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Route-based road weather forecasting is increasingly becoming the standard methodology for winter maintenance decision making (i.e. whether or not to salt the road network) by the highway industry in the UK. Route-based forecasting requires, for the first time, the accuracy of forecasts around routes and away from sensor sites to be verified. This is essential so that end users have confidence in the models’ ability to accurately predict road surface temperature at every point around their road network. A new methodology for verifying route-based forecasts is proposed that uses clustering techniques to create clusters of forecast points with similar geographical and infrastructure characteristics. This facilitates the analysis of forecast statistics at the cluster level, which is found to improve statistical assessment of model performance since verification can be achieved at a much higher resolution than the current methodology allows. Furthermore, verification of the full spatial extent of a route-based forecast can be achieved with fewer forecast points since the majority of thermal variations around the road network are well represented by the clustering solutions. A new sampling strategy is proposed that potentially enables verification at the full spatial and temporal resolution. 相似文献
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M. J. Best 《Theoretical and Applied Climatology》2006,84(1-3):47-55
Summary The current resolution of operational weather forecast model is not sufficient in general to explicitly resolve even the major
cities of the World. As a consequence, urban areas have traditionally been neglected in such models. The introduction of tiled
land surface models has enabled sub-gridscale landuse to be modelled, and hence has provided the opportunity to model cities
within weather forecast models. However, to date there has been little effort made within the operational weather forecast
community.
At present there is only one operational centre that explicitly resolves urban areas. This centre includes a simple urban
scheme within its mesoscale and global models, which has been shown to have a positive impact on the forecast. However, with
the recent developments within urban meteorology there are now a variety of urban schemes, which vary in their complexity
and parameter requirements, that would be suitable for operational weather forecast models. So it is likely that more operational
models, and in particular mesoscale models, will include urban areas in the near future.
With the majority of the World‘s population living in cities, the resilience of these cities to the impacts of climate change
is also becoming of increasing interest. This means that urban areas will have to be included within climate change simulations,
as well as weather forecast simulations, in the future. At present, only one climate change model has included a parametrisation
for urban areas. However, this is likely to increase if work in this area grows rapidly. 相似文献
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Luis Ricardo Lage Rodrigues Francisco Javier Doblas-Reyes Caio Augusto dos Santos Coelho 《Climate Dynamics》2014,42(3-4):597-616
Different combination methods based on multiple linear regression are explored to identify the conditions that lead to an improvement of seasonal forecast quality when individual operational dynamical systems and a statistical–empirical system are combined. A calibration of the post-processed output is included. The combination methods have been used to merge the ECMWF System 4, the NCEP CFSv2, the Météo-France System 3, and a simple statistical model based on SST lagged regression. The forecast quality was assessed from a deterministic and probabilistic point of view. SSTs averaged over three different tropical regions have been considered: the Niño3.4, the Subtropical Northern Atlantic and Western Tropical Indian SST indices. The forecast quality of these combinations is compared to the forecast quality of a simple multi-model (SMM) where all single models are equally weighted. The results show a large range of behaviours depending on the start date, target month and the index considered. Outperforming the SMM predictions is a difficult task for linear combination methods with the samples currently available in an operational context. The difficulty in the robust estimation of the weights due to the small samples available is one of the reasons that limit the potential benefit of the combination methods that assign unequal weights. However, these combination methods showed the capability to improve the forecast reliability and accuracy in a large proportion of cases. For example, the Forecast Assimilation method proved to be competitive against the SMM while the other combination methods outperformed the SMM when only a small number of forecast systems have skill. Therefore, the weighting does not outperform the SMM when the SMM is very skilful, but it reduces the risk of low skill situations that are found when several single forecast systems have a low skill. 相似文献
