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Tropical cyclones over the Bay of Bengal (BoBTC) affect the precipitation over China, with distinct seasonal and daily variabilities. This study quantitatively examines the daily standardized precipitation anomalies (SPAs) over China on the days with BoBTC activities (storm-days) and related circulations, based on rainfall measurements at surface meteorological stations and ECMWF reanalysis data on a 0.25° × 0.25° resolution during 1979–2019. Significant positive SPA is found over the stations in the two adjacent regions around BoB (Southwest China in May/November and southern Tibetan Plateau in October) and three distant regions (Southeast China and the northeastern boundary of the Qinghai–Tibet Plateau in May, and central North China in October). The SPA distributions are remarkably consistent with the integrated water vapor transport (IVT) anomalies. Enhanced IVT is found associated with the interaction between southwesterly (southerly) of the BoBTC circulation and low-level monsoonal flow in May (midlevel westerly in winter months). The probabilities of extreme precipitation (EP) occurrences over the above regions all increase on storm-days. For adjacent regions, EP is significantly correlated with the northward IVT anomalies to the east of BoBTC circulation, which strengthen the water vapor input through the southern border. Such IVT anomalies are stronger in May, benefited by the deep monsoonal southwesterlies than those in November. For distant regions, EP is more closely related to the IVT anomaly extending back from BoB. Enhanced moisture from BoB concentrates along a local low-level convergence line over Southeast China, being further facilitated by coexistence of the BoBTC depression and midlevel westerly trough in midlatitudes. Our results highlight the interactions between BoBTCs and local weather systems that influence the general precipitation anomalies and occurrence of EP over China, especially over distant regions. [ABSTRACT FROM AUTHOR]

The climate of Southwest China is wet all year round， but the frequent drought disasters in recent years have caused huge economic losses such as crop yield reduction and forest fire.In order to fully understand the anomalies of water vapor transport in drought years in Southwest China and provide reference for early warning of drought disasters in this area in the future， this study used TRMM and APHRODITE precipitation data to analyze the interannual variation of precipitation and the interannual variation of precipitation in various seasons in Southwest China from 1998 to 2019， selected the summer dry year （2011）， autumn dry year （2009） and 2008， which were relatively wet in summer and autumn.Using Lagrangian transport model FLEXPART， we tracked the paths of water vapor transport and water vapor sources in the two extreme dry seasons （the autumn of 2009 and the summer of 2011）， and compared with the summer and autumn of the wet year （2008）， respectively.The results showed that： （1） The paths of water vapor transport in dry and wet year are consistent， and the paths in southwest China in summer can be divided into three main paths： the southwest path， the southeast path and the northwest path， among which the most dominant is the southwest path， so the main water vapor source area are the Arabian Sea——the Bay of Bengal.In autumn， the main paths can be divided into two： the southeast path and the northwest path， of which the most important is the southeast path， so the main source of water vapor is South China Sea——the Pacific Northwest.（2） There are differences in the strength of water vapor transport between dry and wet years.The reason for the drought in Southwest China in summer is that the water vapor transported by the southwest route is weak， while the reason for the drought in Southwest China in autumn is that the water vapor transported by southeast route is weak.

Composite analyses were performed in this study to reveal the difference in spring precipitation over southern China during multiyear La Niña events during 1901 to 2015. It was found that there is significantly below-normal precipitation during the first boreal spring, but above-normal precipitation during the second year. The difference in spring precipitation over southern China is correlative to the variation in western North Pacific anomalous cyclone (WNPC), which can in turn be attributed to the different sea surface temperature anomaly (SSTA) over the Tropical Pacific. The remote forcing of negative SSTA in the equatorial central and eastern Pacific and the local air-sea interaction in the western North Pacific are the usual causes of WNPC formation and maintenance. SSTA in the first spring is stronger than those in the second spring. As a result, the intensity of WNPC in the first year is stronger, which is more likely to reduce the moisture in southern China by changing the moisture transport, leading to prolonged precipitation deficits over southern China. However, the tropical SSTA signals in the second year are too weak to induce the formation and maintenance of WNPC and the below-normal precipitation over southern China. Thus, the variation in tropical SSTA signals between two consecutive springs during multiyear La Niña events leads to obvious differences in the spatial pattern of precipitation anomaly in southern China by causing the different WNPC response. [ABSTRACT FROM AUTHOR]

Copyright of Plateau Meteorology is the property of Plateau Meteorology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the prediction ability for summer precipitation anomalies in North China and determine the indicators of early abnormal signals， this paper uses the summer precipitation data in North and South China from 1961 to 2020， and the reanalysis circulation data from the National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR）.Via correlation， synthesis and circulation anomaly regression reconstruction， the relationship between the precipitation anomaly in the pre-flood season （May-June） in South China and the precipitation anomaly in summer （July-August） in North China is analyzed.The results show that： （1） the summer precipitation anomaly in North China （July-August） is usually inversely related to the precipitation anomaly in the pre-flood season in South China （May-June）， that is， the higher the precipitation amount in the pre-flood season in South China， then lower the precipitation amount in North China in summer and vice versa.The precipitation anomaly in the pre-flood season in South China can be used as an early indicator for the prediction of summer precipitation in North China.The water vapor transport anomaly in the lower troposphere， caused by the East Asian summer monsoon， and the circulation anomaly in the middle and lower troposphere， caused by the propagation of tropical low-frequency signals in the northern hemisphere in summer， represent the connection mechanism of the inverse phase change of precipitation between the two areas.（2） In terms of water vapor transport， if the East Asian subtropical summer monsoon is stronger from May to June， that is， the East Asian southwest wind （SSW） is significantly stronger， there will be less water vapor in South China， resulting in less precipitation in the pre-flood season （May-June） in South China.From July to August， the Indian summer monsoon is significantly stronger， the East Asian subtropical summer monsoon is further strengthened， and there are significantly more water vapor in North China， resulting in more precipitation in summer （July-August） in North China.On the contrary， there are more precipitation anomalies in the pre-flood season （May-June） in South China and less precipitation anomalies in summer （July-August） in North China.（3） In terms of dynamic circulation， if the tropical Indian Ocean low-frequency signal is active and the Northwest Pacific low-frequency signal is inactive from May to June， with the Indian Ocean low-frequency signal propagating to the northeast， an anticyclonic circulation anomaly will be formed near the South China coast at 850-hPa layer and convection will be weakened， resulting in less precipitation in the pre-flood season （May-June） in South China.From July to August， the low-frequency signal of the tropical Indian Ocean is still highly active.The anticyclonic circulation anomaly originally located along the coast of South China propagates to the northeast to the lower reaches of the Yangtze River to the eastern sea.North China on the northern side to the anticyclonic is subjected to a cyclonic circulation with strong convection.On the other hand， with the low-frequency disturbance propagating from the middle and upper troposphere to the high latitude， a disturbance wave train propagating along the upper westerly jet will be formed， and the disturbance position is relatively fixed.There is a negative anomaly near Baikal Lake and a positive anomaly near the Korean Peninsula， resulting in the deepening of the high trough of Baikal Lake and the strengthening of the subtropical high near the Korean Peninsula， forming a blocking situation of "high in the East and low in the West"， which is conducive to the upward movement in North China.That is， the convective upward movement in North China in summer is strengthened， resulting in more precipitation in summer （July-August） in North China.On the contrary， there is more precipitation in the pre-flood season （May-June） in South China and less precipitation in summer （July-August） in North China.（4） The precipitation anomaly in the pre-flood season in South China is a good indicator of the summer precipitation anomaly in North China.However， in some years， this relationship is not straightforward， most likely because it is also regulated and affected by other factors， such as the change in the sea surface temperature， tropical circulation， the Qinghai-Xizang Plateau， and the change in the circulation in middle and high latitudes.

