基于风云三号微波成像仪的热带气旋强度的多元统计估计方法研究

STUDY ON THE MULTIVARIATE STATISTICAL ESTIMATION OF TROPICAL CYCLONE INTENSITY USING FY-3 MWRI BRIGHTNESS TEMPERATURE DATA

利用中国风云三号微波成像仪数据开展西北太平洋热带气旋强度多元统计估计方法研究。⑴分析各通道以热带气旋中心为圆心,不同半径的同心圆和同心圆环内的亮温参数与热带气旋最大风速之间的定量关系,结果表明:低频通道1.0°和1.5°以内亮温的最小值、大于某亮温阈值的象元百分比和平均值与最大风速之间的相关性最高。⑵利用主分量分析和多元回归方法建立适合于西北太平洋上的热带气旋强度估计模型,其独立样本检验的均方根误差为13 kt。此模型在热带气旋发展的初始阶段会出现最大风速的高估,而在热带气旋发展的成熟阶段会出现最大风速的低估,正负偏差的分界点出现在70 kt左右,偏差较大的个例大多是未形成规则的热带气旋云系结构,且具有非常明显的不对称性。因此估计热带气旋强度时考虑热带气旋的云系结构特征将有助于进一步提高估计精度,且随着热带气旋样本数的增多,精度也有望进一步提高。

A 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 this model using independent verification data, with the RMSE set at 13 kt. The estimated maximum wind speed is 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 70 kt. For the TC which has a larger error, we found that they are often with less organized and more asymmetric cloud patterns. Therefore, the classification of TC cloud pattern will help to improve the accuracy of the estimated TC intensity, which will also be improved with the increase of statistical samples.