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Weather forecasts by any forecast system are verified using either distributions-oriented or measures-oriented forecast verification measures. Both the forecast verification schemes represent different aspects of the forecast quality, and advantages of them can be utilized to get better insight and to identify particular strengths (deficiencies) in the forecast performance of any forecast system. Keeping this in view, multi-faced verification (binary and continuous) of quantitative precipitation forecasts for consecutive 3 days by a Regional Meso-scale Weather Simulation Model (MM5 Model) has been carried out to get complete insight into its performance. The MM5 model forecasts at 10-km resolution for 792 days of six winters (winter 2003/2004 to winter 2008/2009) are compared with the observational data of six stations in the complex topography of Northwest Himalaya (NWH) in India. The model forecasts are verified using binary categorical forecast verification measures such as Probability of Detection, False Alarm Rate, Miss Rate, Correct Non-occurrence, Critical Success Index and Percent correct, and continuous forecast verification measures such as Mean Absolute Error (MAE) and Root Mean Square Error (RMSE). BIAS is computed to know over-forecast/under-forecast tendency of a precipitation day (PT day) by the MM5 model. MAE (RMSE) of the MM5 model is computed separately for all days, PT days and no precipitation days (NPT days). MAE (RMSE) of PT days is found to be relatively larger as compared to NPT days and all days. These findings indicate that MAE (RMSE) computed separately for all days, PT days and NPT days provides better insight into the performance of the MM5 model. Results also suggest that the MM5 model shows reasonably good performance for binary forecasts (PT days/NPT days) for day 1 (0–24 h), day 2 (24–48 h) and day 3 (48–72 h). However, large errors are seen in predicting the observed precipitation amount of PT days over NWH. 相似文献
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对21世纪以来定量降水预报技术流程中的数值模式预报、统计后处理、检验评估和预报员作用4个方面的研究工作进行了归纳,主要进展包括:业务全球模式对于降水的预报能力持续提升,而发展高分辨率模式 (尤其是对流尺度模式) 和集合预报是提高定量降水预报精准化水平的主要途径,且将两者相结合以促进短期降水预报是发展趋势;统计后处理技术已发展到应用数据挖掘方法对海量预报数据中有效信息进行提取和集成,而再预报资料的出现将进一步促进统计后处理技术的发展;为解决评估精细化定量降水预报面临的新问题,多种新的检验技术得到发展和应用,如极端降水检验评分、空间检验技术及概率检验方法等;预报员在模式和后处理方法上能够提供的附加值越来越有限,但在预报流程中仍将处于核心地位,其角色将逐渐向帮助用户进行决策方向转变。文章指出,定量降水预报技术的发展所面临的挑战包括大气水汽观测及同化技术改进、暖区和复杂地形下暴雨预报等科学问题的解决。 相似文献
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对我国华东、华南、华北区域气象中心和中国气象局数值预报中心业务运行的区域模式2011年5—9月的6 h降水预报, 采用不同检验结果平均方案进行对比检验。对比结果表明:不同的检验结果平均方案基本不影响与中国气象局数值预报中心模式 (NMC-GRA) 在相同区域关于TS评分比较的相对检验结论,即当两个模式评分差距较大时,评分高的模式在两个方案中是一样的,但评分比较接近时,若有一个模式对该区大尺度降水预报较好时,则可能在新方案中有较高的TS评分,而此模式原方案评分则可能略低于局地小尺度降水预报较好的模式。但对于较少发生的强降水预报的预报偏差的评价有很大不同,当新方案的结果显示多数模式对强降水的预报偏少,原方案则可能显示偏多,说明模式对大尺度的强降水预报较实况偏少,但对小尺度局地降水的预报则可能偏多。 相似文献
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Summary The National Hurricane Center and Joint Typhoon Warning Center operational tropical cyclone intensity forecasts for the three
major northern hemisphere tropical cyclone basins (Atlantic, eastern North Pacific, and western North Pacific) for the past
two decades are examined for long-term trends. Results show that there has been some marginal improvement in the mean absolute
error at 24 and 48 h for the Atlantic and at 72 h for the east and west Pacific. A new metric that measures the percent variance
of the observed intensity changes that is reduced by the forecast (variance reduction, VR) is defined to help account for
inter-annual variability in forecast difficulty. Results show that there have been significant improvements in the VR of the
official forecasts in the Atlantic, and some marginal improvement in the other two basins. The VR of the intensity guidance
