共查询到19条相似文献，搜索用时 46 毫秒
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本文利用1961～2019年贵州省85站逐日的雨凇、雾凇资料,通过对样本数据的统计分析以及3个现有指标的对比分析,订正了贵州省单站凝冻过程的指标和分级标准,并根据新的标准对其特征进行分析。结果表明,贵州省凝冻过程的持续天数为3～39天,随着凝冻过程持续天数的增加,其发生频率呈指数下降。凝冻过程开始初日和结束终日时间序列之间存在凝冻过程开始初日偏早/偏晚,结束终日也偏早/偏晚的现象。随着凝冻等级的升高,其影响范围在不断缩小,但大值区主要仍集中在26.5°～27.5°N,低值区仍在贵州省北部和南部地区,且59a间4个不同等级单站凝冻过程的站次均呈缓慢减少趋势。4个典型站的凝冻过程主要集中出现时间基本一致,1月占比最多,2月次之,而11月最少。分旬来看,主要集中出现在1月中旬至2月上旬,11月上旬最少。 相似文献
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基于逐时气象观测资料和一日4次ERA-Interim再分析资料对2018年1月4一7日(第一次过程)和24—27日(第二次过程)安徽省南部(简称皖南)两次冻雨过程中冻雨分布、时间演变及环流特征进行分析,结果表明:通过自动气象观测仪器的风速突然降为0 m·s~(-1)、风向固定不动,可大致推测出冻雨出现时间,比人工观测到冻雨出现时间早。两次冻雨天气均是在准静止锋天气下出现的,但导致冻雨形成的机制不同。第一次过程为典型的"冰相融化"机制,第二次过程为典型的"过冷暖雨"机制。东亚大陆近地面冷高压使两次冻雨天气中皖南处在东北气流之下,其带来的冷温度平流形成近地面到地面的冷垫,而750 hPa高度附近南支槽槽前暖湿气流带来暖温度平流是融化层或逆温层维持和发展的主要原因。当高空温度层结满足冻雨出现条件时,地面0℃线的位置会直接影响冻雨出现的范围。 相似文献
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2011年1月贵州继2008年后又一次出现了历史罕见的低温雨雪凝冻灾害,具有开始时间早、日平均气温低、凝冻日数持续时间长等特点。该文利用气候整编资料、中国国家气候中心资料和NCEP逐日再分析资料对此次过程的环流背景以及物理量场进行了分析。分析表明：此次过程是在“La Nina”事件的大背景下发生的;北半球极涡活动异常,且中心偏向于东半球,强而稳定,欧亚大陆500hPa位势高度距平呈“北高南低”的分布,这种分布是贵州省冬季重凝冻年的主要环流形势之一;青藏高原的南北支槽异常活跃,不断输送水汽和引导冷空气南下;高原南侧、盂加拉湾北部的偏西风水汽输送和来源于西太平洋副高南侧的偏东风水汽输送为贵州省源源不断地输送水汽;逆温层的存在和阶段性的维持是贵州大范围冻雨持续出现的重要原因。 相似文献
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2011~2013年中国冻雨、冻毛毛雨和冻雾的特征分析 总被引：2，自引：1，他引：1
研究冰冻天气的特征对于更好的认识冰冻天气,提高此类天气的预警预报能力,从而达到防灾减灾有重要意义。利用2011~2013年间中国民航机场的一小时或半小时一次的例行观测和特殊观测资料,分析了冻雨、冻毛毛雨和冻雾天气的时空分布、持续时间和气象条件等特征。研究结果表明:我国大部分地区均会发生冰冻天气。冻雨和冻毛毛雨的频发区与其持续时间较长区比较一致,而冻雾的少发区,其持续时间也可能较长。我国冰冻天气最容易在冬季(12~2月)发生,在1月出现的比例最高;在凌晨[00~07时(当地时间,下同)]出现频率相对较高,午后(13~14时)出现频率最低。一次冰冻天气的持续时间一般不超过2个小时。温度在-3~-1℃,露点温度在-4~-1℃,温度露点差在0~1℃时冰冻天气发生的频率最大。出现冰冻天气时的风向以东北风和北风为主,而平均风速在2~3.9 m s-1时冻雨和冻毛毛雨发生的频率最大。我国冻雨和冻毛毛雨发生时,同时常会有雾或轻雾;冻雾出现时,一般不会伴随其他天气。 相似文献
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利用1961～2004年冬季贵州省84个测站凝冻日数资料,分析了2004年冬季(2004年12月～2005年2月)贵州省凝冻天气的时空分布特征,结果表明2004年冬季在省的中部一线有3个明显的重凝冻中心,主要出现了6次持续凝冻天气过程,其中强度最强、持续时间最长、影响范围最严重的是2004年12月23日到2005年1月2日的凝冻天气过程,6个测站达到特重级凝冻标准;与过去40a相比,省的中部一线较常年同期明显偏重,全省平均凝冻日数也是20世纪90年代以来较重的年份,凝冻集中期全省平均温度是1986年以来最冷的一年.分析这6次凝冻天气过程的天气系统,都是有偏北路径冷空气南下影响贵州,在贵州南部形成静止锋;同时高空有低槽东移影响,并且有冷空气不断补充,静止锋活跃,使凝冻天气得以持续. 相似文献
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《气象与环境学报》2016,(2)
为了探讨冬季冻雨天气成因并提高冻雨天气的预报能力,利用常规气象观测资料、加密气象观测资料和NCEP再分析资料,对2010年2月安徽省一次冻雨过程进行天气学分析,利用WRF中尺度模式对此次冻雨过程进行数值模拟,并对冻雨发生的物理量场和层结条件进行分析.结果表明:此次安徽省南部山区和北部平原地区的冻雨天气过程主要是由于北方强冷空气快速南下,在安徽省境内大陆冷高压与西太平洋副热带高压相遇,形成鞍形场切变线引起的.从模拟结果来看,此次安徽省山区与平原地区冻雨天气的成因和层结特征均有较大区别,山区冻雨天气的形成与山脉对冷暖空气的阻挡和抬升有关;而平原地区冻雨天气的形成需强冷空气快速南下,产生有利于冻雨天气发生的层结结构.山区冻雨天气发生时,具有较大的逆温梯度和较高的冷心高度;平原地区冻雨天气发生时,近地面有较大的负变温中心和较高的冷心高度,但与逆温梯度不存在稳定的对应关系.冻雨天气的产生与逆温强度、冷垫厚度及其变温幅度均有一定的关系,是一个复杂的物理过程. 相似文献
