Atmospheric moisture budget and its regulation on the variability of summer precipitation over the Tibetan Plateau

Abstract

Based on station observations and reanalysis data sets, the atmospheric moisture budget and its critical role in regulating the variability of summer precipitation over the Tibetan Plateau (TP) are investigated. Results indicate that the yearly variability of summer precipitation over the southern TP (STP) is mainly controlled by remote moisture transport. Local surface evaporation presents an infinitesimal interannual fluctuation, but it cannot be ignored since it is a large component of total precipitation amount in every summer. Although the incoming moisture transport at the western boundary of STP is much weaker than that at the southern boundary, it primarily influences the temporal variation of STP summer precipitation. Further analysis shows that the summer North Atlantic Oscillation (NAO) also possesses a significant impact on the variation of STP summer precipitation. A strong NAO apparently weakens the moisture transport at the western boundary, inducing less precipitation over the STP. When the NAO is strong, wave‐activity flux obviously diverges eastward from the subtropical high over northwestern Europe. Then such flux converges toward the western TP, which weakens the baroclinic vertical structure of atmospheric circulation over the TP. The NAO also influences the meridional position of the Asian jet stream and modulates the specific humidity and moisture transport at the western boundary of STP. In addition, the dynamic processes of the atmosphere are more important than the thermodynamic processes in regulating the variability of TP summer precipitation.

Atmospheric Water Transport to the Endorheic Tibetan Plateau and Its Effect on the Hydrological Status in the Region

“…For the TP, previous studies have documented that AW transport from the Arabian Sea, Bay of Bengal, and the Indian subcontinent dominates summer precipitation in the southeastern TP based on atmospheric reanalysis products and precipitation isotope techniques (Chen et al, ; Drumond et al, ; Feng & Zhou, ; Tian et al, ; Wang et al, ). Meanwhile, the AW transport from the western sources, the local recycling as well as the incursion of the polar air mass are the AW sources in the northwestern TP (Cannon et al, ; Drumond et al, ; Yu et al, ).…”

Indian Monsoon Low‐Pressure Systems Feed Up‐and‐Over Moisture Transport to the Southwestern Tibetan Plateau

“…LPSs are unlikely to propagate directly into the southwestern TP. Atmospheric moisture budget analyses have shown that water vapor transport from the southern boundary of Plateau dominates summer precipitation over the TP, but the transport routes remain unclear (Barros & Lang, ; Curio et al, ; Feng & Zhou, ; Wang et al, ). Thermally induced upslope winds could transport moisture along the southern periphery (Figure a); however, the Himalayas are sufficiently high that condensation removes most of the water during upslope flow, leaving little moisture available for precipitation in the interior of the TP (Dong et al, ).…”

Scale effects of topographic ruggedness on precipitation over Qinghai‐Tibet Plateau

“…Precipitation is relatively abundant in summer (wet season) as the large circulations of Indian and East Asia monsoons transport a vast amount of water vapor to the south and east Qinghai‐Tibet Plateau (Xu et al , ; Lu et al , ). Indian Ocean is the dominant source region of water vapor and precipitation over the southern Tibet in summer (Pan et al , ), and the local surface evaporation has a non‐negligible effect on the summer precipitation (Wang et al , ). The mean summer precipitation for 1997–2016 can be up to over 120 mm for the stations in the southern Tibet.…”