models was also examined. The improvement in the VR is due to the implementation of advanced statistical intensity prediction
models and the operational version of the GFDL hurricane model in the mid-1990s. The skill of the operational intensity forecasts
for the 5-year period ending in 2005 was determined by comparing the errors to those from simple statistical models with input
from climatology and persistence. The intensity forecasts had significant skill out to 96 h in the Atlantic and out to 72 h
in the east and west Pacific. The intensity forecasts are also compared to the operational track forecasts. The skill was
comparable at 12 h, but the track forecasts were 2 to 5 times more skillful by 72 h. The track and intensity forecast error
trends for the two-decade period were also compared. Results showed that the percentage track forecast improvement was almost
an order of magnitude larger than that for intensity, indicating that intensity forecasting still has much room for improvement. 相似文献
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利用耦合有起电和放电物理过程的中尺度起电放电模式WRF-Electric,开展了华北地区连续3年（2015—2017年）的闪电活动预报试验。结合全国地闪定位观测资料,针对不同影响范围雷暴类型和预报时间,对数值预报结果开展点对点的定量检验,评估模式对闪电活动的预报能力及特点。结果表明:WRF-Electric中尺度模式具备一定的区域闪电活动预报能力,在起报后的6~12 h对闪电活动区域具有较好的预报效果。雷暴落区预报的点对点定量检验中,模式和业务预报在华北主汛期（6—8月）的预报临界成功指数（CSI）均为0.1,模式对于活动范围较小的局地性雷暴过程的预报更具参考价值。模式预报的闪电活动范围相对集中,闪电活动密度偏高,预报的主要问题存在于放电参数化方案的设计。应当考虑到模式空间分辨率对云内电场强度的影响,合理降低闪电参数化中的放电阈值以扩大预报的闪电活动范围。模式在闪电密度的定量预报上还有较大改进空间,单次放电中和电荷量应当更符合观测事实。 相似文献
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基于延伸期过程性天气气候事件预报评估的特点,结合实际科研和业务工作的需求,提出了一种适用于延伸期过程预报的检验方法 (简称PPS方法)。该方法参考了常用的预报评分方法准则,借鉴了命中率、假警报率、欧式距离和动态时间弯曲距离等评估检验方法。利用命中率、假警报率和该方法对实际预报中可能出现的有漏报没有空报和既有漏报也有空报这两类情况的多个实例进行对比分析,表明该方法既能考虑大气随着时间的延长预报效果急剧降低的特性,也考虑了相似时间序列度量不精确匹配和形变的问题。利用该方法对1999—2010年冬季冷空气过程业务预报进行检验,结果表明:该方法能清晰表征延伸期预报时段内冷空气过程预报的准确程度,真实反映了目前延伸期预报准确率较低的现状,有较好的适用性。同时,该方法也适用于其他延伸期过程事件预报的评分,具有较好的应用前景。 相似文献
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GRAPES_TCM模式对影响浙江省热带气旋风力的预报评估 总被引：1，自引：1，他引：0
基于2006—2011年热带气旋影响时浙江省气象站实测风力和上海台风研究所GRAPES_TCM模式输出资料分析得出:模式地形高度与实际差异越大则直接输出风速平均误差越大,通过对浙江沿海模式地形高度误差绝对值在10 m以内的站点进行风力预报评估,结果发现:12~72 h模式直接输出风速存在一定的系统性误差。模式对浙江沿海站点风力预报的TS评分随风力等级的提高而降低,主要缘于空报率的增大。BS评分则表明,模式对越强的风力越有过度预报的倾向。模式20时预报的TS评分一般好于08时,主要得益于漏报率的降低。经MOS释用后可以在一定程度上提高站点风力预报与实况的正相关和预报稳定性,同时提高不同等级风力预报的TS评分;12、24 h模式站点,6级以上风力预报能力与主观预报相当。 相似文献
13.
Summary In this paper, an attempt is made to examine the influence of the physical forcings of an atmospheric general circulation model (AGCM) in the reduction of the systematic errors of the tropical forecasts. A number of major modifications in the parameterization of physical processes were carried out in the operational forecasting system of the European Centre for Medium Range Weather Forecasts (ECMWF) during the period 1984–88 largely in an attempt to reduce the conceptual weaknesses in their formulation. A large number of studies (Slingo et al., 1988; Tiedtke et al., 1988; etc) have demonstrated the positive impact on the reduction of tropical forecast errors to various changes in the treatment of physical processes in the ECMWF model.Keeping in view of these facts, the evaluation of the systematic errors of the ECMWF tropical forecasts is carried out for a period prior to the incorporation of major modifications in the parameterization of physical processes (1984) and corresponding period after such major changes are implemented in the operational AGCM of ECMWF (1988). The paper describes a detailed comparison of the tropical forecast errors for summer monsoon seasons (June-August [JJA]) of 1984 and 1988 in order to bring out the impact on tropical simulation of various improvements in the treatment of physical processes.The results demonstrate a dramatic reduction in the systematic errors of the tropical circulation together with an enhancement of the hydrological cycle to a realistic climatological level with the incorporation of major changes in the treatment of physical processes. Similar improvements are also observed in the winter simulation. In spite of major improvements in the simulation of tropical circulation, the nature of the tropical systematic errors of the ECMWF AGCM, however, remains unchanged. Thus, the inference of the study indicates the requirement of a new approach to the problem of parameterization of physical processes particularly, convection, radiation, boundary layer and their interactions for further reduction of the tropical forecast errors.With 14 Figures 相似文献
