Anomaly-based synoptic analysis and model product application for 2020 summer southern China rainfall events

2021 ◽  
Vol 258 ◽  
pp. 105631
Author(s):  
Weihong Qian ◽  
Yang Ai ◽  
Jeremy Cheuk-Hin Leung ◽  
Banglin Zhang
Keyword(s):  
Southern China ◽  
Rainfall Events ◽  
Synoptic Analysis ◽  
Product Application

scholarly journals Mineral leaching chemicals transport with runoff and sediment from severely eroded rare earth tailings in southern China

2017 ◽  
Author(s):  
Huizhong Lu ◽  
Longxi Cao ◽  
Yin Liang ◽  
Jiuqin Yuan ◽  
Yayun Zhu ◽  
...  
Keyword(s):  
Rare Earth ◽  
Southern China ◽  
Transport Processes ◽  
Clear Trend ◽  
Rainfall Events ◽  
Transport Distance ◽  
Sediment Deposits ◽  
Rare Earth Tailings ◽  
Positive Correlations ◽  
Mineral Leaching

Abstract. Rare earth mining has led to severe soil erosion in southern China. Furthermore, the presence of the mineral leaching chemical ammonium sulfate in runoff and sediment poses a serious environmental threat to downstream water bodies. To study the transport characteristics of mineral leaching chemicals, soil on rare earth tailings was sampled in different positions, and runoff and sediment samples were collected along flow routes during three typical rainfall events. The results demonstrated that the NH4+ contents in the surface sediment deposits increased from the top of the heap (6.56 mg/kg) to the gully (8.23 mg/kg) and outside the tailing heap (13.03 mg/kg). The contents of SO42− in the different locations of the tailing heaps ranged from 27.71 to 40.33 mg/kg. During typical rainfall events, the absorbed NH4+ concentrations (2.05, 1.26 mg/L) in runoff were higher than the dissolved concentrations (0.93, 1.04 mg/L), while the absorbed SO42− concentrations (2.87, 1.92 mg/L) were lower than the dissolved concentrations (6.55, 7.51 mg/L). The dissolved NH4+ and SO42− concentrations in runoff displayed an exponentially decreasing tendency with increasing transport distance (Y=1.02*exp(-0.00312X), Y=3.34*exp(-0.0185X)). No clear trend with increasing distance was observed for the absorbed NH4+ and SO42− contents in transported sediment. The NH4+ and SO42− contents had positive correlations with the silt and clay ratio in transported sediment but negative correlations with the sand ratio. These results provide a better understanding of the transport processes and can be used to develop equations to predict the transport of mineral leaching chemicals in rare earth tailings.

scholarly journals Impact of 3DVAR Data Assimilation on the Prediction of Heavy Rainfall over Southern China

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Tuanjie Hou ◽  
Fanyou Kong ◽  
Xunlai Chen ◽  
Hengchi Lei
Keyword(s):  
Data Assimilation ◽  
Heavy Rainfall ◽  
Positive Impact ◽  
Southern China ◽  
Precipitation Forecast ◽  
Radiosonde Data ◽  
Near Surface ◽  
Rainfall Events ◽  
Forecasting System ◽  
The Impact

This study examines the impact of three-dimensional variational data assimilation (3DVAR) on the prediction of two heavy rainfall events over Southern China by using a real-time storm-scale forecasting system. Initialized from the European Centre for Medium-Range Weather Forecasts (ECMWF) high-resolution data, the forecasting system is characterized by combining the Advanced Research Weather Research and Forecasting (WRF-ARW) model and the Advanced Regional Prediction System (ARPS) 3DVAR package. Observations from Doppler radars, surface Automatic Weather Station (AWS) network, and radiosondes are used in the experiments to evaluate the impact of data assimilation on short-term quantitative precipitation forecast (QPF) skill. Results suggest that extrasurface AWS data assimilation has slight but general positive impact on rainfall location forecasts. Surface AWS data also improve model results of near-surface variables. Radiosonde data assimilation improves the QPF skill by improving rainfall position accuracy and reducing rainfall overprediction. Compared with radar data, the overall impact of additional surface and radiosonde data is smaller and is reflected primarily in reducing rainfall overestimation. The assimilation of all radar, surface, and radiosonde data has a more positive impact on the forecast skill than the assimilation of either type of data only for the two rainfall events.

scholarly journals The Southern China Monsoon Rainfall Experiment (SCMREX)

