West Africa climate extremes and climate change indices

• Published in: International journal of climatology Vol. 38; no. S1; pp. e921 - e938
• Main Authors: Barry, A. A., Caesar, J., Klein Tank, A. M. G., Aguilar, E., McSweeney, Carol, Cyrille, Ahmed M., Nikiema, M. P., Narcisse, K. B., Sima, F., Stafford, G., Touray, L. M., Ayilari‐Naa, J. A., Mendes, C. L., Tounkara, M., Gar‐Glahn, Eugene V. S., Coulibaly, M. S., Dieh, M. F., Mouhaimouni, M., Oyegade, J.A, Sambou, E., Laogbessi, E. T.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.04.2018; Wiley Subscription Services, Inc
• Subjects: Annual precipitation; Atmospheric precipitations; Climate change; climate extremes; Climatic analysis; Climatic extremes; Climatic indexes; Cold days; Daily precipitation; daily temperature; Daily temperature range; Daily temperatures; Drought; indices; Maximum temperatures; Mean temperatures; Minimum temperatures; Precipitation; Rain; Rainfall; Stations; Statistical analysis; Statistical significance; Temperature; Temperature effects; Temperature index; Trends; Weather stations; West Africa; West Africa
• ISSN: 0899-8418; 1097-0088
• DOI: 10.1002/joc.5420

ABSTRACT Observational analyses of changing climate extremes over the West Africa region have been limited by the availability of long and high‐quality datasets. To help address this gap, a climate extremes indices workshop was held in the Gambia in December 2011 with participants from 14 West African countries. The resulting analysis utilized 15 annual indices derived from observed daily temperatures and 10 annual indices derived from observed daily precipitation. The analysis was conducted for 166 meteorological stations in 13 countries for 2 periods: 1960–2010 and 1981–2010. The analyses of trends in the annual mean temperature indices have identified statistically significant increases of 0.16 °C/decade and 0.28 °C/decade for mean annual maximum and mean annual minimum temperatures, respectively, averaged over all available land stations in the region during the last 50 years. The seasonal‐temperature‐related indices show significant patterns of warming in all seasons. The annual mean of daily minimum temperature has increased more than the annual mean of daily maximum temperature leading to a decreasing trend in the diurnal temperature range. Warm days and warm nights have become more frequent, and cold days and cold nights have become less frequent. The analyses of precipitation‐based indices indicate spatially non‐coherent changes throughout the study area with few statistically significant trends over the longer period. Exceptions to this are the simple daily intensity index and maximum 5‐day precipitation, which show significant increasing regional trends over both the shorter and longer periods. Additionally, over the recent period (1981–2010) most of the precipitation related indices show significant trends towards wetter conditions. However, this period of increased rainfall follows a decade of significantly drier conditions in the region – it is not clear whether the recent upward trends reflect the ‘recovery’ from this long drought period or represents a long‐term response to warming. Climate extremes indices were derived from daily temperature and precipitation data from 166 observing stations in 13 West African countries, and combined to provide a regional assessment of changing extremes for 1960–2010 and 1981–2010. Statistically significant warming trends indicate more frequent warm days and nights and less frequent cold days and nights. Precipitation‐based indices indicate weak spatial patterns with few significant trends over 1960–2010, but over 1981–2010 show significant trends towards wetter conditions.