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1.
杨晓霞  夏凡  张骞  侯淑梅  刘畅 《气象科技》2018,46(3):605-618
利用各种观测资料和NCEP/NCAR 1×1°再分析资料,对2012年7月30日夜间和31日夜间鲁西北连续两天强降雨天气进行诊断和对比分析。结果表明:强降水产生在西风槽前和副热带高压边缘的偏南暖湿气流中,西风槽稳定少动,台风在东南沿海北上,副高加强北抬,为鲁西北连续两天的强降水提供了天气尺度背景。925hPa及以下的低层,来自于渤海的偏东气流和来自于华东沿海的东南气流同时向鲁西北强降水区输送水汽,低层比湿大,CAPE和K指数较高。第1次强降水产生在偏南气流的暖区中,降水强度大,维持时间短。第2次强降水期间,低层有冷空气锲入,把暖湿气流抬升,前期为对流性降水,中后期转为稳定性降水,降水强度小,维持时间较长。850hPa及以下倒槽式切变线和中尺度低涡环流是造成强降水的中尺度影响系统,近地面层来自于渤海的东北气流与来自于东南沿海的东南暖湿气流形成中尺度涡旋,产生气旋式辐合上升,触发对流不稳定能量释放。对流云团在鲁西北形成长形的中尺度对流系统(MCS),稳定少动,有明显的列车效应和后向传播特征。强降水具有较强的日变化,夜间发展增强,白天减弱。  相似文献   

2.
对流层低层偏东风对北京局地暴雨的作用   总被引：8，自引：2，他引：6  
本文利用风廓线仪、地面自动站观测资料及NCAR/NCEP 1°×1°分析资料等,对北京地区两次局地暴雨天气过程的对流层低层偏东风进行了对比分析研究,重点分析了浅薄和深厚两次偏东风的形成机制、偏东风的垂直结构特征和温、湿特性,以及偏东风在北京局地暴雨中的作用等。主要结论如下:(1)浅薄偏东风活动在距地面高度500 m 以下,水平尺度约250 km,时间尺度约12 h, 地面风速平均约1 m/s;深厚偏东风活动在距地面高度3000 m 以下,水平尺度大于600 km,持续时间大于24 h,地面风速平均约4 m/s。(2)浅薄偏东风由边界层内浅薄的次天气尺度暖性低涡引起,深厚偏东风由天气尺度地面暖性低压倒槽的发展引起。(3)偏东风具有高相当位温的属性,其源地是北京东部或东南部的暖湿气团;在暖湿偏东风上方800～600 hPa 存在干冷空气活动,形成了有利的对流不稳定层结;浅薄偏东风暖湿能量的局地集中特征更为显著,而深厚偏东风在水汽和能量的持续输送方面,以及与500 hPa 偏西风形成较强的、有利于强对流风暴发展的低层垂直风切变方面作用更为显著。(4)浅薄偏东风在时间和空间上与近地面层辐合中心对应较好,与中高空辐散有较好配合,动力作用明显,直接起到了对流风暴的触发机制作用;深厚偏东风与辐合中心对应较差,与垂直运动及上层辐散也没有很好的配合,与对流风暴的触发没有直接的关系。但是深厚偏东风在对流层低层对应厚达3000 m 的潮湿空气层,削弱了雨滴下落过程中产生的蒸发降温作用,有利于对流的发展和维持。  相似文献   

3.
Climate change in Hispañola is studied since 1900 using a variety of datasets. The longer station-observed temperature record has a significant trend of 0.012 °C/year, while the shorter reanalysis datasets exhibit faster warming, suggesting accelerating greenhouse radiative absorption and Hadley circulation. Rainfall trends are insignificant in the observed period, but a CMIP5 model simulation predicts a significant drying trend. The spatial pattern of climate trends was mapped with reanalysis fields and indicates a faster rate of warming over the eastern half of the island, where observations are dense and the drying trend is greatest. Northeasterly trade winds strengthen on the Atlantic side of the island. While trends intensify in the satellite era compared to the earlier 20th century, part of that effect is ascribed to an upturn in the Atlantic Multi-decadal Oscillation.  相似文献   

