Universität zu Köln

Seregina, Larisa S., Fink, Andreas H. ORCID: 0000-0002-5840-2120, van der Linden, Roderick ORCID: 0000-0002-7364-323X, Elagib, Nadir A. and Pinto, Joaquim G. (2019). A new and flexible rainy season definition: Validation for the Greater Horn of Africa and application to rainfall trends. Int. J. Climatol., 39 (2). S. 989 - 1013. HOBOKEN: WILEY. ISSN 1097-0088

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Abstract

Previous studies on observed or projected rainfall trends for the Greater Horn of Africa (GHA) generally focus on calendric 3-month periods, and thus partly neglect the complexity of rainfall seasonality in this topographically heterogeneous region. This study introduces a novel and flexible methodology to identify the rainfall seasonality, the onset, cessation and duration of the rainy seasons and the associated uncertainties from rainfall time series. The definition is applied to the Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) satellite product and an extensive rain gauge data set. A strong agreement with known seasonal dynamics in the region and the commonly used calendric rainy seasons is demonstrated. Compared to the latter definition, a clear added value is found for the new approach as it captures the local rainfall features (associated with, for example, the sea breeze), thus facilitating evaluations across rainfall seasonality borders. While previously known trends are qualitatively confirmed, trends are amplified in some regions using the flexible definition method. Notably, a drying trend in Tanzania and Democratic Republic of Congo and a wetting trend in central Sudan and parts of eastern Ethiopia and Kenya can be detected. The trends are regionally associated with changes in rainy season cessation. CHIRPS and station trend patterns are consistent over larger regions of the GHA, but differ in regions with known rainfall contributions from warmer cloud tops. Discrepancies are found in coastal and topographically complex areas, and regions with an unstable seasonality of rainfall. As expected, CHIRPS shows spatially more homogeneous trends compared to station data. The more precise definition of the rainy season facilitates the assessment of rainfall characteristics like intensity, rainfall amounts or temporal shifts of rainy seasons. This novel methodology could also provide a more adequate calibration of climate model simulations thus potentially enabling more realistic climate change projections for the GHA.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Seregina, Larisa S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Fink, Andreas H. UNSPECIFIED orcid.org/0000-0002-5840-2120 UNSPECIFIED van der Linden, Roderick UNSPECIFIED orcid.org/0000-0002-7364-323X UNSPECIFIED Elagib, Nadir A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pinto, Joaquim G. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-157399
DOI:	10.1002/joc.5856
Journal or Publication Title:	Int. J. Climatol.
Volume:	39
Number:	2
Page Range:	S. 989 - 1013
Date:	2019
Publisher:	WILEY
Place of Publication:	HOBOKEN
ISSN:	1097-0088
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PRECIPITATION PRODUCTS; INTERANNUAL VARIABILITY; MONSOON ONSET; EAST-AFRICA; SATELLITE; WESTERN; CIRCULATION; ENSEMBLE; DYNAMICS; TANZANIA Multiple languages Meteorology & Atmospheric Sciences Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/15739