The accuracy of the simulation of carbon and water processes largely relies on the selection of atmospheric forcing datasets when driving land surface models(LSM).Particularly in high-altitude regions,choosing appropr...The accuracy of the simulation of carbon and water processes largely relies on the selection of atmospheric forcing datasets when driving land surface models(LSM).Particularly in high-altitude regions,choosing appropriate atmospheric forcing datasets can effectively reduce uncertainties in the LSM simulations.Therefore,this study conducted four offline LSM simulations over the Tibetan Plateau(TP)using the Community Land Model version 4.5(CLM4.5)driven by four state-of-the-art atmospheric forcing datasets.The performances of CRUNCEP(CLM4.5 model default)and three other reanalysis-based atmospheric forcing datasets(i.e.ITPCAS,GSWP3 and WFDEI)in simulating the net primary productivity(NPP)and actual evapotranspiration(ET)were evaluated based on in situ and gridded reference datasets.Compared with in situ observations,simulated results exhibited determination coefficients(R2)ranging from 0.58 to 0.84 and 0.59 to 0.87 for observed NPP and ET,respectively,among which GSWP3 and ITPCAS showed superior performance.At the plateau level,CRUNCEP-based simulations displayed the largest bias compared with the reference NPP and ET.GSWP3-based simulations demonstrated the best performance when comprehensively considering both the magnitudes and change trends of TP-averaged NPP and ET.The simulated ET increase over the TP during 1982-2010 based on ITPCAS was significantly greater than in the other three simulations and reference ET,suggesting that ITPCAS may not be appropriate for studying long-term ET changes over the TP.These results suggest that GSWP3 is recommended for driving CLM4.5 in conducting long-term carbon and water processes simulations over the TP.This study contributes to enhancing the accuracy of LSM in water-carbon simulations over alpine regions.展开更多
The choices of the parameterizations for each component in a microwave emission model have significant effects on the quality of brightness temperature （Tb） sim- ulation. How to reduce the uncertainty in the Tb simu...The choices of the parameterizations for each component in a microwave emission model have significant effects on the quality of brightness temperature （Tb） sim- ulation. How to reduce the uncertainty in the Tb simulation is investigated by adopting a statistical post-processing procedure with the Bayesian model averaging （BMA） ensemble approach. The simulations by the community microwave emission model （CMEM） cou- pled with the community land model version 4.5 （CLM4.5） over China's Mainland are con- ducted by the 24 configurations from four vegetation opacity parameterizations （VOPs）, three soil dielectric constant parameterizations （SDCPs）, and two soil roughness param- eterizations （SRPs）. Compared with the simple arithmetical averaging （SAA） method, the BMA reconstructions have a higher spatial correlation coefficient （larger than 0.99） than the C-band satellite observations of the advanced microwave scanning radiometer on the Earth observing system （AMSR-E） at the vertical polarization. Moreover, the BMA product performs the best among the ensemble members for all vegetation classes, with a mean root-mean-square difference （RMSD） of 4 K and a temporal correlation coefficient of 0.64.展开更多
