Temporal features in thunder days in the United States

1901–80 data for the contiguous U.S. show that secular variability of thunder days was very much less than that of precipitation or of frequency of extra tropical cyclones. Overall, there may have been a slight decline, but more evident was an increase to the thirties followed by a falling off, broken only by a peak in the seventies. These up-and-down movements were evident in most months of the year and regions of the U.S. The general decrease, however, was clear only in the South East and replaced by an increase in the Upper Great Lakes region. Secular variation in thunder day frequency was slightly correlated positively with that of extra tropical cyclone frequency and negatively with sea level pressure. The analysis also confirmed well known seasonal and regional patterns of thunder activity.     

美国天气预报技术的发展

介绍了美国天气预报技术的发展现状。指出在大气探测技术、数值预报及可视化技术发展的推动下美国传统的天气预报向定量与定时方向发展。定量降水预报的实现是天气预报由定性走向定量的重要标志。在充分利用数值模式产品的基础上综合应用卫星与雷达资料建立客观预报工具在暴雨和强对流天气预报中取得较好效果;中尺度分析业务系统的不断改进使降水预报的技巧有明显提高。作者还介绍了美国数值预报产品释用及预报业务系统的概况。最后     

The 1886 tornado of Madrid

Considering the number of dead people, the worst tornado in the last two centuries in Spain is presented. The words used to describe the phenomenon have hidden it to the general public and the specialist The coetaneous press and other printed sources have been revised, and this has let us know the true sense of those words as well as the sequence of the tornadic event.The synoptic situation that was presented by some European Meteorological Offices in 1886 has been revised when all available data and some indirect information have been included.Tornado track and force have been plotted on the actual map of the city following the available information in the newspapers and other documents. Other subjective comments made by the paper writers have allowed us to find out some psychological and sociological aspects used to enhance the tragic perception of their readers.     

Rainfall patterns in the eastern United States

This investigation is an extension of earlier work on rainfall patterns in the western United States. In the present study, rainfall figures from World Weather Records for cities east of the Mississippi have been subjected to filter analysis using the four filters described in the earlier investigation.The results suggest substantial coherence of rainfall data in a broad central area of North America, from the Great Lakes to the Rockies and into southern parts of the Canadian Prairies and Ontario. In this entire region there appears to be a pronounced rainfall cycle, of about 22 yr, which exhibits a possible relationship with the double sunspot cycle. However, inland from the U.S. north-east coast and including southern Quebec and the Canadian maritime Provinces, the cycle is different and is closer to 16 yr.Although the earlier investigation pointed to a connection between the lunar cycle of 18.6 yr and rainfall behaviour in the far west of the United States, there is little evidence of a similar connection in the east.     

The chemical composition of fogs and intercepted clouds in the United States

Over the past decade, the chemical compositions of fogs and intercepted clouds have been investigated at more than a dozen locations across the United States. Sampling sites have been located in the northeast, southeast, Rocky Mountain, and west coast regions of the US. They include both pristine and heavily polluted locations. Frontal/orographic clouds (warm and supercooled), intercepted coastal stratiform clouds, and radiation fogs have all been examined. Sample pH values range from below 3 to above 7. Major ions also exhibit a wide concentration range, with clouds at some locations exhibiting high sea salt concentrations, while composition at other locations is dominated by ammonium and sulfate or nitrate.     

美国西部的长期干旱变化

一些水文气候资料分析表明,美国西部正在经历着多年的严重干旱。然而,利用重建的覆盖美国西部大部分地区的过去1200年的网格化干旱资料进行分析,看出与更早时期出现的极端干旱和发生在公元800～1300年间(中世纪暖期(MWP))的大范围严重干旱相比,现在正经历的干旱还不算很严重。如果美国西部干旱程度的加强是一种对气候变暖的自然响应,那么任何将来温度增暖的趋势都将会加剧美国西部地区的长期干旱。     

美国全球变化研究现状

美国的全球变化研究主要由美国全球变化研究计划（ＵＳＧＣＲＰ）支持,重点资助季节—年际尺度气候变率,十年—百年尺度的气候变化,臭氧、ＵＶ辐射以及大气化学的变化,土地利用以及陆地、海洋生态系统的变化等４个领域。当前,水汽与云仍是全球变化研究中不确定性较大的一个方面,因而受到关注。关于气候变化的信号检测以及成因分析也是一个研究热点。气候模拟研究是全球变化研究的一个主要方法。卫星资料在全球变化研究中的应用取得了大量成果。近期美国在全球变化研究领域的重点是气候模拟,短期气候预测,十年—百年尺度的气候变化,臭氧、ＵＶ辐射以及大气化学的变化,地表以及陆地、海洋生态系统变化,对全球变化的区域尺度估计,卫星资料的应用,气候变化影响的国家级评估等８个方面。     

