Rwanda,a landlocked agricultural country,experienced escalating climate risks since 2013 due to rising June to August(JJA)minimum temperatures(Tmin),harming farming zones,lowering yields,risking health,and threaten-in...Rwanda,a landlocked agricultural country,experienced escalating climate risks since 2013 due to rising June to August(JJA)minimum temperatures(Tmin),harming farming zones,lowering yields,risking health,and threaten-ing economy.This study examined drivers of Rwanda’s 2013 warming anom-aly that severely affected eastern/central lowlands,analyzing circulation changes(1983-2021)using multiple datasets including Enhancing National Climate Services for Rwanda(ENACTS-Rwanda),European Centre for Medium-Range Weather Forecasts Reanalysis 5th Generation(ERA5),and National Oceanic and Atmospheric Administration(NOAA)observations.Methodol-ogies included Empirical Orthogonal Function(EOF)decomposition,Mann-Kendall trend tests,Sen’s slope estimator,and composite analysis to quantify trends and atmospheric linkages.Results showed a significant post-2013 Tmin increase(+0.4˚C to+2.1˚C)exceeding maximum temperature(Tmax)trends.EOF analysis identified a dominant warming mode(72%variance,loadings to+0.872)linked to coupled processes such as increased vertical descending,in-creased 850-hPa specific humidity,increased low-level cloud cover,but re-duced precipitation,which collectively promoted nighttime warming through warm advection.The anomaly was amplified by El Niño-Southern Oscillation(ENSO)-induced Pacific warming and enhanced East African moisture transport.These findings demonstrated how local thermodynamic processes interacted with global climate,forcing them to produce extreme Tmin conditions.The results suggested adaptive strategies,including heat-resistant crop cultivation and optimized water management,could mitigate agricultural impacts.Future research should incorporate these mechanisms into regional climate models while quantifying non-meteorological contributions to observed warming trends,providing critical insights for climate resilience planning in Rwanda and sim-ilar regions.展开更多
Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961–2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in...Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961–2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in eastern China as well as associated external forcing are investigated. Three patterns of the atmospheric circulation are identified, all with quasi-barotropic structures：（1） the East Asia/Pacific（EAP） pattern,（2） the Baikal Lake/Okhotsk Sea（BLOS） pattern, and（3） the eastern China/northern Okhotsk Sea（ECNOS） pattern. The positive EAP pattern significantly increases precipitation over the Yangtze River valley and favors cooling north of the Yangtze River and warming south of the Yangtze River in summer. The warm sea surface temperature anomalies over the tropical Indian Ocean suppress convection over the northwestern subtropical Pacific through the Ekman divergence induced by a Kelvin wave and excite the EAP pattern. The positive BLOS pattern is associated with below-average precipitation south of the Yangtze River and robust cooling over northeastern China. This pattern is triggered by anomalous spring sea ice concentration in the northern Barents Sea. The anomalous sea ice concentration contributes to a Rossby wave activity flux originating from the Greenland Sea, which propagates eastward to North Pacific. The positive ECNOS pattern leads to below-average precipitation and significant warming over northeastern China in summer. The reduced soil moisture associated with the earlier spring snowmelt enhances surface warming over Mongolia and northeastern China and the later spring snowmelt leads to surface cooling over Far East in summer, both of which are responsible for the formation of the ECNOS pattern.展开更多
Persistence is an important property of precipitation and its related impacts. However, changes in persistent precipitation and the possible underlying mechanisms in the context of global warming have not yet been dis...Persistence is an important property of precipitation and its related impacts. However, changes in persistent precipitation and the possible underlying mechanisms in the context of global warming have not yet been discussed in sufficient depth. In this study, the changes in persistent precipitation in summer and related atmospheric circulation patterns over the middle–lower reaches of the Yangtze River(MLRYZR)—a typical monsoon region frequently hit by consecutive rainfall events—are analyzed based on observed daily precipitation and NCEP/NCAR reanalysis data from 1961 to 2019. The results reveal that persistent precipitation events(PPs) tend to happen in a more persistent way, with increased frequency and intensity in the