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1.
Blacklist methods are used in the CMA Global Forecasting System (CMA-GFS) to improve the application of aircraft temperature data to numerical weather prediction in the Northern Hemisphere and the tropics. In this paper, the ERA5 re-analysis data are used to analyze aircraft temperature observation errors of each aircraft and a blacklist is established using pre-quality controls and threshold methods. The blacklist-filtered and blacklisted aircraft temperature data are then applied to the four-dimensional variational assimilation system, respectively, and an assimilation cycle forecast for the period from September 1 to 30, 2019 is carried out. The results show an uneven distribution in the global aircraft blacklist data. After the application of the blacklist methods, the RMSE of geopotential height and temperature analysis field decrease in the vertical direction by a maximum of ~ 1.5 gpm at 200 hPa and ~ 0.15 K at 250 hPa, respectively. Overall, the blacklist methods of aircraft temperature data improve the analysis and forecast in the CMA-GFS. 相似文献
2.
Incorporation of parameter uncertainty into spatial interpolation using Bayesian trans-Gaussian kriging 总被引：2，自引：0，他引：2
Quantitative precipitation estimation(QPE) plays an important role in meteorological and hydrological applications.Ground-based telemetered rain gauges are widely used to collect precipitation measurements. Spatial interpolation methods are commonly employed to estimate precipitation fields covering non-observed locations. Kriging is a simple and popular geostatistical interpolation method, but it has two known problems: uncertainty underestimation and violation of assumptions.This paper tackles these problems and seeks an optimal spatial interpolation for QPE in order to enhance spatial interpolation through appropriately assessing prediction uncertainty and fulfilling the required assumptions. To this end, several methods are tested: transformation, detrending, multiple spatial correlation functions, and Bayesian kriging. In particular, we focus on a short-term and time-specific rather than a long-term and event-specific analysis. This paper analyzes a stratiform rain event with an embedded convection linked to the passing monsoon front on the 23 August 2012. Data from a total of 100 automatic weather stations are used, and the rainfall intensities are calculated from the difference of 15 minute accumulated rainfall observed every 1 minute. The one-hour average rainfall intensity is then calculated to minimize the measurement random error. Cross-validation is carried out for evaluating the interpolation methods at regional and local levels. As a result,transformation is found to play an important role in improving spatial interpolation and uncertainty assessment, and Bayesian methods generally outperform traditional ones in terms of the criteria. 相似文献
3.
The Xin'anjiang Model is used as the basic model to develop a monthly grid-based macroscalehydrological model for the assessment of the effects of climate change on water resources.Themonthly discharge from 1953 through 1985 in the Huaihe River Basin is simulated.The sensitivityanalysis on runoff is made under assumed climatic scenarios.There is a good agreement betweenthe observed and simulated runoff.Due to the increase of time interval and decrease ofprecipitation intensity on monthly time scale,there is no monthly runoff in some model girds as themomhly hydrological model is applied to the Huaihe River Basin.Two methods of downscalingmonthly precipitation to daily resolution are validated by running the Xin'anjiang model withmonthly data at a daily time step.and the model outputs are more realistic than the monthlyhydrological model.The metbods of downscaling of monthly precipitation to daily resolution mayprovide an idea in solving the problem of the shortage of daily data.In the research of the climatechange on water resources,the daily hydrological model can be used instead of the monthly one. 相似文献
4.
Back propagation neural networks are used to retrieve atmospheric temperature profiles from NOAA-16 Advanced Microwave Sounding Unit-A (AMSU-A) measurements over East Asia. The collocated radiosonde observation and AMSU-A data over land in 2002-2003 are used to train the network, and the data over land in 2004 are used to test the network. A comparison with the multi-linear regression method shows that the neural network retrieval method can significantly improve the results in all weather conditions. When an offset of 0.5 K or a noise level of ±0.2 K is added to all channels simultaneously, the increase in the overall root mean square (RMS) error is less than 0.1 K. Furthermore, an experiment is conducted to investigate the effects of the window channels on the retrieval. The results indicate that the brightness temperatures of window channels can provide significantly useful information on the temperature retrieval near the surface. Additionally, the RMS errors of the profiles retrieved with the trained neural network are compared with the errors from the International Advanced TOVS (ATOVS) Processing Package (IAPP). It is shown that the network-based algorithm can provide much better results in the experiment region and comparable results in other regions. It is also noted that the network can yield remarkably better results than IAPP at the low levels and at about the 250-hPa level in summer skies over ocean. Finally, the network-based retrieval algorithm developed herein is applied in retrieving the temperature anomalies of Typhoon Rananim from AMSU-A data. 相似文献
5.
