Combining ASCAT and NEXRAD Retrieval Analysis to Explore Wind Features of Mesoscale Oceanic Systems

Abstract

AbstractOceanic mesoscale systems often produce heavy rainfall and can cause significant hazards in coastal regions and aviation. Surface features that are important in the evolution of these systems were examined combining the Advanced Scatterometer (ASCAT) on board the polar‐orbiting meteorological satellite series Metop‐A and ‐B and ground instrumentation; that is, Next Generation Weather Radars, soundings, buoys. Two case studies were analyzed, over the coastal United States, by reprojecting ASCAT wind and ground radar precipitation and wind retrievals over a common grid domain. ASCAT retrievals were in agreement with buoy and sounding measurements at distances greater than 30 km from the precipitation region. Enhanced uncertainty in ASCAT wind retrievals in heavy precipitation was represented by greater wind direction variability and increases in wind speed. Nevertheless, ASCAT was able to identify regions of convergence and divergence within the systems, as well as outflow boundaries associated with downdrafts, which agreed with wind fields retrieved from the single‐Doppler analysis. Quality flags reported by ASCAT were also examined against polarimetric radar retrievals. Thresholds for rain rate and median volume diameter (D0), corresponding to the boundary between flagged and unflagged ASCAT data, were variable among different cases. However, analysis of ice water path and liquid water path revealed that unflagged ASCAT data rarely exceeded approximately 0.5 kg/m2 in either parameter.