中国覆盖比较完整的台站观测始于1951年，1951年之前虽然有一些观测记录，但是残缺不全。所以要建立更长的气候序列就要吸收代用资料，但是代用资料可能与气候要素仅有一定程度的相关，不可能一一对应，因此应用代用资料重建的气候序列...中国覆盖比较完整的台站观测始于1951年，1951年之前虽然有一些观测记录，但是残缺不全。所以要建立更长的气候序列就要吸收代用资料，但是代用资料可能与气候要素仅有一定程度的相关，不可能一一对应，因此应用代用资料重建的气候序列有一定的不确定性。英国East Anglia大学的Climatic Research Unit（简称CRU）通过整合已有的若干个知名数据库，重建了一套覆盖完整、高分辨率、且无缺测的月平均地表气候要素数据集，时间范围覆盖1901-2003年，空间为0．5°×0．5°经纬网格覆盖所有陆地。这套资料和中国已有的气候数据相比具有如下优点：第一，中国西部20世纪前半期非常缺少观测，CRU资料尽管包含插值带来的误差，经比较仍可作为有一定信度的参考；第二，中国现有的百年温度序列只是年或季分辨率，而CRU资料达到月分辨率；第三，建立这个序列仅使用观测结果，做统计内插，不包括代用资料所带来的不确定性。因此，CRU的序列与用代用资料补充得到的序列在资料方面有较大不同，比较这两个序列，不仅可以进一步确认中国气候变化的特征，也可以彼此校正。结果表明：（1）CRU资料反映的全国年平均温度年际变化和考虑代用资料重建的序列吻合得很好，相关系数达到0．84；（2）区域尺度上，两者在10个典型分区的气温变率也相当一致，相关整体保持在0．8左右，仅新疆西南部和西藏西北部两者差异较大；（3）CRU资料揭示的中国年总降水量在1951～2000年的变化与160站观测吻合，相关系数达到0．93；（4）CRU资料的中国东部四季降水量和重建资料十分一致，秋季一致性最好，相关0．93；（5）CRU资料和重建的序列比较一致地表现出中国温度和降水年代际变化的主要特征，其给出的20世纪20年代中国大旱和20世纪40年代中国高温的空间�展开更多
Soil moisture plays an important role in land-atmosphere interactions. It is an important geophysical parameter in research on climate, hydrology, agriculture, and forestry. Soil moisture has important climatic effect...Soil moisture plays an important role in land-atmosphere interactions. It is an important geophysical parameter in research on climate, hydrology, agriculture, and forestry. Soil moisture has important climatic effects by influencing ground evapotranspi ration, runoff, surface reflectivity, surface emissivity, surface sensible heat and latent heat flux. At the global scale, the extent of its influence on the atmosphere is second only to that of sea surface temperature. At the terrestrial scale, its influence is even greater than that of sea surface temperatures. This paper presents a China Land Soil Moisture Data Assimilation System (CLSMDAS) based on EnKF and land process models, and results of the application of this system in the China Land Soil Moisture Data Assimilation tests. CLSMDAS is comprised of the following components: 1) A land process mo del—Community Land Model Version 3.0 (CLM3.0)—developed by the US National Center for Atmospheric Research (NCAR); 2) Precipitation of atmospheric forcing data and surface-incident solar radiation data come from hourly outputs of the FY2 geostationary meteorological satellite; 3) EnKF (Ensemble Kalman Filter) land data assimilation method; and 4) Observa tion data including satellite-inverted soil moisture outputs of the AMSR-E satellite and soil moisture observation data. Results of soil moisture assimilation tests from June to September 2006 were analyzed with CLSMDAS. Both simulation and assimila tion results of the land model reflected reasonably the temporal-spatial distribution of soil moisture. The assimilated soil mois ture distribution matches very well with severe summer droughts in Chongqing and Sichuan Province in August 2006, the worst since the foundation of the People’s Republic of China in 1949. It also matches drought regions that occurred in eastern Hubei and southern Guangxi in September.展开更多
利用国家气象信息中心研制的全国30000多个地面自动站降水与CMORPH(Climate Prediction Center Morphing technique)卫星反演降水融合而成的融合降水产品,分析了融合降水平均偏差和均方根误差的时空分布特征,探讨了不同降水量级以及站...利用国家气象信息中心研制的全国30000多个地面自动站降水与CMORPH(Climate Prediction Center Morphing technique)卫星反演降水融合而成的融合降水产品,分析了融合降水平均偏差和均方根误差的时空分布特征,探讨了不同降水量级以及站点稀疏区和密集区的融合效果,结果表明:融合降水的平均偏差和均方根误差量值均较卫星反演降水有显著减小,随时间的变化幅度不大且误差的区域性差异减弱;融合降水不同量级降水日数分布接近于地面观测降水,虽高估了雨强小于等于4mm/d的降水,低估了大于4mm/d高值降水,但同一量级下的误差比卫星反演降水大幅减小,且随着降水强度的增加改善效果明显;站点密集区的融合降水值主要是取决于地面观测降水;站点稀疏区在没有站点分布时,融合降水值主要取决于卫星反演降水,但随着站点个数增加,地面观测降水在融合降水中所占比重逐渐增大,且超过了卫星反演降水的作用。可见融合降水充分有效利用了地面观测降水和卫星反演降水各自的优势,融合效果明显。展开更多