陆面模式CLM(Community Land Model)是目前国际上发展较为完善并被广泛应用的陆面过程模式。本文使用中国科学院寒区旱区环境与工程研究所位于青藏高原东部的若尔盖高原湿地生态系统研究站的观测资料,对CLM3.0版本及CLM4.0版本在上述地...陆面模式CLM(Community Land Model)是目前国际上发展较为完善并被广泛应用的陆面过程模式。本文使用中国科学院寒区旱区环境与工程研究所位于青藏高原东部的若尔盖高原湿地生态系统研究站的观测资料,对CLM3.0版本及CLM4.0版本在上述地区的模拟性能进行了检验与对比。通过比较观测值与模拟值,验证了模式在高原季节性冻土地区的适用性,发现CLM4.0较CLM3.0在模拟结果上有了一定提高。CLM4.0加入了未冻水参数化方案,使模式可以模拟到冬季土壤冻结后存留的未冻水,显著增加了冻融期间土壤含水量的模拟,同时减小了土壤含冰量的模拟值。并因此增大了模拟的冻土热容量,减小了热导率,使冻融期间土壤温度的模拟也有了一定改善。但是模拟中也发现对于较深层土壤,温度模拟值在冻融期间较观测显著偏低。另外,在消融(冻结)过程阶段CLM4.0模拟的土壤含水量骤增(骤降)的时间均较观测提前。消融过程、冻结过程阶段模拟时间偏短,而完全冻结、完全消融阶段模拟时间偏长。因此CLM对于高原冻土地区的模拟仍是其需要重点改进的地方之一。展开更多
利用CLM(Common Land Model)模式对我国内蒙古奈曼旗农牧交错带沙漠和农田两种不同典型下垫面的陆面过程进行了数值模拟试验,并与外场试验观测结果进行了对比分析。结果表明:无论是沙漠还是农田试验,CLM都能够较好地模拟其辐射通量和土...利用CLM(Common Land Model)模式对我国内蒙古奈曼旗农牧交错带沙漠和农田两种不同典型下垫面的陆面过程进行了数值模拟试验,并与外场试验观测结果进行了对比分析。结果表明:无论是沙漠还是农田试验,CLM都能够较好地模拟其辐射通量和土壤中的热传导特征,CLM的模拟结果能够真实地再现试验期间土壤热传导过程对天气过程的响应。相比而言,模式对沙漠地区长波辐射通量和干燥时期短波辐射通量的模拟结果好于农田,其原因可能是因为农田下垫面植被及土壤特征较沙漠复杂,有着很大的不确定性,造成了农田地表反照率和温度模拟的偏差。而对农田热传导的模拟结果好于沙漠,反映了CLM对含水量较大、持水力较强的农田下垫面的热传导模拟能力较好,而对含水量较小、持水力较弱的沙漠下垫面的热传导模拟能力相对较差。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
本文基于中国1:100万植被图、马里兰大学AVHRR森林覆盖资料和中国753个气象站点40年的降水气温资料,发展了一套用于气候模拟的中国陆面覆盖资料(Chinese land cover derived fromvegetation map,简称CLCV)。该套资料与CLM(Community Lan...本文基于中国1:100万植被图、马里兰大学AVHRR森林覆盖资料和中国753个气象站点40年的降水气温资料,发展了一套用于气候模拟的中国陆面覆盖资料(Chinese land cover derived fromvegetation map,简称CLCV)。该套资料与CLM(Community Land Model)原来所用的MODIS(Moderate Resolution I maging Spectro-radiometer)陆面覆盖资料相比有较大不同:其中裸土比例减少了14.5%,森林、灌木、草原和农作物比例分别增加了3.3%、4.8%、4.4%和0.3%,冰川、湖泊和湿地比例分别增加了0.4%、0.8%和0.6%。将CLCV和MO-DIS资料分别与全国土地资源概查汇总结果分省统计资料和基于中国1km土地利用图的土地利用资料比较表明,CLCV与两者较为接近。最后,利用CLM模式分别采用CLCV与MODIS陆面覆盖资料在中国区域内进行数值模拟,结果显示,使用CLCV资料所模拟的蒸散增加了约7.7mm/a;地表反照率、感热和径流分别减小了约0.7%、0.3W/m2和7.6mm/a;与MODIS卫星反演地表反照率和GRDC(Global Runoff Data Centre)径流资料比较表明,利用CLCV资料所模拟的地表反照率有一定改进,并能基本模拟出径流分布趋势。展开更多
基于2001年和2010年中分辨率成像光谱仪MODIS(MODerate-resolution Imaging Spectroradiometer)土地覆盖数据,利用公共陆面模式(Community Land Model, CLM)模拟真实的土地利用/覆盖变化(Land Use/Cover Change, LUCC)对地表能量平衡和...基于2001年和2010年中分辨率成像光谱仪MODIS(MODerate-resolution Imaging Spectroradiometer)土地覆盖数据,利用公共陆面模式(Community Land Model, CLM)模拟真实的土地利用/覆盖变化(Land Use/Cover Change, LUCC)对地表能量平衡和水分循环过程的影响。研究表明:1)在2001~2010年,中国LUCC最明显的区域位于干旱半干旱区过渡带、半干旱半湿润区过渡带和南方地区;中国区域荒漠减少0.92%,草地减少0.01%,农田增加0.77%,森林增加2.86%,植被覆盖度整体增加。2)在2001年和2010年两种土地利用/覆盖背景下,LUCC使大部分地区感热通量增加,植被蒸腾、蒸发潜热通量增加,土壤表面蒸发潜热通量减小。3)LUCC使大部分地区地表径流减小;中国西北东部、华北和东北地区土壤湿度减小,其他地区土壤湿度增加,仅干旱半干旱过渡带上的土壤湿度发生了显著变化。4)当典型过渡带区域由荒漠变为草地后,感热通量增加1.11 W m-2,潜热通量增加0.14 W m-2;冠层蒸腾和蒸发分别增加0.039 mm d-1、0.009 mm d-1。土壤湿度平均减小0.01 m3 m-3,且随深度增加变干更明显,这是由于根系吸收了较多深层土壤水分,以满足植被显著增加的蒸腾而产生的结果。当草地变为灌木时,其能量通量和水分循环的变化与上述结果类似。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
基金supported by the National Key Research and Development Program of China(2022YFC3201702)the National Natural Science Foundation of China(42201146,U2240226)+1 种基金the Science and Technology Project of Sichuan Province(2022NSFSC1001)Fundamental Research Funds for The Central Universities(YJ2021133).
