Characteristic 20th and 21st century precipitation and temperature patterns and changes over the Greater Horn of Africa

Abstract

Characteristic patterns and changes in precipitation and temperature over the Greater Horn of Africa during the 20th and 21st century are analysed based on a sample of Coupled Model Intercomparison Project version 3 (CMIP3) models output. Analysis of the 11 CMIP3 models indicates that the equatorial eastern Africa region (including the entire Greater Horn of Africa (GHA)) have been experiencing a significant increase in temperature beginning in the early 1980s, in both A1B and A2 scenarios. All the Atmosphere Ocean Global Circulation Models (AOGCMs) analysed represent the correct mean annual cycle of precipitation, but there is a fairly large spread among the models in capturing the dominant bimodal peaks. In particular, all the models tend to overestimate the peak of the October-November-December (OND) season, while at the same time the peak of the March-April-May (MAM) season tends to be centered on May in the models instead of April as observed. The projected changes and probability distribution of minimum (T min ) and maximum (T max ) temperatures over the GHA sub-region based on PDFs constructed from daily values showed very diverse distributions for the present (1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000) and future (2046-2065; 2081-2100) periods. Whereas in the reference (1981-2000) the probability distribution functions (PDFs) constructed for both T min and T max , and during all the seasons had a near normal (but narrow) distribution, those of the future periods were quite diverse but generally very elongated, with significant shifts toward the positive tail. This generally implies that there is consensus among models and the ensemble mean about high likelihood of increase in extreme warmer T min and T max (more so T min ) in the future over the GHA region. Our results also show significant increase in the number of days with T min and T max greater the 2°C (above 1981-2000 average) by the middle as well as the end of 21st century in both the A1B and A1 scenarios. This is especially so during the June, July, and August (JJA) season where all the 92 days of the season indicate projected minimum temperature to increase by more than 2°C above the 1981-2000 average by the end of 21st century in both scenarios.

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