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基于1961~2019 年贵州省84站逐日雨凇观测资料,确定了贵州省区域性凝冻过程指标,并根据新标准对区域性凝冻过程的时空特征进行了分析。结果表明:1961~2019 年贵州省区域性凝冻过程次数与累积天数均呈减少趋势,在年代际时间尺度上均呈 “偏多—偏少—偏多—偏少”的变化特征,在年际时间尺度上均存在7~8a与3~4a的变化周期。贵州省区域性凝冻过程频发区及中心站点高频区主要集中在中部一线,在东北部和南部部分地区发生频率较低。贵州省区域性凝冻过程可分为中东部型、中部型、中西部型、西部型及全省型共5类,其中以中西部型和全省型为主。 相似文献
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贵州凝冻天气主要以雨凇形式出现,该文利用黔南州1968年12月—2018年3月12日地面观测站资料,分析了50 a来出现的雨凇和凝冻天气的空间分布、初始时间、持续时间等方面,同时利用NECP/NCAR的2.5°×2.5°格点的逐日再分析资料,探究了黔南出现特重级凝冻和重级凝冻的500 hPa环流特征。结果表明:凝冻天气的频次和持续时间的长短,与其地理位置和地貌特征有明显的关系,尤其瓮安出现的凝冻次数最多、持续时间最长,罗甸、荔波50 a来未出现凝冻天气;黔南凝冻平均初日在1月中旬到下旬初,平均终日在1月下旬后期;在区域性凝冻天气环流场分析中,高纬地区的冷高压位置越往南且强度越大,则影响黔南出现区域性凝冻天气可能性越大,尤其在太平洋副高西伸的情况下,凝冻灾害最重。 相似文献
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Both direct and indirect effects of freezing drizzle on ice accretion were analyzed for ten freezing drizzle events during a comprehensive ice thickness, fog, and precipitation observation campaign carried out during the winter of 2008 and 2009 at Enshi Radar Station (3017'N, 10916'E), Hubei Province, China. The growth rate of ice thickness was 0.85 mm h－1 during the freezing drizzle period, while the rate was only 0.4 mm h－1 without sleet and freezing drizzle. The rain intensity, liquid water content (LWC), and diameter of freezing drizzle stayed at low values. The development of microphysical properties of fog was suppressed in the freezing drizzle period. A threshold diameter (Dc) was proposed to estimate the inuence of freezing drizzle on different size ranges of fog droplets. Fog droplets with a diameter less thanDc would be affected slightly by freezing drizzle, while larger fog droplets would be affected signicantly. Dc had a correlation with the average rain intensity, with a correlation coefficient of 0.78. The relationships among the microphysical properties of fog droplets were all positive when the effect of freezing drizzle was weak, while they became poor positive correlations, or even negative correlations during freezing drizzle period. The direct contribution of freezing drizzle to ice thickness was about 14.5%. Considering both the direct and indirect effects, we suggest that freezing drizzle could act as a catalyst causing serious icing conditions. 相似文献
