Evidence of trends in daily climate extremes over southern and west Africa

Abstract

[1] There has been a paucity of information on trends in daily climate and climate extremes, especially from developing countries. We report the results of the analysis of daily temperature (maximum and minimum) and precipitation data from 14 south and west African countries over the period 1961-2000. Data were subject to quality control and processing into indices of climate extremes for release to the global community. Temperature extremes show patterns consistent with warming over most of the regions analyzed, with a large proportion of stations showing statistically significant trends for all temperature indices. Over 1961 to 2000, the regionally averaged occurrence of extreme cold (fifth percentile) days and nights has decreased by À3.7 and À6.0 days/decade, respectively. Over the same period, the occurrence of extreme hot (95th percentile) days and nights has increased by 8.2 and 8.6 days/decade, respectively. The average duration of warm (cold) has increased (decreased) by 2.4 (0.5) days/decade and warm spells.Overall, it appears that the hot tails of the distributions of daily maximum temperature have changed more than the cold tails; for minimum temperatures, hot tails show greater changes in the NW of the region, while cold tails have changed more in the SE and east. The diurnal temperature range (DTR) does not exhibit a consistent trend across the region, with many neighboring stations showing opposite trends. However, the DTR shows consistent increases in a zone across Namibia, Botswana, Zambia, and Mozambique, coinciding with more rapid increases in maximum temperature than minimum temperature extremes. Most precipitation indices do not exhibit consistent or statistically significant trends across the region. Regionally averaged total precipitation has decreased but is not statistically significant. At the same time, there has been a statistically significant increase in regionally averaged daily rainfall intensity and dry spell duration. While the majority of stations also show increasing trends for these two indices, only a few of these are statistically significant. There are increasing trends in regionally averaged rainfall on extreme precipitation days and in maximum annual 5-day and 1-day rainfall, but only trends for the latter are statistically significant.

Changes in daily climate extremes in the eastern and central Tibetan Plateau during 1961–2005

“…Both for precipitation and temperature, data plots are available for visual inspections to reveal more outliers as well as a variety of problems that cause changes in the seasonal cycle or variance of the data. Also, histograms of the data are created which reveal problems that show up when looking at the data set as a whole [Aguilar et al, 2005;New et al, 2006]. Figure 3 is an example of the plots used to quality control precipitation data.…”

“…[3] Precipitation and temperature extremes have been studied in many regions around the world, such as in the Asia-Pacific region [Griffiths et al, 2005;Manton et al, 2001], Caribbean region [Peterson et al, 2002], southern and west Africa [New et al, 2006], South America [Haylock et al, 2006;Vincent et al, 2005], Middle East [X. Zhang et al, 2005], Central America and northern South American [Aguilar et al, 2005], and central and south Asia [Klein Tank et al, 2006].…”

Analysis of mid-twentieth century rainfall trends and variability over southwestern Uganda

“…Such information is still scarce because of the few studies that have analyzed the relationship of climate patterns and water management among others especially in the East Africa region. For example, Kampata et al (2008), New et al (2006), Schreck and Semazzi (2004), Kruger and Shongwe (2004), Mahe et al(2001), King'uyu et al (2000), Nicholson (1996), Ogallo (1993), Beltrando (1990), Rodhe and Virji (1976), and Samson (1952) are among the most recent studies concerning long-term climatological trends that have fo-cused on surface air temperature and precipitation in Africa. From these and other studies, a range of potential climatic impacts on water management for various geo-graphic areas, flood prevention and control, drought man-agement, food and fiber production, etc.…”

Evaluation of CMIP5 Global Climate Models over the Volta Basin: Precipitation

“…Dry seasons are becoming drier, while rainy season precipitation is decreasing. is trend, if it continues, could significantly affect the production of crops and also the shifting of the rainy season (e.g., [64][65][66]). e trends also show changes in the 1960s and 1970s, shown in the change-point years.…”