Computation of atmospheric heating rates and surface irradiances using CALIPSO, CloudSat and MODIS derived cloud and aerosol properties

Cloud vertical profiles retrieved from CALIPSO and CloudSat data provide additional information that greatly improves the estimate of atmospheric radiative heating rates and potentially improves the estimate of the global surface radiation budget. To utilize CALIPSO and CloudSat cloud vertical profiles, we combined their profiles and generated merged profiles. We then used cloud and aerosol properties derived from CALIPSO and CloudSat in addition to those derived from MODIS by the CERES cloud algorithm in irradiance computations. Once the resulting modeled irradiances are compared with those from CERES standard products, we can assess the effect of CALIPSO and CloudSat vertical profiles in improving irradiance computations. Because of lower cloud base heights provided by the merged profiles compared with cloud base heights derived from MODIS cloud top heights by an empirical formula, a preliminary result indicates that the global annual mean surface longwave downward irradiance increases approximately by 7 Wm-2. The global annual mean surface shortwave irradiance decreases by 2 Wm-2. At top of the atmosphere (TOA), the agreement with CERES derived shortwave irradiance improves by 0.5 W m-2 when merged cloud profiles are used. However, the difference between modeled and CERES derived longwave irradiances increases by 1.6 Wm-2 because thin cirrus clouds frequently overlap with lower level clouds. Their vertical extinction profiles are often unknown even when the total optical thicknesses are constrained by those derived from MODIS. In addition, about 5% of the time when either CALIPSO or CloudSat or both detect clouds, MODIS derived cloud properties are not available because either MODIS does not detect clouds or a large solar zenith angle causes a difficulty in the retrieval. These two situations present a new challenge when one tries to utilize CALIPSO and CloudSat derived properties in addition to MODIS derived properties in computing irradiances.