Millimeter Wavelength ARM Radar and AAF G1: Observations and Analysis from the ACAPEX Field Campaign

From late January to early March of 2015, the ARM Cloud Aerosol Precipitation Experiment (ACAPEX) deployed a variety of instruments to study atmospheric rivers as they make landfall along the western United States. Of particular interest to this study are the radars aboard the Ron Brown and the cloud probes on the AAF G1 aircraft. In order to analyze the atmospheric rivers, a research vessel (Ron Brown) containing two millimeter wavelength radars, KAZR and MWACR, was stationed offshore. Both radars are zenith pointing, providing a time series of radar reflectivity as clouds move over the Ron Brown. The ARM Aerial Facility (AAF) Gulfstream-1 (G1) aircraft flew coordinated flights over the Ron Brown, as well as many flights over the ocean and coastal regions nearby. The instruments that will be utilized are the Two-Dimensional Stereo Probe (2DS) and High Volume Precipitation Spectrometer-3 (HVPS3). These optical array probes measure cloud particle size distributions for particles with sizes between 10 µm and 19.6 mm. In order to study the atmospheric rivers over the ocean and as they make landfall, the KAZR and MWACR radars aboard the Ron Brown are utilized to examine the cloud structure over the ocean. When coordinated flights occurred, the radar and cloud probe data are compared by calculating reflectivity from the particle size distributions using T-matrix scattering methods. During atmospheric river events when the coordinated flights were not flown, the radar data is used to examine the clouds over the ocean. The cloud probe data is used to examine the clouds near shore and on land using properties such as cloud thickness, particle size distribution, and liquid water content for both precipitation and non-precipitating cases. This will provide an idea of the changes that occur to the clouds during an event as they move from the open ocean to land.