The Tibetan Plateau Summer Monsoon in the CMIP5 Simulations

Abstract Temporal variability within the Tibetan Plateau summer monsoon (TPSM) is closely linked to both the East and South Asian summer monsoons over several time scales but has received much less attention than these other systems. In this study, extensive integrations under phase 5 of the Coupled Model Intercomparison Project (CMIP5) historical scenarios from 15 coupled general circulation models (CGCMs) and Atmospheric Model Intercomparison Project (AMIP) runs from eight atmospheric general circulation models (AGCMs) are used to evaluate the performance of these GCMs. Results indicate that all GCMs are able to simulate the climate mean TPSM circulation system. However, the large bias associated with precipitation intensity and patterns remains, despite the higher resolution and inclusion of the indirect effects of sulfate aerosol that have helped to improve the skill of the models to simulate the annual cycle of precipitation in both AGCMs and CGCMs. The interannual variability of the surface heat low and the Tibetan high in most of the AGCMs resembles the observation reasonably because of the prescribed forcing fields. However, only a few models were able to reproduce the observed seesaw pattern associated with the interannual variability of the TPSM and the East Asian summer monsoon (EASM). Regarding long-term trends, most models overestimated the amplitude of the tropospheric warming and the declining trend in the surface heat low between 1979 and 2005. In addition, the observed cooling trend in the upper troposphere and the decline of the Tibetan high were not reproduced by most models. Therefore, there is still significant scope for improving GCM simulations of regional climate change, especially in regions near extensive mountain ranges.

Download Full-text

Sensitivity of East Asian summer monsoon precipitation to the location of the Tibetan Plateau

Journal of Climate ◽

10.1175/jcli-d-21-0154.1 ◽

2021 ◽

pp. 1-36

Author(s):

Soo-Hyun Seok ◽

Kyong-Hwan Seo

Keyword(s):

Tibetan Plateau ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

General Circulation ◽

Asian Summer Monsoon ◽

East Asian ◽

Circulation Model ◽

Dynamical Response ◽

The Tibetan Plateau ◽

Asian Summer

AbstractRecent studies have highlighted that a primary mechanism of the East Asian summer monsoon (EASM) is the fluid dynamical response to the Tibetan Plateau (TP), that is, orographically forced Rossby waves. With this mechanism in mind, this study explores how changes in the location of the TP affect the EASM precipitation. Specifically, the TP is moved in the four cardinal directions using idealized general circulation model experiments. The results show that the monsoon aspects are entirely determined by the location of the TP. Interestingly, the strongest EASM precipitation occurs when the TP is situated near its current location, a situation in which downstream southerlies are well developed from the surface to aloft. However, southerlies into the EASM region weaken as the TP moves, which in turn reduces the precipitation. Nevertheless, as long as it moves in the east–west direction, the TP is likely to force the stationary waves that induce precipitation over the mid-latitudes (not necessarily over East Asia). In contrast, moving the TP well north of its original location does not induce strong monsoon flows over the EASM region, resulting in the driest case. Meanwhile, although the southward movement of the TP triggers downstream southerlies to some extent, it does not lead to an increase in the precipitation. Overall, these results show that the location of the TP is crucial in determining the EASM precipitation, and the latter is much more sensitive to the displacement of the TP in the meridional direction than in the zonal direction.

Download Full-text

Orographic Effects of the Tibetan Plateau on the East Asian Summer Monsoon: An Energetic Perspective

Journal of Climate ◽

10.1175/jcli-d-13-00479.1 ◽

2014 ◽

Vol 27 (8) ◽

pp. 3052-3072 ◽

Cited By ~ 58

Author(s):

Jinqiang Chen ◽

Simona Bordoni

Keyword(s):

Tibetan Plateau ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

Thermal Gradient ◽

General Circulation ◽

Asian Summer Monsoon ◽

East Asian ◽

Eastern China ◽

The Tibetan Plateau ◽

Asian Summer

Abstract This paper investigates the dynamical processes through which the Tibetan Plateau (TP) influences the East Asian summer monsoon (EASM) within the framework of the moist static energy (MSE) budget, using both observations and atmospheric general circulation model (AGCM) simulations. The focus is on the most prominent feature of the EASM, the so-called meiyu–baiu (MB), which is characterized by a well-defined, southwest–northeast elongated quasi-stationary rainfall band, spanning from eastern China to Japan and into the northwestern Pacific Ocean between mid-June and mid-July. Observational analyses of the MSE budget of the MB front indicate that horizontal advection of moist enthalpy, and primarily of dry enthalpy, sustains the front in a region of otherwise negative net energy input into the atmospheric column. A decomposition of the horizontal dry enthalpy advection into mean, transient, and stationary eddy fluxes identifies the longitudinal thermal gradient due to zonal asymmetries and the meridional stationary eddy velocity as the most influential factors determining the pattern of horizontal moist enthalpy advection. Numerical simulations in which the TP is either retained or removed show that the TP influences the stationary enthalpy flux, and hence the MB front, primarily by changing the meridional stationary eddy velocity, with reinforced southerly wind over the MB region and northerly wind to its north. Changes in the longitudinal thermal gradient are mainly confined to the near downstream of the TP, with the resulting changes in zonal warm air advection having a lesser impact on the rainfall in the extended MB region.

