CARES Campaign Field Updates

Published: 17 February 2014

Meet Rahul Zaveri – CARES Lead Scientist

Rahul Zaveri is the lead scientist for the CARES—Carbonaceous Aerosols and Radiative Effects Study—campaign taking place June 2-28, 2010, in the central California region to the northeast of Sacramento. This field campaign is designed to increase scientific knowledge about evolution of black carbon and secondary organic aerosols from both urban/manmade and biogenic sources. He’ll be sharing his experiences with you through this travelogue, as well as PNNL’s Facebook page.

Rahul is a chemical engineer whose career has involved a wide range of research experience including assessment of transport, transformation, and fate of energy-related emissions. His expertise is in developing and applying multiphase gas-aerosol-cloud chemistry models in the analysis of field and laboratory measurements to solve complex atmospheric chemistry problems. »» Learn More

Dear CARES Participants and Interested Colleagues

We are pleased to report again at the successful completion of the field portion of the CARES campaign. The field study began on June 2 and the last sampling day was June 28. The DOE G-1 aircraft flew 67.4 hours over 21 research flights. The NASA B-200 flew in coordination with the G-1 as well as sampled areas outside of the G-1’s primary domain. The NOAA Twin Otter shifted its operation to Sacramento from June 15 through 28 to collaborate with CARES. I have attached a few slides of some pictures of the T0 and T1 ground sites, various aircraft, and participants; summary of the daily flights and other campaign activities; and links to outreach information and news media stories.

Thanks again to our hosts at McClellan Jet Services and American River College in Sacramento and Northside School in Cool, CA. And thanks to all the participants and support staff for their hard work and a great display of team spirit throughout the campaign.

We now look forward to working closely with all the CARES participants and other collaborators in analyzing the rich dataset and disseminating the results through conferences and peer-reviewed literature.

Best wishes,
Rahul Zaveri, Will Shaw, and Dan Cziczo

Wednesday, June 30, 2010

Today, Rahul Zaveri returns to Pacific Northwest National Laboratory in Richland, Washington, to begin the task of evaluating and analyzing the aerosol data collected in the CARES campaign.

Thank you to all the people who visited Rahul’s travelogue throughout June.

Monday, June 28, 2010

We had the highest ozone and aerosol concentrations of the entire study on the last day! The high concentrations were the result of stagnating air over Sacramento in the morning coupled with hot temperatures and sunny skies. We carried out two G-1 and B-200 coordinated flights to sample the concentrated Sacramento plume in the morning and again in the afternoon as it slowly moved eastward. The NOAA Twin Otter also flew in the plume between 10:30 AM and 2:00 PM. The two ground sites also collected valuable data in the plume over the course of the day.

It’s been a hectic month here in Sacramento, to say the least. I’d like to thank the entire CARES science team, aircraft crew, and the support staff for their hard work and professionalism as we went through the ups and downs of the campaign. Special thanks are also due to all the family members and who were away from their loved ones for up to 5 weeks straight during the field activities.

As I write this last blog entry tonight, I am reminded of Henry Ford’s quote on teamwork:

“Coming together is a beginning.
Keeping together is progress.
Working together is success.”

The CARES team came together, kept together, and worked together the past 4 weeks, but the job is not done yet. The end of the field portion of the CARES study marks the beginning of the long journey ahead that entails analyzing the data, presenting new findings at conferences, and publishing the results in peer-reviewed scientific journals. I look forward to working with the team over the coming months and years as we analyze the data and bear the fruits of the study.

Thanks to Kathryn Lang, Christine Novak, and Patricia Mosley at PNNL for managing the CARES blog site. I truly enjoyed writing about the daily field activities, participants’ roles, their instruments, and the scientific issues related to the effects of air pollution on climate change. Thanks very much for reading!

Until the next adventure . . .


Sunday, June 27, 2010

While I don’t have the actual numbers, I believe we have collected a few terabytes of data over the last 4 weeks. Each instrument’s principal investigator will check the quality of their data in the coming weeks, apply calibration corrections where necessary, and prepare preliminary datasets for further analysis. This is a painstakingly slow process. More comprehensive data analyses will begin once the final datasets are prepared and shared with all the participants of the study. One of the main objectives of the CARES study is to use the field data to evaluate, improve, and validate mathematical representations of aerosol processes and properties used in computer climate simulation models. The collection of computer codes (programs) that describes the various aerosol processes and properties is referred to as an “aerosol module.”

Over the past 12 years at PNNL, I have led the development of a comprehensive aerosol module called “MOSAIC” (Model for Simulating Aerosol Interactions and Chemistry). MOSAIC was recently implemented in the next-generation Weather Research and Forecasting (WRF) model to simulate aerosol formation, transport, and the associated direct and indirect radiative effects at regional scales.

As part of CARES data analyses, we will evaluate and improve representations of carbonaceous aerosols in MOSAIC, including secondary organic aerosol formation, new particle formation and growth, black carbon aging, and the related optical properties, and cloud condensation nuclei activation properties.

The ultimate goal is to produce a reduced and more efficient version of MOSAIC that is well evaluated using field and laboratory measurements under a variety of conditions for use in global climate models.

Tomorrow is the last day of the study. It’s going to be another hot and sunny day, with highs in the mid 90s. The forecast calls for stagnating conditions over Sacramento in the morning, with the urban plume slowly moving to the east by late afternoon. We are scheduled to carry our last two flights, and the plan is to sample the freshly emitted aerosols in the Sacramento plume in the morning and aged aerosols in the same plume in the afternoon one last time.

Saturday, June 26, 2010

We are nearing the end of the CARES field study, with just two more days to go. Everybody is quite anxious to go home after having spent nearly 5 weeks here. At the same time, everybody is excited about the data we have collected in this study. We had our third and final science meeting today to review the data and discuss preliminary findings from the different instruments at the two ground sites and on the aircraft. Overall, we have collected a very rich and unique dataset, which should provide new insights into the evolution of different types of carbonaceous aerosols and their climate-affecting properties.

I’d like to take this opportunity to highlight the remaining instruments we have deployed in CARES. Dr. Will Shaw, Mr. Danny Nelson, Dr. Larry Berg, and Dr. Mikhail Pekour of PNNL have set up weather stations at both the ground sites

and special radars at the Cool site that measure wind speed and direction at different altitudes. They also have been launching radiosonde weather balloons(Offsite link)—5 on days we have aircraft flights and 1 on the remaining days—to measure vertical profiles of temperature, pressure, and relative humidity. These meteorological measurements will be very useful in characterizing the vertical structure of the atmospheric boundary layer and in figuring out the transport of aerosols from different source regions to our sampling locations on the ground and in the air aloft.

