scholarly journals Relative Contributions of Tropical and Mid-Latitude Signals on Intraseasonal Precipitation Anomalies Over South China in Boreal Winter

2022 ◽  
Author(s):  
Lu Wang ◽  
Jie Jiang ◽  
Tim Li
Keyword(s):  
South China ◽  
Southern China ◽  
Wave Train ◽  
Intraseasonal Oscillation ◽  
Lower Troposphere ◽  
Low Pressure ◽  
Boreal Winter ◽  
Pressure System ◽  
Pressure Anomaly ◽  
Precipitation Anomalies

Abstract The southern China (SC) exhibits a strong intraseasonal precipitation variability in boreal winter, but so far the relative contributions of the tropical Madden-Julian Oscillation (MJO) and the mid-latitude intraseasonal oscillation (ISO) is unclear. This issue is addressed through a cluster analysis. The result shows that 53% of strong intraseasonal precipitation events are unrelated to the MJO. They are caused by southward propagation of a low-pressure anomaly in the lower troposphere from higher latitudes. Southerly anomalies associated with the low-pressure system transport high mean moisture from South China Sea, leading to moisture accumulation over SC. 47% of the events are accompanied by the MJO, and they can be further divided into two groups: one with enhanced MJO convection over the eastern Indian Ocean (termed as IO group), and the other over the Maritime Continent (termed as MC group). For the IO group, the SC precipitation is triggered by low-level southerly anomalies associated with an anomalous anticyclone over the western North Pacific (WNP) in association with suppressed MJO convection in situ, as well as the upper-tropospheric divergence related to a wave train excited from the MJO convection. For the MC group, both the upper-tropospheric wave train related to MJO and the southward propagation of low-pressure anomaly from higher latitudes in the lower troposphere contribute to trigger the SC precipitation.

scholarly journals Synoptic perspectives on pollutant transport patterns observed by satellites over East Asia: Case studies with a conceptual model

2016 ◽  
Author(s):  
Hyun Cheol Kim ◽  
Soontae Kim ◽  
Seok-Woo Son ◽  
Pius Lee ◽  
Chun-Sil Jin ◽  
...  
Keyword(s):  
High Pressure ◽  
East Asia ◽  
Southern China ◽  
Low Pressure ◽  
Pressure System ◽  
Weather Patterns ◽  
High Pressure System ◽  
Synoptic Weather ◽  
Low Pressure System ◽  
Transport Patterns

Abstract. We demonstrate that daily pollutant transport patterns in East Asia are visible from satellite images when inspected with corresponding synoptic weather analyses. Transport pathways of air pollutants in East Asia are investigated using satellite observations, surface weather charts, and chemical-transport model simulations. It is found that during cool season (fall to spring), pollutant transports in East Asia are largely determined by synoptic weather patterns associated with high pressure system over southern China, which is extended from the Siberia High, and low pressure system over Manchuria, which is initiated by Altai-Sayan cyclogenesis. Based on the relative location and strength of these weather systems, three types of synoptic weather patterns that may contribute to pollutants transport in East Asia, especially in China and Korea, are identified: i.e., (1) a strengthening of the Siberian High and its southeastward propagation; (2) a high-pressure system over southern China followed by a frontal passage associated with a northern low-pressure system; and (3) a stagnant high-pressure system over southern China. For all three patterns, the high-pressure system in southern China is essential for the development of regional air pollution, while frontal activities associated with low-pressure system provide a forcing mechanism to transport those pollutants eastward or southeastward. Observed and simulated surface PM distributions show good agreement in both aerosol optical depth and NO2 column density further implying that anthropogenic emissions also contribute to regional events of high surface PM concentrations. It is argued that the quasi-periodic migration of synoptic weather systems in East Asia works as an efficient pump of pollutants; i.e., regional air pollutions developed under high-pressure systems are transported downstream by low-pressure systems.

