风云四号气象卫星地面测距系统精度改进技术     

贾耀红  任立清  郭强 《气象科技》2020,48(5):630-634

风云四号静止气象卫星(FY-4)地面测距系统用于获得分布在不同地方的5个地面站到卫星的精确距离,进而利用得到的距离数据确定并预报卫星的轨道和位置,所以测距精度是影响卫星轨道和位置确定精度的主要因素。本文根据测距系统工作的原理及过程,分析影响测距精度的误差来源,从测距体制、站址坐标测量、地面设备时延测量、转发器时延测量、大气传输时延测量和各站时间同步几个方面分析了风云四号测距系统为了提高测距精度采取的相应的技术手段。  相似文献   

太原大气能见度影响因子分析及能见度预报     

卢盛栋  陈立瑾  赵桂香  张泽秀  段鹏飞 《沙漠与绿洲气象(新疆气象)》2020,14(4):105-112

利用2017年1月—2019年12月太原地区逐时气象资料,分析了能见度及其主要影响因子的变化特征,并对两次低能见度过程进行深入分析,构建了能见度预报模型并进行检验,结果表明:(1)从空间分布看,太原北部能见度明显高于南部地区。从时间分布看,太原地区平均能见度最大值出现在5月,最小值出现在1月;日间最低值出现在06:00(北京时,下同),冬季略向后推移,最高值出现在15:00前后。(2)2017—2019年太原地区低能见度分别出现93、84、79 d;低能见度发生时,干霾、湿霾发生频率分别为59.27%、40.73%;湿霾发生时,能见度降低更加明显。(3)所选个例中,能见度均随各影响因子有所起伏,干霾、湿霾过程中能见度分别与颗粒物浓度、相对湿度变化一致。(4)采用神经网络方法构建太原地区能见度预报模型,预报模型相关系数为0.81,均方根为4.43 km,平均绝对误差为17.39%,轻微级能见度的TS评分为87%。神经网络方法对太原地区能见度预报具有较高的参考价值。  相似文献   

Statistical Downscaling Based on Dynamically DownscaledPredictors： Application to Monthly Precipitation in Sweden   总被引：3，自引：0，他引：3  

Cecilia HELLSTR?M  Deliang CHEN 《大气科学进展》2003,20(6):951-958

A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation.  相似文献   

The role of land surface dynamics in glacial inception: a study with the UVic Earth System Model   总被引：5，自引：2，他引：3  

K. J. Meissner  A. J. Weaver  H. D. Matthews  P. M. Cox 《Climate Dynamics》2003,21(7-8):515-537

The first results of the UVic Earth System Model coupled to a land surface scheme and a dynamic global vegetation model are presented in this study. In the first part the present day climate simulation is discussed and compared to observations. We then compare a simulation of an ice age inception (forced with 116 ka BP orbital parameters and an atmospheric CO₂ concentration of 240 ppm) with a preindustrial run (present day orbital parameters, atmospheric [CO₂] = 280 ppm). Emphasis is placed on the vegetations response to the combined changes in solar radiation and atmospheric CO₂ level. A southward shift of the northern treeline as well as a global decrease in vegetation carbon is observed in the ice age inception run. In tropical regions, up to 88% of broadleaf trees are replaced by shrubs and C₄ grasses. These changes in vegetation cover have a remarkable effect on the global climate: land related feedbacks double the atmospheric cooling during the ice age inception as well as the reduction of the meridional overturning in the North Atlantic. The introduction of vegetation related feedbacks also increases the surface area with perennial snow significantly.  相似文献   

Performance of the Rossby Centre regional atmospheric model in Southern Sweden: comparison of simulated and observed precipitation   总被引：1，自引：1，他引：0  

C. Achberger  M.-L. Linderson  D. Chen 《Theoretical and Applied Climatology》2003,76(3-4):219-234

Summary Two climate model simulations made with the Rossby Centre regional Atmospheric model version 1 (RCA1) are evaluated for the precipitation climate in Scania, southernmost Sweden. These simulations are driven by the HadCM2 and the ECHAM4/OPYC3 global circulation models (GCMs) for 10 years. Output from the global and the regional simulations are compared with an observational data set, constructed from a dense precipitation gauge network in Scania. Area-averaged time series corresponding to the size and location of the RCA1 grid points in Scania have been created (the Scanian Data Set). This data set was compared to a commonly used gridded surface climatology provided by the Climatic Research Unit (CRU). Relatively large differences were found, mainly due to the fact that the CRU-climatology uses fewer stations and lacks a correction for rain-gauge under-catch. This underlines the importance of the data set chosen for model evaluations. The validation is carried out at a large scale including the whole area of Scania and at the finest resolution of RCA1 (the grid point level). When integrated over the whole area of Scania, RCA1 improves the shape of the annual precipitation cycle and the inter-annual variability compared to output from the GCMs. The RCA1 control climate is generally too wet compared to the observations. At the grid point level, RCA1 improves the simulation of the variability compared to the GCMs. There is a strong positive correlation between precipitation and altitude in all seasons in the observations. This relationship is, however, much weaker and even reversed in the RCA1 simulations. Analysis of the dense rain gauge network reveals features of spatial variability at around 20–35km in the area and indicates that a finer resolution is needed if the spatial variability in the area is to be better captured by RCA1.  相似文献   

Winter cyclone frequencies in thirteen models participating in the Atmospheric Model Intercomparison Project (AMIP1)   总被引：1，自引：0，他引：1  