MLRYZR region. Mechanism analyses show that persistent precipitation has happened along with simultaneous enhancement of some large-scale atmospheric circulation patterns,including the Lake Baikal blocking(BB), the Okhotsk Sea blocking(OB), and the western Pacific subtropical high(WPSH). Such enhanced anomalous circulation patterns could persistently reinforce the convergence and supply of water vapor in the MLRYZR region, contributing to the increase in PPs in this region. Based on the above results, we are able to offer some new insights into the long-term changes in precipitation structure and the possible causes. This study is also expected to support attribution studies on regional precipitation changes in the future.展开更多
An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horri...An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horrific wildfires.Here,we use observational data to find the atmospheric circulation variabilities of the North Pacific and Arctic-Pacific-Canada patterns that co-occurred with the development and mature phases of the heatwave,as well as the North America pattern,which coincided with the decaying and eastward movement of the heatwave.Climate models from the Coupled Model Intercomparison Project(Phase 6)are not designed to simulate a particular heatwave event like this one.Still,models show that greenhouse gases are the main reason for the long-term increase of average daily maximum temperature in western North America in the past and future.展开更多
Long-term variations and trends in a wide range of statistics for daily precipitation characteristics in terms of intensity, frequency and duration in Finland were analysed using precipitation records during 1908e2008...Long-term variations and trends in a wide range of statistics for daily precipitation characteristics in terms of intensity, frequency and duration in Finland were analysed using precipitation records during 1908e2008 from 3 meteorological stations in the south(Kaisaniemi),centre(Kajaani) and north(Sodankyl€a). Although precipitation days in northern part were more frequent than in central and southern parts, daily precipitation intensity in the south was generally higher than those in the centre and north of the country. Annual sum of very light precipitation(0 mm < daily precipitation long-term 50 th percentile of daily precipitation more than 0 mm) significantly( p < 0.05) decreased over time,with the highest rate in northern Finland. These decreasing trends might be the result of significant increases in frequency of days with very light precipitation at all the stations, with the highest and lowest rates in northern and southern Finland, respectively. Ratio of annual total precipitation to number of precipitation days also declined in Finland over 1908e2008, with a decreasing north to south gradient. However, annual duration indices of daily precipitation revealed no statistically significant trends at any station. Daily precipitation characteristics showed significant relationships with various well-known atmospheric circulation patterns(ACPs). In particular, the East Atlantic/West Russia(EA/WR)pattern in summer was the most influential ACP negatively associated with different daily precipitation intensity, frequency and duration indices at all three stations studied.展开更多
The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies（SSTAs） over the South Pacific Ocea...The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies（SSTAs） over the South Pacific Ocean（SPO） in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn,not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.展开更多
Based on three reanalysis datasets—ERA-Interim,NCAR–NCEP and JRA-55—the classification of25 commonly used indexes of the East Asian summer monsoon(EASM)was investigated.The physical nature of two categories of mons...Based on three reanalysis datasets—ERA-Interim,NCAR–NCEP and JRA-55—the classification of25 commonly used indexes of the East Asian summer monsoon(EASM)was investigated.The physical nature of two categories of monsoon index,together with their circulation pattern,climate anomalies,and driving factors,were investigated.Results suggest that the selected 25 monsoon indexes can be classified into two typical categories(CategoryⅠandⅡ),which are dominated by interannual and decadal variabilities of the EASM,respectively.The anomalous circulation patterns and summer rainfall patterns related to the two categories of index also exhibit evident differences.CategoryⅠis closely linked to the low-latitude circulation system and the anomalous circulation pattern is a typical East Asia–Pacific teleconnection pattern.The summer rainfall anomaly exhibits a typical tripole pattern.However,CategoryⅡmainly reflects the impacts of the middle–high latitude circulation system on the summer monsoon and is closely linked to a typical Eurasian teleconnection pattern,which corresponds to a dipole of summer rainfall anomalies.Further analysis suggests that the underlying thermal driving factors of the two categories of monsoon are distinct.The main driving factors of CategoryⅠare the tropical sea surface temperature anomalies(SSTAs),especially ENSO-related SSTAs in the preceding winter and summer SSTAs in the tropical Indian Ocean.The winter signal of Category II summer monsoon anomalous activity mainly originates from the polar region and the middle and high latitudes of the Eurasian continent.CategoryⅡmonsoon activity is also associated with summer SSTAs in the equatorial central Pacific.展开更多
