Structures and characteristics of the windy atmospheric boundary layer in the South China Sea region during cold surges

2015 ◽  
Vol 32 (6) ◽  
pp. 772-782 ◽  
Author(s):  
Xue-Ling Cheng ◽  
Jian Huang ◽  
Lin Wu ◽  
Qing-Cun Zeng
Keyword(s):  
Boundary Layer ◽  
South China Sea ◽  
Atmospheric Boundary Layer ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Cold Surges

scholarly journals Two Distinct Types of Extratropical Circulation Anomalies Associated with Cold Surges over the South China Sea

2019 ◽  
Vol 32 (16) ◽  
pp. 5069-5084 ◽  
Author(s):  
Bo Pang ◽  
Riyu Lu
Keyword(s):  
South China Sea ◽  
Rossby Wave ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
Cold Surge ◽  
Siberian High ◽  
China Sea ◽  
Wave Trains ◽  
Cold Surges

Abstract This study investigated the extratropical circulation anomalies responsible for cold surges over the South China Sea in winter. The surge events were identified by the intensity of northerly winds over 110°–117.5°E along 15°N at 925 hPa. Two distinct patterns of sea level pressure (SLP) anomalies in East Asia were found to have a crucial role in inducing cold surges over the South China Sea. Accordingly, the cold surge events were classified into two types. The first type of cold surge is characterized by a pair of SLP anomalies with positive and negative ones centered over China and Japan, respectively, whereas the second type of cold surge is characterized by widespread and persistent positive SLP anomalies over East Asia. Furthermore, the first type of cold surge is accompanied by a deepened East Asian trough and precursory Rossby wave trains across the Eurasian continent in the mid- and upper troposphere, but the latter is not. Prior to both types of the cold surges, the Siberian high is significantly intensified. However, diagnosis of the SLP tendency indicates that the intensification is related to different physical processes. In the first type of cold surge, the Rossby wave trains favor negative vorticity advection and cold advection, inducing intensification of the Siberian high. By contrast, in the second type of cold surge, vorticity advection can be ignored due to the lack of Rossby wave trains, and only the lower-tropospheric cold advection induced by anomalous northerly winds, resulting from the anomalous Siberian high, contributes to the further intensification of the Siberian high.

scholarly journals The South China Sea Monsoon Experiment—Boundary Layer Height (SCSMEX-BLH): Experimental Design and Preliminary Results

2015 ◽  
Vol 143 (12) ◽  
pp. 5035-5053 ◽  
Author(s):  
Huijun Huang ◽  
Weikang Mao
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Active Period ◽  
The South ◽  
Layer Height ◽  
China Sea ◽  
Boundary Layer Height

Abstract Knowing the relationship between local convective precipitation and boundary layer processes is critical for forecasting rainstorms. For the South China Sea area, such a forecast is particularly important during the monsoon season. During such a season, the authors examined the boundary layer features at three sites as part of the South China Sea Monsoon Experiment—Boundary Layer Height (SCSMEX-BLH) experiment. The sites are spread from inland to over sea along a 43.4-km line. Here the authors analyze SCSMEX-BLH data from an intensive observing period that includes a convectively suppressed (inactive) period, a period influenced by a tropical storm, and a convectively active monsoon period. Some preliminary findings include the following: 1) The absorption of shortwave radiation over the sea is the primary driver of the land–sea temperature difference. The difference produces a diurnal variation below 400 m, with a warmer surface layer over the coast at night. 2) In the inactive and storm periods, the sensible heat flux is larger than that in the active period, whereas in the active period, the heat flux (primarily latent heat flux) over sea is significant. Also in the active period, the depth of the mixed layer inland is smaller than that in other periods, but the depth on the coast is always higher than that in other periods. 3) In the active period at night, as a monsoon vapor surge advects horizontally over the warm sea surface, a large latent heat flux driven by strong winds aids the growth of marine cumulus, which eventually develop into inland cumulonimbus bringing inland rainfall.

Influence of Siberian Blocking on Long-Lived Cold Surges over the South China Sea

2020 ◽  
Vol 33 (16) ◽  
pp. 6945-6956
Author(s):  
Bo Pang ◽  
Riyu Lu ◽  
Rongcai Ren
Keyword(s):  
South China Sea ◽  
East Asia ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
Sea Level Pressure ◽  
Cold Surge ◽  
China Sea ◽  
Cold Surges ◽  
Extratropical Circulation

AbstractCold surges occur frequently over the South China Sea (SCS) in winter, and most of them last only a few days. However, some cold surge events can persist longer, for instance, more than 5 days. This study focuses on these long-lived cold surge events and investigates the associated extratropical circulation anomalies. The results indicate that long-lived cold surges, characterized as strong northerlies over the SCS, can be triggered by a successive high anomaly center over East Asia. Accompanying this is an anomalously extensive and quasi-stationary anticyclone over Siberia in the midtroposphere, hinting at a more frequent occurrence of Siberian blocking. Further analyses reveal that the blocking frequency is indeed significantly high over 90°–150°E from day −4 to day +2 relative to the onset of long-lived cold surge events. Furthermore, there exist significant correlations between the leading occurrence of Siberian blocking and the sea level pressure (SLP) anomalies over East Asia, which are directly related to long-lived cold surges. The intensification of the high SLP anomaly over East Asia is found to mainly result from cold advection induced by the anomalous northerly winds along the southeastern edge of the Siberian blocking.

scholarly journals Aircraft Observations of Tropical Cyclone Boundary Layer Turbulence over the South China Sea

2019 ◽  
Vol 76 (12) ◽  
pp. 3773-3783 ◽  
Author(s):  
N. Sparks ◽  
K. K. Hon ◽  
P. W. Chan ◽  
S. Wang ◽  
J. C. L. Chan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
South China Sea ◽  
South China ◽  
Inner Core ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Boundary Layer Turbulence ◽  
Aircraft Observations

Abstract There have been no high-frequency aircraft observations of tropical cyclone (TC) eyewall boundary layer turbulence since two flights into Atlantic hurricanes in the 1980s. We present an analysis of the first TC boundary layer flight observations in the South China Sea by the Hong Kong Observatory comprising four eyewall penetrations. We derive the vertical flux of momentum and vertical momentum diffusivity from observed turbulence parameters. We observe negative (upward) vertical fluxes of tangential momentum near the eyewall consistent with a jet below the flight level near the radius of maximum wind. Our observations of vertical momentum diffusivity support a superlinear relationship between diffusivity and wind speed at the high wind speeds in the inner-core of TCs (power-law exponent of 1.73 ± 0.20) while the few existing boundary layer hurricane observations in the North Atlantic suggest a more linear relationship.

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