Extending across three major plateaus,namely the Qinghai-Tibetan Plateau,the Inner Mongolia-Xinjiang Plateau and the Loess Plateau,Northwest China has the complex terrain and spatio-temporal climate variations,and is ...Extending across three major plateaus,namely the Qinghai-Tibetan Plateau,the Inner Mongolia-Xinjiang Plateau and the Loess Plateau,Northwest China has the complex terrain and spatio-temporal climate variations,and is affected by the interactions among different circulation systems,such as the summer monsoon,the westerlies and the plateau monsoon.The understanding of the climate variability,as well as its characteristics and evolution mechanisms in this area has been limited so far.In this paper,the precipitation characteristics and mechanisms in the eastern and western parts of Northwest China during the flood season are compared and analyzed based on the data from 192 national meteorological observational sites in Northwest China in 1961-2016.The results show that,divided by the northern boundary of the East Asian summer monsoon,there are huge differences in the precipitation variation characteristics between the eastern and western parts.The inter-annual variations,interdecadal variations and total trends in the two parts all show a significant seesaw phenomenon.Moreover,it is found that the seesaw phenomenon of precipitation variation is closely related to the opposite variation between the East Asian summer monsoon index(MI)and the westerly circulation index(WI).In addition,the inverse variations on different time scales are only related to the contributions of precipitation at specific grades.Besides,in the two matching patterns of precipitation in the seesaw phenomenon,the middle and high latitudes are occupied by the"high-low-high"wave trains in the precipitation increases in the east of Northwest China(ENWC)and decreases in the west of Northwest China(WNWC)pattern,meaning precipitation increases in ENWC and decreases in WNWC.Whereas the opposite"low-high-low"wave trains at 500 hPa height are observed in the middle and high latitudes in the WH-EA pattern at 500 hPa height,meaning precipitation increases in WNWC and decreases in ENWC.Thus,the atmosphere circulation situation with two wave train types can su展开更多
South China （SC） experienced persistent heavy rain in June 2010. The climatic anomalies and related mechanism are analyzed in this study. Results show that the large-scale circulation pattern favorable for precipita...South China （SC） experienced persistent heavy rain in June 2010. The climatic anomalies and related mechanism are analyzed in this study. Results show that the large-scale circulation pattern favorable for precipitation was maintained. In the upper level, the South Asian High and westerly jet stream provided a divergent circulation over SC. In the middle and low levels, an anomalous strong subtropical high （STH） extended to the South China Sea. The southwesterly monsoon flow along the northwest flank of the STH transported abundant water vapor from the western North Pacific, the Bay of Bengal, and the South China Sea to SC. The precipitation can be classified into two types： the West Siberia low （WSL）-induced low-level cyclone mode, and the STH-induced low-level jet mode. STH and WSL indices are defined to estimate the influence of these two systems, respectively. Analysis shows that both are critical for precipitation, but their respective contributions differ from year to year. In 2010, both were important factors for the heavy rainfall in June.展开更多
