Modelling the spatial and temporal distribution of rainfall intensity at local scale

Summary Accurate estimates of rainfall intensity distribution with high temporal and spatial resolution are necessary in most urban hydrological studies, such as planning, simulation or control of sewer networks. Traditionally, these data are obtained from intensity-duration-frequency (IDF) curves at sites with long rainfall intensity time-series, however, little attention is given to the spatial features of precipitation. In this paper, a mathematical model of a local scale storm that takes account of the spatial variability of rainfall and rain-cell movement is proposed. The model has been calibrated with a dense network of raingauges and a long rainfall intensity timeseries (60 years) and its parameters have been calculated for convective storms of return periods up to 15 years with their most frequently-observed rain-cell velocities (1 to 4 m/s).This work has been supported by the DGICYT, Project NAT91-0596.With 6 Figures     

Tropical and extratropical cyclone damages under climate change

This paper provides the first quantitative synthesis of the rapidly growing literature on future tropical and extratropical cyclone damages under climate change. We estimate a probability distribution for the predicted impact of changes in global surface air temperatures on future storm damages, using an ensemble of 478 estimates of the temperature-damage relationship from nineteen studies. Our analysis produces three main empirical results. First, we find strong but not conclusive support for the hypothesis that climate change will cause damages from tropical cyclones and wind storms to increase, with most models predicting higher future storm damages due to climate change. Second, there is substantial variation in projected changes in losses across regions. Potential changes in damages are greatest in the North Atlantic basin, where the multi-model average predicts that a 2.5 °C increase in global surface air temperature would cause hurricane damages to increase by 63 %. The ensemble predictions for Western North Pacific tropical cyclones and European wind storms (extratropical cyclones) are +28 % and +23 %, respectively. Finally, our analysis shows that existing models of storm damages under climate change generate a wide range of predictions, ranging from moderate decreases to very large increases in losses.     

Understanding the impact of climate change on Northern Hemisphere extra-tropical cyclones

Extra-tropical cyclones strongly influence weather and climate in mid-latitudes and any future changes may have large impacts on the local scale. In this study Northern Hemisphere storms are analysed in ensembles of time-slice experiments carried out with an atmosphere only model with present day and future anthropogenic emissions. The present day experiment is forced by observed sea-surface temperature and sea-ice. The sea-surface temperatures and sea-ice for the future experiment are derived by adding anomalies, from parallel but lower resolution coupled model experiments, to the observed data. The storms in the present day simulation compare fairly well with observations in all seasons but some errors remain. In the future simulations there is some evidence of a poleward shift in the storm tracks in some seasons and regions. There are fewer cyclones in the Northern Hemisphere in winter and spring. The northeast end of the North Atlantic storm track is shifted south in winter giving more storms and increased frequency of strong winds over the British Isles. This shift is related to an increase in baroclinicity and a southward shift of the jet that occurs as a response to a minimum in ocean warming in the central North Atlantic. An increase in the frequency of storms over the UK is likely to cause enhanced levels of wind and flood damage. These results concur with those from some other models, however, large uncertainties remain.     

广东台风特大暴雨预报

使用台风年鉴，天气图，天星云图等气象资料，对１９６０－１９９１年影响广东的３９例特大暴雨台风进行了对比分析，台风特大暴雨主要是由其云系中的中尺度强降水系统造成，归纳出形成发展的概仿模式和相应环境流场特征，建立预报思路与方法。１９９４年作１５次预报试验，其准确率达７３％。     

长沙黄花机场两次对流风暴特征的对比分析

利用新一代多普勒天气雷达资料、机场自动观测系统资料结合其它有关资料,对2012年9月1日和2013年7月1日发生在长沙黄花机场的两次对流风暴的特征进行了对比分析,结果表明：2012年9月1日的对流风暴属于普通单体风暴,具有尺度小、持续时间短、降水量大的特点;2013年7月1日的对流风暴属于多单体风暴,具有尺度较小、生命史较短,产生了雷暴、降水量小的特点。两次对流风暴的共同点：在很短时间内产生了大于20 m/s的地面大风（〉17 m/s）,出现了风向突变、风速骤增、气压上升、气温骤降等类似于飑线的气象要素剧烈变化过程;两次对流风暴的触发机制都是副高外围的东风波扰动。     

Catastrophic winter storms: An escalating problem

Winter storms are a major weather problem in the USA and their losses have been rapidly increasing. A total of 202 catastrophic winter storms, each causing more than $1 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous USA, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of 9 storms, and 1 year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing synoptic weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.     