Impact of Boreal Autumn Antarctic Oscillation on Winter Wet and Cold Weather in East Asia

2021 ◽  
Author(s):  
Zhengxuan Yuan ◽  
Jun Qin ◽  
Shuanglin Li ◽  
Sijing Huang ◽  
Yassin Mbululo ◽  
...  
Keyword(s):  
Southern China ◽  
Wave Train ◽  
Yangtze River Basin ◽  
Air Flow ◽  
Lower Troposphere ◽  
Dominant Mode ◽  
Cold Weather ◽  
Occurrence Rate ◽  
Antarctic Oscillation ◽  
Quasi Biennial Oscillation

<p>The Antarctic Oscillation (AAO) is the dominant mode of the southern extratropical atmospheric mass variability which has potential influences on the Northern Hemisphere (NH). This study reveals a significantly negative correlation between the September-October (SO) AAO index and the occurrence rate of following January-February (JF) wet and cold weather in the Middle and Lower Reaches of Yangtze River Basin (MLRY) in China. The latter is quantified by a Precipitation-Temperature (PT) Index. JF PT is modulated by both northerly air flow in the lower troposphere and southerly air flow in the lower-middle troposphere. The SO AAO stimulates Southern Ocean Dipole (SOD) pattern-like SST anomalies, which induces a North Atlantic Oscillation (NAO)-like atmospheric response in the following JF through ocean-air interaction. As for the northerly flow, the JF NAO-like pattern triggers an eastward propagating wave train, influencing the intensity of East Asian Winter Monsoon (EAWM) and subsequently the northerly cold flow to MLRY. As for southerly flow, the variation of JF SOD regulates the local meridional cell, in turn modulating the Middle East Jet Stream (MEJS) along with the NAO-like pattern, influencing the intensity of precipitation and the wet and warm flow over Southern China and the adjacent regions. In addition to the tropospheric processes, the stratospheric Quasi Biennial Oscillation (QBO) serves as the ‘bridge’ for linking SOD to NH climate, inducing the JF PT response to SOD SST. To summarize, SO AAO affects the JF PT in MLRY by modulating both cold-dry northerly air flow and warm-wet southerly air flow through ocean-atmosphere interactions and stratospheric pathway.</p>

scholarly journals The Quasi-Biweekly Oscillation of Winter Precipitation Associated with ENSO over Southern China

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 406 ◽  
Author(s):  
Qiaoyu Tong ◽  
Suxiang Yao
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern China ◽  
Low Pressure ◽  
Winter Precipitation ◽  
Precipitation Variability ◽  
Pressure System ◽  
Vorticity Advection ◽  
Low Pressure System ◽  
Low Pressure Systems

Using ERA-interim Reanalysis data and observational data, the intraseasonal oscillation of the winter rainfall in southern China is studied. The mean square deviation of daily precipitation is used to express precipitation variability, and winter precipitation variability over southern China is determined to be highly correlated with sea surface temperature (SST) in central and eastern tropical Pacific; the dominant period of the precipitation is 10–30 days, which reflects quasi-biweekly oscillation. Examination of 1000 hPa geopotential height suggests that key low-pressure systems affecting the intraseasonal precipitation come from Lake Baikal, but with different travel paths. In El Niño years, key low-pressure systems converge with other low-pressure systems and move southeastward until reaching South China, while in La Niña years, only one low-pressure system can reach southern China. Meanwhile, the explosive development of the low-pressure system is mainly caused by the joint effects of thermal advection and vorticity advection in El Niño, and only vorticity advection accounted for the dominant status in La Niña. Multiscale analysis shows that the meridional distribution of intraseasonal circulation plays an important role on the thermal transmission and brings strong warm advection from low latitudes to high latitudes in El Niño.

scholarly journals A Precipitation-Based Index for Tropical Intraseasonal Oscillations

2020 ◽  
Vol 33 (3) ◽  
pp. 805-823 ◽  
Author(s):  
Shuguang Wang
Keyword(s):  
Real Time ◽  
Decadal Variability ◽  
Intraseasonal Oscillation ◽  
Longwave Radiation ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Eof Analysis ◽  
Intraseasonal Oscillations ◽  
Precipitation Anomalies ◽  
Tropical Intraseasonal Oscillations

AbstractCharacteristic patterns of precipitation-associated tropical intraseasonal oscillations, including the Madden–Julian oscillation (MJO) and boreal summer intraseasonal oscillation (BSISO), are identified using local empirical orthogonal function (EOF) analysis of the Tropical Rainfall Measuring Mission (TRMM) precipitation data as a function of the day of the year. The explained variances of the EOF analysis show two peaks across the year: one in the middle of the boreal winter corresponding to the MJO and the other in the middle of summer corresponding to the BSISO. Comparing the fractional variance indicates that the BSISO is more coherent than the MJO during the TRMM period. Similar EOF analyses with the outgoing longwave radiation (OLR) confirm this result and indicate that the BSISO is less coherent before the TRMM era (1979–98). In contrast, the MJO exhibits much less decadal variability. A precipitation-based index for tropical intraseasonal oscillation (PII) is derived by projecting bandpass-filtered precipitation anomalies to the two leading EOFs as a function of day of the year. A real-time version that approximates the PII is further developed using precipitation anomalies without any bandpass filtering. It is further shown that this real-time PII index may be used to diagnose precipitation in the subseasonal forecasts.

