利用中国气象局国家气象信息中心研发的中国气象局陆面数据同化系统(China Meteorological Administration Land Data Assimilation System,CLDAS)大气近地面强迫资料,驱动美国国家大气研究中心公用陆面模式(Community Land Model,CLM3....利用中国气象局国家气象信息中心研发的中国气象局陆面数据同化系统(China Meteorological Administration Land Data Assimilation System,CLDAS)大气近地面强迫资料,驱动美国国家大气研究中心公用陆面模式(Community Land Model,CLM3.5),对中国新疆地区土壤温度时空分布进行逐小时Off-line模拟(模拟时段为2009—2012年);利用国家土壤温度自动站(新疆区域105站点)数据验证CLDAS驱动场强迫下的CLM3.5模式在中国新疆地区3个土壤层(5cm、20cm和80cm)的土壤温度模拟能力。研究发现:在月变化方面,第1层(5cm)土壤温度模拟与实测值差异最大,在每年7月最大差异达5k左右;第2层(20cm)在每年7月达最大差异(3k左右),而第3层(80cm)在每年7月均模拟的很好。造成这种现象的原因可能因为新疆地区7月前后浅层土壤温度变化剧烈,温度白天最高可达300K以上,昼夜温差大,导致模式不能很好抓住浅层土壤温度的变化趋势。研究还发现,在80cm土壤深度,模式在1月、12月的模拟结果均较前两层差。在日变化方面,研究发现:较浅的两层(5cm和20cm)土壤温度模拟值在夏季和秋季均较差。与月变化模拟结果类似的是,80cm土壤层日变化在1、12月模拟较差,然而在其他时段却模拟的很好。在小时变化方面,分析发现:第1层土壤(5cm)模拟结果在每年的1—4月及9—11月的全天(即24 h),模式也会有不同的偏差:其中,在03UTC—21UTC之间主要表现为模式结果比观测结果偏高,而在日内21UTC—00UTC主要表现为模拟结果偏小。在每年的5—8月,全天模拟值都偏小,其中在09UTC达当日最大值。而距离第2层(20cm)处的土壤温度模拟值在大部分月份都偏差较小(-1K至1k之间),并在日内12UTC偏差达到当日最大值。研究发现,在土壤20cm处,模式模拟的最大值较观测值提前,而第3层(80cm)的土壤温度基本不受日内变化影响,表现较为平稳。造成这种影响的原因可能是因为新疆地区5—8月、9—11月为昼夜温差大,深层土壤温度较浅层土壤温度温差变化小,这也造成了模式对于浅层土壤模拟较深层差的主要原因。总体研究表明:CLDAS驱动场强迫下的CLM3.5模式可较为精确的模拟中国新疆地区多年平均土壤温度时空分布,并较为准确的反映中国新疆地区土壤温度的小时、日、月及年际的变化规律。模式浅温度模拟不好的原因可能与模式参数化方案及地表参数有关,后期将继续修正该问题。展开更多
利用第二次全国土壤调查土壤质地数据（SNSS）和中国区域陆地覆盖资料（CLCV）将陆面过程模式CLM3.5（Community Land Model version 3.5）中基于联合国粮食农业组织发展的土壤质地数据（FAO）和MODIS卫星反演的陆地覆盖数据（MODIS）...利用第二次全国土壤调查土壤质地数据（SNSS）和中国区域陆地覆盖资料（CLCV）将陆面过程模式CLM3.5（Community Land Model version 3.5）中基于联合国粮食农业组织发展的土壤质地数据（FAO）和MODIS卫星反演的陆地覆盖数据（MODIS）进行了替换,使用中国气象局陆面数据同化系统（CMA Land Data Assimilation System,CLDAS）大气强迫场资料,分别驱动基于同时改进土壤质地和陆地覆盖数据的CLM3.5（CLM-new）、基于只改进陆地覆盖数据的CLM3.5（CLM-clcv）、基于只改进土壤质地数据的CLM3.5（CLM-snss）和基于原始下垫面数据的CLM3.5（CLM-ctl）,对内蒙古地区2011~2013年土壤湿度的时空变化进行模拟试验,研究下垫面改进对CLM3.5模拟土壤湿度的影响。将四组模拟结果与46个土壤水分站点观测数据进行对比分析,结果表明：相对于控制试验,CLM-clcv、CLM-snss和CLM-new都能不同程度地改进土壤湿度模拟,其中CLM-clcv主要在呼伦贝尔改进明显,CLM-snss则在除呼伦贝尔以外的大部地区改进显著,CLM-ctl模拟的土壤湿度在各层上均系统性偏大,而CLM-new模拟土壤湿度最好地反映出内蒙古地区观测的土壤湿度的时空变化特征,显著改善了土壤湿度的模拟,体现在与观测值有着更高的相关系数和更小的平均偏差与均方根误差。展开更多
Based on station observations, The European Centre for Medium-Range Weather Forecasts reanalysis （ERA40）, the National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） rean...Based on station observations, The European Centre for Medium-Range Weather Forecasts reanalysis （ERA40）, the National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis and Princeton University＇s global meteorological forcing data set （Princeton）, four atmospheric forcing fields were constructed for use in driving the Community Land Model version 3.5 （CLM3.5）. Simulated soil moisture content throughout the period 1951-2000 in the Yellow River basin was validated via comparison with corresponding observations in the upper, middle, and lower reaches. The results show that CLM3.5 is capable of reproducing not only the characteristics of intra-annual and annual variations of soil moisture, but also long-term variation trends, with different statistical significance in the correlations between the observations and simulations from different forcing fields in various reaches. The simulations modeled with station-based atmospheric forcing fields are the most consistent with observed soil moisture, and the simulations based on the Princeton data set are the second best, on average. The simulations from ERA40 and NCEP/NCAR are close to each other in quality, but comparatively worse to the other sources of forcing information that were evaluated. Regionally, simulations are most consistent with observations in the lower reaches and less so in the upper reaches, with the middle reaches in between. In addition, the soil moisture simulated by CLM3.5 is systematically greater than the observations in the Yellow River basin. Comparisons between the simulations by CLM3.5 and CLM3.0 indicate that simulation errors are primarily caused by deficiencies within CLM3.5 and are also associated with the quality of atmospheric forcing field applied.展开更多