The other set of instruments are specialized particle samplers, which essentially collect aerosol particles on disks or filters for detailed analyses to be carried out later with a number of sophisticated laboratory techniques. Dr. Alex Laskin of the Environmental Molecular Sciences Laboratory (EMSL), a DOE national scientific user facility at PNNL, has deployed his “Time Resolved Aerosol Collectors” (TRAC) at the two ground sites and onboard the G-1 aircraft. Alex’s collaborators Dr. Ryan Moffet and Dr. Mary Gilles(Offsite link) of Lawrence Berkeley National Laboratory(Offsite link) (LBNL) are operating these devices in the field, and they will together analyze the collected aerosols using various microscopic and spectromicroscopic techniques at EMSL and LBNL.

Dr. Claudio Mazzoleni(Offsite link), Assistant Professor, Michigan Tech(Offsite link), and his student Kyle Gorkowski have deployed particle collectors for analysis using a Scanning Electron Microscope(Offsite link) to determine the shape and morphology of different types of carbonaceous aerosols.

Dr. Jeff Gaffney(Offsite link), Professor, University of Arkansas, and his students Angie Marchany and Mahbuba Begum have deployed high-volume samplers that collect aerosol particles on filters. They plan to perform radiocarbon dating analysis on their aerosol samples to distinguish between carbonaceous aerosols from fossil fuel combustion (i.e., old carbon) and from biogenic hydrocarbons emitted from trees (i.e., new carbon).

Dr. Alena Kubatova(Offsite link), Associate Professor, University of North Dakota(Offsite link), and her postdoctoral research associate Dr. Haewoo Jeong(Offsite link) have also deployed a high-volume sampler at each ground site. They are collecting aerosol particles, which they will analyze to determine the polar and non-polar organic compounds using organic solvent extraction and GC/MS techniques.

Friday, June 25, 2010

After carrying out two back-to-back flights, two days in a row, today was declared a hard down day so aircraft crew can relax and rejuvenate. I took this opportunity to visit the Cool ground site and join Berk Knighton and his student Cody Floerchinger on a short hike along the American Canyon Creek Falls trail. It was a hot and sunny day, but I really enjoyed the hike as the trail was well shaded.

Both Berk and Cody have spotted rattlesnakes in this area several times, and Mikhail Pekour found one right next to the trailers at the Cool site. I was really hoping to see one today. As luck would have it, I didn’t see any snakes, but spotted other interesting wildlife, a big frog, a couple of lizards, and several lesser goldfinches and turkey vultures. The highlight was a nice little waterfall and a natural swimming pond at the end of the trail.

Tomorrow is going to be a soft down day, which means the aircraft instrument operators will have access to the aircraft and power so they can calibrate their instruments and perform the necessary maintenance. I have taken this opportunity to have another science meeting to review the data we have collected so far. This will be the last time we will all meet to discuss the data while we are all still here.

Thursday, June 24, 2010

We did two flights yesterday to sample the Sacramento plume as it was transported to the northeast over the course of the day.

Today was another long day with two more back-to-back flights. The morning flight was carried out close to the Carquinez Strait to sample the inflow of aerosols and their precursors from oil refineries along the river and the wider Bay Area emission sources into the Central Valley. The afternoon flight was carried out over Sacramento and to the northeast to again sample the flow of “aged” aerosols and their climate-affecting properties.

In the previous blog entry I had described some of the key instruments that have been deployed in CARES to measure the light scattering and absorption properties of aerosols. Scattering of light by aerosols causes a cooling effect on the atmosphere while absorption of light by certain types of carbonaceous aerosols (black carbon or soot) causes a warming effect on the atmosphere. These are referred to as “direct radiative effects” on climate, because in these processes the aerosols directly affect the amount of sunlight that reaches the surface of the earth and the amount that is reflected back to space.

Under very humid conditions, the available water vapor in the air can condense upon aerosol particles, some of which then grow into relatively bigger cloud droplets of average diameter of 0.02 millimeters (i.e., 100 times bigger than aerosol particles). The process of cloud formation is quite complex and depends greatly on the size of the aerosol particles, the hygroscopicity (solubility) of the chemicals that are present in the particles, and the relative humidity. The bigger and more hygroscopic (i.e., more soluble) the aerosol particles, the more efficient they are in forming cloud droplets. Since cloud droplets are more efficient in scattering sunlight than aerosol particles, this phenomenon is referred to as the “indirect radiative effect” of aerosols on climate.

We have deployed special instruments called “Cloud Condensation Nucleation (CCN) Counters” in CARES that measure the concentrations of aerosol particles that can become cloud droplets under specified humidity conditions. Post-doctoral research associates Dr. Manish Shrivastava and Dr. Naruki Hiranuma of Pacific Northwest National Laboratory are operating these instruments at the American River College and the Cool ground sites, respectively. Manish is also operating another instrument called the “OC-EC Analyzer” from Sunset Laboratory, Inc. at the American River College, while Dr. Nels Laulainen of PNNL is operating another OC-EC unit along with several other instruments at the Cool site. The OC-EC instrument measures the concentrations of organic carbon (OC) and elemental carbon (EC) components of carbonaceous aerosols.

Dr. Jim Barnard of PNNL has deployed an instrument called Multifilter Rotating Shadowband Radiometer (MFRSR) at both the ground sites to measure different types of incoming solar irradiances at multiple wavelengths.

Dr. Jeff Gaffney, Professor, University of Arkansas, has deployed an Ultraviolet MFRSR unit as well at the Cool site.

Wednesday, June 23, 2010

Today we observed the highest ozone levels—nearly 90 parts per billion—in this area since the campaign started. Ground-level ozone is one of the many air pollutants that are regulated by the Environmental Protection Agency (EPA) in the US. Breathing air containing ozone can decrease lung function, aggravate asthma symptoms, or cause other respiratory illnesses. Exposure to high levels of ozone may also contribute to premature death, especially in people with heart and lung disease, and it can harm sensitive vegetation and ecosystems as well. The current 8-hour average National Ambient Air Quality Standard (NAAQS) for ground-level ozone is 75 parts per billion.

Ozone is not emitted directly into the air. It is formed by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOCs.

The chemical reactions that form ozone are also directly or indirectly responsible for forming secondary aerosols such as sulfate, nitrate, and a variety of organic compounds. When breathed in, these small aerosol particles can reach into the deepest regions of the lungs and further aggravate asthma and respiratory conditions. Aerosol particles are therefore also regulated by the EPA, and the current 24-hour average standard for particles smaller than 2.5 microns in diameter is 35 micrograms per cubic meter.

