MULTIPLE AIRCRAFT MICROWAVE OBSERVATIONS OF STORMS OVER THE WESTERN PACIFIC-OCEAN

During the second half (January-February 1993) of the intensive observ ation phase of the Tropical Ocean Global Atmosphere/Coupled Ocean-Atmo sphere Response Experiment (TOGA/COARE), NASA deployed both DC-8 and E R-2 research aircraft in Townsville, Australia. A number of flights we re made over the western Pacific Ocean with the objective of studying strong equatorial convection and clouds. A host of microwave radiomete rs operating in the frequency range of 10-220 GHz were placed on board both aircraft. Many other instruments were also present in both aircr aft; among them was a 13.8-GHz radar in the DC-8 aircraft that provide s reflectivity profiles of atmospheric hydrometeors essential for the present study. Observations were made by both aircraft on weather syst ems of convection as well as of cloud radiation. Some of these observa tions were conducted with both aircraft flying over the same regions a t near coincidence but different altitudes. The nearly concurrent micr owave radiometric measurements at comparable frequencies from the two aircraft at the altitudes of about 11 and 20 km provide a unique means to examine the properties of hydrometeors associated with storms. Thr ee well-coordinated DC-8 and ER-2 aircraft flights over storms are des cribed below. All of the microwave radiometers and the 13.8-GHz radar functioned normally during these flights. Some radiometers on the ER-2 and the DC-8 aircraft have comparable frequencies; signatures' acquir ed by these radiometers from these flights are analyzed in detail. It is shown that storm-associated brightness temperature depressions obse rved at frequencies less than or equal to 90 GHz from two different al titudes are quite comparable. At high frequencies greater than or equa l to 150 GHz the brightness temperature depressions observed at 20-km altitude are significantly larger than those observed at 11-km altitud e in some portions of the storms. This suggests the presence of hydrom eteors in the 11- to 20-km altitude region that effectively scatter ra diation at frequencies greater than or equal to 150 GHz.