scholarly journals Diurnal variations of southerly monsoon surge and their impacts on East Asian summer rainfall

2021 ◽  
pp. 1-49
Author(s):  
Biqi Liu ◽  
Guixing Chen ◽  
Wenxin Zeng ◽  
Lanqiang Bai ◽  
Huiling Qin
Keyword(s):  
Water Vapor ◽  
East Asia ◽  
Large Scale ◽  
Western Pacific Subtropical High ◽  
Summer Rainfall ◽  
Diurnal Variations ◽  
Water Vapor Transport ◽  
Diurnal Cycles ◽  
The North ◽  
Rain Events

AbstractMonsoon southerlies can be particularly active for days and produce substantial rainfall over East Asia. These multiday episodes of southerly monsoon surge may exhibit distinct diurnal variations due to regional forcings under given large-scale conditions. This study categorizes the southerly surges into two types with different wind diurnal variations to clarify their influence on rainfall over East Asia. In the summer of 1998–2019, there are 63 episodes of southerly surge with large wind diurnal cycles and 55 episodes with small diurnal cycles. The first type of southerly surges usually occurs with anomalous low-level warming over southeastern China related to the westward extension of the western Pacific subtropical high. The second type of southerly surges instead occurs with anomalous cooling due to the deepened midlatitude trough. They thus represent the different mechanisms downscaling from large-scale conditions to regional diurnal forcings. After the onset of the first type, the intensified monsoon southerlies at night lead to the northward displacement of large-scale ascent and northward water vapor transport with warm moist energy. The monsoon rainband tends to move to the north of 35°N with a robust response in precipitation systems, especially in the meso-α-scale rain events from midnight to morning. As a comparison, the rainband stays at 30°–35°N after the onset of the second type when the strengthened large-scale ascent and water vapor convergence are located relatively south. These differences between the two types of southerly monsoon surges highlight that the multiday large-scale conditions interact with sub-daily regional forcings and greatly regulate the detailed evolution of summer rainband over East Asia.

scholarly journals Why the Increasing Trend of Summer Rainfall over North China Has Halted since the Mid-1990s

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Haiwen Liu ◽  
Jiarui Miao ◽  
Kaijun Wu ◽  
Mengxing Du ◽  
Yuxiang Zhu ◽  
...  
Keyword(s):  
Water Vapor ◽  
North China ◽  
Asian Summer Monsoon ◽  
Summer Rainfall ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Precipitation Trend ◽  
The North ◽  
Asian Summer ◽  
Upper Level

Previous studies indicate that the summer (July-August) rainfall over North China has decreased since the mid-1970s due to the weakening of East Asian summer monsoon (EASM). However, this study firstly discovers the new evidences that the summer rainfall over North China had a significant increasing tendency during 1979–1996; since 1997, this increasing tendency has halted while more summer droughts occurred over North China. One important cause for the halted increasing tendency over North China is the interdecadal decrease of the westerly water vapor transport during 1997–2016 in addition to the weakened EASM. The decrease of the westerly water vapor transport during 1997–2016 was due to the interdecadal warming over Lake Baikal. The interdecadal warming in the upper troposphere at 200 hPa forced the weakening of the upper-level zonal winds since 1997, which resulted in the anomalous descending flow over the north side of North China and the halted precipitation trend in North China.

scholarly journals Extreme Floods in the Eastern Part of Europe: Large-Scale Drivers and Associated Impacts

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1122
Author(s):  
Monica Ionita ◽  
Viorica Nagavciuc
Keyword(s):  
Water Vapor ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Flood Events ◽  
Rainfall Events ◽  
Catchment Areas ◽  
Large Scale Atmospheric Circulation ◽  
Heavy Rainfall Events