LIU Li WANG Tijian SUN Zhenhai WANG Qingeng ZHUANG Bingliang HAN Yong LI Shu 《大气科学进展》2012,29(6):1264-1278
Turbulence characteristics of an atmospheric surface layer over a coastal mountain area were investigated under different coordinate frames.Performances of three methods of coordinate rotation:double rotation(DR),triple rotation(TR),and classic planar-fit rotation(PF) were examined in terms of correction of eddy covariance flux.Using the commonly used DR and TR methods,unreasonable rotation angles are encountered at low wind speeds and cause significant run-to-run errors of some turbulence characteristics.The PF method rotates the coordinate system to an ensemble-averaged plane,and shows large tilt error due to an inaccurate fit plane over variable terrain slopes.In this paper,we propose another coordinate rotation scheme.The observational data were separated into two groups according to wind direction.The PF method was adapted to find an ensemble-averaged streamline plane for each group of hourly runs with wind speed exceeding 1.0 m s 1.Then,the coordinate systems were rotated to their respective bestfit planes for all available hourly observations.We call this the PF10 method.The implications of tilt corrections for the turbulence characteristics are discussed with a focus on integral turbulence characteristics,the spectra of wind-velocity components,and sensible heat and momentum fluxes under various atmospheric stabilities.Our results show that the adapted application of PF provides greatly improved estimates of integral turbulence characteristics in complex terrain and maintains data quality.The comparisons of the sensible heat fluxes for four coordinate rotation methods to fluxes before correction indicate that the PF10 scheme is the best to preserve consistency between fluxes. 相似文献
6.
Whether the initial conditions contain pronounced mesoscale signals is important to the simulation of the southwest vortex. An eastward-moving southwest vortex is simulated using the PSU/NCAR MM5. A modest degree of success is achieved, but the most serious failure is that the formation and displacement of the simulated vortex in its early phase are about fourteen hours later than the observed vortex. Considering the relatively sparse data on the mesoscale vortex and in an attempt to understand the cause of the forecast failure, an adjoint model is used to examine the sensitivity of the southwest vortex to perturbations of initial conditions. The adjoint sensitivity indicates how small perturbations of model variables at the initial time in the model domain can influence the vortex. A large sensitivity for zonal wind is located under 400 hPa, a large sensitivity for meridional wind is located under 500 hPa, a large sensitivity for temperature is located between 500 and 900 hPa, and almost all of the large sensitivity areas are located in the southwestern area. Based on the adjoint sensitivity results, perturbations are added to initial conditions to improve the simulation of the southwest vortex. The results show that the initial conditions with perturbations can successfully simulate the formation and displacement of the vortex; the wind perturbations added to the initial conditions appear to be a cyclone circulation under the middle level of the atmosphere in the southwestern area with an anticyclone circulation to its southwest; a water vapor perturbation added to initial conditions can strengthen the vortex and the speed of its displacement. 相似文献
7.
