| 1. |
- Lin, Changgui, 1985, et al.
(författare)
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A new perspective on solar dimming over the Tibetan Plateau
- 2019
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 39:1, s. 302-316
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Royal Meteorological Society Solar radiation changes (dimming/brightening) have recently received growing attention within the research community, although there is currently no generally accepted explanation. This article aims to provide a new perspective for identifying the reasons behind solar dimming/brightening by using long-term measurements of direct and diffuse solar radiation, unlike previous studies which have focused on global solar radiation. We postulate that extinction processes can be more readily revealed by direct and diffuse radiation measurements with the help of a modelling tool that treats the two components separately. An example is presented for Golmud and Lhasa in the northern and southern Tibetan Plateau (TP) respectively, over the period 1957–2013. The following is found: (a) ground-based observed cloud cover alone hardly explains the observed solar dimming at the two sites; (b) both the cloud-free direct radiation transmittivity (τdir) and diffuse radiation proportion (pdif) declined; (c) variations in pdifare overwhelmingly dominated by variations in aerosols, while those in τdirare related to variations in both aerosol and water vapour; (d) on top of the suggested reduced aerosol concentrations, decreased snow cover can partly explain declined diffuse radiation via lowered surface albedo; (e) the decline in τdircan be partly attributed to the wetting atmosphere via strengthened absorption; and (f) the impact of volcanic eruptions was also identified from such radiative parameters, lasting into the following summer and especially strong in the southern TP.
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| 2. |
- Wang, Yan, et al.
(författare)
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The Formation of a Dry-Belt in the North Side of Central Himalaya Mountains
- 2019
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 46, s. 2993-3000
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Tidskriftsartikel (refereegranskat)abstract
- ©2019. American Geophysical Union. All Rights Reserved. South Asian monsoon crosses the Himalayan Mountains (HMs) and brings moisture for precipitations in the South Tibetan Plateau. A distinct dry-belt was found in the north of the central HM region, where there are the highest and steepest mountains in the world. Through in situ and remote-sensing observations and convection-permitting numerical experiments, the current study demonstrates that the formation of the dry-belt is mainly due to the depletion of water vapor when the monsoonal flow climbs the steep south slope of the HMs. The foehn phenomenon is notable over the north slope of the HMs, but the hot and dry downslope flow does not significantly reduce the amount of the precipitation; instead, it can delay the peak of the diurnal precipitation in the north side of the HMs.
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| 3. |
- Zhou, X., et al.
(författare)
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Dynamical impact of parameterized turbulent orographic form drag on the simulation of winter precipitation over the western Tibetan Plateau
- 2019
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 53:1-2, s. 707-720
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Tidskriftsartikel (refereegranskat)abstract
- Sub-grid orographic drag directly acts on wind and impacts the regional water cycle through control of atmospheric water vapor (AWV) transport. The effect of turbulent orographic form drag (TOFD) on wind and precipitation is investigated in this study using the WRF model for a winter month over the western Tibetan Plateau (TP), where solid precipitation supplies large amounts of water resources. The diurnal cycle of wind components and atmospheric circulation simulated with TOFD are consistent with observations and ERA-Interim data, whereas stronger westerlies exist in the simulation without the TOFD scheme. The latter results in more zonal AWV transport from the west and more precipitation over the western TP and surroundings. The implementation of the TOFD scheme leads to reduced biases, when evaluated with two observation-based precipitation products. It is therefore concluded that this scheme has a clear dynamical control on the regional atmospheric water recharge and thus the parameterization of the small-scale orographic drag in the model helps to improve the prediction of wintertime precipitation in the western TP region.
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