ARM Cloud Aerosol Precipitation Experiment (ACAPEX): Aerial Observations
14 January 2015 - 27 February 2015
Lead Scientist: L. Ruby Leung
Observatory: AAF, ACX
The western United States receives precipitation predominantly during the cold season when storms approach from the Pacific Ocean. The snowpack that accumulates during winter storms provides about 70-90% of water supply for the region. Understanding and modeling the fundamental processes that govern the large precipitation variability and extremes in the western U.S. is a critical test for the ability of climate models to predict the regional water cycle, including floods and droughts. Two elements of significant importance in predicting precipitation variability in the western U.S. are atmospheric rivers and aerosols. Atmospheric rivers (ARs) are narrow bands of enhanced water vapor associated with the warm sector of extratropical cyclones over the Pacific and Atlantic oceans. Because of the large lower-tropospheric water vapor content, strong atmospheric winds, and neutral moist static stability, some ARs can produce heavy precipitation by orographic enhancement during landfall on the U.S. West Coast. While ARs are responsible for a large fraction of heavy precipitation in that region during winter, much of the rest of the orographic precipitation occurs in post-frontal clouds, which are typically quite shallow, with tops just high enough to pass the mountain barrier. Such clouds are inherently quite susceptible to aerosol effects on both warm rain and ice precipitation-forming processes.
This campaign comprised the deployment of the DOE ARM Mobile Facility 2 (AMF2) and the ARM Aerial Facility (AAF) G-1 in a field campaign called ARM Cloud Aerosol Precipitation Experiment (ACAPEX), which took place in conjunction with CalWater 2 – a NOAA field campaign. The joint CalWater 2/ACAPEX field campaign aimed to improve understanding and modeling of large-scale dynamics and cloud and precipitation processes associated with ARs and aerosol-cloud interactions that influence precipitation variability and extremes in the western U.S. The observational strategy consisted of the use of land and offshore assets to monitor:
- the evolution and structure of ARs from near their regions of development
- the long-range transport of aerosols in the eastern North Pacific and potential interactions with ARs
- how aerosols from long-range transport and local sources influence cloud and precipitation on the U.S. West Coast where ARs make landfall and post-frontal clouds are frequent.
The AMF2 was deployed on a research vessel offshore and provided critical measurements to quantify the moisture budget and cloud and precipitation processes associated with ARs and to characterize aerosols and aerosol-cloud-precipitation interactions associated with aerosols from long-range transport in the Pacific Ocean. The G-1 aircraft probed the clouds that form over the ocean and their transformations upon landfall as well as the orographic effects over the coastal range and the Sierra Nevada. The G-1 flights provided the critical information needed for comparing the simulated and observed processes of the vertical profiles of cloud microstructure and the resultant precipitation initiation and glaciation. This allowed the development and validation of more realistic simulations that replicated the aircraft measurements and thus quantified more reliably the entities that cannot be obtained directly by the aircraft measurements to improve understanding and modeling of aerosol-cloud-precipitation interactions.
ARM Operational Periods: ARM Mobile Facility 2: 2015.01.12—2015.02.12 ARM Aerial Facility: 2015.01.02—2015.02.27
Nalli N, C Barnet, T Reale, Q Liu, V Morris, J Spackman, E Joseph, C Tan, B Sun, F Tilley, L Leung, and D Wolfe. 2016. "Satellite Sounder Observations of Contrasting Tropospheric Moisture Transport Regimes: Saharan Air Layers, Hadley Cells, and Atmospheric Rivers." Journal of Hydrometeorology, 17(12), 10.1175/JHM-D-16-0163.1.
Gero J, MH Westphall, RO Knuteson, N Nalli, and WL Smith. 2016. Sea Surface Emissivity, Temperature and Atmospheric Measurements from the M-AERI during the ACAPEX Campaign. In Hyperspectral Imaging & Sounding ofthe Environment, Washington DC: OSA.
Thompson DR, I McCubbin, BC Gao, RO Green, AA Matthews, F Mei, KG Meyer, S Platnick, B Schmid, J Tomlinson, and E Wilcox. 2016. "Measuring cloud thermodynamic phase with shortwave infrared imaging spectroscopy." Journal of Geophysical Research: Atmospheres, 121(15), 10.1002/2016jd024999.
Leung LR. 2016. ARM Cloud-Aerosol-Precipitation Experiment (ACAPEX) Field Campaign Report. Ed. by Robert Stafford, DOE ARM Climate Research Facility. DOE/SC-ARM-16-012.
Mather J. 2015. 2015 Annual Report. Ed. by Robert Stafford, DOE ARM Climate Research Facility. DOE/SC-ARM-15-084.
