Based on the statistical method and the historical evolution of meteorological sta- tions, the temperature time series for each station in Hunan Province during 1910-2014 are tested for their homogeneity and then corr...Based on the statistical method and the historical evolution of meteorological sta- tions, the temperature time series for each station in Hunan Province during 1910-2014 are tested for their homogeneity and then corrected. The missing data caused by war and other reasons at the 8 meteorological stations which had records before 1950 is filled by interpola- tion using adjacent observations, and complete temperature time series since the estab- lishment of stations are constructed. After that, according to the representative analysis of each station in different time periods, the temperature series of Hunan Province during 1910-2014 are built and their changes are analyzed. The results indicate that the annual mean temperature has a significant warming trend during 1910-2014 and the seasonal mean temperature has the largest rising amplitude in winter and spring, followed by autumn, but no significant change in summer. Temperature variation over Hunan Province has several sig- nificant warm-cold alternations and more frequent than that in whole China. Annual and seasonal mean temperatures except summer and autumn have abrupt warming changes in the recent 100 years. The wavelet analysis suggests that the annual and four seasonal mean temperatures in recent 100 years have experienced two climatic shifts from cold to warm.展开更多
Based on the collection and processing of the China national-wide monthly station observational precipitation data in 1900-2009, the data series for each station has been tested for their homogeneity with the Standard...Based on the collection and processing of the China national-wide monthly station observational precipitation data in 1900-2009, the data series for each station has been tested for their homogeneity with the Standard Normalized Homogeneity Test （SNHT） method and the inhomogeneous parts of the series are adjusted or corrected. Based on the data, the precipitation anomalies during 1900-2009 and the climatology normals during 1971-2000 have been transformed into the grid boxes at 5°×5° and 2°×2° resolutions respectively. And two grid form datasets are constructed by combining the normal and anomalies. After that, the missing values for the 5°×5° grid dataset are interpolated by Empirical Orthogonal Function （EOF） techniques. With the datasets of different resolutions, the precipitation change series during 1900-2009 over China's Mainland are built, and the annual and seasonal precipitation trends for the recent 110 years are analyzed. The result indicates that the annual precipitation shows a slight dryer trend during the past 110 years, notwithstanding lack of statistical confidence. It is worth noting that after the interpolation of the missing values, the annual precipitation amounts in the early 1900s become less, which increases the changing trend of the annual precipitation in China for the whole 110 years slightly （from -7.48 mm/100a to -6.48 mm/100a）.展开更多
Based on the daily regional mean rainfall,the Z-index method is used to identify persistent flood and drought events lasting for at least 10 days over a region where Dongting Lake and Poyang Lake sit(referred to as th...Based on the daily regional mean rainfall,the Z-index method is used to identify persistent flood and drought events lasting for at least 10 days over a region where Dongting Lake and Poyang Lake sit(referred to as the"two-lake region"hereafter).The National Centers for Environmental Prediction(NCEP)reanalysis data are then utilized to perform a preliminary diagnostic analysis on these events.The results indicate that the composite standardized geopotential height at 500 hPa presents two different meridional wave trains from north to south over the East Asian-Pacific region,i.e.,a"-+-"pattern for the droughts and a"+-+"pattern for the floods,respectively.The developing,maintaining and decaying phases in the drought and flood events are closely related to the intensity and location of a subtropical high and an extra-tropical blocking high.It is shown that the East Asian summer monsoon is strong(weak)with the occurrence of persistent drought(flood)events.Droughts(floods)are accompanied by a weak(strong)tropical convergent system and a strong(weak)subtropical convergent system.Furthermore,the persistent drought(flood)events are associated with a divergence(convergence)of vertically integrated water vapor flux.In the vertical profile of water vapor flux,divergence(convergence)in the mid-and lower-levels and convergence(divergence)in the higher levels are evident in the droughts(floods).Both the divergence in the droughts and the convergence in floods are strongest at 850 hPa.展开更多
