| Understanding and quantifying the radiative forcing and energy redistribution of clouds in the atmosphere are important for studies related to the atmospheric radiation budget and climate change. Here we propose to construct time-series of the cloud shortwave radiative forcing and heating rate for overcast cases. In order to make the time series continuous, the data from partly cloudy skies will also be processed using the independent column approximation. Our focus will be on the Cabauw Experimental Site for Atmospheric Research (CESAR), but our method can also be applied on other profiling stations. Such sites provide the necessary high quality ground-based radiation data (preferrably provided by the BSRN network) and aerosol/cloud properties for surface model constraint. The SEVIRI instrument onboard MSG provides collocated radiation data and cloud properties at the top of the atmosphere (TOA). Simultaneous radiative closure at TOA and the surface will be imposed using SEVIRI narrowband radiances and BSRN broadband irradiances as model constraints, respectively. Subsequently we will retrieve shortwave cloud radiative forcing profiles and heating rates throughout the entire atmosphere together with upward irradiances at TOA. We will use GERB data for broadband validation of the modeled TOA fluxes. For the radiative transfer calculations we will use the Doubling-Adding KNMI (DAK) model. The combination of SEVIRI and BSRN measurements will also provide diurnal cycles of the radiative forcing and heating rate. The algorithm that will be used for this study will be integrated to an automatic tool and run on a daily basis in order to construct time series of the radiative forcing of clouds. These can be used for (1) process studies related to the indirect aerosol effect, (2) the detection of possible trends (monitoring), and (3) the evaluation of climate and weather models. |
