一种基于TMI观测结果的海表温度反演算法   总被引：4，自引：1，他引：3  

王雨  傅云飞  刘奇  刘国胜  刘显通  程静 《气象学报》2011,69(1):149-160

基于星载微波仪器观测结果反演海表温度,能很好地克服云对反演结果的干扰,实现对海表温度全天候的监测.文中利用热带测雨卫星所搭载的微波成像仪的观测结果,建立了一种新的适用于非降水条件下的海表温度反演算法.作为一种半经验统计算法,它以辐射传输方程为基础,通过理论模拟计算,建立海表温度与微波成像仪多通道亮温之间的关系,较好地反...  相似文献   

A Study of Shallow Cumulus Cloud Droplet Dispersion by Large Eddy Simulations          下载免费PDF全文

WANG Xiaofeng  XUE Huiwen  FANG Wen  ZHENG Guoguang 《Acta Meteorologica Sinica》2011,25(2):166-175

Cloud droplet dispersion is an important parameter in estimating aerosol indirect effect on climate in general circulation models (GCMs). This study investigates droplet dispersion in shallow cumulus clouds under different aerosol conditions using three-dimensional large eddy simulations (LES). It is found that cloud droplet mean radius, standard deviation, and relative dispersion generally decrease as aerosol mixing ratio increases from 25 mg⁻¹ (clean case) to 100 mg⁻¹ (moderate case), and to 2000 mg⁻¹ (polluted case). Under all the three simulated aerosol conditions, cloud droplet mean radius and standard deviation increase with height. However, droplet relative dispersion increases with height only in the polluted case, and does not vary with height in the clean and moderate cases.  相似文献   

Spatial Distribution and Temporal Variation of the Winter Wheat Late Frost Disaster in Henan, China   总被引：1，自引：0，他引：1       下载免费PDF全文

ZHANG Xuefen  ZHENG Youfei  WANG Chunyi  CHEN Huailiang  REN Zhenhe  ZOU Chunhui 《Acta Meteorologica Sinica》2011,25(2):249-259

The winter wheat late frost disaster(WFD) occurs mainly in the Yellow and Huaihe River area,of which Henan Province covers the most part.Henan is the major area of wheat production in China,but it is severely hit by the WFD.In this study,we construct a WFD index based on the minimum temperature and the winter wheat development period(WDP).The WFD degrees and days at 30 agrometeorological stations in Henan Province during the period of 1981-2004 are calculated.For the large-scale temporal variation analysis of WFD,the 24-yr WDP observation series is relatively short,so it is expanded by using the relation between the turning green date of winter wheat and the 5-day running mean temperature and that between the stem elongation phase and the effective cumulative temperature above a critical value of 2.5 ℃.The WFD data are also expanded for the last 50 years and are analyzed by using the empirical orthogonal function(EOF) and the Morlet wavelet methods.Characteristics in the spatial distribution and temporal variation of WFD are revealed.The results show that the frequency of WFD is generally high,exceeding 40% in parts of Henan,and exhibits a rising trend in the period of 1970-1990.The variation trend of WFD degrees is similar to that of WFD days,and the areas with higher WFD degrees coincide the areas with more WFD days.Moreover,the WFD degree has a greater impact on the winter wheat yield than the WFD days.The areas with high WFD degrees lie in the southeast and southwest of Henan,and the areas with low WFD degrees lie in the south of the Huaihe River and parts of western Henan.Temporal variations of the first and second EOF modes of the WFD degree display 16-and quasi-22-yr periodicities,respectively.The areas of high(low) WFD frequency are distributed in the northern Henan and the southwest border of Henan(the northeast Henan and the middle part of southwest Henan).The temporal variation of the first(second) EOF mode of WFD days exhibits a periodicity(periodicities) of quasi-4 yr(quasi-3 and quasi-6-7 yr).  相似文献   

