Tibetan Plateau gets wetter and greener in early summer in recent decades

Known as the "water tower of Asia," the Tibetan Plateau (TP) is the source of the 10 largest rivers in Asia, supporting more than 1.4 billion people and exerting a substantial influence on the water resources, agriculture, and ecosystems of the downstream countries. The change of water supplies over the TP has long been a subject of climate change research. Recently, a new study conducted by Dr. ZHANG Wenxia, Prof. ZHOU Tianjun and Dr. ZHANG Lixia from the Institute of Atmospheric Physics, Chinese Academy of Sciences, shows that the TP has grown significantly wetter each May since 1979.

According to their study, both increased precipitation frequency and intensity have made contributions to a wetter climate over TP. "Our further analyses show that the phase transition of the Interdecadal Pacific Oscillation around the late 1990s has promoted an earlier onset of the South Asian summer monsoon since 1979," says the first author Dr. ZHANG. "It happens via increasing meridional thermal contrast between the Indian Ocean and the Asian landmass in the pre-monsoon season." The earlier onset of the South Asian summer monsoon is then favorable for increased southwesterly water vapor transport and hence a wet TP in May.

"The wetting TP has influenced the regional hydrological cycle and ecosystem," says Prof. ZHOU Tianjun. The coherent increases in the soil moisture content and vegetation activities confirm the precipitation trend, indicating a wetting and greening TP in the early summer in recent decades. "This is especially beneficial for agriculture during the vegetation growing season. The increased rainfall also indicates richer water release from the TP to downstream areas, suggesting enhanced water availability in Asia." This study was recently published in the Journal of Geophysical Research: Atmospheres .

More information:
Wenxia Zhang et al, Wetting and greening Tibetan Plateau in early summer in recent decades, Journal of Geophysical Research: Atmospheres (2017). DOI: 10.1002/2017JD026468

Provided by Chinese Academy of Sciences