These aerosol particles are also the main cause of haze and visibility degradation, and they play a significant role in climate modification due to increased scattering and/or absorption of sunlight. Increased concentrations of aerosol particles can also modify cloud properties and affect rainfall patterns in a highly polluted region. We have deployed a number of instruments in CARES that measure the optical (light scattering and absorption) and cloud formation properties of aerosols.

Dr. Patrick Arnott, Associate Professor, University of Nevada, Reno, and his graduate student Madhu Gyawali, along with Dr. Manvendra Dubey of Los Alamos National Laboratory and his post-doctoral research associate Dr. Brad Flowers have deployed instruments called the Photo-Acoustic Soot Spectrometer at the ground sites and onboard the G-1 aircraft to measure scattering and absorption of light by black carbon present in vehicle exhaust or biomass burning.

Dr. Dean Atkinson, Associate Professor, Portland State University, and his graduate student Jimmy Radney have deployed another instrument called the Cavity Ring-Down (CRD) spectrometer that also measures the optical properties of aerosols by a different technique. Dr. Chris Cappa, Assistant Professor at University of California, Davis, and his graduate student Kati Kolesar have also deployed a CRD instrument at the American River College site.

Dr. Mikhail Pekour and Dr. Larry Berg of Pacific Northwest National Laboratory have deployed yet another set of instruments called the Particle Soot Absorption Photometer (PSAP) and nephelometer, which measure light absorption and scattering, respectively. It is important to measure these critical climate-affecting aerosol properties by different techniques to increase our confidence in our results.

Monday, June 21, 2010

Yesterday (Sunday, June 20) was a hard down day for the aircraft folks, which means the pilots, support crew, and instrument scientists get the day off. They are not supposed to show up for work at all. I took that opportunity to have another science meeting to review and discuss the data collected so far.

The instruments I’d like to highlight today are the trace gas analyzers of Dr. Stephen Springston, Brookhaven National Laboratory (BNL). Stephen has more than 20 years of experience measuring trace pollutant gases, including oxides of nitrogen, ozone, sulfur dioxide, and carbon monoxide onboard the G-1 aircraft.
Nitric oxide, nitrogen dioxide, and carbon monoxide are formed from various combustion processes, and they are typically present in vehicle exhaust and power plant emissions. Sulfur dioxide is usually present in coal-fired power plant plumes and certain industrial emissions. In contrast, ozone is a “secondary” chemical, meaning it is formed in the atmosphere in the presence of sunlight, nitrogen oxides, and reactive organic gases.
Stephen’s colleague Dr. Art Sedlacek of BNL has deployed a relatively new instrument called the Single Particle Soot Photometer (SP2), which measures black carbon particles that are also invariably present in vehicle exhaust as well as biomass burning (e.g., forest fires, agricultural burning) emissions.
The SP2 estimates black carbon mass in individual particles by heating them with a laser and measuring the intensity of the incandescence light at the color temperature specific to black carbon. The SP2 instrument is commercially available from Droplet Measurement Technologies (DMT), and Dr. Subramanian of DMT is also participating in CARES, operating an SP2 instrument at each ground site. Depending on the level of pollution, this instrument can produce up to 100 GB data per day!

Dr. Gunnar Senum of BNL, who’s an expert in measuring aerosol and cloud droplet size distributions, recently joined us to relieve Stephen, and he will take turns with Art to operate several instruments on the G-1.

Dr. Jian Wang of BNL is also an expert in measuring aerosol size distributions. He has invented a new instrument called the Fast Integrated Mobility Spectrometer (FIMS) that measures the size distribution of aerosol particles between 30 and 100 nanometers every second. That’s pretty fast! We have deployed FIMS on the G-1 for the CARES project to measure the size distributions of these very small particles at unprecedented speed and accuracy so that we can see how fast they grow due to “aging.” Jian’s post-doctoral research associate Dr. Chongai Kuang of BNL arrived here yesterday to assist with the FIMS measurements.

John Hubbe of PNNL is the aircraft “Payload Master,” who is responsible for the overall layout of the payload, power supply, and operation of several instruments during flights.

Lastly, I’d like to thank Dr. Larry Kleinman of BNL for diligently going through all the data from various instruments to make sure they make sense. Larry’s experience and mentorship has been absolutely invaluable!

More instruments and scientists tomorrow . . .

Saturday, June 19, 2010

We were scheduled to carry out two flights today, but some trouble with the power generator on the G-1 aircraft forced us to scrub the morning flight. Mechanic Gene Dukes quickly fixed the generator, and the aircraft was ready to fly again by noon.

AAF Technical Director Dr. Beat Schmid went back home a couple of days ago, and Deputy Technical Director Dr. Jennifer Comstock is here in his place. AAF Operations Lead Jason Tomlinson also went back home, and deserves a much needed break from the non-stop work the past several weeks. Thanks to both Beat and Jason for their hard work, and a warm welcome to Jennifer! We are now exactly two-thirds of the way through the study, with nine more days to go. There’s still a lot of flying to be done and more data to be collected before we can all go home.

The data collected so far has shown some interesting results already. As I have mentioned earlier, one of the research issues we would like to address in CARES is the effect of different types of carbonaceous particles and their evolving compositions on their climate-affecting properties. Highly specialized instruments called “single-particle mass spectrometers” are needed to characterize and distinguish between different types of particles, from different sources, with different compositions and properties. We have deployed three such state-of-the-art single particle instruments in CARES.

The one deployed on the G-1 aircraft is called the “Aerosol Time-of-Flight Mass Spectrometer” or ATOFMS, which was developed under the leadership of Professor Kimberly Prather, University of California, San Diego. Dr. Prather’s graduate students Kaitlyn Suski and Jack Cahill are operating the newest ATOFMS called “Shirley,” who is smaller and faster than the previous generation. The single particle instrument deployed at the American River College site is called the “Single Particle Laser Ablation Time-of-flight Mass Spectrometer” or SPLAT II, which was developed by Dr. Alla Zelenyuk of PNNL. The SPLAT II belongs to the Environmental Molecular Sciences Laboratory, a national scientific user facility at PNNL. Dr. Zelenyuk’s post-doctoral fellows Dr. Josef Beranek and Dr. Tim Vaden are operating the SPLAT II during CARES. The third instrument deployed at the Cool site is called the “Particle Analysis by Laser Mass Spectrometry” or PALMS, which is being operated by Dr. Dan Cziczo of PNNL.