Projected implications of climate change for road safety in Greater Vancouver, Canada

The elevated risk of collision while driving during precipitation has been well documented by the road safety community, with heavy rainfall events of particular concern. As the climate warms in the coming century, altered precipitation patterns are likely. The current study builds on the extensive literature on weather-related driving risks and draws on the climate change impact literature in order to explore the implications of climate change for road safety. It presents both an approach for conducting such analyses, as well as empirical estimates of the direction and magnitude of change in road safety for the highly urbanized Greater Vancouver metropolitan region on Canada’s west coast. The signal that emerges from the analysis is that projections of greater rainfall frequency are expected to translate into higher collision counts by the mid 2050s. The greatest adverse safety impact is likely to be concentrated on moderate to heavy rainfall days (≥ 10 mm), which are associated with more highly elevated risks today. This suggests that particular attention should be paid to future changes in the frequency and intensity of extreme rainfall events.     

Increased hurricane intensities with CO2-induced warming as simulated using the GFDL hurricane prediction system

 The impact of CO₂-induced global warming on the intensities of strong hurricanes is investigated using the GFDL regional high-resolution hurricane prediction system. The large-scale initial conditions and boundary conditions for the regional model experiments, including SSTs, are derived from control and transient CO₂ increase experiments with the GFDL R30-resolution global coupled climate model. In a case study approach, 51 northwest Pacific storm cases derived from the global model under present-day climate conditions are simulated with the regional model, along with 51 storm cases for high CO₂ conditions. For each case, the regional model is integrated forward for five days without ocean coupling. The high CO₂ storms, with SSTs warmer by about 2.2 °C on average and higher environmental convective available potential energy (CAPE), are more intense than the control storms by about 3–7 m/s (5%–11%) for surface wind speed and 7 to 24 hPa for central surface pressure. The simulated intensity increases are statistically significant according to most of the statistical tests conducted and are robust to changes in storm initialization methods. Near-storm precipitation is 28% greater in the high CO₂ sample. In terms of storm tracks, the high CO₂ sample is quite similar to the control. The mean radius of hurricane force winds is 2 to 3% greater for the composite high CO₂ storm than for the control, and the high CO₂ storms penetrate slightly higher into the upper troposphere. More idealized experiments were also performed in which an initial storm disturbance was embedded in highly simplified flow fields using time mean temperature and moisture conditions from the global climate model. These idealized experiments support the case study results and suggest that, in terms of thermodynamic influences, the results for the NW Pacific basin are qualitatively applicable to other tropical storm basins. Received: 20 July 1998/Accepted: 24 December 1998     

Quasi-stationarity of centennial Northern Hemisphere midlatitude winter storm tracks

The winter storm activity on the Northern Hemisphere during the last one thousand years in a global climate simulation was analyzed by determining all midlatitude storms and their tracks, then consecutively clustering them for hundred years’ segments. Storm track clusters with longest lifetime and largest deepening rates are found over the oceans. The numbers of extratropical winter storms exhibit notable yearly variability but hardly any variability on centennial time scales. The clusters of these storm tracks also show only small differences between the centuries. The numbers of members in neighboring oceanic clusters are negatively correlated. A linear relationship was found between the numbers of members per storm track clusters over the Pacific or Atlantic Ocean and seasonal mean atmospheric circulation patterns by a canonical correlation analysis.     

