Reconstruct the Mesoscale Information of Typhoon with BDA Method Combined with AMSU‐A Data Assimilation Method

Abstract

This paper conducts the assimilating experiments and simulating experiments on typhoon “Aere” (No. 0418), by use of bogus data assimilation (BDA) method combined with advanced microwave sounding unit‐A (AMSU‐A) data assimilation method in the fifth‐generation National Center for Atmospheric Research (NCAR)/Penn State Mesoscale Model Version‐3 (MM5V3), the Radiative Transfer for TIROS‐N Operational Vertical Sounder Version‐7 (RTTOV) model, and their adjoint models. The Bogus data constructed with BDA technique are mainly located at sea level, while the peak energy contribution levels of the sounder channels selected in AMSU‐A data assimilation technique are mainly located at upper troposphere. The two types of data can reconstruct the meso‐scale information and improve the typhoon initial fields under the model dynamic forcing effect, respectively from the low level and the upper level of atmosphere during the assimilating process. Numerical results show that with four‐dimensional variational data assimilation (4DVAR) technique the circulation of initial fields is improved, the “warm core” of typhoon is enhanced, the “cloud water” phenomenon that occurs in the optimal initial fields and the numerical model is changed into “warm start” from “cold start”.