Atmos. Chem. Phys. Discuss., 11, 10935-10972, 2011
© Author(s) 2011. This work is distributed
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Potential evaporation trends over land between 1983–2008: driven by radiative or turbulent fluxes?
C. Matsoukas1, N. Benas2, N. Hatzianastassiou3, K. G. Pavlakis4, M. Kanakidou5, and I. Vardavas2
1Department of Environment, University of the Aegean, Mytilene, Greece
2Department of Physics, University of Crete, Heraklion, Greece
3Laboratory of Meteorology, Department of Physics, University of Ioannina, Ioannina, Greece
4Department of General Applied Science, Technological Educational Institute of Crete, Heraklion, Greece
5Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Heraklion, Greece

Abstract. We model the Penman potential evaporation (PE) over all land areas of the globe for the 25-year period 1983–2008, relying on radiation transfer models (RTMs) for the shortwave and longwave fluxes. Penman's PE is determined by two factors: available energy for evaporation and ground to atmosphere vapour transfer. Input to the PE model and RTMs comprises satellite cloud and aerosol data, as well as data from reanalyses. PE is closely linked to pan evaporation, whose trends have sparked controversy in the community, since the factors responsible for the observed pan evaporation trends are not determined with consensus. Our particular interest is the temporal evolution of PE, and the provided insight to the observed trends of pan evaporation. We examine the interannual trends of PE and various related physical quantities, such as net solar flux, net longwave flux, water vapour saturation deficit and wind speed. Our findings are the following: Global warming has led to a larger water vapour saturation deficit. Global dimming/brightening cycles in the last 25 years slightly increased the available energy for evaporation. PE trends seem to follow closely the trends of energy availability and not the trends of the atmospheric capability for vapour transfer, almost everywhere on the globe, with trends in the Northern hemisphere significantly larger than in the Southern. These results support the hypothesis that secular changes in the radiation fluxes, and not vapour transfer considerations, are responsible for potential evaporation trends.

Citation: Matsoukas, C., Benas, N., Hatzianastassiou, N., Pavlakis, K. G., Kanakidou, M., and Vardavas, I.: Potential evaporation trends over land between 1983–2008: driven by radiative or turbulent fluxes?, Atmos. Chem. Phys. Discuss., 11, 10935-10972, doi:10.5194/acpd-11-10935-2011, 2011.
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