scholarly journals Variation of High and Low Level Circulation of Meiyu in Jiangsu Province in Recent 30 Years

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1258
Author(s):  
Ruoxin Hu ◽  
Lijuan Wang
Keyword(s):  
Western Pacific Subtropical High ◽  
Analysis Data ◽  
Jiangsu Province ◽  
Water Vapor Transport ◽  
Low Level ◽  
South Asia High ◽  
Westerly Jet ◽  
Daily Precipitation Data ◽  
The Western Pacific ◽  
Circulation Characteristics

By using the NCEP/NCAR re-analysis data from 1990 to 2019 and the daily precipitation data of CN05.1 gridded observation dataset, the high and low level circulation characteristics and their influence on the onset and precipitation of Meiyu in Jiangsu Province in recent 30 years are studied. Comparing Meiyu in the 2010s with that in the 1990s, it is found that during the 2010s Meiyu was characterized by a late arrival and less precipitation. There were obviously earlier Meiyu years in the 1990s, while no extremely early Meiyu year existed in the 2010s, which was mainly caused by the late northward jump of the upper jet and the ridge line of the western Pacific subtropical high (WPSH hereinafter) in the 2010s. Compared with the 1990s, the 2010s witnessed an eastward position of the South Asia high and a westward position of the subtropical westerly jet during the Meiyu period, which are not conducive to precipitation in the Yangtze-Huaihe region. At the same time, the cold air flowing southward to the Yangtze-Huaihe region was hindered in the 2010s due to the change of blocking in the middle troposphere. In the 2010s, the water vapor transport and the vertical transportation weakened, resulting in the decrease of precipitation in the Yangtze-Huaihe region.

Combined Effects of Synoptic-Scale Teleconnection Patterns on Summer Precipitation in Southern China

2020 ◽  
Author(s):  
Chao Wang
Keyword(s):  
East Asia ◽  
Extreme Precipitation ◽  
Southern China ◽  
Summer Precipitation ◽  
Western Pacific Subtropical High ◽  
Asia Pacific ◽  
Combined Effects ◽  
Teleconnection Patterns ◽  
South Asia High ◽  
Westerly Jet

<p>Using ERA-Interim daily reanalysis and precipitation data, the combined effects of East Asia-Pacific (EAP) and Silk Road (SR) teleconnection patterns on summer precipitation in southern China were investigated on synoptic to sub-monthly timescales. Combined EAP and SR patterns lead to more persistent and extreme precipitation in the Yangtze River Valley (YRV) and exhibit an obvious zonal advance between the South Asia High (SAH) and Western Pacific Subtropical High (WPSH) prior to its onset. During typical combined events, an overlap between the SAH and WPSH remains in a favorable position for Persistent Extreme Precipitation (PEP). Furthermore, SR-induced acceleration of the westerly jet stream and extra positive vorticity advection provide persistent upper-level divergence for YRV precipitation. An anomalous EAP-related cyclone/anticyclone pair over East Asia induces enhanced low-level southwesterlies to the northern anticyclone flank and northerlies from the mid-latitudes, advecting anomalously abundant moisture toward the YRV, resulting in clear moisture convergence. Moreover, the strong ascent of warmer/moister air along a quasi-stationary front may be crucial for PEP. During decay, the SAH and WPSH diverge from each other and retreat to their normal positions, and the strong ascent of warmer/moister air rapidly weakens to dissipation, terminating PEP in the YRV.</p>

Dynamic and Thermodynamic Relations of Distinctive Stratus Clouds on the Lee Side of the Tibetan Plateau in the Cold Season

2013 ◽  
Vol 26 (21) ◽  
pp. 8378-8391 ◽  
Author(s):  
Yi Zhang ◽  
Rucong Yu ◽  
Jian Li ◽  
Weihua Yuan ◽  
Minghua Zhang
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Eastern China ◽  
Cold Season ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Primary Role ◽  
Moist Air ◽  
Low Level ◽  
Stratus Clouds

Abstract Given the large discrepancies that exist in climate models for shortwave cloud forcing over eastern China (EC), the dynamic (vertical motion and horizontal circulation) and thermodynamic (stability) relations of stratus clouds and the associated cloud radiative forcing in the cold season are examined. Unlike the stratus clouds over the southeastern Pacific Ocean (as a representative of marine boundary stratus), where thermodynamic forcing plays a primary role, the stratus clouds over EC are affected by both dynamic and thermodynamic factors. The Tibetan Plateau (TP)-forced low-level large-scale lifting and high stability over EC favor the accumulation of abundant saturated moist air, which contributes to the formation of stratus clouds. The TP slows down the westerly overflow through a frictional effect, resulting in midlevel divergence, and forces the low-level surrounding flows, resulting in convergence. Both midlevel divergence and low-level convergence sustain a rising motion and vertical water vapor transport over EC. The surface cold air is advected from the Siberian high by the surrounding northerly flow, causing low-level cooling. The cooling effect is enhanced by the blocking of the YunGui Plateau. The southwesterly wind carrying warm, moist air from the east Bay of Bengal is uplifted by the HengDuan Mountains via topographical forcing; the midtropospheric westerly flow further advects the warm air downstream of the TP, moistening and warming the middle troposphere on the lee side of the TP. The low-level cooling and midlevel warming together increase the stability. The favorable dynamic and thermodynamic large-scale environment allows for the formation of stratus clouds over EC during the cold season.

