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1.
Cloud-to-ground (CG) lightning observations for the warm seasons (May-September) of 1989 and 1990 were analyzed for the Great Lakes region in order to assess the diurnal variations in the lightning characteristics. Several parameters, including flash rate, the spatial extent of lightning activity, first stroke peak current, and the percentage of positive flashes, varied markedly over the course of the day. In contrast, other parameters, such as the frequency of lightning periods and the multiplicity of both negative and positive CG flashes, displayed little diurnal variation. A large degree of intraseasonal (i.e., month-to-month) variation was observed in the diurnal patterns for several of the lightning parameters. 相似文献
2.
This study integrates past research methodologies, data from the National Lightning Detection Network (NLDN), and geographic information system techniques to assess the lightning and severe weather hazard relationship for the 27–28 April 2011 United States tornado outbreak. NLDN and Doppler radar data are used to examine the cloud-to-ground (CG) lightning characteristics associated with seven supercell thunderstorms that produced long-track, significant and/or violent tornadoes. Analyses indicate that CG lightning flashes alone do not provide enough information for the detection of a lightning jump prior to tornadogenesis. All seven supercells were dominated by negative-polarity CG lightning flashes; which is expected due to the geographic location and elevated low-level moisture found in the outbreak environment. The correlation between low-level mesocyclone strength and total CG lightning flash rate was varied and inconsistent among all storms despite their formation and sustenance in similar environmental and geographic space. Additional case studies, as well as climatological approaches, are required to discover if the varying lightning–tornado relationships found in this study are consistent with other tornadic environments. 相似文献
3.
利用雷电定位资料、多普勒雷达资料和FY-2E卫星资料对发生在滇西南的两次台风低压西行形成飑线过程的地闪变化特征进行了对比分析,结果表明：2次飑线过程均以负地闪占主导地位,“7．17”过程正、负地闪频数峰值均出现在飑线成熟阶段,正地闪峰值超前于负地闪峰值10～15min;正、负地闪集中发生在冷中心区后侧的温度梯度大值区和辐合线附近回波强度t〉40dBz、回波顶高≥12km的强回波区域;“9．22”过程正地闪频数呈单峰型变化,负地闪出现3个峰值,对应着3次飑线发展,密集负地闪出现在前侧TBB温度梯度大值区和强回波区左后侧强度≥40dBz、回波顶高≥12km的强回波区;负地闪减弱阶段正地闪开始活跃正地闪出现在后侧冷云中心。两次飑线过程中-10℃层回波强度的跃增总超前于负地闪的跃增6—30min左右。 相似文献
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5.
This article analyzes lightning/landscape interactions across the State of Colorado. Ten years (2003–2012) of warm season cloud-to-ground (CG) lightning activity are mapped at 500 × 500 m2 to characterize the distribution of thunderstorm activity. Geospatial analyses quantify lightning activity by elevation, physiographic region, and mountain range, and time-series animations outline the general movement of thunderstorms. From these spatio-temporal perspectives, our objective is to elucidate lightning/landscape interactions as they occur over a topographically and climatologically diverse landscape. The information aids meteorologists by exposing orographic and rainshadow effects, mesoscale meteorological effects, fluxes of moisture sources, thunderstorm initiation zones, and thunderstorm movements. Other benefits extend to wildland fire managers, those who maintain lightning-vulnerable infrastructures, and, from a human risk perspective, an overall awareness to those who work and play outdoors. Major findings include (1) elevation alone does not determine the degree of lightning activity, (2) across the state's mountain ranges, lightning density varies considerably, but the number of lightning days does not, and (3) the time of lightning initiation and maxima varies by elevation, with higher mountain elevations experiencing most activity 1 h before lower mountain elevations, and 3 h before lower Great Plains locations. 相似文献
6.
武当山是世界文化与自然遗产,因而武当山风景区的雷电防护尤为重要。截取风景区的地闪数据,以1 km2范围为基本单元,得到各单元内2008-01-01―2011-12-31期间的全部地闪频次、极性、强度等参数,分析武当山风景区雷电环境及武当山地理环境对雷电活动的影响。研究表明：研究区域闪电集中发生在6―8月份的午后T 14：00―18:00。闪电频数日变化规律明显,最大值出现在T 16:00,最小值出现在T 10:00―11:00。雷击大地密度整体上随高度表现出明显的增长趋势,雷电流强度平均值与高度大致呈现反向分布趋势,拟合出的雷击大地密度与高度关系式的相关系数R达0.834 56。大气环流特征表明,武当山雷电天气主要有3种类型：副热带高压西北部雷电型、高空槽雷电型和低涡雷电型,其中副热带高压西北部雷电型占主导。 相似文献
7.