The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observati...The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observational analysis indicates that Vicente influenced distant heavy rainfall by transporting water vapor northward to the Beijing area. This moisture transport was mainly driven by the interaction between Vicente and the western Pacific subtropical high（WPSH） associated with the formation of a low-level southeasterly moisture channel. A set of numerical sensitivity experiments were performed with prescribed typhoons of different intensities to investigate the interaction between Vicente and the WPSH and its effects on this rainstorm process. The results indicate that the WPSH interacting with typhoons of different intensities may exert varying degrees of influence on the development of a southeasterly moisture channel, resulting in a change in rain rate and location over the Beijing area. Specifically, in the presence of an enhanced typhoon,the WPSH shows remarkable withdrawal to the east, which is favorable for a northward extension of the southeasterly moisture channel, thereby increasing moisture supply for the rainstorm. The WPSH tends to stretch westward in a zonal pattern if the typhoon is weakened or removed, hindering the northward extension of the moisture channel. Thus, the rainfall area may be expected to expand or contract, with corresponding increases or decreases in rain rate over the Beijing area with a strengthened or weakened typhoon, respectively.展开更多
The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15%Cr(mass fraction) in-situ composites were systematically studied and high strength and high electrical conducti...The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15%Cr(mass fraction) in-situ composites were systematically studied and high strength and high electrical conductive Cu base in-situ composites have been developed. The best combination is the addition of 0.1% to 0.2% Zr, Ti, or Sn in Cu-15%Cr in-situ composite, thermomechanical treatment to refine the microstructure and optimizing the precipitation of second phase. The strength is controlled by high density of dislocations in the Cu matrix, the lamellar spacing of the second phase, and the fine Cr precipitates. The aging treatment to reduce solute atoms has a beneficial effect on the increase of electrical conductivity. The addition of Zr, or Ti of about 0.15% to 0.2% promotes the precipitation of Cr particles.展开更多
文摘中国覆盖比较完整的台站观测始于1951年，1951年之前虽然有一些观测记录，但是残缺不全。所以要建立更长的气候序列就要吸收代用资料，但是代用资料可能与气候要素仅有一定程度的相关，不可能一一对应，因此应用代用资料重建的气候序列有一定的不确定性。英国East Anglia大学的Climatic Research Unit（简称CRU）通过整合已有的若干个知名数据库，重建了一套覆盖完整、高分辨率、且无缺测的月平均地表气候要素数据集，时间范围覆盖1901-2003年，空间为0．5°×0．5°经纬网格覆盖所有陆地。这套资料和中国已有的气候数据相比具有如下优点：第一，中国西部20世纪前半期非常缺少观测，CRU资料尽管包含插值带来的误差，经比较仍可作为有一定信度的参考；第二，中国现有的百年温度序列只是年或季分辨率，而CRU资料达到月分辨率；第三，建立这个序列仅使用观测结果，做统计内插，不包括代用资料所带来的不确定性。因此，CRU的序列与用代用资料补充得到的序列在资料方面有较大不同，比较这两个序列，不仅可以进一步确认中国气候变化的特征，也可以彼此校正。结果表明：（1）CRU资料反映的全国年平均温度年际变化和考虑代用资料重建的序列吻合得很好，相关系数达到0．84；（2）区域尺度上，两者在10个典型分区的气温变率也相当一致，相关整体保持在0．8左右，仅新疆西南部和西藏西北部两者差异较大；（3）CRU资料揭示的中国年总降水量在1951～2000年的变化与160站观测吻合，相关系数达到0．93；（4）CRU资料的中国东部四季降水量和重建资料十分一致，秋季一致性最好，相关0．93；（5）CRU资料和重建的序列比较一致地表现出中国温度和降水年代际变化的主要特征，其给出的20世纪20年代中国大旱和20世纪40年代中国高温的空间�
基金supported by National High Technology Research and Development Program of China (Grant Nos. 2007AA12Z144, 2009AA12Z129)Chinese COPES Project (Grant Nos. GYHY200706005, GYHY200806014)China Meteorological Administration New Technology Promotion Project (Grant No. CMATG2008Z04)
文摘Soil moisture plays an important role in land-atmosphere interactions. It is an important geophysical parameter in research on climate, hydrology, agriculture, and forestry. Soil moisture has important climatic effects by influencing ground evapotranspi ration, runoff, surface reflectivity, surface emissivity, surface sensible heat and latent heat flux. At the global scale, the extent of its influence on the atmosphere is second only to that of sea surface temperature. At the terrestrial scale, its influence is even greater than that of sea surface temperatures. This paper presents a China Land Soil Moisture Data Assimilation System (CLSMDAS) based on EnKF and land process models, and results of the application of this system in the China Land Soil Moisture Data Assimilation