The simulation of soil temperature on the Tibetan Plateau(TP) plays a dominant role in the performance of both global climate and numerical weather forecast models. To improve the simulation of soil temperature on the...The simulation of soil temperature on the Tibetan Plateau(TP) plays a dominant role in the performance of both global climate and numerical weather forecast models. To improve the simulation of soil temperature on the TP, the Johansen soil thermal conductivity parameterization scheme was introduced into Community Land Model 3.5(CLM3.5) and Regional Climatic Model 4(Reg CM4). The improved CLM3.5 and Reg CM4-CLM were utilized to conduct offline and regional simulation experiments on the TP. Comparison of the new and old schemes revealed that CLM3.5 provides high thermal conductivity parameters of mineral soil solid on the TP. The Johansen scheme is more practical for the TP than the soil thermal conductivity parameterization in CLM3.5. The simulation of soil temperature and liquid water content was improved in offline experiment. The improved parameterization scheme can also reduce the simulation error of soil temperature in winter throughout the entire TP.展开更多
The regional climate model RegCM4 was used to investigate the regional climate effects of land cover change over China. Two 24-year simulations （1978-2001）, one with the land cover derived from the MODIS data and th...The regional climate model RegCM4 was used to investigate the regional climate effects of land cover change over China. Two 24-year simulations （1978-2001）, one with the land cover derived from the MODIS data and the other with the CLCV （Chinese land cover derived from vegetation map） data, were conducted for a region encompassing China. The differences between the MODIS and CLCV data reflect characteristics of desertification and degradation of vegetation in China. Results indicate that the land cover change has important impacts on local climate through mechanisms related to changes in surface energy, water budgets and macro-scale circulation. In summer, the land cover change leads to a decrease in surface air temperature over southern China, a reduction in precipitation and an increase in surface air temperature in the transitional climate zone and the northern Tibetan Plateau, and an increase in inter-annual variability of surface air temperature in the marginal monsoon zone and northwestern China. Strengthened southwesterly winds increase precipitation to some extent in central and eastern Inner Mongolia by enhancing water vapor transport. In winter, enhanced northerly winds, bringing more dry and cold air, lead to a reduction in precipitation and temperature over areas south of the Yellow River.展开更多
Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and unde...Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and understanding benefit disaster alleviation,as well as weather and climate predictions based on the understanding the land-atmosphere interactions.We thus simulated soil moisture using land surface model CLM3.5 driven with observed climate in China,and corrected wet bias in soil moisture simulations via introducing soil porosity parameter into soil water parameterization scheme.Then we defined soil moisture drought to quantify spatiotemporal variability of droughts.Over the period from 1951 to 2008,40%of months(to the sum of 12×58)underwent droughts,with the average area of 54.6%of total land area of China's Mainland.The annual monthly drought