《Polar Science》2007,1(1):1-15
Statistical characteristics of the surface meteorology are examined at Syowa Station (69°00′S, 39°35′E), which is located on an island near the coastal region of the Antarctic continent, based on operational observations made over the 50-year period from February 1957 through January 2007, which includes missing periods equivalent to 5 years. Statistics are obtained for the surface temperature, sea level pressure (SLP), and horizontal winds in terms of frequency distribution, frequency power spectra, seasonal variation, diurnal variation, inter-annual variation, and trends, using hourly observation data, and several interesting characteristics are elucidated. The mean temperature, SLP, and wind speed over the 50-year period are −10.5 °C, 986 hPa, and 6.6 m s−1, respectively. The frequency distribution of temperature is far from the normal one, because less variation exists in summer at higher temperatures. The predominant wind direction is northeasterly (southwestward), and a weak secondary peak is observed in the southerly (northward) direction in the frequency distribution. The directional constancy of winds is 0.78. The frequency spectra over a wide range of 2 h to 20 years exhibit clearly isolated peaks corresponding to annual and diurnal frequencies and their higher harmonics. An important finding is that the spectral shape is proportional to a power of the frequency with a transition frequency for all physical parameters. The transition frequencies correspond to about 5 days for temperature and winds and 3 days for SLP, most likely due to cyclonic activity. A peak in the 11-year solar cycle is not identified in any spectrum. Another interesting feature is the dominance of semi-annual and semi-diurnal variations in SLP, while annual and diurnal variations are dominant for temperature and winds. Statistically significant trends are not detected for annual mean surface temperature and SLP over the 50-year period, while a positive trend is significant for wind speed. These trends are also examined as a function of the months. The inter-annual variation of SLP is well correlated with that of the Antarctic Oscillation index, indicating that Syowa Station can be regarded as a typical Antarctic station. Furthermore, statistical analysis was conducted for blizzards (severe snow storms), in terms of duration, and seasonal and inter-annual variation in frequency of occurrence. It is shown that the blizzards are dominant in the period from late March to late October. No systematic variation in blizzard frequency was observed during the 50-year period. Instead, the frequency depends largely on the year with a minimum of nine in 1988 and a maximum of 42 in 1982. As a typical example, a synoptic chart is used to show the cause of a strong snow storm on 27 May 1996, when the absolute maximum gust was observed. 相似文献
8.
《The Journal of geography》2012,111(1):13-20
Abstract Long-term collection of soil temperature with depth is important when studying climate change. The international program GLOBE® provides an excellent opportunity to collect such data, although currently endorsed temperature collection protocols need to be refined. To enhance data quality, protocol-based methodology and automated data logging, along with other physical data, were used to collect soil temperature to a depth of one meter. Data show that diurnal and shallow variation ceases at around 50 cm depth. Therefore the need to incorporate deeper depths into the current protocols for heat flux calculations is warranted. The manual methodology was also found to give representative data. 相似文献
9.
雷电活动参数作为反映区域雷电活动特征的重要指标,地形对其影响不容忽视。利用2014—2018年青海省地闪数据、数字地形高程数据以及HWSD土壤数据集,定量分析海拔、坡度、坡向以及土壤电阻率对青海省地闪分布特征的影响。结果表明：（1） 青海省地闪主要集中在海拔3150~4850 m、坡度0~35°的地区,其中东北坡向地闪次数最多,东南坡向地闪次数最少,地闪对应的土壤电阻率主要集中于100 Ω·m。（2） 地闪密度随海拔的升高先增大后减小,随坡度的增大而减小;地闪平均强度随海拔的升高先减小后增大,随坡度的增大而增大。（3） 选取92°27′00″~97°44′24″E、31°40′48″~34°16′48″N地闪活跃区域,对其1 km×1 km网格内地闪数据与地理参量平均值进行相关性分析,所选区域内地闪密度与平均海拔呈正相关关系,与平均坡度呈负相关关系;而地闪强度与平均海拔呈负相关关系,与平均坡度呈正相关关系。 相似文献
10.
