ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Volume 39,Issue 9,2013 Table of Contents
2013, 39(9):1089-1095.
DOI: 10.7519/j.issn.1000-0526.2013.09.001
Abstract:
During June-August 2010, significant circumglobal teleconnections existed in the Northern Hemisphere which originated from the negative disturbance around the exit of upper level jet stream over the Atlantic. The disturbance propagated downstream along the teleconnection wave train, causing Russian heat wave, heavy rains and floods in Pakistan and northwestern and northeastern China. The teleconnection analysis shows that the negative disturbance firstly caused positive perturbation and the development of blocking high in western Russia, resulting in persisting high temperature and drought. Secondly, the negative disturbance propagated to northern West Asia, causing cold air to move southward and meet the northward and westward Indian summer monsoons in northern Pakistan and produced torrential rains. In early August, the disturbance continued to propagate downstream along the upper level jet stream over Asia, causing floods in northwestern and northeastern China and the Korea Peninsula. The sudden rain storm and landslide in Zhouqu, Gansu Province and the extremely heavy rain in Songhuajiang River region occurred just in this stage. The meridional circulation over the Eurasia developed exceptionally during 2010 summer and the meridional cell of the upper level jet stream was great, causing cold air from high latitudes and warm air from low latitudes to interact continuously. This induced the establishing, strengthening, and maintaining of high latitude blocking high in western Russian, and low latitude severe floods in Pakistan and rainstorm in mid latitudes of China. Monsoons acted as a key factor for the heavy rains and floods with the display of interaction of two warm and humid air flows from the Arabian Sea and Bay of Bengal and the southward cold air flow along the blocking high over northern Pakistan, as well as the interaction of warm and humid air flows from the Indian Ocean and the Pacific and the moisture from westerlies over northeastern China and the Korea Peninsula.
During June-August 2010, significant circumglobal teleconnections existed in the Northern Hemisphere which originated from the negative disturbance around the exit of upper level jet stream over the Atlantic. The disturbance propagated downstream along the teleconnection wave train, causing Russian heat wave, heavy rains and floods in Pakistan and northwestern and northeastern China. The teleconnection analysis shows that the negative disturbance firstly caused positive perturbation and the development of blocking high in western Russia, resulting in persisting high temperature and drought. Secondly, the negative disturbance propagated to northern West Asia, causing cold air to move southward and meet the northward and westward Indian summer monsoons in northern Pakistan and produced torrential rains. In early August, the disturbance continued to propagate downstream along the upper level jet stream over Asia, causing floods in northwestern and northeastern China and the Korea Peninsula. The sudden rain storm and landslide in Zhouqu, Gansu Province and the extremely heavy rain in Songhuajiang River region occurred just in this stage. The meridional circulation over the Eurasia developed exceptionally during 2010 summer and the meridional cell of the upper level jet stream was great, causing cold air from high latitudes and warm air from low latitudes to interact continuously. This induced the establishing, strengthening, and maintaining of high latitude blocking high in western Russian, and low latitude severe floods in Pakistan and rainstorm in mid latitudes of China. Monsoons acted as a key factor for the heavy rains and floods with the display of interaction of two warm and humid air flows from the Arabian Sea and Bay of Bengal and the southward cold air flow along the blocking high over northern Pakistan, as well as the interaction of warm and humid air flows from the Indian Ocean and the Pacific and the moisture from westerlies over northeastern China and the Korea Peninsula.
2013, 39(9):1096-1102.
DOI: 10.7519/j.issn.1000-0526.2013.09.002
Abstract:
Using the NCEP/NCAR global daily reanalysis data, this paper defined the winter pentad Eurasian teleconnection persistent anomaly, analyzed the characteristics of persistent abnormal process of EU pattern and discussed the corresponding atmospheric circulation and its impact on the winter weather in China. Statistical results show that: 26 persistent abnormal processes occur in the 54 winters of 1957-2010. The positive persistent abnormal processes mainly occur in December, the 2nd to the 5th pentad of January, and the 4th pentad of February to the 1st pentad of March while the negative ones occur in the 4th and 5th pentads of December, the first three pentads of January and the 3rd pentad of February to the 1st pentad of March. Then the 200 hPa and 850 hPa geopotential height fields are selected to represent high and low atmospheric layers. Synthetic analysis shows that: during the processes of index anomalies, characteristics of strong EU pattern exists in both of the high and low atmospheric layers; and temperature in most parts of China is influenced by EU index anomalies, showing significant difference. Precipitation presents significant difference in the middle and lower reaches of the Yellow River and Yangtze River, and parts of southeastern China. During positive abnormal processes, influenced by the strengthened Siberian high, northerly winds prevail in the lower troposphere over China with lower temperature and less rainfalls. The opposite situation tends to occur in negative processes.
Using the NCEP/NCAR global daily reanalysis data, this paper defined the winter pentad Eurasian teleconnection persistent anomaly, analyzed the characteristics of persistent abnormal process of EU pattern and discussed the corresponding atmospheric circulation and its impact on the winter weather in China. Statistical results show that: 26 persistent abnormal processes occur in the 54 winters of 1957-2010. The positive persistent abnormal processes mainly occur in December, the 2nd to the 5th pentad of January, and the 4th pentad of February to the 1st pentad of March while the negative ones occur in the 4th and 5th pentads of December, the first three pentads of January and the 3rd pentad of February to the 1st pentad of March. Then the 200 hPa and 850 hPa geopotential height fields are selected to represent high and low atmospheric layers. Synthetic analysis shows that: during the processes of index anomalies, characteristics of strong EU pattern exists in both of the high and low atmospheric layers; and temperature in most parts of China is influenced by EU index anomalies, showing significant difference. Precipitation presents significant difference in the middle and lower reaches of the Yellow River and Yangtze River, and parts of southeastern China. During positive abnormal processes, influenced by the strengthened Siberian high, northerly winds prevail in the lower troposphere over China with lower temperature and less rainfalls. The opposite situation tends to occur in negative processes.