星载测雨雷达探测频段选择仿真研究   总被引：2，自引：2，他引：0  

吴琼  杨虎  卢乃锰 《气象学报》2011,69(2):344-351

在星载测雨雷达必须满足的3个基本条件的基础上,开展了风云三号(FY-3)星载测雨雷达最佳波段组合的研究.文中将高精度GCE(Goddard cumulus ensemble)模式中BOB飓风资料的大气廓线和水凝物廓线作为三维Quickbeam气象雷达模拟软件的输入,分别模拟了5、10、14、35和94 GHz 5个频点...  相似文献   

毫米波测云雷达的系统定标和探测能力研究   总被引：4，自引：1，他引：3  

仲凌志  刘黎平  葛润生  冯胜 《气象学报》2011,69(2):352-362

毫米波测云雷达是中国自主研制的一部双线偏振全相干8.6 mm波长的测云雷达.本文在介绍该雷达系统的参数和技术特点的同时;重点阐述了厂家用外接仪表对该雷达天线系统、发射机系统以及接收机系统等硬件参数进行测试的方法,检验了雷达回波功率动态范围的定标和测量参数的定标结果;并从理论计算,配合试验区域内另外两部10cm波长的天气...  相似文献   

Effects of Crop Growth and Development on Land Surface Fluxes   总被引：2，自引：0，他引：2  

CHEN Feng  XIE Zhenghui 《大气科学进展》2011,28(4):927-944

In this study, the Crop Estimation through Resource and Environment Synthesis model (CERES3.0) was coupled into the Biosphere-Atmosphere Transfer Scheme (BATS), which is called BATS CERES, to represent interactions between the land surface and crop growth processes. The effects of crop growth and development on land surface processes were then studied based on numerical simulations using the land surface models. Six sensitivity experiments by BATS show that the land surface fluxes underwent substantial changes when the leaf area index was changed from 0 to 6 m2 m-2. Numerical experiments for Yucheng and Taoyuan stations reveal that the coupled model could capture not only the responses of crop growth and development to environmental conditions, but also the feedbacks to land surface processes. For quantitative evaluation of the effects of crop growth and development on surface fluxes in China, two numerical experiments were conducted over continental China: one by BATS CERES and one by the original BATS. Comparison of the two runs shows decreases of leaf area index and fractional vegetation cover when incorporating dynamic crops in land surface simulation, which lead to less canopy interception, vegetation transpiration, total evapotranspiration, top soil moisture, and more soil evaporation, surface runoff, and root zone soil moisture. These changes are accompanied by decreasing latent heat flux and increasing sensible heat flux in the cropland region. In addition, the comparison between the simulations and observations proved that incorporating the crop growth and development process into the land surface model could reduce the systematic biases of the simulated leaf area index and top soil moisture, hence improve the simulation of land surface fluxes.  相似文献   

A 35-GHz Polarimetric Doppler Radar and Its Application for Observing Clouds Associated with Typhoon Nuri     

ZHONG Lingzhi  LIU Liping  FENG Sheng  GE Runsheng  ZHANG Zhe 《大气科学进展》2011,28(4):945-956

Millimeter-wavelength radar has proved to be an effective instrument for cloud observation and research. In this study, 8-mm-wavelength cloud radar (MMCR) with Doppler and polarization capabilities was used to investigate cloud dynamics in China for the first time. Its design, system specifications, calibration, and application in measuring clouds associated with typhoon are discussed in this article. The cloud radar measurements of radar reflectivity (Z), Doppler velocity (Vr), velocity spectrum width (Sw) and the depolar-ization ratio (LDR) at vertical incidence were used to analyze the microphysical and dynamic processes of the cloud system and precipitation associated with Typhoon Nuri, which occurred in southern China in August 2008. The results show the reflectivity observed using MMCR to be consistent with the echo height and the melting-layer location data obtained by the nearby China S-band new-generation weather radar (SA), but the Ka-band MMCR provided more detailed structural information about clouds and weak precipitation data than did the SA radar. The variation of radar reflectivity and LDR in vertical structure reveals the transformation of particle phase from ice to water. The vertical velocity and velocity spectrum width of MMCR observations indicate an updraft and strong turbulence in the stratiform cloud layer. MMCR provides a valuable new technology for meteorological research in China.  相似文献   

Nonlinearity and finite-time instability in a T21L3 quasigeostrophic model          下载免费PDF全文