The study analyzes summertime lightning incidence data across northern tropical Africa from the TRMM satellite sensor during 1998–2011. It uses harmonic analyses to detect the spatial patterns in diurnal variations of lightning activity across the study area. The results are in conformity with previous studies examining diurnal patterns of convective weather processes in this region, with most lightning activity concentrated over land areas. The peak time of lightning activity over most of the study area was during late afternoon hours, from around 1700 to 1900 local standard time. The peak time of lightning activity was observed during early morning hours in some coastal areas, such as Cameroon, which can be a result of local-level convergence between the land and sea breeze. A general progression in the time of lightning activity from late afternoon to early evening hours was observed throughout the interior of the study area, which may be attributed to land-surface heating and associated mesoscale convective systems, and to upper-level circulation in the form of the African Easterly Jet Stream. 相似文献
11.
巴丹吉林最高沙山区CO2浓度与昼夜变化规律 总被引：1，自引：0，他引：1
为查明沙漠区CO2浓度和对大气CO2的影响以及在全球碳循环中的作用,利用红外CO2监测仪,在2009年5月对全球最高大的巴丹吉林诺尔图东大沙山等进行了17个钻孔CO2浓度的昼夜观测。结果表明,巴丹吉林大沙山不同观测点CO2浓度差异较大,各观测点CO2浓度变化在0.01%~0.075％之间;夜间沙层CO2浓度低,白天CO2浓度高;CO2浓度昼夜变化明显,从早7时到次日7时1~5m各深度CO2浓度均呈现由低到高再到低的变化规律;在24h内,沙层CO2浓度变化存在4个转折点,分别出现在凌晨5时、11时、18时和21时左右。在沙层水分一定的条件下,昼夜温度变化是造成沙层CO2浓度昼夜规律变化的主要原因,两者呈正相关关系;含水量较高的沙层CO2浓度明显高于含水量较低的沙层;5m深度以上沙层CO2浓度均高于地表空气CO2浓度,表明极端干旱的高大沙山区是CO2的来源区,也指示环境恶劣的裸露高大沙山区微生物活动产生的沙层CO2浓度仍然超过了大气CO2浓度。 相似文献
12.
西江河口段溶解无机碳稳定同位素组成的时空变化 总被引：3，自引：1，他引：2
For researching the spatio-temporal variation of the stable isotopic composition of the riverine dissolved inorganic carbon（DIC）,we had carried out a survey throughout the hydrologic year during which theδ^13CDIC of the surface water and its physicochemical parameter were examined along the Xijiang River Inner Estuarine waterway from September 2006 to June 2007.There was a striking seasonal variation on the averageδ^13CDIC,as the averageδ^13CDIC in summer（-13.91‰）or autumn（-13.09‰）was much less than those in spring（-11.71‰）or winter（-12.26‰）.The riverineδ13C DIC was controlled by decomposed condition of the riverine organic matter linking the seasonal variation of the physicochemical parameter in the surface water according to the correlation analysis which indicated notable relations betweenδ^13CDIC and water temperature（p=0.000;r=-0.569）or betweenδ^13CDIC and oxide-reduction potential（p=0.000;r=0.646）.The striking positive correlation between δ^13CDIC and the sampling distance happened in the summer rainy season,while striking negative correlation happened in the spring dry season,indicating that river-sea interaction influenced water physicochemical parameters and controlled the riverine DIC property in the survey waterway.In view of the riverineδ^13CDIC decreasing for the decomposition of the terrestrial organic matter in the rainy season in summer and increasing for the briny invaded zone extending in the spring dry season along the waterway from the Makou gauging station to the Modaomen outlet,theδ^13CDIC spatio-temporal variation was closely related to the geographical environment of the Xijiang drainage basin. 相似文献
13.
利用2005—2020年新疆雷电灾害统计数据及2013—2020年新疆闪电定位监测数据,从雷电灾害发生的行业分布、人员伤亡、经济损失等角度,对新疆2005—2020年雷电灾害特征进行了分析。结果表明：（1） 2005—2020年新疆共发生雷电灾害事件154次,导致82人伤亡,近16 a雷电灾害事件呈逐年递减趋势,其中月分布高发期在4—8月,这与新疆的雷电月活动规律一致。（2） 雷电灾害空间分布特征和地域有很大的相关性,雷电灾害主要集中在北疆阿勒泰地区、塔城东南部地区以及伊犁哈萨克自治州直属县市一线,而南疆的雷电灾害数量基本上很少。（3） 雷电灾害事件主要发生在农村,占雷电灾害事件总数的62.3%。雷电灾害事件造成的行业受损比例由多到少依次是民用电子设备、工厂设备、电力设备和建筑物。本研究结果可为新疆防雷减灾工作提供重要的理论依据。 相似文献
14.