Friday, June 18, 2010

One can never have enough aircraft and instruments! The NOAA Twin Otter, which is carrying out its missions as part of the CalNex field campaign, arrived at McClellan Airport on June 15, and will be collaborating with us until June 28. I like the Twin Otter. In a previous field study, a few years ago in Houston, TX, I had the pleasure of flying onboard another Twin Otter as the mission scientist. It’s a highly maneuverable, versatile aircraft that can be flown at slow speeds, quite appropriate for carrying out air pollution sampling missions. The NOAA Twin Otter missions for CalNex are being led by Dr. Mike Hardesty, Dr. Christoph Senff, and Dr. Robert Banta of NOAA and Dr. Rainer Volkamer, Assistant Professor, University of Colorado, Boulder. Much like the NASA B-200, the NOAA Twin Otter carries several remote sensing instruments, including the downward looking ozone/aerosol and Doppler wind Lidars and an AMAX-DOAS system to measure various trace gases, aerosols, and wind profiles below the aircraft.
Now, whenever we have more than one aircraft carrying similar payloads, it is customary to carry out coordinated flight patterns to allow intercomparison of measurements from instruments on different aircraft. Such maneuvers need careful planning between the principal investigators and precise coordination between the pilots of all the aircraft involved in the intercomparison exercise. The proposed flight plan must meet all the safety requirements and must be approved by the Federal Aviation Administration (FAA).

Today we carried out such an intercomparison exercise between four aircraft—DOE G-1, NOAA WP-3, NOAA Twin Otter, and NASA B-200. The flight plan involved the DOE G-1 trailing behind the NOAA WP-3 by about 6 nautical miles at a speed of 190 nautical miles per hour at 1500 ft altitude, with the NASA B-200 and NOAA Twin Otter flying right above at 28000 and 6500 ft altitudes, respectively. As shown in the pictures, the G-1 (yellow trace) arrived at the agreed upon rendezvous point “34” near Fresno, CA, by 4:26 pm, and circled over it for about 35 minutes until the WP-3 (white trace) arrived there at 5:00 pm. The two aircraft then lined up as planned and flew close to each other to Bakersfield, sampling roughly the same air along the way. This strategy will allow us to compare the performance of instruments onboard the two aircraft, and thereby increase the confidence in our measurements. The NASA B-200 and NOAA Twin Otter flew over the same path at higher altitudes, so that their remote sensing instruments can provide the vertical context for the G-1 and WP-3 measurements.

Needless to say it was a pretty exciting day!

Thursday, June 17, 2010

As I have mentioned earlier, the DOE G-1 aircraft typically flies around 1000-3000 ft above ground level, and samples aerosols within the boundary layer, as close as possible to the emission sources on the ground. We also frequently sample at increasing altitudes, up to 8000 ft, to characterize the vertical distribution of aerosols. This sampling strategy provides valuable data on aerosol size, composition, and its climate-affecting properties along horizontal and vertical lines, i.e., the path of the aircraft flight in the atmosphere.

To complement the in situ data obtained onboard the G-1, we are deploying the NASA B-200 King Air aircraft that typically flies at 28,000 ft, and carries specialized instruments capable of remotely sensing the scattering properties and shape of aerosols below it all the way to the ground.

The B-200 team is led by Dr. Richard Ferrare and Dr. Chris Hostetler of NASA’s Langley Research Center. Their instrument, the High Spectral Resolution Lidar (HSRL), is installed in the belly of the aircraft, and it “looks” down to remotely sense the vertical distribution of aerosols as it flies around at 28,000 ft, often in sync with the G-1 flying the same pattern at 1000 ft. The results look like pretty “curtains” of color-coded properties of aerosols as shown in the picture.

The B-200 is also equipped with the Research Scanning Polarimeter (RSP), which provides an estimate of the optical properties of aerosols in the columns of air below the aircraft. The principal investigator of the RSP instrument is Dr. Brian Cairns at NASA’s Goddard Institute of Space Studies.

It’s been a pleasure to work with Rich Ferrare the past couple of weeks. He went back today as Chris Hostetler and Mike Obland replaced him. I also had the pleasure of making two new friends from NASA—Ray Rogers and Matteo Ottaviani, who gave me a nice tour of the B-200 aircraft the other day. Check out Matteo’s blog: Who CARES? to see some stunning photos and videos and more information on NASA’s participation in CARES.

Wednesday, June 16, 2010

The morning and afternoon flights yesterday, June 15, were quite successful. All instruments worked without any issues, the temperature inside the G-1 aircraft cabin remained comfortable throughout the flight, and the meteorological conditions were nearly ideal. The Sacramento plume was clearly “visible” from the measurements by different instruments onboard the G-1.

One of the key instruments used in characterizing the composition of aerosol particles is the Aerosol Mass Spectrometer (AMS) of Aerodyne Research, Inc. We have deployed three AMS units in CARES. The one on the G-1 aircraft belongs to the Environmental Molecular Sciences Laboratory (EMSL), a DOE national scientific user facility at PNNL. It is maintained by Dr. Liz Alexander and is being operated by Dr. John Shilling of PNNL for the CARES campaign.

The AMS unit deployed at the American River College site belongs to PNNL, and is being operated by Dr. Dr. Chen Song. Dr. Qi Zhang, Assistant Professor, UC Davis, and her post-doctoral research associate Ari Setyan are running another AMS unit at the Cool site. Special thanks are due to Drs. John Jayne, Ed Fortner, Tim Onasch, and Doug Worsnop of Aerodyne Research, Inc., for their efforts to ensure smooth operation of the AMS units during CARES.

The AMS measures the average composition of particles within certain size ranges, as well as the average composition of all the particles between about 60 and 600 nanometer diameters.

In addition to the AMS, we have also deployed a bulk aerosol composition measurement at each ground site and onboard the G-1 aircraft using the Particle-In-Liquid Sampler (PILS) system of Brechtel Manufacturing, Inc (BMI). Before the campaign began, Fred J. Brechtel of BMI trained Dan Cziczo, Mikhail Pekour, Chen Song, Danny Nelson, and Celine Kluzek of PNNL to operate the PILS system. It collects aerosol particles in the form of aqueous solution in small vials at pre-programmed time intervals – every hour at the ground sites and every three minutes on the G-1 aircraft. These samples are being analyzed by Qi Zhang’s post-doctoral research associate, Dr. Yele Sun at UC Davis.

Fred Brechtel has also designed and manufactured a specialized a aerosol inlet system that carefully draws the ambient aerosols into the aircraft as it is moving at 100 meters per second.

Monday, June 14, 2010

Today it was distinctly hazier than it has been since we started the study. Hazy sky means more aerosol particles in the air. This is good news for us!