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应用国家气象中心模式检验方法,对华中区域中尺度业务数值预报模式WRF和中国气象局下发的GRAPES模式2013年1-12月的预报产品（包括降水、2 m温度场、850 hPa温度场、850 hPa风场和500 hPa位势高度场预报）进行统计检验。检验结果表明：所有要素24 h预报均优于48 h;对于晴雨预报,GRAPES模式TS评分高于WRF,但随着降水量级增大,WRF的TS评分基本都高于GRAPES,同时WRF降水预报范围明显偏大;分析2 m温度场的均方根误差及预报准确率发现,WRF的2 m温度场预报优于GRAPES,且暖季预报优于冷季;形势场要素分析表明,WRF对850 hPa温度场和风场预报具有相当大的优势,全年误差变化较稳定,而对500 hPa位势高度场的预报误差存在一定的季节性特征,即夏半年WRF高度场预报优于冬半年,GRAPES模式则相反。总体上,华中区域中尺度业务数值模式产品对天气预报具有一定的参考价值。 相似文献
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Diana J. M. Greenslade Eric W. Schulz Jeff D. Kepert Graham R. Warren 《Journal of Atmospheric & Ocean Science》2005,10(3):261-287
Recent work has demonstrated that surface marine winds from the Bureau of Meteorology's operational Numerical Weather Prediction (NWP) systems are typically underestimated by 5 to 10%. This is likely to cause significant bias in modelled wave fields that are forced by these winds. A simple statistical adjustment of the wind components is shown to reduce the observed bias in Significant Wave Height considerably. The impact of increasing the vertical resolution of the NWP model and assimilating scatterometer data into the model is assessed by comparing the resulting forecast wind and waves to observations. It is found that, in general, the inclusion of scatterometer observations improves the accuracy of the surface wind forecasts. However, most of the improvement is shown to arise from the increased number of vertical levels in the atmospheric model, rather than directly from the use of the observations. When the wave model is forced with surface winds from the NWP model that includes scatterometer data, it is found that the scatterometer assimilation does not reduce the systematic bias in surface wave forecasts, but that the random errors are reduced. 相似文献
16.
This study examines the forecast performance of tropical intraseasonal oscillation (ISO) in recent dynamical extended range
forecast (DERF) experiments conducted with the National Centers for Environmental Prediction (NCEP) Global Forecasting System
(GFS) model. The present study extends earlier work by comparing prediction skill of the northern winter ISO (Madden-Julian
Oscillation) between the current and earlier experiments. Prediction skill for the northern summer ISO is also investigated.
Since the boreal summer ISO exhibits northward propagation as well as eastward propagation along the equator, forecast skill
for both components is computed. For the 5-year period from 1 January, 1998 through 31 December, 2002, 30-day forecasts were
made once a day. Compared to the previous DERF experiment, the current model has shown some improvements in forecasting the
ISO during winter season so that the skillful forecasts (anomaly correlation>0.6) for upper-level zonal wind anomaly extend
from the previous shorter-than 5 days out to 7 days lead-time. A similar level of skill is seen for both northward and eastward
propagation components during the summer season as in the winter case. Results also show that forecasts from extreme initial
states are more skillful than those from null phases for both seasons, extending the skillful range by 3–6 days. For strong
ISO convection phases, the GFS model performs better during the summer season than during the winter season. In summer forecasts,
large-scale circulation and convection anomalies exhibit northward propagation during the peak phase. In contrast, the GFS
model still has difficulties in sustaining ISO variability during the northern winter as in the previous DERF run. That is,
the forecast does not maintain the observed eastward propagating signals associated with large-scale circulation; rather the
forecast anomalies appear to be stationary at their initial location and decay with time. The NCEP Coupled Forecast System
produces daily operational forecasts and its predication skill of the MJO will be reported in the future. 相似文献
17.
GRAPES-GFS模式暴雨预报天气学检验特征 总被引：5，自引：4，他引：1
本文采用天气学检验方法,对2016年度国家气象中心GRAPES全球数值预报系统(GRAPES-GFS)业务预报暴雨过程及2013-2015年部分回算个例进行了检验,并结合对比欧洲中期天气预报中心确定性预报模式(EC模式)和国家气象中心全球谱模式T639L60(T639模式)降水预报,梳理总结业务GRAPES-GFS模式预报性能优势和系统性偏差特征。被检验暴雨过程共38次,其中南方暴雨过程20次,北方暴雨过程6次,热带扰动或台风降水过程12次。依靠预报员主观天气学检验分析,从降水预报效果检验出发,结合主要影响天气系统和示踪物理量检验,梳理总结模式预报系统性偏差,以期全面发掘该业务预报模式性能。结果表明对短期时效内的降水预报,GRAPES-GFS模式预报稳定性较好,整体明显优于T639模式。但还存在诸如对对流性降水预报较实况偏北或对主雨带南侧暖区降水预报不足的偏差特征;另对弱高空波动背景下的对流性降水预报偏弱;而在降水预报强度大致正确的情况下,对降水系统南侧偏南气流控制区域预报湿度偏大,对副热带地区的低涡系统预报偏强。 相似文献
18.
