There exists great uncertainty in parameterizing snow cover fraction in most general circulation models (GCMs) using various empirical formulae, which has great influence on the performance of GCMs. This work reviews ...There exists great uncertainty in parameterizing snow cover fraction in most general circulation models (GCMs) using various empirical formulae, which has great influence on the performance of GCMs. This work reviews the commonly used relationships between region-averaged snow depth (or snow water equivalent) and snow cover extent (or fraction) and suggests a new empirical formula to compute snow cover fraction, which only depends on the domain-averaged snow depth, for GCMs with different horizontal resolution. The new empirical formula is deduced based on the 10-yr (1978-1987) 0.5°× 0.5° weekly snow depth data of the scanning multichannel microwave radiometer (SMMR) driven from the Nimbus-7 Satellite. Its validation to estimate snow cover for various GCM resolutions was tested using the climatology of NOAA satellite-observed snow cover.展开更多
The South Asian High （SAH） and precipitation over East Asia simulated by 11 coupled GCMs associated with the forthcoming Intergovernmental Panel on Climate Change＇s （IPCC） 4th Assessment Report are evaluated. The...The South Asian High （SAH） and precipitation over East Asia simulated by 11 coupled GCMs associated with the forthcoming Intergovernmental Panel on Climate Change＇s （IPCC） 4th Assessment Report are evaluated. The seasonal behavior of the SAH is presented for each model. Analyses of the results show that all models are able to reproduce the seasonal cycle of the SAH. Locations of the SAH center are also basically reproduced by these models. All models underestimate the intensity and the extension of coverage in summer. The anomalous SAH can be divided into east and west modes according to its longitudinal position in summer on the interannual timescale, and the composite anomalies of the observed precipitation for these two modes tend to have opposite signs over East Asia. However, only several coupled GCMs can simulate the relationship between rainfall and SAH similar to the observed one, which may be associated with the bias in simulation of the subtropical anticyclone over the West Pacific （SAWP） at 500 hPa. In fact, it is found that any coupled GCM, that can reproduce the reasonable summer mean state of SAWP and the southward （northward） withdrawal （extension） for the east （west） mode of SAH as compared to the observed, will also simulate similar rainfall anomaly patterns for the east and west SAH modes over East Asia. Further analysis indicates that the observed variations in the SAH, SAWP and rainfall are closely related to the sea surface temperature （SST） over the equatorial tropical Pacific. Particularly, some models cannot simulate the SAWP extending northward in the west mode and withdrawing southward in the east mode, which may be related to weak major E1 Nifio or La Nifia events. The abilities of the coupled GCMs to simulate the SAWP and ENSO events are associated partly with their ability to reproduce the observed relationship between SAH and the rainfall anomaly over East Asia.展开更多
General circulation models （GCMs） are often used in assessing the impact of climate change at global and continental scales. However, the climatic factors simulated by GCMs are inconsistent at comparatively smaller ...General circulation models （GCMs） are often used in assessing the impact of climate change at global and continental scales. However, the climatic factors simulated by GCMs are inconsistent at comparatively smaller scales, such as individual river basins. In this study, a statistical downscaling approach based on the Smooth Support Vector Machine （SSVM） method was constructed to predict daily precipitation of the changed climate in the Hanjiang Basin. NCEP/NCAR reanalysis data were used to establish the statistical relationship between the larger scale climate predictors and observed precipitation. The relationship obtained was used to project future precipitation from two GCMs （CGCM2 and HadCM3） for the A2 emission scenario. The results obtained using SSVM were compared with those from an artificial neural network （ANN）. The comparisons showed that SSVM is suitable for conducting climate impact studies as a statistical downscaling tool in this region. The temporal trends projected by SSVM based on the A2 emission scenario for CGCM2 and HadCM3 were for rainfall to decrease during the period 2011–2040 in the upper basin and to increase after 2071 in the whole of Hanjiang Basin.展开更多
