Comparison of TOGA COARE optical raingage data with radar reflectivity

This thesis compares bin-by-bin radar reflectivity data \nwith optical raingage data from TOGA COARE. Radar and \nraingage data were used from two ships, each carrying one \nradar and two raingages. This study analyzes six cases \nincluding a total of nine echoes. At simultaneous times, \nradar data from the opposite ship of the raingages, located \nat a distance of 100 to 135 km, were used to compare with \nthe raingage data. Also, at a time prior to the echo \npassing over the ship, radar data from the same ship of the \nraingages were used to compare with the raingage data. The \nray of radar data most likely to have passed over the ship \nwas chosen. Its bin-by-bin reflectivity data were converted \nto rainfall rates using a Z-R relationship from GATE. These \nrates were compared with the rainfall rates from the \nraingages at the corresponding times by performing a timespace \nconversion using the echo speed. The data was then \nplotted using identical scales for direct comparisons. \nGraphs were also generated to compare cumulative percentages \nof area from the echo occupied by a rainfall rate with \ncumulative percentages of time from the raingages that the \nrainfall rate was occurring. \nThe radar data from the same ship as the raingages \nshowed excellent representations of the raingage data. The \ntrends and maximum peaks were quite comparable between these two data sets. Most of the time rainfall rates recorded by \nthe raingages exceeded rates recorded by the radars. These \ntwo sets of data differed by a factor of two or less. Due \nto beam widening and interference from intervening echoes, \nusing the opposite radars at a distance of 100 to 135 km \nshowed poor representations of the raingage data .