Increased probability of fire during late Holocene droughts in northern New England

A 101 year time-series of storm losses in the Netherlands is developed from the near-surface wind speed records at five Dutch stations. Station metadata combined with results from statistical tests were used to homogenise the data and retain the temporal variability driven solely by changes in climate processes. The wind speed data were transformed into storm damage using a model measuring loss impacts upon society. The resulting windstorm loss time-series for the Netherlands contains some interesting features. Annual losses are stable over the whole period and have a dominant cycle with a period of about 50 years. The Netherlands is currently experiencing the minimum aggregate storm damage of the past 100 years, though only slightly lower than a quiet period of 50 years ago. Both of these minima are driven primarily by lowered rates of occurrence of damaging storms. However, further analysis reveals the present-day minimum has different characteristics from the previous lull: currently, the frequency of stronger storms is slightly above the previous minimum whereas the frequency of weaker storms is uniquely low. A seasonal analysis provides more information: there is a dearth of damaging storms in the earlier half of the storm season in the present day; since this period contains generally weaker storms, this seasonality is also manifested as a lack of weaker storms. These results suggest a different mix of climate forcing mechanisms in modern times compared to 50 years ago, in the earlier half of the storm season.     

Renewable and low-carbon energies as mitigation options of climate change for China

This article discusses how renewable and low-carbon energies can serve as mitigation options of climate change in China’s power sector. Our study is based on scenarios developed in PowerPlan, a bottom-up model simulating a countries’ power sector and its emissions. We first adjusted the model to China’s present-day economy and power sector. We then developed different scenarios based on story lines for possible future developments in China. We simulated China’s carbon-based electricity production system of today and possible future transitions towards a low-carbon system relying on renewable and low-carbon energies. In our analysis, we compare the business-as-usual scenarios with more sustainable energy scenarios. We found that by increasing the share of renewable and nuclear energies to different levels, between 17% and 57% of all CO₂ emissions from the power sector could be avoided by 2030 compared to the business-as-usual scenario. We also found that electricity generation costs increase when more sustainable power plants are installed. As a conclusion, China has two options: choosing for high climate change mitigation and high costs or choosing for moderate climate change mitigation and moderate costs. In case high climate change mitigation will be chosen, development assistance is likely to be needed to cover the costs.     

甘肃沙尘暴短期、短时业务化预报方法研究

利用1955~2002年甘肃省80个站的观测资料，对发生在甘肃境内的64个强或特强沙尘暴个例逐个进行了天气气候分析，总结了甘肃沙尘暴天气气候特点，沙尘暴爆发的天气类型，移动路径。得出沙尘暴短期和临近预报的着眼点，建立了甘肃沙尘暴短期预报概念模型。通过用计算机语言和模块化设计方案，成功设计了中国西北地区沙尘暴监测预警人机交互预报平台，实现了沙尘暴监测预警预报业务化。     

天津春季沙尘天气日数变化规律及小波变换特征

根据沙尘天气标准确定了1961～2003年天津逐年的春季沙尘天气日数且形成序列，分析了春季沙尘天气的演变规律，并应用小波分析方法分析了其多时间尺度的变化特征。结果表明：天津地区春季的沙尘天气以每10年-5.9天的变化速率呈显著的下降趋势；20世纪60-70年代处于沙尘多发期，90年代最少；春季沙尘天气具有40年、4～6年和16年的明显周期。t检验结果显示，气候突变大约发生在1980年前后。     

Extremes of near-surface wind speed over Europe and their future changes as estimated from an ensemble of RCM simulations

In this study, we analyse the uncertainty of the effect of enhanced greenhouse gas conditions on windiness projected by an ensemble of regional model simulations driven by the same global control and climate change simulations. These global conditions, representative for 1961–1990 and 2071–2100, were prepared by the Hadley Centre based on the IPCC SRES/A2 scenario. The basic data sets consist of simulated daily maximum and daily mean wind speed fields (over land) from the PRUDENCE data archive at the Danish Meteorological Institute. The main focus is on the results from the standard 50 km-resolution runs of eight regional models. The best parameter for determining possible future changes in extreme wind speeds and possible change in the number of storm events is maximum daily wind speed. It turned out during this study that the method for calculating maximum daily wind speed differs among the regional models. A comparison of simulated winds with observations for the control period shows that models without gust parameterisation are not able to realistically capture high wind speeds. The two models with gust parametrization estimate an increase of up to 20% of the number of storm peak (defined as gusts?≥?8 Bft in this paper) events over Central Europe in the future. In order to use a larger ensemble of models than just the two with gust parameterisation, we also look at the 99th percentile of daily mean wind speed. We divide Europe into eight sub-regions (e.g., British Isles, Iberian Peninsula, NE Europe) and investigate the inter-monthly variation of wind over these regions as well as differences between today’s climate and a possible future climate. Results show differences and similarities between the sub-regions in magnitude, spread, and seasonal tendencies. The model ensemble indicates a possible increase in future mean daily wind speed during winter months, and a decrease during autumn in areas influenced by North Atlantic extra-tropical cyclones.     

