Estimation of tropical cyclone central pressure from warm core intensity observed by the Advanced Microwave Sounding Unit-A (AMSU-A)

Abstract

   Estimation of tropical cyclone (TC) intensity, that is, minimum sea level pressure (MSLP) and maximum sustained wind speed, by using satellite data is important for disaster prevention and mitigation, especially where in situ data are sparse, such as over the ocean, but it is still a challenging issue. For decades, the Dvorak technique has been the principal satellite-based method used for TC intensity estimation at the Japan Meteorological Agency and other forecast centers. However, the Dvorak technique requires specification of the TC cloud pattern, and estimation of TC intensity from the pattern is subjective and empirical. This study developed a new MSLP estimation method that uses 55-GHz band brightness temperatures (TBs) observed by the Advanced Microwave Sounding Unit-A (AMSU-A). This method is based on a regression between TC warm core intensities obtained from AMSU-A TBs and MSLPs in the best-track data archived by the Regional Specialized Meteorological Center (RSMC) Tokyo - Typhoon Center for TCs that occurred during the 2008 TC season in the western North Pacific basin. The TC warm core intensities were corrected to reduce the possible errors, such as those due to AMSU-A coarse spatial resolution and TB attenuation caused by ice cloud and rain particles. The MSLPs for TCs during 2009-2011 were then estimated by using this new method and validated against the best-track MSLPs. In the validation results, the root mean square error was 10.1 hPa, and the bias was 0.3 hPa. The MSLP estimation error was within ±5 hPa for 51.0% of the total number of observations, and within ±10 hPa for 79.3% of the total. This new method has advantages over the Dvorak technique for estimating the intensities of TCs with a relatively large warm core and some specific cloud patterns.