The Simulation of Typhoon Chanchu Infrared Channels Brightness Temperature
“珍珠”台风卫星红外通道亮温的数值模拟

The high cloud coverage in the tropics makes it easier for numerically simulated satellite radiation data,especially those in the infrared channels,to be subject to clouds.Improved simulation of satellite-derived temperature of brightness blackbody(TBB) data for tropical synoptic systems helps to verify numerical models for the tropics and improve the direct use of satellite information in assimilation.The work first uses the Weather Research and Forecasting(WRF) model to simulate the three-dimensional meteorological field of typhoon Chanchu,including the cloud structure,and physical quantities,such as total cloud fractions and cloud top pressure,are diagnostically studied.Then,version 8.7 of a fast radiative transfer model for TIROS Operational Vertical Sounder(RTTOV) is used to simulate the infrared TBB of the storm measured with the High resolution Infrared Radiation Sounder(HIRS) and simulations are compared for conditions with and without clouds.It is shown in the results that the RTTOV model cannot simulate the structure of Typhoon Chanchu accurately and the simulated temperature is generally higher than the observation if the cloud effect is not taken into account under such extreme condition as the typhoon.By including the threedimensional structure of clouds simulated by meteorological models,the RTTOV model can simulate the spiral structure on the infrared channels of HIRS/3 (like channels 4-10 and channels 13-19).Clouds have positive effect on the simulation of infrared channels that altitudes of peak energy are below the cloud layers.The TBB simulated with the scheme in this paper reproduces the structural characteristics of the typhoon and is well correlated with the observation.It shows that the scheme is one of the ways to verify model simulation.TBB of some infrared channels has the potential applicability in data assimilation of tropical synoptic systems.