Climatic change on the Tibetan Plateau: Potential Evapotranspiration Trends from 1961–2000

Abstract

Abstract. Time series of Penman-Monteith potential evapotranspiration estimates for 101 stations on the Tibetan Plateau and surrounding areas are analyzed in this paper. For the Tibetan Plateau as a whole potential evapotranspiration (PET) has decreased in all seasons. The average annual evapotranspiration rate decreased by 13.1 mm/decade or 2.0% of the annual total. Superimposed on this general decline are fluctuations ranging from app. 600 to 700 mm with above average rates in the 1970s and 1980s. On a regional basis, spatial trend distributions remain stable throughout the year with similar seasonal variations. Decreasing PET rates are more pronounced in winter and spring (80% of all stations) as compared to summer and autumn (58% of all stations). Maximum negative (positive) annual rates were recorded at two stations in the southern Qaidam Basin with −79.5 mm/decade (84.8 mm/decade) even though in general negative rates tend to be noticeably higher than positive rates.Changes in wind speed and to a lesser degree relative humidity were found to be the most important meteorological variables affecting PET trends on the Tibetan Plateau while changes in sunshine duration played an insignificant role. Stable daytime temperatures on the Tibetan Plateau have limited the importance of temperature trends for changes of PET rates. Negative evapotranspiration trends are therefore thought to be linked to a general decrease in intensity of the regional monsoon circulation rather than to reductions in sunshine duration. Reduced PET rates appear to be in contrast to a predicted increased hydrological cycle under global warming scenarios.

Using a global climate model to evaluate the influences of water vapor, snow cover and atmospheric aerosol on warming in the Tibetan Plateau during the twenty-first century

“…Liu and Chen (2000) estimated that the winter warming has been twice as large as the annual mean. However, comparisons between winter and annual warming rates vary significantly among other studies based on the selection of station and the observation period (Du et al 2004;Chen et al 2006;You et al 2007). Moreover between 1991 and 2000, Rangwala et al (2009) found that spring and summer months appeared to have warmed rapidly over the plateau.…”

“…For the late twentieth century, estimates of PET on the plateau by Chen et al (2006) and Zhang et al (2007) have shown decreasing trends of 1.5-2.0% per decade. These decreasing trends have been linked with decreases in surface wind speed and insolation.…”

“…This warming trend has been largest during the winter months; fall has the next highest warming rate, while summer and spring show relatively less warming (Du et al 2004;Liu and Chen 2000;Chen et al 2006;You et al 2007). Liu and Chen (2000) estimated that the winter warming has been twice as large as the annual mean.…”

Analysis of Evapotranspiration Variability and Trends in the Arabian Peninsula

“…In the contrary ET o and pan evaporation has shown to decrease in China (Thomas, 2000;Liu et al, 2004) and at a rate of 1.19 mm year −1 (Song et al, 2010) despite the rise in maximum daily temperature. In the Tibetan Plateau ET o decreases as well at a rate of 1.31 mm year −1 or 2.0% of the annual total evapotranspiration (Shenbin et al, 2006). The decrease in ET o has been attributed to the decrease in wind speed and net radiation.…”

Ni̇ğde İli̇’ndeki̇ Potansi̇yel Evapotranspi̇rasyon Tahmi̇nleri̇ni̇n Trend Anali̇zi̇

“…Shenbin ve ark. [2] Tibet platosu için potansiyel evapotranspirasyonu Penman Monteith yöntemini kullanarak hesaplamışlardır. Trendleri belirlemek için doğrusal regresyon analizi kullanmışlardır.…”