HR: 16:30h
AN: H34D-03    [Abstracts]
TI: Decreasing Evapotranspiration on the Tibetan Highlands and its Implications for Agriculture
AU: * Thomas, A
EM: axel.thomas@geogr.uni-giessen.de
AF: Institute of Geography, Justus Liebig University Giessen, Senckenbergstr. 1, Giessen, 35390, Germany
AB: Evapotranspiration (ET) is one of the central factors of the hydrological cycle regulating the moisture transfer from soil and plants to the atmosphere. Feedback between soil moisture and atmospheric humidity, mainly governed by ET, may be directly responsible for variations in the strength of regional circulation of the Asian Monsoon System with the major part of this energy transfer conducted through the "elevated heating surface" of the Tibetan Plateau. No reliable information on spatial and temporal variations of ET rates on the Tibetan Plateau has been available until recently. Penman-Monteith ET estimates of 63 stations located on the Tibetan Plateau between 1591 and 4670 m a.s.l. are presented that show that despite the large altitude potential ET (PET) rates in some parts of the plateau are comparable to those of the South Chinese lowlands at similar latitudes (up to 1300mm a-1). In all seasons the major part of the stations show declining PET and pan evaporation rates that appear to be related to changes in solar radiation and wind speeds. On average PET rates (1961-2000) have decreased by 13.1mm decade-1 with annual trends at individual stations ranging from -79.5 mm to 84.8 mm decade-1. Water balance calculations point to decreasing water availability for agricultural production in the Central Tibetan valleys where most of the agricultural areas are located. In the major part of the Tibetan Plateau decreasing water availability appears to stand in contrast to an anticipated increase of the hydrological cycle under climate change conditions.
UR: http://www.staff.uni-mainz.de/thomasa/english/tibet/proj_tibet_03_2003_e.html
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
DE: 1813 Eco-hydrology
DE: 1818 Evapotranspiration
SC: Hydrology [H]
MN: 2007 Fall Meeting