Reexamination of Tropical Cyclone Wind-Pressure Relationship based on Aircraft Data in the Western North Pacific

The wind-pressure relationships (WPR) for tropical cyclones in west North Pacific are reexamined based on the aircraft data, CMA best track data and daily JRA-55 data during 1957-1987. Minimum sea level pressure (MSLP) is estimated from aircraft reconnaissance, and maximum surface wind speeds (MSW) are adjusted from the maximum wind speed at the flight level multiplying by the recommended ration suggested by Franklin et al. (2003). Results show that the mean MSLP is higher in 1957-1964 than that in 1965-1987 for each MSW group. Considering the possible influences of the change of reconnaissance instrument and technology in 1965 on the relationship between MSLP and MSW, Only the aircraft reconnaissance data after 1965 are used in the following analyses, which results in 1874 samples.

The linear effects of TC center latitude, size, translation speed, intensification trend, and environmental pressure on the wind-pressure relationships were examined. Results show that TCs moving fast, with small size, located in low latitude and high environmental pressure tended to have higher MSLP for a given MSW. The coupled effects of several predictors are also tested. The predictors refer to MSW² multiplying by latitude, MSW² multiplying by TC translation speed were selected based on the stepwise predictor selection procedure. Result suggests that the effect of latitude on WPR depends on the TCs intensity. MSLP decreases as latitude increases for TCs strength weaker or equal to category 2. For TCs with the intensity scale of category 3 or higher, MSLP tends to increase as latitude increases. Meanwhile, the effect of TC moving speed on MSLP is not significant for weak TCs. MSLP increases from 925.0 hPa (SPD=0) to 979.7 hPa (SPD=30 m/s) for TCs strength as category 3, while it only increases 7.1 hPa for tropical storm. At last, a new WPR model was developed, which resulted in mean absolute error of 6.8 hPa, which shows improvement over the Dvorak (1975), AH (1977) and Koba (1991) WPR models.