ARM Cloud Aerosol Precipitation Experiment (ACAPEX)

 

Authors

L. Ruby Leung — Pacific Northwest National Laboratory
Ryan Spackman — NASA - Ames Research Center
Marty Ralph — National Oceanic and Atmospheric Administration
Kimberly Prather — Scripps Institution of Oceanography
Daniel Rosenfeld — The Hebrew University of Jerusalem
Chris W. Fairall — NOAA- Earth System Research Laboratory

Category

General Topics

Description

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. The DOE ARM Cloud-Aerosol-Precipitation Experiment (ACAPEX) will take place in early 2015 in conjunction with the NOAA CalWater 2 field campaign to use both land and offshore assets to monitor (1) the evolution and structure of ARs from near their regions of development, (2) long range transport of aerosols in eastern North Pacific and potential interactions with ARs, and (3) 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. Measurements collected from the field campaigns will allow analysis and development and validation of models to improve understanding and modeling of aerosol-cloud-precipitation interactions.

Lead PI

L. Ruby Leung — Pacific Northwest National Laboratory