沙漠与城市气溶胶散射系数变化比较 总被引：1，自引：0，他引：1
利用塔克拉玛干沙漠大气环境观测试验站和中国气象局乌鲁木齐沙漠气象研究所承担的乌鲁木齐大气成分观测站2010年1月1日至12月31日的单波段积分浊度计的观测资料,分析了沙漠（塔中）和城市（乌鲁木齐）两种不同下垫面地区的气溶胶散射系数的变化特征。（1）散射系数小时平均值：塔中地区变化范围在39.6～8 442.8 Mm-1,平均值318.4 Mm-1;乌鲁木齐变化范围在28.9～6 590.0 Mm-1,平均值451.5 Mm-1;乌鲁木齐小时平均值在1 000 Mm-1以上的高值区间大于塔中地区。（2）散射系数日变化：塔中呈现单峰变化,其中最大值387.0 Mm-1出现于凌晨02：00,最小值276.4 Mm-1出现于午后的17：00;乌鲁木齐呈现三锋变化,3个峰值分别出现于09：00、14：00、22：00,与塔中地区存在明显差异。（3）散射系数月均值变化：塔中的月平均值最大是4月,为500.2 Mm-1,最小是2月,为145.9 Mm-1;乌鲁木齐月均值最大在2月,为1 086.3 Mm-1,最小值在7月,为101.1 Mm-1,两地区月均值变化整体呈现相反的现象。（4）散射系数季节变化：塔中地区春季>夏季>秋季>冬季;乌鲁木齐冬季>秋季>春季>夏季。 相似文献
15.
《自然地理学》2013,34(5):385-406
Researchers have utilized radar reflectivity returns and lightning flashes separately and together to locate convection with tropical cyclones (TCs). Most studies utilizing both datasets have examined TCs over the ocean, while landfall observations have been limited to a few TCs. This study employs a GIS to delineate regions of high radar reflectivity values within 45 landfalling TCs. The percentage of convective regions contained within each quadrant placed relative to storm motion and deep-layer vertical wind shear is calculated. These percentages are then compared to those from previous studies of quadrant-based lightning flash locations. Results indicate that the GIS-based radar analysis may be identifying TC regions that are electrically active. Both the radar- and lightning-based analyses show that convection shifts from the right to the front of the storm as forward velocity increases. Convection is located left of the shear vector when storm motion is 45-135° counterclockwise from the shear vector, and downshear when shear-minus-motion angles are 315-45°. Additionally, storms that became extratropical within 72 hours of landfall had more convection forward of the circulation center and left of the shear vector, and may produce less lightning than the remaining TCs. 相似文献
16.
1956-2003年拉萨河流域径流变化趋势 总被引：4，自引：1，他引：3
Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of the two hydrological stations （Lhasa and Tanggya） and the meteorological data of the three meteorological stations （Damxung, Lhasa and Tanggya）. The trends and the change points of runoff and climate from 1956 to 2003 were detected using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between runoff and climate change were analyzed using multiple linear regression. The major results could be summarized as follows： （1） The annual mean runoff during the last 50 years is characterized by a great fluctuation and a positive trend with two change points （around 1970 and the early 1980s）, after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides, the monthly mean runoff with a positive trend is centralized in winter half-year （November to April） and some other months （May, July and September）. （2） The trends of the climate change in the study area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter season. 相似文献
17.