The southeastern Tibetan Plateau(SETP)is the preeminent summer heavy precipitation region within the Tibetan Plateau(TP).However,the large-scale circulation types and dynamics driving summer heavy precipitation in the...The southeastern Tibetan Plateau(SETP)is the preeminent summer heavy precipitation region within the Tibetan Plateau(TP).However,the large-scale circulation types and dynamics driving summer heavy precipitation in the SETP remain inadequately elucidated.Using the hierarchical clustering method,two distinctive atmospheric circulation patterns associated with heavy precipitation were identified:the Tibetan Plateau vortex type(TPVT,constituting 56.6%of the events)and the mid-latitude trough type(MLTT,43.4%).A comprehensive examination of the two atmospheric circulation patterns reveals a clear nexus between the occurrences of summer heavy precipitation and positive vorticity anomalies,moisture convergence,as well as the southeastward displacement of the westerly jet core.Specifically,TPVT events are characterized by the eastward and dry-to-wet potential vorticity progression processes,while MLTT events are linked to the intrusion of a deep extratropical trough into the SETP.This study advances our understanding of the complex mechanisms governing the summer heavy precipitation in the SETP,shedding light on critical meteorological processes in the region.展开更多
The evolution of daily synoptic weather patterns is the main driver of day-to-day weather change. These patterns are generally associated with changes in temperature, precipitation, etc., especially during extreme wea...The evolution of daily synoptic weather patterns is the main driver of day-to-day weather change. These patterns are generally associated with changes in temperature, precipitation, etc., especially during extreme weathers. Evaluating the ability of climate models to reproduce the frequency and intensity of daily synoptic patterns is essential for increasing confidence in future projections. In this study, we investigated the ability of 34 global climate models （GCMs） included in the Coupled Model Intercomparison Project Phase 5 （CMIP5） to simulate synoptic patterns over East Asia and their evolution features in winter and summer. Daily synoptic patterns in sea level pressure and their occurrence frequencies were identified by using an objective clustering algorithm, self-organizing maps （SOMs）. The evaluation consists of correlating the frequencies of these patterns in the 34 CMIP5 models with the frequencies in the NCEP reanalysis during the baseline period of 1980-1999. The results illustrated that most of these models were able to reproduce the synoptic patterns of the NCEP reanalysis. In addition, the frequencies of temporal sea level pressure （SLP） anomaly patterns were reproduced by most of the models over the baseline period, but the frequencies of spatial SLP anomaly patterns were only reproduced by a few GCMs. Overall, the models performed better in summer than in winter. Comprehensive evaluation shows that the four top-performing models for both winter and summer are bcc-csml-l-m, NorESM1-M, MRI-CGCM3, and CCSM4. They show good performance in simulating the daily synoptic patterns in SLP and in reproducing their occurrence frequencies. The results showed that the SOM was an effective tool for differentiating characteristics of synoptic circulation patterns and for evaluating the ability of climate models to simulate the frequency of daily synoptic patterns. The results can also help users to choose a better model for future climate projection and downscaling over East Asia.展开更多