Download Full-text

Origins of East Asian Summer Monsoon Seasonality

Journal of Climate ◽

10.1175/jcli-d-19-0888.1 ◽

2020 ◽

Vol 33 (18) ◽

pp. 7945-7965 ◽

Cited By ~ 4

Author(s):

J. C. H. Chiang ◽

W. Kong ◽

C. H. Wu ◽

D. S. Battisti

Keyword(s):

Tibetan Plateau ◽

Summer Monsoon ◽

East Asian Summer Monsoon ◽

General Circulation ◽

Asian Summer Monsoon ◽

East Asian ◽

Circulation Model ◽

Northeastern China ◽

The Tibetan Plateau ◽

Asian Summer

AbstractThe East Asian summer monsoon is unique among summer monsoon systems in its complex seasonality, exhibiting distinct intraseasonal stages. Previous studies have alluded to the downstream influence of the westerlies flowing around the Tibetan Plateau as key to its existence. We explore this hypothesis using an atmospheric general circulation model that simulates the intraseasonal stages with fidelity. Without a Tibetan Plateau, East Asia exhibits only one primary convective stage typical of other monsoons. As the plateau is introduced, the distinct rainfall stages—spring, pre-mei-yu, mei-yu, and midsummer—emerge, and rainfall becomes more intense overall. This emergence coincides with a pronounced modulation of the westerlies around the plateau and extratropical northerlies penetrating northeastern China. The northerlies meridionally constrain the moist southerly flow originating from the tropics, leading to a band of lower-tropospheric convergence and humidity front that produces the rainband. The northward migration of the westerlies away from the northern edge of the plateau leads to a weakening of the extratropical northerlies, which, coupled with stronger monsoonal southerlies, leads to the northward migration of the rainband. When the peak westerlies migrate north of the plateau during the midsummer stage, the extratropical northerlies disappear, leaving only the monsoon low-level circulation that penetrates northeastern China; the rainband disappears, leaving isolated convective rainfall over northeastern China. In short, East Asian rainfall seasonality results from the interaction of two seasonally evolving circulations—the monsoonal southerlies that strengthen and extend northward, and the midlatitude northerlies that weaken and eventually disappear—as summer progresses.

Download Full-text

Variable resolution general circulation models: Stretched-grid model intercomparison project (SGMIP)

Journal of Geophysical Research Atmospheres ◽

10.1029/2005jd006520 ◽

2006 ◽

Vol 111 (D16) ◽

Cited By ~ 59

Author(s):

Michael Fox-Rabinovitz ◽

Jean Côté ◽

Bernard Dugas ◽

Michel Déqué ◽

John L. McGregor

Keyword(s):

General Circulation ◽

General Circulation Models ◽

Model Intercomparison ◽

Variable Resolution ◽

Grid Model ◽

Intercomparison Project

Download Full-text

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

National Science Review ◽

10.1093/nsr/nwaa005 ◽

2020 ◽

Vol 7 (3) ◽

pp. 516-533 ◽

Cited By ~ 4

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.

Download Full-text

Bias-corrected climate projections for South Asia from Coupled Model Intercomparison Project-6

Scientific Data ◽

10.1038/s41597-020-00681-1 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Vimal Mishra ◽

Udit Bhatia ◽

Amar Deep Tiwari

Keyword(s):

Climate Change ◽

Impact Assessment ◽

South Asia ◽

General Circulation ◽

Coupled Model ◽

General Circulation Models ◽

River Basins ◽

Climate Projections ◽

Model Intercomparison ◽

Intercomparison Project

Abstract Climate change is likely to pose enormous challenges for agriculture, water resources, infrastructure, and livelihood of millions of people living in South Asia. Here, we develop daily bias-corrected data of precipitation, maximum and minimum temperatures at 0.25° spatial resolution for South Asia (India, Pakistan, Bangladesh, Nepal, Bhutan, and Sri Lanka) and 18 river basins located in the Indian sub-continent. The bias-corrected dataset is developed using Empirical Quantile Mapping (EQM) for the historic (1951–2014) and projected (2015–2100) climate for the four scenarios (SSP126, SSP245, SSP370, SSP585) using output from 13 General Circulation Models (GCMs) from Coupled Model Intercomparison Project-6 (CMIP6). The bias-corrected dataset was evaluated against the observations for both mean and extremes of precipitation, maximum and minimum temperatures. Bias corrected projections from 13 CMIP6-GCMs project a warmer (3–5°C) and wetter (13–30%) climate in South Asia in the 21st century. The bias-corrected projections from CMIP6-GCMs can be used for climate change impact assessment in South Asia and hydrologic impact assessment in the sub-continental river basins.

Download Full-text