为了更深入地认识不同条件下的陆-气相互作用,选取2007年1月至2008年12月兰州大学半干旱气候与环境观测站(Semi-Arid Climate and Environment Observatory of Lanzhou University,SACOL)与中科院吉林通榆观测站的湍流资料,并结合常规...为了更深入地认识不同条件下的陆-气相互作用,选取2007年1月至2008年12月兰州大学半干旱气候与环境观测站(Semi-Arid Climate and Environment Observatory of Lanzhou University,SACOL)与中科院吉林通榆观测站的湍流资料,并结合常规气象观测资料,利用Swinbank于1951年提出的涡动相关法分析三种下垫面上的湍流通量,从而定量地描述和认识陆-气相互作用,并比较分析半干旱区不同下垫面热通量和动量通量的日变化与季节变化特征。结果表明:(1)SACOL、草原站和农田站上感、潜热通量的日变化均表现为单峰型,其中感热通量Hs日峰值可分别达到140.3,157.3和144.8 W·m-2;潜热通量LvE日峰值为Hs的40%~75%。(2)夜间热通量主要集中于-22.6~24.2 W·m-2,夜间Hs一年四季均表现为负值,而LvE几乎保持正值。(3)各测站上动量通量τ具有明显日变化,但由于风向、风速差异,通榆地区τ的日峰值可达0.25 kg·m-1·s-2,而SACOL仅有0.08 kg·m-1·s-2。(4)通榆站上τ的日变化具有显著季节差异,春、秋季的日较差远大于其他季。(5)排除热力因子影响,黄土高原下垫面对湍流活动的削弱作用更强,在该下垫面上近地层大气更容易也更快趋于稳定。展开更多
利用NOAH(The Community Noah Land Surface Model)、SHAW(Simultaneous Heat and Water)和CLM(Community Land Model)3个不同的陆面过程模式及兰州大学(Semi-Arid Climate Observatory and Laboratory,SACOL)2007年的观测资料,对黄土...利用NOAH(The Community Noah Land Surface Model)、SHAW(Simultaneous Heat and Water)和CLM(Community Land Model)3个不同的陆面过程模式及兰州大学(Semi-Arid Climate Observatory and Laboratory,SACOL)2007年的观测资料,对黄土高原半干旱区的陆面过程进行了模拟研究。通过与观测值间的对比,考察不同陆面过程模式在半干旱区的适用性。研究结果表明:3个模式在半干旱区的模拟性能有较大差异。其中,CLM模式模拟的20 cm以上的浅层土壤温度最优,SHAW模式模拟的深层土壤温度最优;SHAW模式模拟的土壤含水量与观测值最为接近,而NOAH和CLM模式模拟值有较大偏差;3个模式均能较好地模拟地表反射辐射,其中SHAW模式模拟值与观测值的偏差最小;对地表长波辐射的模拟,CLM模式的模拟最优;3个模式均能较好地反映感热、潜热通量的变化趋势,其中CLM模式对感热的模拟性能优于其他两个模式,在有降水发生后的湿润条件下,CLM模式对潜热的模拟性能最优,而无降水的干燥条件下,CLM模式的模拟偏差最大,NOAH模式对冬季潜热的模拟最优。总体而言,CLM模式能够更好地再现半干旱区地气之间的相互作用,但模式对土壤含水量及干燥条件下的潜热通量的模拟较差,模式对半干旱区陆气间的水文过程还有待进一步的研究和改进。展开更多
为了改善陆面过程模式在半干旱地区的模拟能力,在SHAW(Simultaneous Heat and Water Model)模式和CoLM(Common Land Surface Model)模式参数化方案基础上,结合黄土高原SACOL站(Semi-Arid Climate and Environment Observatory of Lanzho...为了改善陆面过程模式在半干旱地区的模拟能力,在SHAW(Simultaneous Heat and Water Model)模式和CoLM(Common Land Surface Model)模式参数化方案基础上,结合黄土高原SACOL站(Semi-Arid Climate and Environment Observatory of Lanzhou University)得到的部分土壤和近地层的研究结果,利用SHAW模式的动力框架,发展了一个新的陆面过程模式TBLSHAW(Two-Big-Leaf-SHAW)。该模式由一层植被、多层土壤和湍流边界层构成。在植被层主要采取双大叶模型计算能量平衡;土壤层利用水热耦合传输模型计算土壤温度和湿度,并包含了冻融、蒸发及降水渗透等物理过程;湍流边界层采取莫宁—奥布霍夫理论计算湍流通量。最后利用SACOL站获取的观测资料,对TBLSHAW模式进行了模拟检验。结果表明,TBLSHAW模式能够合理地模拟半干旱地区各项陆面过程特征的变化趋势;模拟的土壤温度和土壤湿度与观测值的偏差较小,模式效率和相关系数较高;模拟的净短波辐射及向上长波辐射较好;但是模拟的感热通量、潜热通量与观测值偏差较大,这可能与该地区的能量闭合度较低有关,还有待进一步研究。展开更多
Arid and semi-arid areas comprise about 30% of the earth＇s surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a speci...Arid and semi-arid areas comprise about 30% of the earth＇s surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL） was established in 2005. SACOL consists of a large set of instruments and focuses on： （1） monitoring of long term tendencies in semiarid climate changes; （2） monitoring of the aerosol effect on the water cycle; （3） studies of interaction between land surface and the atmosphere; （4） improving the land surface and climate models; and （5） validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.展开更多
In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station of SACOL （Semi-Arid Climate ＆ Environment Observatory of Lanzhou University）, which i...In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station of SACOL （Semi-Arid Climate ＆ Environment Observatory of Lanzhou University）, which is located on a semi-arid grassland over the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2, momentum, and latent and sensible heat fluxes were assessed. The result showed that coordinate rotation has a great influence on the momentum flux but little on scalar fluxes. For coordinate rotation using the planar fit method, different regression planes should be determined for different wind direction sectors due to the heterogeneous nature of the ground surface. Sonic temperature correction decreased the sensible heat flux by about 9%, while WPL correction （correction for density fluctuations） increased the latent heat flux by about 10%. WPL correction is also particularly important for CO2 fluxes. Other procedures of flux corrections, such as the time