文摘Rwanda,a landlocked agricultural country,experienced escalating climate risks since 2013 due to rising June to August(JJA)minimum temperatures(Tmin),harming farming zones,lowering yields,risking health,and threaten-ing economy.This study examined drivers of Rwanda’s 2013 warming anom-aly that severely affected eastern/central lowlands,analyzing circulation changes(1983-2021)using multiple datasets including Enhancing National Climate Services for Rwanda(ENACTS-Rwanda),European Centre for Medium-Range Weather Forecasts Reanalysis 5th Generation(ERA5),and National Oceanic and Atmospheric Administration(NOAA)observations.Methodol-ogies included Empirical Orthogonal Function(EOF)decomposition,Mann-Kendall trend tests,Sen’s slope estimator,and composite analysis to quantify trends and atmospheric linkages.Results showed a significant post-2013 Tmin increase(+0.4˚C to+2.1˚C)exceeding maximum temperature(Tmax)trends.EOF analysis identified a dominant warming mode(72%variance,loadings to+0.872)linked to coupled processes such as increased vertical descending,in-creased 850-hPa specific humidity,increased low-level cloud cover,but re-duced precipitation,which collectively promoted nighttime warming through warm advection.The anomaly was amplified by El Niño-Southern Oscillation(ENSO)-induced Pacific warming and enhanced East African moisture transport.These findings demonstrated how local thermodynamic processes interacted with global climate,forcing them to produce extreme Tmin conditions.The results suggested adaptive strategies,including heat-resistant crop cultivation and optimized water management,could mitigate agricultural impacts.Future research should incorporate these mechanisms into regional climate models while quantifying non-meteorological contributions to observed warming trends,providing critical insights for climate resilience planning in Rwanda and sim-ilar regions.
基金Supported by the National Natural Science Foundation of China(41530531,41675092,and 41305056)China Meteorological Administration Special Public Welfare Research Fund(GYHY201506001)
文摘Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961–2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in eastern China as well as associated external forcing are investigated. Three patterns of the atmospheric circulation are identified, all with quasi-barotropic structures：（1） the East Asia/Pacific（EAP） pattern,（2） the Baikal Lake/Okhotsk Sea（BLOS） pattern, and（3） the eastern China/northern Okhotsk Sea（ECNOS） pattern. The positive EAP pattern significantly increases precipitation over the Yangtze River valley and favors cooling north of the Yangtze River and warming south of the Yangtze River in summer. The warm sea surface temperature anomalies over the tropical Indian Ocean suppress convection over the northwestern subtropical Pacific through the Ekman divergence induced by a Kelvin wave and excite the EAP pattern. The positive BLOS pattern is associated with below-average precipitation south of the Yangtze River and robust cooling over northeastern China. This pattern is triggered by anomalous spring sea ice concentration in the northern Barents Sea. The anomalous sea ice concentration contributes to a Rossby wave activity flux originating from the Greenland Sea, which propagates eastward to North Pacific. The positive ECNOS pattern leads to below-average precipitation and significant warming over northeastern China in summer. The reduced soil moisture associated with the earlier spring snowmelt enhances surface warming over Mongolia and northeastern China and the later spring snowmelt leads to surface cooling over Far East in summer, both of which are responsible for the formation of the ECNOS pattern.
基金Supported by the National Natural Science Foundation of China(41905083)National Key Research and Development Program of China(2018YFC1507700).
文摘Persistence is an important property of precipitation and its related impacts. However, changes in persistent precipitation and the possible underlying mechanisms in the context of global warming have not yet been discussed in sufficient depth. In this study, the changes in persistent precipitation in summer and related atmospheric circulation patterns over the middle–lower reaches of the Yangtze River(MLRYZR)—a typical monsoon region frequently hit by consecutive rainfall events—are analyzed based on observed daily precipitation and NCEP/NCAR reanalysis data from 1961 to 2019. The results reveal that persistent precipitation events(PPs) tend to happen in a more persistent way, with increased frequency and intensity in the MLRYZR region. Mechanism analyses show that persistent precipitation has happened along with simultaneous enhancement of some large-scale atmospheric circulation patterns,including the Lake Baikal blocking(BB), the Okhotsk Sea blocking(OB), and the western Pacific subtropical high(WPSH). Such enhanced anomalous circulation patterns could persistently reinforce the convergence and supply of water vapor in the MLRYZR region, contributing to the increase in PPs in this region. Based on the above results, we are able to offer some new insights into the long-term changes in precipitation structure and the possible causes. This study is also expected to support attribution studies on regional precipitation changes in the future.