A Multivariate Empirical Orthogonal Function-Based Scheme for the Balanced Initial Ensemble Generation of an Ensemble Kalman Filter 
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下载免费PDF全文 The initial ensemble perturbations for an ensemble data assimilation system are expected to reasonably sample model uncertainty at the time of analysis to further reduce analysis uncertainty. Therefore, the careful choice of an initial ensemble perturbation method that dynamically cycles ensemble perturbations is required for the optimal performance of the system. Based on the multivariate empirical orthogonal function (MEOF) method, a new ensemble initialization scheme is developed to generate balanced initial perturbations for the ensemble Kalman filter (EnKF) data assimilation, with a reasonable consideration of the physical relationships between different model variables. The scheme is applied in assimilation experiments with a global spectral atmospheric model and with real observations. The proposed perturbation method is compared to the commonly used method of spatially-correlated random perturbations. The comparisons show that the model uncertainties prior to the first analysis time, which are forecasted from the balanced ensemble initial fields, maintain a much more reasonable spread and a more accurate forecast error covariance than those from the randomly perturbed initial fields. The analysis results are further improved by the balanced ensemble initialization scheme due to more accurate background information. Also, a 20-day continuous assimilation experiment shows that the ensemble spreads for each model variable are still retained in reasonable ranges without considering additional perturbations or inflations during the assimilation cycles, while the ensemble spreads from the randomly perturbed initialization scheme decrease and collapse rapidly. 相似文献
8.
The North–East Corridor(NEC) Testbed project is the 3rd of three NIST(National Institute of Standards and Technology) greenhouse gas emissions testbeds designed to advance greenhouse gas measurements capabilities. A design approach for a dense observing network combined with atmospheric inversion methodologies is described. The Advanced Research Weather Research and Forecasting Model with the Stochastic Time-Inverted Lagrangian Transport model were used to derive the sensitivity of hypothetical observations to surface greenhouse gas emissions(footprints). Unlike other network design algorithms, an iterative selection algorithm, based on a k-means clustering method, was applied to minimize the similarities between the temporal response of each site and maximize sensitivity to the urban emissions contribution. Once a network was selected, a synthetic inversion Bayesian Kalman filter was used to evaluate observing system performance. We present the performances of various measurement network configurations consisting of differing numbers of towers and tower locations. Results show that an overly spatially compact network has decreased spatial coverage, as the spatial information added per site is then suboptimal as to cover the largest possible area, whilst networks dispersed too broadly lose capabilities of constraining flux uncertainties. In addition, we explore the possibility of using a very high density network of lower cost and performance sensors characterized by larger uncertainties and temporal drift. Analysis convergence is faster with a large number of observing locations, reducing the response time of the filter. Larger uncertainties in the observations implies lower values of uncertainty reduction. On the other hand, the drift is a bias in nature, which is added to the observations and,therefore, biasing the retrieved fluxes. 相似文献
9.
To solve the problem of mesoscale analysis error accumulation after a period of continuous cycle data assimilation (CCDA), a blending method and a constraining method are compared to introduce global analysis information into the Global/Regional Assimilation and Prediction Enhanced System mesoscale three-dimensional variational data assimilation system (GRAPES-Meso 3Dvar). Based on a spatial filter used to obtain a blended analysis, the blending method is weighted toward the T639 global analysis for scales larger than the cutoff wavelength of 1,200 km and toward the GRAPES mesoscale analysis for wavelengths below that. The constraining method considers the T639 global analysis data as an extra source of information to be added in the 3DVar cost function. The cloud-resolving GRAPES-Meso system (3 km resolution) with a 3 h analysis cycle update is chosen, and forecast experiments on an extreme precipitation event over the eastern part of China are presented. The comparison shows that the inclusion of large-scale information with both methods has a positive impact on the regional model, in which the 3 h background forecasts are slightly closer to the radiosonde observations. The results also show that both methods are effective in improving large-scale analysis while reserving the well-featured mesoscale information, leading to an enhancement in the balance and accuracy of the analysis. Subjective verification reveals that the introduction of large-scale information has a visible beneficial impact on the forecast of precipitation location and intensity. The methodologies and experiences presented in this paper could serve as a reference for ongoing efforts toward the development of multi-scale analysis in GRAPES-Meso. 相似文献
10.
