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Special Session 5: Ocean-atmosphere interaction, multi-scale climate variability and their implication for biogeochemical processes |
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Spatiotemporal characteristics of evapotranspiration variation across global dry land during 1982–2011
SS5-20-S
Xia Zhang* , The Institute of Atmospheric Physics, Chinese Academy of Sciences
Presenter Email: zhangxia@tea.ac.cn
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| Global warming has enhanced the interaction between the global energy and water cycle, and the change of the water balance will lead to frequent extreme droughts and floods. Surface evapotranspiration is an important process in the energy-water cycle, and it’s considered to be a key link when we understand climate change. Based on the observation (FLUXNET-MTE) and the model (ERA-Interim) of two sets of surface evapotranspiration data, during the year 1982 to 2011, we analyzed the spatiotemporal variation characteristics of global terrestrial ET, and chose six areas with significant changes to analyze the regional differences about amplitude, trends and intra-annual variation comparatively. The results show that, (1) The global terrestrial average annual ET values show a zonal spatial distribution with ET values decreasing prominently from equator towards the poles. The maximal ET value appears in the summer, while the minimum is in the winter. The ET values near the equator are big for four seasons. The ET value in summer across global land has the biggest standard deviation (45.76 mm/a). In the background of global climate turning change (around the year 1993), ET values' spatial distribution has a negative-to-positive decadal transformation, especially in Eurasian continent and Africa. (2) Most global terrestrial areas' average annual ET values have an increasing trend. In the arid and semi-arid areas, average annual ET values in the South Africa and American southwest have significant linear trends—the values in South Africa increase significantly with the trend coefficient of 25.14 mm/10a, while the values in American southwest decrease significantly with the coefficient of -19.86 mm/10a. By comparison, the values in Sahel belt, northern China and Australia show slight increasing trends, and the values in southern Argentina and Chile show a weak decreasing trend. ET values across most arid and semi-arid areas, during warm seasons, exist obvious differences under global climate turning change. (3) ET value is limited by meteorological factors such as temperature, precipitation, especially the temperature, and the correlations between ET and temperature have significant regional differences in different latitudes due to the coupling effects of various elements. |
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