In recent years, the phenomenon of a critical slowing down has demonstrated its major potential in discovering whether a complex dynamic system tends to abruptly change at critical points. This research on the Pacific...In recent years, the phenomenon of a critical slowing down has demonstrated its major potential in discovering whether a complex dynamic system tends to abruptly change at critical points. This research on the Pacific decadal oscillation(PDO) index has been made on the basis of the critical slowing down principle in order to analyze its early warning signal of abrupt change. The chaotic characteristics of the PDO index sequence at different times are determined by using the largest Lyapunov exponent(LLE). The relationship between the regional sea surface temperature(SST) background field and the early warning signal of the PDO abrupt change is further studied through calculating the variance of the SST in the PDO region and the spatial distribution of the autocorrelation coefficient, thereby providing the experimental foundation for the extensive application of the method of the critical slowing down phenomenon. Our results show that the phenomenon of critical slowing down, such as the increase of the variance and autocorrelation coefficient, will continue for six years before the abrupt change of the PDO index. This phenomenon of the critical slowing down can be regarded as one of the early warning signals of an abrupt change. Through calculating the LLE of the PDO index during different times, it is also found that the strongest chaotic characteristics of the system occurred between 1971 and 1975 in the early stages of an abrupt change(1976), and the system was at the stage of a critical slowing down, which proves the reliability of the early warning signal of abrupt change discovered in 1970 from the mechanism. In addition, the variance of the SST,along with the spatial distribution of the autocorrelation coefficient in the corresponding PDO region, also demonstrates the corresponding relationship between the change of the background field of the SST and the change of the PDO.展开更多
[Objective] The aim was to picture choroplethic map through VB and Surfer techniques. [Method] Taking the way to depict many kinds of choroplethic map through VB and Surfer techniques as an example, methods to realize...[Objective] The aim was to picture choroplethic map through VB and Surfer techniques. [Method] Taking the way to depict many kinds of choroplethic map through VB and Surfer techniques as an example, methods to realize data process, system protection and programming through ActiveX control under VB 6.0 programming environment. [Result] In the development of 'Hunan Modern Agricultural Meteorological Business Service Comprehensive Platform', because of different requirements, the workload was large, but picture and data was isolated by dint of ActiveX control, which improved the software efficiency. [Conclusion] The study solved the problems such as programming workload reduction, code utilization efficiency improvement and software interface.展开更多
In 2018,China experienced the hottest summer since 1961.The maximum,mean,and minimum temperatures all reached the highest.Air temperatures in most regions were much higher than normal;in northern China especially,the ...In 2018,China experienced the hottest summer since 1961.The maximum,mean,and minimum temperatures all reached the highest.Air temperatures in most regions were much higher than normal;in northern China especially,the temperature anomalies were above double of the standard deviations.Consistent variations of temperature anomalies appeared in the national mean and in northern China on different timescales from intraseasonal to annual,indicating that the above normal temperature in northern China contributed significantly to the record-breaking hot summer of entire China.Relationships among the high temperature in summer 2018,the tropospheric circulation,and the global sea surface temperatures(SSTs)are further analyzed.It is found that the intensified and more northward western Pacific subtropical high(WPSH),weakened Northeast China cold vortex(NECV),and positive geopotential height anomaly from northern China to the Sea of Japan resulted in the abnormally high temperature in summer 2018.From late July to mid August,the WPSH was stronger than normal,with its ridge line jumping to north of 40°N;meanwhile,the NECV was much weaker and more northward than normal;both of the two systems led to the persistent high temperature in northern China during this period.In addition,the SSTs in Kuroshio and its extension area(K–KE)in summer 2018 were also the highest since 1961 and the greatest positive SST anomaly in K–KE was favorable for the above normal geopotential height over North China–Northeast China–Japan at 500 hPa,giving rise to the exceptionally high temperature in northern China.展开更多
基金China Meteorological Administration Special Public Welfare Research Fund,GYHY201406016
文摘Based on the statistical method and the historical evolution of meteorological sta- tions, the temperature time series for each station in Hunan Province during 1910-2014 are tested for their homogeneity and then corrected. The missing data caused by war and other reasons at the 8 meteorological stations which had records before 1950 is filled by interpola- tion using adjacent observations, and complete temperature time series since the estab- lishment of stations are constructed. After that, according to the representative analysis of each station in different time periods, the temperature series of Hunan Province during 1910-2014 are built and their changes are analyzed. The results indicate that the annual mean temperature has a significant warming trend during 1910-2014 and the seasonal mean temperature has the largest rising amplitude in winter and spring, followed by autumn, but no significant change in summer. Temperature variation over Hunan Province has several sig- nificant warm-cold alternations and more frequent than that in whole China. Annual and seasonal mean temperatures except summer and autumn have abrupt warming changes in the recent 100 years. The wavelet analysis suggests that the annual and four seasonal mean temperatures in recent 100 years have experienced two climatic shifts from cold to warm.