2013, 39(9):1103-1110.
DOI: 10.7519/j.issn.1000-0526.2013.09.003
Abstract:
In this paper, the possible predictors of the summer climate in 2012 in China are reviewed based on both the dynamic forecasts and the statistical predictions. In the winter of 2011/2012, the La Nina event reaches its peak, the Arctic sea ice area is much less than its climatology, the intensity of the Antarctic oscillation is the second higher since 1979, and the snow cover over the Tibetan Plateau is more but warmer than normal. Under the influence of these abnormal features, the East Asian monsoon becomes stronger in the following summer and the main rainfall belt locates in northern China. These basic characteristics have been captured successfully in the prediction issued by the National Climate Centre of CMA in early April. Besides, the air temperatures in most regions in the country are warmer, the tropical cyclones are more active in June-August, the onset date of the South China Sea summer monsoon is earlier, the Chinese Meiyu along the middle low reaches of Yangtze River Valley is less, and the rainfall in North China is earlier and more. In the last part of this paper, the predictability and the difficulty of the seasonal rainfall forecast are discussed, and the scientific questions together with the operational problems are also listed.
In this paper, the possible predictors of the summer climate in 2012 in China are reviewed based on both the dynamic forecasts and the statistical predictions. In the winter of 2011/2012, the La Nina event reaches its peak, the Arctic sea ice area is much less than its climatology, the intensity of the Antarctic oscillation is the second higher since 1979, and the snow cover over the Tibetan Plateau is more but warmer than normal. Under the influence of these abnormal features, the East Asian monsoon becomes stronger in the following summer and the main rainfall belt locates in northern China. These basic characteristics have been captured successfully in the prediction issued by the National Climate Centre of CMA in early April. Besides, the air temperatures in most regions in the country are warmer, the tropical cyclones are more active in June-August, the onset date of the South China Sea summer monsoon is earlier, the Chinese Meiyu along the middle low reaches of Yangtze River Valley is less, and the rainfall in North China is earlier and more. In the last part of this paper, the predictability and the difficulty of the seasonal rainfall forecast are discussed, and the scientific questions together with the operational problems are also listed.
2013, 39(9):1111-1118.
DOI: 10.7519/j.issn.1000-0526.2013.09.004
Abstract:
The East Asain summer monsoon was stronger in 2012, though the Tibetan Plateau (TP) snow cover extent was anomalously larger than the climate mean in the preceding spring and winter, which is inconsistent with the results of previous studies. This paper made an effort to investigate the possible relationship between the TP snow cover from winter 2011 to spring 2012 and the following Asian summer monsoon, using the monthly mean snow cover extent data from Rutgers University Global Snow Lab, NCEP/NCAR reanalysis monthly average data, and the monthly data set of NOAA’s Precipitation Reconstruction over Land (PREC/L). The findings suggest that the TP was covered mainly by an anomalous cyclone with lower temperature in the mid troposphere in spring 2012 and the previous winter, which agreed with the features of larger snow cover years. Particularly to the west of 90°E, the mid tropospheric temperature anomalies from the TP to the tropical Indian Ocean were negative in the north and positive in the south from winter to spring, conducive to the weaker meridional temperature gradient there in summer and thus to the weaker South Aisan summer monsoon. However, to the east of 90°E, the mid tropospheric temperature anomalies from East Asia to the tropics were positive in the north and negative in the south in winter and spring, favorable for the earlier seasonal transition from winter to summer in the southeastern Asia, the earlier onset of the South China Sea summer monsoon, and also the stronger East Asian summer monsoon. They were more influenced by other forcings than the TP. Therefore, the fact of more TP snow cover from winter 2011 to spring 2012 probably made a significant contribution to the following weaker South Asian summer monsoon, and had less impact on the East Asian summer monsoon in 2012.
The East Asain summer monsoon was stronger in 2012, though the Tibetan Plateau (TP) snow cover extent was anomalously larger than the climate mean in the preceding spring and winter, which is inconsistent with the results of previous studies. This paper made an effort to investigate the possible relationship between the TP snow cover from winter 2011 to spring 2012 and the following Asian summer monsoon, using the monthly mean snow cover extent data from Rutgers University Global Snow Lab, NCEP/NCAR reanalysis monthly average data, and the monthly data set of NOAA’s Precipitation Reconstruction over Land (PREC/L). The findings suggest that the TP was covered mainly by an anomalous cyclone with lower temperature in the mid troposphere in spring 2012 and the previous winter, which agreed with the features of larger snow cover years. Particularly to the west of 90°E, the mid tropospheric temperature anomalies from the TP to the tropical Indian Ocean were negative in the north and positive in the south from winter to spring, conducive to the weaker meridional temperature gradient there in summer and thus to the weaker South Aisan summer monsoon. However, to the east of 90°E, the mid tropospheric temperature anomalies from East Asia to the tropics were positive in the north and negative in the south in winter and spring, favorable for the earlier seasonal transition from winter to summer in the southeastern Asia, the earlier onset of the South China Sea summer monsoon, and also the stronger East Asian summer monsoon. They were more influenced by other forcings than the TP. Therefore, the fact of more TP snow cover from winter 2011 to spring 2012 probably made a significant contribution to the following weaker South Asian summer monsoon, and had less impact on the East Asian summer monsoon in 2012.
2013, 39(9):1119-1124.
DOI: 10.7519/j.issn.1000-0526.2013.09.005
Abstract:
Decadal variations of the East Asian summer monsoon and the summer precipitation are investigated by using the NCAR/NCEP and ERA 40 reanalysis dataset and the monthly rainfall data at 160 Chinese stations during 1951-2010. For better illustration, an East Asian summer meridional circulation index (EASMCI) is defined in this paper and its relationship with the summer precipitation over the Haihe River Basin is analyzed as well. Results indicate that the westerly winds at both the lower and the higher troposphere in East Asia show anti phase variations since the 1980s. Results also indicate the meridional wind speed at lower troposphere and the EASMCI have decreased in recent 30 years, weakening the summer monsoon and blocking the northward movement of the summer rain belt. Statistical analysis shows a significant positive correlation between the summer precipitation over the Haihe River Basin and the EASMCI. Under the positive phase of the index, the East Asian summer meridional circulation is strengthened and accelerates the south wind to blow more northward, favoring the summer precipitation over the basin. However, under the negative phase of the index, the precipitation is less. In a word, the results in this paper demonstrate that the decadal weakening of the EASMCI is possibly a direct reason for the decrease of the precipitation over the Haihe River Basin in recent 30 years.