scholarly journals Dynamics of Interannual Variability in Summer Precipitation over East Asia*

2011 ◽  
Vol 24 (20) ◽  
pp. 5435-5453 ◽  
Author(s):  
Yu Kosaka ◽  
Shang-Ping Xie ◽  
Hisashi Nakamura
Keyword(s):  
East Asia ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Wave Train ◽  
Polar Front ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Temperature Advection ◽  
Svd Analysis ◽  
Precipitation Anomalies

Abstract The summertime mei-yu–baiu rainband over East Asia displays considerable interannual variability. A singular value decomposition (SVD) analysis for interannual variability reveals that precipitation anomalies over the mei-yu–baiu region are accompanied by in situ anomalies of midtropospheric horizontal temperature advection. Anomalous warm (cool) advection causes increased (decreased) mei-yu–baiu precipitation locally by inducing adiabatic ascent (descent). The anomalous precipitation acts to reinforce the vertical motion, forming a feedback system. By this mechanism, the remotely forced anomalous atmospheric circulation can induce changes in mei-yu–baiu precipitation. The quasi-stationary precipitation anomalies induced by this mechanism are partially offset by transient eddies. The SVD analysis also reveals the association of mei-yu–baiu precipitation anomalies with several teleconnection patterns, suggesting remote induction mechanisms. The Pacific–Japan (PJ) teleconnection pattern, which is associated with anomalous convection over the tropical western North Pacific, contributes to mei-yu–baiu precipitation variability throughout the boreal summer. The PJ pattern mediates influences of the El Niño–Southern Oscillation in preceding boreal winter on mei-yu–baiu precipitation. In early summer, the leading covariability pattern between precipitation and temperature advection also features the Silk Road pattern—a wave train along the summertime Asian jet—and another wave train pattern to the north along the polar-front jet that often leads to the development of the surface Okhotsk high.

scholarly journals Subseasonal Variability of Precipitation in China during Boreal Winter

2015 ◽  
Vol 28 (16) ◽  
pp. 6548-6559 ◽  
Author(s):  
Yonghong Yao ◽  
Hai Lin ◽  
Qigang Wu
Keyword(s):  
South China ◽  
Wave Train ◽  
Yangtze River Basin ◽  
Daily Rainfall ◽  
Precipitation Variability ◽  
Tropical Convection ◽  
Boreal Winter ◽  
The North ◽  
Subseasonal Variability ◽  
Cold Air Outbreak

Abstract Using pentad data of the Northern Hemisphere extended winter (November–March) from 1979 to 2012 derived from the daily rainfall of the National Meteorological Information Center of China, subseasonal variability of precipitation in China is analyzed. The two dominant modes of subseasonal variability are identified with an empirical orthogonal function (EOF) analysis. The first EOF mode (EOF1) is characterized by a monopole in South China, whereas the second EOF mode (EOF2) has a meridional dipole structure with opposite precipitation anomalies over the Yangtze River basin and the coastal area of South China. These two modes tend to have a phase shift to each other in both space and time, indicating that part of their variability represents a southward-propagating pattern. The subseasonal variability is decomposed into two components: one related to the Madden–Julian oscillation (MJO) and the other independent of MJO. It is found that the MJO contributes to about 10% of the precipitation variability in South China. EOF1 is associated with MJO phase 3, corresponding to enhanced equatorial convection in the Indian Ocean and depressed convection in the western Pacific, while EOF2 is related to MJO phase 5 when the enhanced tropical convection moves to the Maritime Continent region. Subseasonal precipitation variability in China that is independent of the MJO is especially affected by processes including tropical convection variability and the “cold surge” phenomenon or the development of a Siberian high and cold-air outbreak in East Asia associated with a wave train from the North Atlantic.

scholarly journals Increasing persistent hazes in Beijing: potential impacts of weakening East Asian Winter Monsoons associated with northwestern Pacific SST trend since 1900

2017 ◽  
Author(s):  
Lin Pei ◽  
Zhongwei Yan ◽  
Zhaobin Sun ◽  
Shiguang Miao ◽  
Yao Yao
Keyword(s):  
Large Scale ◽  
North China ◽  
East Asian ◽  
Lower Troposphere ◽  
Northwestern Pacific ◽  
Boreal Winter ◽  
Pressure System ◽  
Increasing Trend ◽  
Meridional Winds ◽  
Haze Days