Which downscaled rainfall data for climate change impact studies in urban areas? Review of current approaches and trends

Changes in extreme precipitation should be one of the primary impacts of climate change (CC) in urban areas. To assess these impacts, rainfall data from climate models are commonly used. The main goal of this paper is to report on the state of knowledge and recent works on the study of CC impacts with a focus on urban areas, in order to produce an integrated review of various approaches to which future studies can then be compared or constructed. Model output statistics (MOS) methods are increasingly used in the literature to study the impacts of CC in urban settings. A review of previous works highlights the non-stationarity nature of future climate data, underscoring the need to revise urban drainage system design criteria. A comparison of these studies is made difficult, however, by the numerous sources of uncertainty arising from a plethora of assumptions, scenarios, and modeling options. All the methods used do, however, predict increased extreme precipitation in the future, suggesting potential risks of combined sewer overflow frequencies, flooding, and back-up in existing sewer systems in urban areas. Future studies must quantify more accurately the different sources of uncertainty by improving downscaling and correction methods. New research is necessary to improve the data validation process, an aspect that is seldom reported in the literature. Finally, the potential application of non-stationarity conditions into generalized extreme value (GEV) distribution should be assessed more closely, which will require close collaboration between engineers, hydrologists, statisticians, and climatologists, thus contributing to the ongoing reflection on this issue of social concern.     

新疆南部干旱区暴雨研究：科学认知与主要进展*

新疆南部(简称南疆)是典型的干旱区,地形和下垫面复杂,生态环境脆弱,对气候变化异常敏感。在全球变暖背景下,近年来南疆暴雨发生频率和强度明显增加,引起社会广泛关注。本文主要回顾了南疆干旱区暴雨的科学认知、研究进程和最新研究进展,南疆暴雨具有降水集中度高、相对强度大、极端性强、空间分布不均匀等特点。南疆暴雨研究经过了从大降水个例到多尺度相互作用机理和数值模拟发展应用的阶段,目前在南疆暴雨的重要影响天气系统和水汽输送等方面取得新的科学认识。最后,对干旱区暴雨科学研究的未来发展方向进行了简要的讨论和展望,以期承上启下,为未来新时期南疆暴雨研究提供创新基础。     

Diagnostic analysis of future climate scenarios applied to urban flooding in the Chicago metropolitan area

Past heavy precipitation events in the Chicago metropolitan area have caused significant flood-related economic and environmental damages. A key component in flood management policies and actions is determining flood magnitudes for specified return periods. This is a particularly difficult task in areas with a complex and changing climate and land-use, such as the Chicago metropolitan area. The standard design storm methodology based on the NOAA Atlas 14 and ISWS Bulletin 70 has been used in the past to estimate flood hydrographs with variable return periods in this region. In a changing climate, however, these publications may not be accurate. This study presents and illustrates a methodology for diagnostic analysis of future climate scenarios in the framework of urban flooding, and assesses the corresponding uncertainties. First, the design storms are calculated using data downscaled by a regional climate model (RCM) at 30-km spacing for the present and 2050s under the IPCC A1Fi (high) and B1 (low) emissions scenarios. Next, the corresponding flood discharges at six watersheds in suburban Chicago are estimated using a hydrologic event model. The resulting scenarios in flood frequency were first assessed through a set of diagnostic tests for precipitation timing and frequency. The study did not reveal any significant changes in the 2050s in the average timing of heavy storms, but their regularity decreased. The average timing did not exhibit any significant spatial variability throughout the region. The precipitation frequency analysis revealed distinct differences between the northern and southeastern subregions of the Chicago metropolitan area. The quantiles in the northern subregion averaged for 2-year, 5-year, and 10-year return periods exhibited a 20% and 16% increase in daily precipitation for scenarios B1 and A1Fi, respectively. The southeastern subregion, however, exhibited a decrease of 12% for scenario B1 and a minor increase of 3% for scenario A1Fi. The hydrologic effects of changing precipitation on the flood quantiles were illustrated using six small watersheds in the region. The relative increases or decreases in precipitation translated into even larger relative increases or decreases in flood peaks, due to the nonlinear nature of the rainfall-runoff process. Simulations using multiple climate models, for longer periods, finer spatio-temporal resolution, and larger areal coverage could be used to more accurately account for numerous uncertainties in the precipitation and flood projections.     