Decadal variations of the East Asian summer monsoon and the summer precipitation are investigated by using the NCAR/NCEP and ERA 40 reanalysis dataset and the monthly rainfall data at 160 Chinese stations during 1951-2010. For better illustration, an East Asian summer meridional circulation index (EASMCI) is defined in this paper and its relationship with the summer precipitation over the Haihe River Basin is analyzed as well. Results indicate that the westerly winds at both the lower and the higher troposphere in East Asia show anti phase variations since the 1980s. Results also indicate the meridional wind speed at lower troposphere and the EASMCI have decreased in recent 30 years, weakening the summer monsoon and blocking the northward movement of the summer rain belt. Statistical analysis shows a significant positive correlation between the summer precipitation over the Haihe River Basin and the EASMCI. Under the positive phase of the index, the East Asian summer meridional circulation is strengthened and accelerates the south wind to blow more northward, favoring the summer precipitation over the basin. However, under the negative phase of the index, the precipitation is less. In a word, the results in this paper demonstrate that the decadal weakening of the EASMCI is possibly a direct reason for the decrease of the precipitation over the Haihe River Basin in recent 30 years.
2013, 39(9):1125-1132.
DOI: 10.7519/j.issn.1000-0526.2013.09.006
Abstract:
The relationship between Kuroshio sea surface temperature index (KuSSTI) and the first frost dates (FFDs) in northern China are analyzed on the basis of observation data and reanalysis data. The results show that the monthly KuSSTIs of respective months of summer and early autumn have significant impacts on FFDs in northern China. The warmer (cooler) the Kuroshio SSTs are, the later (earlier) FFDs in North China, Huang Huai Region, northern Hetao Region, middle and northeastern Inner Mongolia and the region around the Bohai Sea are. Further analysis indicates that the warm (cold) Kuroshio SST anomalies significantly influence the general circulation from northern China, Japan Sea to north Pacific, increasing (decreasing) the 500 hPa geopotential height and weakening (strengthening) the East Asia trough. The lower level wind anomaly shows southeast (northwest) direction over North China and Huang Huai Region, weakening (strengthening) the cold wave from the north, so that the FFDs in North China and Huang Huai Region come later (earlier) than normal.
The relationship between Kuroshio sea surface temperature index (KuSSTI) and the first frost dates (FFDs) in northern China are analyzed on the basis of observation data and reanalysis data. The results show that the monthly KuSSTIs of respective months of summer and early autumn have significant impacts on FFDs in northern China. The warmer (cooler) the Kuroshio SSTs are, the later (earlier) FFDs in North China, Huang Huai Region, northern Hetao Region, middle and northeastern Inner Mongolia and the region around the Bohai Sea are. Further analysis indicates that the warm (cold) Kuroshio SST anomalies significantly influence the general circulation from northern China, Japan Sea to north Pacific, increasing (decreasing) the 500 hPa geopotential height and weakening (strengthening) the East Asia trough. The lower level wind anomaly shows southeast (northwest) direction over North China and Huang Huai Region, weakening (strengthening) the cold wave from the north, so that the FFDs in North China and Huang Huai Region come later (earlier) than normal.
2013, 39(9):1133-1138.
DOI: 10.7519/j.issn.1000-0526.2013.09.007
Abstract:
With the NCEP/NCAR reanalysis data during 1961-2011 and the precipitation data from 45 stations in the Yellow River Basin, Nino3 SST difference index (ΔI SST3) from the previous October to current April is defined and the relationship between ΔI SST3 and summer sea surface temperature, and the correlations of atmospheric circulation and summer precipitation in Yellow River Basin with the Δ I SST3 index are analyzed. The results show that: (1) When ΔI SST3 increases (decreases), the following summer’s sea surface temperature of the central and eastern equatorial Pacific tends to be warm (cool) while that of the area from South China Sea to Philippines Peninsula sea region tends to be cool (warm). (2) The Δ I SST3 also shows a significant negative correlation with the subtropical area within 100°E-80°W at the 500 hPa height field. The positive and negative abnormal difference field of Δ I SST3 shows that when the Δ I SST3 increases (decreases), the height at 500 hPa over the tropical and subtropical Pacific regions in summer is lower (higher); the 850 hPa westerly (easterly) to the north of the equator appears to be abnormal; the Western Pacific subtropical high is significantly weak (strong); northerly (southerly) airflow prevails in coastal areas of eastern China; warm and humid airflow is inactive (active); the monsoon is weaker (stronger). However, the Mongolia cyclone (anticyclone) in the middle and high latitudes is further developing. As a result, the anticyclonic (cyclonic) circulation covers the Hetao Region.(3) The ΔI SST3 and the summer precipitation over the Yellow River Basin share a significant negative correlation with a coefficient of -0.51. When the Δ I SST3 is positively abnormal,the summer precipitation in the Yellow River Basin is likely to decline; When the Δ I SST3 presents negative anomaly,precipitation of the Yellow River basin in summer tends to exceed the normal, and the negative anomaly has more significant influence on the summer precipitation of the Yellow River Basin.