numbers presented a significant decrease in arid regions,but a significant increase in semi-arid and semi-humid regions,a decrease in humid regions but not significant.The Mainland as a whole experienced an increasing drought trend,with77.3%of areal ratio of decrease to increase.The monthly droughts in winter were the strongest but the weakest in summer,impacting 54.3%and 8.4%total area of the Mainland,respectively.The drought lasting three months or more occurred mainly in the semi-arid and semi-humid regions,with probability>51.7%,even>77.6%,whereas those lasting 6 and 12 months or more impacted mainly across arid and semi-arid regions.展开更多
On the basis of station observations,an atmospheric field (ObsFC) was constructed for the Community Land Model version 3.5 (CLM3.5).The model (CLM3.5 driven with ObsFC,hereafter referred as to CLM3.5/ObsFC) was used t...On the basis of station observations,an atmospheric field (ObsFC) was constructed for the Community Land Model version 3.5 (CLM3.5).The model (CLM3.5 driven with ObsFC,hereafter referred as to CLM3.5/ObsFC) was used to simulate soil moisture (SM) from 1951 to 2008 in China.The resulting SM was compared with in situ observations,remote-sensing data and estimations made by various land models,indicating that CLM3.5/ObsFC is capable of reproducing the temporospatial characteristics and long-term variation trends of SM over China.Using an in situ observation-based forcing field improves the simulation of SM.Analysis of SM simulated using CLM3.5/ObsFC shows that the overall spatial pattern of SM was characterized by a gradually decreasing and alternating distribution of arid-humid zones from the southeast to northwest.Regionally averaged SM was the driest over southern Xinjiang Province and western Inner Mongolia,while the most humid regions were located over the Northeast Plain,Jianghuai region and the Yangtze River basin.The long-term variation trends of SM were generally characterized by increases in arid and humid regions and decreases in semiarid regions.Moreover,the variation was relatively intense from the mid-1970s to the mid-1990s in the arid region.The time series was more stable in the humid region except for a period near 1970 and after the year 2003.A downward trend was most prominent in the semiarid region from the 1990s to the end of the time series.For 1951-2008,in the arid,semiarid and humid regions,the SM volume percentage changed by 2.35,-1.26 and 0.08,respectively.The variation trends and intensity remarkably differed among the different regions,with the most notable changes being over the arid and semiarid regions north of 35°N.展开更多
文摘利用中国气象局国家气象信息中心研发的中国气象局陆面数据同化系统(China Meteorological Administration Land Data Assimilation System,CLDAS)大气近地面强迫资料,驱动美国国家大气研究中心公用陆面模式(Community Land Model,CLM3.5),对中国新疆地区土壤温度时空分布进行逐小时Off-line模拟(模拟时段为2009—2012年);利用国家土壤温度自动站(新疆区域105站点)数据验证CLDAS驱动场强迫下的CLM3.5模式在中国新疆地区3个土壤层(5cm、20cm和80cm)的土壤温度模拟能力。研究发现:在月变化方面,第1层(5cm)土壤温度模拟与实测值差异最大,在每年7月最大差异达5k左右;第2层(20cm)在每年7月达最大差异(3k左右),而第3层(80cm)在每年7月均模拟的很好。造成这种现象的原因可能因为新疆地区7月前后浅层土壤温度变化剧烈,温度白天最高可达300K以上,昼夜温差大,导致模式不能很好抓住浅层土壤温度的变化趋势。研究还发现,在80cm土壤深度,模式在1月、12月的模拟结果均较前两层差。在日变化方面,研究发现:较浅的两层(5cm和20cm)土壤温度模拟值在夏季和秋季均较差。与月变化模拟结果类似的是,80cm土壤层日变化在1、12月模拟较差,然而在其他时段却模拟的很好。在小时变化方面,分析发现:第1层土壤(5cm)模拟结果在每年的1—4月及9—11月的全天(即24 h),模式也会有不同的偏差:其中,在03UTC—21UTC之间主要表现为模式结果比观测结果偏高,而在日内21UTC—00UTC主要表现为模拟结果偏小。在每年的5—8月,全天模拟值都偏小,其中在09UTC达当日最大值。而距离第2层(20cm)处的土壤温度模拟值在大部分月份都偏差较小(-1K至1k之间),并在日内12UTC偏差达到当日最大值。研究发现,在土壤20cm处,模式模拟的最大值较观测值提前,而第3层(80cm)的土壤温度基本不受日内变化影响,表现较为平稳。造成这种影响的原因可能是因为新疆地区5—8月、9—11月为昼夜温差大,深层土壤温度较浅层土壤温度温差变化小,这也造成了模式对于浅层土壤模拟较深层差的主要原因。总体研究表明:CLDAS驱动场强迫下的CLM3.5模式可较为精确的模拟中国新疆地区多年平均土壤温度时空分布,并较为准确的反映中国新疆地区土壤温度的小时、日、月及年际的变化规律。模式浅温度模拟不好的原因可能与模式参数化方案及地表参数有关,后期将继续修正该问题。
