Preprint Article Version 1 This version is not peer-reviewed

Impact of Snow-Darkening by Deposition of Light-Absorbing Aerosols on Snow Cover in the Himalaya-Tibetan-Plateau and Influence on the Asian Monsoon: A Possible Mechanism for the Blanford Hypothesis 

Version 1 : Received: 21 September 2018 / Approved: 22 September 2018 / Online: 22 September 2018 (23:18:38 CEST)

A peer-reviewed article of this Preprint also exists.

Lau, W.K.M.; Kim, K.-M. Impact of Snow Darkening by Deposition of Light-Absorbing Aerosols on Snow Cover in the Himalayas–Tibetan Plateau and Influence on the Asian Summer Monsoon: A Possible Mechanism for the Blanford Hypothesis. Atmosphere 2018, 9, 438. Lau, W.K.M.; Kim, K.-M. Impact of Snow Darkening by Deposition of Light-Absorbing Aerosols on Snow Cover in the Himalayas–Tibetan Plateau and Influence on the Asian Summer Monsoon: A Possible Mechanism for the Blanford Hypothesis. Atmosphere 2018, 9, 438.

Journal reference: Atmosphere 2018, 9, 438
DOI: 10.3390/atmos9110438

Abstract

The impact of snow darkening by deposition of light absorbing aerosols (LAAs) on snow cover over the Himalaya-Tibetan-Plateau (HTP) and influence on the Asian monsoon are investigated using the NASA Goddard Earth Observing System Model Version 5 (GEOS-5). We find that during April-May-June, deposition of LAAs on snow leads to a reduction in surface albedo, initiating a sequence of feedback processes, starting with increased surface solar radiation, rapid snowmelt in HTP and warming of the surface and upper troposphere, followed by enhanced low-level southwesterlies and increased dust loading over the Himalayas-Indo-Gangetic Plain. The warming is amplified by increased dust aerosol heating, and subsequently amplified by latent heating from enhanced precipitation over the Himalaya foothills and northern India, via the Elevated Heat Pump (EHP) effect during June-July-August. The reduced snow cover in the HTP anchors the enhanced heating over the Tibetan Plateau and its southern slopes, in conjunction with an enhancement of the Tibetan Anticyclone, and the development of an anomalous Rossby wavetrain over East Asia, leading to weakening of the subtropical westerly jet, and northward displacement and intensification of the Mei-Yu rainbelt. Our results suggest that atmosphere-land heating by LAAs, particularly desert dust play a fundamental role in physical processes underpinning the snow-monsoon relationship proposed by Blandford more than a century ago.

Subject Areas

snow-darkening, light-absorbing aerosols, dust and black carbon, elevated-heat- pump effect, snow cover–monsoon relationship, Blanford hypothesis

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