With the NCEP/NCAR reanalysis data during 1961-2011 and the precipitation data from 45 stations in the Yellow River Basin, Nino3 SST difference index (ΔI SST3) from the previous October to current April is defined and the relationship between ΔI SST3 and summer sea surface temperature, and the correlations of atmospheric circulation and summer precipitation in Yellow River Basin with the Δ I SST3 index are analyzed. The results show that: (1) When ΔI SST3 increases (decreases), the following summer’s sea surface temperature of the central and eastern equatorial Pacific tends to be warm (cool) while that of the area from South China Sea to Philippines Peninsula sea region tends to be cool (warm). (2) The Δ I SST3 also shows a significant negative correlation with the subtropical area within 100°E-80°W at the 500 hPa height field. The positive and negative abnormal difference field of Δ I SST3 shows that when the Δ I SST3 increases (decreases), the height at 500 hPa over the tropical and subtropical Pacific regions in summer is lower (higher); the 850 hPa westerly (easterly) to the north of the equator appears to be abnormal; the Western Pacific subtropical high is significantly weak (strong); northerly (southerly) airflow prevails in coastal areas of eastern China; warm and humid airflow is inactive (active); the monsoon is weaker (stronger). However, the Mongolia cyclone (anticyclone) in the middle and high latitudes is further developing. As a result, the anticyclonic (cyclonic) circulation covers the Hetao Region.(3) The ΔI SST3 and the summer precipitation over the Yellow River Basin share a significant negative correlation with a coefficient of -0.51. When the Δ I SST3 is positively abnormal,the summer precipitation in the Yellow River Basin is likely to decline; When the Δ I SST3 presents negative anomaly,precipitation of the Yellow River basin in summer tends to exceed the normal, and the negative anomaly has more significant influence on the summer precipitation of the Yellow River Basin.
2013, 39(9):1139-1144.
DOI: 10.7519/j.issn.1000-0526.2013.09.008
Abstract:
Basic characteristics of the Meiyu over the middle lower reaches of Yangtze River in 1961-2011 are investigated by using the updated precipitation data, especially for the new features in the 21st century. The results indicate both the length of Meiyu period and rainy days reduce in recent decade, and the Meiyu amount also decreases. This change could be attributed to the negative Pacific Decadal Oscillation (PDO) and the increased frequency of the La Nina events in the 21st century. Under the negative PDO phase, rainfall above normal always occurs in northern China, especially in the regions north of the Huaihe River Valley. As a result of the more frequent La Nina events, the SSTs over the western Pacific warmer pool increase in recent decade and force the western Pacific subtropical high to be stronger and more westward and northward. Thus the warmer and wetter southwesterly moisture over the Bay of Bengal and the tropical Indian Ocean has been transported to the regions north of the Huahe River Valley instead of the Meiyu areas. This is a possible cause of the decrease of the Meiyu in the 21st century.
Basic characteristics of the Meiyu over the middle lower reaches of Yangtze River in 1961-2011 are investigated by using the updated precipitation data, especially for the new features in the 21st century. The results indicate both the length of Meiyu period and rainy days reduce in recent decade, and the Meiyu amount also decreases. This change could be attributed to the negative Pacific Decadal Oscillation (PDO) and the increased frequency of the La Nina events in the 21st century. Under the negative PDO phase, rainfall above normal always occurs in northern China, especially in the regions north of the Huaihe River Valley. As a result of the more frequent La Nina events, the SSTs over the western Pacific warmer pool increase in recent decade and force the western Pacific subtropical high to be stronger and more westward and northward. Thus the warmer and wetter southwesterly moisture over the Bay of Bengal and the tropical Indian Ocean has been transported to the regions north of the Huahe River Valley instead of the Meiyu areas. This is a possible cause of the decrease of the Meiyu in the 21st century.
2013, 39(9):1145-1153.
DOI: 10.7519/j.issn.1000-0526.2013.09.009
Abstract:
The research of MJO has showed that it is a new and workable method for studying the extended period weather forecast (10 to 30 days) to use the propagation process of MJO. However, how to predict the extended period rainfall process in winter Yunnan is an important problem to be solved in forecast operations. In this paper, rainfall circulation configurations under the influence of MJO are divided into three types, and the corresponding three weather processes are contrasted and analyzed in order to find the forecast predictors for the extended period weather forecast. The results showed that firstly, the tropical convection activities will be fully aroused when MJO activity center enters into the west Bengal and tropical regions of Pacific (called “wet window”). Otherwise, the tropical convection activity is not active in the upstream region of Yunnan (called “dry window”). Secondly, when MJO is in wet window, the occurrence of precipitation process is under the condition of cold air and suitable circulation. Southerly winds of Southern branch trough or the West Pacific subtropical high guides the water vapor into Yunnan. But, when MJO is in dry window, even though there is befitting condition of water vapor and circulation perturbation, the large scale rainfall process does not happen.
The research of MJO has showed that it is a new and workable method for studying the extended period weather forecast (10 to 30 days) to use the propagation process of MJO. However, how to predict the extended period rainfall process in winter Yunnan is an important problem to be solved in forecast operations. In this paper, rainfall circulation configurations under the influence of MJO are divided into three types, and the corresponding three weather processes are contrasted and analyzed in order to find the forecast predictors for the extended period weather forecast. The results showed that firstly, the tropical convection activities will be fully aroused when MJO activity center enters into the west Bengal and tropical regions of Pacific (called “wet window”). Otherwise, the tropical convection activity is not active in the upstream region of Yunnan (called “dry window”). Secondly, when MJO is in wet window, the occurrence of precipitation process is under the condition of cold air and suitable circulation. Southerly winds of Southern branch trough or the West Pacific subtropical high guides the water vapor into Yunnan. But, when MJO is in dry window, even though there is befitting condition of water vapor and circulation perturbation, the large scale rainfall process does not happen.
2013, 39(9):1154-1162.
DOI: 10.7519/j.issn.1000-0526.2013.09.010
Abstract:
Daily actual evapotranspiration is estimated based on surface net radiation, vegetation index, mean temperature and daily temperature difference by using satellite remote sensing data and routine meteorological data. Also, the estimated ET is compared with the measured ET using eddy covariance method at Luancheng Station. Besides, the temporal and spatial variation of actual evapotranspiration and its impact factors are analyzed qualitatively. According to the evapotranspiration drought index (EDI), the distribution characteristics of drought in North China is analyzed and compared to Palmer index and precipitation anomaly percentage respectively. The results show that the estimated evapotranspiration through the ET model correlates well with the measured ET and the estimation is acceptable for assessing the drought conditions in large areas. In addition, the EDI anomaly can reflect a higher spatial resolution of drought pattern and is reliable in the indication and judgment of drought.