Objective:To explore the phytochemical constituents from petroleum ether and diehloromethane extracts of Moringa oleifera(M.oleufera)roots using GC/GC—MS.Methods:A total of 5.11 kg fresh and undried crashed root of M...Objective:To explore the phytochemical constituents from petroleum ether and diehloromethane extracts of Moringa oleifera(M.oleufera)roots using GC/GC—MS.Methods:A total of 5.11 kg fresh and undried crashed root of M.oleifera were cut into small pieces and extracted with petroleum ether and diehloromethane(20 L.each) at room temperature for 2 d.The concentrated extracts were subjected to their GC—MS analysis.Results:The GC-MS analysis of the petroleum ether and diehloromethane extracts of M.oleifern roots,which showed promising biological activities,has resulted in the identification 102 compounds.These constituents belong to 15 classes of compounds including hydrocarbons,fatty acids,esters,alcohols,isolhioeyanate.thiocyanale,pyrazine,aromalics.alkamides.cyanides,steroids,halocompounds.urea and N-hydroxyimine derivatives,unsaturated alkenamides.alkyne and indole.GC/GC-MS studies on petroleum ether extraet of the roots revealed that it contained 39 compounds,belonging to nine classes.Cyclooctasulfur S8 has been isolated as a pure compound from the extract.The major compounds identified from petroleum ether extract were trans-13-clocosene(37.9%).nonacosane(32.6%).cycloartenol(28.6%) nonadecanoic acid(13.9%) and cyclooctasulfur S8(13.9%).Dichloromethane extract of the roots was composed of 63 compounds of which nasimizinol(58.8%) along with oleic acid(46.5%),N—benzyl-N-(7—cyanato heptanamide(38.3%),N—benzyl-N—(1—chlorononyl) amide(30.3%),bis[3—benzyl prop-2-ene]-1-one(19.5%) and N.N-dibeuzyl—2-ene pent 1.5—diamide(11.6%) were the main constituents.Conclusions:This study helps to predict the formula and structure of active molecules which can be used as drugs.This result also enhances the traditional usage of M.oleifera which possesses a number of bioactive compounds.展开更多
基金This work was conducted unlder the joint support of the National Natural Sciences Foundation of China under Grant Nos.40005008 and 40135020the Chinese Academy Project ZKCX2-SW-210.
文摘There exists great uncertainty in parameterizing snow cover fraction in most general circulation models (GCMs) using various empirical formulae, which has great influence on the performance of GCMs. This work reviews the commonly used relationships between region-averaged snow depth (or snow water equivalent) and snow cover extent (or fraction) and suggests a new empirical formula to compute snow cover fraction, which only depends on the domain-averaged snow depth, for GCMs with different horizontal resolution. The new empirical formula is deduced based on the 10-yr (1978-1987) 0.5°× 0.5° weekly snow depth data of the scanning multichannel microwave radiometer (SMMR) driven from the Nimbus-7 Satellite. Its validation to estimate snow cover for various GCM resolutions was tested using the climatology of NOAA satellite-observed snow cover.
文摘The South Asian High （SAH） and precipitation over East Asia simulated by 11 coupled GCMs associated with the forthcoming Intergovernmental Panel on Climate Change＇s （IPCC） 4th Assessment Report are evaluated. The seasonal behavior of the SAH is presented for each model. Analyses of the results show that all models are able to reproduce the seasonal cycle of the SAH. Locations of the SAH center are also basically reproduced by these models. All models underestimate the intensity and the extension of coverage in summer. The anomalous SAH can be divided into east and west modes according to its longitudinal position in summer on the interannual timescale, and the composite anomalies of the observed precipitation for these two modes tend to have opposite signs over East Asia. However, only several coupled GCMs can simulate the relationship between rainfall and SAH similar to the observed one, which may be associated with the bias in simulation of the subtropical anticyclone over the West Pacific （SAWP） at 500 hPa. In fact, it is found that any coupled GCM, that can reproduce the reasonable summer mean state of SAWP and the southward （northward） withdrawal （extension） for the east （west） mode of SAH as compared to the observed, will also simulate similar rainfall anomaly patterns for the east and west SAH modes over East Asia. Further analysis indicates that the observed variations in the SAH, SAWP and rainfall are closely related to the sea surface temperature （SST） over the equatorial tropical Pacific. Particularly, some models cannot simulate the SAWP extending northward in the west mode and withdrawing southward in the east mode, which may be related to weak major E1 Nifio or La Nifia events. The abilities of the coupled GCMs to simulate the SAWP and ENSO events are associated partly with their ability to reproduce the observed relationship between SAH and the rainfall anomaly over East Asia.