文摘利用第二次全国土壤调查土壤质地数据（SNSS）和中国区域陆地覆盖资料（CLCV）将陆面过程模式CLM3.5（Community Land Model version 3.5）中基于联合国粮食农业组织发展的土壤质地数据（FAO）和MODIS卫星反演的陆地覆盖数据（MODIS）进行了替换,使用中国气象局陆面数据同化系统（CMA Land Data Assimilation System,CLDAS）大气强迫场资料,分别驱动基于同时改进土壤质地和陆地覆盖数据的CLM3.5（CLM-new）、基于只改进陆地覆盖数据的CLM3.5（CLM-clcv）、基于只改进土壤质地数据的CLM3.5（CLM-snss）和基于原始下垫面数据的CLM3.5（CLM-ctl）,对内蒙古地区2011~2013年土壤湿度的时空变化进行模拟试验,研究下垫面改进对CLM3.5模拟土壤湿度的影响。将四组模拟结果与46个土壤水分站点观测数据进行对比分析,结果表明：相对于控制试验,CLM-clcv、CLM-snss和CLM-new都能不同程度地改进土壤湿度模拟,其中CLM-clcv主要在呼伦贝尔改进明显,CLM-snss则在除呼伦贝尔以外的大部地区改进显著,CLM-ctl模拟的土壤湿度在各层上均系统性偏大,而CLM-new模拟土壤湿度最好地反映出内蒙古地区观测的土壤湿度的时空变化特征,显著改善了土壤湿度的模拟,体现在与观测值有着更高的相关系数和更小的平均偏差与均方根误差。
基金supported by themajor state basic research development program of China(Grant No.2006CB400504)the key program of the National Natural Science Foundation of China (Grant No.40830956)National Natural Science Foundation of China (Grant Nos.40775055,40828004)
文摘Based on station observations, The European Centre for Medium-Range Weather Forecasts reanalysis （ERA40）, the National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis and Princeton University＇s global meteorological forcing data set （Princeton）, four atmospheric forcing fields were constructed for use in driving the Community Land Model version 3.5 （CLM3.5）. Simulated soil moisture content throughout the period 1951-2000 in the Yellow River basin was validated via comparison with corresponding observations in the upper, middle, and lower reaches. The results show that CLM3.5 is capable of reproducing not only the characteristics of intra-annual and annual variations of soil moisture, but also long-term variation trends, with different statistical significance in the correlations between the observations and simulations from different forcing fields in various reaches. The simulations modeled with station-based atmospheric forcing fields are the most consistent with observed soil moisture, and the simulations based on the Princeton data set are the second best, on average. The simulations from ERA40 and NCEP/NCAR are close to each other in quality, but comparatively worse to the other sources of forcing information that were evaluated. Regionally, simulations are most consistent with observations in the lower reaches and less so in the upper reaches, with the middle reaches in between. In addition, the soil moisture simulated by CLM3.5 is systematically greater than the observations in the Yellow River basin. Comparisons between the simulations by CLM3.5 and CLM3.0 indicate that simulation errors are primarily caused by deficiencies within CLM3.5 and are also associated with the quality of atmospheric forcing field applied.
基金supported by the National Natural Science Foundation of China(91537104,41375077,41775016,41405015,and 41405016)
文摘The simulation of soil temperature on the Tibetan Plateau(TP) plays a dominant role in the performance of both global climate and numerical weather forecast models. To improve the simulation of soil temperature on the TP, the Johansen soil thermal conductivity parameterization scheme was introduced into Community Land Model 3.5(CLM3.5) and Regional Climatic Model 4(Reg CM4). The improved CLM3.5 and Reg CM4-CLM were utilized to conduct offline and regional simulation experiments on the TP. Comparison of the new and old schemes revealed that CLM3.5 provides high thermal conductivity parameters of mineral soil solid on the TP. The Johansen scheme is more practical for the TP than the soil thermal conductivity parameterization in CLM3.5. The simulation of soil temperature and liquid water content was improved in offline experiment. The improved parameterization scheme can also reduce the simulation error of soil temperature in winter throughout the entire TP.
