Modification of the convective adjustment time‐scale in the Kain–Fritsch eta scheme for the case of weakly forced deep convection over the Tibetan Plateau region

2019 ◽  
Vol 145 (722) ◽  
pp. 1915-1932 ◽  
Author(s):  
Chenghai Wang ◽  
Di Wu ◽  
Feimin Zhang
Keyword(s):  
Tibetan Plateau ◽  
Time Scale ◽  
Deep Convection ◽  
The Tibetan Plateau ◽  
Plateau Region ◽  
Adjustment Time ◽  
Convective Adjustment

Extracting the cumulative distribution location of highly intermittent river from Sentinel-1 time series in an alpine catchment on the Tibetan Plateau

2021 ◽  
Author(s):  
Junyuan Fei ◽  
Jintao Liu
Keyword(s):  
Time Series ◽  
Tibetan Plateau ◽  
Time Scale ◽  
Proper Time ◽  
Cumulative Distribution ◽  
The Tibetan Plateau ◽  
Statistical Features ◽  
Catchment Scale ◽  
Intermittent Rivers ◽  
Intermittent River

<p>Highly intermittent rivers are widespread on the Tibetan Plateau and deeply impact the ecological stability and social development downstream. Due to the highly intermittent rivers are small, seasonal variated and heavy cloud covered on the Tibetan Plateau, their distribution location is still unknown at catchment scale currently. To address these challenges, a new method is proposed for extracting the cumulative distribution location of highly intermittent river from Sentinel-1 time series in an alpine catchment on the Tibetan Plateau. The proposed method first determines the proper time scale of extracting highly intermittent river, based on which the statistical features are calculated to amplify the difference between land covers. Subsequently, the synoptic cumulative distribution location is extracted through Random Forest model using the statistical features above as explanatory variables. And the precise result is generated by combining the synoptic result with critical flow accumulation area.  The highly intermittent river segments are derived and assessed in an alpine catchment of Lhasa River Basin. The results show that the the intra-annual time scale is sufficient for highly intermittent river extraction. And the proposed method can extract highly intermittent river cumulative distribution locations with total precision of 0.62, distance error median of 64.03 m, outperforming other existing river extraction method.</p>

scholarly journals Transport of Asian surface pollutants to the global stratosphere from the Tibetan Plateau region during the Asian summer monsoon

2020 ◽  
Vol 7 (3) ◽  
pp. 516-533 ◽  
Author(s):  
Jianchun Bian ◽  
Dan Li ◽  
Zhixuan Bai ◽  
Qian Li ◽  
Daren Lyu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Global Climate ◽  
Pollutant Emissions ◽  
The Tibetan Plateau ◽  
Plateau Region ◽  
Radiative Processes ◽  
Asian Summer ◽  
The Impact

Abstract Due to its surrounding strong and deep Asian summer monsoon (ASM) circulation and active surface pollutant emissions, surface pollutants are transported to the stratosphere from the Tibetan Plateau region, which may have critical impacts on global climate through chemical, microphysical and radiative processes. This article reviews major recent advances in research regarding troposphere–stratosphere transport from the region of the Tibetan Plateau. Since the discovery of the total ozone valley over the Tibetan Plateau in summer from satellite observations in the early 1990s, new satellite-borne instruments have become operational and have provided significant new information on atmospheric composition. In addition, in situ measurements and model simulations are used to investigate deep convection and the ASM anticyclone, surface sources and pathways, atmospheric chemical transformations and the impact on global climate. Also challenges are discussed for further understanding critical questions on microphysics and microchemistry in clouds during the pathway to the global stratosphere over the Tibetan Plateau.