Beckman M and R Jundt. 2015. ARM Cloud Aerosol Precipitation Experiment Backgrounder. Ed. by Dana DuPont, ARM Climate Research Facility. DOE/SC-ARM-15-021.
Leung LR, K Prather, M Ralph, D Rosenfeld, R Spackman, P DeMott, C Fairall, J Fan, S Hagos, M Hughes, C Long, S Rutledge, D Waliser, and H Wang. 2014. ARM Cloud Aerosol Precipitation Experiment (ACAPEX) Science Plan. Ed. by Robert Stafford, U.S. DOE, Office of Science, Office of Biological and Environmental Research. DOE/SC-ARM-14-030.
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Campaign Data Sets
|IOP Participant||Data Source Name||Final Data|
|Duli Chand||Nephelometer and Particle Soot Absorption Photometer Data||Order Data|
|Jennifer Comstock||Two Dimensional Stereo (2DS) Particle Imaging Probe||Order Data|
|Paul DeMott||Continuous Flow Thermal Diffusion Chamber||Order Data|
|Paul DeMott||Ice Nucleation Spectrometer||Order Data|
|John Hubbe||Aircraft-Integrated Meteorological Measurement System||Order Data|
|John Hubbe||Particle Volume Monitor||Order Data|
|Alyssa Matthews||Cloud Droplet Probe||Order Data|
|Alyssa Matthews||High Volume Precip Spectrometer||Order Data|
|Alyssa Matthews||High Volume Precipitation Spectrometer - Images||Order Data|
|Alyssa Matthews||Two Dimensional Stereo (2DS) Particle Imaging Probe||Order Data|
|Alyssa Matthews||Water Content Monitor||Order Data|
|Fan Mei||Cloud Condensation Nuclei Counter||Order Data|
|Fan Mei||Cloud Imaging Probe||Order Data|
|Fan Mei||Condensation Particle Counter||Order Data|
|Fan Mei||Fast Cloud Droplet Probe (FCDP)||Order Data|
|Fan Mei||Meteorology/State/Position Parameters||Order Data|
|Mikhail Pekour||Counterflow Virtual Impactor (CVI)||Order Data|
|Mikhail Pekour||Optical Particle Counter - Counterflow Virtual Impactor||Order Data|
|Mikhail Pekour||Optical Particle Counter - Isokinetic||Order Data|
|Kimberly Prather||Aerosol Time-of-Flight Mass Spectrometer||Order Data|
|Arthur Sedlacek||Mentor Processed - Single Particle Soot Photometer||Order Data|
|Stephen Springston||Trace Gases||Order Data|
|Jason Tomlinson||Cloud Spectrometer and Impactor (CSI)||Order Data|
|Jason Tomlinson||Cloud and Aerosol Spectrometer||Order Data|
|Jason Tomlinson||Passive Cavity Aerosol Spectrometer||Order Data|
|Jason Tomlinson||Ultra High Sensitivity Aerosol Spectrometer||Order Data|
|Jason Tomlinson||Video||Order Data|
ACX Data Sources
|Name||Full Name||Browse Data|
||Atmospheric Emitted Radiance Interferometer||Browse Data|
||Aerosol Observing System||Browse Data|
||Meteorological Measurements associated with the Aerosol Observing System||Browse Data|
||Cloud Condensation Nuclei Particle Counter||Browse Data|
||Condensation Particle Counter||Browse Data|
||Cimel Sunphotometer||Browse Data|
||High Spectral Resolution Lidar||Browse Data|
||Humidified Tandem Differential Mobility Analyzer||Browse Data|
||Infrared Thermometer||Browse Data|
||Ka ARM Zenith Radar||Browse Data|
||Laser Disdrometer||Browse Data|
||Microwave Radiometer-Scaled Sonde Profiles||Browse Data|
||Micropulse Lidar||Browse Data|
||Cloud mask from Micropulse Lidar||Browse Data|
||Marine W-Band (95 GHz) ARM Cloud Radar||Browse Data|
||Microwave Radiometer||Browse Data|
||Microwave Radiometer, 3 Channel||Browse Data|
||Navigational Location and Attitude||Browse Data|
||Ozone Monitor||Browse Data|
||Planetary Boundary Layer Height||Browse Data|
||Portable Radiation Package||Browse Data|
||Particle Soot Absorption Photometer||Browse Data|
||Radar Wind Profiler||Browse Data|
||Balloon-Borne Sounding System||Browse Data|
||Stabilized Platform||Browse Data|
||Total Sky Imager||Browse Data|