Xuefen ZHANG Liangxu LI Rongkang YANG Ran GUO Xia SUN Jianping LUO Hongbin CHEN Daxin LIU Kebing TANG Wenwu PENG Xiaodong HAN Qiyun GUO Xiaoxia LI Xikun FEI 《大气科学进展》2021,38(4):531-537
In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yilong-10 high-altitude large unmanned aerial vehicle(UAV). The Yilong-10 UAV carried a self-developed dropsonde system and a millimeter-wave cloud radar system. In addition, a solar-powered unmanned surface vessel and two drifting buoys were used. The experiment was further supported by an intelligent, reciprocating horizontal drifting radiosonde system that was deployed from the Sansha Meteorological Observing Station, with the intent of producing a stereoscopic observation over the South China Sea. Comprehensive three-dimensional observations were collected using the system from 31 July to2 August, 2020. This information was used to investigate the formation and development processes of Typhoon Sinlaku(2020). The data contain measurements of 21 oceanic and meteorological parameters acquired by the five devices, along with video footage from the UAV. The data proved very helpful in determining the actual location and intensity of Typhoon Sinlaku(2020). The experiment demonstrates the feasibility of using a high-altitude, large UAV to fill in the gaps between operational meteorological observations of marine areas and typhoons near China, and marks a milestone for the use of such data for analyzing the structure and impact of a typhoon in the South China Sea. It also demonstrates the potential for establishing operational UAV meteorological observing systems in the future, and the assimilation of such data into numerical weather prediction models. 相似文献
11.
3种再分析资料基本统计量比较 总被引：2，自引：0，他引：2
为了评估中国气象部门整理的资料的特色和应用价值,使用统计方法检验了中国资料和NCEP/NCAR、ECMWF再分析资料7月100 hPa、500 hPa位势高度场和1月海平面气压场的气候均值和年际方差的差异显著性,并比较了1月和7月北半球主要大气活动中心面积、强度指数的年际变化差异和相关程度。结果表明：1）ECMWF再分析资料7月100 hPa、500 hPa位势高度场的气候均值都显著小于中国资料,且其历年值分别小于1 660、588 dagpm,与中国资料相比不适合用于研究南亚高压、副热带高压;2）中国资料是由单层等压面图上直接读数得到的,更接近实际观测值,更适宜于诊断单个等压面上的气压系统;3）3种资料冬季蒙古高压、阿留申低压的年际变化一致性要好于夏季南亚高压、副热带高压。 相似文献
12.
气象信息科学视算环境及其若干问题 总被引：5，自引：2，他引：3
多维动态气象数据的科学视算环境通过多视角的图形、图像表达方式 ,能够直接、准确地展示复杂多样的天气过程及其时空演变 ,辅助解释人员和预报人员形成天气系统的四维空间 /时间结构 ,已成为天气系统分析的重要工具。文中首先讨论了描述天气系统和天气过程的常用图形、图像表达方式 ,然后通过若干典型天气系统数值模拟结果的示例分析 ,介绍了目前气象信息科学视算环境的主要功能 ,最后结合当前的应用状况和气象科学发展的需求 ,讨论了气象信息科学视算环境中的若干问题及其解决方案 ,并展望了未来气象信息科学视算环境的发展前景。 相似文献
13.
An estimate of roughness length is required by some atmospheric models and is also used in the logarithmic profile to determine the increase of wind speed with height under neutral conditions. The choice of technique for determining roughness lengths is generally constrained by the available input data. Here, we compare sets of roughness lengths derived by different methods for the same site and evaluate their impact on the prediction of the vertical wind speed profile.Wind speed and direction data have been collected at four heights over a three-year period at the North Norfolk Wind Monitoring Site. Wind speed profiles were used to generate sector roughness lengths based on the logarithmic profile formula. This is the only direct way of determining roughness lengths. The simplest and cheapest method is to use maps with published tables giving roughness length estimates for different terrain types. Alternatively Wieringa (1976, 1986) and Beljaars (1987) give formulae for determining roughness lengths from wind speed gusts or standard deviations.The four sets of estimated roughness lengths vary considerably. They were used to estimate 34 m wind speeds from 12.7 m observations. The profile-derived roughnesses are used simply as a check on the prediction of the wind speed profiles. The terrain-derived roughness lengths give reasonable results. Gust-derived and standard deviation roughnesses both predict wind speeds which are lower than the observed ones. The error is greater in the case of standard deviation roughnesses. If stability corrections are applied in the prediction of the vertical wind speed profile, the results are considerably improved. 相似文献
14.