We are exactly half way through the study, and so far it has been pretty clean up here. We were therefore excited to see some hazy conditions develop in this area, especially to the west as shown in the “before” and “after” pictures I took from McClellan Airport. The G-1 aircraft flew close to the Bay Area to sample air pollution coming into the Central Valley and towards Sacramento. Art Sedlacek of Brookhaven National Laboratory took an aerial shot of a power plant along the Carquinez Strait. Hopefully, the hazy conditions around Sacramento will last for the rest of the study so we can contrast the observations from the first half with the second.

At the beginning of the campaign I had promised to introduce different research groups and their instruments that are part of the CARES study. I will start today with Dr. Tom Jobson, Associate Professor, and his graduate students Mike Erickson and Will Wallace from Washington State University, Pullman, WA.

Tom’s group is deploying their Mobile Atmospheric Chemistry Laboratory (MACL) trailer, which houses a suite of instruments for field research on atmospheric aerosols. For the CARES project, they have configured the trailer to measure a variety of gaseous pollutants that are directly or indirectly responsible for secondary aerosol formation. These gases include nitrogen oxides (NOx), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), and a variety of volatile and semi-volatile organic gases that are emitted from vehicle exhaust as well as trees. The instruments that measure the organic gases include the Proton Transfer Reaction Mass Spectrometer (PTR-MS) (PTR-MS) and the Gas Chromatography-Ion Trap Mass Spectrometer (GC-ITMS). The WSU trailer is part of the extensive suite of instruments at the American River College site.

Dr. Berk Knighton, Associate Research Professor, and his student Cody Floerchinger from Montana State University are also measuring organic trace gases with another PTR-MS instrument at the Cool site. Dr. Scott Herndon of Aerodyne Research, Inc., is also here to oversee the operation while Berk had to go back for a few days.

Particular emphasis is given to the measurement of volatile and semi-volatile organic gases, which upon oxidation form secondary organic aerosols. Measurement of aerosol composition at many places around the world has shown that organic compounds typically constitute between 20 and 90% of the total mass for aerosol particles smaller than 2.5 microns in diameter. However, significant uncertainties and knowledge gaps still exist in our ability to simulate the formation and evolution organic aerosols in a climate model.

As part of the CARES field campaign, we are trying to learn more about organic aerosol formation and their climate-affecting properties by measuring how organic gases and aerosols evolve in the Sacramento and Bay Area urban plumes as well as in the surrounding forested regions.

Sunday, June 13, 2010

On Friday, June 11, we had our first science meeting to review the data collected so far. Most of the participants attended the meeting while a few spent the day calibrating or fixing their instruments so that they were ready for the next day’s aircraft missions. The meeting started at 3:00 PM and went on for 3 hours. This was the first time the aircraft and ground sites folks met each other since the campaign began, so everybody was eager to show their measurements as well as curious to see what others had observed so far. The goal was to make some sense of all the different measurements made at two ground sites and from two aircraft. The intense discussions often continue after hours over dinner.

The main story that is emerging so far is that the background air in the Central Valley surrounding the Sacramento area has been unusually clean since the campaign began June 2. However, there is evidence of enhanced concentrations of ultrafine aerosols, between 3 and 10 nanometers in diameter, in the Sacramento urban plume, and on some days the ultrafine aerosols are also observed in air outside the urban plume.

These findings were confirmed again on Saturday, June 12, when we conducted two aircraft missions south of Sacramento, in San Joaquin Valley. Along with the enhanced concentrations of ultrafine particles, we also see relatively larger, but still quite small, black carbon particles inside the Sacramento plume. Black carbon particles can absorb sunlight and therefore tend to warm the atmosphere. Also, their absorption efficiency increases when they get coated with other non-absorbing substances present in the urban plume or from natural sources. As part of the CARES objectives, we will investigate these mechanisms once all the data are collected and analyzed.

Today was the hottest day here since the campaign began. It reached 100° F (38° C) by 4 PM. It was not a problem because we weren’t flying today. Tomorrow is going to be equally hot, so we will try to do only one flight in the morning and then get the aircraft back in the hangar before the mercury climbs high in the afternoon.

Thursday, June 10, 2010

The last two days have been pretty hectic. According to Jerome Fast’s weather briefing, June 7, the wind pattern on June 8 was expected to transport the Sacramento urban plume to the northeast by late afternoon. This is the type of flow pattern we were waiting for.

We conducted two flights that day: one in the morning from 9:00 AM – noon and another in the afternoon from 3:30 PM – 6:30 PM. The morning flight was designed to sample the freshly emitted pollutants over the Sacramento urban area, while the afternoon flight was designed to sample the aged pollution over the Cool site.

Hot and sunny days during summer in Sacramento area are conducive to the upslope mountain flows we are interested in, but high temperatures are also of great concern inside the aircraft. Many instruments (and their operators) onboard the G-1 will show signs of trouble when the cabin temperature increases above 100° F (38° C). The AAF crew installed an air conditioner, rigged up some ducting, and took several other measures to keep the aircraft cool.

Unfortunately, the compressor itself failed after the first flight on June 8. Still, the crew decided to go for the afternoon flight since the ambient temperature was cooler than the previous day. The cabin temperature remained under control for the most part of the flight. Some instruments had to be shut off toward the end to prevent any potential damage.

June 9 was declared a down day, so the crew could replace the compressor and fix a few other things before the really hot days arrive next week.

The air conditioner was up and running again this morning, and we did a flight in the afternoon.

Tomorrow we will have our first science meeting to review the data collected by different instruments at both the ground sites and onboard the two aircraft over the past week.

Monday, June 7, 2010

Folks working at the Cool site, up in the foothills of the Sierra Nevada Mountains, have the pleasure of driving back and forth everyday on the scenic Route 49 between Auburn and Cool in the El Dorado County – the home of the world-shaking Gold Rush of 1849.

I visited the Cool site today to check on a few things, and stopped on the way to appreciate the natural beauty of the area. The 7 mile long winding road cuts the Middle Fork of the American River, which originates in the high Sierra Nevada just west of Lake Tahoe, in the Tahoe and El Dorado National Forests. An added attraction along this route is the view of the Foresthill Bridge, which is the tallest bridge in California, and the 3rd tallest bridge of its kind in the United States. There is a tremendous diversity of flora and fauna in this region as well. We have spotted a few birds and insects at the site, and Berk Knighton’s graduate student, Cody Floerchinger of Montana State University, has seen snakes in the area several times already. I am hoping to see at least one in the coming days if I am lucky.

The mixed-evergreen coniferous forests in the Sierra Nevada Mountains are also a rich source of volatile organic compounds such as isoprene, methyl butenol, and monoterpenes. These compounds are emitted from tree leaves as part of natural processes, and their emission rate increases when it is hot and sunny. Once in the air, these compounds can get oxidized by reacting with ozone and other oxidants formed in the presence of sunlight to form low volatility compounds, which can either nucleate to form very small (ultrafine) organic particles or condense upon pre-existing particles.