2017 ◽  
Vol 98 (5) ◽  
pp. 999-1013 ◽  
Author(s):  
Yali Luo ◽  
Renhe Zhang ◽  
Qilin Wan ◽  
Bin Wang ◽  
Wai Kin Wong ◽  
...  
Keyword(s):  
Rainy Season ◽  
Heavy Rainfall ◽  
Monsoon Rainfall ◽  
Southern China ◽  
Precipitation Forecast ◽  
Ensemble Prediction ◽  
Rainfall Events ◽  
The World ◽  
Field Campaigns ◽  
Heavy Rainfall Events

Abstract During the presummer rainy season (April–June), southern China often experiences frequent occurrences of extreme rainfall, leading to severe flooding and inundations. To expedite the efforts in improving the quantitative precipitation forecast (QPF) of the presummer rainy season rainfall, the China Meteorological Administration (CMA) initiated a nationally coordinated research project, namely, the Southern China Monsoon Rainfall Experiment (SCMREX) that was endorsed by the World Meteorological Organization (WMO) as a research and development project (RDP) of the World Weather Research Programme (WWRP). The SCMREX RDP (2013–18) consists of four major components: field campaign, database management, studies on physical mechanisms of heavy rainfall events, and convection-permitting numerical experiments including impact of data assimilation, evaluation/improvement of model physics, and ensemble prediction. The pilot field campaigns were carried out from early May to mid-June of 2013–15. This paper: i) describes the scientific objectives, pilot field campaigns, and data sharing of SCMREX; ii) provides an overview of heavy rainfall events during the SCMREX-2014 intensive observing period; and iii) presents examples of preliminary research results and explains future research opportunities.

scholarly journals Heavy Rainfall Events in Southern China Associated with Tropical Cyclones in the Bay of Bengal: A Case Study

Atmosphere ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 574
Author(s):  
Junpeng Yuan ◽  
Jiao Lü ◽  
Dian Feng ◽  
Mengni Mao ◽  
Tao Feng ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Bay Of Bengal ◽  
Heavy Rainfall ◽  
Southern China ◽  
Southwestern China ◽  
Rain Event ◽  
Rainfall Events ◽  
Main Contributor ◽  
Heavy Rainfall Events

We use a case study to show that a continuous heavy rainfall process in southern China was closely related to tropical cyclone activity in the Bay of Bengal. The continuous heavy rainfall that occurred in southern China on 11–13 May 2002 can be considered as two different processes. The first process, referred to as a predecessor rain event, occurred over southwestern China before landfall of the tropical cyclone. The second process occurred after dissipation of the tropical cyclone when its remnant caused heavy rainfall that expanded from southwestern China to the middle to lower reaches of the Yangtze–Huaihe river basin. Both of the heavy rainfall processes were closely related to the transport of warm, moist air associated with a tropical cyclone originating over the Bay of Bengal, but the mechanisms in the two processes were quite different. Low-level orographic forcing was the main contributor to the predecessor rain event, whereas baroclinic frontogenesis induced by thermal advection was the main contributor to the tropical cyclone remnant event. Both heavy rainfall events occurred beneath the equatorial entrance of the upper level East Asian subtropical jet.

Why Nocturnal Long-Duration Rainfall Presents an Eastward-Delayed Diurnal Phase of Rainfall down the Yangtze River Valley

2010 ◽  
Vol 23 (4) ◽  
pp. 905-917 ◽  
Author(s):  
Haoming Chen ◽  
Rucong Yu ◽  
Jian Li ◽  
Weihua Yuan ◽  
Tianjun Zhou
Keyword(s):  
Yangtze River ◽  
Large Scale ◽  
Southern China ◽  
Summer Rainfall ◽  
Early Morning ◽  
The Tibetan Plateau ◽  
The Yangtze River ◽  
Rainfall Events ◽  
Low Level ◽  
Long Duration