S. Lambert  J. Sheng  J. Boyle 《Climate Dynamics》2002,19(1):1-16

Various aspects of the simulated behaviour of cyclones in thirteen models participating in the AMIP1 exercise are presented. In the simulation of the winter climatological mean sea level pressure field for the Northern Hemisphere, the models produce reasonable simulations of the "semi-permanent" features of the climatology. The greatest departures from the observed climatology occur near the exit regions of the oceanic storm tracks; i.e., over northwestern North America, over and to the west of the British Isles and in the Mediterranean. The departures in the three geographical areas are very systematic in that at least eleven of the models exhibit similar departures from observations. In the Southern Hemisphere the intensity of the circumpolar trough is generally well simulated but positioned slightly too far north. Most models exhibit errors south of Africa, New Zealand, and South America. The simulations of the cyclone events show that the models are reasonably successful in reproducing the large-scale aspects of observed cyclone events but deficiencies in the details of the simulations are apparent. The paucity of simulated events to the south of the Alps and to the east of the Rockies suggests that the models have difficulty simulating lee cyclogenesis. Over much of North America, the models have difficulty simulating the correct level of synoptic activity as demonstrated by the low numbers of both cyclone events and anticyclone events. The models have difficulty simulating the distribution of cyclone events as a function of central pressure. The most common problem is that the models exhibit an ever increasing deficit of events with decreasing central pressure. This problem is more apparent in the Southern Hemisphere than in the Northern Hemisphere and does not appear to be resolution dependent. There is an apparent ENSO signal in the observed Northern Hemisphere interannual variability of intense winter cyclone events. With the exception of ECMWF, the models fail to reproduce this phenomenon. There is some evidence that the models do indeed respond to the interannual variability in the SSTs, but the response tends to be negatively correlated with that of the real atmosphere. In the Southern Hemisphere, there does not appear to be ENSO-induced interannual variability in the observed numbers of cyclone events. Consequently, it could be argued that the models have been reasonably successful in the Southern Hemisphere since they, like the observations, do not exhibit any ENSO-induced interannual variability.  相似文献   

国家级地面自动站A文件质量控制方法及软件开发   总被引：21，自引：4，他引：21  

王新华  罗四维  刘小宁  任芝花  孙化南 《气象》2006,32(3):107-112

地面自动站A文件是以站月为单位的气象观测综合资料，具有要素多、信息量大的特点。为了实现有效的质量控制，研究了更为全面的国家级的质量控制方法并遵循软件工程理论，采用模块化的设计方法完成了应用软件的开发，这对保证我国地面自动站观测数据的质量起到了重要作用。  相似文献   

一次夏季东北冷涡中积云发展过程的数值模拟   总被引：3，自引：7，他引：3  

耿树江  王建捷  宫福久 《气象科学》2006,26(2):149-156

运用中国科学院大气物理所设计开发的三维冰雹云模式,对2002年7月11日至15日期间,发生在中国东北地区的一次由冷涡天气诱发的积云对流变化过程进行三维数值模拟。模拟结果表明:(1)冷涡诱发的积云自然降水呈中小尺度复合体的特征;(2)积云起源于低层暖湿区域里,并由强上升气流抬升到高层,得到充分发展;(3)冷涡中积云同样存在液态水累积区,一般出现在最大上升气流上,其中液态水含量随着积云的发展而变化,冰雹即在此液态水累积区0℃以下的区域内生长;(4)在模拟区域内,模拟出了多个积云单体的并合现象,而后发展为积云团;(5)模拟出的积云形态与雷达回波基本吻合。  相似文献   

Further Study on Identifying Anomalous Large-Scale Rainfall Regimes in Phase Space          下载免费PDF全文

REN Hongli  GAO Li  ZHANG Peiqun  LI Weijing 《Acta Meteorologica Sinica》2006,20(1):62-71

Using a 40-yr daily precipitation dataset including 134 stations from 1962 to 2001, the large-scale distribution patterns of precipitation anomalies over East China are investigated in the present paper. In the phase space spanned by the first 8 EOFs generated from the 20-day low-pass filtered data, the six rainfall regimes (RRs) are identified by applying a cluster analysis method, namely, the northeastern China regime, Yellow River regime, Qinling Mountain-Huaihe River regime, Yangtze River with its south regime, South China regime, and rainless regime. Analyses show that the new RRs exhibit good persistence and evident physical sense, and excellently represent both of countrywide and regional features, which also demonstrate the inhomogeneity of multi-dimensional phase space. Furthermore, it is more important that the new RRs can describe intraseasonal dynamic characteristics of large-scale rainfall anomalies, which is the most significant difference between the new RRs and the conventional seasonal mean rainfall patterns. On the other hand, the climatic characteristics of daily distributions of the RRs events, as well as the 40-year panorama of the RRs occurring are also investigated, which further document rationality and objectivity of the RRs with intraseasonal variability, and are likely to present more helpful information for short-term climate prediction, compared with other previous classical rainfall patterns.  相似文献   

Tangling Turbulence and Semi-Organized Structures in Convective Boundary Layers     

T. Elperin  N. Kleeorin  I. Rogachevskii  S. S. Zilitinkevich 《Boundary-Layer Meteorology》2006,119(3):449-472

A new mean-field theory of turbulent convection is developed based on the idea that only the small-scale region of the spectrum is considered as turbulence, whereas its large-scale part, including both regular and semi-organized motions, is treated as the mean flow. In the shear-free regime, this theory predicts the convective wind instability, which causes the formation of large-scale semi-organized motions in the form of cells. In the presence of wind shear, the theory predicts another type of instability, which causes the formation of large-scale semi-organized structures in the form of rolls and the generation of convective-shear waves propagating perpendicular to the convective rolls. The spatial characteristics of these structures, such as the minimum size of the growing perturbations and the size of perturbations with the maximum growth rate, are determined. This theory might be useful for understanding the origin of large-scale cells and rolls observed in the convective boundary layer and laboratory turbulent convection  相似文献