Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

ARM Cloud Aerosol Precipitation Experiment (ACAPEX)

14 January 2015 - 12 February 2015

Lead Scientist: L. Ruby Leung

Observatory: AMF, 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 percent 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 consisted of the deployment of the ARM Mobile Facility 2 (AMF2) and the ARM Aerial Facility (AAF) Gulfstream-1 aircraft 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 in 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 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 quantify 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

The NOAA research vessel Ronald H. Brown, above, played host to the AMF2 for ACAPEX. The G-1 returned to McClellan Airfield in Sacramento, California, for flights over the Sierra Nevada and Pacific Ocean.
The NOAA research vessel Ronald H. Brown, above, played host to the AMF2 for ACAPEX. The G-1 returned to McClellan Airfield in Sacramento, California, for flights over the Sierra Nevada and Pacific Ocean.

Co-Investigators

Chris Fairall Kimberly Prather Ryan Spackman
Jiwen Fan Marty Ralph Duane Waliser
Samson Hagos Veerabhadran Ramanathan Hailong Wang
Mimi Hughes Daniel Rosenfeld
Chuck Long Steven Rutledge

Related Publications

2017

Fairall C, S Matrosov, C Williams, and E Walsh. 2017. "Estimation of Rain Rate from Airborne Doppler W-band Radar in CALWATER2." Journal of Atmospheric and Oceanic Technology, , 10.1175/JTECH-D-17-0025.1. ONLINE.

Neiman P, N Gaggini, C Fairall, J Aikins, J Spackman, L Leung, J Fan, J Hardin, N Nalli, and A White. 2017. "An Analysis of Coordinated Observations from NOAA's Ronald Brown Ship and G-IV Aircraft in a Landfalling Atmospheric River over the North Pacific during CalWater-2015." Monthly Weather Review, 145(9), 10.1175/MWR-D-17-0055.1.

Cordeira J, F Ralph, A Martin, N Gaggini, J Spackman, P Neiman, J Rutz, and R Pierce. 2017. "Forecasting Atmospheric Rivers during CalWater 2015." Bulletin of the American Meteorological Society, 98(3), 10.1175/BAMS-D-15-00245.1.

2016

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.

Ralph FM, KA Prather, D Cayan, JR Spackman, P DeMott, M Dettinger, C Fairall, R Leung, D Rosenfeld, S Rutledge, D Waliser, AB White, J Cordeira, A Marin, J Helly, and J Intrieri. 2016. "CalWater Field Studies Designed to Quantify the Roles of Atmospheric Rivers and Aerosols in Modulating U.S. West Coast Precipitation in a Changing Climate." Bulletin of the American Meteorological Society, 97(7), 10.1175/bams-d-14-00043.1.


View All Related Publications

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
Paul DeMott Ice Nucleation Spectrometer - Ronald H. Brown Order Data
Jonathan Gero Marine Atmospheric Emitted Radiance Interferometer 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
Nicholas Nalli Ozone Sondes 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 Mentor Processed Meteorological Data Order Data
Stephen Springston Mentor Processed Particle Soot Absorption Photometer (PSAP) Data Order Data
Stephen Springston Mentor Processed Trace Gas Data 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
AERI Atmospheric Emitted Radiance Interferometer Browse Data
AOS Aerosol Observing System Browse Data
AOSMET Meteorological Measurements associated with the Aerosol Observing System Browse Data
CCN Cloud Condensation Nuclei Particle Counter Browse Data
CEIL Ceilometer Browse Data
CPC Condensation Particle Counter Browse Data
CSPHOT Cimel Sunphotometer Browse Data
HSRL High Spectral Resolution Lidar Browse Data
HTDMA Humidified Tandem Differential Mobility Analyzer Browse Data
IRT Infrared Thermometer Browse Data
KAZR Ka ARM Zenith Radar Browse Data
LDIS Laser Disdrometer Browse Data
LSSONDE Microwave Radiometer-Scaled Sonde Profiles Browse Data
MPL Micropulse Lidar Browse Data
MPLCMASK Cloud mask from Micropulse Lidar Browse Data
MWACR Marine W-Band (95 GHz) ARM Cloud Radar Browse Data
MWR Microwave Radiometer Browse Data
MWR3C Microwave Radiometer, 3 Channel Browse Data
NAV Navigational Location and Attitude Browse Data
NEPHELOMETER Nephelometer Browse Data
OZONE Ozone Monitor Browse Data
PBLHT Planetary Boundary Layer Height Browse Data
PRP Portable Radiation Package Browse Data
PSAP Particle Soot Absorption Photometer Browse Data
RWP Radar Wind Profiler Browse Data
SONDE Balloon-Borne Sounding System Browse Data
S-TABLE Stabilized Platform Browse Data
TSI Total Sky Imager Browse Data