THE DIURANAL DISTRIBUTION OF LARGE HAIL OVER THE UNITED STATES

The diurnal course of large hail varies over the United States. The time of maximum of large hail changes from near 1500 hours on the east coast to between 1800 and 1900 hours on the Great Plains. The north-to-south differences are smaller except near the Gulf Coast, where secondary maxima occur. In some areas the time of maximum of large hail differs from the maxima times of tornadoes, heavy rain, and thunderstorms.     

ADJUSTMENTS TO NATURAL HAZARDS: FACTORS AFFECTING THE ADOPTION OF CROP-HAIL INSURANCE∗

As crop losses from hail continue to rise, farmers increasingly rely on crop-hail insurance to mitigate the effects of hail damage. This paper examines a series of socio-economic and psycho-dynamic factors that affect the adoption decision in a relatively homogeneous agricultural region in central Illinois. The very high rates of insurance adoption found in the area indicate that adoption is based on the perceived existence of a hazard, satisfaction with insurance and its availability at acceptable costs, and the perceived lack of alternative adjustments.     

SPATIAL AND TEMPORAL DISTRIBUTION OF INTENSE CONVECTIVE WEATHER — THUNDERSTORMS AND HAIL IN CHINA

Thunderstorms and hail are important features in the climatology of China. Using occurrences of thunderstorm days or hail days, the spatial and temporal distribution of these phenomena are described. Location, relief, thermal activity, and air mass convergence all contribute to seasonal variations and peak concentrations. The Qinghai-Tibet Plateau in summer is the most active thunderstorm area of the Northern Hemisphere at 30° to 35° of latitude, but extreme occurrence occurs in Yunnan Province, with thunderstorms experienced on more than 43% of days during the year.

Hailstorms in China usually pioduce small hail which causes minimal damage. Occurrences of squalls, however, may form extensive hailswaths accompanied by large hailstones. These long duration hailswaths are potentially very destructive. Middle and eastern areas of the Qinghai-Tibet Plateau may experience over 30 days a year on which hail occurs. The extreme occurrence of 53 hail days was recorded at Nagu. Although thunderstorm days tend to follow seasonal variation of winter and summer monsoon shifts, hail days correlate more to shifts in air mass convergence.     

长江口浑浊带含沙量的潮流变化及其成因分析

实测数据显示在长江口南槽浑浊带内,近河床含沙量在很多情况下在转流后1—3h内出现峰值,在涨、落急流速最大时含沙量却迅速下降。本文利用实测数据计算了不问潮时的泥沙垂向紊动扩散系数,发现它与底层含沙量有类似的变化过程,结合近底层高浓度悬沙的迁移,认为转流后出现的含沙量峰值主要是由于憩流期沉降到河床的悬沙重新悬浮引起的。重新悬浮是浑浊带的重要成因。     

三江源地区冰雹灾害分布特征及其成因

青藏高原腹地的雹灾形成与其它地区有一定的差别。根据三江源地区126个乡整理的近60 a的雹灾数据,分析了青海南部高原雹灾的空间和时间变化规律,并通过对雹灾次数与海拔高程、地形起伏度、居民点密度的相关分析,结果表明：三江源地区雹灾的高发区域为东北部的兴海、同德、贵南等地及南部的称多、玉树、囊谦等2个地区,雹灾主要发生在5～9月份,在6、8月份形成明显的双峰性特点,地形起伏度、居民点密度与雹灾频次具有明显的正相关,海拔高程与雹灾频次呈负相关,雨带推移和生产方式不同是三江源地区雹灾产生空间分异的主要原因。     

晋宁烟区冰雹灾害时空分布特征及环流形势分析

针对晋宁区2009~2018年6~9月5个乡镇烤烟种植区的冰雹灾害问题,以烟区冰雹灾害分布、烤烟种植及受损面积、经济损失等数据为基础,对烟区冰雹灾害时空分布特征、地形因素对冰雹灾害的影响等进行分析,并对冰雹灾害出现的大气环流背景进行分型。结果表明:晋宁烟区冰雹灾害年际变化大、时空分布极不均匀,7~8月最多,降雹时段主要集中在12~21时,高峰期16~18时;冰雹灾害多发区主要为晋城镇南部、双河乡和夕阳乡山区、二街西北部、六街东南部,且山区明显多于坝区;冰雹灾害风险从高到低依次为:晋城、夕阳、双河、二街、六街;冰雹灾害发生的环流形势主要有:低压活动型44.4%、低压槽型27.0%、低涡型4.8%、切变型3.2%,其他20.6%。     

AUTOMATED ISOCHRONES AND THE LOCATIONS OF EMERGENCY MEDICAL SERVICES IN CITIES

A method is described for the automatic calculation and graphical reproduction of isochrones around emergency medical centers in large cities. The isochrones are set for different time standards and for varying traffic conditions. The technique is based on the concept of a velocity field. It permits a rapid evaluation of coverage standards under different operating conditions.     

