Abstract
Changes in water circulation and uneven distributions of water resources caused by global warming are prominent problems facing the world at present. It is important to understand the influencing factors, and evapotranspiration (ET) is a key parameter for measuring the water cycle. However, understanding of spatiotemporal changes in actual evapotranspiration and its mechanism is still limited by a lack of long-term and large-scale in situ datasets. Here, the evolution of evapotranspiration in typical East Asian monsoon areas in China from 1989 to 2005 was analyzed with global land ET synthesis products. Evapotranspiration in China showed evident interdecadal variations around 1998; it decreased before 1998 and subsequently increased, which is inversely related to global ET changes. We further divided China into water-control and energy-control regions to discuss the factors influencing ET changes in each region. The interdecadal variations in increasing ET after 1998 in China were dominated by increasing potential evaporation in the energy-control region. An analysis using the empirical orthogonal function (EOF) method found that this occurred because ET is mainly manifested as decadal changes controlled by climate warming in the energy-control region and as interannual variations in the water-control region. The different feedbacks of ET on climate change in the two regions were also reflected in the difference in energy partition. The change in the Bowen rate (BR) did not increase climatic differences between energy- and water-control zones, but increases in the BR in arid summers significantly affected local weather and climate.
Highlights
Most of the precipitation that falls to the ground returns to the atmosphere in the form of evapotranspiration except for runoff and local storage, and evapotranspiration accounts for 60% on land [1]
The Intergovernmental Panel on Climate Change [11,12] noted that the global average land temperature has increased by 0.74–0.85 ◦ C in the past 100 years, which would directly affect the water content and cycle in the atmosphere, including global precipitation and evapotranspiration
We aim to answer the following questions: (1) How have actual ET and potential evaporation (PET) evolved in the typical East Asian monsoon region of China under global warming?
Summary
Most of the precipitation that falls to the ground returns to the atmosphere in the form of evapotranspiration except for runoff and local storage, and evapotranspiration accounts for 60% on land [1]. Changing the water cycle and evapotranspiration will affect regional ecosystems and climates under global warming and cause feedbacks, including acidification and heat waves [2,3,4,5,6,7]. The Intergovernmental Panel on Climate Change [11,12] noted that the global average land temperature has increased by 0.74–0.85 ◦ C in the past 100 years, which would directly affect the water content and cycle in the atmosphere, including global precipitation and evapotranspiration. For every 1 ◦ C increase in temperature, the atmospheric water content increases by 7% according to the Clausius–Clapeyron equation [13,14]. Evaporation does not show the expected increasing trend under global warming. Many studies have shown that pan ET and potential evaporation (PET) have decreased
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