The Beijing-Tianjin-Hebei urban agglomeration is currently facing severe complex air pollution. In this paper, simultaneous observations conducted in 2014 show that the annual mean concentration of fine particulate ma...The Beijing-Tianjin-Hebei urban agglomeration is currently facing severe complex air pollution. In this paper, simultaneous observations conducted in 2014 show that the annual mean concentration of fine particulate matter （PM2.5） was 84 ± 70, 86 ±60, and 118 ± 95 μg m-3 in Beijing, Tianjin, and Shijiazhuang, respectively. The mean 03 8h max in the summer was 171 ± 43, 147 ± 45, and 146 ± 44 μg m-3, respectively. This research indicates that PM2.5 and O3 are positively correlated when the temperature exceeds 20 ℃5 and the urban agglomeration shows characteristics of complex air pollution consisting of superimposed 03 and PM2.s. In summer, when the humidity was less than 55%, secondary particles and 03 also increased in a coordinated manner （y = 1.35x ＋ 29.85; R2 = 0.61）, which demonstrates severe complex pollution. However, the mean PM2.5（y） and mean 03 8 h max （x） in summer showed a negative correlation （y = - 1.3x ＋ 245; R2 = 0.61 ） in the three regions, indicating high concentrations of PM2.5 pollution partially inhibit O3 generation.展开更多
为揭示北京一次持续重污染过程的气象成因,利用北京地区常规及特种气象资料、风云二号C卫星数据及PM_(2.5)观测资料,分析了高低空环流形势、局地气象要素的动力和热力结构对其的影响。结果表明:过程期间,高空以西北或偏西气流为主,地面...为揭示北京一次持续重污染过程的气象成因,利用北京地区常规及特种气象资料、风云二号C卫星数据及PM_(2.5)观测资料,分析了高低空环流形势、局地气象要素的动力和热力结构对其的影响。结果表明:过程期间,高空以西北或偏西气流为主,地面受高压后部弱气压场和低压辐合区控制;地面呈现小风或静风的状态;850 h Pa以下相对湿度维持在80%以上;存在多层逆温且维持时间长;不利于污染物扩散的气象条件是PM_(2.5)前期积累的主因,而局地环流所形成的风场辐合线北抬是PM_(2.5)浓度在后期短时内爆发性增长的关键因素。展开更多
A hybrid grid-point statistical interpolation-ensemble transform Kalman filter (GSI-ETKF) data assimilation system for the Weather Research and Forecasting (WRF) model was developed and applied to typhoon track foreca...A hybrid grid-point statistical interpolation-ensemble transform Kalman filter (GSI-ETKF) data assimilation system for the Weather Research and Forecasting (WRF) model was developed and applied to typhoon track forecast with simulated dropsonde observations. This hybrid system showed significantly improved results with respect to tropical cyclone track forecast compared to the standard GSI system in the case of Muifa in 2011. Further analyses revealed that the flow-dependent ensemble covariance was the major contributor to the better performance of the GSI-ETKF system than the standard GSI system; the GSI-ETKF system was found to be potentially able to adjust the position of the typhoon vortex systematically and better update the environmental field.展开更多
The aerosol optical properties and chemical components of PM2.1(particulate matter with a diameter of 2.1μm or less)were investigated at Mount Gongga on the eastern slope of the Tibetan Plateau from April 2012 to Dec...The aerosol optical properties and chemical components of PM2.1(particulate matter with a diameter of 2.1μm or less)were investigated at Mount Gongga on the eastern slope of the Tibetan Plateau from April 2012 to December 2014.The annual mean aerosol optical depth(AOD)was 0.35±0.23,and the?ngstr?m exponent was 1.0±0.38.The AOD exhibited higher values in summer and winter,but lower values in spring and autumn.Dividing the observational periods into dry and wet seasons,the authors found that the concentrations of K^+,elemental carbon,secondary inorganic aerosols,and primary and secondary organic carbon in the dry(wet)season were 0.29(0.21),0.88(0.60),7.4(4.5),7.5(5.1),and 3.9(12)μg m?3,respectively.Combined with trajectory analysis,the authors found that higher concentrations of K^+,elemental carbon,and primary organic carbon indicated the effects of biomass burning from Southeast Asia during the dry season.However,the oxidation of volatile organic compounds was the main source of aerosols during the wet season,which originated from the Sichuan Basin.展开更多