On 21 July 2012, an extreme rainfall event that recorded a maximum rainfall amount over 24 hours of 460 mm, occurred in Beijing, China. Most operational models failed to predict such an extreme amount. In this study, a convective-permitting ensemble forecast system (CEFS), at 4-km grid spacing, covering the entire mainland of China, is applied to this extreme rainfall case. CEFS consists of 22 members and uses multiple physics parameterizations. For the event, the predicted maximum is 415 mm d-1 in the probability-matched ensemble mean. The predicted high-probability heavy rain region is located in southwest Beijing, as was observed. Ensemble-based verification scores are then investigated. For a small verification domain covering Beijing and its surrounding areas, the precipitation rank histogram of CEFS is much flatter than that of a reference global ensemble. CEFS has a lower (higher) Brier score and a higher resolution than the global ensemble for precipitation, indicating more reliable probabilistic forecasting by CEFS. Additionally, forecasts of different ensemble members are compared and discussed. Most of the extreme rainfall comes from convection in the warm sector east of an approaching cold front. A few members of CEFS successfully reproduce such precipitation, and orographic lift of highly moist low-level flows with a significantly southeasterly component is suggested to have played important roles in producing the initial convection. Comparisons between good and bad forecast members indicate a strong sensitivity of the extreme rainfall to the mesoscale environmental conditions, and, to less of an extent, the model physics. 相似文献
19.
对北京地区中尺度数值天气预报客观检验系统的框架和方法进行了详细的介绍，分析了北京地区冬季（2001年11月1日~2002年2月28日）主要预报要素的客观检验结果，在此基础上给出北京地区冬季中尺度数值预报业务的误差特征，并根据检验结果定性地分析了模式预报系统性和非系统性误差的可能来源。结果表明，模式地形的强迫作用是地面和对流层低层预报系统性误差的重要来源；测站高空预报要素的非系统性误差显著，初始时刻存在的误差在积分过程中被进一步放大；对北京 (54511) 单站地面要素预报的检验结果发现，2-m温度预报冬季整体偏低。在系统性误差为主要误差分量时对模式的平均误差进行订正能有效地提高温度预报的准确率。 相似文献
20.
Summary The University of New South Wales (UNSW) High Resolution numerical weather prediction model (HIRES) is run routinely, on
a daily basis, at a horizontal resolution of 25 km. The output is made available to the New South Wales (NSW) regional office
of the Australian Bureau of Meteorology in Sydney. HIRES has been used to forecast mean wind direction and speed at a height
of 12 metres for a number of events in the past. The opportunity was used in December 1997 to run the model for the annual
Sydney to Hobart yacht race area.
For the 1997 Sydney to Hobart yacht race the model was run at 25 km horizontal resolution and the output was made available
to all competitors on the morning of the race, namely December 26th. It was also decided by the authors to expand the verification
to include all observations available both from land and sea within the model domain an well as those available from a moving
single point at sea, namely a yacht.
After the event, the model was run once at the increased resolution of 10 km, out to 5 days ahead. Both model runs were subjected
to detailed verification by one of the authors (KLB) who participated in the race aboard the maxi-yacht Nicorette and who carried out a pre-arranged observational program during the race. Surface synoptic weather maps prepared in the NSW
office of the Bureau of Meteorology were also consulted in order to extend the verification scheme. The model predicted winds
were verified on a six-hourly basis utilising instrumentation on the yacht as well as surface observations plotted in standard
World Meterological Organisation (WMO) format on surface synoptic weather maps. The yacht carried wind sensors situated on
top of the mast at a height of 30 metres above the water. The authors were most interested in the accuracy of the wind velocity
forecast by the model.
It is important to note that forecasting for points over the ocean at widely separated time intervals represents a very difficult
challenge. The verifications reveal that the model gave overall forecast guidance of very good to excellent quality and was
particularly accurate early in the race, when a Southerly Buster event occurred during the evening of the first day. However,
a caveat should be added that this forecast, despite its remarkable accuracy, is not a claim that accurate very high resolution
regional prediction is a solved problem. Rather, it is a demonstration that in particular instances current models are now
capable of achieving high levels of skill a number of days ahead.
Received September 28, 1999 Revised November 25, 1999 相似文献