Characterization of shallow oceanic precipitation using profiling and scanning radar observations at the Eastern North Atlantic ARM observatory
Abstract. Shallow oceanic precipitation variability is documented using three second-generation radar systems located at the Atmospheric Radiation Measurement (ARM)
Eastern North Atlantic observatory: ARM zenith radar (KAZR2),
the Ka-band scanning ARM cloud radar (KaSACR2) and the X-band scanning ARM
precipitation radar (XSAPR2). First, the radar systems and measurement
post-processing techniques, including sea-clutter removal and calibration
against colocated disdrometer and Global Precipitation Mission (GPM)
observations are described. Then, we present how a combination of profiling
radar and lidar observations can be used to estimate adaptive (in both time
and height) parameters that relate radar reflectivity ( Z ) to precipitation
rate ( R ) in the form Z=αRβ , which we use to estimate
precipitation rate over the domain observed by XSAPR2. Furthermore, constant
altitude plan position indicator (CAPPI) gridded XSAPR2 precipitation rate
maps are also constructed. Hourly precipitation rate statistics estimated from the three radar systems differ because KAZR2 is more sensitive to shallow virga and XSAPR2
suffers from less attenuation than KaSACR2 and as such is best suited for
characterizing intermittent and mesoscale-organized precipitation. Further
analysis reveals that precipitation rate statistics obtained by averaging
12 h of KAZR2 observations can be used to approximate that of a 40 km radius domain averaged over similar time periods. However, it was
determined that KAZR2 is unsuitable for characterizing domain-averaged
precipitation rate over shorter periods. But even more fundamentally, these
results suggest that these observations cannot produce an objective domain
precipitation estimate and that the simultaneous use of forward simulators
is desirable to guide model evaluation studies.