tests. CLSMDAS is comprised of the following components: 1) A land process mo del—Community Land Model Version 3.0 (CLM3.0)—developed by the US National Center for Atmospheric Research (NCAR); 2) Precipitation of atmospheric forcing data and surface-incident solar radiation data come from hourly outputs of the FY2 geostationary meteorological satellite; 3) EnKF (Ensemble Kalman Filter) land data assimilation method; and 4) Observa tion data including satellite-inverted soil moisture outputs of the AMSR-E satellite and soil moisture observation data. Results of soil moisture assimilation tests from June to September 2006 were analyzed with CLSMDAS. Both simulation and assimila tion results of the land model reflected reasonably the temporal-spatial distribution of soil moisture. The assimilated soil mois ture distribution matches very well with severe summer droughts in Chongqing and Sichuan Province in August 2006, the worst since the foundation of the People’s Republic of China in 1949. It also matches drought regions that occurred in eastern Hubei and southern Guangxi in September.
文摘利用国家气象信息中心研制的全国30000多个地面自动站降水与CMORPH(Climate Prediction Center Morphing technique)卫星反演降水融合而成的融合降水产品,分析了融合降水平均偏差和均方根误差的时空分布特征,探讨了不同降水量级以及站点稀疏区和密集区的融合效果,结果表明:融合降水的平均偏差和均方根误差量值均较卫星反演降水有显著减小,随时间的变化幅度不大且误差的区域性差异减弱;融合降水不同量级降水日数分布接近于地面观测降水,虽高估了雨强小于等于4mm/d的降水,低估了大于4mm/d高值降水,但同一量级下的误差比卫星反演降水大幅减小,且随着降水强度的增加改善效果明显;站点密集区的融合降水值主要是取决于地面观测降水;站点稀疏区在没有站点分布时,融合降水值主要取决于卫星反演降水,但随着站点个数增加,地面观测降水在融合降水中所占比重逐渐增大,且超过了卫星反演降水的作用。可见融合降水充分有效利用了地面观测降水和卫星反演降水各自的优势,融合效果明显。
基金supported by the National Natural Science Foundation of China (Grant Nos. 41630426 & 4170506)the Youth Fund Projects of Science and Technology from Gansu Province (Grant No. 17JR5RA342)
文摘Extending across three major plateaus,namely the Qinghai-Tibetan Plateau,the Inner Mongolia-Xinjiang Plateau and the Loess Plateau,Northwest China has the complex terrain and spatio-temporal climate variations,and is affected by the interactions among different circulation systems,such as the summer monsoon,the westerlies and the plateau monsoon.The understanding of the climate variability,as well as its characteristics and evolution mechanisms in this area has been limited so far.In this paper,the precipitation characteristics and mechanisms in the eastern and western parts of Northwest China during the flood season are compared and analyzed based on the data from 192 national meteorological observational sites in Northwest China in 1961-2016.The results show that,divided by the northern boundary of the East Asian summer monsoon,there are huge differences in the precipitation variation characteristics between the eastern and western parts.The inter-annual variations,interdecadal variations and total trends in the two parts all show a significant seesaw phenomenon.Moreover,it is found that the seesaw phenomenon of precipitation variation is closely related to the opposite variation between the East Asian summer monsoon index(MI)and the westerly circulation index(WI).In addition,the inverse variations on different time scales are only related to the contributions of precipitation at specific grades.Besides,in the two matching patterns of precipitation in the seesaw phenomenon,the middle and high latitudes are occupied by the"high-low-high"wave trains in the precipitation increases in the east of Northwest China(ENWC)and decreases in the west of Northwest China(WNWC)pattern,meaning precipitation increases in ENWC and decreases in WNWC.Whereas the opposite"low-high-low"wave trains at 500 hPa height are observed in the middle and high latitudes in the WH-EA pattern at 500 hPa height,meaning precipitation increases in WNWC and decreases in ENWC.Thus,the atmosphere circulation situation with two wave train types can su