Abstract Hourly observational records and 6-hourly reanalysis data were used to investigate the influences of large-scale forcings on the diurnal variation of summer rainfall along the Yangtze River (YR). The results show that long-duration (more than six hours) rainfall events dominate the summer rainfall along the YR. These events tend to start during the night and to peak after several hours of development. The eastward-delayed initiation of the nocturnal long-duration rainfall events is thought to be due to the diurnal clockwise rotation of the low-tropospheric circulation, especially the accelerated nocturnal southwesterlies. In the early evening, the anomalous easterly flow toward the Tibetan Plateau (TP) causes low-level convergence over the Plateau’s eastern slope that induces the formation of rainfall in the upper YR valley. The anomalous wind sequentially rotates clockwise to a southerly flow at midnight and accelerates the meridional wind in the middle valley, resulting in the initiation of rainfall between 2300 and 0300 LST. In the early morning, the accelerated southwesterlies in southern China, when combined with decelerated winds in the north of the YR, causes a strong convergence along the YR and contributes to the early morning rainfall in the lower valley. Furthermore, the development of the convection systems is suppressed in the afternoon by the mid- and low-level warm advection downstream from the TP. This helps explain why long-duration events do not typically start in the afternoon in the upper YR valley.

Causes of Interdecadal Increase in the Intraseasonal Rainfall Variability over Southern China around the Early 1990s

2020 ◽  
Vol 33 (21) ◽  
pp. 9481-9496
Author(s):  
Yifeng Cheng ◽  
Lu Wang ◽  
Tim Li
Keyword(s):  
Southern China ◽  
Rainfall Variability ◽  
Lower Troposphere ◽  
Summer Rainfall ◽  
Dominant Factor ◽  
Interdecadal Change ◽  
Rainfall Events ◽  
Southerly Wind ◽  
Budget Analysis ◽  
Northward Propagation

AbstractThe southern China (SC) summer rainfall exhibits prominent intraseasonal variability, which exhibits a significant increase in the early 1990s with the turning point at 1993. The SC intraseasonal rainfall events could be divided into three categories according to different propagations, including the southward-propagating (SP) events, the northwestward-propagating (NWP) events, and the northward-propagating (NP) events. This study explores the causes of the observed interdecadal increase in the intraseasonal rainfall variability over SC by comparing the SC intraseasonal rainfall events of each category between the former decadal period (P1) and the later decadal period (P2). The result indicates that such interdecadal change is due to the more frequent NP events coming from the South China Sea (SCS). Based on the moisture and vorticity budget analysis, it is revealed that the summer mean southerly wind in the middle to lower troposphere is the dominant factor of the northward propagation over the SCS, as it could induce positive meridional moisture and vorticity advection anomalies ahead of the convection. A marked interdecadal enhancement of the summer mean southerly wind over the SCS is the cause of more frequent occurrence of NP events over SC, as it provides more favorable conditions for the northward propagation. The change of the atmospheric instability over the SCS where the NP convection perturbation originates was also investigated, but no significant change was found.

scholarly journals Large-Scale Environmental Conditions Related to Midsummer Extreme Rainfall Events around Japan in the TRMM Region

2018 ◽  
Vol 31 (17) ◽  
pp. 6933-6945 ◽  
Author(s):  
Atsushi Hamada ◽  
Yukari N. Takayabu
Keyword(s):  
Extreme Events ◽  
Environmental Conditions ◽  
Large Scale ◽  
Southern China ◽  
Extreme Rainfall ◽  
Extreme Rainfall Events ◽  
Near Surface ◽  
Rainfall Events ◽  
Precipitation Characteristics ◽  
Large Scale Flow

The precipitation characteristics of extreme events in August determined from 13 years of satellite data around Japan in the TRMM observation region and their relationship with large-scale environmental conditions are examined. Two types of extreme events, extreme rainfall and extreme convective events, are defined in each analysis grid box using maximum near-surface rainfall and maximum 40-dB Z echo-top height in each event, respectively. There are clear differences in precipitation characteristics between the two types of extreme events. Extreme rainfall events are more organized precipitation systems than the extreme convective events, with relatively lower echo-top heights and very low lightning activity. There are also clear differences in the related environmental conditions, where the environments related to the extreme rainfall events are somewhat convectively stable and very humid in almost the entire troposphere. These facts are consistent with our previous studies and reinforce the importance of warm-rain processes in extremely intense precipitation productions. The environments related to the extreme rainfall events exhibit a zonally extended moist anomaly in the free troposphere from southern China to the east of Japan, indicating that the excessive moisture transported from the west by a large-scale flow may partially play a role in producing environmental conditions favorable for extreme rainfall. On the other hand, the environments related to extreme convective events are not associated with free-tropospheric moisture inflow. The relationships with the tropical cyclones and upper-tropospheric dynamical fields are also examined, and are found to be clearly different between the extreme rainfall events and extreme convective events.

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