Precipitation extremes driven by the El Niño–Southern Oscillation (ENSO) are one of the critical ways in which the ENSO impacts the global climate, specifically in the tropical Pacific, where they have the potential to cause extreme weather conditions. However, existing approaches struggle to effectively identify the evolution of ENSO-related precipitation anomalies that change rapidly in spatial distribution. To address this challenge, we propose the object-oriented spatiotemporal clustering approach using remote sensing products (OSCAR) for detecting evolutions of ENSO-related precipitation anomalies. The OSCAR was validated using simulated datasets and applied to precipitation anomalies over the tropical Pacific. The simulation experiment demonstrates that the OSCAR outperforms the dual-constraint spatiotemporal clustering approach (DcSTCA) in accuracy, particularly for rapidly evolving precipitation anomaly variations. The application of the OSCAR demonstrates its ability to recognize the evolution of ENSO-related precipitation anomalies over the tropical Pacific, which may offer valuable references for global climate change research. [ABSTRACT FROM AUTHOR]

Abstract An extreme drought occurred in the Yangtze River Basin in 2022, inflicting huge impacts nationwide. To provide a reference for drought prevention and mitigation, this paper presents a comprehensive analysis of the drought in the Yangtze River Basin in terms of its characteristics, causes, impacts, and response strategies. It concludes that this extreme drought stood out by its long duration, wide impact range, and severe intensity, as a combined result of abnormal high‐temperature weather and massive social water consumption. Serious impacts are observed in various fields of the economy, including agricultural irrigation, urban and rural water supply, power generation, and navigation. Finally, drought mitigation measures and effects are examined, and future drought response and mitigation strategies are proposed.

Copyright of Plateau Meteorology is the property of Plateau Meteorology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Affected by the East Asian summer monsoon, summer floods occur frequently in eastern China, causing huge economic losses and social impacts. In 2021, the precipitation anomaly during the Meiyu period in Yangtze-Huaihe River Valley (YHRV) was abnormally high, with a value of 188.0 mm, about 1.7 standard deviations above normal. However, it did not cause serious flood disasters. This was mainly due to the existence of two precipitation anomaly centers in YHRV, which shared the impact of the excessive precipitation. These two centers were located at the junction of Anhui Province and Henan Province and the junction of Jiangsu Province, Anhui Province and Jiangxi Province, respectively. And more notably, the 2021 Meiyu precipitation anomalies were distributed in a Northwest-Southeast oriented band that is very rare. During the 2021 Meiyu period, the western Pacific subtropical high (WPSH) weakened and extended westward. An anticyclonic circulation anomaly in the lower troposphere was observed over eastern China, which was found to be related to the quasi-stationary wave trains propagating eastward from Hainan Island to the northwestern Pacific by vorticity budget analysis. And the Rossby wave source term played a critical role. In addition, the tropical Atlantic anomalous warming produced convergence anomaly over the eastern Mediterranean and excited quasi-stationary wave trains propagating downstream at the mid-latitudes in upper layers through a monsoon-desert-like teleconnection. It raised the geopotential height over eastern China and thus favored the westward extension of WPSH. These large-scale circulation anomalies generated the anomalous easterly winds along the eastern coast of China and the anomalous southwesterly winds from Guangxi Province to the middle and lower reaches of the Yangtze River. Similar features can be found in the anomalous water vapor transport and the water vapor converged in the YHRV. The above-mentioned reasons jointly caused the abnormally high precipitation anomaly and its unusual pattern in the 2021 Meiyu season. This study might provide a scientific basis and clues for understanding Meiyu precipitation anomalies and disaster prevention and mitigation.

Wildfires are well known as annual disasters in Indonesia. More than 3 million ha was burned in the last 5 years. During an extreme event such as in 2019, carbon emissions can cause smog disasters in neighboring countries such as Malaysia and Singapore. Though difficult to predict, many hotspots that appear can be used to indicate the emergence of large-scale wildfires. The objective of this research is to provide suggestions in terms of used variables when analyzing fire event indication (hotspot), fire event scale (burned area), and fire event impact (carbon emissions). This research provides a spatio-temporal analysis and dependency between drought (precipitation and its derivative variables) and fire indicators (hotspot, burned area, and carbon emission). This research provides the different characteristics of each indicator when used to find joint patterns of burned areas, hotspots, and carbon emissions. Overall, using potential evapotranspiration and precipitation to calculate climate water balance gives great results in all analysis. Precipitation anomalies give the best joint spatial pattern to describe wildfire events in the area with monsoonal rainfall. Meanwhile, precipitation gives better results by capturing more wildfire events in a temporal pattern, even on robust analysis. [ABSTRACT FROM AUTHOR]

