סמינר בחוג למדעי כדור הארץ: The role of the export of tropical moisture into midlatitudes for extreme precipitation events in the Mediterranean region
Shimon Krichak, TAU
The Mediterranean region (MR) is characterized by a significant number of synoptic events with exceptionally intense rainfall (heavy precipitating events, HPEs), taking place during the cool season. A number of international projects have been focused on the investigation of the phenomena. Many of the registered cool MR season HPEs took place during with intense Atlantic storms associated with intense exports of humid tropical air into the midlatitudes. The fact alludes a role of the processes in the Atlantic in the MR HPEs. To test the hypothesis we analyze the spatial distributions of a number of key atmospheric variables for more than 50 intense HPEs for the MR. The results of this evaluation for both individual and composite events suggest a notable role of poleward export of humid air of tropical origin into the midlatitude MR from the Atlantic Ocean and Arabian Sea. The export events arecharacterized by a strongly confluent flow ahead of a polar cold front, which concentrates the water vapor into narrow plumes (atmospheric rivers, AR). The tropical moisture exports are leading to formation of AR-like features also in the MR. It is also found that the linear trend (for 1979–2013) of the frequency of days with high amount of precipitable water (greater than 20 kg m−2) is consistent with recent changes in the character of precipitation over the MR and southern Europe.
מארגנת הסמינר: ד"ר רוית חלד