Daily actual evapotranspiration is estimated based on surface net radiation, vegetation index, mean temperature and daily temperature difference by using satellite remote sensing data and routine meteorological data. Also, the estimated ET is compared with the measured ET using eddy covariance method at Luancheng Station. Besides, the temporal and spatial variation of actual evapotranspiration and its impact factors are analyzed qualitatively. According to the evapotranspiration drought index (EDI), the distribution characteristics of drought in North China is analyzed and compared to Palmer index and precipitation anomaly percentage respectively. The results show that the estimated evapotranspiration through the ET model correlates well with the measured ET and the estimation is acceptable for assessing the drought conditions in large areas. In addition, the EDI anomaly can reflect a higher spatial resolution of drought pattern and is reliable in the indication and judgment of drought.
2013, 39(9):1163-1170.
DOI: 10.7519/j.issn.1000-0526.2013.09.011
Abstract:
Drought and flood have significant impacts on catchment water use and ecological balance. To develop practical drought/flood monitoring indicators that only need a few climate variables, it is fundamentally necessary to explore the relationship between hydrology variables and climate variables for the specific catchment. This study investigates the correlations between lake water level and various time scale climatological indices according to the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), based on the monthly water level records from Honghu Lake representative gauging stations and the monthly observations of 8 meteorological stations in the Four Lake Basin. The results showed that extreme droughts and floods are primarily controlled by precipitation variability over the Four Lake Basin, and both SPEI and SPI are well related with lake water level of Honghu Lake while the degree of the correlation varies between different seasons and SPEI/SPI time scales, with the highest correlations for rainy summer and autumn months. Generally, the 4-6 month scale SPEI/SPI drought index is most closely correlated with lake water level of Honghu Lake, showing an apparent response of lake water level to the current and former months’ water surplus and deficiency. When compared with the historical time series of monthly average lake water level of Honghu Lake, the 5 month scale SPEI/SPI agrees well with the variability of the lake water level. The response relationship found during the study can not only aid the monitoring and forecasting of flood and drought conditions in the Four Lake Basin based on conventional weather data, but also provides some references for other places of China.
Drought and flood have significant impacts on catchment water use and ecological balance. To develop practical drought/flood monitoring indicators that only need a few climate variables, it is fundamentally necessary to explore the relationship between hydrology variables and climate variables for the specific catchment. This study investigates the correlations between lake water level and various time scale climatological indices according to the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI), based on the monthly water level records from Honghu Lake representative gauging stations and the monthly observations of 8 meteorological stations in the Four Lake Basin. The results showed that extreme droughts and floods are primarily controlled by precipitation variability over the Four Lake Basin, and both SPEI and SPI are well related with lake water level of Honghu Lake while the degree of the correlation varies between different seasons and SPEI/SPI time scales, with the highest correlations for rainy summer and autumn months. Generally, the 4-6 month scale SPEI/SPI drought index is most closely correlated with lake water level of Honghu Lake, showing an apparent response of lake water level to the current and former months’ water surplus and deficiency. When compared with the historical time series of monthly average lake water level of Honghu Lake, the 5 month scale SPEI/SPI agrees well with the variability of the lake water level. The response relationship found during the study can not only aid the monitoring and forecasting of flood and drought conditions in the Four Lake Basin based on conventional weather data, but also provides some references for other places of China.
2013, 39(9):1171-1175.
DOI: 10.7519/j.issn.1000-0526.2013.09.012
Abstract:
By using daily precipitation and temperature data in 170 meteorological stations and historical drought disaster information in the Huaihe River Basin from 1961 to 2010, this paper studies the adaptability of the CI index, and then analyzes the spatial temporal characteristics of drought in the recent 50 years with a variety of statistical methods. The results show that the correlation coefficient between drought days calculated by CI index and drought disasters has past the 0.01 significance level test, indicating that the CI index has good regional adaptability in the Huaihe River Basin. The spatial distribution of the average drought days which descends from north to south is latitudinal. The trend of drought days ascends in the east and west, and descends in the central and north of the basin, but they all have not passed the 0.05 significance level test. The cumulative percent variance of the EOF first three modes reaches 94.4%, the first distribution pattern is consistent within the whole basin, the second is contrary between south and north, and the third is contrary between east and west. The drought days have experienced four circulations since 1961, and now are in the period less than normal. The Mann Kendall mutation test shows that there is no obvious mutation point of drought days in the Huaihe River Basin in the recent 50 years.
By using daily precipitation and temperature data in 170 meteorological stations and historical drought disaster information in the Huaihe River Basin from 1961 to 2010, this paper studies the adaptability of the CI index, and then analyzes the spatial temporal characteristics of drought in the recent 50 years with a variety of statistical methods. The results show that the correlation coefficient between drought days calculated by CI index and drought disasters has past the 0.01 significance level test, indicating that the CI index has good regional adaptability in the Huaihe River Basin. The spatial distribution of the average drought days which descends from north to south is latitudinal. The trend of drought days ascends in the east and west, and descends in the central and north of the basin, but they all have not passed the 0.05 significance level test. The cumulative percent variance of the EOF first three modes reaches 94.4%, the first distribution pattern is consistent within the whole basin, the second is contrary between south and north, and the third is contrary between east and west. The drought days have experienced four circulations since 1961, and now are in the period less than normal. The Mann Kendall mutation test shows that there is no obvious mutation point of drought days in the Huaihe River Basin in the recent 50 years.
2013, 39(9):1176-1181.