Precipitation extremes driven by the El Niño–Southern Oscillation (ENSO) are one of the critical ways in which the ENSO impacts the global climate, specifically in the tropical Pacific, where they have the potential to cause extreme weather conditions. However, existing approaches struggle to effectively identify the evolution of ENSO-related precipitation anomalies that change rapidly in spatial distribution. To address this challenge, we propose the object-oriented spatiotemporal clustering approach using remote sensing products (OSCAR) for detecting evolutions of ENSO-related precipitation anomalies. The OSCAR was validated using simulated datasets and applied to precipitation anomalies over the tropical Pacific. The simulation experiment demonstrates that the OSCAR outperforms the dual-constraint spatiotemporal clustering approach (DcSTCA) in accuracy, particularly for rapidly evolving precipitation anomaly variations. The application of the OSCAR demonstrates its ability to recognize the evolution of ENSO-related precipitation anomalies over the tropical Pacific, which may offer valuable references for global climate change research.

Based on the daily precipitation data of 244 meteorological stations in the Yellow River Basin, the NCEP/NCAR monthly reanalysis data, and the monthly average sea temperature data of the Hadley Climate Prediction and Research Center of the British Met Office, the characteristics and large-scale precipitation anomalies in the Yellow River Basin in July 2018 were analyzed. Circulation characteristics, and further explore the influence of SST on precipitation and circulation anomalies. The results show that: (1) In July 2018, the average precipitation in the Yellow River Basin was 41.5% higher than that in the same period of the previous year, which was the second largest since 2000. Among them, the Lanzhou-Tuoketuo area, the Shan-Shaanxi area, the Jingwei River and the Fenhe River were more abundant. obvious. ② In July 2018, the atmospheric circulation in Eurasia showed obvious anomalies, the South Asian high was abnormally strengthened and extended eastward, the subtropical westerly jet in East Asia was abnormally northerly, and the circulation in the middle and high latitudes of East Asia showed a situation of “low in the west and high in the east”, and the Lake Balkhash to Lake Baikal showed a situation of “low in the west and high in the east” The area is controlled by a trough of low pressure, and the subtropical high in the Northwest Pacific is anomalous from the west to the north. The cold air from the middle and high latitudes continues to split southward and the warm and humid air from the northwest side of the subtropical high meets in the Yellow River Basin, resulting in more precipitation in the basin as a whole. (3) The abnormally cold equatorial SST in the equatorial Middle East Pacific in the early spring and the continuously warmer mid-latitude North Pacific SST are important external forcing factors that cause atmospheric circulation and precipitation anomalies in the Yellow River Basin. [ABSTRACT FROM AUTHOR]

In this study, atmospheric moisture source regions and transport pathways, which substantially affect extreme summer precipitation events in the source region of the Yellow River (SRYR) of China were investigated using the Lagrangian Flexible Particle Dispersion Model (FLEXPART). Based on the 24‐hour cumulative precipitation data from the China Meteorological Data Service Center, 2012 and 2015 were selected to represent wet and dry years during the period 2007–2016, respectively. The results indicate that potential moisture sources include the northern Tibetan Plateau, the Bay of Bengal, the southern edge of the Himalayas, Sichuan Basin, and the SRYR. In the wet year, moisture from the southern branch was transported along two pathways: (a) moisture from the Arabian Sea was carried by the Somalia jet and entered the SRYR through the Indian Peninsula and Bay of Bengal, and (b) moisture from the South China Sea entered the SRYR through the Sichuan Basin. In the dry year, the moisture primary originated from the northern branch. Moisture from the eastern European Plain or northern Africa was carried by the westerly jet and entered the SRYR. It is estimated that the ratios of moisture from the northern and southern branches contributing to the precipitation in the SRYR were 22.1 and 15.9% in the wet year, while they were 52.9 and 8.4% in the dry year, respectively. Internal moisture recycling contributed ~22.0% to precipitation in the wet year and 11.0% in the dry year. In this study, the transport trajectories of moisture contributing to extreme precipitation events in the SRYR are delineated. The results indicate that the northern branch is the primary contributor of moisture in the SRYR. [ABSTRACT FROM AUTHOR]

Based on the NCEP/ NCAR reanalysis monthly mean data and NOAA global daily precipitation data, the present study analyzes the temporal and spatial characteristics of the vertical structure variation of the South China Sea summer monsoon (SCS-SM) by using the empirical orthogonal function (EOF) method, and then discusses the influence and mechanism of the vertical structure of the SCS-SM on summer precipitation in China. The main conclusions are as follows: (1) The vertical structures of the SCS- SM feature obvious inter-annual and interdecadal variation. The first mode of EOF mainly shows the inter- annual variation of the vertical structure of the SCS-SM, which consists of two typical structural changes, i. e., the simultaneous increase (decrease) of the southwest wind in the lower troposphere and the northeast wind in the upper troposphere (referred to as"lower-upper troposphere simultaneous enhancement"and "lower-higher troposphere simultaneous weakening" ); the second mode of EOF mainly features the interdecadal change of the vertical structure of the SCS-SM, which can be divided into two vertical structure changes of two different ages (periods): the change of the southwest wind (northeast wind) at the lower troposphere (upper troposphere) from enhancement to weakening from bottom to top with height, and the change of the southwest wind (northeast wind) at the lower troposphere (upper troposphere) from weakening to enhancement (referred to as"low troposphere from stronger to weaker-upper troposphere from stronger to weaker"and"low troposphere from weaker to stronger-upper troposphere from weaker to stronger" ). (2) The changes of the SCS-SM vertical structure significantly affect the anomalous changes of summer precipitation in eastern China by changing the circulation anomalies in the lower and upper troposphere. When the SCS-SM presents a vertical structure of"lower-upper troposphere simultaneous enhancement", the low-latitude tropical monsoon circulation in the SCS is anomalously strengthened, and there are the low-level divergence, upper-level convergence and abnormal subsidence movement in the Yangtze River Basin. At the same time, southern China and northeastern China are characterized by low- level convergence, upper-level divergence, and abnormal ascending movements. Such a low-upper-level circulation configuration leads to abnormally high precipitation in southern China, less precipitation in the Yangtze River Basin, and more precipitation in the north. It is the opposite in the"lower-higher troposphere simultaneous weakening"years. When the SCS-SM vertical structure is in the period of"low troposphere from weaker to stronger-upper troposphere from weaker to stronger", from southern China to northeastern China, the circulation conditions of low-level convergence (divergence) and high-level convergence (convergence) are favorable to the rising (sinking) movement, which leads to the increase of precipitation in southern China and Jianghuai areas, and the decrease in the precipitation in Jiangnan and northeastern China. The opposite is true for the period of"low troposphere from stronger to weaker-upper troposphere from stronger to weaker" . [ABSTRACT FROM AUTHOR]