文摘The accuracy of the simulation of carbon and water processes largely relies on the selection of atmospheric forcing datasets when driving land surface models(LSM).Particularly in high-altitude regions,choosing appropriate atmospheric forcing datasets can effectively reduce uncertainties in the LSM simulations.Therefore,this study conducted four offline LSM simulations over the Tibetan Plateau(TP)using the Community Land Model version 4.5(CLM4.5)driven by four state-of-the-art atmospheric forcing datasets.The performances of CRUNCEP(CLM4.5 model default)and three other reanalysis-based atmospheric forcing datasets(i.e.ITPCAS,GSWP3 and WFDEI)in simulating the net primary productivity(NPP)and actual evapotranspiration(ET)were evaluated based on in situ and gridded reference datasets.Compared with in situ observations,simulated results exhibited determination coefficients(R2)ranging from 0.58 to 0.84 and 0.59 to 0.87 for observed NPP and ET,respectively,among which GSWP3 and ITPCAS showed superior performance.At the plateau level,CRUNCEP-based simulations displayed the largest bias compared with the reference NPP and ET.GSWP3-based simulations demonstrated the best performance when comprehensively considering both the magnitudes and change trends of TP-averaged NPP and ET.The simulated ET increase over the TP during 1982-2010 based on ITPCAS was significantly greater than in the other three simulations and reference ET,suggesting that ITPCAS may not be appropriate for studying long-term ET changes over the TP.These results suggest that GSWP3 is recommended for driving CLM4.5 in conducting long-term carbon and water processes simulations over the TP.This study contributes to enhancing the accuracy of LSM in water-carbon simulations over alpine regions.
基金Project supported by the China Special Fund for Meteorological Research in the Public Interest(No.GYHY201306045)the National Natural Science Foundation of China(Nos.41305066 and41575096)
文摘The choices of the parameterizations for each component in a microwave emission model have significant effects on the quality of brightness temperature （Tb） sim- ulation. How to reduce the uncertainty in the Tb simulation is investigated by adopting a statistical post-processing procedure with the Bayesian model averaging （BMA） ensemble approach. The simulations by the community microwave emission model （CMEM） cou- pled with the community land model version 4.5 （CLM4.5） over China's Mainland are con- ducted by the 24 configurations from four vegetation opacity parameterizations （VOPs）, three soil dielectric constant parameterizations （SDCPs）, and two soil roughness param- eterizations （SRPs）. Compared with the simple arithmetical averaging （SAA） method, the BMA reconstructions have a higher spatial correlation coefficient （larger than 0.99） than the C-band satellite observations of the advanced microwave scanning radiometer on the Earth observing system （AMSR-E） at the vertical polarization. Moreover, the BMA product performs the best among the ensemble members for all vegetation classes, with a mean root-mean-square difference （RMSD） of 4 K and a temporal correlation coefficient of 0.64.