4.
A climate-monitoring network was implemented in a large private preserve along the southern shore of Lake Superior. The network uses a dense sampling design to assess the spatial and temporal influence of a large, cold body of water on adjacent terrestrial surfaces. Based on a 3-year record, near-shore sites are 1–2°C cooler than sites 5?km inland in spring and summer, and 1°C warmer in winter. Near the shore, winds are from the NNW most of the year, and are much stronger in winter. Inland, southwesterly flow is typical and overall wind velocity is lower and more consistent. This decoupling is attributable to the influence of the Huron Mountains, a topographic barrier that restricts the lake effect to a narrow coastal zone. A 2-year record of hourly air temperature measurements from 26–30 sites across the study area demonstrates that the mean daily temperature can differ by as much as 11°C, but the average difference is 2.5–3.0°C.  相似文献   

5.
基于黑球湿球温度识别了中国复合热浪,并定量分析了城市化和西太平洋副热带高压（简称西太副高）对中国复合热浪的协同作用。结果表明：1979—2019年中国复合热浪的发生天数、强度和影响范围都在逐步上升,尤其在2010年以后出现跃升,比20世纪80年代增大了4倍左右;城市化快速发展和西太副高增强协同加剧了中国复合热浪;较早发展的城市化对热浪天数、强度、范围增长的贡献分别是9.2％、12.5％、7.5％,而同期西太副高的增强对三类热浪指数有约30％的正贡献,甚至在考虑全球变暖对西太副高的加强作用时,西太副高的贡献增至70％左右。这表明,快速发展的城市化和全球变暖背景下增强的西太副高的协同作用可以解释80％以上21世纪初中国复合热浪的跃升。  相似文献   

6.
ABSTRACT

South Indian Ocean Rossby waves (SIO-RW) are identified in the Global Ocean Data Assimilation System (GODAS) 1.5–7?yr filtered sea surface height (SSH) time series. There is a persistent three-year oscillation in the 5°–15°S latitude band from 55° to 85°E. Field correlations show little coupling at 90°E, but as the SIO-RW undulates westward at approximately 0.19?m?s?1 across the mid-basin, a northwest–southeast axis of warm sea surface temperatures (SSTs) and deep convection forms. Many teleconnections in earlier work are confirmed: interannual pulses of zonal wind in the eastern basin trigger the SIO-RW via anticyclonic wind stress curl. New insights derive from an understanding of links with the upper troposphere. As the SIO-RWs move westward with the onset of an El Niño in the Pacific, increased convection over the north Indian Ocean corresponds to reduced evaporation and SST warming. Mid-tropospheric heating T′?>?2°C over the northwest Indian Ocean accelerates the southern sub-tropical jet to greater than 10?m?s?1 over the southeast Indian Ocean, reinforcing the anticyclonic vorticity. The downstream acceleration of the jet generates upper-level divergence and moist convection over the western basin, anchoring an atmospheric Rossby wave in a northwest–southeast alignment underpinned by differential propagation of the SIO-RW. As the ocean Rossby wave reaches Africa, the coupling fades and transitions. What distinguishes Indian Ocean from Pacific Ocean Rossby waves are their southern latitude and higher frequency. The tropical mid-tropospheric heating that accelerates the southern sub-tropical jet shifts westward in tandem with the SIO-RW.  相似文献   

7.
The present work investigates possible impact of the non-uniformity in observed land surface temperature on trend estimation, based on Climatic Research Unit (CRU) Temperature Version 4 (CRUTEM4) monthly temperature datasets from 1900 to 2012. The CRU land temperature data exhibit remarkable non-uniformity in spatial and temporal features. The data are characterized by an uneven spatial distribution of missing records and station density, and display a significant increase of available sites around 1950. Considering the impact of missing data, the trends seem to be more stable and reliable when estimated based on data with < 40% missing percent, compared to the data with above 40% missing percent. Mean absolute error (MAE) between data with < 40% missing percent and global data is only 0.011°C (0.014°C) for 1900–50 (1951–2012). The associated trend estimated by reliable data is 0.087°C decade–1 (0.186°C decade–1) for 1900–50 (1951–2012), almost the same as the trend of the global data. However, due to non-uniform spatial distribution of missing data, the global signal seems mainly coming from the regions with good data coverage, especially for the period 1900–50. This is also confirmed by an extreme test conducted with the records in the United States and Africa. In addition, the influences of spatial and temporal non-uniform features in observation data on trend estimation are significant for the areas with poor data coverage, such as Africa, while insignificant for the countries with good data coverage, such as the United States.  相似文献   