Long-Term Fluctuations in Thunderstorm Activity in the United States

Thunder-day occurrences during a 100-year period based on data from carefully screened records of 86 first-order stations distributed across the United States were assessed for temporal fluctuations and trends during 1896–1995. Short-term (<10-year) fluctuations of adjacentstations were often dissimilar reflecting localized differences in storm activity in a few years, making spatial interpretations difficult. But, temporal fluctuations based on 20-year and longer periods exhibited regional coherence reflecting the control of large, synoptic-scale weather systems on the distribution of thunderstorms over broad areas. Classification of station fluctuations based on 20-year periods revealed six types of distributions existed and they formed 12 discrete areas across the nation. One type present in the lower Midwest and the South had a peak in storm activity in 1916–1935 followed by a general decline to 1976–1995.A second type maximizing at the same time had its minimum earlier, in 1956–1975. Another distribution found at stations in the upper Midwest and Northeast had a mid-century peak (1936–1955) with a recent minimum in1976–1995. A fourth distribution also peaked in 1936–1955 but had an early minimumin 1896–1915, and it mainly occurred in the northern plains and Rocky Mountains. A fifth distribution peaked during 1956–1975 and was foundat stations in four areas including the central High Plains, Southwest, northern Great Lakes, and Southeast. The sixth temporal distribution showed a steady increase in storm activity during the 100-year period, peaking in 1976–1995, and covered a large area extending from the Pacific Northwestacross the central Rockies and into the southern High Plains. The national average distribution based on all station values peaked in mid century. The national distribution differs markedly from several regional distributions illustrating the importance of using regional analysis to assess temporal fluctuations in severe weather conditions in the nation. The 100-year linear trends of the 86 stations defined six regions across the U.S. Significant upward trends existed over most of the western two-thirds of the nation, unchanging trends existed in the northern plains and Midwest, and downward trends were found in most of the nation's east. The up trends in storm-day frequencies in the southern plains occurred where storm damage is greatest and where demographic changes have added to storm losses over time. The national patterns of trends and storm distributions were similar to those found for hail. The temporal distributions of storm activity helped explain recent increases in major storms and their losses, conditions which have increased in the west and south.     

The 20th century cooling trend over the southeastern United States

Portions of the southern and southeastern United States, primarily Mississippi, Alabama, and Georgia, have experienced century-long (1895–2007) downward air temperature trends that occur in all seasons. Superimposed on them are shifts in mean temperatures on decadal scales characterized by alternating warm (1930s–1940s, 1990s) and cold (1900s; 1960s–1970s) regimes. Regional atmospheric circulation and SST teleconnection indices, station-based cloud cover and soil moisture (Palmer drought severity index) data are used in stepwise multiple linear regression models. These models identify predictors linked to observed winter, summer, and annual Southeastern air temperature variability, the observed variance (r²) they explain, and the resulting prediction and residual time series. Long-term variations and trends in tropical Pacific sea temperatures, cloud cover, soil moisture and the North Atlantic and Arctic oscillations account for much of the air temperature downtrends. Soil moisture and cloud cover are the primary predictors of 59.6 % of the observed summer temperature variance. While the teleconnections, cloud cover and moisture data account for some of the annual and summer Southeastern cooling trend, large significant downward trending residuals remain in winter and summer. Comparison is made to the northeastern United States where large twentieth century upward air temperature trends are driven by cloud cover increases and Atlantic Multidecadal Oscillation (AMO) variability. Differences between the Northeastern warming and the Southeastern cooling trends in summer are attributable in part to the differing roles of cloud cover, soil moisture, the Arctic Oscillation and the AMO on air temperatures of the 2 regions.     

United States non-cooperation and the Paris agreement

In June 2017, the Trump administration decided to withdraw the US from the Paris Agreement, a landmark climate agreement adopted in 2015 by 195 nations. The exit of the US has not just raised concern that the US will miss its domestic emission reduction targets, but also that other parties to the Paris Agreement might backtrack on their initial pledges regarding emission reductions or financial contributions. Here we assess the magnitude of the threat that US non-cooperation poses to the Paris Agreement from an international relations perspective. We argue that US non-cooperation does not fundamentally alter US emissions, which are unlikely to rise even in the absence of new federal climate policies. Nor does it undermine nationally determined contributions under pledge and review, as the Paris Agreement has introduced a new logic of domestically driven climate policies and the cost of low-carbon technologies keeps falling. However, US non-participation in raising climate finance could raise high barriers to global climate cooperation in the future. Political strategies to mitigate these threats include direct engagement by climate leaders such as the European Union with key emerging economies, notably China and India, and domestic climate policies that furnish benefits to traditional opponents of ambitious climate policy.