Since these particles are formed from oxidation of organic gases, they are called secondary organic aerosols (SOA), as opposed to primary organic aerosols (POA), which are directly emitted from vehicle exhaust or meat cooking. As part of the CARES field study, we are interested in learning more about how the Sacramento urban air pollution interacts with natural emissions of organic gases, and thereby affects the natural processes of secondary organic aerosol formation in forested areas as well as in the urban plume.

Sunday, June 6, 2010

The day started very early for the aircraft teams and the weather balloon launch teams at both the ground sites. The aircraft ground support crew and the instrument PIs have to start preparing the aircraft and the instruments at least 3 hours before takeoff. On a flight day, five weather balloons are launched, one every three hours, starting at 7 AM. The NASA B-200 took off at 9:00 AM while the DOE G-1 took off at 10:40 AM. Both aircraft landed after sampling over the urban area for about 3 hours. The G-1 crew grabbed a quick bite, refueled, and jumped back on the plane for another takeoff at 3:30 PM.

Thanks to Jason Tomlinson, we are now able to download selected data from the G-1 in real time so that folks on the ground can look at what was being measured by the G-1 while it is in flight.

A quick look at the morning flight’s data confirmed what we have been seeing at both the ground sites the past few days—very clean air, except for a huge concentration of very small particles (between 3 and 12 nanometers) within and outside the Sacramento urban area. NASA B-200’s data also support this finding on a slightly larger scale. While a careful analysis of all the data is needed to understand the source(s) of these particles, the working hypothesis is that these ultrafine particles are formed from nucleation of sulfuric acid vapors, which grow bigger by condensation of organic vapors from natural sources (trees and other vegetation).

In the afternoon flight, the concentrations of these very small particles were 2-3 times lower compared to the morning flight. This can occur due to a number of processes, such as coagulation (i.e., two or more particles colliding and sticking with each other), condensational growth (i.e., additional vapors glomming onto them), and dilution as the turbulent boundary layer grows deeper in the afternoon. The boundary layer is the turbulent layer of air close to the ground, where air pollutants mix up during the day. It starts out very shallow (less than 100 meters) early in the morning and can grow 1 to 2 km high (or even higher) throughout the day as the sun heats up the ground and produces air thermals.

High afternoon temperatures can also cause the aircraft cabin to heat up a little bit too much, which can cause many instruments to malfunction. We had a bit of this issue today as the afternoon temperature on the ground reached about 90° F (32° C). We have decided to address the heat issues tomorrow and be prepared for even warmer weather in the coming days.

Saturday, June 5, 2010

The CARES media event yesterday went quite well, thanks to the meticulous preparations by PNNL’s Mary Beckman, Media Relations, and Lynne Roeder, Communications Specialist, and the rest of the outreach team—Kathryn Lang, Kimberly Tebrugge, and Dana Dupont for their help in planning the event. It started at the American River College site at 11 am and continued on to the McClellan Airport until about 2 pm. A number of reporters from various news media interviewed several of the CARES team members and took tours to view the instrumented trailers and the G-1 aircraft.

I would like to thank our invited guests Dr. Bart Croes, Division Chief of California Air Resources Board (CARB) and Dr. Eileen McCauley, Manager of the Atmospheric Processes Research Section, for attending the event and for their valuable assistance during the planning of CARES. A couple of interested chemistry professors from American River College and the Assistant Dean of Science and Engineering, Dr. Derrick Booth, also graced the occasion.

The reporters seemed to be quite enthusiastic about our work. They asked a lot of questions of about the scientific objectives of the CARES field study, data collection methods and instrumentation, and what all of this means to the general public—why should they care about CARES? Check out the article in the Sacramento Bee newspaper and Fox 40 Sacramento News video—I think they did a pretty good job in getting the main points across.

The aircraft team was busy preparing the instruments today in anticipation for a couple of flights tomorrow. The weather forecast calls for a warm day and the wind pattern looks favorable for the transport of the Sacramento urban plume to the west or northwest. It’s going to be a long day.

Thursday, June 3, 2010

It was an interesting day at the airport. The aircraft crew resolved the issue with the ground power, and the G-1 was up and ready to fly in the morning.

Now, as I had explained on May 31, the unique summertime meteorology in Sacramento area was the primary reason for selecting this site for CARES. The other motivation was the opportunity to collaborate with the CalNex field study that is also taking place presently in California. As part of CalNex, the National Oceanic & Atmospheric Administration (NOAA) is deploying their WP-3 and Twin Otter Remote Sensing aircraft and the R/V Atlantis ship to make measurements of air pollutants and their climate-affecting properties in and around California. We plan to coordinate our sampling with them as opportunities arise.

In fact, an opportunity to coordinate the G-1 flight with R/V Atlantis arose today. I had been in touch with the ship’s principal investigator, Patricia Quinn of NOAA’s Pacific Marine Environmental Laboratory, the last few days regarding this possible coordination as the ship was working its way up the California coast from Los Angeles to Sacramento. I learned yesterday that the ship will be moving up the Sacramento River today and be in our sampling domain by 1:00 PM.

So, after the weather briefing at 9:15 AM, we all swung into action to develop a flight plan in which the G-1 would fly vertical spirals over the ship at a few different altitudes between 1000 and 5000 feet. The NASA B-200 would also fly over the G-1 at 28,000 feet, as well as perform additional maneuvers to scope the larger domain with their remote sensing instruments. Both aircraft took off around 12:30 PM and completed their missions without a hitch. The G-1 was able to meet up with the ship between 13:13 and 14:04 do vertical profiles over it as planned. John Hubbe managed to take a nice picture of the ship.

A debriefing was held at 4 PM, where the pilots, flight engineers, and instrument principal investigators reported how everything performed. Some minor problems with a couple of instruments were discovered, but the overall mission was deemed quite successful!

Tomorrow is the CARES media day, where reporters will visit the American River College site and the airport to see what we are up to. Read the press release here.

Wednesday, June 2, 2010

Today marks the official start of the CARES field campaign. As planned, several state-of-the-art instruments at both the ground sites began making measurements of aerosol size, concentration, composition and their climate-affecting properties. A number of instruments that measure concentrations of pollutant gases such as ozone, carbon monoxide, sulfur dioxide, nitrogen oxides, and selected organic compounds emitted from vehicle exhaust and vegetation also kicked into action. However, most of these instruments hardly “saw” any signs of pollution. It was a gorgeous day outside, and the air appeared to be exceptionally clean. This was quite disappointing, at least initially. As the day progressed, we saw massive amounts of very small particles appear at both the ground sites.

