|TITLE||THE RELATION BETWEEN THE GLOBAL HADLEY CIRCULATION AND THE CLIMATE IN THE MEDITERRANEAN REGION|
|AUTHORS||AL Scambiati (1), P Lionello (1,2), R D'Agostino (3)|
- Disteba, University of Salento, Lecce, Italy
- Euro Mediterranean Center on Climat Change, Lecce , Italy
- Max Planck Institute for Meteorology, Hamburg, Germany
|ABSTRACT||This study investigate the relation between the global Hadley Circulation (HC) and the climate in the Mediterranean region. The analysis is performed using the ensemble mean of the AMIP-like experiment ERA-20CM, the deterministic analysis ERA-20C and ERA-INTERIM. The analysis is restricted to the winter when the HC is stronger.
Firstly, we have calculated the mean position of the northern edge (NE) of the HC considering the zonal mean distribution of the following variables: the Outgoing Longwave Radiation (OLR), Precipitation, Precipitation minus Evaporation (P-E), the Mean Sea Level Pressure (MSLP) and the Stream function. Then the NE has been correlated with the distribution of the vertical velocity in the Mediterranean basin. The correlation distribution shows a strong and extended positive values over the eastern part of the basin and a negative values in the central part of the Mediterranean for the majority of the metrics and for both ERA-20CM ad ERA-20C. Therefore, the poleward movement of the winter HC provokes on the one hand, an increase of the downward motion in the eastern Mediterranean, on the other hand an intensification of the upward motion in the central part. After removing the ENSO signal (Nino3.4) the correlation distribution is substantially the same even if by far weaker. We can affirm that the correlations are partially consequence of an ENSO common driving. Finally, we have adopted the same procedure correlating the position of the NE, estimated with the different metrics, with the precipitation distribution overt the Mediterranean. What emerges is a poleward movement of the NE provokes a reduction of precipitation, but there is a clear disagreement in positioning the area of precipitation decreasing over the basin.|