Associated atmospheric mechanisms for the increased cold season precipitation over the Three-River Headwaters region from the late 1980s

2021 ◽  
pp. 1
Author(s):  
Shasha Shang ◽  
Gaofeng Zhu ◽  
Jianhui Wei ◽  
Yan Li ◽  
Kun Zhang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Hadley Circulation ◽  
Walker Circulation ◽  
Cold Season ◽  
Precipitation Variability ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Westerly Jet ◽  
Tropical Oceans

AbstractPrecipitation in the Three-River Headwater (TRH) region has undergone significant changes as a result of global warming, which can affect water resources in downstream regions of Asia. However, the underlying mechanisms of the precipitation variability during the cold season (October to April), are still not fully understood. In this study, the daily China gridded precipitation product of CN05.1 as well as the NCEP-NCAR reanalysis are used to investigate the characteristics of the cold season precipitation variability over the TRH region and associated atmospheric mechanisms. The cold season precipitation shows an increasing trend (5.5 mm decade-1) from 1961 to 2014, with a dry-to-wet shift in around the late 1980s. The results indicate that the increased precipitation is associated with the enhanced easterly anomalies over the Tibetan Plateau (TP) and enhanced southeasterly water vapor transport. The enhanced Walker circulations, caused by the gradients of sea surface temperature between the equatorial central-eastern Pacific and Indo-western Pacific in tropical oceans, resulted in strengthened easterly anomalies over the TP and the westward expansion of the anticyclone in the western North Pacific. Meanwhile, the changed Walker circulation is accompanied by a strengthened local Hadley circulation which leads to enhanced meridional water vapor transport from tropical oceans and the South China Sea toward the TRH region. Furthermore, the strengthened East Asia Subtropical Westerly jet may contribute to the enhanced divergence at upper level and anomalous ascending motion above the TRH region leading to more precipitation.

Scale sensitivity of the Gill circulation, Part II: Off-equatorial case

2021 ◽  
Author(s):  
Gilles Bellon ◽  
Beatriz Reboredo
Keyword(s):  
Diabatic Heating ◽  
Dynamical Response ◽  
Plane Case ◽  
Horizontal Scale ◽  
Overturning Circulation ◽  
Low Level ◽  
Heating Source ◽  
Horizontal Extent ◽  
Westerly Jet ◽  
Tropospheric Heating

Abstract We investigate the steady dynamical response of the atmosphere on the equatorial β-plane to a steady, localized, mid-tropospheric heating source. Following Part I which investigates the case of an equatorial diabatic heating, we explore the sensitivity of the Gill circulation to the latitudinal location of the heating, together with the sensitivity to its horizontal scale. Again, we focus on characteristics of the response which would be particularly important if the circulation interacted with the hydrologic and energy cycles: overturning circulation and low-level wind. In the off-equatorial case, the intensity of the overturning circulation has the same limit as in the equatorial case for small horizontal extent of the diabatic heating, which is also the limit in the f-plane case. The decrease in this intensity with increasing horizontal scale of the diabatic heating is slightly faster in the off-equatorial case than in the equatorial case, which is due to the increase of rotational winds at the expense of divergent winds. The low-level westerly jet is more intense than in the equatorial case, with larger maximum wind and eastward mass transport that tend to infinity for small horizontal extent of the diabatic heating. In terms of spatial characteristics, this jet has a similar latitudinal extent as in the equatorial case but, unlike in the equatorial case, it extends further equatorward than poleward of the diabatic-heating center. It also extends further eastward than in the equatorial case.

scholarly journals Relationship Analysis between Runoff of Dadu River Basin and El Niño

2018 ◽  
Vol 246 ◽  
pp. 01074
Author(s):  
Zujian Zou ◽  
Yubin He
Keyword(s):  
River Basin ◽  
El Niño ◽  
El Nino ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
Tibet Plateau ◽  
Rainfall Runoff ◽  
Dadu River ◽  
The Western Pacific

The Dadu River Basin is located in the transitional zone between the Qinghai-Tibet Plateau and the Sichuan Basin. It is alternately affected by various weather systems such as the western Pacific subtropical high, the Qinghai-Tibet high (anti-cyclone), the southwest warm and humid air current, and the southeast monsoon. The western Pacific subtropical high is one of the main influencing factors of rainfall runoff in the basin. During the El Niño period, the western Pacific subtropical high moved eastward and the position was southward. The warm and humid airflow and the southeast monsoon northward changed, and the rainfall runoff in the Dadu River Basin changed.By analyzing the development of the El Niño phenomenon, Divide an El Niño process into different stages of occurrence, development, and end. Combining the characteristics of the Dadu River runoff in each stage, Studying the runoff situation of the Dadu River Basin under different strengths and weaknesses of the El Niño phenomenon. Using the correlation method to establish a model of the relationship between the abundance of the Dadu River Basin and the El Niño strength and weakness. Providing new ideas and new methods for the accurate prediction of the incoming water of the Dadu River under the abnormal climatic conditions of El Niño. It provides technical support for reservoir dispatching, flood control dispatching and economic dispatching of cascade hydropower stations, and provides experience for other river basins to cope with complex climate situations and improve water regime forecasting levels.

scholarly journals The Changing Impact Mechanisms of a Diverse El Niño on the Western Pacific Subtropical High

2019 ◽  
Vol 46 (2) ◽  
pp. 953-962 ◽  
Author(s):  
Mengyan Chen ◽  
Jin‐Yi Yu ◽  
Xin Wang ◽  
Wenping Jiang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Western Pacific Subtropical High ◽  
Western Pacific ◽  
Subtropical High ◽  
The Western Pacific
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