基金supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0306)National Natural Science Foundation of China (Grant Nos. 41731173 and 42192564)+5 种基金National Key R&D Program of China (2019YFA0606701)Strategic Priority Research Program of Chinese Academy of Sciences (XDB42000000 and XDA20060502)Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences (ISEE2021ZD01)Independent Research Project Program of State Key Laboratory of Tropical Oceanography (Grand No. LTOZZ2004)Leading Talents of Guangdong Province Programsupported by the High Performance Computing Division in the South China Sea Institute of Oceanology
文摘An extraordinary and unprecedented heatwave swept across western North America(i.e.,the Pacific Northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horrific wildfires.Here,we use observational data to find the atmospheric circulation variabilities of the North Pacific and Arctic-Pacific-Canada patterns that co-occurred with the development and mature phases of the heatwave,as well as the North America pattern,which coincided with the decaying and eastward movement of the heatwave.Climate models from the Coupled Model Intercomparison Project(Phase 6)are not designed to simulate a particular heatwave event like this one.Still,models show that greenhouse gases are the main reason for the long-term increase of average daily maximum temperature in western North America in the past and future.
基金the Finnish Cultural Foundation and Maa-ja vesitekniikan tuki r.y. (MVTT, 29188) for funding this researchsupported by Swedish VR, BECC and MERGE programs
文摘Long-term variations and trends in a wide range of statistics for daily precipitation characteristics in terms of intensity, frequency and duration in Finland were analysed using precipitation records during 1908e2008 from 3 meteorological stations in the south(Kaisaniemi),centre(Kajaani) and north(Sodankyl€a). Although precipitation days in northern part were more frequent than in central and southern parts, daily precipitation intensity in the south was generally higher than those in the centre and north of the country. Annual sum of very light precipitation(0 mm < daily precipitation long-term 50 th percentile of daily precipitation more than 0 mm) significantly( p < 0.05) decreased over time,with the highest rate in northern Finland. These decreasing trends might be the result of significant increases in frequency of days with very light precipitation at all the stations, with the highest and lowest rates in northern and southern Finland, respectively. Ratio of annual total precipitation to number of precipitation days also declined in Finland over 1908e2008, with a decreasing north to south gradient. However, annual duration indices of daily precipitation revealed no statistically significant trends at any station. Daily precipitation characteristics showed significant relationships with various well-known atmospheric circulation patterns(ACPs). In particular, the East Atlantic/West Russia(EA/WR)pattern in summer was the most influential ACP negatively associated with different daily precipitation intensity, frequency and duration indices at all three stations studied.
基金jointly supported by the Special Fund for Public Welfare Industry (meteorology) (Grant No. GYHY201306026)the National Natural Science Foundation of China (Grant Nos. 41421004 and 41522503)
文摘The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies（SSTAs） over the South Pacific Ocean（SPO） in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn,not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.
