Relationship between moisture budget components over the eastern Mediterranean

Abstract

AbstractAtmospheric water vapor budget analysis is carried out in a rectangular domain of 3.04 × 105 km2, over the eastern Mediterranean (EM) using NASA GOES‐1 reanalysis gridded (2.50 longitude by 20 latitude) data set, for a period of eight rainy seasons (October–April) in 1985–1993. All days have been divided into 6 groups, based on rainfall amount, and the relationships between daily water vapor budget components have been studied in relation to precipitation amounts.We found that the mean rainy season precipitation, P over the study region is, about 260 mm. The highest precipitation category (over 2.2 mm/day) contributed 63% of the total rainfall, and the next category (0.9 to 2.2 mm/day) contributed another 22%. These two rainfall categories were accompanied by deep upper troughs extending from the Black Sea to Crete and a mean sea level (MSL) cyclone near Cyprus. For the rest of the rainfall categories the upper air flow was nearly zonal, with no clear MSL cyclonic activity. The western boundary exhibited a net moisture inflow, increasing with rainfall amount. The southern boundary moisture inflow becomes significant only for the highest rainfall category.The correlation between P and both inflow and outflow was (+0.45), in agreement with similar studies over the US Midwest in summer. However, in contrast to the latter studies – our study shows no correlation between P and moisture flux divergence (MFD). A possible explanation for this is that winter rainfall over the Eastern Mediterranean is mostly associated with cold fronts, whereas in the Midwest convective rain develops in the warm sector, near the maximum MFD. Finally, both, recycling ratio R, and the correlation between daily P and E support the idea that rainfall over the EM originates, at least partly, in humidity evaporating from the Sea within the region. Copyright © 2009 Royal Meteorological Society