库尔勒市2015年两次冰雹天气成因及雷达回波特征对比分析

利用常规探测资料、库尔勒多普勒天气雷达、风云2E静止卫星以及NCEP/NCAR提供的0.5°×0.5°再分析资料,对2015年发生在库尔勒市的两次冰雹天气从天气形势、环境背景及强对流云团结构等方面进行了成因分析,并重点对比了雷达回波特征。结果表明：4月17日冰雹天气为弱短波槽影响,系统浅薄,6月1日为低涡降雹,系统深厚。两次冰雹共性特征很多：在冰雹发生前,有强的垂直风切变,0 ℃层和-20 ℃层高度适宜且之间伴有浅薄的饱和湿层。通过塔里木盆地东南缘水汽的输送,云团在天山南麓及切变线附近合并降雹是这两次冰雹最突出的特征。雷达图中冰雹云发展中强回波中心值＞55 dBz,配合有逆风区,存在明显的回波悬垂和弱回波区,强的垂直风切变是其发展和维持的主要原因。冰雹云形成于云顶亮温＜-50 ℃的冷云盖东南边缘的云团合并处附近,并且主要沿中低层平均风方向移动。     

CLIMATOLOGY: THE CHALLENGE FOR THE EIGHTIES

Geographical climatology must systematically investigate the exchanges of heat, water, and momentum that occur at or near the earth's surface. Our discipline should focus upon surface features described under the general term “topoclimatology”as well as upon transfer processes occurring in the planetary boundary layer. Climatologists must increase their understanding of the synergistic relationships among climatic processes, surface features, and human actions. Methods of data collection, summary, analysis, and display also need to be improved. These challenges must be met in order that we may develop a better understanding of climate and improve our quantitative climatic analogues.     

提高火箭防雹效果的几点建议

通过对各方面条件相似的滇中地区实施人工防雹作业后,烤烟受冰雹灾害的情况进行初步分析后认为,不论是使用火箭还是高炮,防雹作业都是有效的,这几个地方防雹效果的差异,主要是由于各种作业装备的作用方式不同引起的.针对火箭防雹作业特点,提出了提高火箭防雹效果的5点建议：（1）提高雹云识别能力;（2）合理布设防雹作业网;（3）使火箭具备爆炸催化能力;（4）采用自旋方式改善火箭飞行的稳定性;（5）采用爆炸自毁方式或其它快速自毁方式.     

51a新疆雹灾损失的时空分布特征

用新疆1952-2002 a的900例雹灾资料,对雹灾发生频次、受灾面积、经济损失的时空分布特征进行分析。结果表明,新疆雹灾频次、受灾面积、经济损失从20世纪70年代开始增长较快,受灾面积、频次1990年达到最大,可比经济损失最大值出现在1995年。雹灾主要集中在4～9月,雹灾发生频次6月最多,受灾面积5月份最多,可比经济损失值以7月份最大。按灰色关联灾情评估模型可将新疆分为严重雹灾区、重雹灾区、中雹灾区、轻雹灾区和微雹灾区五个区域。其中:阿克苏为雹灾重点防御地区,喀什、塔城、伊犁、博州、石河子为次重点防御地区。     

Influence of Hail Suppression on the Hail Trend in Serbia

The influence of hail suppression by silver iodide seeding on the trend in the number of hail days (hail trend) in the Republic of Serbia was studied in three cases: (1) in Vojvodina region, Northern Province of Serbia, in two periods, from 1967 to 2002 when there was no hail suppression, and from 2003 to 2009 when hail suppression was extended to the entire territory; (2) in Serbia proper (Serbia without the Provinces), in two periods, from 1967 to 1984 when hail suppression was spreading, and from 1985 to 2009 when hail suppression occurred over the entire territory; and (3) in the same period from 1967 to 2002 on the two adjacent territories of Vojvodina and Serbia without the Provinces, where no hail suppression occurred in the first and hail suppression did occur in the second. The hail trend in Serbia was calculated on the basis of all observed data from all synoptic and climatological stations for the period 1967 to 2009. The results associate hail suppression with the stagnation of the hail trend rather than its decrease, and show that hail suppression did not have statistically unique influence on the hail trend.     

