云参数对AIRS亮温模拟计算的影响试验

由于云污染对大气红外遥感的严重干扰，大量红外资料遭到了舍弃。为 了充分同化红外资料，提高初始场精度和改善数值预报效果，利用通用辐射传输模式(Community Radiative Transfer Model, CRTM) 模拟了大气红外探测仪(Atmospheric Infrared Sounder, AIRS)的通道亮温，并分析了云类型、云层含水量、云厚度和云顶高度等云参数对AIRS亮温的 影响。结果表明：(1)由于云层对红外辐射的截断作用，只有高于云顶的大气才会对辐射亮温产 生影响；(2)随着云层积分含水量的增加，亮温逐渐减小，但其减速放缓，直至不变；有效半径较 大的粒子对辐射的散射作用较强，相应亮温较小；(3)若云顶高度固定不变，云厚度的变化 则不会对亮温产生影响；若云底高度固定不变，云层越厚，相应的亮温越小；(4)地面通道亮温 对云顶高度的变化比较敏感，云顶以上通道的亮温不受云顶高度变化的影响。

Test of Effect of Cloud Parameter on AIRS Brightness Temperature Simulation

Because of the serious interference of cloud contamination with atmospheric infrared remote sensing, a large number of infrared data are abnegated. To make full use of the infrared data in assimilation to improve the initial field accuracy and numerical prediction effectiveness, a general Community Radiative Transfer Model (CRTM) is used to simulate the brightness temperature of channels of the Atmospheric Infrared Sounder (AIRS) and analyze the effect of cloud parameters (cloud type, cloud moisture, cloud thickness and cloud top) on the brightness temperature of channels of AIRS. The results show that 1) Infrared radiation can be truncated by clouds, so that only the atmosphere above cloud top can affect the radiation; 2) The brightness temperature decreases gradually with the increase of water content, but its decrease rate will slow down until it is constant. The particles with a larger effective radius have stronger scattering for the radiation, so the corresponding brightness temperature will be lower; 3) For a constant cloud top height, the variation of cloud thickness will not affect the brightness temperature. For a constant cloud bottom height, the thicker the cloud is, the lower the brightness temperature will be; 4) Since the brightness temperature of ground channels are more sensitive to the variation of cloud top height, the brightness temperature of the channels above cloud top will not be changed.