卷云短波反射特性的模拟计算研究

Simulations of the Reflectance of Cirrus Clouds in Shortwave Spectral Region

利用通用大气辐射传输(CART)软件模拟计算了0.4～2.5μm波段卷云大气反射率,分析了卷云大气的反射率随波长、光学厚度、有效尺度、卷云高度和地表类型变化情况,并模拟计算了0.55,1.38,2.75μm波段卷云大气反射率间关系。结果表明,可见光到近红外波段,卷云大气反射率随卷云光学厚度的增大而增大。可见光波段,卷云大气反射率随卷云粒子有效尺度变化很小;近红外波段,卷云大气的反射率随卷云粒子有效尺度增大而减小;近红外大气强吸收波段,卷云大气的反射率随卷云高度的增大而增大。大气窗口区卷云大气的反射率随地表类型的变化有显著的变化。通过0.55μm和2.75μm波段,1.38μm和2.75μm波段的卷云大气反射率间关系可以反演卷云光学厚度和有效尺度。

The reflectance of cirrus atmosphere from 0.4μm to 2.5 μm is simulated by a combined atmospheric radiative transfer （CART） software. The effects of wavelength, optical thickness, effective size, cirrus altitude and surface type on the reflectance of cirrus atmosphere are analyzed. The relationships between reflectance of cirrus atmosphere at 0.55, 1.38 and 2.75μm bands are simulated. Results show that the reflectance increases with optical thickness from visible with near infrared wavelength regions. Variation of the reflectance with effective size of cirrus clouds is small at the visible band, and the reflectance decreases with effective size at near IR wavelength band. The reflectance increases with cirrus altitude at IR absorption band of water vapor. Variation of the reflectance with different surface types is distinct in the atmospheric window region. The cirrus optical thickness and effective size can be retrieved with the relationship between reflectance of cirrus atmosphere at 0.55 μm and 2.75 μm, 1.38μm and 2.75μm bands.