While it will take several weeks or months to analyze all the data from just this one day and figure out the source(s) and evolution of these particles, our guess is that they may have formed via oxidation of natural organic gases emitted from trees. Such new particle formation events, which tend to occur quite efficiently under very clean conditions, are the nature’s way of maintaining a certain concentration of atmospheric aerosols, some of which lead to cloud formation and rain. Such processes are still rather poorly understood and not well represented in computer models that simulate the effects of aerosols on climate. So, the apparently clean and boring day turned out to be quite exciting after all.

Back at the airport we ran into some last-minute glitches with the G-1 aircraft, and decided to postpone the first flight until those issues are resolved. Like I said in the previous blog entry, it always takes a few days to spin up after the aircraft arrives at the field site. This campaign is no exception. The AAF folks are working hard at it, and they expect to get the G-1 up again very soon.

So, we are off to an exciting start, and hope to collect lots of interesting data over the next 4 weeks.

Tuesday, June 1, 2010

I cannot believe it’s already been a week since we started setting up the ground sites. As you can see, a lot has happened here in the last few days. The basic infrastructure—trailer space, power, air conditioning, internet, inlet systems, compressed gases, security—was put in place at both ground sites in less than a week! Kudos to the entire PNNL ground site setup team led by Will Shaw and Dan Cziczo. Will and Dan are also the co-principal investigators of the CARES field study.

All the different research groups have also been hard at work and have pretty much settled down in their spots in the trailers with their “babies,” and most look quite happy. Some remaining minor issues will hopefully be taken care of in the next couple of days.

Tom Jobson of WSU and Dan Cziczo are going to oversee the daily operations at the T0 and T1 sites, respectively. Most of the ground sites folks who are staying in Roseville, a suburb of Sacramento, have been meeting every night at 9 o’clock to give everybody an update on their instrument status, and we plan to continue doing this in the days to come.

The DOE G-1 and NASA B-200 aircraft teams have nearly settled into their offices at McClellan Jet Services, which provides full airport FBO services, 24/7. It’s quite nice, and I was particularly impressed with the size of their hangars. They are huge!

G-1’s new chief pilot, Mike Hubbell, gave the flight safety briefing at 4:00 PM, and the first aircraft science meeting was held at 7:00 PM. We are planning to have our first flight tomorrow afternoon to make sure all the instruments are performing as expected. It always takes a few days to spin up after arriving at the field site.

The study officially begins tomorrow, and everybody’s quite excited and anxious at the same time.

Monday, May 31, 2010

A friend who has been following the blog asked a question the other day: So, why are we doing CARES in Sacramento, CA; why not southern California, or some other city? Great question! The answer is related to the aircraft and ground-based sampling strategy, which I had promised I will describe a couple of days ago.

In the CARES study, we would like to measure the composition and climate-affecting properties of different carbonaceous aerosols just after they are emitted in an urban area. We also want to measure how these parameters and properties change with time.

Aerosol size, composition, and properties change with time due to various processes, which are collectively referred to as “aging.” However, as aerosols “age,” they can be transported from one location to another by wind, which makes it difficult to sample the same aerosols again after they have aged if we were to sample from a fixed location, such as a ground site. But if the prevailing wind direction is known, we could put another ground site at some distance in that direction and sample the aged aerosols when they arrive at the second location after a certain amount of time, depending on the wind speed. This is exactly what we are doing in CARES.

Wind patterns in the Sacramento area in summer are complex, but quite regular. As the ground and Sierra Nevada Mountains heat up during the daytime, the warm air above it rises and is pulled up the mountain slopes as cooler marine air gushes in through the Carquinez Strait, as shown in the diagram.

The direction and speed of wind in the Sacramento area is such that the aerosols emitted during the morning rush hour in the urban area will be transported to the northeast in the foothills area by late afternoon. We have therefore placed a ground site in the Sacramento urban area at American River College and another site in Cool at Northside School. The G-1 aircraft will sample across and along the urban plume in the morning and again in the afternoon to get a more complete picture of the evolution and dispersion of the aerosols from morning to late afternoon.

Jerome Fast of PNNL arrived in Sacramento yesterday and will be serving as CARES meteorologist. He will be providing daily weather briefings and forecasts of Sacramento urban plume transport based on the computer model calculations performed by our colleagues Bill Gustafson and Manish Shrivastava, back at PNNL.

Sunday, May 30, 2010

The Eagle has landed. Pilots Bob Hannigan, Mike Hubbell, Bill Svancara, Dick Hone, and mechanic Gene Dukes brought in the Gulfstream-1 research aircraft (G-1) from Pasco, WA (PNNL is located in nearby Richland.), where it is normally hangared when not in use. During CARES, it will be hangared at McClellan Airport, a former Air Force base. The G-1 is being deployed for CARES by the U.S. DOE’s ARM Aerial Facility (AAF), which is an integral measurement capability of the ARM Climate Research Facility.

Beat Schmid, the technical director of AAF, and his team, John Hubbe, Jason Tomlinson, Jennifer Comstock, and Celine Kluzek, all at PNNL; along with John Shilling of PNNL; Liz Alexander, Matt Newburn, and Alex Laskin of the Environmental Molecular Sciences Laboratory at PNNL; John Jayne of Aerodyne; Stephen Springston, Gunnar Senum, Art Sedlacek, Jian Wang, and Chongai Kuang of Brookhaven National Laboratory; Kimberly Prather and her graduate students Kaitlyn Suski and Jack Cahill of UC San Diego; Manvendra Dubey and Brad Flowers of Los Alamos National Laboratory; and Fred Brechtel of Brechtel Manufacturing, Inc. have all done a fantastic job of integrating an unprecedented suite of instruments on the G-1, under a strict weight limit, power requirement constraints, and tight schedule.

The G-1 will carry a full payload of highly sophisticated instruments to measure aerosol size distribution, composition, and their climate-affecting properties. The payload also includes various instruments to measure aerosol precursors (gaseous pollutants such as sulfur dioxide, nitrogen oxides, and organic compounds) that upon oxidation in the presence of sunlight would form particles. All these measurements are extremely difficult to make while flying around at 100 meters per second.

In the coming days, I will introduce the AAF folks, the aircraft scientists, and the instruments that make these measurements possible.

Saturday, May 29, 2010

Most of the CARES participants have arrived with their specialized instruments. The remaining instruments will be coming in shortly. I will introduce all of them and their instruments in the coming days. At the moment everybody is very busy hauling, unpacking, and installing their equipment in the trailers at the two sites.

