Application Of TRMM/TMI Data In Estimating The Intensity Of Tropical Cyclones

Using the brightness temperature (TB) data of TRMM Microwave Imager (TMI) from2007—2009, we calculated the parameters in9channels (10,19,21,37and85GHz channel) and polarization correction temperature (PCT), including the maximum, minimum, average and AREA:ratio of pixels over the threshold in different region. We established a method for estimating the intensity of tropical cyclone (TC) in the western North Pacific, and tested tropical cyclones on2010independently. The results are as follows:(1) The TC intensity may be well reflected by TB data, the highest correlation coefficient can reach0.83, and the linear fitting root mean square error is close to business error. Low frequency channels TB is more sensitive to the underlying surface, which can be used to estimate the TC intensity on sea.(2) The parameter in the0.5°—1.5°latitude away from the TC center give higher correlation with TC intensity. And the correlation in Circular area is better than in the ring area; For TC on the sea, the most correlated parameter is the minimum value, average value and the threshold value of correlation times, maximum correlation the worst; For the Low frequency channels,except for10GHz, threshold value between260K and280K give higher correlation with the TC intensity.(3) The model fits well for TCs on sea which strength weaker than severe typhoon, the RMSE is about5m/s and the mean absolute error is about4m/s. For the TCs’strength between severe typhoon and super typhoon, the fitting error is bigger, the RMSE is9.65m/s and6.60m/s respectively, and the mean absolute error is7.76m/s and5.49m/s, respectively. For intensity of strong typhoon and above, model fitting error in the day (night) decreases (increases), with the minimum (maximum) error value of6m/s (11.96m/s), which indicates the estimate value is large in daytime and small at night. Generally, the model has certain applicability, the estimation error approaches Dvorak method’s and can be put into operational application.(4) The model fits well for TCs on land. The RMSE is6.22m/s and the mean absolute error is4.92m/s. For TCs which strength stronger than severe typhoon, the fitting error is small, the RMSE is4.34m/s and6.60m/s respectively, and the mean absolute error is3.63m/s and4.38m/s, respectively. For intensity below strong typhoon, the RMSE is about6m/s and the mean absolute error is about5m/s.