DOI: 10.7519/j.issn.1000-0526.2013.09.013
Abstract:
Because the main earlier circulation indices with different monthly variation features have different influences on midsummer (July-August) precipitation in China, different methods should be used to predict the midsummer prediction anomalies with respect to the monthly continuity and transition features of the impact factors. The 78 monthly circulation indices from National Climate Centre and the 30 indices from CPC/NOAA are employed to construct two factor schemes to describe the continuity and transition of circulation anomaly characteristics respectively. With the above different schemes, the “Running Correlation， Stepwise Regression， Ensemble Analysis” method is used to set up two models to predict the midsummer precipitation of 160 stations over China. Therefore, different variation features of earlier circulation indices are used in our statistic prediction models and different effects of the above two schemes are well shown. The result indicates that both of the factor treating schemes have certain predictive abilities but the transition one shows better effect. Meanwhile, for single station, the ensemble of the indices with its cross modeling series closely correlated to the observation time series holds more potential prediction ability.
Because the main earlier circulation indices with different monthly variation features have different influences on midsummer (July-August) precipitation in China, different methods should be used to predict the midsummer prediction anomalies with respect to the monthly continuity and transition features of the impact factors. The 78 monthly circulation indices from National Climate Centre and the 30 indices from CPC/NOAA are employed to construct two factor schemes to describe the continuity and transition of circulation anomaly characteristics respectively. With the above different schemes, the “Running Correlation， Stepwise Regression， Ensemble Analysis” method is used to set up two models to predict the midsummer precipitation of 160 stations over China. Therefore, different variation features of earlier circulation indices are used in our statistic prediction models and different effects of the above two schemes are well shown. The result indicates that both of the factor treating schemes have certain predictive abilities but the transition one shows better effect. Meanwhile, for single station, the ensemble of the indices with its cross modeling series closely correlated to the observation time series holds more potential prediction ability.
2013, 39(9):1182-1189.
DOI: 10.7519/j.issn.1000-0526.2013.09.014
Abstract:
The empirical mode decomposition (EMD) method has the advantage of dealing with the nonlinear and nonstationary data, making them linearized and stationary. So EMD is adopted to analyze the precipitation data based on the multi time scale viewpoint, and the relatively simple semi period signal with different oscillations are decomposed from the complex nonstationary and nonlinear signal. Then the characteristic intrinsic mode functions (IMFs) are chosen to construct the regression ensemble prediction model (REPM), which is based on the mean generation regression (MGR) method, the mean generation correlation (MGC) method, the rhythm fitting error (RFE) method and the fitting error (FE) method. The results show that the average score of the Ps and the same symbol ratio (SSR) are 68-73 and 50%-58%, respectively, among the four kinds of single models during rainy period in Guangdong for the recent 10 years. However, in the REPM, the average Ps and SSR scores have reached 79.8 and 68.8%, respectively, increasing 10 scores and 10% or so compared with one of the four kinds of single models. Meanwhile, if the SST signals in tropical East Pacific in the previous winter are coupled into the REPM, the Ps and SSR scores have improved, but the SSR scores, 3.1% higher than the former. Therefore, both the multi time scale information extracting from the meteorological elements and the ensemble model construction can improve the accuracy of short term climate prediction.
The empirical mode decomposition (EMD) method has the advantage of dealing with the nonlinear and nonstationary data, making them linearized and stationary. So EMD is adopted to analyze the precipitation data based on the multi time scale viewpoint, and the relatively simple semi period signal with different oscillations are decomposed from the complex nonstationary and nonlinear signal. Then the characteristic intrinsic mode functions (IMFs) are chosen to construct the regression ensemble prediction model (REPM), which is based on the mean generation regression (MGR) method, the mean generation correlation (MGC) method, the rhythm fitting error (RFE) method and the fitting error (FE) method. The results show that the average score of the Ps and the same symbol ratio (SSR) are 68-73 and 50%-58%, respectively, among the four kinds of single models during rainy period in Guangdong for the recent 10 years. However, in the REPM, the average Ps and SSR scores have reached 79.8 and 68.8%, respectively, increasing 10 scores and 10% or so compared with one of the four kinds of single models. Meanwhile, if the SST signals in tropical East Pacific in the previous winter are coupled into the REPM, the Ps and SSR scores have improved, but the SSR scores, 3.1% higher than the former. Therefore, both the multi time scale information extracting from the meteorological elements and the ensemble model construction can improve the accuracy of short term climate prediction.
2013, 39(9):1190-1196.
DOI: 10.7519/j.issn.1000-0526.2013.09.015
Abstract:
A principal component stepwise regression prediction model of climatic field for the flood period rainfall in Fujian Province is established. The model predicts the precipitation of flood period in Fujian through predicting the principal component of the climatic field of that period. This study takes the 500 hPa height and the sea surface temperature of Pacific Ocean and the sea level pressure in the Northern Hemisphere and many principal component factors in various seasons and regions as predictors, calculating and analyzing the distribution and types of the principal components of the flood period rainfall in Fujian. Through correlation screening and double test stepwise regression, a prediction equation is developed for the principal component of the Fujian flood period rainfall. By applying this model to predicting the flood period precipitation in Fujian in 2012, it is found that the model is capable to predict the precipitation and its distribution in the flood period in Fujian.
A principal component stepwise regression prediction model of climatic field for the flood period rainfall in Fujian Province is established. The model predicts the precipitation of flood period in Fujian through predicting the principal component of the climatic field of that period. This study takes the 500 hPa height and the sea surface temperature of Pacific Ocean and the sea level pressure in the Northern Hemisphere and many principal component factors in various seasons and regions as predictors, calculating and analyzing the distribution and types of the principal components of the flood period rainfall in Fujian. Through correlation screening and double test stepwise regression, a prediction equation is developed for the principal component of the Fujian flood period rainfall. By applying this model to predicting the flood period precipitation in Fujian in 2012, it is found that the model is capable to predict the precipitation and its distribution in the flood period in Fujian.
2013, 39(9):1197-1203.
