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931.
932.
微型无人驾驶飞机探空初步试验研究 总被引:4,自引:1,他引:4
马舒庆 《南京气象学院学报》1997,20(2):171-177
对具有自动导航,自动驾驶功能的微型无人驾驶飞机探空的可行性进行了初步研究。设计了水平空速归零测风方式,利用全球定位系统测风,进行了微型无人驾驶飞机探测试验。研究表明,微型无人驾驶飞机可成为一种方便,经济,灵活的探空工具。 相似文献
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该文将循环神经网络(recurrent neural network,RNN)应用于雷达临近预报。使用预测循环神经网络(predictive RNN)架构,利用雷达历史组合反射率因子建模,给出雷达组合反射率因子未来1 h的预报结果。预测循环神经网络的核心是在长短时记忆单元(long short-term memory,LSTM)中增加时空记忆模块,能够提取雷达回波不同尺度的空间特征,配合循环神经网络架构,可以有效解决反射率因子预测问题。北京大兴雷达和广州雷达长时间序列的独立检验结果和2个强对流天气个例检验结果表明:该方法和传统的基于交叉相关法的1 h雷达外推临近预报相比,在20 dBZ和30 dBZ检验项目内,临界成功指数(CSI)可以提升0.15~0.30,命中率(POD)提高0.15~0.25,虚警率(FAR)降低0.15~0.20,该方法对反射率因子强度变化有一定预报能力。 相似文献
936.
Jinshuai?Ruan Xiaohang?WenEmail author Guangzhou?Fan Deqin?Li Wei?Hua Bingyun?Wang Yi?Zhang Mingjun?Zhang Chao?Wang Lei?Wang 《Theoretical and Applied Climatology》2018,134(3-4):817-828
To study the land surface and atmospheric meteorological characteristics of non-uniform underlying surfaces in the semi-arid area of Northeast China, we use a “High-Resolution Assimilation Dataset of the water-energy cycle in China (HRADC)”. The grid points of three different underlying surfaces were selected, and their meteorological elements were averaged for each type (i.e., mixed forest, grassland, and cropland). For 2009, we compared and analyzed the different components of leaf area index (LAI), soil temperature and moisture, surface albedo, precipitation, and surface energy for various underlying surfaces in Northeast China. The results indicated that the LAI of mixed forest and cropland during the summer is greater than 5 m2 m?2 and below 2.5 m2 m?2 for grassland; in the winter and spring seasons, the Green Vegetation Fraction (GVF) is below 30%. The soil temperature and moisture both vary greatly. Throughout the year, the mixed forest is dominated by latent heat evaporation; in grasslands and croplands, the sensible heat flux and the latent heat flux are approximately equal, and the GVF contributed more to latent heat flux than sensible heat flux in the summer. This study compares meteorological characteristics between three different underlying surfaces of the semi-arid area of Northeast China and makes up for the insufficiency of purely using observations for the study. This research is important for understanding the water-energy cycle and transport in the semi-arid area. 相似文献
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The potential role of tropical Pacific forcing in driving the seasonal variability of the Arctic Oscillation (AO) is explored
using both observational data and a simple general circulation model (SGCM). A lead–lag regression technique is first applied
to the monthly averaged sea surface temperature (SST) and the AO index. The AO maximum is found to be related to a negative
SST anomaly over the tropical Pacific three months earlier. A singular value decomposition (SVD) analysis is then performed
on the tropical Pacific SST and the sea level pressure (SLP) over the Northern Hemisphere. An AO-like atmospheric pattern
and its associated SST appear as the second pair of SVD modes. Ensemble integrations are carried out with the SGCM to test
the atmospheric response to different tropical Pacific forcings. The atmospheric response to the linear fit of the model’s
empirical forcing associated with the SST variability in the second SVD modes strongly projects onto the AO. Idealized thermal
forcings are then designed based on the regression of the seasonally averaged tropical Pacific precipitation against the AO
index. Results indicate that forcing anomalies over the western tropical Pacific are more effective in generating an AO-like
response while those over the eastern tropical Pacific tend to produce a Pacific-North American (PNA)-like response. The physical
mechanisms responsible for the energy transport from the tropical Pacific to the extratropical North Atlantic are investigated
using wave activity flux and vorticity forcing formalisms. The energy from the western tropical Pacific forcing tends to propagate
zonally to the North Atlantic because of the jet stream waveguide effect while the transport of the energy from the eastern
tropical Pacific forcing mostly concentrates over the PNA area. The linearized SGCM results show that nonlinear processes
are involved in the generation of the forced AO-like pattern. 相似文献
940.
Numerical simulations of anomalies of precipitation and surface air temperature in china in the summer of 1997 总被引:1,自引:0,他引:1
1.IntroductionStatisticalstudiesdemonstratedthatinEINinoyearstheprecipitationinsummerintheChangjiangRiverandHuaiheRiverBasinsisprobablyabovethenormalwhileitispossiblybelowthenormalinthenorthernChinaandtheHetao(theGreatBendoftheHuangheRiver)region.ThetemperatureinsummerisusuallylowerthannormalinEastAsia,especiallyinNortheastChina.Therewere6yearswithseverelowtemperaturesince1951,andtheyare1954,1957,1964,1972,1976and1983,whichareallrelatedtotheEINinoyears(seeHuangetal.,1989,1992;Xiangand… 相似文献