Boreal Summer Intraseasonal Oscillation and Its Possible Impact on Precipitation over Southern China in 2019

2021 ◽  
Vol 35 (4) ◽  
pp. 571-582
Author(s):  
Jieli Hong ◽  
Zongjian Ke ◽  
Yuan Yuan ◽  
Xie Shao
Keyword(s):  
Southern China ◽  
Intraseasonal Oscillation ◽  
Boreal Summer ◽  
Boreal Summer Intraseasonal Oscillation

scholarly journals The driving processes of concurrent hot and dry extreme events in China

2021 ◽  
Author(s):  
Fangxing Tian ◽  
Nicholas Klingaman ◽  
Buwen Dong
Keyword(s):  
Extreme Events ◽  
Southern China ◽  
Eastern China ◽  
Intraseasonal Oscillation ◽  
Silk Road ◽  
Height Anomaly ◽  
Boreal Summer ◽  
Boreal Summer Intraseasonal Oscillation ◽  
Silk Road Pattern ◽  
The Silk Road

<p>Sub-seasonal heatwave-driven concurrent hot and dry extreme events (HDEs) can cause substantial damage to crops, and hence to lives and livelihoods. However, the physical processes that lead to these devastating events are not well-understood.</p><p>Based on observations and reanalysis data for 1979-2016 over China, we show that HDEs occur preferentially over central and eastern China (CEC) and southern China (SC), with a maximum of 3 events year<sup>-1</sup> along the Yangtze Valley. The probability of longer-lived and potentially more damaging HDEs is larger in SC than in CEC. Over SC the key factors of HDEs—positive anomalies of surface air temperature and evapotranspiration, and negative anomalies of soil moisture—begin two pentads before maximising at the peak of the HDEs. These anomalies occur south of a positive height anomaly at 200 hPa, associated with a large-scale subsidence anomaly. The processes over CEC are similar to SC, but the anomalies begin one pentad before the peak. HDE frequency is strongly related to the Silk Road Pattern and the Boreal Summer Intraseasonal Oscillation. Positive phases of the Silk Road Pattern and suppressed phases of the Boreal Summer Intraseasonal Oscillation are associated with positive height anomalies over CEC and SC, increasing HDE frequency by about 35-54% relative to the climatological mean.  Understanding the effects of sub-seasonal and seasonal atmospheric circulation variability, such as the Silk Road Pattern and Boreal Summer Intraseasonal Oscillation, on HDEs is important to improve HDE predictions over China.</p>

scholarly journals The driving processes of concurrent hot and dry extreme events in China

2020 ◽  
pp. 1-40
Author(s):  
Fangxing Tian ◽  
Nicholas P. Klingaman ◽  
Buwen Dong
Keyword(s):  
Extreme Events ◽  
Southern China ◽  
Eastern China ◽  
Intraseasonal Oscillation ◽  
Silk Road ◽  
Height Anomaly ◽  
Boreal Summer ◽  
Boreal Summer Intraseasonal Oscillation ◽  
Silk Road Pattern ◽  
The Silk Road

AbstractSub-seasonal heatwave-driven concurrent hot and dry extreme events (HDEs) can cause substantial damage to crops, and hence to lives and livelihoods. However, the physical processes that lead to these devastating events are not well-understood. Based on observations and reanalysis data for 1979-2016 over China, we show that HDEs occur preferentially over central and eastern China (CEC) and southern China (SC), with a maximum of 3 events year-1 along the Yangtze Valley. The probability of longer-lived and potentially more damaging HDEs is larger in SC than in CEC. Over SC the key factors of HDEs—positive anomalies of surface air temperature and evapotranspiration, and negative anomalies of soil moisture—begin two pentads before maximising at the peak of the HDEs. These anomalies occur south of a positive height anomaly at 200 hPa, associated with a large-scale subsidence anomaly. The processes over CEC are similar to SC, but the anomalies begin one pentad before the peak. HDE frequency is strongly related to the Silk Road Pattern and the Boreal Summer Intraseasonal Oscillation. Positive phases of the Silk Road Pattern and suppressed phases of the Boreal Summer Intraseasonal Oscillation are associated with positive height anomalies over CEC and SC, increasing HDE frequency by about 35-54% relative to the climatological mean. Understanding the effects of sub-seasonal and seasonal atmospheric circulation variability, such as the Silk Road Pattern and Boreal Summer Intraseasonal Oscillation, on HDEs is important to improve HDE predictions over China.

Cloud and radiative heating profiles associated with the boreal summer intraseasonal oscillation

2017 ◽  
Vol 50 (5-6) ◽  
pp. 1485-1494 ◽  
Author(s):  
Jinwon Kim ◽  
Duane E. Waliser ◽  
Gregory V. Cesana ◽  
Xianan Jiang ◽  
Tristan L’Ecuyer ◽  
...  
Keyword(s):  
Intraseasonal Oscillation ◽  
Radiative Heating ◽  
Boreal Summer ◽  
Boreal Summer Intraseasonal Oscillation ◽  
Heating Profiles

scholarly journals Initiation of Boreal Summer Intraseasonal Oscillation: Dynamic Contribution by Potential Vorticity

2012 ◽  
Vol 140 (6) ◽  
pp. 1748-1760 ◽  
Author(s):  
Kyong-Hwan Seo ◽  
Eun-Ji Song
Keyword(s):  
Potential Vorticity ◽  
Intraseasonal Oscillation ◽  
Vertical Wind Shear ◽  
Boreal Summer ◽  
Dynamical Process ◽  
Initiation Mechanism ◽  
Middle Troposphere ◽  
Boreal Summer Intraseasonal Oscillation ◽  
Low Level ◽  
The Tropics

Abstract Potential vorticity (PV) thinking conceptually connects the upper-level (upper troposphere in the extratropics and middle troposphere for the tropics) dynamical process to the lower-level process. Here, the initiation mechanism of the boreal summer intraseasonal oscillation (BSISO) in the tropics is investigated using PV thinking. The authors demonstrate that the midtropospheric PV anomaly produces a dynamical environment favorable for the BSISO initiation. Under seasonal easterly vertical wind shear, the PV anomaly enhances low-level convergence and upward motion at its western edge. Tropical PV forcing in the middle troposphere produces balanced mass and circulation fields that spread horizontally and vertically so that its effect can reach even the lowest troposphere. The downward influence of the midtropospheric PV forcing is one of the key aspects of the PV thinking. Direct piecewise PV inversions confirm that the anomalous lower-level zonal wind and its convergence necessary for the initiation of BSISO convection do not arise solely from the response to the lower-level PV forcing but from the summed contribution by PV forcing at all levels. About 50% of the low-level circulation variations result from PV forcing from 700 to 450 hPa, with the largest contribution from the 600–650-hPa PV anomalies for the convection initiation region over the western Indian Ocean. The current study is compared with and incorporated into the thermodynamic recharge process and the frictional moisture flux convergence mechanism for the BSISO initiation. This study is the first qualitative application of the PV thinking approach that reveals the BSISO dynamics.

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