Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

Seasonal variations in cloud droplet number concentration (NCD) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An uncertainty analysis of the cloud model is included to reveal the main sensitivities of the cloud model. We compared the seasonal cycle in NCD, obtained using 9 yr of satellite data, to surface concentrations of potential cloud activating aerosols, measured at the SMEAR II station at Hyytiälä in Finland. The results show that NCD and cloud condensation nuclei (CCN) concentrations have no clear correlation at seasonal time scale. The fraction of aerosols that actually activate as cloud droplet decreases sharply with increasing aerosol concentrations. Furthermore, information on the stability of the atmosphere shows that low NCD is linked to stable atmospheric conditions. Combining these findings leads to the conclusion that cloud droplet activation for the studied clouds over the boreal forest is limited by convection. Our results suggest that it is important to take the strength of convection into account when studying the influence of aerosols from the boreal forest on cloud formation, although they do not rule out the possibility that aerosols from the boreal forest affect other types of clouds with a closer coupling to the surfac

Spatial equilibrium modeling for inter-regional trade flow estimation and agricultural policy analysis in Costa Rica

Tab. 51 ref. Tambi?n como serie: Field Report (REPOSA) no. 181. Continuaci?n de Field Report - Atlantic Zone Programm

Application of Meteosat Derived Meteorological Information for Crop Yield Predictions.

Abstract not availableJRC.G-Institute for the Protection and the Security of the Citizen (Ispra

Aggregation of evaporative fraction by remote sensing from micro to macro scale

The evaporative fraction of the surface energy balance has been favoured as a tool to describe the energy partitioning during daytime. It is shown that the evaporative fraction behaves temporally stable under heterogeneous terrain conditions in the Echival Field Experiment in Desertification-Threatened Areas (EFEDA). The evaporative fraction has been calculated by means of data retrieved from geostationary satellites using the SEBAL model. The overall attainable accuracy of the evaporative fraction changes with spatial resolution in relation to the correlation length of the land surface processes