Analysis on Typhoon Rananim Using Products Retrieved from ATOVS

Nowadays, the most widely used tropical cyclone estimation and position analysis techniques employed by operational forecasters are to analyze the infrared and visible satellite imagery. While these products provide invaluable information about the overall structure and strength of tropical cyclones, they often can't penetrate clouds to ascertain low-level storm structures. Relatively, certain waveleng ths of microwave energy are able to penetrate ice clouds (such as the cirrus above the storm). Therefore, it offers a unique perspective into tropical cyclone structures. Advanced TIROS Operational Vertical Sounding (ATOVS) is composed of the Advanced Microwave Sounding Unit (AMSU) and the High-resolution Infrared Radiation Sounder (HIRS/3), which are aboard the NOAA-16-18 satellites. With the International ATOVS Processing Package (IAPP) by Cooperative Institute of Meteorological Satellite Studies (CIMSS) of the University of Wisconsin (UW), the ATOVS data can be finally translated into the retrieval products including the atmospheric temperature profile, moisture profile in both clear and cloudy atmospheres. The domain of typhoon center cloud field is determine according to the coincident infrared image, and then the temperature anomalies are calculate by subtracting the average temperature of outer radius from the temperature at each grid in the domain. By analyzing the cross-section of temperature anomalies, the warm-core of typhoon Rananim can be seen in the upper-troposphere clearly as well as the distribution of strong precipitation in the lower altitude due to its contamination to the upper microwave radiation. But the area range of ATOVS data received by National Satellite Meteo rological Center (NSMC) is not wide enough, which can only receive the data of part of the Western North Pacific besides the mainland. By analyzing the area range of ATOVS retrieval data mapped with the tracks of Rananim from National Meteo rological Center (NMC), four ideal sets of ATOVS retrieval data are recieved. Under hydrostatic assumption, using the nearest NCEP/NCAR reanalyzed data as initial parameter and four sets of ATOVS data mapped with Rananim, the minimum sea level pressure (MSLP) is calculated respectively and compared with the typhoon warning report of NMC estimated from the visible and infrared method, the mean discrepancy of MSLP is found to be 11.8 hPa, showing similar time-variant tendency of Rananim as described by NMC. Therefore, by using ATOVS retrieval products, the thermal structure under the Center Dense Overcast of typhoon Rananim is better displayed; what's more, the relatively accurate intensity of typhoon is obtained when compared with the result of the operational departments.