Changes in surface air temperature can directly affect hydrology, agriculture, and ecosystems through extreme climate events such as heat waves. For this reason, and to improve climate change adaptation strategies, it...Changes in surface air temperature can directly affect hydrology, agriculture, and ecosystems through extreme climate events such as heat waves. For this reason, and to improve climate change adaptation strategies, it is important to investigate the ranking of hottest years. In this study, the Wilcoxon signed-ranktest and Monte Carlo simulation are used to estimate the ranking of the hottest years for theTibetan Plateau （TP） in recent decades, and the uncertainty in the ranking.The Wilcoxon signed-rank test shows that the top 10 hottest years on record over the TP mainly occur after 1998. The top three hottest years are ranked as 2006, 2009, and 2010, but there is almost no significant difference between them. When both sampling and observational errors are considered, only five years have a non-zero probability of being the hottest year, with the three highest probabilities being for the years 2006 （-47.231%）, 2009 （-40.390%）, and 2010 （-12.376%）. Similarly, with respect to a given year that is among the 10 hottest years, our results show that all the years among the ranks of 1-10 resulting from the Wilcoxon signed-rank test have probabilities above 10%, while the years 2001 and 2012 have probabilities of 3% and 4%.展开更多
Daily temperature data from 599 stations across China for the years 1961 to 2007 were used to analyze the changes in the natural regional boundaries. The results show that the accumulated temperature ≥10℃ and its du...Daily temperature data from 599 stations across China for the years 1961 to 2007 were used to analyze the changes in the natural regional boundaries. The results show that the accumulated temperature ≥10℃ and its duration changed dramatically from the end of 1990s to the early 21 st century. The amplitude of natural regional boundaries was greater in the 21st century than it was in the 20th century. In the eastern region of China, the climatic zones were migrating generally northward, with the northern edge of the subtropical zone and the eastern section of the warm temperate zone showing an obvious northward shift of up to 1-3° of latitude. The climatic zones moved south in the Qinghal-Tibet Plateau, western Inner Mongolia, and some areas of western Xinjiang, and slightly to the north in other parts of the western region.展开更多
基金partially supported by the National Basic Research Program of China[grant numbers 2016YFC0202001,973Program 2014CB441200]National Earth System Science Data Sharing Infrastructure,National Science & Technology Infrastructure of China(http://www.geodata.cn)
文摘The Beijing-Tianjin-Hebei urban agglomeration is currently facing severe complex air pollution. In this paper, simultaneous observations conducted in 2014 show that the annual mean concentration of fine particulate matter （PM2.5） was 84 ± 70, 86 ±60, and 118 ± 95 μg m-3 in Beijing, Tianjin, and Shijiazhuang, respectively. The mean 03 8h max in the summer was 171 ± 43, 147 ± 45, and 146 ± 44 μg m-3, respectively. This research indicates that PM2.5 and O3 are positively correlated when the temperature exceeds 20 ℃5 and the urban agglomeration shows characteristics of complex air pollution consisting of superimposed 03 and PM2.s. In summer, when the humidity was less than 55%, secondary particles and 03 also increased in a coordinated manner （y = 1.35x ＋ 29.85; R2 = 0.61）, which demonstrates severe complex pollution. However, the mean PM2.5（y） and mean 03 8 h max （x） in summer showed a negative correlation （y = - 1.3x ＋ 245; R2 = 0.61 ） in the three regions, indicating high concentrations of PM2.5 pollution partially inhibit O3 generation.