I would like to take this opportunity on behalf of the CARES team to thank our hosts, Mr. Laduan Smedley, Director of Administrative Services, and Dr. Derrick Booth, Asst. Dean of Science and Engineering, at American River College and Ms. Wendy Westsmith, Principal, at Northside School and their staff members for the kind hospitality and help as we settle down in our new home away from home for the next month.

The PNNL team did a great job of setting up the inlet towers and plumbing inside the trailers at both the sites. The inlet system is basically a combination of pipes that bring air into the trailer (via a pump) and distributes it to all the different instruments. It sounds simple, but several factors, such as the material of the pipe, number of bends, air flow rate, etc., have to be considered in the design and installation of the inlet system. It also takes several people to safely hoist the inlet tower and secure it, as you can see in the pictures.

Thanks to Jill Walters back at PNNL for arranging the delivery of all the necessary compressed gas cylinders (purified air, nitrogen, helium). They have arrived at both sites in a timely fashion. Purified air and nitrogen are needed in several aerosol sampling instruments, while helium is needed for weather balloons. Yes, we will be launching weather balloons from both the sites, which should be a fun activity to watch.

The G-1 aircraft arrives tomorrow at the McClellan Airport, which is located less than 3 miles from the American River College site. I will go to the airport tomorrow afternoon and see how we are doing there.

Thursday, May 27, 2010

The 18-wheeler full of PNNL instruments and related equipment arrived at the American River College site promptly at 8:00 AM. The estimated total weight of the equipment: about 20,000 pounds! The PNNL squad — Will Shaw, Danny Nelson, Jane McKinney, Dan Cziczo, Mikhail Pekour, Nels Laulainen, Jim Barnard, Chen Song, and I — spent the entire day unloading, unpacking, and sorting all the equipment and arranging the trailers. We were getting them ready for more CARES participants from other institutions who are scheduled to arrive tomorrow with additional equipment. Jeremy and Oscar from the PNNL IT department were busy setting up internet connections for the trailers.

As expected, the temperature started to drop in a hurry around noon, and dark clouds rolled in just as we were finishing unloading the truck at the Cool site. It was pouring by 1:00 PM, and we even had a brief spell of hail! The rain slowed us down a little, but we pretty much accomplished what we had set out to do for the day.

We all worked hard, and I was particularly impressed with Danny Nelson’s experience and skill in operating a forklift. Way to go, Danny! The pictures should give you an idea of how much stuff had to be carefully moved around today at just one site. Tomorrow we will continue unpacking the instruments, welcome our collaborators and help them settle into their assigned spots in the trailers.

While all this is happening here in Sacramento, the aircraft team, who I will introduce later, is busy preparing and test-flying the DOE G-1 aircraft back at PNNL. The plane is scheduled to arrive here on Sunday, May 30. The NASA B-200 King Air aircraft is already here. In the next couple of blog entries, I will describe the air sampling strategy we plan to use during CARES and the roles of ground sites and aircraft in achieving our science objectives.

Wednesday, May 26, 2010

Since this blog’s audience includes folks who may not be familiar with atmospheric aerosols and their role in climate change, I thought it would be worthwhile to provide a very short background.

Atmospheric aerosols are tiny particles suspended in air. They are present everywhere (in varying concentrations), and their sizes can range from a thousandth of a micron to a few microns (the average thickness of human hair is about 0.1 millimeter, which is 100 times bigger than 1 micron). Furthermore, these particles can be composed of naturally occurring substances such as soil dust, sea spray, organic compounds emitted from trees, etc., as well as manmade substances resulting from various types of air pollution, such as vehicular exhaust, power plant emissions, industrial emissions, etc.

While greenhouse gases such as carbon dioxide, water vapor, methane, and ozone tend to warm the earth’s atmosphere by absorbing infrared radiation emitted from the earth’s surface, aerosols generally tend to cool the atmosphere by scattering (reflecting) the incoming solar radiation. However, certain carbonaceous aerosols (i.e., those composed of carbon-containing compounds), formed from both manmade and natural processes, can absorb light and therefore tend to warm the atmosphere.

Aerosols are also precursors of clouds, which are significantly more efficient than aerosols in scattering light and cooling the atmosphere. The efficiency with which aerosols can scatter and absorb light and form clouds depend greatly on their size, type (chemical composition), and how they are vertically distributed in the earth’s atmosphere.

While tremendous progress has been made in the scientific understanding of the effects of aerosols on climate, significant uncertainties and knowledge gaps still exist in role of carbonaceous aerosols and their radiative effects, which essentially serve as motivations for the CARES field study.

The U.S. Department of Energy’s Atmospheric System Research (ASR) program is an international leader in climate-relevant atmospheric research related to aerosols, clouds, and cloud-aerosol interactions, and the CARES field study is a part of this program.

CARES officially begins on June 2. At the moment, we are setting up the two ground sites – one in Sacramento at the American River College and another in Cool, CA, at the Northside School where we will make intensive measurements of aerosols and their climate-affecting properties with a suite of specialized instruments.

The four construction trailers (two at each site) that will house all the instruments arrived today. Washington State University’s mobile atmospheric chemistry laboratory also arrived today. Most of the day was spent in setting these trailers, leveling them, and hooking up power. The trucks carrying all the instruments will arrive early tomorrow morning, and it will be a busy day unloading them and sorting everything out according to the two sites. Rain is in the forecast all day tomorrow, so we bought some tarps to protect the equipment while the trailers are still being prepared. Hope everything goes smoothly.

Tuesday, May 25, 2010

Hi, welcome to my CARES field study blog. I am on my flight to Sacramento, California, as I begin to write the first entry for my first blog.

Sacramento is the base for the month long (June 2-28) CARES field study that is funded by the U.S. Department of Energy (DOE), and it is focused on improving the scientific understanding of the effects of certain types of air pollution and naturally occurring particles in the atmosphere (a.k.a. atmospheric aerosols) on climate change.

I will write more about the what, why, where, who, and how about CARES in the coming days, but before we embark on this exciting scientific adventure, I would like to take this opportunity to thank the entire CARES team who has worked diligently and sometimes around the clock to pull everything together.

The CARES research team includes more than 70 scientists, post-doctoral fellows, and students from 20 institutions (national laboratories, universities, and research organizations) across the United States. We have been preparing for this intensive field study for over a year now, and the last few months have been pretty hectic, to say the least.

I would also like to acknowledge and extend sincere thanks to the administrators, contracts personnel, engineers, aircraft pilots, mechanics, communications specialists, IT personnel, and other support staff at PNNL and other team institutions, who have worked very hard so execution of CARES can proceed smoothly, efficiently, and most importantly, safely. Thank you all for a job well done!

Now, let the adventure begin . . .Rahul