scholarly journals Are precipitation anomalies associated with aerosol variations over eastern China?

2017 ◽  
Vol 17 (12) ◽  
pp. 8011-8019 ◽  
Author(s):  
Xiangde Xu ◽  
Xueliang Guo ◽  
Tianliang Zhao ◽  
Xingqin An ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Interannual Variability ◽  
Eastern China ◽  
Interdecadal Variation ◽  
Atmospheric Environment ◽  
Precipitation Process ◽  
The South ◽  
Light Rain ◽  
The North ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Abstract. In eastern China (EC), the strong anthropogenic emissions deteriorate the atmospheric environment, building a south–north zonal distribution of high aerosols harbored by the upstream Tibetan and Loess plateaus in China. This study climatologically analyzed the interannual variability in precipitation with different intensities in association with aerosol variations over the EC region from 1961 to 2010 by using precipitation and visibility data from more than 50 years and aircraft and surface aerosol data from recent years in China, and the impacts of aerosol variations on interannual variability in the intensity of precipitation events and their physical causes are investigated. We found that the frequency of light rain has significantly decreased and the occurrence of rainstorms, especially severe rainstorms, has significantly increased over recent decades. The extreme precipitation events presented an interannual variability pattern similar to that of the frequent haze events over EC. Accompanied by the frequent haze events in EC, light rain frequency significantly decreased and extremely heavy precipitation events have occurred more frequently. During the 1980s, the regional precipitation trends in EC showed an obvious transform from more light rain to more extreme rainstorms. The running correlation analysis of interdecadal variation further verified that the correlation between the increasing aerosols and frequencies of abnormal precipitation events tended to be more significant in EC. The correlation between atmospheric visibility and low cloud amounts, which are both closely related to aerosol concentrations, was positive in the north and negative in the south, and the spatial distribution of the variability in regional rainstorm frequency was positive in the south and negative in the north. After the 1990s, the visibility in summer season deteriorated more remarkably, light rain frequency decreased noticeably, and rainstorms and extraordinarily heavy rainfall occurred more frequently. There were significant differences in the interdecadal variation trends in light rain and rainstorm events between the highly aerosol-polluted area in EC and the relatively clean area on the western plateaus of China. The aircraft measurements over EC confirmed that the diameters of cloud droplets decreased under high aerosol concentration conditions, thereby inhibiting weak precipitation process.

scholarly journals Are precipitation anomalies associated with aerosol variations over Eastern China?

2017 ◽  
Author(s):  
Xiangde Xu ◽  
Xueliang Guo ◽  
Tianliang Zhao ◽  
Xingqin An ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Interannual Variability ◽  
Eastern China ◽  
Interdecadal Variation ◽  
Aerosol Concentration ◽  
Atmospheric Environment ◽  
Western China ◽  
Light Rain ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Abstract. In Eastern China (EC), strong anthropogenic emissions deteriorate the atmospheric environment harbored by the upstream Tibetan and Loess Plateaus, building a south-north zonal distribution of high anthropogenic aerosols. This research analyzed the interannual variability of precipitations with different intensities in the EC region from 1961 to 2010. We found that the frequency of light rain significantly decreased and the occurrence of rainstorm, especially the extraordinary rainstorm significantly increased over the recent decades. The extreme precipitation events presented the same interannual variability pattern with the frequent haze events. Moreover, the extreme rainfall events of various intensities showed a regular interannual variability trend. During the 1980s, the regional precipitation trends in EC showed an obvious "transform" from more light rain to more extreme rainstorms. The running correlation analysis of interdecadal variation further verified that the correlation between the increasing aerosol emissions and the frequency of abnormal precipitation events tended to be more significant in the EC. The correlation between atmospheric visibility and low cloud amounts, which are both closely related with aerosol concentrations, had a spatial distribution of "northern positive and southern negative" pattern, and the spatial distribution of the frequency variability of regional rainstorms was "southern positive and northern negative". After the 1990s, the visibility in summer season deteriorated more remarkably than other seasons, and the light rain frequency decreased obviously while the rainstorm and extraordinary heavy rainfall occurred more frequently. There were significant differences in the interdecadal variation trends in light rain and rainstorm events between the high aerosol concentration areas in the EC and the relatively "clean area" in western China. The aircraft measurements over the EC confirmed that the diameters of cloud droplets decreased under high aerosol concentration condition, thereby inhibiting weak precipitation process.