基金supported by the National Natural Science Foundation of China [grant number 41625019]
文摘Based on three reanalysis datasets—ERA-Interim,NCAR–NCEP and JRA-55—the classification of25 commonly used indexes of the East Asian summer monsoon(EASM)was investigated.The physical nature of two categories of monsoon index,together with their circulation pattern,climate anomalies,and driving factors,were investigated.Results suggest that the selected 25 monsoon indexes can be classified into two typical categories(CategoryⅠandⅡ),which are dominated by interannual and decadal variabilities of the EASM,respectively.The anomalous circulation patterns and summer rainfall patterns related to the two categories of index also exhibit evident differences.CategoryⅠis closely linked to the low-latitude circulation system and the anomalous circulation pattern is a typical East Asia–Pacific teleconnection pattern.The summer rainfall anomaly exhibits a typical tripole pattern.However,CategoryⅡmainly reflects the impacts of the middle–high latitude circulation system on the summer monsoon and is closely linked to a typical Eurasian teleconnection pattern,which corresponds to a dipole of summer rainfall anomalies.Further analysis suggests that the underlying thermal driving factors of the two categories of monsoon are distinct.The main driving factors of CategoryⅠare the tropical sea surface temperature anomalies(SSTAs),especially ENSO-related SSTAs in the preceding winter and summer SSTAs in the tropical Indian Ocean.The winter signal of Category II summer monsoon anomalous activity mainly originates from the polar region and the middle and high latitudes of the Eurasian continent.CategoryⅡmonsoon activity is also associated with summer SSTAs in the equatorial central Pacific.
基金Second Tibetan Plateau Scientific Expedition,Research(STEP)Programme(2019QZKK0105)National Natural Science Foundation of China(U2442213,42122033,42475002 and 42075006).
文摘The southeastern Tibetan Plateau(SETP)is the preeminent summer heavy precipitation region within the Tibetan Plateau(TP).However,the large-scale circulation types and dynamics driving summer heavy precipitation in the SETP remain inadequately elucidated.Using the hierarchical clustering method,two distinctive atmospheric circulation patterns associated with heavy precipitation were identified:the Tibetan Plateau vortex type(TPVT,constituting 56.6%of the events)and the mid-latitude trough type(MLTT,43.4%).A comprehensive examination of the two atmospheric circulation patterns reveals a clear nexus between the occurrences of summer heavy precipitation and positive vorticity anomalies,moisture convergence,as well as the southeastward displacement of the westerly jet core.Specifically,TPVT events are characterized by the eastward and dry-to-wet potential vorticity progression processes,while MLTT events are linked to the intrusion of a deep extratropical trough into the SETP.This study advances our understanding of the complex mechanisms governing the summer heavy precipitation in the SETP,shedding light on critical meteorological processes in the region.
基金Supported by the National Natural Science Foundation of China(41230528 and 41205162)National(Key)Basic Research and Development(973)Program of China(2012CB955204)Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The evolution of daily synoptic weather patterns is the main driver of day-to-day weather change. These patterns are generally associated with changes in temperature, precipitation, etc., especially during extreme weathers. Evaluating the ability of climate models to reproduce the frequency and intensity of daily synoptic patterns is essential for increasing confidence in future projections. In this study, we investigated the ability of 34 global climate models （GCMs） included in the Coupled Model Intercomparison Project Phase 5 （CMIP5） to simulate synoptic patterns over East Asia and their evolution features in winter and summer. Daily synoptic patterns in sea level pressure and their occurrence frequencies were identified by using an objective clustering algorithm, self-organizing maps （SOMs）. The evaluation consists of correlating the frequencies of these patterns in the 34 CMIP5 models with the frequencies in the NCEP reanalysis during the baseline period of 1980-1999. The results illustrated that most of these models were able to reproduce the synoptic patterns of the NCEP reanalysis. In addition, the frequencies of temporal sea level pressure （SLP） anomaly patterns were reproduced by most of the models over the baseline period, but the frequencies of spatial SLP anomaly patterns were only reproduced by a few GCMs. Overall, the models performed better in summer than in winter. Comprehensive evaluation shows that the four top-performing models for both winter and summer are bcc-csml-l-m, NorESM1-M, MRI-CGCM3, and CCSM4. They show good performance in simulating the daily synoptic patterns in SLP and in reproducing their occurrence frequencies. The results showed that the SOM was an effective tool for differentiating characteristics of synoptic circulation patterns and for evaluating the ability of climate models to simulate the frequency of daily synoptic patterns. The results can also help users to choose a better model for future climate projection and downscaling over East Asia.