Changes in growing season in the Northeastern United States

ABSTRACT

Changes in growing season length (GSL) are of concern for agricultural, phenological, economic, epidemiological, and bioclimatological reasons. This research identifies spatial and temporal changes over the last several decades in GSL, along with the day-of-year of the last spring freeze and first autumn freeze, for the northeastern United States – a region particularly susceptible to such changes due to the large population and intense economic activities. Results suggest that growing season has significantly increased in length since 1980 as compared to prior to 1980, and both spatial and temporal variation in GSL has decreased for the region over time. Changes to GSL for this region are driven more by a shift in the first autumn freeze date than the last spring freeze date. The areas of greatest increase in GSL in the pre- vs. post-1980 period tend to be in the high elevations, near large water bodies, and near the largest cities. Results will assist environmental planners as they prepare mitigation and adaptation strategies amid a changing environment.     

LETTERS TO THE PRESIDENT OF THE ASSOCIATION

Topographic shading curtails the period and complicates the geographic patterns of insolation in mountainous areas. Maps derived from oblique aerial photographs of shadow lines cast by the irregular, mountainous east horizon in Provo, Utah are used as a case study to illustrate an alternative to existing techniques of solar radiation data collection. For study areas of several hundred square kilometers, this method may be superior in resolution and at the same time more error free and economically feasible than other methods. Measurement of solar inputs received at sample stations scattered through the mapped area show that the phenomenon of topographically delayed sunrise has a distinct effect on daily totals of radiation in the manner suggested by the maps.     

ON THE SENSITIVITY OF CONCLUSIONS ABOUT THE BASES OF COGNITIVE DISTANCE

The “ecological fallacy’ inherent in two studies of the correlation of cognitive distance with objective distance and travel time is considered. The studies reach opposite conclusions using similar types of data, but both involve different types of aggregation of cognitive-distance judgments. It is shown that, under certain circumstances, correlations based on aggregate data can lead to reverse conclusions to those based on more behaviorally valid disaggregate data. Hence such aggregation is unjustifiable and, as a result, neither study's conclusions can be relied upon.     

明代雹灾的时空特征分析

对我国明代的雹灾史料进行整理和分类,构建了明代雹灾数据库,并根据冰雹的大小和造成的危害程度进行等级划分。利用统计等方法揭示明代雹灾的时间特征和频次规律;通过明代各省区行政区划图展示不同等级雹灾的空间分布特征。结果表明：我国明代共有1 970次雹灾发生,可分为3种不同的等级,其中2级雹灾最多;明代的雹灾具有明显的阶段性和季节性特征,雹灾多集中于明代的中后期且多发于春、夏季节,秋季较少,冬季最少;在空间分布上,明代雹灾多集中于东部,西部少,中部不多,南北少,不同省区雹灾的季节分布也不同。这些研究结论可为雹灾的预测、预防提供历史背景。     

VARIABILITY IN HIGH TEMPERATURE EXTREMES IN THE SOUTHEASTERN UNITED STATES

Forty-one years of data from 13 first-order National Weather Service stations in the southeastern United States were analyzed to determine the spatial variability in the frequency and duration of hours and days when temperatures were ≥32° C (high-heat). Spatial analysis indicated that extreme high temperature characteristics from individual stations should not be combined into a regional or statewide average. For determining high-heat scenarios, May through September (summer) average maximum temperature (Tmax) was found to be a more appropriate indicator of high-heat conditions than the average temperature (Tmean). Comparing conditions in average warm and cool summer seasons indicated that: (1) increases in the frequency and duration of high-heat hours and days from cool to warm summer seasons range from 70 to 997%; (2) the number of high-heat hours per day increases significantly (27 to 118%) from cool to warm summer seasons; (3) increases in Tmax from cool to warm summer seasons are greater than increases for Tmean; (4) Tmean values underestimate the number and duration of high-heat events; and (5) the diurnal temperature range increases during warm summer seasons. These results show that great variability already exists in today's climate characteristics, and that any potential shift in average temperature will cause even greater changes in the frequency and duration of extreme high temperatures in this region. [Key words: climate variability, temperature extremes, southeast United States.]     

A CAUTIONARY NOTE ON THE USE OF THE ALLOMETRIC FUNCTION TO ESTIMATE URBAN POPULATIONS

Use of the allometric function to estimate the number of inhabitants of urban areas, given knowledge of their land areas obtained through satellite photographs, rests as much on the stability of this function over time as on its goodness of fit to a cross section of cities at a single point in time. Using urban land and population data for four countries, the United States, Japan, Sweden, and Norway, this paper demonstrates that the function is not generally stable but rather has been subject to rapid upward shifts over the past 10 to 20 years.     

多普勒雷达资料在人工防雹作业中的应用分析

利用多普勒雷达回波资料分析2007年6月23日贵州黔西南州一次高炮消雹作业过程,表明高炮消雹作业的效果是显著的。作业前后,回波在强度、高度和形态面积上都有明显变化,作业有效地扼制了雹云的发展,化雹为雨,起到了防灾减灾的作用。