姜智娜  王东海 《Acta Meteorologica Sinica》2011,25(4):419-429

In this paper, a nonlinear optimization method is used to explore the finite-time instability of the atmospheric circulation with a three-level quasigeostrophic model under the framework of the conditional nonlinear optimal perturbation (CNOP). As a natural generalization of linear singular vector (SV), CNOP is defined as an initial perturbation that makes the cost function the maximum at a prescribed forecast time under certain physical constraint conditions. Special attentions are paid to the different structures and energy evolutions of the optimal perturbations.  相似文献   

Simulation of the anthropogenic aerosols over South Asia and their effects on Indian summer monsoon   总被引：4，自引：2，他引：2  

Zhenming Ji  Shichang Kang  Dongfeng Zhang  Chunzi Zhu  Jia Wu  Ying Xu 《Climate Dynamics》2011,36(9-10):1633-1647

A regional climate model coupled with a chemistry-aerosol model is employed to simulate the anthropogenic aerosols including sulfate, black carbon and organic carbon and their direct effect on climate over South Asia. The model is driven by the NCAR/NCEP re-analysis data. Multi-year simulations with half, normal and double emission fluxes are conducted. Results show that the model performs well in reproducing present climate over the region. Simulations of the aerosol optical depth and surface concentration of aerosols are also reasonable although to a less extent. The negative radiative forcing is found at the top of atmosphere and largely depended on emission concentration. Surface air temperature decreases by 0.1?C0.5°C both in pre-monsoon and monsoon seasons. The range and intensity of cooling areas enlarge while aerosol emission increases. Changes in precipitation are between ?25 and 25%. Different diversifications of rainfall are showed with three emission scenarios. The changes of precipitation are consistent with varieties of monsoon onset dates in pre-monsoon season. In the regions of increasing precipitation, monsoon onset is advanced and vice versa. In northeast India and Myanmar, aerosols lead the India summer monsoon onset advancing 1?C2 pentads, and delaying by 1?C2 pentads in central and southeast India. These changes are mainly caused by the anomaly of local Hadley circulations and enhancive precipitation. Tibetan Plateau played a crucial role in the circulation changes.  相似文献   

Predictable climate dynamics of abnormal East Asian winter monsoon: once-in-a-century snowstorms in 2007/2008 winter   总被引：1，自引：0，他引：1  

Zhiwei Wu  Jianping Li  Zhihong Jiang  Jinhai He 《Climate Dynamics》2011,37(7-8):1661-1669

In 2008 (January–February), East Asia (EA) experiences the most severe and long-persisting snowstorm in the past 100 years. Results in this study show that 2007/2008 winter is dominant by the third principal mode of the East Asian winter monsoon (EAWM) which explains 8.7% of the total surface air temperature variance over EA. Significantly distinguished from the first two leading modes, the third mode positive phase features an increased surface pressure over the northwestern EA, an enhanced central Siberian high (CSH), a strengthened and northwestward extended western Pacific subtropical high (WPSH) and anomalously strong moisture transport from western Pacific, Arabian Sea and Bay of Bengal to EA. It also exhibits an intimate linkage with the sea surface temperature anomalies (SSTAs) in the Arctic Ocean areas adjacent to northern Eurasian continent, central North Pacific and northeastern Pacific. Such SSTAs emerge in prior autumn and persist through ensuing winter, signifying precursory conditions for the anomalous third EAWM mode. Numerical experiments with a simple general circulation model demonstrate that the Arctic SSTAs excite geo-potential height anomalies over northern Eurasian continent and impacts on the CSH, while the extra-tropical Pacific SSTAs deform the WPSH. Co-effects of them play crucial roles on origins of the third EAWM mode. Based on these results, an empirical model is established to predict the third mode of the EAWM. Hindcast is performed for the 1957–2008 period, which shows a quite realistic prediction skill in general and good prediction ability in the extreme phase of the third mode of the EAWM such as 2007/2008 winter. Since all these predictors can be readily monitored in real time, this empirical model provides a real time forecast tool and may facilitate the seasonal prediction of high-impact weather associated with the abnormal EAWM.  相似文献