Impact of atmospheric convection on south Tibet summer precipitation isotopologue composition using a combination of in situ measurements, satellite data, and atmospheric general circulation modeling

Abstract

Precipitation isotopologues recorded in natural archives from the southern Tibetan Plateau may document past variations of Indian monsoon intensity. The exact processes controlling the variability of precipitation isotopologue composition must therefore first be deciphered and understood. This study investigates how atmospheric convection affects the summer variability of δ18O in precipitation (δ18Op) and δD in water vapor (δDv) at the daily scale. This is achieved using isotopic data from precipitation samples at Lhasa, isotopic measurements of water vapor retrieved from satellites (Tropospheric Emission Spectrometer (TES), GOSAT) and atmospheric general circulation modeling. We reveal that both δ18Op and δDv at Lhasa are well correlated with upstream convective activity, especially above northern India. First, during days of strong convection, northern India surface air contains large amounts of vapor with relatively low δDv. Second, when this low‐δDv moisture is uplifted toward southern Tibet, this initial depletion in HDO is further amplified by Rayleigh distillation as the vapor moves over the Himalayan. The intraseasonal variability of the isotopologue composition of vapor and precipitation over the southern Tibetan Plateau results from these processes occurring during air mass transportation.

Water stable isotopes in the Yarlungzangbo headwater region and its vicinity of the southwestern Tibetan Plateau

“…In the northern slope of the central Himalaya and the southern TP, most ( Â90%) of the annual precipitation falls in summer (JJAS), the low river/stream d 18 O and d-excess values east of Saga in this study are consistent with the fact that the monsoonal moisture predominates surface water recharge in this area of the TP. Monsoonal moisture is transported along the Yarlungzangbo valley from the east and/or through low passes in the central Himalaya (Gao et al, 1985;Kang et al, 2002;Hren et al, 2009;He et al, 2015;Yu et al, 2015). The similarity between the average d-excess (mean: 3.091.2 ) and the average monsoon precipitation value (Â4 to Â6 ) provides compelling support for this notion.…”

“…# 2016 W. Ren et al This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license. (Gao et al, 1985;Hren et al, 2009), and less moisture is transported directly through low passes (Trans-Himalayan rivers) in the central Himalaya (Kang et al, 2002;Bookhagen et al, 2005;He et al, 2015). More recently, isotopic investigations in the Yarlungzangbo basin have sought to gain an insight into regional moisture sources and the 'isotopic altitude effect'.…”

Deuterium‐excess determination of evaporation to inflow ratios of an alpine lake: Implications for water balance and modeling

“…Isotopes and d‐excess in precipitation showed clear seasonality (Figures and ), which were similar to that of southern TP (Liu, Tian, Yao, & Yu, ; Tian et al, ; Yao et al, ). The lower isotopic values in summer were related to strong monsoon convective precipitation (Cai & Tian, ; He et al, ). Also, they may be related to the weather patterns in individual precipitation events (Guan, Zhang, Skrzypek, Sun, & Xu, ; Skrzypek et al, ).…”

Southern Tibetan Plateau ice core δ18O reflects abrupt shifts in atmospheric circulation in the late 1970s

“…At the intra-summer scale, different controls were identified for Lhasa precipitation δ 18 O variability . Combining daily precipitation isotopic composition measurements and satellite information on convection and water vapor isotopic composition, He et al (2015) showed a dominant control through convective activity above North India: enhanced convection (and increased precipitation above N. India) depletes surface water δ 18 O, and this depletion is further amplified along the orographic uplift of moister air, and finally by enhanced subsidence of depleted vapor towards Lhasa. Our study suggests that controls at the intra-seasonal time scale cannot be extrapolated at the inter-annual scale.…”