Droughts and related water stress are the major constraints of the sustainable socioeconomic development of Bangladesh. Large-scale atmospheric oscillations are the major drivers of climate fluctuation and droughts in Bangladesh, like many other regions of Asia including the Indian subcontinent, the largest entity in the world, with over 1.7 billion people. Therefore, it is crucial to insight into the spatiotemporal distribution of drought and its linkage to large-scale atmospheric indices to provide early warning and alleviate drought impacts. However, regional droughts and their linkages to large-scale oscillation indices like El-Nino Southern Oscillation (ENSO) are not explored adequately in Bangladesh. This study intends to evaluate the spatiotemporal distribution of droughts in Bangladesh using the standardized precipitation evapotranspiration index (SPEI) and the standardized precipitation index (SPI) for multiple timescales, − 3, − 6, − 12, and 24-months, and to investigate the relationship of drought characteristics with ENSO. The monthly rainfall and temperature records from twenty locations for 38 years from the period 1980 to 2017 were used for this purpose. The results revealed that the droughts are region-specific and are in agreement with the warming trends observed in the different regions of Bangladesh. The droughts, particularly short-term droughts, are increasing significantly in the North-western region, indicating the worsening drought conditions in the drought-prone region. The SPI and SPEI showed a significant (p < 0.05) positive association with the percentage of precipitation anomaly (Pa). However, the association of drought indices with ENSO and potential evapotranspiration (PET) were not significant. The polynomial regression model demonstrated that Indian Ocean Dipole (IOD) could explain SPEI-3 (4.7%) variations better than SPI-3 (4.2%). [ABSTRACT FROM AUTHOR]

The study of teleconnection patterns is important to define and predict the temperature and precipitation anomalies and climate changes on a regional scale. In this study, the precipitation anomalies and intensities are analyzed in different El Niño–Southern Oscillation (ENSO) phases based on statistic-synoptic and dynamic approaches in Iran's basins. For this purpose, a network of 717 meteorological stations and rain gauges was created during the period 1987–2015 in 6 basins and 30 sub-basins in Iran. The precipitation anomalies and intensities of these basins were statistically analyzed in different ENSO phases and Oceanic Niño Index (ONI), respectively. To analyze the synoptic and dynamic conditions in a medium El Niño, the negative and positive anomalies in the precipitation were examined in winter 2003 and spring 1992 using monthly European Centre for Medium-Range Weather Forecasts (ECMWF) data. Also, moisture flux convergence (MFC) was calculated and plotted for the lower (850–1000), middle (700–750), and upper (500–600) hPa troposphere layers using GrADS. The results of the precipitation anomalies showed positive and negative fluctuations of ± 100 to ± 150 mm in ENSO phases and ± 50 mm in the neutral phase. Consequently, the seasonal and annual precipitation anomalies were escalated in different ENSO intensities and their different phases. Moreover, it was found that the southeastern, eastern, and central plateau basins were slightly affected by the ENSO. Synoptic and dynamic analysis of precipitation anomalies also demonstrated the role of westward displacement (sea to land) and eastward (land to sea) components of Saudi Arabia's high-pressure system. During the positive precipitation anomalies (with a significant eastward displacement to the east and settled on the Arabian Sea), advection of heat and humidity toward Iran and penetration trough in the Middle East caused the increased intensity and extension of precipitations. [ABSTRACT FROM AUTHOR]

Precipitation is one of the most important and complex climatic elements. This vital element, on which the lives of living organisms and fauna depend, has highly variable temporal and spatial distributions in the world. While limited areas of the planet have an excess precipitation, a large part of it is facing the shortage of this vital element. Therefore, its spatial distribution on the Earth is not at all satisfactory to the inhabitants. In the subtropical regions, this limitation is of great significance. For this reason, officials and users are so willing to receive more precipitation during the cooler months and minimize water loss from evaporation and transpiration. Winter precipitation can be very useful and effective in these areas. Several studies conducted on the trend of monthly precipitations in the cold periods of the year in the southern regions of Iran have found significant decreases in February precipitations compared to those of the two previous and following months recorded at most of the south and southwest stations. Considering that southern regions are among the few regions in Iran where the precipitation periods correspond to the cultivation periods, this problem was studied and analyzed as the main issue of this research. [ABSTRACT FROM AUTHOR]

Abstract Precipitation predictions in the sub‐seasonal timescale are very important for several sectors such as agriculture and energy in regions of South America that are very much affected by precipitation extremes, both excess and lack of rain. The aim of the present study is to investigate the ability of two S2S project models (ECMWF and NCEP) to detect the Southern Hemisphere teleconnections in model hindcasts and the associated anomalous precipitation over South America. The period of analyses is 1999–2010 for the austral summer season (December–January–February). Both models represented adequately the Southern Annular Mode (SAM) pattern in predictions up to 4 weeks ahead and the Pacific South America (PSA) pattern up to 3 weeks. Atmospheric variables of observed extreme cases of SAM were well predicted by the two models, 2 and 3 weeks in advance. The models predicted well atmospheric variables in observed extreme cases of PSA, 2 weeks in advance and with less intensity in the third week. Precipitation anomaly signals associated with these modes were well predicted 2 weeks in advance, although with different intensities. The good ability of the models hindcast in predicting teleconnection patterns and precipitation anomalies over South America provides more confidence to use predictions at sub‐seasonal timescale.