基金State Key Development Program of Basic Research of China,No.2010CB951600National Science and Technology Supporting Program of the 11th and 12th Five-Year Plan Periods,No.2007BAC29B01+2 种基金 No.2012BAC22B00China Meteorological Administration Special Foundation for Climate Change, No.CCSF201224No.540000G010C01
文摘Based on the collection and processing of the China national-wide monthly station observational precipitation data in 1900-2009, the data series for each station has been tested for their homogeneity with the Standard Normalized Homogeneity Test （SNHT） method and the inhomogeneous parts of the series are adjusted or corrected. Based on the data, the precipitation anomalies during 1900-2009 and the climatology normals during 1971-2000 have been transformed into the grid boxes at 5°×5° and 2°×2° resolutions respectively. And two grid form datasets are constructed by combining the normal and anomalies. After that, the missing values for the 5°×5° grid dataset are interpolated by Empirical Orthogonal Function （EOF） techniques. With the datasets of different resolutions, the precipitation change series during 1900-2009 over China's Mainland are built, and the annual and seasonal precipitation trends for the recent 110 years are analyzed. The result indicates that the annual precipitation shows a slight dryer trend during the past 110 years, notwithstanding lack of statistical confidence. It is worth noting that after the interpolation of the missing values, the annual precipitation amounts in the early 1900s become less, which increases the changing trend of the annual precipitation in China for the whole 110 years slightly （from -7.48 mm/100a to -6.48 mm/100a）.
基金China Meteorological Administration for the R&D Special Fund for Public Welfare Industry(Meteorology)(GYHY201306016)
文摘Based on the daily regional mean rainfall,the Z-index method is used to identify persistent flood and drought events lasting for at least 10 days over a region where Dongting Lake and Poyang Lake sit(referred to as the"two-lake region"hereafter).The National Centers for Environmental Prediction(NCEP)reanalysis data are then utilized to perform a preliminary diagnostic analysis on these events.The results indicate that the composite standardized geopotential height at 500 hPa presents two different meridional wave trains from north to south over the East Asian-Pacific region,i.e.,a"-+-"pattern for the droughts and a"+-+"pattern for the floods,respectively.The developing,maintaining and decaying phases in the drought and flood events are closely related to the intensity and location of a subtropical high and an extra-tropical blocking high.It is shown that the East Asian summer monsoon is strong(weak)with the occurrence of persistent drought(flood)events.Droughts(floods)are accompanied by a weak(strong)tropical convergent system and a strong(weak)subtropical convergent system.Furthermore,the persistent drought(flood)events are associated with a divergence(convergence)of vertically integrated water vapor flux.In the vertical profile of water vapor flux,divergence(convergence)in the mid-and lower-levels and convergence(divergence)in the higher levels are evident in the droughts(floods).Both the divergence in the droughts and the convergence in floods are strongest at 850 hPa.