GPS掩星反演大气温湿资料具有高垂直分辨率、高精度、受云和降水影响小等优点,针对GRAPES同化预报系统,发展设计了一种既考虑预报模式高度-地形追随垂直坐标不均匀分层特点,又结合掩星反演资料特性的新适应性垂直稀疏化方案。通过个例试验和批量试验,探索了该适应性稀疏化方案对分析预报质量的影响。试验结果表明:选取合适的稀疏参数,新稀疏化方案的GPS掩星反演资料对背景场的调整更加有效,分析场质量更高;位势高度、比湿、温度和风场等预报场的均方根误差均更小;适应性稀疏化方案对改善台风路径预报具有积极作用。批量试验则进一步证实了适应性稀疏化方案对分析场质量有明显的改善作用。 相似文献
15.
以江西省376个气象自动观测站的逐小时气温数据为基准,采用偏差、相关性和平均绝对误差等评价指标,对比分析2017—2022年CLDAS陆面同化和ERA5 Land再分析气温资料在江西省的适用性。结果表明： 1） ERA5 Land、CLDAS资料均能很好反映大部分站点的气温变化,CLDAS资料与观测资料的相关系数为0.99,相关系数区间分布较为集中;ERA5 Land资料与观测资料的相关系数为0.97,分布较为分散。2） 相较于观测站点多年平均气温,CLDAS资料较为接近,ERA5 Land资料则偏离较大。3） CLDAS资料的平均绝对误差明显低于ERA5 Land资料,二者均存在平原、盆地部分站点平均绝对误差较小而局部高海拔山区站点异常偏大的空间特征,以及秋季最大而冬季最小的季节特征。4） ERA5 Land资料偏差的日变化范围为-0.65—0.39 ℃,整体呈现单谷形分布;CLDAS资料偏差日变化范围为-0.05—0.05 ℃,波动幅度较小,没有明显的变化特征。5） 两种格点资料均能较好反映大部分站点的低温日数变化,但对于高温日数变化,ERA5 Land资料偏差较大,CLDAS资料偏差较小。 相似文献
16.
云分辨尺度下一种综合调整水物质含量的闪电资料同化方法 总被引：3，自引：0，他引：3
在直接调整水汽含量（称为F12）和直接调整冰相粒子浓度（称为Q14）两种闪电资料同化方法的基础上,提出了一种综合调整冰相粒子浓度和水汽含量（称为C17）的闪电资料同化方法,选取一次具有完整闪电观测资料（云闪加地闪）的飑线过程,利用WRF在云分辨尺度进行数值模拟,详细比较了3种闪电资料同化方法的模拟结果。与不进行闪电资料同化的控制试验相比,闪电资料同化试验明显改进了模式对流活动的模拟能力,但是不同同化方法有所差异。在同化时段内,F12方法中回波强度较小,形成大范围层云区,回波中心比实测偏向下游;Q14方法回波强度和落区同实测最为接近,但是对层云区的模拟无明显改进;C17方法综合了F12和Q14方法的优势,与F12方法相比,回波强度增大,落区更加接近实测,层云区面积扩大。同化结束后,F12方法冷池有所增强,雨区向东北方向延伸,但是强度较弱,形成大范围的弱降水区,同化正面效果保持最久;Q14方法低层大气偏干,地表冷池偏强,对流系统迅速移动并衰减,降水区域比实测偏南,同化正面效果消失较快;C17方法冷池范围和强度与实际观测最为接近,降水较F12方法增强,模拟出的飑线形态得到调整,模拟出了实测中的另一降水中心,同化正面效果保持时间延长。 相似文献
17.