Precipitation predictions in the sub-seasonal timescale are very important for several sectors such as agriculture and energy in regions of South America that are very much affected by precipitation extremes, both excess and lack of rain. The aim of the present study is to investigate the ability of two S2S project models (ECMWF and NCEP) to detect the Southern Hemisphere teleconnections in model hindcasts and the associated anomalous precipitation over South America. The period of analyses is 1999-2010 for the austral summer season (December-January-February). Both models represented adequately the Southern Annular Mode (SAM) pattern in predictions up to 4 weeks ahead and the Pacific South America (PSA) pattern up to 3 weeks. Atmospheric variables of observed extreme cases of SAM were well predicted by the two models, 2 and 3 weeks in advance. The models predicted well atmospheric variables in observed extreme cases of PSA, 2 weeks in advance and with less intensity in the third week. Precipitation anomaly signals associated with these modes were well predicted 2 weeks in advance, although with different intensities. The good ability of the models hindcast in predicting teleconnection patterns and precipitation anomalies over South America provides more confidence to use predictions at sub-seasonal timescale. [ABSTRACT FROM AUTHOR]

Precipitation prediction during flood season has been a key task of climate prediction for a long time. This type of prediction is linked with the national economy and people's livelihood, and is also one of the difficult problems in climatology. At present, there are some precipitation forecast models for the flood season, but there are also some deviations from these models, which makes it difficult to forecast accurately. In this paper, based on the measured precipitation data from the flood season from 1993 to 2019 and the precipitation return data of CWRF, ANN cycle modeling and a weighted integration method is used to correct the CWRF used in today's operational systems. The MAE and TCC of the precipitation forecast in the flood season are used to check the prediction performance of the proposed algorithm model. The results demonstrate a good correction effect for the proposed algorithm. In particular, the MAE error of the new algorithm is reduced by about 50%, while the time correlation TCC is improved by about 40%. Therefore, both the generalization of the correction results and the prediction performance are improved. [ABSTRACT FROM AUTHOR]

In order to explore the method and index of potato fine drought forecast in central Inner Mongolia, based on the data of potato yield and precipitation in Wuchuan County of Hohhot City, Cuyang County of Baotou City, and Chayou Middle Banner of Ulan Qab City from 1979 to 2013, the relationship between precipitation anomaly percentage and meteorological yield during potato growth period in central Inner Mongolia was analyzed by regression analysis. According to the precipitation anomaly percentage meteorological drought index, the light drought, medium drought and heavy drought indexes of the seedling stage and flowering stage in the above-mentioned areas were obtained as follows; - 5% - - 25%, - 25% - - 40%, and < -40%, respectively. The results show that the models are more accurate in determining the yield reduction caused by drought, and can well predict the occurrence of drought. [ABSTRACT FROM AUTHOR]

The reversed impacts of the Arctic oscillation (AO) on precipitation over the South China Sea and its surrounding areas (SCSA) in October and November during 1979–2014 are investigated. The correlation coefficients between AO and the precipitation in October and November are 0.44 and − 0.31, which are statistically significant at the 99% and 90% confidence levels, respectively. In October (November), the specific humidity exhibits obvious positive (negative) anomalies in the SCSA, and an upward (downward) airflow moving from ground to the upper troposphere (1000–150 hPa) between 10°N and 30°N (10°N and 20°N) is observed with more (less) cloud cover. Moisture budget diagnosis suggests that the precipitation's increasing (decreasing) in October (November) mainly contributed by zonal moisture flux convergence (divergence). Furthermore, the Rossby wave guided by westerlies tends to motivate positive geopotential height in the upper troposphere over approximately 20°–30°N, 40°–80°E in October, which is accompanied by a stronger anticyclone in the Arabian Sea region. However, in November, the wave train propagating from the Arabian Sea to the Bay of Bengal is observed in the form of cyclones and anticyclones. Further analysis reveal that the AO in October may increase precipitation through the southern wave train (along the westerly jet stream from North Africa to the Middle East and South China). Moreover, air-sea interactions over the North Pacific might also generate horseshoe-shaped sea surface temperature (SST) anomalies characterized by positive SST in the central subtropical North Pacific surrounded by negative SST, which may affect the precipitation in the SCSA. Ensemble-mean results from CMIP6 historical simulations further confirm these relationships, and the models that can better simulate the observed positive geopotential height in the Arabian Sea present more consistent precipitation's increasing over the SCSA in October. [ABSTRACT FROM AUTHOR]

In this paper, the features and possible causes of extreme precipitation in the winter of 2019/2020 in China are investigated based on the observational station daily dataset provided by the China Meteorological Administration and the ECMWF ERA5 reanalysis dataset. Record-breaking precipitations are found in most areas of China in the winter of 2019/2020, particularly for the north of China. The magnitude of precipitation in south (north) of China in 2019/2020 increase 0.39 mm/day (0.15 mm/day), about 39.0% (105.5%) compared with the climatological mean. Moisture budget analysis shows that contributions of atmospheric circulation anomaly on horizontal moisture advection and total moisture flux convergence are primarily responsible for the positive anomalies of precipitation in China. Further analysis suggests that the weakened East Asian Trough and the anti-cyclone circulation anomaly over the Sea of Japan favor the transportation of low-level warm and humid airflow from the Northwest Pacific and the East China Sea to the north of China. Meanwhile, the westward movement of the Subtropical High and the Southern Branch Trough anomalies transport low-level warm and humid air from the Bay of Bengal and the South China Sea to south of China. The warm moist air flows northeastward from the East China Sea, Bay of Bengal and the South China Sea while the climatological cold wind flows southeastward, which causes the increase of local precipitation in the winter of 2019/2020. In consideration of the fact that stratospheric polar vortex anomaly has a process of downward propagation to the troposphere, it is of great significance to study the changes of the stratosphere and the relationships between stratosphere and troposphere.