8.
A long-lived and loosely organized squall line moved rapidly across Urumqi, the capital city of Xinjiang Uygur Autonomous Region of China on 26 June 2005, generating hail and strong winds. The squall line was observed by a dual Doppler radar system in a field experiment conducted in 2004 and 2005 by the Chinese Academy of Meteorological Sciences and the local meteorological bureau in northwestern China. The 3D wind fields within the squall line were retrieved through dual Doppler analyses and a variational Doppler radar analysis system (VDRAS). The formation and structure of the squall line as well as the genesis and evolution of embedded convective cells were investigated. During its life period, the squall line consisted of six storm cells extending about 100 km in length, and produced hail of about 25 mm in diameter and strong surface winds up to 11 m s-1. Radar observations revealed a broad region of stratiform rain in a meso-β cyclone, with the squall line located to the west of this. Two meso-γ scale vortices were found within the squall line. Compared to typical squall lines in moist regions, such as Guangdong Province and Shanghai, which tend to be around 300--400 km in length, have echo tops of 17--19 km, and produce maximum surface winds of about 25 m s-1 and temperature variations of about 8oC this squall line system had weaker maximum reflectivity (55 dBZ), a lower echo top (13 km) and smaller extension (about 100 km), relatively little stratiform rainfall preceding the convective line, and a similar moving speed and temperature variation at the surface.  相似文献   

9.
The results of two oceanographic surveys, carried out by TINRO-Center in August 2003 and 2007 in the southwestern part of the Chukchi Sea under conditions of opposite regimes of atmospheric circulation in the Eastern Arctic, are given. A stationary anticyclone with the center over the Beaufort Sea in 2007 favored the transport of warm air masses to the Arctic basin and more rapid ice melting. The surface layer temperature to the east of Wrangel Island reached 12°C (6–8°C above the normal). The upwelling of bottom waters was registered in the coastal zone due to the southeastern winds, the Siberian coastal current was not observed. In summer 2003, on the contrary, the cyclonic circulation type prevailed over the eastern seas of the Arctic, the northwestern winds in the coastal zone favored the spreading of the Siberian coastal current almost up to Bering Strait, the water temperature was 2–3°C below normal. The coastal thermal front was formed in both situations: in the first case, due to upwelling, in the second case, due to the spreading of cold coastal desalinated East Siberian waters.  相似文献   

10.
The one-layer radiation atmospheric model with SRB (Surface Radiation Budget) database for 1984-2007 was used to obtain the estimation of variations in the distribution of surface temperature for a case of general increase in atmospheric albedo by 1%, that is, surface temperature decreases by 1°C on average on the globe.  相似文献   

11.
The spatial patterns of precipitation anomalies during five 30-yr warm periods of 691-720, 1231-1260, 1741-1770, 1921-1950, and 1981-2000 were investigated using a dryness/wetness grading dataset covering 48 stations from Chinese historical documents and 22 precipitation proxy series from natural archives. It was found that the North China Plain (approximately 35 -40 N, east of 105 E) was dry in four warm periods within the centennial warm epochs of 600-750, the Medieval Warm Period (about 900-1300) and after 1900. A wet condition prevailed over most of China during 1741-1770, a 30-yr warm peak that occurred during the Little Ice Age (about 1650-1850). The spatial pattern of the precipitation anomaly in 1981-2000 over East China (25 -40 N, east of 105 E) is roughly consistent with that in 1231-1260, but a difference in the precipitation anomaly appeared over the Tibetan Plateau. The spatial patterns of the precipitation anomalies over China varied between all five 30-yr warm periods, which implies that the matching pattern between temperature and precipitation change is multiform, and the precipitation anomaly could be positive or negative when a decadal warm climate occurs in different climate epochs. This result may provide a primary reference for the mechanism detection and climate simulation of the precipitation anomaly of the future warm climate.  相似文献   

