The approach to remote sensing of water vapor by using global positioning systems(GPS)is discussed.In order to retrieve the vertical integrated water vapor(IWV)or the precipitable water (PW),the weighted“mean tempera...The approach to remote sensing of water vapor by using global positioning systems(GPS)is discussed.In order to retrieve the vertical integrated water vapor(IWV)or the precipitable water (PW),the weighted“mean temperature”of the atmosphere,T_m would be estimated to the specific area and season.T_m depends on surface temperature,tropospheric temperature profile,and the vertical distribution of water vapor.The surface temperature dependence is borne out by a comparison of T_m and the values of surface temperature T_s using radiosonde profiles of Beijing Station(No.54511)throughout 1992.The analysis of radiosonde profiles spanning a one-year interval(1992)from sites in eastern region of China with a latitude range of 20-50°N and a longitude range of 100-130°E yields the coefficients α and b of a linear regression equation T_m= α+bT_s.展开更多
A numerical model has been developed for simulating land-surface processes and atmospheric boundary layer climate of vegetation and desert in semi-arid region.Dynamically,thermal and hydrological processes take place ...A numerical model has been developed for simulating land-surface processes and atmospheric boundary layer climate of vegetation and desert in semi-arid region.Dynamically,thermal and hydrological processes take place in the atmospheric boundary layer.Vegetation and surface layer of soil are included in the soil-vegetation-atmosphere coupled system,in which,vegetation is considered as a horizontally uniform layer,soil is divided into 13 layers and the horizontal differences of variables in the system are neglected.The influence of local boundary layer climate by vegetation cover factor is simulated with the coupled model in the semi-arid region of Northwest China (around 38°N,105°E).Results indicate that due to significant differences of water and energy budgets in vegetation and desert region,the air is colder and wetter over the vegetation and correspondingly an obvious local circulation in the lower atmosphere is formed. Simulating results also show that maximum updraft and downdraft occur around the vegetation-desert marginal area,where the dynamical and thermodynamical properties of PBL (Planetary Boundary Layer) are uncontinuous.It is stronger at daytime,weaker and reverse at nighttime.In the simulation,the moisture inversion phenomena are analyzed.Finally.the influences of vegetation cover factor exchange on local boundary layer climate are simulated.The simulating results bring to light that water may be conserved and improved by developing tree planting and afforestation,and improving cover factor of vegetation in local ecoenvironment,and this is an important way of transforming local climate in arid and semi-arid area.Results indicate that the coupled model can be used to study the soil-vegetation-atmosphere interaction and local boundary layer climate.展开更多
In this paper,two schemes proposed by Julian(1984)and Krishnamauti(1986)are used to retrieve the tropical divergent wind at 200 hPa and 850 hPa from the satellite observational Outgoing Long-wave Radiation(OLR).The co...In this paper,two schemes proposed by Julian(1984)and Krishnamauti(1986)are used to retrieve the tropical divergent wind at 200 hPa and 850 hPa from the satellite observational Outgoing Long-wave Radiation(OLR).The comparison study has been conducted among the OLR-derived divergent wind field and those directly from wind fields of ECMWF and CAC tropical analysis,and NCEP/NCAR reanalysis for examining their reliability.Then,the divergent wind retrieved from OLR by using Julian's scheme is used to composite the diagrams of the Walker circulation and the local Hadley circulation during 1982—1983 ENSO event.The possible linkage between the anomalies of summer rainfall in East China during this period and the anomalous Walker and local Hadley circulations is discussed. It is shown that it is practically feasible to use the satellite observed OLR data in the estimation of the tropical divergent wind.It is aiso indicated that NCEP/NCAR reanalysis has made a progress for improving the reliability of the tropical divergent wind,though some biases still exist in the description of the intensity and position of the divergence(convergence)maximum centers over Asian monsoon region.The application of Julian's method to a diagnosis on the evolutions of the anomalous Walker and Hadley circulations during 1982—1983 ENSO event shows that the development of this ENSO event is not companied with the sudden reversal of the Walker circulation,but the propagation of the ascending branch over the western Pacific to the central- eastern Pacific and crossing through the date line,which results in a significant displacement of the vertical circulation over the West Pacific(WP)and the central-east Pacific(CEP).It is also indicated that there exists a close linkage between the change of local Hadley circulation in the WP and the Walker circulation in the CEP,implying that the Walker circulation possibly severs as a bridge between the anomalies of the SST in the CEP and the change of local Hadley circulation in Northwest Pacific.The latter is responsible for the climate anomaly over eastern China during this period.展开更多
基金the Chinese National Climbing Project"The Tibetan Plateau Meteorological Experiment"and in part by the Naltional Natural Science Foundation of China under Grant No.49675296.