文摘陆面模式CLM(Community Land Model)是目前国际上发展较为完善并被广泛应用的陆面过程模式。本文使用中国科学院寒区旱区环境与工程研究所位于青藏高原东部的若尔盖高原湿地生态系统研究站的观测资料,对CLM3.0版本及CLM4.0版本在上述地区的模拟性能进行了检验与对比。通过比较观测值与模拟值,验证了模式在高原季节性冻土地区的适用性,发现CLM4.0较CLM3.0在模拟结果上有了一定提高。CLM4.0加入了未冻水参数化方案,使模式可以模拟到冬季土壤冻结后存留的未冻水,显著增加了冻融期间土壤含水量的模拟,同时减小了土壤含冰量的模拟值。并因此增大了模拟的冻土热容量,减小了热导率,使冻融期间土壤温度的模拟也有了一定改善。但是模拟中也发现对于较深层土壤,温度模拟值在冻融期间较观测显著偏低。另外,在消融(冻结)过程阶段CLM4.0模拟的土壤含水量骤增(骤降)的时间均较观测提前。消融过程、冻结过程阶段模拟时间偏短,而完全冻结、完全消融阶段模拟时间偏长。因此CLM对于高原冻土地区的模拟仍是其需要重点改进的地方之一。
文摘利用CLM(Common Land Model)模式对我国内蒙古奈曼旗农牧交错带沙漠和农田两种不同典型下垫面的陆面过程进行了数值模拟试验,并与外场试验观测结果进行了对比分析。结果表明:无论是沙漠还是农田试验,CLM都能够较好地模拟其辐射通量和土壤中的热传导特征,CLM的模拟结果能够真实地再现试验期间土壤热传导过程对天气过程的响应。相比而言,模式对沙漠地区长波辐射通量和干燥时期短波辐射通量的模拟结果好于农田,其原因可能是因为农田下垫面植被及土壤特征较沙漠复杂,有着很大的不确定性,造成了农田地表反照率和温度模拟的偏差。而对农田热传导的模拟结果好于沙漠,反映了CLM对含水量较大、持水力较强的农田下垫面的热传导模拟能力较好,而对含水量较小、持水力较弱的沙漠下垫面的热传导模拟能力相对较差。
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。
文摘本文基于中国1:100万植被图、马里兰大学AVHRR森林覆盖资料和中国753个气象站点40年的降水气温资料,发展了一套用于气候模拟的中国陆面覆盖资料(Chinese land cover derived fromvegetation map,简称CLCV)。该套资料与CLM(Community Land Model)原来所用的MODIS(Moderate Resolution I maging Spectro-radiometer)陆面覆盖资料相比有较大不同:其中裸土比例减少了14.5%,森林、灌木、草原和农作物比例分别增加了3.3%、4.8%、4.4%和0.3%,冰川、湖泊和湿地比例分别增加了0.4%、0.8%和0.6%。将CLCV和MO-DIS资料分别与全国土地资源概查汇总结果分省统计资料和基于中国1km土地利用图的土地利用资料比较表明,CLCV与两者较为接近。最后,利用CLM模式分别采用CLCV与MODIS陆面覆盖资料在中国区域内进行数值模拟,结果显示,使用CLCV资料所模拟的蒸散增加了约7.7mm/a;地表反照率、感热和径流分别减小了约0.7%、0.3W/m2和7.6mm/a;与MODIS卫星反演地表反照率和GRDC(Global Runoff Data Centre)径流资料比较表明,利用CLCV资料所模拟的地表反照率有一定改进,并能基本模拟出径流分布趋势。
文摘基于2001年和2010年中分辨率成像光谱仪MODIS(MODerate-resolution Imaging Spectroradiometer)土地覆盖数据,利用公共陆面模式(Community Land Model, CLM)模拟真实的土地利用/覆盖变化(Land Use/Cover Change, LUCC)对地表能量平衡和水分循环过程的影响。研究表明:1)在2001~2010年,中国LUCC最明显的区域位于干旱半干旱区过渡带、半干旱半湿润区过渡带和南方地区;中国区域荒漠减少0.92%,草地减少0.01%,农田增加0.77%,森林增加2.86%,植被覆盖度整体增加。2)在2001年和2010年两种土地利用/覆盖背景下,LUCC使大部分地区感热通量增加,植被蒸腾、蒸发潜热通量增加,土壤表面蒸发潜热通量减小。3)LUCC使大部分地区地表径流减小;中国西北东部、华北和东北地区土壤湿度减小,其他地区土壤湿度增加,仅干旱半干旱过渡带上的土壤湿度发生了显著变化。4)当典型过渡带区域由荒漠变为草地后,感热通量增加1.11 W m-2,潜热通量增加0.14 W m-2;冠层蒸腾和蒸发分别增加0.039 mm d-1、0.009 mm d-1。土壤湿度平均减小0.01 m3 m-3,且随深度增加变干更明显,这是由于根系吸收了较多深层土壤水分,以满足植被显著增加的蒸腾而产生的结果。当草地变为灌木时,其能量通量和水分循环的变化与上述结果类似。
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.