12.
The sea level pressure (SLP) variability in 30–60 day intraseasonal timescales is investigated using 25 years of reanalysis data addressing two issues. The first concerns the non-zero zonal mean component of SLP near the equator and its meridional connections, and the second concerns the fast eastward propagation (EP) speed of SLP compared to that of zonal wind. It is shown that the entire globe resonates with high amplitude wave activity during some periods which may last for few to several months, followed by lull periods of varying duration. SLP variations in the tropical belt are highly coherent from 25°S to 25°N, uncorrelated with variations in mid latitudes and again significantly correlated but with opposite phase around 60°S and 65°N. Near the equator (8°S–8°N), the zonal mean contributes significantly to the total variance in SLP, and after its removal, SLP shows a dominant zonal wavenumber one structure having a periodicity of 40 days and EP speeds comparable to that of zonal winds in the Indian Ocean. SLP from many of the atmospheric and coupled general circulation models show similar behaviour in the meridional direction although their propagation characteristics in the tropical belt differ widely.  相似文献   

13.
1. IntroductionFor the latest 15 years, the climate change hasbeen paid more attention by the policy-makers, scien-tists, and the public. The global warming of 0.4-0.8°Cfor the 20th century has been measured by the instru-mental observations. The atmospheric concentrationof CO2 increased from 280 ppm for the period 1000-1750 to 368 ppm in the year 2000 with an increase of27%-35%. In the light of new evidence and taking intoaccount the remaining uncertainties, most of the ob-served warming o…  相似文献   

14.
张文龙  崔晓鹏  黄荣  黎慧琦 《大气科学》2019,43(5):1171-1190
本文利用雷达、加密地面自动站等高时空分辨率的观测资料,结合NCEP 1°×1°再分析资料、常规观测等资料,对2011年6月23日发生在北京城区的极端强降水事件开展了细致的观测和诊断分析。结果表明,这次极端强降水事件,主要是由向东南移动的东北—西南走向的飑线右端的强降水超级单体（High Precipitation Supercell,简称HPS）造成的,这是目前已有文献记载的中国发生纬度最高的HPS。HPS在移动方向的右后侧和右前侧均有明显的“V”型入流,这不同于已有HPS模型,表明中、低层干冷空气和低层暖湿气流特征显著。在环境条件方面,存在对流层低层逆温层,其能量存储盖作用使得雷暴具有爆发性增强的潜势,但该逆温层是在08:00～14:00（北京时,下同）的6小时内形成的,对业务预报极具挑战性。相对其他大气层结热动力参数, 风暴相对螺旋度和粗理查逊数在14:00较08:00显著增大,对HPS的发生具有一定指示作用。高空偏西风急流和低层偏东风活动显著,使得北京地区的水平风垂直切变增强,形成上干下湿的对流不稳定以及次级环流圈。高空急流造成强烈的相当位温差动平流,促进对流不稳定度发展加强。结合复杂地形作用,在北京西部100 m地形高度线附近形成显著的平原暖湿空气与山地干冷空气的干湿分界线以及风场辐合线。水汽供应主要源自低层偏东风和本地水汽积累。当飑线从西北方向侵入北京并向东南方向移动时,在北部山区,由于条件不足,雷暴没有显著发展加强;然而,在西部山区,在湖面、城市热岛、低层偏东风、冷池出流共同作用下,加之其他有利的环境条件,飑线右端雷暴强烈发展加强,特别是当经过100 m地形高度线附近时发展成为HPS,进而造成石景山区模式口站的大暴雨中心。  相似文献   