基金the Chinese National Climbing Project"The Tibetan PlateauMeteorological Experiment"and in part by the NationalNatural Science Foundation of China under Grant No.49675296.
文摘The approach to remote sensing of water vapor by using global positioning systems(GPS)is discussed.In order to retrieve the vertical integrated water vapor(IWV)or the precipitable water (PW),the weighted“mean temperature”of the atmosphere,T_m would be estimated to the specific area and season.T_m depends on surface temperature,tropospheric temperature profile,and the vertical distribution of water vapor.The surface temperature dependence is borne out by a comparison of T_m and the values of surface temperature T_s using radiosonde profiles of Beijing Station(No.54511)throughout 1992.The analysis of radiosonde profiles spanning a one-year interval(1992)from sites in eastern region of China with a latitude range of 20-50°N and a longitude range of 100-130°E yields the coefficients α and b of a linear regression equation T_m= α+bT_s.
文摘A numerical model has been developed for simulating land-surface processes and atmospheric boundary layer climate of vegetation and desert in semi-arid region.Dynamically,thermal and hydrological processes take place in the atmospheric boundary layer.Vegetation and surface layer of soil are included in the soil-vegetation-atmosphere coupled system,in which,vegetation is considered as a horizontally uniform layer,soil is divided into 13 layers and the horizontal differences of variables in the system are neglected.The influence of local boundary layer climate by vegetation cover factor is simulated with the coupled model in the semi-arid region of Northwest China (around 38°N,105°E).Results indicate that due to significant differences of water and energy budgets in vegetation and desert region,the air is colder and wetter over the vegetation and correspondingly an obvious local circulation in the lower atmosphere is formed. Simulating results also show that maximum updraft and downdraft occur around the vegetation-desert marginal area,where the dynamical and thermodynamical properties of PBL (Planetary Boundary Layer) are uncontinuous.It is stronger at daytime,weaker and reverse at nighttime.In the simulation,the moisture inversion phenomena are analyzed.Finally.the influences of vegetation cover factor exchange on local boundary layer climate are simulated.The simulating results bring to light that water may be conserved and improved by developing tree planting and afforestation,and improving cover factor of vegetation in local ecoenvironment,and this is an important way of transforming local climate in arid and semi-arid area.Results indicate that the coupled model can be used to study the soil-vegetation-atmosphere interaction and local boundary layer climate.
基金This research is supported by the Chinese Ninth Five-Year National Project"Short-Range Climate Prediction System" the National Natural Science Foundation of China project for the young scientists,Grant No.49705061.
文摘In this paper,two schemes proposed by Julian(1984)and Krishnamauti(1986)are used to retrieve the tropical divergent wind at 200 hPa and 850 hPa from the satellite observational Outgoing Long-wave Radiation(OLR).The comparison study has been conducted among the OLR-derived divergent wind field and those directly from wind fields of ECMWF and CAC tropical analysis,and NCEP/NCAR reanalysis for examining their reliability.Then,the divergent wind retrieved from OLR by using Julian's scheme is used to composite the diagrams of the Walker circulation and the local Hadley circulation during 1982—1983 ENSO event.The possible linkage between the anomalies of summer rainfall in East China during this period and the anomalous Walker and local Hadley circulations is discussed. It is shown that it is practically feasible to use the satellite observed OLR data in the estimation of the tropical divergent wind.It is aiso indicated that NCEP/NCAR reanalysis has made a progress for improving the reliability of the tropical divergent wind,though some biases still exist in the description of the intensity and position of the divergence(convergence)maximum centers over Asian monsoon region.The application of Julian's method to a diagnosis on the evolutions of the anomalous Walker and Hadley circulations during 1982—1983 ENSO event shows that the development of this ENSO event is not companied with the sudden reversal of the Walker circulation,but the propagation of the ascending branch over the western Pacific to the central- eastern Pacific and crossing through the date line,which results in a significant displacement of the vertical circulation over the West Pacific(WP)and the central-east Pacific(CEP).It is also indicated that there exists a close linkage between the change of local Hadley circulation in the WP and the Walker circulation in the CEP,implying that the Walker circulation possibly severs as a bridge between the anomalies of the SST in the CEP and the change of local Hadley circulation in Northwest Pacific.The latter is responsible for the climate anomaly over eastern China during this period.