DOI: 10.7519/j.issn.1000-0526.2013.09.016
Abstract:
Using winter precipitation data from 73 meteorological stations in Hebei Province during 1961-2009, NCEP/NCAR reanalysis data and NOAA SST data of the Pacific Ocean during the same period, features of precipitation anomalies in Hebei Province in winter and their relations with the atmospheric circulation and SSTA of the Pacific Ocean are analyzed with the Singular Value Decomposition (SVD) analysis method, and other statistical methods. The results indicate that winter precipitation in Hebei has the characteristics of interdecadal and periodic variations. In the scale within a decade, 8 to 10 year or 2 to 3 year periodic changes in winter have been found in the recent 49 years. When the 500 hPa height field over East Asia in winter shows the positive, negative and positive East Asia-Pacific (EAP) teleconnection pattern from low to high latitudes, Hebei receives more precipitation than normal and the most remarkable areas are in Cangzhou and the eastern part of Chengde. When the distribution pattern of SST of the North Pacific shows PDO positive phase and the central equatorial Pacific distribution of SSTA appears to be the pattern of El Ni〖AKn~D〗o, the winter precipitation in Hebei becomes even more especially in Xingtai, Handan and Cangzhou.
Using winter precipitation data from 73 meteorological stations in Hebei Province during 1961-2009, NCEP/NCAR reanalysis data and NOAA SST data of the Pacific Ocean during the same period, features of precipitation anomalies in Hebei Province in winter and their relations with the atmospheric circulation and SSTA of the Pacific Ocean are analyzed with the Singular Value Decomposition (SVD) analysis method, and other statistical methods. The results indicate that winter precipitation in Hebei has the characteristics of interdecadal and periodic variations. In the scale within a decade, 8 to 10 year or 2 to 3 year periodic changes in winter have been found in the recent 49 years. When the 500 hPa height field over East Asia in winter shows the positive, negative and positive East Asia-Pacific (EAP) teleconnection pattern from low to high latitudes, Hebei receives more precipitation than normal and the most remarkable areas are in Cangzhou and the eastern part of Chengde. When the distribution pattern of SST of the North Pacific shows PDO positive phase and the central equatorial Pacific distribution of SSTA appears to be the pattern of El Ni〖AKn~D〗o, the winter precipitation in Hebei becomes even more especially in Xingtai, Handan and Cangzhou.
2013, 39(9):1204-1209.
DOI: 10.7519/j.issn.1000-0526.2013.09.017
Abstract:
Using 61 station precipitation data in the middle reaches of Yellow River, characteristics and ambient field of summer precipitation in the middle reaches of the Yellow River are analyzed and one prediction model is established in this paper. The research result reveales that summer precipitation in the middle reaches of Yellow River is mainly affected by the East Asian jet stream, the West Pacific subtropical high and the low trough in the vicinity of Lake Baikal. That is， when the East Asian jet stream and the West Pacific subtropical high are stronger, lying more northward, and the Baikal trough is deeper, more rains fall in this region, and vice versa. Besides, the autumn Southern Oscillation, the North African subtropical high, the South China Sea subtropical high, the Northern Hemisphere subtropical high and the Northern Hemisphere polar vortex can all exert an impact on the summer circulation and precipitation in the middle reaches of Yellow River. Therefore, a forecast model for summer precipitation in the middle reaches of the Yellow River is established by using the above factors. Assessment shows that this model has good prediction ability and can be used for quantitative prediction of summer precipitation in the middle reaches of Yellow River.
Using 61 station precipitation data in the middle reaches of Yellow River, characteristics and ambient field of summer precipitation in the middle reaches of the Yellow River are analyzed and one prediction model is established in this paper. The research result reveales that summer precipitation in the middle reaches of Yellow River is mainly affected by the East Asian jet stream, the West Pacific subtropical high and the low trough in the vicinity of Lake Baikal. That is， when the East Asian jet stream and the West Pacific subtropical high are stronger, lying more northward, and the Baikal trough is deeper, more rains fall in this region, and vice versa. Besides, the autumn Southern Oscillation, the North African subtropical high, the South China Sea subtropical high, the Northern Hemisphere subtropical high and the Northern Hemisphere polar vortex can all exert an impact on the summer circulation and precipitation in the middle reaches of Yellow River. Therefore, a forecast model for summer precipitation in the middle reaches of the Yellow River is established by using the above factors. Assessment shows that this model has good prediction ability and can be used for quantitative prediction of summer precipitation in the middle reaches of Yellow River.
2013, 39(9):1210-1216.
DOI: 10.7519/j.issn.1000-0526.2013.09.018
Abstract:
In this paper, a predictive model constructed in 2002 to forecast summer rain field in Shandong Province is significantly improved. On the basis of the original prediction factors of 100 hPa and 500 hPa geopotential heights and sea surface temperature of the key zone, teleconnection circulation indices characterizing monthly development and regional circulation of weather system are taken into account. Climate background of the atmospheric circulation abrupt change is considered when selecting data of 1977-2008 period to construct the model. And besides of mathematical analysis, schemes considering physical implications of the predictors are included in the new model. The new model, the original model and the 2002 predictive model are comparatively evaluated by using the 2009-2011 observation data. Results show that performance of the improved model is much better than the original one. The new model has also good performance of predictions in forecasting spatial distributions of precipitation.
In this paper, a predictive model constructed in 2002 to forecast summer rain field in Shandong Province is significantly improved. On the basis of the original prediction factors of 100 hPa and 500 hPa geopotential heights and sea surface temperature of the key zone, teleconnection circulation indices characterizing monthly development and regional circulation of weather system are taken into account. Climate background of the atmospheric circulation abrupt change is considered when selecting data of 1977-2008 period to construct the model. And besides of mathematical analysis, schemes considering physical implications of the predictors are included in the new model. The new model, the original model and the 2002 predictive model are comparatively evaluated by using the 2009-2011 observation data. Results show that performance of the improved model is much better than the original one. The new model has also good performance of predictions in forecasting spatial distributions of precipitation.
2013, 39(9):1217-1220.