15.
This work investigates the distribution of high winds above Beaufort scale 6 in the offshore zones of China using high-resolution satellite measurements.A numerical experiment is carried out in order to find out the effects of Taiwan Island on the formation of strong winds.The analysis indicates that the distribution of high wind occurrence is similar to that of the average wind velocity in winter.High winds tend to be anchored in special topographical regions,such as the Taiwan Strait,the Bashi Channel and the southeast coast of Vietnam.High winds occur much more frequently over the warmer than the colder flank of Kuroshio front as it meanders from Taiwan to Japan.The frequency of high winds decreases drastically in spring.The Taiwan Strait maintains the largest high wind occurrence.Besides,high winds remain frequent in the Bashi Channel,the southeast tip of Taiwan Island and the warmer flank of Kuroshio front.In summer,high winds generally occur infrequently except over a broad region off the southeast coast of Vietnam near 10°N and the frequency there decreases from southwest to northeast.High winds around Taiwan Island present near axisymmetric distribution with larger frequency along southeast-northwest direction and smaller frequency along southwest-northeast direction.The dominant direction of high winds exhibits a counterclockwise circulation surrounding the island.The frequency of high winds increases rapidly in autumn and almost repeats the distribution that appears in winter.The simulation results suggest that the effects of Taiwan Island topography on high winds vary with seasons.In winter,topography is the major cause of high winds in the surrounding oceanic zones.High winds in both Taiwan Strait and the southeast corner of the island disappear and the frequency decreases gradually from south to north when the terrain is removed.However,in summer,high wind frequency derived from two simulations with and without terrain is almost identical.We attribute this phenomenon to the factors which are responsible for the formation of high winds.  相似文献   

16.
本文利用NCEP 1°×1°逐6 h再分析资料和地面区域自动站逐小时观测资料,对贵州省铜仁市梵净山东侧2020年6月29日夜间的一次特大暴雨天气过程的大尺度环流背景和中尺度天气系统进行了分析。结果表明：此次暴雨过程处于高空西北气流控制背景下,中低层动力抬升条件较弱,但深厚的暖云层和湿层、较低的自由对流高度（LFC）、抬升凝结高度（LCL）和中等到强的对流有效位能（CAPE）,配合低层水汽辐合抬升运动的爆发性增强有利于此次梵净山东侧高效率降水。暴雨落区分为A区和B区两个区域,其间降雨特征存在明显不同,A区降水开始时间早,累计雨量大,主要为偏东北风与偏东南风辐合引起的上升运动造成的对流性降水,而B区小时雨强更大,由于小尺度涡旋的发生发展、配合低层弱冷空气的抬升触发作用造成的冷性降水;且降水强度与1h正变压、负变温呈正相关关系。迎风坡和喇叭口地形的动力强迫抬升作用,利于低层水汽输送和抬升凝结,受近地层东北气流与东南偏南气流形成的中尺度辐合线触发、加强,也是此次极端暴雨形成的重要原因。  相似文献   

17.
Summary The degree-day method is commonly used to estimate energy consumption for heating and cooling in residential, commercial and industrial buildings, as well as in greenhouses, livestock facilities, storage facilities and warehouses. This article presents monthly and yearly averages and spatial distributions of heating, cooling, and industrial degree-days at the base temperatures of 18 °C and 20 °C, 18 °C and 24 °C, and 7 °C and 13 °C, respectively; as well as the corresponding number of days in Turkey. The findings presented here will facilitate the estimation of heating and cooling energy consumption for any residential, commercial and industrial buildings in Turkey, for any period of time (monthly, seasonal, etc.). From this analysis it will also be possible to compare and design alternative building systems in terms of energy efficiencies. If one prefers to use set point temperatures to indicate the resumption of the heating season would also be possible using the provided information in this article. In addition, utility companies and manufacturing/marketing companies of HVAC systems would be able to easily determine the demand, marketing strategies and policies based on the findings in this study.  相似文献   

18.
From extensive outdoor comfort campaigns, preliminary outdoor comfort ranges have been defined for the local population of Glasgow, UK, in terms of two thermal indices: ‘Temperature Humidity Sun Wind’ (THSW) and ‘Physiological Equivalent Temperature’ (PET). A series of measurements and surveys was carried out from winter through summer 2011 during 19 monitoring campaigns. For data collection, a Davis Vantage Pro2 weather station was used, which was equipped with temperature and humidity sensors, cup anemometer with wind vane, silicon pyranometer and globe thermometer. From concurrent measurements using two weather stations, one located close to the city core and another located at a rural setting, approximately at a 15-km distance from the urban area of Glasgow, comparisons were made with regard to thermal comfort levels and to urban–rural temperature differences for different periods of the year. It was found that the two selected thermal indices (THSW and PET) closely correlate to the actual thermal sensation of respondents. Moreover, results show that the urban site will have fewer days of cold discomfort, more days of ‘neutral’ thermal sensation and slightly higher warm discomfort. The most frequent urban heat island intensity was found to be around 3° C, whereas the fraction of cooling to heating degree-hours for a T base of 65 °F was approximately 1/12th.  相似文献   

