Ali Tokay

As part of the NASA Tropical Rainfall Measuring Mission Ground Validation (TRMM-GV) program, a field campaign was conducted in Florida Keys during August-September 2002. The purpose of the field campaign was to study the characteristics of rainfall over the Florida ...

An analysis of temporal variations in gamma parameters of raindrop spectra is presented utilizing surface-based observations from the Tropical Ocean Global Atmosphere Couple Ocean-Atmosphere Experiment. An observed dramatic change in the N0 parameter, found to occur during rainfall events with little change in rainfall rate, is suggestive of a transition from rain of convective origin to rain originating from the

Abstract A severe freezing rainstorm produced as much as 4.5 cm of freezing rain during an 18-h period at Champaign, Illinois, on 14-15 February 1990, resulting in over $12 million in damage, week-long power outages, and a federal disaster declaration. The ice storm ...

... authors thank Dr. Ramesh Kakar (NASA Headquarters), Mr. Richard Lawrence (Chief, NASA/GSFC TRMM Satellite Validation Office), Dr. Scott Braun (TRMM ... Tokay, A., PG Bashor, E. Habib, and T. Kasparis, 2008: Raindrop size distribution measurements in tropical cyclones. ...

... In this study, a rain event was defined based on at least one gauge tip occurrence in a 30-min period, similar to Cosgrove and Garstang (1995), and Habib and Krajewski (2002). ... Cosgrove, CM and M. Garstang, 1995: Simulation of rain events from rain-gauge measurements. ...

... This study was sponsored by NASA's TRMM program through Grants NAG5-9664 and NCC5-339 under Dr. Ramesh Kakar, Program Scientist. REFERENCES. Barthazy, E., W. Henrich, and A. Waldvogel. ... University of Chicago Press, 324 pp. Bolen, SM and V. Chandrasekar. ...

... J. Miriovsky a , A. Allen Bradley a , William E. Eichinger a , Witold F. Krajewski a , Anton Kruger a , Brian R. Nelson a , Jean ... Although spatial resolution of 1 km × 1° azimuth seems high, evencasual weather observers intuitively recognize that rainfall can vary significantly over ...

Serial reflectivity measurements from paired instruments are examined during two field campaigns in order to examine the precision of the measurements. The instruments studied are two collocated Joss-Waldvogel disdrometers (JWD) at Wallops Island, VA and two collocated profilers deployed at Ji-Parana, Brazil during Tropical Rainfall Measuring Mission (TRMM) Large-Scale Biosphere-Atmosphere Experiment. Differencing the measured reflectivity from the instrument pairs eliminated

ABSTRACT One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve coldseason precipitation measurements in mid- and high latitudes through the use of high-frequency passive microwave radiometry. For this purpose, the Weather Research and Forecasting model (WRF) with the Goddard microphysics scheme is coupled with a Satellite Data Simulation Unit (WRF-SDSU) to facilitate snowfall retrieval algorithms over land by providing a virtual cloud library and corresponding microwave brightness temperature measurements consistent with the GPM Microwave Imager (GMI). When this study was initiated, there were no prior published results using WRF at cloud-resolving resolution (1 km or finer) for high-latitude snow events. This study tested the Goddard cloud microphysics scheme in WRF for two different snowstorm events (a lake-effect event and a synoptic event between 20 and 22 January 2007) that took place over the Canadian CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Validation Project (C3VP) site in Ontario, Canada. The 24-h-accumulated snowfall predicted by WRF with the Goddard microphysics was comparable to that observed by the ground-based radar for both events. The model correctly predicted the onset and termination of both snow events at the Centre for Atmospheric Research Experiments site. The WRF simulations captured the basic cloud patterns as seen by the ground-based radar and satellite [i.e., CloudSat and Advanced Microwave Sounding Unit B (AMSU-B)] observations, including the snowband featured in the lake event. The results reveal that WRF was able to capture the cloud macrostructure reasonably well. Sensitivity tests utilizing both the "2ICE" (ice and snow) and "3ICE" (ice, snow, and graupel) options in the Goddard microphysical scheme were also conducted. The domain- and time-averaged cloud species profiles from the WRFsimulations with both microphysical options show identical results (due to weak vertical velocities and therefore the absence of large precipitating liquid or high-density ice particles like graupel). Both microphysics options produced an appreciable amount of liquid water, and the model cloud liquid water profiles compared well to the in situ C3VP aircraft measurements when only grid points in the vicinity of the flight paths were considered. However, statistical comparisons between observed and simulated radar echoes show that the model tended to have a high bias of several reflectivity decibels (dBZ), which shows that additional research is needed to improve the current cloud microphysics scheme for the extremely cold environment in high latitudes, despite the fact that the simulated ice/liquid water contents may have been reasonable for both events. Future aircraft observations are also needed to verify the existence of graupel in high-latitude continental snow events.