Variations of trough positions and precipitation patterns in the mediterranean area

• Published in: Journal of Climatology
• Main Author: Jacobeit, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1987
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1002/joc.3370070503; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.3370070503; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.3370070503

Abstract Recent variations of circulation and climate can be studied by investigating even rather short periods of time as far as they display different modes or anomalies which may also act on larger timescales as more persistent ones. Thus a period of 10 years (September 1966 to August 1976) which could be covered by daily sets of 500hPa airflow data in the Atlantic‐European region and of precipitation data at 101 Mediterranean stations was chosen to examine the variable distribution patterns of upper troughs in the Mediterranean area and their corresponding patterns of precipitation anomalies. After the outline of trough axis distribution to eight successive longitudinal bands and of the different percentages of trough precipitation at various trough axis positions for the whole period of 10 years a subdivision into individual years was made to show some of the operative deviations both of the upper trough distribution and of the corresponding precipitation pattern in relation to the overall mean situation. Together with some circulation indices (zonal index, geopotential anomaly, measure of (he relative vorticity, specifications about the Westerlies' main branch) which have been calculated for the crucial upstream region of the North Atlantic, some basic tendencies concerning different circulation patterns and their consequences for the Mediterranean region could be outlined. Considering within‐type changes and the variations of further cyclonic elements this might serve for estimating climatological effects on larger time‐scales of more persistent anomalies of circulation.