台灣地區強降雨系統登陸前後結構與演化的觀測與分析-(第2-3年)(2/2)

It has been long recognized that in the retrieved thermodynamic fields using multiple-Doppler-radar synthesized winds, a bias with the form of an unknown constant exists at each horizontal level, leading to the uncertainty in the retrieved vertical structure. This constant, theoretically, can be determined by an in-situ independent measurement (e.g., by a balloon sounding) of the pressure and/or temperature at only one grid point on each horizontal plane. However, the temporal resolution of the sounding data is known to be very low. Therefore, in this study, it is proposed to design a new thermodynamic retrieval scheme so that the ambiguity in the retrieved thermodynamic fields’ vertical structure can be effectively mitigated without using the sounding data. The equation of state (EoS), since it bridges the pressure and temperature, is a candidate which can be used as an additional constraint in our algorithm. However, how to properly implement EoS to our variational scheme is the major task of this project. In additional to the aforementioned issue, when more than one in-situ observation is available on a given horizontal plane, how to determine which in-situ measurement can provide the best estimation of the bias correction is another research goal of this project.