In this study we analyzed the diurnal spatial patterns of cycles of ozone (O3) and respirable suspended particulate (RSP) matter in Hong Kong between 2001 and 2011. We used harmonic analysis to reveal the diurnal cycle in the seasonal-level spatial patterns. The diurnal cycle of O3 is stronger in the northeast rural areas of Hong Kong than in the urban center due to the lower titration effects of nitric oxide in the rural areas. For RSP, the southern sections show the strongest diurnal cycle and the northeastern sections show the weakest diurnal cycle, which could be explained by the heavy vehicular traffic in the southern urban areas and light vehicular traffic in the northeast rural areas. The diurnal patterns of O3 and RSP both show stronger cycles in the summer months, which might be related to the diurnal rainfall pattern. The time of maximum for O3 is around 1400 Local Standard Time (LST) in the afternoon in summer, whereas a wider range in the time of maximum, between 1100 and 1400 LST, was observed in winter. The spatial pattern of the time of maximum for RSP showed a gradual progression from the center of the city to the west, between 1300 and 1700 LST, which is consistent with rush hour traffic. 相似文献
18.
夏季不同天气条件下沙漠辐射和能量平衡的对比分析 总被引：4，自引：0，他引：4
利用2009 年7 月24 日-9 月12 日“巴丹吉林沙漠陆-气相互作用观测试验”资料,对比分析了典型晴天和阴天下巴丹吉林沙漠地表辐射、能量平衡和土壤温度的日变化规律.结果表明：①巴丹吉林沙漠典型晴天条件下总辐射、地表反射辐射、地表长波辐射、有效辐射、净辐射的峰值和日积分值都比典型阴天条件下大,大气长波辐射比阴天条件下小.两种天气条件下净辐射日积分值占太阳总辐射的1/3.②沙漠地区典型晴天地表反射率呈U型,白天均值为0.32;阴天变化较平缓,均值为0.29.③两种天气条件下地表热量平衡都以感热输送为主,波文比分别为4.55 和1.16.晴天不平衡能量达到净辐射的20%,阴天为30%.④晴天条件下有效能量夜间为负值,白天为正值,阴天全天为正值;湍流能量全天均为正值.能量闭合度(EBR)晴天平均为0.68,阴天为0.76.⑤土壤温度5~10 cm日较差逐渐减小,20、40 cm日变化不明显;5 cm土壤热通量日变化较大,20 cm土壤热通量振幅较小. 相似文献
19.
蒸腾速率(Tr)是植物生理生态学研究中表征蒸腾耗水的常用指标,研究植物的蒸腾耗水有助于了解当地生态系统稳定性和水资源的可持续利用,但在遥感应用尤其在干旱区遥感应用中很少被使用。本文以古尔班通古特沙漠南缘的主要建群种多枝柽柳(Tamarix ramosissima)作为研究对象,应用高光谱指数法对其Tr日变化过程进行研究,寻找和确定最佳的Tr光谱指数。选择的6个光谱指数判定系数R2介于0.06~0.73,其中简单比值(SR)光谱指数有最高的判定系数(R2=0.73)、较低的均方根误差(RMSE=0.24)和较为简单的形式,光谱范围处于近红外波段(1 645~1 655nm)/(1 775~1 785nm)。SR作为Tr最佳光谱指数,对植被水分关系变化敏感,能够较好地记录和监测Tr日变化过程,有益于揭示光谱指数物理和生理机制。 相似文献
20.
巴丹吉林沙漠典型湖泊湖气界面水一热交换特征 总被引：1，自引：0，他引：1
利用2012年8月-2013年7月在巴丹吉林沙漠腹地典型湖泊上用涡动相关系统观测的湍流资料,分析了湍流方差统计特征、微气象特征,计算了湍流热通量和湖泊蒸发量,初步结论为：①湖面上局地环流复杂,湍流三维风速的标准差与稳定度(Z/L)之间满足1/3次律。②湖面辐射分量具有明显季节变化和日变化特征,结冰期和非结冰期能量分配不同,冬季湖泊将储存的能量向大气传递;潜热通量和感热通量季节变化存在差异,但均有明显的昼夜变化特征。③湖气界面的感热通量在不同的月份也存在差异,感热以湖泊向大气传递为主;潜热通量夏半年远大于冬半年,在一天中6:00-8:00时处于最低值,15:00-16:00时达到峰值,在冬季会出现潜热向下输送现象。感热通量和潜热通量日变化呈负相关,湖面有效能量主要分配给潜热,湖泊同周围环境以水汽交换为主。④湖面平均蒸发速率为3.97 mm/d,累计蒸发量为1450±10 mm/a,同期的蒸发量是降水量的20多倍,湖泊主要靠地下水补给。这些结论可为进一步研究巴丹吉林沙漠腹地湖泊群的水循环及补给来源提供参考。 相似文献