Conditional nonlinear optimal perturbation (CNOP),which is a natural extension of singular vector (SV) into the nonlinear regime,is applied to ensemble prediction study by using a quasi-geostrophic model under the per...Conditional nonlinear optimal perturbation (CNOP),which is a natural extension of singular vector (SV) into the nonlinear regime,is applied to ensemble prediction study by using a quasi-geostrophic model under the perfect model assumption. SVs and CNOPs have been utilized to generate the initial pertur-bations for ensemble prediction experiments. The results are compared for forecast lengths of up to 14 d. It is found that the forecast skill of samples,in which the first SV is replaced by CNOP,is com-paratively higher than that of samples composed of only SVs in the medium range (day 6―day 14). This conclusion is valid under the condition that analysis error is a kind of fast-growing ones regardless of its magnitude,whose nonlinear growth is faster than that of SV in the later part of the forecast. Fur-thermore,similarity index and empirical orthogonal function (EOF) analysis are performed to explain the above numerical results.展开更多
The circulation, hygrothermal property and moisture transport character of typical hot and humid weather were analyzed in Beijing areas from July 30 to August 4, 2002. It was pointed out that, under the control of sub...The circulation, hygrothermal property and moisture transport character of typical hot and humid weather were analyzed in Beijing areas from July 30 to August 4, 2002. It was pointed out that, under the control of subtropical anticyclone which stretches to the west and north, downdraft suppresses the lifting of lower-troposphere moisture, which makes moisture keep in the lower troposphere. That is the direct reason causing hot and humid weather. Considering the non-uniformity saturated character in real atmosphere, generalized moist potential vorticity (GMPV) equation is derived by the introduction of generalized moist potential temperature concept. The analysis of GMPV shows that negative GMPV anomaly occurs in the lower troposphere. It has indicative sense to hot and humid weather. Thus, the GMPV anomaly can be utilized to identify this kind of weather and to make a short-term prediction.展开更多
The spatial resolution of general circulation models （GCMs） is too coarse to represent regional climate variations at the regional, basin, and local scales required for many environmental modeling and impact assessm...The spatial resolution of general circulation models （GCMs） is too coarse to represent regional climate variations at the regional, basin, and local scales required for many environmental modeling and impact assessments. Weather research and forecasting model （WRF） is a nextgeneration, fully compressible, Euler non-hydrostatic mesoscale forecast model with a runtime hydrostatic option. This model is useful for downscaling weather and climate at the scales from one kilometer to thousands of kilometers, and is useful for deriving meteorological parameters required for hydrological simulation too. The objective of this paper is to validate WRF simulating 5 km/ 1 h air temperatures by daily observed data of China Meteorological Administration （CMA） stations, and by hourly in-situ data of the Watershed Allied Telemetry Experimental Research Project. The daily validation shows that the WRF simulation has good agreement with the observed data; the R2 between the WRF simulation and each station is more than 0.93; the absolute of meanbias error （MBE） for each station is less than 2℃; and the MBEs of Ejina, Mazongshan and Alxa stations are near zero, with R2 is more than 0.98, which can be taken as an unbiased estimation. The hourly validation shows that the WRF simulation can capture the basic trend of observed data, the MBE of each site is approximately 2℃, the R2 of each site is more than 0.80, with the highest at 0.95, and the computed and observed surface air temperature series show a significantly similar trend.展开更多
基金the State Key Development Program for Basic Research of China (Grant No.2006CB400503)the Chinese Academy of Sciences (Grant No.KZCX3-SW-230)the National Natural Science Foundation of China (Grant Nos.40221503 and 40675030)
文摘Conditional nonlinear optimal perturbation (CNOP),which is a natural extension of singular vector (SV) into the nonlinear regime,is applied to ensemble prediction study by using a quasi-geostrophic model under the perfect model assumption. SVs and CNOPs have been utilized to generate the initial pertur-bations for ensemble prediction experiments. The results are compared for forecast lengths of up to 14 d. It is found that the forecast skill of samples,in which the first SV is replaced by CNOP,is com-paratively higher than that of samples composed of only SVs in the medium range (day 6―day 14). This conclusion is valid under the condition that analysis error is a kind of fast-growing ones regardless of its magnitude,whose nonlinear growth is faster than that of SV in the later part of the forecast. Fur-thermore,similarity index and empirical orthogonal function (EOF) analysis are performed to explain the above numerical results.
基金This work was supported by the National Key Basic Research and Development Project of China(Grant No.TG1999045700)International Key Cooperation Sciences and Technology Project(Grant No.2004DFA06100)+1 种基金the Olympic Project of Chinese Academy Sciceces(Grant No.KACX1-02)projects of the National Natural Science Foundation of China(Grant Nos.40505009 and 40405007).
文摘The circulation, hygrothermal property and moisture transport character of typical hot and humid weather were analyzed in Beijing areas from July 30 to August 4, 2002. It was pointed out that, under the control of subtropical anticyclone which stretches to the west and north, downdraft suppresses the lifting of lower-troposphere moisture, which makes moisture keep in the lower troposphere. That is the direct reason causing hot and humid weather. Considering the non-uniformity saturated character in real atmosphere, generalized moist potential vorticity (GMPV) equation is derived by the introduction of generalized moist potential temperature concept. The analysis of GMPV shows that negative GMPV anomaly occurs in the lower troposphere. It has indicative sense to hot and humid weather. Thus, the GMPV anomaly can be utilized to identify this kind of weather and to make a short-term prediction.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 40901202, 40925004）, and the National High Technology Research and Development Program of China （Grant No. 2009AA122104）. The input data for WRF model are from the Research Data Archive （RDA） which is maintained by the Computational and Information Systems Laboratory （CISL） at the National Center for Atmo- spheric Research （NCAR）. The original data are available from the RDA （http：//dss.ucar.edu） in Dataset No. ds083.2.
文摘The spatial resolution of general circulation models （GCMs） is too coarse to represent regional climate variations at the regional, basin, and local scales required for many environmental modeling and impact assessments. Weather research and forecasting model （WRF） is a nextgeneration, fully compressible, Euler non-hydrostatic mesoscale forecast model with a runtime hydrostatic option. This model is useful for downscaling weather and climate at the scales from one kilometer to thousands of kilometers, and is useful for deriving meteorological parameters required for hydrological simulation too. The objective of this paper is to validate WRF simulating 5 km/ 1 h air temperatures by daily observed data of China Meteorological Administration （CMA） stations, and by hourly in-situ data of the Watershed Allied Telemetry Experimental Research Project. The daily validation shows that the WRF simulation has good agreement with the observed data; the R2 between the WRF simulation and each station is more than 0.93; the absolute of meanbias error （MBE） for each station is less than 2℃; and the MBEs of Ejina, Mazongshan and Alxa stations are near zero, with R2 is more than 0.98, which can be taken as an unbiased estimation. The hourly validation shows that the WRF simulation can capture the basic trend of observed data, the MBE of each site is approximately 2℃, the R2 of each site is more than 0.80, with the highest at 0.95, and the computed and observed surface air temperature series show a significantly similar trend.