scholarly journals Large-Scale Flow Patterns Associated with Extreme Precipitation and Atmospheric Rivers over Norway

2019 ◽  
Vol 147 (4) ◽  
pp. 1415-1428 ◽  
Author(s):  
Imme Benedict ◽  
Karianne Ødemark ◽  
Thomas Nipen ◽  
Richard Moore
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
Moisture Flux ◽  
Cold Season ◽  
Fuzzy Cluster ◽  
The South ◽  
Atmospheric Rivers ◽  
The North ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Abstract A climatology of extreme cold season precipitation events in Norway from 1979 to 2014 is presented, based on the 99th percentile of the 24-h accumulated precipitation. Three regions, termed north, west, and south are identified, each exhibiting a unique seasonal distribution. There is a proclivity for events to occur during the positive phase of the NAO. The result is statistically significant at the 95th percentile for the north and west regions. An overarching hypothesis of this work is that anomalous moisture flux, or so-called atmospheric rivers (ARs), are integral to extreme precipitation events during the Norwegian cold season. An objective analysis of the integrated vapor transport illustrates that more than 85% of the events are associated with ARs. An empirical orthogonal function and fuzzy cluster technique is used to identify the large-scale weather patterns conducive to the moisture flux and extreme precipitation. Five days before the event and for each of the three regions, two patterns are found. The first represents an intense, southward-shifted jet with a southwest–northeast orientation. The second identifies a weak, northward-shifted, zonal jet. As the event approaches, regional differences become more apparent. The distinctive flow pattern conducive to orographically enhanced precipitation emerges in the two clusters for each region. For the north and west regions, this entails primarily zonal flow impinging upon the south–north-orientated topography, the difference being the latitude of the strong flow. In contrast, the south region exhibits a significant southerly component to the flow.

scholarly journals Recognizing the Aggregation Characteristics of Extreme Precipitation Events Using Spatio-Temporal Scanning and the Local Spatial Autocorrelation Model

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 218
Author(s):  
Changjun Wan ◽  
Changxiu Cheng ◽  
Sijing Ye ◽  
Shi Shen ◽  
Ting Zhang
Keyword(s):  
Spatial Autocorrelation ◽  
Extreme Precipitation ◽  
Eastern China ◽  
Temporal Aggregation ◽  
Global Changes ◽  
Percentile Method ◽  
Extreme Precipitation Events ◽  
Spatio Temporal ◽  
Precipitation Events ◽  
Local Spatial Autocorrelation

Precipitation is an essential climate variable in the hydrologic cycle. Its abnormal change would have a serious impact on the social economy, ecological development and life safety. In recent decades, many studies about extreme precipitation have been performed on spatio-temporal variation patterns under global changes; little research has been conducted on the regionality and persistence, which tend to be more destructive. This study defines extreme precipitation events by percentile method, then applies the spatio-temporal scanning model (STSM) and the local spatial autocorrelation model (LSAM) to explore the spatio-temporal aggregation characteristics of extreme precipitation, taking China in July as a case. The study result showed that the STSM with the LSAM can effectively detect the spatio-temporal accumulation areas. The extreme precipitation events of China in July 2016 have a significant spatio-temporal aggregation characteristic. From the spatial perspective, China’s summer extreme precipitation spatio-temporal clusters are mainly distributed in eastern China and northern China, such as Dongting Lake plain, the Circum-Bohai Sea region, Gansu, and Xinjiang. From the temporal perspective, the spatio-temporal clusters of extreme precipitation are mainly distributed in July, and its occurrence was delayed with an increase in latitude, except for in Xinjiang, where extreme precipitation events often take place earlier and persist longer.