The role of the large-scale atmospheric circulation in producing heavy rainfall events and floods in the eastern part of Europe, with a special focus on the Siret and Prut catchment areas (Romania), is analyzed in this study. Moreover, a detailed analysis of the socio-economic impacts of the most extreme flood events (e.g., July 2008, June–July 2010, and June 2020) is given. Analysis of the largest flood events indicates that the flood peaks have been preceded up to 6 days in advance by intrusions of high Potential Vorticity (PV) anomalies toward the southeastern part of Europe, persistent cut-off lows over the analyzed region, and increased water vapor transport over the catchment areas of Siret and Prut Rivers. The vertically integrated water vapor transport prior to the flood peak exceeds 300 kg m−1 s−1, leading to heavy rainfall events. We also show that the implementation of the Flood Management Plan in Romania had positive results during the 2020 flood event compared with the other flood events, when the authorities took several precaution measurements that mitigated in a better way the socio-economic impact and risks of the flood event. The results presented in this study offer new insights regarding the importance of large-scale atmospheric circulation and water vapor transport as drivers of extreme flooding in the eastern part of Europe and could lead to a better flood forecast and flood risk management.

Modulation of coupled modes of Tibetan Plateau heating and Indian Summer Monsoon on summer rainfall over Central Asia

2021 ◽  
pp. 1-54
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Central Asia ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Diabatic Heating ◽  
Summer Rainfall ◽  
Hadley Cell ◽  
Vapor Transport ◽  
Water Vapor Transport

Abstract It has been suggested that summer rainfall over Central Asia (CA) is significantly correlated with the summer thermal distribution of the Tibetan Plateau (TP) and the Indian summer monsoon (ISM). However, relatively few studies have investigated their synergistic effects of different distribution. This study documents the significant correlations between precipitation in CA and the diabatic heating of TP and the ISM based on the results of statistical analysis and numerical simulation. Precipitation in CA is is dominated by two water vapor transport branches from the south which are related to the two primary modes of anomalous diabatic heating distribution related to the TP and ISM precipitation, that is, the “+-” dipole mode in the southeastern TP and the Indian subcontinent (IS), and the “+-+” tripole mode in the southeastern TP, the IS, and southern India. Both modes exhibit obvious mid-latitude Silk Road pattern (SRP) wave trains with cyclone anomalies over CA, but with different transient and stationary eddies over south Asia. The different locations of anomalous anticyclones over India govern two water vapor transport branches to CA, which are from the Arabian Sea and the Bay of Bengal. The water vapor flux climbs while being transported northward and can be transported to CA with the cooperation of cyclonic circulation. The convergent water vapor and ascending motion caused by cyclonic anomalies favor the precipitation in CA. Further analysis corroborates the negative South Indian Ocean Dipole (NSIOD) in February could affect the tripole mode distribution of TP heating and ISM via the atmospheric circulation, water vapor transport and an anomalous Hadley cell circulation. The results indicate a reliable prediction reference for precipitation in CA.

scholarly journals Changes in Winter Atmospheric Rivers along the North American West Coast in CMIP5 Climate Models

2015 ◽  
Vol 16 (1) ◽  
pp. 118-128 ◽  
Author(s):  
Michael D. Warner ◽  
Clifford F. Mass ◽  
Eric P. Salathé
Keyword(s):  
Water Vapor ◽  
North American ◽  
West Coast ◽  
American West ◽  
Climate Models ◽  
Water Vapor Transport ◽  
The West ◽  
North American West ◽  
The North ◽  
Extreme Precipitation Events

Abstract Most extreme precipitation events that occur along the North American west coast are associated with winter atmospheric river (AR) events. Global climate models have sufficient resolution to simulate synoptic features associated with AR events, such as high values of vertically integrated water vapor transport (IVT) approaching the coast. From phase 5 of the Coupled Model Intercomparison Project (CMIP5), 10 simulations are used to identify changes in ARs impacting the west coast of North America between historical (1970–99) and end-of-century (2070–99) runs, using representative concentration pathway (RCP) 8.5. The most extreme ARs are identified in both time periods by the 99th percentile of IVT days along a north–south transect offshore of the coast. Integrated water vapor (IWV) and IVT are predicted to increase, while lower-tropospheric winds change little. Winter mean precipitation along the west coast increases by 11%–18% [from 4% to 6% (°C)−1], while precipitation on extreme IVT days increases by 15%–39% [from 5% to 19% (°C)−1]. The frequency of IVT days above the historical 99th percentile threshold increases as much as 290% by the end of this century.