基金supported by the National Basic Research Program of China(Grant No.2009CB421405)the National Natural Science Foundation of China(Grant Nos.41025017and40921160379)partly supported by City University of Hong Kong(GrantNo.7002717)
文摘South China （SC） experienced persistent heavy rain in June 2010. The climatic anomalies and related mechanism are analyzed in this study. Results show that the large-scale circulation pattern favorable for precipitation was maintained. In the upper level, the South Asian High and westerly jet stream provided a divergent circulation over SC. In the middle and low levels, an anomalous strong subtropical high （STH） extended to the South China Sea. The southwesterly monsoon flow along the northwest flank of the STH transported abundant water vapor from the western North Pacific, the Bay of Bengal, and the South China Sea to SC. The precipitation can be classified into two types： the West Siberia low （WSL）-induced low-level cyclone mode, and the STH-induced low-level jet mode. STH and WSL indices are defined to estimate the influence of these two systems, respectively. Analysis shows that both are critical for precipitation, but their respective contributions differ from year to year. In 2010, both were important factors for the heavy rainfall in June.
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2015CB452804 and 2009CB421504)National Natural Science Foundation of China(91215302,41175063,41275066,and 41475055)
文摘The heaviest rainfall in recent six decades fell in Beijing on 21 July 2012, reaching a record of 460 mm within 18 h. This rainfall was a typical remote precipitation event related to Typhoon Vicente（1208）.Observational analysis indicates that Vicente influenced distant heavy rainfall by transporting water vapor northward to the Beijing area. This moisture transport was mainly driven by the interaction between Vicente and the western Pacific subtropical high（WPSH） associated with the formation of a low-level southeasterly moisture channel. A set of numerical sensitivity experiments were performed with prescribed typhoons of different intensities to investigate the interaction between Vicente and the WPSH and its effects on this rainstorm process. The results indicate that the WPSH interacting with typhoons of different intensities may exert varying degrees of influence on the development of a southeasterly moisture channel, resulting in a change in rain rate and location over the Beijing area. Specifically, in the presence of an enhanced typhoon,the WPSH shows remarkable withdrawal to the east, which is favorable for a northward extension of the southeasterly moisture channel, thereby increasing moisture supply for the rainstorm. The WPSH tends to stretch westward in a zonal pattern if the typhoon is weakened or removed, hindering the northward extension of the moisture channel. Thus, the rainfall area may be expected to expand or contract, with corresponding increases or decreases in rain rate over the Beijing area with a strengthened or weakened typhoon, respectively.
文摘The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15%Cr(mass fraction) in-situ composites were systematically studied and high strength and high electrical conductive Cu base in-situ composites have been developed. The best combination is the addition of 0.1% to 0.2% Zr, Ti, or Sn in Cu-15%Cr in-situ composite, thermomechanical treatment to refine the microstructure and optimizing the precipitation of second phase. The strength is controlled by high density of dislocations in the Cu matrix, the lamellar spacing of the second phase, and the fine Cr precipitates. The aging treatment to reduce solute atoms has a beneficial effect on the increase of electrical conductivity. The addition of Zr, or Ti of about 0.15% to 0.2% promotes the precipitation of Cr particles.