文摘为揭示北京一次持续重污染过程的气象成因,利用北京地区常规及特种气象资料、风云二号C卫星数据及PM_(2.5)观测资料,分析了高低空环流形势、局地气象要素的动力和热力结构对其的影响。结果表明:过程期间,高空以西北或偏西气流为主,地面受高压后部弱气压场和低压辐合区控制;地面呈现小风或静风的状态;850 h Pa以下相对湿度维持在80%以上;存在多层逆温且维持时间长;不利于污染物扩散的气象条件是PM_(2.5)前期积累的主因,而局地环流所形成的风场辐合线北抬是PM_(2.5)浓度在后期短时内爆发性增长的关键因素。
基金supported by the Project for public welfare (Meteorology) of China(Grant No.GYHY201206006)the National Natural Science Foundation of China(Grant Nos.40975067 and 41175094)
文摘A hybrid grid-point statistical interpolation-ensemble transform Kalman filter (GSI-ETKF) data assimilation system for the Weather Research and Forecasting (WRF) model was developed and applied to typhoon track forecast with simulated dropsonde observations. This hybrid system showed significantly improved results with respect to tropical cyclone track forecast compared to the standard GSI system in the case of Muifa in 2011. Further analyses revealed that the flow-dependent ensemble covariance was the major contributor to the better performance of the GSI-ETKF system than the standard GSI system; the GSI-ETKF system was found to be potentially able to adjust the position of the typhoon vortex systematically and better update the environmental field.
基金supported by the National Basic Research Program of China[grant numbers 2016YFC0202001 and 973Program 2014CB441200]the National Natural Science Foundation of China[grant numbers 41375036 and41305076]
文摘The aerosol optical properties and chemical components of PM2.1(particulate matter with a diameter of 2.1μm or less)were investigated at Mount Gongga on the eastern slope of the Tibetan Plateau from April 2012 to December 2014.The annual mean aerosol optical depth(AOD)was 0.35±0.23,and the?ngstr?m exponent was 1.0±0.38.The AOD exhibited higher values in summer and winter,but lower values in spring and autumn.Dividing the observational periods into dry and wet seasons,the authors found that the concentrations of K^+,elemental carbon,secondary inorganic aerosols,and primary and secondary organic carbon in the dry(wet)season were 0.29(0.21),0.88(0.60),7.4(4.5),7.5(5.1),and 3.9(12)μg m?3,respectively.Combined with trajectory analysis,the authors found that higher concentrations of K^+,elemental carbon,and primary organic carbon indicated the effects of biomass burning from Southeast Asia during the dry season.However,the oxidation of volatile organic compounds was the main source of aerosols during the wet season,which originated from the Sichuan Basin.
基金supported by the National Natural Science Foundation of China[grant number 41405069],[grant number91537214],[grant number 41605063]the Key Foundation of the Education Department of Sichuan Province[grant number16ZA0203]the Scientific Research Foundation of Chengdu University of Information Technology[grant number KYTZ201517],[grant number J201516],[grant number J201518]
文摘Changes in surface air temperature can directly affect hydrology, agriculture, and ecosystems through extreme climate events such as heat waves. For this reason, and to improve climate change adaptation strategies, it is important to investigate the ranking of hottest years. In this study, the Wilcoxon signed-ranktest and Monte Carlo simulation are used to estimate the ranking of the hottest years for theTibetan Plateau （TP） in recent decades, and the uncertainty in the ranking.The Wilcoxon signed-rank test shows that the top 10 hottest years on record over the TP mainly occur after 1998. The top three hottest years are ranked as 2006, 2009, and 2010, but there is almost no significant difference between them. When both sampling and observational errors are considered, only five years have a non-zero probability of being the hottest year, with the three highest probabilities being for the years 2006 （-47.231%）, 2009 （-40.390%）, and 2010 （-12.376%）. Similarly, with respect to a given year that is among the 10 hottest years, our results show that all the years among the ranks of 1-10 resulting from the Wilcoxon signed-rank test have probabilities above 10%, while the years 2001 and 2012 have probabilities of 3% and 4%.
基金supported by the National Natural Science Foundation of China (Grant No.40875053)
文摘Daily temperature data from 599 stations across China for the years 1961 to 2007 were used to analyze the changes in the natural regional boundaries. The results show that the accumulated temperature ≥10℃ and its duration changed dramatically from the end of 1990s to the early 21 st century. The amplitude of natural regional boundaries was greater in the 21st century than it was in the 20th century. In the eastern region of China, the climatic zones were migrating generally northward, with the northern edge of the subtropical zone and the eastern section of the warm temperate zone showing an obvious northward shift of up to 1-3° of latitude. The climatic zones moved south in the Qinghal-Tibet Plateau, western Inner Mongolia, and some areas of western Xinjiang, and slightly to the north in other parts of the western region.