基金supported by the National Basic Research Program (No.2010CB428403, 2010CB951001)the National Natural Science Foundation of China (No.91125016)
文摘The regional climate model RegCM4 was used to investigate the regional climate effects of land cover change over China. Two 24-year simulations （1978-2001）, one with the land cover derived from the MODIS data and the other with the CLCV （Chinese land cover derived from vegetation map） data, were conducted for a region encompassing China. The differences between the MODIS and CLCV data reflect characteristics of desertification and degradation of vegetation in China. Results indicate that the land cover change has important impacts on local climate through mechanisms related to changes in surface energy, water budgets and macro-scale circulation. In summer, the land cover change leads to a decrease in surface air temperature over southern China, a reduction in precipitation and an increase in surface air temperature in the transitional climate zone and the northern Tibetan Plateau, and an increase in inter-annual variability of surface air temperature in the marginal monsoon zone and northwestern China. Strengthened southwesterly winds increase precipitation to some extent in central and eastern Inner Mongolia by enhancing water vapor transport. In winter, enhanced northerly winds, bringing more dry and cold air, lead to a reduction in precipitation and temperature over areas south of the Yellow River.
基金supported by the National Basic Research Program of China(Grant No.2012CB956202)the National Key Technology R&D Program of China(Grant Nos.2013BAC10B02,2012BAC22B04)the National Natural Science Foundation of China(Grant No.41105048)
文摘Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and understanding benefit disaster alleviation,as well as weather and climate predictions based on the understanding the land-atmosphere interactions.We thus simulated soil moisture using land surface model CLM3.5 driven with observed climate in China,and corrected wet bias in soil moisture simulations via introducing soil porosity parameter into soil water parameterization scheme.Then we defined soil moisture drought to quantify spatiotemporal variability of droughts.Over the period from 1951 to 2008,40%of months(to the sum of 12×58)underwent droughts,with the average area of 54.6%of total land area of China's Mainland.The annual monthly drought numbers presented a significant decrease in arid regions,but a significant increase in semi-arid and semi-humid regions,a decrease in humid regions but not significant.The Mainland as a whole experienced an increasing drought trend,with77.3%of areal ratio of decrease to increase.The monthly droughts in winter were the strongest but the weakest in summer,impacting 54.3%and 8.4%total area of the Mainland,respectively.The drought lasting three months or more occurred mainly in the semi-arid and semi-humid regions,with probability>51.7%,even>77.6%,whereas those lasting 6 and 12 months or more impacted mainly across arid and semi-arid regions.
基金supported by the National Basic Research Program of China (2010 CB428404)the Key Program of the National Natural Science Foundation of China (40830956)the Special Fund for Meteorological Scientific Research in Public Interest (GYHY201106028)
文摘On the basis of station observations,an atmospheric field (ObsFC) was constructed for the Community Land Model version 3.5 (CLM3.5).The model (CLM3.5 driven with ObsFC,hereafter referred as to CLM3.5/ObsFC) was used to simulate soil moisture (SM) from 1951 to 2008 in China.The resulting SM was compared with in situ observations,remote-sensing data and estimations made by various land models,indicating that CLM3.5/ObsFC is capable of reproducing the temporospatial characteristics and long-term variation trends of SM over China.Using an in situ observation-based forcing field improves the simulation of SM.Analysis of SM simulated using CLM3.5/ObsFC shows that the overall spatial pattern of SM was characterized by a gradually decreasing and alternating distribution of arid-humid zones from the southeast to northwest.Regionally averaged SM was the driest over southern Xinjiang Province and western Inner Mongolia,while the most humid regions were located over the Northeast Plain,Jianghuai region and the Yangtze River basin.The long-term variation trends of SM were generally characterized by increases in arid and humid regions and decreases in semiarid regions.Moreover,the variation was relatively intense from the mid-1970s to the mid-1990s in the arid region.The time series was more stable in the humid region except for a period near 1970 and after the year 2003.A downward trend was most prominent in the semiarid region from the 1990s to the end of the time series.For 1951-2008,in the arid,semiarid and humid regions,the SM volume percentage changed by 2.35,-1.26 and 0.08,respectively.The variation trends and intensity remarkably differed among the different regions,with the most notable changes being over the arid and semiarid regions north of 35°N.