DOI: 10.7519/j.issn.1000-0526.2013.09.019
Abstract:
RMM1, RMM2 and amplitude averaged from 1 to 25th are used to take the place of the average monthly. Right field consists of RMM1, RMM2 and amplitude of the preceding month, and left field consists of monthly rainfall over the Yangtze River Valley. The relationships between the two fields are studied by SVD. With optimization technique the time coefficients of the left field are estimated on the basis of the time coefficient of the right field according to the total number of stations which have the same sign between estimated anomaly and observed anomaly. Rainfall fields are retrieved by linear combination of the time coefficients and the vectors. Even though few of first models of SVD are above the significant level, the actual predictions achieve good results.
RMM1, RMM2 and amplitude averaged from 1 to 25th are used to take the place of the average monthly. Right field consists of RMM1, RMM2 and amplitude of the preceding month, and left field consists of monthly rainfall over the Yangtze River Valley. The relationships between the two fields are studied by SVD. With optimization technique the time coefficients of the left field are estimated on the basis of the time coefficient of the right field according to the total number of stations which have the same sign between estimated anomaly and observed anomaly. Rainfall fields are retrieved by linear combination of the time coefficients and the vectors. Even though few of first models of SVD are above the significant level, the actual predictions achieve good results.
2013, 39(9):1221-1226.
DOI: 10.7519/j.issn.1000-0526.2013.09.020
Abstract:
Climate comfort degree is very important to the development of tourism and it is also a major factor affecting the duration of tourism season. This paper employs a comprehensive climate comfort evaluation model, which is based on temperature humidity index (THI), wind chill index (WCI) and index of clothing (ICL). We select nine famous mountain scenic areas which are typical in China sceneries and analyze climate comfort degree according to the new model. Then the grades of fitness and its temporal distribution are classified. The climate comfort degree of each season and north south variation are analyzed, too. Nine famous mountains are divided into three types based on the distribution of comfort period in a year. The results indicate that: The variation of comprehensive comfort index of Changbai Mountain and Wutai Mountain, which are located in the northern part of China, is like an inverted “V” and the comfortable period is short. The most comfortable period of Changbai Mountain is from June to August and more comfortable tourism period of Wutai Mountain is from June to August. The variation of comprehensive comfort index of Emei Mountain, Huangshan Mountain, Taishan Mountain and Huashan Mountain, which are located in the central part of China, looks like an inverted “U”. And their comfortable tourism period is from June to September. The variation of comprehensive comfort index of Lushan Mountain, Wuyi Mountain and Guilin Landscape, which are located in the southern part of China, looks like an “M” and the comfortable period is the longest. Lushan Mountain’s tourism comfortable period is from May to October， Wuyi Mountain and Guilin Landscape’s tourism comfortable period is from March to April and from October to November.
Climate comfort degree is very important to the development of tourism and it is also a major factor affecting the duration of tourism season. This paper employs a comprehensive climate comfort evaluation model, which is based on temperature humidity index (THI), wind chill index (WCI) and index of clothing (ICL). We select nine famous mountain scenic areas which are typical in China sceneries and analyze climate comfort degree according to the new model. Then the grades of fitness and its temporal distribution are classified. The climate comfort degree of each season and north south variation are analyzed, too. Nine famous mountains are divided into three types based on the distribution of comfort period in a year. The results indicate that: The variation of comprehensive comfort index of Changbai Mountain and Wutai Mountain, which are located in the northern part of China, is like an inverted “V” and the comfortable period is short. The most comfortable period of Changbai Mountain is from June to August and more comfortable tourism period of Wutai Mountain is from June to August. The variation of comprehensive comfort index of Emei Mountain, Huangshan Mountain, Taishan Mountain and Huashan Mountain, which are located in the central part of China, looks like an inverted “U”. And their comfortable tourism period is from June to September. The variation of comprehensive comfort index of Lushan Mountain, Wuyi Mountain and Guilin Landscape, which are located in the southern part of China, looks like an “M” and the comfortable period is the longest. Lushan Mountain’s tourism comfortable period is from May to October， Wuyi Mountain and Guilin Landscape’s tourism comfortable period is from March to April and from October to November.
2013, 39(9):1227-1232.
DOI: 10.7519/j.issn.1000-0526.2013.09.021
Abstract:
The following are the main characteristics of the general circulation of atmosphere in June 2013. There was only one polar vortex center, whose center was near Greenland, in the Northern Hemisphere with weaker strength compared to normal years. More high level troughs were active in middle high latitudes. The northwestern Pacific subtropical high was weaker than normal. The monthly mean precipitation amount was 99.9 mm, near climatological normal (99.3 mm). The monthly mean temperature was 20.7℃, being 0.7℃ higher than normal (20.0℃). Seven heavy rainfall processes occurred in this month and extreme daily precipitation was recorded at many stations and some places suffered from severe floods. On June 23, the region of middle and lower reaches of Yangtze River stepped into Meiyu period, and out of it on the 29th. Besides, large scale hot weather hit the Southern China for the first time this year. The tropical storm “Bebinca” became the first tropical storm landing China this year, and the time of landing was earlier than normal.
The following are the main characteristics of the general circulation of atmosphere in June 2013. There was only one polar vortex center, whose center was near Greenland, in the Northern Hemisphere with weaker strength compared to normal years. More high level troughs were active in middle high latitudes. The northwestern Pacific subtropical high was weaker than normal. The monthly mean precipitation amount was 99.9 mm, near climatological normal (99.3 mm). The monthly mean temperature was 20.7℃, being 0.7℃ higher than normal (20.0℃). Seven heavy rainfall processes occurred in this month and extreme daily precipitation was recorded at many stations and some places suffered from severe floods. On June 23, the region of middle and lower reaches of Yangtze River stepped into Meiyu period, and out of it on the 29th. Besides, large scale hot weather hit the Southern China for the first time this year. The tropical storm “Bebinca” became the first tropical storm landing China this year, and the time of landing was earlier than normal.
Mobile website
® 2024 All Rights Reserved
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
ISSN:1000-0526 CN:11-2282/P