تاريخچة اقليمي استان چهارمحال و بختياري در منطقة زاگرس مرکزي نشان دهندة فراواني بارش برف در فص سرد اس. در سال هاي اخير گرايش بارش ها از برف به باران در فصول پاييز و زمستان افزايش و بارش برف در فص زمستان در استان نسب. به ميانگين بلندمدت کاهش يافته اس.؛ اين در حالي اس. که گاهي شاهد بارش برف بهاري در استان هستيم با era در اين پژوهش شرايط ديناميکي و ترموديناميکي براي سه بارش فرين برف در فص بهار با استهاده از داده هاي 5 0 درجه تحلي مي شود براي بررسي اقليمي، نابهنجاري هاي دما، بارش و ارتهاع ژئوپتانسيلي یي دورة / تهکيک شبکه اي 26 2030 ( محاسبه شد؛ همچنين کمي. هاي فرارف. تاوايي، شار ریوب. و آب قاب بارش براي دستيابي - آماري 10 ساله ) 3173 به منابع ریوب. مؤثر در ريزش برف در سطح استان بررسي شد تحلي نابهنجاري هاي بارش نشان مي دهد مقدار آنها در همة رويدادهاي بارشي بيش از ميانگين بلندمدت بوده اس. که با نابهنجاري دما و ارتهاع ژئوپتانسي تراز 600 هکتوپاسکال همخواني دارد نتايج نشان داد ریوب. سامانه هاي مطالعه شده بيشتر از درياي سرخ، درياي عرب، درياي عمان و شمال اقيانوس هند تنمين شده و با فرارف. تاوايي مثب. همراه بوده اس. بررسي شرايط ترموديناميکي نيز نشان داد شاخص هاي ناپايداري در ساعات پيش از آغاز بارش مساعد بوده و فعالي. همرفتي سامانه ها را تشديد کرده اس. سرمايش همرفتي همراه با کاهش شديد دما سبب تبدي باران به برف شده اس. کاهش چشمگير دما نسب. به ميانگين بلندمدت و سردبودن ستون جوّ، بارش برف را در فص بهار توجيه مي کند [ABSTRACT FROM AUTHOR]

【Objective】The present paper aimed to explain the changes of hydrothermal resources in the growth period of foxtail millet and maize in Heilongjiang region, and to provide theoretical basis for crop safety production.【Method】Based on the daily weather data from 1957 to 2013 in Raoyang County and Penman-Monteith formula, precipitation anomaly percentage and growth length day（GDD）, this paper analyzed the changes of hydrothermal resources in Raoyang County from June to September.【Result】（i） The size of ET0 was June > July > August > September, and the climatic tendency rates were-5.85,-1.96,-2.59 and-1.46 mm 10 a-1, respectively. The decrease of ET0 in different months was affected by different ten days, June was mainly affected by mid-late days, July was affected by mid-late days, August and September were affected by early and mid-late days, respectively.（ii） The frequency of drought from June to September was 33.33 %, 19.30 %, 31.58 % and 38.6 % respectively. Light drought was dominant in June and July, light drought was dominant in August and moderate drought was dominant in September.（iii）From June to September, the growth degree days were 459.58, 516.49, 470.40 and 301.64 ℃·d, respectively. The climatic tendency rates were 1.19, 3.28, 0.46 and 3.10 ℃·10 a-1, respectively. The increase of growth duration in June and August was affected by the first and middle ten days, July by the first and second ten days, and September by all stages, with the greatest increase in the latter ten days. 【Conclusion】In the future interannual changes, for crops such as millet and maize growing in Heilonggang from June to September, the heat resources were abundant and increasing, but the drought risk will increase in July and August. Therefore, in agricultural production, we should improve the irrigation system in July and August, and strengthen the measures of water conservation and drought resistance in this stage. [ABSTRACT FROM AUTHOR]

We studied the Iran precipitation anomaly in September to November of 2016 and its probable connection with ENSO (El Nino-Southern Oscillation). This period with similar cases in the previous 55 years (1964, 1983, and 1995 according to forecasting center of NOAA) was investigated. In all cases, ENSO changed from strong El-Nino to weak La-Nina after a very brief neutral period. In the following, observational data from 44 synoptic stations of Iran, which have long term statistics about 30 years duration, have been used. Moreover, NCEP-NCAR reanalysis data, which include mean sea level pressure, geopotential height at 850, 500 and 300 hPa, wind and humidity at 850 hPa as well as 300 hPa zonal and meridional winds have been used. Results show that along the establishment of weak La Nina after strong El Nino, autumn rainfall decreases strongly so that severe negative precipitation anomaly (up to 100%) happens in more than 70% of synoptic stations. Besides, atmospheric anomaly patterns in these conditions suggest the development and establishment of a high-pressure system over Iran so that when Siberian high pressure system strengthens, it blocks the passage of precipitation systems reaching Iran and causes cold and dry air mass establishment in the country. Moreover, during these period, extensions of subtropical high over Saudi Arabian, North African high and eastward expansion of Azores high as well as weakening of Iceland low pressure, stop the activity of Mediterranean lowpressure and Sudanese systems. At this time, the transport of moisture has also decreased relative to long term mean. [ABSTRACT FROM AUTHOR]

Forest responses to changes in drought frequency is a critical matter for the future of Amazon forests under climate change, but equally important is the much less studied response to large floods, which may also increase tree mortality and change forest functionality. Further, forest vulnerability to flood is being exacerbated by large hydroelectric dams on Amazon rivers that put upland environments not adapted to flood at unique risk.To address this critical knowledge gap, we evaluated the effects of the extreme 2014 rainfall coupled with the newly constructed Jirau hydroelectric dam on tree survival and forest functionality, in the upper Madeira River basin. We used surveys of campinarana white‐sand forests (stems >1 cm in seven 1 ha plots) conducted before and after the extreme flood to test trait‐based ecological theory predictions of the impact of flood on overall community function.We found that flooding increased mortality by nearly five‐fold (from 3.2% to 15.1%), mostly in smaller trees. This large mortality induced significant and consistent shifts in community function, towards species with conservative life strategies: direct comparison of trait differences between surviving and dying trees showed that survivors had smaller, high density stomata, and higher leaf dry matter content, wood density and root tissue density (RTD). Size and density of stomata and RTD were the most important predictors of species mortality rates.Synthesis and applications. Although focused on a single event in one type of forest, this work highlights the general importance, and need for further study, of interaction between climate change and mega‐dams in Amazon forests. In particular, we expect that continued expansion of hydroelectric dams in Amazonia will likely intensify the impact of large floods on forests made newly vulnerable by these dams, with substantial effect on future forest functionality in expanded floodplain areas across the Basin. Hence, these interaction analyses should be required in the Brazilian legal instruments such as the environmental impact assessments and its accompanying Environmental Impacts Reports for large infrastructure projects in Amazon. [ABSTRACT FROM AUTHOR]