Key policy insights

• US non-cooperation need not be a major threat to pledge and review under the Paris Agreement.

• US non-cooperation is a serious threat to climate finance.

• Deeper engagement with emerging economies offers new opportunities for global climate policy.

     

Advances in tornado and storm research in the United Kingdom and Europe: the role of the Tornado and Storm Research Organisation

The Tornado and Storm Research Organisation (TORRO) was formed in the UK in 1974 in order to determine realistic spatial, temporal and intensity distributions of tornadoes in the UK and, eventually, throughout Europe. Currently, TORRO's databases contain nearly 2000 tornadoes and over 550 waterspouts for the UK alone. In 1972, TORRO's founder, Terence Meaden, devised the Tornado Intensity Scale. This scale enables the wind speeds of tornadoes to be rated on a scale from T0 to T10, or more (since it is an open-ended scale). Using this scale, estimates have been made of the statistical return periods of differing intensities of UK tornadoes. TORRO's research into understanding the conditions of tornado development is ultimately intended to lead to issuing forecasts of tornadoes. In 1991, TORRO issued the first tornado watch in the UK for 12 November and this proved to be accurate—not only did three property-damaging tornadoes strike East Anglia but the forecast maximum intensity of T5 was attained. In 1975, TORRO expanded its activities to include conventional thunderstorm reporting and investigations. In 1982, TORRO incorporated the British and Irish thunderstorm data-collection organisation, the Thunderstorm Census Organisation (TCO), which was established in 1924. By the early 1980s, TORRO's network of voluntary thunderstorm observers, located throughout the UK and Ireland and increasingly in other European countries, numbered around 350 and the network continues to grow. In addition to TORRO's early focus on tornadoes and thunderstorms, its data collection and research has expanded to consider other whirlwinds (such as waterspouts and land devils), hailstorms, lightning (including ball lightning) and blizzards/heavy snowfalls. In 1996, TORRO began providing easy access to its databases (e.g. post-1995 UK and European severe weather events, especially tornadoes and hailstorms) and other information via its internet site at http://www.torro.org.uk/. Building on over 25 years of experience—and of the half a century of the TCO before it—TORRO continues to expand its European role in severe weather data collection and research, helped by the on-going appointment of European representatives and its increasing European membership.     

Uncertainties in projected runoff over the conterminous United States

Projections of runoff from global multi-model ensembles provide a valuable basis for the estimation of future hydrological extremes. However, projections suffer from uncertainty that originates from different error sources along the modeling chain. Hydrological impact studies have generally partitioned these error sources into global impact and global climate model (GIM and GCM, respectively) uncertainties, neglecting other sources, including scenarios and internal variability. Using a set of GIMs driven by GCMs under different representative concentration pathways (RCPs), this study aims to partition the uncertainty of future flows coming from GIMs, GCMs, RCPs, and internal variability over the CONterminous United States (CONUS). We focus on annual maximum, median, and minimum runoff, analyzed decadally over the twenty-first century. Results indicate that GCMs and GIMs are responsible for the largest fraction of uncertainty over most of the study area, followed by internal variability and to a smaller extent RCPs. To investigate the influence of the ensemble setup on uncertainty, in addition to the full ensemble, three ensemble configurations are studied using fewer GIMs (excluding least credible GIMs in runoff representation and GIMs accounting for vegetation and CO₂ dynamics), and excluding intermediate RCPs. Overall, the use of fewer GIMs has a minor impact on uncertainty for low and medium flows, but a substantial impact for high flows. Regardless of the number of pathways considered, RCPs always play a very small role, suggesting that improvement of GCMs and GIMs and more informed ensemble selections can yield a reduction of projected uncertainties.     

Spuriously induced temperature trends in the Southeast United States

Summary This study uses correlation and multiple regression techniques to document differences in annual temperature trends between the National Climatic Data Center (NCDC) Climate Division Database (CDD) and the United States Historical Climate Network (USHCN) for the Southeast United States. Results indicate that an increase (decrease) in elevation and a northward (southward) shift in mean station location in the CDD correspond with decreases (increases) in temperature. Although the movement of station locations in the CDD showed only modest impacts on trends, the effects of the movements are statistically significant, and explain some of the variances in the temperature trends. Results therefore suggest that climate divisions with more rugged terrain and greater shifts in elevation are more susceptible to spuriously generated trends.     

