利用NOAA/AVHRR资料分析雾顶的微物理特征

Analysis of fog microphysical parameters from NOAA/AVHRR images

选取2006年的冷雾、暖雾和海洋平流雾3个个例,利用NOAA/AVHRR多光谱资料建立了RGB合成图,并反演生成了雾滴有效半径,利用可见光反射率、温度、雾滴有效半径等特征量,定量分析了雾顶微物理特征。分析表明,在RGB合成图上,雾呈现出纹理均匀、顶部光滑、边缘清晰的特点;3类雾的可见光反射率在30%~60%之间,较厚的雾可见光反射率较高,雾的有效半径小,为7~10μm,其值较稳定;与层状云相比,雾顶亮温较高,海洋平流雾的雾顶亮温比周围海表温度高。通过与地面观测值比较,反演的雾滴有效半径较为合理,说明反演结果较可靠。

Based on the NOAA/AVHRR multi-spectral data,the effective radius of particles on the fog top was retrieved via the reflectance of channel centered at 3.7μm,and the microphysical properties of fogs were displayed and analyzed by means of composite RGB images.Three cases of cold fog,warm fog and oceanic advection fog in 2006 are quantitatively analyzed by means of microphysical parameters on fog top,such as visible reflectance,brightness temperature and fog drop effective radius.The composite RGB images show that the fog has even grains,smooth top and clear edge;the visible reflectance of three kinds of fog are among 30%-60% and the thicker fog has larger reflectance and small effective radius with stable value between 7 and 10 μm;in comparison with layer cloud,fog has higher bright temperature and oceanic advection fog has bright temperature higher than surrounding ocean surface.The retrieval effective radius is close to the value of surface observation,which indicates that the retrieved results are reasonable.