A Dynamically Computed Convective Time Scale for the Kain–Fritsch Convective Parameterization Scheme

2015 ◽  
Vol 143 (6) ◽  
pp. 2105-2120 ◽  
Author(s):  
O. Russell Bullock ◽  
Kiran Alapaty ◽  
Jerold A. Herwehe ◽  
John S. Kain
Keyword(s):  
Time Scale ◽  
Radiation Effects ◽  
Convective Available Potential Energy ◽  
Wrf Model ◽  
Grid Cell ◽  
Grid Spacing ◽  
Convective Parameterization ◽  
Convective Clouds ◽  
Adjustment Time ◽  
Convective Adjustment

Abstract Many convective parameterization schemes define a convective adjustment time scale τ as the time allowed for dissipation of convective available potential energy (CAPE). The Kain–Fritsch scheme defines τ based on an estimate of the advective time period for deep convective clouds within a grid cell, with limits of 1800 and 3600 s, based on practical cloud-lifetime considerations. In simulations from the Weather Research and Forecasting (WRF) Model using 12-km grid spacing, the value of τ often defaults to the lower limit, resulting in relatively rapid thermodynamics adjustments and high precipitation rates. Herein, a new computation for τ in the Kain–Fritsch scheme is implemented based on the depth of the buoyant layer and the convective velocity scale. This new τ formulation is applied using 12- and 36-km model grid spacing in conjunction with a previous modification that takes into account the radiation effects of parameterized convective clouds. The dynamically computed convective adjustment time scale is shown to reduce the precipitation bias by approximately 15% while also providing improved simulations of inland rainfall from tropical storms.

scholarly journals Microplastics Footprints in a High-Altitude Basin of the Tibetan Plateau, China

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2805
Author(s):  
Sansan Feng ◽  
Hongwei Lu ◽  
Tianci Yao
Keyword(s):  
Tibetan Plateau ◽  
Surface Waters ◽  
Human Activities ◽  
The Tibetan Plateau ◽  
Brahmaputra River ◽  
Plateau Region ◽  
Remote Areas ◽  
Water And Sediment ◽  
Lhasa River ◽  
And Behavior

Microplastics (MPs) are ubiquitous in the environment and have been drawing increasing attention; however, MPs’ occurrence and behavior in remote areas are not well understood. In this study, we quantified and characterized MPs from surface waters and sediments in a remote area, namely the Tibetan Plateau, China. The samples were collected from the Lhasa River and the lower reaches of the Brahmaputra River to better understand MPs’ sources to rivers of the Tibetan Plateau. MPs’ concentrations in water and sediment were 735 items/m3 and 51 items/kg, respectively, and the dominating MPs observed were fibers with size ranging from 100 to 500 µm. MP abundance increased nearly two-fold from upstream to downstream in the Brahmaputra River, associated with the inputs from downstream human activities and the inflows of tributaries (especially the Lhasa River). This study provides important bases for analyzing MPs migration processes in the plateau region.

scholarly journals Height dependence of the tendency for reduction in seasonal snow cover in the Himalaya and the Tibetan Plateau region, 1966–2001

2006 ◽  
Vol 43 ◽  
pp. 369-377 ◽  
Author(s):  
Kunio Rikiishi ◽  
Haruka Nakasato
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
The Tibetan Plateau ◽  
Plateau Region ◽  
Seasonal Snow ◽  
Snow Covered Area ◽  
Covered Area ◽  
Height Dependence ◽  
Seasonal Snow Cover ◽  
The Himalaya

AbstractThe dataset of Northern Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent for the period October 1966-July 2001 is analyzed to examine the height dependence of declining tendencies of seasonal snow cover in the Himalaya and the Tibetan Plateau region (25−45˚ N, 70−110˚E). It is found that the annual mean snow-covered area is decreasing in the Himalaya/Tibet region at a rate of ∼ 1 % a−1, implying that the mean snow-covered area has decreased by one-third from 1966 to 2001. The rate of decrease is largest (1.6%) at the lowest elevations (0−500 m). On the other hand, the length of the snow-cover season is declining at all elevations, with the greatest rate of decline in the 4000−6000 m height range. On the Tibetan Plateau (∼4000−6000 m a.s.l.), the length of the snow-cover season has decreased by 23 days, and the end date for snow cover has advanced by 41 days over this 35 year period. These rates might be somewhat overestimated by the binary definition of snow cover on satellite images. It is likely that the reduction of the snow surface albedo by deposition of Asian dust and anthropogenic aerosols may be at least partly responsible for earlier snowmelt.

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