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971.
Application and Study of Precipitation Schemes in Weather Simulation in Summer and Winter over China 下载免费PDF全文
XU Guoqiang WAN Qilin HUANG Liping XUE Jishan CHEN Dehui 《Acta Meteorologica Sinica》2006,20(1):28-38
Through simulation of summer and winter precipitation cases in China, the cloud precipitation schemes of model were examined. Results indicate that it is discrepant between convective precipitation simulated by the Kain-Fritsch (KF) scheme and Betts-Miller (BM) scheme in summer, the former scheme is better than the latter in this case. The ambient atmosphere may be varied by different convective schemes. The air is wetter and the updraft is stronger in the KF scheme than in the BM scheme, which can induce the more grid scale precipitation in the KF scheme, i.e., the different cumulus schemes may have the different and important effect on the grid scale precipitation. However, there is almost no convective rain in winter in northern China, so the effect of cumulus precipitation on the grid scale precipitation can be disregarded. Therefore, the gird scale precipitation is primary in the winter of northern China. 相似文献
972.
We analyze the space velocities of blue supergiants, long-period Cepheids, and young open star clusters (OSCs), as well as the H I and H II radial-velocity fields by the maximum-likelihood method. The distance scales of the objects are matched both by comparing the first derivatives of the angular velocity Ω′ determined separately from radial velocities and proper motions and by the statistical-parallax method. The former method yields a short distance scale (for R0=7.5 kpc, the assumed distances should be increased by 4%), whereas the latter method yields a long distance scale (for R0=8.5 kpc, the assumed distances should be increased by 16%). We cannot choose between these two methods. Similarly, the distance scale of blue supergiants should be shortened by 9% and lengthened by 3%, respectively. The H II distance scale is matched with the distance scale of Cepheids and OSCs by comparing the derivatives Ω′ determined for H II from radial velocities and for Cepheids and OSCs from space velocities. As a result, the distances to H II regions should be increased by 5% in the short distance scale. We constructed the Galactic rotation curve in the Galactocentric distance range 2–14 kpc from the radial velocities of all objects with allowance for the difference between the residual-velocity distributions. The axial ratio of the Cepheid+OSC velocity ellipsoid is well described by the Lindblad relation, while σu≈σv for gas. The following rotation-curve parameters were obtained: Ω0=(27.5±1.4) km s?1 kpc?1 and A=(17.1±0.5) km s?1 kpc?1 for the short distance scale (R0=7.5 kpc); and Ω0=(26.6±1.4) km s?1 kpc?1 and A=(15.4±0.5) km s?1 kpc?1 for the long distance scale (R0=8.5 kpc). We propose a new method for determining the angular velocity Ω0 from stellar radial velocities alone by using the Lindblad relation. Good agreement between the inferred Ω0 and our calculations based on space velocities suggests that the Lindblad relation holds throughout the entire sample volume. Our analysis of the heliocentric velocities for samples of young objects reveals noticeable streaming motions (with a velocity lag of ~7 km s?1 relative to the LSR), whereas a direct computation of the perturbation amplitudes in terms of the linear density-wave theory yields a small amplitude for the tangential perturbations. 相似文献
973.
张学庄 《武汉大学学报(信息科学版)》2002,27(6):611-615
讨论了光电测距仪的乘常数问题,并举出了按光电测距仪检定规程(试行)JJG703-90检测得到的乘常数(R)不正确的例子,分析了R误差大的原因。 相似文献
974.
太阳活动百年尺度的跃变与气候跃变的相关分析 总被引:10,自引:5,他引:5
讨论了2500多年来太阳黑子周期长度(SCL)的跃变特征,发现有在年尺度上SCL基本在平均值附近变化,而其变率则存在明显的跃变现象,当SCL的变率增大时,气候随之发生冷跃变,反之,则发生暖跃变。小冰期内,太阳活动弱且不稳定,与地球气候冷且不稳定具有同时性。 相似文献
975.
将小波分析的方法应用于大气边界层风、温场结构的研究,表明了这种方法应用于大气边界层研究的优越性。小波分析方法与谱分析方法,多尺度分析方法可以互补。当研究不同尺度湍流的串级过程和突变气象场的位置时,小波方法更为优越。 相似文献
976.
977.
978.
针对像素图数学基础变换问题 ,提出了一种间接变换思路 ,给出了具体的变换方法 ,包括整块变换和分块变换及拼接等问题 ,并作了相关的实验。 相似文献
979.
Frontogenesis, evolution and the time scale of front formation 总被引:1,自引:0,他引:1
Frontogenesis,EvolutionandtheTimeScaleofFrontFormationFangJuan(方娟)andWuRongsheng(伍荣生)SevereMesoscalemeteorologicalResearchLab... 相似文献
980.
Jun Yang 《地震学报(英文版)》1998,11(4):455-465
The relation of tidal factor value to tiltmeter type has been founded from the harmonic analysis for observational data. The
relation is deducted theoretically. It is discovered that the frequency responses of different type tiltmeters and operative
periods or damping constant are slightly different in same station. The tiltmeter of small operative period is able to receive
more precursory information. That is the tidal factors obtained from harmonic analysis for observed data on tiltmeter of different
damping constant are different. The relation between frequency response and tidal factor is searched. It is necessary to calibrate
absolutely tiltmeter to predict earthquake. In order to obtain any amount of ground tilt information, it is necessary to select
appropriately different frequency tiltmeters to make comprehensive observation.
The study is sponsored by the Chinese Joint Seismological Science Foundation, No. 91100. 相似文献