19.
Abstract

The impacts of climate change on surface air temperature (SAT) and winds in the Gulf of St. Lawrence (GSL) are investigated by performing simulations from 1970 to 2099 with the Canadian Regional Climate Model (CRCM), driven by a five-member ensemble. Three members are from Canadian Global Climate Model (CGCM3) simulations following scenario A1B from the Intergovernmental Panel on Climate Change (IPCC); one member is from the Community Climate System Model, version 3 (CCSM3) simulation, also following the A1B scenario; and one member is from the CCSM4 (version 4) simulation following the Representative Concentration Pathway (RCP8.5) scenario. Compared with North America Regional Reanalysis (NARR) data, it is shown that CRCM can reproduce the observed SAT spatial patterns; for example, both CRCM simulations and NARR data show a warm SAT tongue along the eastern Gulf; CRCM simulations also capture the dominant northwesterly winds in January and the southwesterly winds in July. In terms of future climate scenarios, the spatial patterns of SAT show plausible seasonal variations. In January, the warming is 3°–3.5°C in the northern Gulf and 2.5°–3°C near Cabot Strait during 2040–2069, whereas the warming is more uniform during 2070–2099, with SAT increases of 4°–5°C. In summer, the warming gradually decreases from the western side of the GSL to the eastern side because of the different heat capacities between land and water. Moreover, the January winds increase by 0.2–0.4?m?s?1 during 2040–2069, related to weakening stability in the atmospheric planetary boundary layer. However, during 2070–2099, the winds decrease by 0.2–0.4?m?s?1 over the western Gulf, reflecting the northeastward shift in northwest Atlantic storm tracks. In July, enhanced baroclinicity along the east coast of North America dominates the wind changes, with increases of 0.2–0.4?m?s?1. On average, the variance for the SAT changes is about 10% of the SAT increase, and the variance for projected wind changes is the same magnitude as the projected changes, suggesting uncertainty in the latter.  相似文献   

20.
A regional sea-ice?Cocean model was used to investigate the response of sea ice and oceanic heat storage in the Hudson Bay system to a climate-warming scenario. Projections of air temperature (for the years 2041?C2070; effective CO2 concentration of 707?C950?ppmv) obtained from the Canadian Regional Climate Model (CRCM 4.2.3), driven by the third-generation coupled global climate model (CGCM 3) for lateral atmospheric and land and ocean surface boundaries, were used to drive a single sensitivity experiment with the delta-change approach. The projected change in air temperature varies from 0.8°C (summer) to 10°C (winter), with a mean warming of 3.9°C. The hydrologic forcing in the warmer climate scenario was identical to the one used for the present climate simulation. Under this warmer climate scenario, the sea-ice season is reduced by 7?C9?weeks. The highest change in summer sea-surface temperature, up to 5°C, is found in southeastern Hudson Bay, along the Nunavik coast and in James Bay. In central Hudson Bay, sea-surface temperature increases by over 3°C. Analysis of the heat content stored in the water column revealed an accumulation of additional heat, exceeding 3?MJ?m?3, trapped along the eastern shore of James and Hudson bays during winter. Despite the stratification due to meltwater and river runoff during summer, the shallow coastal regions demonstrate a higher capacity of heat storage. The maximum volume of dense water produced at the end of winter was halved under the climate-warming perturbation. The maximum volume of sea ice is reduced by 31% (592?km3) while the difference in the maximum cover is only 2.6% (32,350?km2). Overall, the depletion of sea-ice thickness in Hudson Bay follows a southeast?Cnorthwest gradient. Sea-ice thickness in Hudson Strait and Ungava Bay is 50% thinner than in present climate conditions during wintertime. The model indicates that the greatest changes in both sea-ice climate and heat content would occur in southeastern Hudson Bay, James Bay, and Hudson Strait.  相似文献   

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