Project Components

The objectives of this Component are summarized in the acquisition and storage of the raw satellite, reanalysis and model data in order to be further analyzed for the scopes of the proposed research. Data from 5 different satellite instruments will be used along with ERA-interim data from ECMWF, data from a global chemical-aerosol-transport model and results from REGCM4 regional climate model simulations.

During and after the acquisition of the raw satellite and model data, we will develop programming tools in order to process and analyze these data. Various analysis techniques will be used in order to create a new spatially and temporally homogeneous dataset. The dataset will be used in the investigation of the aerosol direct and indirect effects. A daily high resolution (0.1x0.1 degree) and a moderate resolution (1x1 degree) gridded dataset is expected to emerge for the total of the satellite and model products mentioned above.

The marine, dust and anthropogenic fraction of the aerosol tropospheric load at a 0.1x0.1 and 1x1 degree resolution will be quantified. Emphasis will be given on the anthropogenic component of the aerosol load because it consists the core parameter for the quantification of the human induced aerosol indirect effect. The anthropogenic (τa), dust (τd) and marine (τm) aerosol optical depth at 550nm will be calculated on a daily basis using MODIS AOD₅₅₀ observations. The estimated daily values will afterwards be used as an input to a set of parameterizations in order to quantify the direct and indirect radiative effects of different types of aerosols. Simulated aerosol optical depth and aerosol direct radiative effect over Europe will be obtained based on regional climate simulations with REGCM4. The simulations will be used here and at a later stage for the evaluation of the model against the satellite-based aerosol and direct radiative forcing observations.

MODIS satellite-retrieved parameters from the high/moderate resolution gridded datasets will be used in order to investigate the aerosol-cloud relationships for the region of Eastern Mediterranean. The relations between AOD₅₅₀, Cloud effective radius (Re) and CDNC (Cloud Droplet Number Concentration) will be calculated for the investigation of the first aerosol indirect effect. The relations between AOD₅₅₀, Total cloud Cover(TCC) and Liquid/Ice phase cloud Water Path (LWP/IWP) for the investigation of the second indirect effect. We will also search for signs of the aerosol semi-direct effect. The aerosol cloud relations will be calculated for sub-regions characterized by the presence of predominant types of aerosols. The aerosol-cloud relations per aerosol and cloud type, per season or month will be the final outcome of this research. The same procedure will be repeated taking into account the relative position of aerosol and cloud layers as defined by CALIPSO observations. These relations are of high importance for the regional modeling community. For example, today, the REGCM regional climate model does not take into account aerosol indirect effects. Results from this research could potentially be used within the aerosol-cloud parameterizations which are going to be included into an upgraded version of REGCM model.

A novel technique was originally proposed by Quaas et al. (2008) in order to quantify the aerosol direct and indirect radiative effect using satellite data exclusively. The direct and indirect (first) radiative effect of the different aerosol types (e.g. anthropogenic, dust) can be estimated using the same equations for the different AOD₅₅₀ components (e.g. ta, td, etc.). The main challenge-objective here is to estimate the aerosol direct and indirect effects using aerosol and cloud observations only and not radiation data or radiative transfer models. Within the proposed research, the first aerosol indirect radiative effect is going to be examined. For the calculation of the second indirect radiative effect satellite-based albedo observations are needed which is out of the scope of this research. In addition, it has been shown that the large uncertainties of the method do not allow for a safe quantification of the second indirect radiative effect. The aerosol direct and indirect radiative effects will be calculated on a grid cell-by-grid cell basis. The outcome of this Component will be a high resolution (0.1x0.1 degree) direct and indirect aerosol radiative forcing climatology, which is expected to reveal many interesting local features concerning the aerosol-cloud-radiation interactions. The results will be compared with results from the moderate 1x1 degree resolution dataset allowing for the investigation of the footprint of the aerosol direct and indirect radiative effects. Finally, the satellite-based aerosol direct radiative forcing observations will be used for the evaluation of the model-based REGCM4 aerosol direct radiative forcing estimates.