Highlights • A dual-cropping system was presented to address the effects of climate change. • The dual-cropping system in the HP showed variable responses to climate warming. • Phenophases of crop growing period were shortened due to increasing temperature. • Precipitation anomalies induced by ENSO and AAO imposed a negative effect. • Potential risks arise from intensification of water stress and climate extremes. Abstract Challenges for achieving food security with an increasing world population are stimulating many stakeholders to consider the impact of climate change on global-regional crop production. One major concern is how the covariations of climate warming and extremes (e.g., ENSO) affect agricultural systems and production. Here, a dual-cropping system in the Huaihe Plain was used as a testbed to address this issue. We found that climate warming during 1982–2013 has produced remarkable influences on the dual-cropping agricultural system. For the spring season crop (i.e., winter wheat), a significant negative effect was found with a production loss of ˜6.9 × 106 tons due to an elevated T mean (˜2.21 °C) (r =-0.508, p < 0.01), which was associated with water stress. For the summer/autumn crops (i.e., rice and maize), a significant positive effect was found, but with a less substantial production gain (˜1.4 × 106 tons), supposedly due to the relaxed temperature constraints (an increased T max of ˜1.28 °C) for high heat resistant crops (r = 0.495, p < 0.01). The phenophase of the crop growing period was shortened by ˜7 days for the spring crop and by ˜4.4 days for the summer/autumn crops with enhanced thermal conditions. Precipitation anomalies, especially those associated with ENSO turning from El Niño to La Niña, imposed an additional serious impact on the dual-cropping system through decreased precipitation in the spring and increased precipitation in the summer/autumn. Potential impacts for the future could be derived from intensification of water and heat stresses, as well as the climate extremes (e.g., ENSO and AAO). [ABSTRACT FROM AUTHOR]

An anomalous South Asian summer monsoon (SASM) system could generate a large anomaly in precipitation and hydrological disasters in the SASM-prevailing area, as widely reported for the Indian Peninsula. However, how the SASM system influences the precipitation anomaly over the South-Central Tibetan Plateau (SCTP) is largely unknown. In this study, we (a) analyze the influences of the early and late onset (demise) of the SASM on the interannual variations in precipitation over the SCTP during 1979–2015; and (b) illuminate the underlying mechanisms and asymmetric effects with regard to the onset and demise of the SASM by analyzing the characteristics of water vapor transport and moisture budgets in this region. Results indicate that the precipitation anomaly over the SCTP is dominated by the cyclonic and anticyclonic water vapor transport associated with the anomalous SASM activities, causing moisture convergence and divergence in this region. The topographic effect in the southeastern Tibetan Plateau (SETP) and southwestern Tibetan Plateau (SWTP) further strengthens the anomaly in water vapor transport in vertical direction and contributes to the precipitation anomaly through moisture convergence and divergence. The anomalous SASM and topography exhibit asymmetric effects between the onset and demise as well as between the early and late onset (demise) of the SASM. They cause 23.41%, 15.91%, and 1.96% difference in precipitation between the early and late SASM-onset years, and 13.05%, 21.50%, and 29.86% difference in precipitation between the early and late SASM-demise years in the SETP, central Tibetan Plateau (CETP), and SWTP, by regulating the horizontal and vertical thermodynamic and dynamic processes. The results help improve our understanding of the SASM-precipitation relationship over the SCTP and guide the prediction of precipitation and alleviation of water-related disasters in the region and its surroundings that are home to billions of people in Asia.

Tropical cyclones (TCs) are essential elements of the hydrological cycle in tropical and subtropical regions. In the present study, the contribution of TCs to seasonal precipitation around the tropical and subtropical North America is examined. When TC activity over the tropical eastern Pacific (TEP) or the Intra Americas Seas (IAS) is below (above-normal), regional precipitation may be below (above-normal). However, it is not only the number of TCs what may change seasonal precipitation, but the trajectory of the systems. TCs induce intense precipitation over continental regions if they are close enough to shorelines, for instance, if the TC center is located, on average, less than 500 km-distant from the coast. However, if TCs are more remote than this threshold distance, the chances of rain over continental regions decrease, particularly in arid and semi-arid regions. In addition, a distant TC may induce subsidence or produce moisture divergence that inhibits, at least for a few days, convective activity farther away than the threshold distance. An analysis of interannual variability in the TCs that produce precipitation over the tropical and subtropical North America shows that some regions in northern Mexico, which mostly depend on this effect to undergo wet years, may experience seasonal negative anomalies in precipitation if TCs trajectories are remote. Therefore, TCs (activity and trajectories) are important modulators of climate variability on various time scales, either by producing intense rainfall or by inhibiting convection at distant regions from their trajectory. The impact of such variations on water availability in northern Mexico may be relevant, since water availability in dams recovers under the effects of TC rainfall. Seasonal precipitation forecasts or climate change scenarios for these regions should take into account the effect of TCs, if regional adaptation strategies are implemented.

Abstract: The European climate is changing under global warming, and especially the Mediterranean region has been identified as a hot spot for climate change with climate models projecting a reduction in winter rainfall and a very pronounced increase in summertime heat waves. These trends are already detectable over the historic period. Hence, it is beneficial to forecast seasonal droughts well in advance so that water managers and stakeholders can prepare to mitigate deleterious impacts. We developed a new cluster‐based empirical forecast method to predict precipitation anomalies in winter. This algorithm considers not only the strength but also the pattern of the precursors. We compare our algorithm with dynamic forecast models and a canonical correlation analysis‐based prediction method demonstrating that our prediction method performs better in terms of time and pattern correlation in the Mediterranean and European regions. [ABSTRACT FROM AUTHOR]