Extreme precipitation events during the South Asian summer monsoon season in the past century

2021 ◽  
Author(s):  
Renaud Falga ◽  
Chien Wang
Keyword(s):  
South Asian ◽  
Extreme Events ◽  
Extreme Precipitation ◽  
Monsoon Season ◽  
Past Century ◽  
South Asian Summer Monsoon ◽  
The South ◽  
The Past ◽  
Extreme Precipitation Events ◽  
Precipitation Events

<p>The South Asian monsoon system impacts the livelihoods of over a billion people. While the overall monsoon rainfall is believed to have decreased during the 20<sup>th</sup> century, there is a good agreement that the extreme precipitation events have been rising in some parts of India. As an important part of the Indian population is dependent on rainfed agriculture, such a rise in extremes, along with resulting flood events, can be all the more problematic. Although studies tend to link this rise in extreme events with anthropogenic forcing, some uncertainties remain on the exact causes. In order to examine the correlation between anthropogenic forcings and the different trends in extreme events, we have analyzed the high-resolution daily rainfall data in the past century delivered by the Indian Meteorological Department alongside several other economic and ecological estimates. The results from this analysis will be presented in detail.</p>

scholarly journals Meteorological Drought Changes and Related Circulation Characteristics in Yulin City of the Northern Shaanxi from 1961 to 2015

Atmosphere ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1196
Author(s):  
Yixing Yin ◽  
Lijuan Zhang ◽  
Xiaojun Wang ◽  
Wucheng Xu ◽  
Wenjun Yu ◽  
...  
Keyword(s):  
Water Vapor ◽  
Standardized Precipitation Index ◽  
Meteorological Drought ◽  
Precipitation Process ◽  
Observation Data ◽  
The South ◽  
Vapor Flux ◽  
The North ◽  
Northern Shaanxi ◽  
Yulin City

This study explored the spatio-temporal patterns of meteorological drought change and the mechanisms of drought occurrence in Yulin City of the northern Shaanxi by using Standardized Precipitation Index (SPI), Empirical Orthogonal Function (EOF) analysis and composite analysis based on the meteorological observation data and NCEP/NCAR reanalysis data from 1961 to 2015. The main findings of the research are as follows: (1) In the annual and seasonal drought series, there is a non-significant trend toward drought in summer, while there are non-significant trends toward wetness for the other series. Overall, the frequency of drought is low in the southeast and high in the west and the north of the study area. (2) EOF1 is characterized by a uniform pattern in the whole region, i.e., there is a feature of consistent drought or flood in Yulin City. EOF2, EOF3 and EOF4 mainly indicate opposite characteristics of the changes of floods and droughts in the eastern/western parts and the southeast/other parts in the study area. (3) In the summer of the typical drought (flood) years, the study area is controlled by the northwest airflow behind the trough (zonal airflow at the bottom of low-pressure trough), and the meridional circulation (zonal circulation) is distributed in the mid-latitudes, which is conducive to the intrusion of cold air into the south (north) of China. The cold and warm air intersection area is to the south (to the north). The water vapor flux is weak (strong) and the water vapor divergence (convergence) prohibits (enhances) the precipitation process in the study area.

scholarly journals The South Atlantic Subtropical High: Climatology and Interannual Variability

2017 ◽  
Vol 30 (9) ◽  
pp. 3279-3296 ◽  
Author(s):  
Xiaoming Sun ◽  
Kerry H. Cook ◽  
Edward K. Vizy
Keyword(s):  
Interannual Variability ◽  
Annual Cycle ◽  
Large Scale ◽  
Austral Summer ◽  
Southern Annular Mode ◽  
South Atlantic ◽  
Subtropical High ◽  
Interannual Variations ◽  
The South ◽  
The North