Spuriously induced precipitation trends in the southeast United States

This study uses correlation and multiple regression techniques to document differences in annual and seasonal precipitation trends between the NCDC Climate Division database and the United States Historical Climate Network (USHCN) in the southeast United States. Findings indicate that the majority of climate divisions have different temporal patterns than those depicted by the USHCN. They did not, however, consistently possess statistically significant relationships between the ratio (CDD/USHCN) and changes in mean station location as noted in other studies. It appears that other influences cause the majority of the variance between the two datasets. The fact that the two datasets do not consistently agree, however, suggests that spuriously induced trends may be present in the NCDC Climate Division database.     

Climate Change and Floodplain Management in the United States

Federal agencies use flood frequency estimates to delineate flood risk, manage the National Flood Insurance Program, and ensure that Federal programs are economically efficient. The assumption behind traditional flood risk analysis is that climate is stationary, but anthropogenic climate change and better knowledge of interdecadal climate variability challenge the validity of the assumption. This paper reviews several alternative statistical models for flood risk estimation that do not assume climate stationarity. Some models require subjective judgement or presuppose an understanding of the causes of the underlying non-stationarity, which is problematic given our current knowledge of the interaction of climate and floods. Although currently out of favor, hydrometeorological models have been used for engineering design as alternatives to statistical models and could be adapted to different climate conditions. Floodplain managers should recognize the potentially greater uncertainty in flood risk estimation due to climate change and variability and try to incorporate the uncertainties into floodplain management decision-making and regulation.     

The economic cost of greenhouse-induced sea-level rise for developed property in the United States

Estimates of the true economic cost that might be attributed to greenhouse-induced sea-level rise on the developed coastline of the United States are offered for the range of trajectories that is now thought to be most likely. Along a 50-cm sea level rise trajectory (through 2100), for example, transient costs in 2065 (a year frequently anticipated for doubling of greenhouse-gas concentrations) are estimated to be roughly $70 million (undiscounted, but measured in constant 1990$). More generally and carefully cast in the appropriate context of protection decisions for developed property, the results reported here are nearly an order of magnitude lower than estimates published prior to 1994. They are based upon a calculus that reflects rising values for coastal property as the future unfolds, but also includes the cost-reducing potential of natural, market-based adaptation in anticipation of the threat of rising seas and/or the efficiency of discrete decisions to protect or not to protect small tracts of property that will be made when necessary and on the (then current) basis of their individual economic merit.This research was funded by the Electric Power Research Institute as part of its impacts assessment program. Notwithstanding that support, the opinions expressed here and responsibility for any errors reside with the authors. The authors express their appreciation for comments offered on earlier drafts by Rick Freeman, Rob Mendelsohn, Joel Smith, Tom Wilson, Jim Titus, Robert Chen and the Snowmass Workshop on the Impacts of Global Change. If we may, we would also like to dedicate this paper to the memory of Dr. James Broadus from the Woods Hole Oceanographic Institution. His untimely death was, indeed, tragic; and we miss both his company and his flawless contribution to this and other work.     

Interannual temperature variability in the United States since 1896

The variability of mean monthly temperatures in the United States since 1896 is examined. The results show that the interannual variability reached a peak in the decade centered on 1930 and decreased fairly steadily to a minimum in the decade centered on 1970. This temporal trend is almost completely explained by changes in the variability of winter (December, January, February) mean monthly temperatures. The greatest percent decrease in variability occurred in the Midwest.     

Aerosol radiative properties in the semiarid Western United States

Characterization of aerosol optical properties, such as aerosol optical depth, Angstrom exponent, and volume size distribution at the semiarid site of Tombstone Arizona (31°23′N, 110°05′W, 1408 m) will be presented for one annual cycle. In this region, extensive observations of selected optical parameters such as aerosol optical depth (AOD) have been made in the past and reported on in the literature. Less is known about other optical characteristics that are important in climate modeling and remote sensing. New observational techniques and inversion methods allow for the expansion of the earlier information. Observations have been taken with a state of the art sun photometer for a 1-year period and their analysis will be presented here. Monthly mean AODs at 500 nm were found to be in the range of 0.03–0.12; the monthly mean Angstrom exponent ranged from 0.9 to 1.6, being higher in spring and summer and lower in late fall and winter. Volume size distributions exhibit clear dominance of smaller particles, with a gradual increase in size from winter to spring and into summer. Annual variation of the radii of the smaller and the larger particles ranged between 0.05–0.4 and 4–8 μm, respectively. Radiance measurements at 940 nm were used to estimate precipitable water. The retrieved values compared within limits of uncertainty with independently derived estimates from the National Center for Environmental Prediction (NCEP) regional weather forecast model. An interesting outcome from this study was the consistency found in aerosol optical depths as observed in this study and those derived about two decades ago.