Monthly relative vorticity and the relative vorticity anomaly at pressure level 850 hPa are computed to study circulation over Southeast Asia associated with the rainfall over Thailand. Monthly mean rainfall is averaged during the years 1979 to 2013 over Thailand to study the trends of rainfall and to analyze the difference between the SSTA in a dry year (1992) and a wet year (1999), and the precipitation anomaly. Rotation of the relative vorticity over Thailand during the rainy season in 1999 is supported by the westerly wind from the Indian Ocean. Relative vorticity over Thailand in October to December are brought by the wind from the east toward the west of the South China Sea. The positive value of relative vorticity in 1992 is less than in 1999. This is consistent with the precipitation anomalies in 1992 and 1999. Clearly, the rainfall and precipitation anomaly over Thailand in wet year 1992 and dry year 1999 are consistent with the relative vorticity at pressure level 850 hPa. Both years are also associated with the SSTA. It can be concluded that the large amounts of rainfall over Thailand are associated with the positive values of relative vorticity at pressure level 850 hPa and SSTA over Southeast Asia. The daily relative vorticity at pressure level 850 hPa and SSTA over Southeast Asia during Typhoon Linda is analyzed in the research. The positive value of relative vorticity is consistent with circulation during Typhoon Linda which is brought by winds from the South China Sea, and the SSTA is also unusual over the Gulf of Thailand and the Andaman Sea. These are the causes of violent storms in Thailand during Typhoon Linda. [ABSTRACT FROM AUTHOR]

The interannual variability of precipitation in El Niño/Southern Oscillation-neutral years was studied for the Centro de Lançamento de Alcântara region. Monthly precipitation, sea surface temperature, wind at 925 hPa and outgoing longwave radiation data from various gridded datasets for the 1951–2010 period (60 years) were used. The data grouping was based on terciles. For the Centro de Lançamento de Alcântara in El Niño/Southern Oscillation- Neutral years, March is the month of the rainy quarter (March to May), when the interhemispheric gradient of the sea surface temperature anomalies over the Atlantic (GRAD)and the atmospheric circulation at 925 hPa over the Centro de Lançamento de Alcântara were able to best explain the variability of precipitation. In this month, the wind direction at 925 hPa was the factor that explained the highest fraction of precipitation variance (40%), followed by GRAD (30%) and the wind magnitude (20%). For the Centro de Lançamento de Alcântara, in general, above-average precipitation was related to weak north-northeasterly low-level winds and southward GRAD, while below-average precipitation was related to strong east-northeasterly low-level winds and northward GRAD.These features were related to an eastward expansion of the Amazon convection towards the northern Northeast Brazil and might be related to a slight southward displacement of the Intertropical Convergence Zone in above-average precipitation years.

The interannual variability of precipitation in El Niño/Southern Oscillation-neutral years was studied for the Centro de Lançamento de Alcântara region. Monthly precipitation, sea surface temperature, wind at 925 hPa and outgoing longwave radiation data from various gridded datasets for the 1951-2010 period (60 years) were used. The data grouping was based on terciles. For the Centro de Lançamento de Alcântara in El Niño/Southern Oscillationneutral years, March is the month of the rainy quarter (March to May) when the interhemispheric gradient of the sea surface temperature anomalies over the Atlantic (GRAD) and the atmospheric circulation at 925 hPa over the Centro de Lançamento de Alcântara were able to best explain the variability of precipitation. In this month, the wind direction at 925 hPa was the factor that explained the highest fraction of precipitation variance (40%), followed by GRAD (30%) and the wind magnitude (20%). For the Centro de Lançamento de Alcântara, in general, above-average precipitation was related to weak north-northeasterly low-level winds and southward GRAD, while below-average precipitation was related to strong east-northeasterly low-level winds and northward GRAD. These features were related to an eastward expansion of the Amazon convection towards the northern Northeast Brazil and might be related to a slight southward displacement of the Intertropical Convergence Zone in above-average precipitation years. [ABSTRACT FROM AUTHOR]

The variation of the East Asian jet stream (EAJS) associated with the Eurasian (EU) teleconnection pattern is investigated using 60-yr NCEP-NCAR daily reanalysis data over the period 1951-2010. The EAJS consists of three components: the polar front jet (PFJ); the plateau subtropical jet (PSJ); and the ocean subtropical jet (OSJ). Of these three jets over East Asia, the EU pattern exhibits a significant influence on the PFJ and OSJ. There is a simultaneous negative correlation between the EU pattern and the PFJ. A significant positive correlation is found between the EU pattern and the OSJ when the EU pattern leads the OSJ by about 5 days. There is no obvious correlation between the EU pattern and the PSJ. The positive EU phase is accompanied by a weakened and poleward-shifted PFJ, which coincides with an intensified OSJ. A possible mechanism for the variation of the EAJS during different EU phases is explored via analyzing the effects of 10-day high-and low-frequency eddy forcing. The zonal wind tendency due to high-frequency eddy forcing contributes to the simultaneous negative correlation between the EU pattern and the PFJ, as well as the northward/southward shift of the PFJ. High- and low-frequency eddy forcing are both responsible for the positive correlation between the EU pattern and the OSJ, but only high-frequency eddy forcing contributes to the lagged variation of the OSJ relative to the EU pattern. The negative correlation between the EU pattern and winter temperature and precipitation anomalies in China is maintained only when the PFJ and OSJ are out of phase with each other. Thus, the EAJS plays an important role in transmitting the EU signal to winter temperature and precipitation anomalies in China. [ABSTRACT FROM AUTHOR]

Abstract: That poverty and mental health are negatively associated in developing countries is well known among epidemiologists. Whether the relationship is causal or associational, however, remains an open question. This paper aims to estimate the causal effect of poverty on mental health by exploiting a natural experiment induced by weather variability across 440 districts in Indonesia (N = 577,548). Precipitation anomaly in two climatological seasons is used as an instrument for poverty status, which is measured using per capita household consumption expenditure. Results of an instrumental variable estimation suggest that poverty causes poor mental health: halving one's consumption expenditure raises the probability of suffering mental illness by 0.06 point; in terms of elasticity, a 1% decrease in consumption brings about 0.62% more symptoms of common mental disorders. This poverty effect is approximately five times stronger than that obtained prior to instrumenting and is robust to alternative distributional assumption, model specification, sample stratification and estimation technique. An individual's mental health is also negatively correlated with district income inequality, suggesting that income distribution may have a significant influence upon mental health over and above the effect of poverty. The findings imply that mental health can be improved not only by influencing individuals' health knowledge and behaviour but also by implementing a more equitable economic policy. [Copyright &y& Elsevier]