Jieshun Zhu Bohua Huang Magdalena A. Balmaseda James L. Kinter III Peitao Peng Zeng-Zhen Hu Lawrence Marx 《Climate Dynamics》2013,41(9-10):2785-2795
Currently, ensemble seasonal forecasts using a single model with multiple perturbed initial conditions generally suffer from an “overconfidence” problem, i.e., the ensemble evolves such that the spread among members is small, compared to the magnitude of the mean error. This has motivated the use of a multi-model ensemble (MME), a technique that aims at sampling the structural uncertainty in the forecasting system. Here we investigate how the structural uncertainty in the ocean initial conditions impacts the reliability in seasonal forecasts, by using a new ensemble generation method to be referred to as the multiple-ocean analysis ensemble (MAE) initialization. In the MAE method, multiple ocean analyses are used to build an ensemble of ocean initial states, thus sampling structural uncertainties in oceanic initial conditions (OIC) originating from errors in the ocean model, the forcing flux, and the measurements, especially in areas and times of insufficient observations, as well as from the dependence on data assimilation methods. The merit of MAE initialization is demonstrated by the improved El Niño and the Southern Oscillation (ENSO) forecasting reliability. In particular, compared with the atmospheric perturbation or lagged ensemble approaches, the MAE initialization more effectively enhances ensemble dispersion in ENSO forecasting. A quantitative probabilistic measure of reliability also indicates that the MAE method performs better in forecasting all three (warm, neutral and cold) categories of ENSO events. In addition to improving seasonal forecasts, the MAE strategy may be used to identify the characteristics of the current structural uncertainty and as guidance for improving the observational network and assimilation strategy. Moreover, although the MAE method is not expected to totally correct the overconfidence of seasonal forecasts, our results demonstrate that OIC uncertainty is one of the major sources of forecast overconfidence, and suggest that the MAE is an essential component of an MME system. 相似文献
18.
基于R语言的NetCDF文件分析和可视化应用 总被引：3，自引：0，他引：3
气象领域目前有多种广泛应用的气象数据分析和可视化工具集,包括GrADS、NCL、CDO和IDL等。R语言是一种由统计学家开发的统计计算和绘图的语言和环境,具有大数据处理的能力。R语言数量众多的扩展包为R语言用于海量气象数据分析和可视化提供了强有力的支持。基于R语言对NCEP发布的数据集进行了统计分析和可视化,展示了R语言在气象数据处理和可视化方面的应用。结合R语言提供的贝叶斯统计扩展包和高性能并行计算扩展包探讨了R语言在气象数据处理和可视化应用方面的广泛前景。 相似文献
19.
为了解决带电作业时手臂末端输出力的准确控制,提出一种基于表面肌电信号（sEMG信号）和支持向量机回归（SVR）实现对手臂末端施力的评估方法.通过手握机械手臂末端的手柄,做往复推拉运动,记录此时手柄处的力传感器的数据F,同时利用3组肌电信号传感器同步采集手臂的肌电信号.将肌电信号提取特征后,与力F组合成样本集合S,在样本集合中随机抽取50%的样本数据作为训练集,分别训练BP神经网络、GRNN神经网络以及SVR神经网络.最后用训练好的神经网络对整个样本集中的力F进行预测,并用均方根误差和相关系数评估模型的预测效果.结果显示,SVR神经网络的预测效果较好,其均方根误差为3.074 0,相关系数为0.951 7. 相似文献
20.
In operational data assimilation systems, observation-error covariance matrices are commonly assumed to be diagonal.However, inter-channel and spatial observation-error correlations are inevitable for satellite radiances. The observation errors of the Microwave Temperature Sounder(MWTS) and Microwave Humidity Sounder(MWHS) onboard the FengYun-3A(FY-3A) and FY-3B satellites are empirically assigned and considered to be uncorrelated when they are assimilated into the WRF model's Community Variational Data Assimilation System(WRFDA). To assimilate MWTS and MWHS measurements optimally, a good characterization of their observation errors is necessary. In this study, background and analysis residuals were used to diagnose the correlated observation-error characteristics of the MWTS and MWHS. It was found that the error standard deviations of the MWTS and MWHS were less than the values used in the WRFDA. MWTS had small inter-channel errors, while MWHS had significant inter-channel errors. The horizontal correlation length scales of MWTS and MWHS were about 120 and 60 km, respectively. A comparison between the diagnosis for instruments onboard the two satellites showed that the observation-error characteristics of the MWTS or MWHS were different when they were onboard different satellites. In addition, it was found that the error statistics were dependent on latitude and scan positions.The forecast experiments showed that using a modified thinning scheme based on diagnosed statistics can improve forecast accuracy. 相似文献