Transmission formulation for random stacks of clouds

Abstract

We present a formulation for calculations of photon transmission for random cloud stacks (maximum-random overlap) that can be applied in contrail avoidance experiments, for instance. Other applications are not excluded. In contrail avoidance experiments, the application of the method is to estimate in advance whether contrails are detectable with a satellite instrument and whether therefore the result of the experiment can be validated. For an established contrail avoidance procedure, the method can help to decide whether a contrail should be avoided if cirrus clouds in below the contrail would render the expected infrared radiation effect quite low. The method is derived in some detail, and a practical example is provided. For applications it is necessary to empirically determine or estimate a transmission threshold, that likely depends on the viewing geometry, the spatial resolution and the wavelength of the satellite instrument. An IDL-code is available to interested users.

Keywords

• clouds and contrails
• radiation transmission
• satellite data
• visibility