Zirkulationsdynamische Telekonnektivität der Klimavariabilität im südlichen Afrika
Projektleitung an der Universität Würzburg:
Beteiligte Wissenschaftlerinnen und Wissenschaftler:
Teleconnections between interannual variability of summer rainfall in southern hemispheric Africa and the global tropospheric geopotential height field are examined by means of bi- and multivariate statistical methods. It is shown that the use of highpass filtered data is able to optimise correlation analyses. The main part of the investigation consists of a method for extracting statistically independent major coupling modes with high relevance to the whole rainfall variability. Indications about the physical basis of the teleconnections are derived from the spatial patterns of the modes as well as from the spatial and seasonal variations of their impact. The implications of the first three modes for the southern part of the study area are discussed in detail. Concerning the ENSO teleconnection (mode 1) a mid-tropospheric center at the Namibian coast is revealed as an atmospheric key area. Further more aspects about the role of upper tropospheric tropical-temperate troughs in the mechanism of signal transport are derived. The extraction of a second mode, describing a southern hemisphere wave pattern, confirms that the rainfall reducing influence of upper east-coast troughs is acting mainly independently from the ENSO mode. The third extracted mode represents the influence of sea surface temperatures in the Indian Ocean. Comparisons with former studies show that the presented method is able to split up different variability signals and allows a synthetic view of all major rainfall teleconnections.
Laufzeit: von 11.1997 bis 10.2000