delay correction and frequency response correction, do not significantly influence the turbulent fluxes. Furthermore, quality tests on stationarity and turbulence development conditions were discussed. Parameterizations of integral turbulent characteristics （ITC） were tested and a specific parameterization scheme was provided for SACOL. The ITC test on turbulence development conditions was suggested to be applied only for the vertical velocity. The combined results of the quality tests showed that about 62%-65% of the total data were of high quality for the latent heat flux and CO2 flux, and as much as about 76% for the sensible heat flux. For the momentum flux, however, only about 35% of the data were of high quality.展开更多
Although sudden nocturnal warming events near the earth＇s surface in Australia and the United States have been examined in previous studies, similar events observed occasionally over the Loess Plateau of Northwest Ch...Although sudden nocturnal warming events near the earth＇s surface in Australia and the United States have been examined in previous studies, similar events observed occasionally over the Loess Plateau of Northwest China have not yet been investigated. The factors that lead to these warming events in such areas with their unique topography and climate remain not clear. To understand the formation mechanisms and associated thermal and dynamical features, a nocturnal warming event recorded in Gansu Province （northwest of the Loess Plateau） in June 2007 was investigated by using observations and model simulations with the Weather Research and Forecasting （WRF） model. Observations showed that this near-surface warming event lasted for 4 h and the temperature increased by 2.5℃. During this event, a decrease in humidity occurred simultaneously with the increase of temperature. The model simulation showed that the nocturnal warming was caused mainly by the transport of warmer and drier air aloft downward to the surface through enhanced vertical mixing. Wind shear played an important role in inducing the elevated vertical mixing, and it was enhanced by the continuous development of the atmospheric baroclinicity, which converted more potential energy to kinetic energy.展开更多
文摘利用NOAH(The Community Noah Land Surface Model)、SHAW(Simultaneous Heat and Water)和CLM(Community Land Model)3个不同的陆面过程模式及兰州大学(Semi-Arid Climate Observatory and Laboratory,SACOL)2007年的观测资料,对黄土高原半干旱区的陆面过程进行了模拟研究。通过与观测值间的对比,考察不同陆面过程模式在半干旱区的适用性。研究结果表明:3个模式在半干旱区的模拟性能有较大差异。其中,CLM模式模拟的20 cm以上的浅层土壤温度最优,SHAW模式模拟的深层土壤温度最优;SHAW模式模拟的土壤含水量与观测值最为接近,而NOAH和CLM模式模拟值有较大偏差;3个模式均能较好地模拟地表反射辐射,其中SHAW模式模拟值与观测值的偏差最小;对地表长波辐射的模拟,CLM模式的模拟最优;3个模式均能较好地反映感热、潜热通量的变化趋势,其中CLM模式对感热的模拟性能优于其他两个模式,在有降水发生后的湿润条件下,CLM模式对潜热的模拟性能最优,而无降水的干燥条件下,CLM模式的模拟偏差最大,NOAH模式对冬季潜热的模拟最优。总体而言,CLM模式能够更好地再现半干旱区地气之间的相互作用,但模式对土壤含水量及干燥条件下的潜热通量的模拟较差,模式对半干旱区陆气间的水文过程还有待进一步的研究和改进。
文摘为了改善陆面过程模式在半干旱地区的模拟能力,在SHAW(Simultaneous Heat and Water Model)模式和CoLM(Common Land Surface Model)模式参数化方案基础上,结合黄土高原SACOL站(Semi-Arid Climate and Environment Observatory of Lanzhou University)得到的部分土壤和近地层的研究结果,利用SHAW模式的动力框架,发展了一个新的陆面过程模式TBLSHAW(Two-Big-Leaf-SHAW)。该模式由一层植被、多层土壤和湍流边界层构成。在植被层主要采取双大叶模型计算能量平衡;土壤层利用水热耦合传输模型计算土壤温度和湿度,并包含了冻融、蒸发及降水渗透等物理过程;湍流边界层采取莫宁—奥布霍夫理论计算湍流通量。最后利用SACOL站获取的观测资料,对TBLSHAW模式进行了模拟检验。结果表明,TBLSHAW模式能够合理地模拟半干旱地区各项陆面过程特征的变化趋势;模拟的土壤温度和土壤湿度与观测值的偏差较小,模式效率和相关系数较高;模拟的净短波辐射及向上长波辐射较好;但是模拟的感热通量、潜热通量与观测值偏差较大,这可能与该地区的能量闭合度较低有关,还有待进一步研究。
基金SACOL was sponsored by Lanzhou University through 985 Programthe National Basic Research Program of China under Grant No. 2006CB400501the National Natural Science Founda- tion of China under Grant Nos. 40633017 and 40725015
