A fast method for the retrieval of integrated longwave and shortwave top-of-atmosphere upwelling irradiances from MSG/SEVIRI (RRUMS)

摘要

A new Rapid Retrieval of Upwelling irradiances from MSG/SEVIRI (RRUMS) ispresented. It has been developed to observe the top-of-atmosphere irradiancesof small scale and rapidly changing features that are not sufficientlyresolved by specific Earth radiation budget sensors. Our retrieval takesadvantage of the spatial and temporal resolution of MSG/SEVIRI and providesoutgoing longwave and reflected shortwave radiation only by means of acombination of SEVIRI channels. The longwave retrieval is based on a simplelinear combination of brightness temperatures from the SEVIRI infraredchannels. The shortwave retrieval is based on a neural network that requiresas input the visible and near-infrared SEVIRI channels. Both LW and SWalgorithms have been validated by comparing their results with CERES and GERBirradiance observations. While being less accurate than their dedicatedcounterparts, the SEVIRI-based methods have two major advantages compared toCERES and GERB: their higher spatial resolution and the better temporalresolution. With our retrievals it is possible to observe the radiativeeffect of small-scale features such as cumulus clouds, cirrus clouds, oraircraft contrails. The spatial resolution of SEVIRI is3 km × 3 km in the sub-satellite point, remarkably better thanthat of CERES (20 km) or GERB (45 km). The temporal resolution is 15 min(5 min in the Rapid-Scan mode), the same as GERB, but significantly betterthan that of CERES which, being on board of a polar orbiting satellite, has atemporal resolution as low as 2 overpasses per day.