Abstract. This paper analyzes the variations of persistent haze days in boreal winter in Beijing and　demonstrates a significant increasing trend with increasing probability of the persistent haze　events (PHEs) during 1980–2016. The atmospheric conditions favorable for the increasing　PHEs include reduced surface meridional winds and weakened East Asian Trough in the mid-troposphere. These conditions indicate a weakening East Asian Winter Monsoon (EAWM)　system, which is then found to be associated with an anomalous warm and high-pressure system　in the mid-lower troposphere over the northwestern Pacific. We proposed a practical circulation　indicator using the anomalous southerly winds at 850 hPa over North China. The increasing　occurrence of the persistent haze days in Beijing is closely related with increasing frequencies　of unusual persistent southerly episodes in recent decades. Over the past centennial period 1900–2009, the anomalous meridional winds at 850 hPa in North China were positively　correlated with the sea surface temperature anomalies over the northwestern Pacific. Based on the present results, we outline an observation-based mechanism highlighting the role of large　scale climate warming on the increasing trend of PHEs in Beijing.

scholarly journals Simulated coordinated impacts of the NAO and El Niño on aerosol concentrations over eastern China

2019 ◽  
Author(s):  
Juan Feng ◽  
Jianping Li ◽  
Hong Liao ◽  
Jianlei Zhu
Keyword(s):  
South China ◽  
El Niño ◽  
Transport Model ◽  
El Nino ◽  
Wave Train ◽  
Eastern China ◽  
Central China ◽  
Boreal Winter ◽  
Enso Events ◽  
The Impact

Abstract. The high aerosol concentrations (AC) over eastern China have attracted attention from both science and society. Based on the simulations of a chemical transport model using a fixed emissions level, the possible role of the previous autumn North Atlantic Oscillation (NAO) combined with the simultaneous El Niño–South Oscillation (ENSO) on the boreal winter AC over eastern China is investigated. We find that the NAO only manifests its negative impacts on the AC during its negative phase over central China, and a significant positive influence on the distribution of AC is observed over south China only during the warm events of ENSO. The impact of the previous NAO on the AC occurs via an anomalous sea surface temperature tripole pattern by which a teleconnection wave train is induced that results in anomalous convergence over central China. In contrast, the occurrence of ENSO events may induce an anomalous shift in the western Pacific subtropical high and result in anomalous southwesterlies over south China. The anomalous circulations associated with a negative NAO and El Niño are not favorable for the transport of AC and correspond to worsening air conditions. The results highlight that the combined effects of tropical and extratropical systems play considerable role in affecting the boreal winter AC over eastern China.

Extratropical Forcing of Submonthly Variations of Rainfall in Vietnam

2019 ◽  
Vol 32 (8) ◽  
pp. 2329-2348 ◽  
Author(s):  
Bui Minh Tuan
Keyword(s):  
Heavy Rainfall ◽  
Wave Train ◽  
Intraseasonal Oscillation ◽  
Power Spectral Analysis ◽  
Red River Delta ◽  
The North ◽  
Power Spectral ◽  
Precipitation Anomalies ◽  
Tropical Depressions ◽  
Extratropical Forcing

Abstract An EOF analysis is applied to high-resolution Vietnam Gridded Precipitation anomalies to support the notion that the characteristics of intraseasonal oscillation (ISO) of rainfall in Vietnam are distinct from location to location and highly affected by topography. Power spectral analysis reveals that the ISO of rainfall in Vietnam is dominated by submonthly-scale ISO (SISO), which is most active in September–October. The rainfall SISO shows remarkable relationships with heavy rainfall days in the Red River Delta and Mid-Central and Central Highlands but relatively weak correlations with heavy rainfall days in the Northeast and Southern Plain. A composite technique applied to filtered OLR and ERA-Interim shows that the first four principal components (PCs) of the rainfall SISO involve four different processes that closely relate to extratropical systems. The rainfall SISO in the PC1 is governed by interaction between the pressure surge induced by the submonthly amplifications of the Siberian high and tropical depressions (TDs). Rainfall SISO in PC2 is modulated by the convergence of the southward excursion of the polar air mass and TD-type waves. Rainfall SISO in PC3 is generated by the quasigeostrophic lifting of the extratropical wave train associated with TD-type waves. The effect of upstream development of the wave train from the North Pacific and TD-type wave is the key process inducing the rainfall SISO in PC4.

Sign in / Sign up

Export Citation Format

Share Document