基金supported by the National Natural Science Foundation of China(Grant Nos.41175067 and 41305056)the National Basic Research Program of China(Grant No.2012CB955901)+1 种基金the Special Scientific Research Project for Public Interest of China(Grant No.GYHY201506001)the Special Fund for Climate Change of China Meteorological Administration(Grant No.CCSF201525)
文摘In recent years, the phenomenon of a critical slowing down has demonstrated its major potential in discovering whether a complex dynamic system tends to abruptly change at critical points. This research on the Pacific decadal oscillation(PDO) index has been made on the basis of the critical slowing down principle in order to analyze its early warning signal of abrupt change. The chaotic characteristics of the PDO index sequence at different times are determined by using the largest Lyapunov exponent(LLE). The relationship between the regional sea surface temperature(SST) background field and the early warning signal of the PDO abrupt change is further studied through calculating the variance of the SST in the PDO region and the spatial distribution of the autocorrelation coefficient, thereby providing the experimental foundation for the extensive application of the method of the critical slowing down phenomenon. Our results show that the phenomenon of critical slowing down, such as the increase of the variance and autocorrelation coefficient, will continue for six years before the abrupt change of the PDO index. This phenomenon of the critical slowing down can be regarded as one of the early warning signals of an abrupt change. Through calculating the LLE of the PDO index during different times, it is also found that the strongest chaotic characteristics of the system occurred between 1971 and 1975 in the early stages of an abrupt change(1976), and the system was at the stage of a critical slowing down, which proves the reliability of the early warning signal of abrupt change discovered in 1970 from the mechanism. In addition, the variance of the SST,along with the spatial distribution of the autocorrelation coefficient in the corresponding PDO region, also demonstrates the corresponding relationship between the change of the background field of the SST and the change of the PDO.
文摘[Objective] The aim was to picture choroplethic map through VB and Surfer techniques. [Method] Taking the way to depict many kinds of choroplethic map through VB and Surfer techniques as an example, methods to realize data process, system protection and programming through ActiveX control under VB 6.0 programming environment. [Result] In the development of 'Hunan Modern Agricultural Meteorological Business Service Comprehensive Platform', because of different requirements, the workload was large, but picture and data was isolated by dint of ActiveX control, which improved the software efficiency. [Conclusion] The study solved the problems such as programming workload reduction, code utilization efficiency improvement and software interface.
基金Supported by the National Key Research and Development Program of China(2018YFC1505603)National Science and Technology Support Program of China(2015BAC03B04)+2 种基金Youth Talent Development Program of China Meteorological Administration(CMA)National Natural Science Foundation of China(41205039 and 41776039)Forecasters’ Project of CMA(CMAYBY2019-149)
文摘In 2018,China experienced the hottest summer since 1961.The maximum,mean,and minimum temperatures all reached the highest.Air temperatures in most regions were much higher than normal;in northern China especially,the temperature anomalies were above double of the standard deviations.Consistent variations of temperature anomalies appeared in the national mean and in northern China on different timescales from intraseasonal to annual,indicating that the above normal temperature in northern China contributed significantly to the record-breaking hot summer of entire China.Relationships among the high temperature in summer 2018,the tropospheric circulation,and the global sea surface temperatures(SSTs)are further analyzed.It is found that the intensified and more northward western Pacific subtropical high(WPSH),weakened Northeast China cold vortex(NECV),and positive geopotential height anomaly from northern China to the Sea of Japan resulted in the abnormally high temperature in summer 2018.From late July to mid August,the WPSH was stronger than normal,with its ridge line jumping to north of 40°N;meanwhile,the NECV was much weaker and more northward than normal;both of the two systems led to the persistent high temperature in northern China during this period.In addition,the SSTs in Kuroshio and its extension area(K–KE)in summer 2018 were also the highest since 1961 and the greatest positive SST anomaly in K–KE was favorable for the above normal geopotential height over North China–Northeast China–Japan at 500 hPa,giving rise to the exceptionally high temperature in northern China.