Circulation Features Associated with the Record-Breaking Rainfall over South China in June 2017

2018 ◽  
Vol 31 (18) ◽  
pp. 7209-7224 ◽  
Author(s):  
Jianqi Sun ◽  
Jing Ming ◽  
Mengqi Zhang ◽  
Shui Yu
Keyword(s):  
East Asia ◽  
South China ◽  
North Atlantic ◽  
Large Scale ◽  
Wave Train ◽  
Western Pacific Subtropical High ◽  
Early Summer ◽  
Intense Rainfall ◽  
Maritime Continent ◽  
Anomalous Anticyclone

In June 2017, south China suffered from intense rainfall that broke the record spanning the previous 70 years. In this study, the large-scale circulations associated with the south China June rainfall are analyzed. The results show that the anomalous Pacific–Japan (PJ) pattern is a direct influence on south China June rainfall or East Asian early summer rainfall. In addition, the Australian high was the strongest in June 2017 during the past 70 years, which can increase the equatorward flow to northern Australia and activate convection over the Maritime Continent. Enhanced convection over the Maritime Continent can further enhance local meridional circulation along East Asia, engendering downward motion over the tropical western North Pacific and enhancing the western Pacific subtropical high (WPSH) and upward motion over south China, which increases the rainfall therein. In addition, a strong wave train pattern associated with North Atlantic air–sea interaction was observed in June 2017 at Northern Hemispheric mid- to high latitudes; it originated from the North Atlantic and propagated eastward to East Asia, resulting in an anomalous anticyclone over the Mongolian–Baikal Lake region. This anomalous anticyclone produced strong northerly winds over East Asia that encountered the southerly associated with the WPSH over south China, thereby favoring intense rainfall over the region. Case studies of June 2017 and climate research based on data during 1979–2017 and 1948–2017 indicate that the extremities of the atmospheric circulation over south Europe and Australian high and their coupling with the PJ pattern could be responsible for the record-breaking south China rainfall in June 2017.

Estimation of the precipitable water and water vapor flux using MAX-DOAS in two typical  cities of China

2021 ◽  
Author(s):  
Hongmei Ren ◽  
Ang Li ◽  
Pinhua Xie ◽  
Zhaokun Hu ◽  
Jin Xu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Precipitable Water ◽  
Reanalysis Data ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Optical Absorption Spectroscopy ◽  
Water Vapor Flux ◽  
Vapor Flux ◽  
The North ◽  
Two Cities

<p>      Water vapor transport affects regional precipitation and climate change. The measurement of precipitable water and water vapor flux is of great significance to the study of precipitation and water vapor transport. In the study, a new method of computing the precipitable water and estimating the water vapor transport flux using multi-axis differential optical absorption spectroscopy (MAX-DOAS) were presented. The calculated precipitable water and water vapor flux were compared to the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data and the correlation coefficient of the precipitable water, the zonal and meridional water vapor flux and ECMWF are r≥0.92, r=0.77 and r≥0.89, respectively. The seasonal and diurnal climatologies of precipitable water and water vapor flux in the coastal (Qingdao) and inland (Xi’an) cities of China using this method were analyzed from June 1, 2019 to May 31, 2020. The results indicated that the seasonal and diurnal variation characteristics of the precipitable water in the two cities were similar. The zonal fluxes of the two cities were mainly transported from west to east, Qingdao's meridional flux was mainly transported to the south, and Xi'an was mainly transported to the north. The results also indicated that the water vapor flux transmitting belts appear near 2km and 1.4km above the surface in Qingdao and appeared around 2.8km, 1.6km and 1.0km in Xi'an. </p>

Response of Seasonal Simulations of a Regional Climate Model to High-Frequency Variability of Soil Moisture during the Summers of 1988 and 1993