ERA-Interim and JRA-55 reanalysis products are analyzed to document the annual cycle of the South Atlantic subtropical high (SASH) and examine how its interannual variability relates to regional and large-scale climate variability. The annual cycle of the SASH is found to have two peaks in both intensity and size. The SASH is strongest and largest during the solstitial months when its center is either closest to the equator and on the western side of the South Atlantic basin during austral winter or farthest poleward and in the center of the basin in late austral summer. Although interannual variations in the SASH’s position are larger in the zonal direction, the intensity of the high decreases when it is positioned to the north. This relationship is statistically significant in every month. Seasonal composites and EOF analysis indicate that meridional changes in the position of the SASH dominate interannual variations in austral summer. In particular, the anticyclone tends to be displaced poleward in La Niña years when the southern annular mode (SAM) is in its positive phase and vice versa. Wave activity flux vectors suggest that ENSO-related convective anomalies located in the central-eastern tropical Pacific act as a remote forcing for the meridional variability of the summertime SASH. In southern winter, multiple processes operate in concert to induce interannual variability, and none of them appears to dominate like ENSO does during the summer.

scholarly journals Spatial hydrochemical structure in surface waters of the Southern ocean between Africa and Antarctica

2021 ◽  
Vol 67 (4) ◽  
pp. 328-347
Author(s):  
K. V. Artamonova ◽  
I. A. Gangnus ◽  
L. A. Dukhova ◽  
V. V. Maslennikov ◽  
N. A. Lavinen
Keyword(s):  
Surface Layer ◽  
Southern Ocean ◽  
Interannual Variability ◽  
High Latitude ◽  
Polar Front ◽  
Hydrochemical Characteristics ◽  
The South ◽  
The North ◽  
The Antarctic ◽  
Subantarctic Front

Some hydrochemical characteristics and, first of all, the main nutrients (phosphorus, nitrogen, silicon) can be used as markers for distinguishing different types of water masses and positions of the main fronts of the Southern Ocean. The seasonal and interannual variability of these characteristics also reflects the character of biological processes in the surface layer of the ocean, which is important for assessing biological productivity. The aim of this study was to analyze the main features of the spatial distribution of hydrochemical characteristics in the surface layer in the Atlantic and Indian Ocean sectors of the Southern Ocean between the Subantarctic Front and the shores of Antarctica and assess their seasonal (spring–autumn) and interannual variability for the observation period from 2008 to 2020. We describe the surface nutrient concentrations between Africa and Antarctica along the transects that cross the Subantarctic Front (SAF) in the north, the Polar Frontal Zone (PFS), Polar Front (PF) and Antarctic Zone water in the south. The findings revealed an increase in dissolved oxygen and nutrients towards the south. Nitrates changed values within the SAF from 15 μM to 24 μM, whereas values from 1.2 μM to 1.7 μM were observed for phosphates. Silicate increased considerably within the Polar Front, from 6.6 μM to 20.8 μM. An analysis was carried out of the seasonal and interannual variability of the hydrochemical conditions in the surface layer of the Southern Ocean. The interannual variability of the nutrients was determined by the spatial variability of the main fronts of the Antarctic Circumpolar Current (ACC) and the intensity of the largescale Weddell Gyre (WG). Since 2017, there has been an increase in the meridional transfer of waters: in the Antarctic Summer 2017–2018, there was a spreading of high-nutrient WG waters toward the north, and in the Summer 2019–2020, the low-nutrient waters anomaly was transferred far to the south (up to 60°S).According to the data obtained, the seasonal dynamics of the nutrients in the surface layer of the Southern Ocean was rather weakly expressed. An exception is the high-latitude waters of the Cooperation and Davis Seas, where maximum seasonal variability of the hydrochemical characteristics was observed. The highest rate of nutrient consumption was observed in the coastal area of the Cooperation Sea near the fast ice edge from mid–December to early January and reached 3.2 μM per day for silicate, 1.8 μM per day for nitrates, and 0.12 μM per day for mineral phosphorus. The results of the long-term monitoring of the hydrochemical conditions in the Cooperation Sea made it possible to distinguish conditionally “warm” years with early vegetation (at the end of December) and intensive consumption of nutrients by phytoplankton, and “cold” years, when the formation of high-latitude “oases” in December–January was not observed.

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