基金supported financially by the National Natural Science Foundation of China (Grant Nos.50679063 and 50809049)the International CooperationResearch Fund of China (2005DFA20520)the Re-search Fund for the Doctoral Program of Higher Education(200804861062)
文摘General circulation models （GCMs） are often used in assessing the impact of climate change at global and continental scales. However, the climatic factors simulated by GCMs are inconsistent at comparatively smaller scales, such as individual river basins. In this study, a statistical downscaling approach based on the Smooth Support Vector Machine （SSVM） method was constructed to predict daily precipitation of the changed climate in the Hanjiang Basin. NCEP/NCAR reanalysis data were used to establish the statistical relationship between the larger scale climate predictors and observed precipitation. The relationship obtained was used to project future precipitation from two GCMs （CGCM2 and HadCM3） for the A2 emission scenario. The results obtained using SSVM were compared with those from an artificial neural network （ANN）. The comparisons showed that SSVM is suitable for conducting climate impact studies as a statistical downscaling tool in this region. The temporal trends projected by SSVM based on the A2 emission scenario for CGCM2 and HadCM3 were for rainfall to decrease during the period 2011–2040 in the upper basin and to increase after 2071 in the whole of Hanjiang Basin.
文摘Objective:To explore the phytochemical constituents from petroleum ether and diehloromethane extracts of Moringa oleifera(M.oleufera)roots using GC/GC—MS.Methods:A total of 5.11 kg fresh and undried crashed root of M.oleifera were cut into small pieces and extracted with petroleum ether and diehloromethane(20 L.each) at room temperature for 2 d.The concentrated extracts were subjected to their GC—MS analysis.Results:The GC-MS analysis of the petroleum ether and diehloromethane extracts of M.oleifern roots,which showed promising biological activities,has resulted in the identification 102 compounds.These constituents belong to 15 classes of compounds including hydrocarbons,fatty acids,esters,alcohols,isolhioeyanate.thiocyanale,pyrazine,aromalics.alkamides.cyanides,steroids,halocompounds.urea and N-hydroxyimine derivatives,unsaturated alkenamides.alkyne and indole.GC/GC-MS studies on petroleum ether extraet of the roots revealed that it contained 39 compounds,belonging to nine classes.Cyclooctasulfur S8 has been isolated as a pure compound from the extract.The major compounds identified from petroleum ether extract were trans-13-clocosene(37.9%).nonacosane(32.6%).cycloartenol(28.6%) nonadecanoic acid(13.9%) and cyclooctasulfur S8(13.9%).Dichloromethane extract of the roots was composed of 63 compounds of which nasimizinol(58.8%) along with oleic acid(46.5%),N—benzyl-N-(7—cyanato heptanamide(38.3%),N—benzyl-N—(1—chlorononyl) amide(30.3%),bis[3—benzyl prop-2-ene]-1-one(19.5%) and N.N-dibeuzyl—2-ene pent 1.5—diamide(11.6%) were the main constituents.Conclusions:This study helps to predict the formula and structure of active molecules which can be used as drugs.This result also enhances the traditional usage of M.oleifera which possesses a number of bioactive compounds.