1966—2016年重庆南川降水的多尺度分析

利用1966—2016年南川国家站的逐日降水观测资料,分析了南川降水的年内分布及次季节变化和暴雨的气候变化特征、年际、年代际和趋势变化特征。结果表明:南川降水的年内分布差异大,降水量峰值出现在6月,月降水强度最大在7月;南川的降水具有明显的次季节变化,且准双周变化信号(10~25 d)大于低频季节内振荡(25~90 d);南川的暴雨日数和暴雨量与年降水量有很好的正相关性;暴雨出现在3—11月,其分布呈单峰型,峰值出现在6月;年平均暴雨日为2.5 d,暴雨日数年际变化的线性趋势不显著;暴雨日总降水量在1966—1994年存在10~12 a的年代际变化信号,在1996—2016年主要存在13~15 a的年代际变化信号,在1976—1984年还存在2~4 a的年际变化信号;南川的暴雨特征量年际、年代际变化大,但没有显著的升降趋势,说明南川暴雨的总体气候特征是比较平稳的。     

Public perceptions of rainfall change in India

People’s perceptions of changes in local weather patterns are an important precursor to proactive adaptation to climate change. In this paper, we consider public perceptions of changes in average rainfall in India, analyzing the relationship between perceptions and the instrumental record. Using data from a national sample survey, we find that local instrumental records of precipitation are a strong predictor of perceived declines in rainfall. Perceptions of decreasing rainfall were also associated with perceptions of changes in extreme weather events, such as decreasing frequency of floods and severe storms, increasing frequency of droughts, and decreasing predictability of the monsoon. Higher social vulnerability—including low perceived adaptive capacity and greater food and livelihood dependence on local weather—was also associated with perceptions of decreasing rainfall. While both urban and rural respondents were likely to perceive local changes in precipitation, we show that rural respondents in general were more sensitive to actual changes in precipitation. Individual perceptions of changes in local climate may play an important role in shaping vulnerability to global climate change, adaptive behavior, and support for adaptation and mitigation policies. Awareness of local climate change is therefore particularly important in regions where much of the population is highly exposed and sensitive to the impacts of climate change.     

ROSE2.0在黔西南4·14强对流天气中的应用分析

受高空槽、切变线、静止锋、弱冷空气、西南急流、地面辐合线影响,2022年4月14日黔西南州出现大范围强对流天气。本文对过程中ROSE2.0进行应用检验分析,结论如下：（1）过程第一阶段对流强度偏弱;第二阶段超级单体或强多单体风暴发展和成熟,对流以大冰雹、8级雷暴大风、40 mm以下短时强降水为主;第三阶段列车效应最明显,风暴移速较快,对流以8～11级雷暴大风、中冰雹、40～60 mm短时强降水为主。（2）ROSE2.0与本地雷达软件相比,大冰雹时CR基本一致,但VIL、HI偏小,ET偏大;ROSE2.0与实际理论值相比,VIL值明显偏低,ET、HI偏大;雷暴大风时低层径向速度ROSE2.0比本地的要小,但中高层偏大;短时强降水时一小时雨强估计ROSE2.0比实际值偏小。