Cloud Phase Recognition Based On Oxygen A Band And Co2 1.6 Mu M Band

The accurate recognition of the cloud phase has a great influence on the retrieval of the cloud top height. In order to improve the accuracy of obtaining the cloud top height with OCO-2, we proposed a cloud phase recognition algorithm based on the threshold of parameter alpha; alpha is defined as the reflectivity ratio of the region with weak continuous absorption of the oxygen A band to the region with weak continuous absorption of the CO2 1.6 mu m band. The alpha under different solar zenith angles and different ground albedos was calculated. The results show the following: under the same surface albedo and solar zenith angle, alpha was large for ice clouds and small for water clouds. Under the same surface albedo, the greater the solar zenith angle, the smaller the alpha of the ice cloud, and the larger the alpha of the water cloud. Under the same solar zenith angle, the greater the surface albedo, the smaller the alpha; when the solar zenith angle was less than 70 degrees, alpha can be used to effectively distinguish between the ice cloud and water cloud. This study used OCO-2 data of a single orbit over ocean to verify the feasibility of the algorithm through comparison with the CALIOP cloud phase product, which provided a basis for OCO-2 cloud top height estimation.