文摘Arid and semi-arid areas comprise about 30% of the earth＇s surface. Changes in climate and climate variability will likely have a significant impact on these regions. The Loess Plateau over Northwest China is a special semi-arid land surface and part of a dust aerosol source. To improve understanding and capture the direct evidence of the impact of human activity on the semi-arid climate over the Loess Plateau, the Semi-Arid Climate and Environment Observatory of Lanzhou University （SACOL） was established in 2005. SACOL consists of a large set of instruments and focuses on： （1） monitoring of long term tendencies in semiarid climate changes; （2） monitoring of the aerosol effect on the water cycle; （3） studies of interaction between land surface and the atmosphere; （4） improving the land surface and climate models; and （5） validation of space-borne observations. This paper presents a description of SACOL objectives, measurements, and sampling strategies. Preliminary observation results are also reviewed in this paper.
基金sponsored by the National Natural Science Foundation of China un-der Grant Nos40633017 and 40725015
文摘In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station of SACOL （Semi-Arid Climate ＆ Environment Observatory of Lanzhou University）, which is located on a semi-arid grassland over the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2, momentum, and latent and sensible heat fluxes were assessed. The result showed that coordinate rotation has a great influence on the momentum flux but little on scalar fluxes. For coordinate rotation using the planar fit method, different regression planes should be determined for different wind direction sectors due to the heterogeneous nature of the ground surface. Sonic temperature correction decreased the sensible heat flux by about 9%, while WPL correction （correction for density fluctuations） increased the latent heat flux by about 10%. WPL correction is also particularly important for CO2 fluxes. Other procedures of flux corrections, such as the time delay correction and frequency response correction, do not significantly influence the turbulent fluxes. Furthermore, quality tests on stationarity and turbulence development conditions were discussed. Parameterizations of integral turbulent characteristics （ITC） were tested and a specific parameterization scheme was provided for SACOL. The ITC test on turbulence development conditions was suggested to be applied only for the vertical velocity. The combined results of the quality tests showed that about 62%-65% of the total data were of high quality for the latent heat flux and CO2 flux, and as much as about 76% for the sensible heat flux. For the momentum flux, however, only about 35% of the data were of high quality.
基金Supported by the National Natural Science Foundation of China(41375109)National(Key)Basic Research and Development(973)Program of China(2014CB441406)Key Laboratory of Meteorological Disaster of Ministry of Education,Nanjing University of Information Science&Technology(KLME1412)
文摘Although sudden nocturnal warming events near the earth＇s surface in Australia and the United States have been examined in previous studies, similar events observed occasionally over the Loess Plateau of Northwest China have not yet been investigated. The factors that lead to these warming events in such areas with their unique topography and climate remain not clear. To understand the formation mechanisms and associated thermal and dynamical features, a nocturnal warming event recorded in Gansu Province （northwest of the Loess Plateau） in June 2007 was investigated by using observations and model simulations with the Weather Research and Forecasting （WRF） model. Observations showed that this near-surface warming event lasted for 4 h and the temperature increased by 2.5℃. During this event, a decrease in humidity occurred simultaneously with the increase of temperature. The model simulation showed that the nocturnal warming was caused mainly by the transport of warmer and drier air aloft downward to the surface through enhanced vertical mixing. Wind shear played an important role in inducing the elevated vertical mixing, and it was enhanced by the continuous development of the atmospheric baroclinicity, which converted more potential energy to kinetic energy.