2007 ◽  
Vol 8 (4) ◽  
pp. 738-757 ◽  
Author(s):  
Song Yang ◽  
S-H. Yoo ◽  
R. Yang ◽  
K. E. Mitchell ◽  
H. van den Dool ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Vapor ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Water Vapor Transport ◽  
Diurnal Variability ◽  
High Frequency Variability

Abstract This study employs the NCEP Eta Regional Climate Model to investigate the response of the model’s seasonal simulations of summer precipitation to high-frequency variability of soil moisture. Specifically, it focuses on the response of model precipitation and temperature over the U.S. Midwest and Southeast to imposed changes in the diurnal and synoptic variability of soil moisture in 1988 and 1993. High-frequency variability of soil moisture increases (decreases) precipitation in the 1988 drought (1993 flood) year in the central and southern-tier states, except along the Gulf Coast, but causes smaller changes in precipitation along the northern-tier states. The diurnal variability and synoptic variability of soil moisture produce similar patterns of precipitation change, indicating the importance of the diurnal cycle of land surface process. The increase (decrease) in precipitation is generally accompanied by a decrease (increase) in surface and lower-tropospheric temperatures, and the changes in precipitation and temperature are attributed to both the local effect of evaporation feedback and the remote influence of large-scale water vapor transport. The precipitation increase and temperature decrease in 1988 are accompanied by an increase in local evaporation and, more importantly, by an increase in the large-scale water vapor convergence into the Midwest and Southeast. Analogous but opposite-sign behavior occurs in 1993 (compared to 1988) in changes in precipitation, temperature, soil moisture, evaporation, and large-scale water vapor transport. Results also indicate that, in regions where the model simulates the diurnal cycle of soil moisture reasonably well, including this diurnal cycle in the simulations improves model performance. However, no notable improvement in model precipitation can be found in regions where the model fails to realistically simulate the diurnal variability of soil moisture.

Interdecadal Variation of the Relationship between East Asian Water Vapor Transport and Tropical Pacific Sea Surface Temperatures during January and Associated Mechanisms

2019 ◽  
Vol 32 (21) ◽  
pp. 7575-7594 ◽  
Author(s):  
Bo Sun ◽  
Huijun Wang ◽  
Botao Zhou
Keyword(s):  
Water Vapor ◽  
East Asia ◽  
East Asian ◽  
Tropical Pacific ◽  
Vapor Transport ◽  
Sea Surface ◽  
Water Vapor Transport ◽  
The Relationship ◽  
Asian Water ◽  
Sst Anomalies

Abstract This study examined the interdecadal variations in the relationship between the East Asian water vapor transport (WVT) and the central and eastern tropical Pacific (CETP) sea surface temperatures (SSTs) in January during 1951–2018, focusing on the meridional WVT over East Asia, which is critical for the East Asian winter precipitation. The results indicate that before the 1980s, an increased southerly WVT over East Asia was generally associated with warm SST anomalies in the CETP during January, whereas, after the mid-1980s, an increased southerly WVT over East Asia was mostly associated with cold SST anomalies in the central tropical Pacific during January. The underlying mechanisms are discussed based on a comparison on the climate anomalies associated with the East Asian meridional WVT between the periods of 1951–79 and 1986–2018. During 1951–79, the meridional WVT over East Asia was mainly modulated by the Pacific–East Asian (PEA) teleconnection, which would induce an anomalous southerly WVT over East Asia corresponding to warm SST anomalies in the CETP. Whereas, during 1986–2018, the connection between the PEA teleconnection and the East Asian meridional WVT was weakened. The connection among the CETP SSTs, the anomalous zonal circulation over the North Pacific, and the East Asian meridional WVT was enhanced. Additionally, the connection among the CETP SSTs, the circumglobal teleconnection in the Northern Hemisphere, and the East Asian meridional WVT was enhanced. The above two enhanced connections opposed the effect of the PEA teleconnection and would induce an anomalous southerly WVT over East Asia corresponding to cold SST anomalies in the central tropical Pacific.

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