An Objective Technique for Estimating Tropical Cyclone Intensity over the Western North Pacific Utilizing FY-3 Microwave Imager Data

An objective technique for estimating tropical cyclone(TC) intensity over the Western North Pacific utilizing FY-3 Microwave Imager(MWRI) data is developed.As a first step, we investigated the relationship between the FY-3 MWRI brightness temperature parameters, which are computed in concentric circles or annuli of different radius in different MWRI frequencies, and the TC maximum wind speed from the TC best track data, we found that the parameters of lower frequency channels’ minimum brightness temperature，mean brightness temperature and ratio of pixels over the threshold brightness temperature with a radius of 1.0 or 1.5 degrees from the center give higher correlation.Then by applying principal components analysis (PCA) and multiple regression method ,we established an estimation model, finally, we evaluated our estimation model using independent verification data, the RMSE is 13kt.The estimated maximum wind speed always stronger in the early stages of development, but toward the mature stage, the results tend to be slightly weaker, and a reversal of positive and negative bias takes place with a boundary of around 70kt. For the TC which has a larger error, we found that they ofen with less organized cloud pattern and the asymmetric cloud pattern, so the classification of TC cloud pattern will help to improve the acuracy of the estimated TC intensity, and with the increase of statistical samples the accuracy of the estimated TC intensity will also be improved.