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Analyzed is a phenomenon of the freezing rain observed in Perm krai on December 14, 2010, when the surface temperature was ?10.9°C. The process of cooling of falling drops is numerically simulated and their temperature is computed on the basis of the data of radio sounding of the atmosphere. It is demonstrated that the large-size drops do not have time to reach the supercooling state and, when falling to the ground, have a positive temperature. The finer drops are cooled to the negative temperature. An executed estimation of the process of transformation of falling drops into ice at the crystallization of the supercooled water demonstrated that the volume fraction of the ice crust of drops at the phase transition does not exceed 3% even under optimum cooling conditions. 相似文献
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现在地面测报工作从查算到报表制作都主要由计算机完成 ,只有原始记录部分完全靠观测员如实记录。由于各站的技术水平、对《规范》的理解以及传统记录习惯等不同 ,在一些目测项目上存在很大差别 ,特别是在云与降水、能见度与天气现象配合方面表现突出。下面对检查中发现的一些记录进行分析 ,以求能得到统一。记录一 :某 3次观测站某日 0 8时记录 :ＶＶ =0 8 Ｎ =1 0 云状为 :ＳｃｏｐＦｎ ,2 0～0 8时降水量为 1 2ｍｍ ,天气现象 :夜间只有雨 ,白天为 :·0 8— 1 0∶2 5 =仔细分析该记录 ,我认为天气现象记录在夜间和白天都应当记录有… 相似文献
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Tsoi-Ching Yip 《Atmospheric Research》1995,36(3-4)
The Chaine and Skeates icing model is a semi-empirical model. It is based on the formulations proposed by McKay and Thompson (1969). Horizontal ice accretion thickness is assumed to be the observed precipitation amount adjusted by the appropriate ice density. Clear ice density is assumed to be 900 kg/m3. Vertical ice accretion thickness is proportional to precipitation rate and wind speed. Ice accretion occurs only at temperatures near or below freezing. All impinging water is assumed to turn into ice. The freezing fraction is assumed to be one. Horizontal and vertical ice thicknesses are changed into equivalent radial thickness (Chaine and Castonguay, 1974). All parameters used in this model can be derived from routinely observed meteorological data. Icing amounts estimated by this model are very sensitive to wind speed and precipitation rate. Model simulated 30-year return period equivalent radial ice amounts for 20 Quebec locations are compared with collocated Passive Ice Meter data and the results are found to be reasonable. The variation of ice amount with height can be estimated by a log function proportional to 10 m icing amounts, except in British Columbia. Also the 30-year return period equivalent radial ice estimates due to freezing precipitations for 303 locations in Canada are calculated and an Ice Map is plotted. In the future, more work needs to be done to estimate ice amounts due to other forms of icing such as in-cloud rime icing and wet snow. These quantities should be added to the current amounts to make the ice map complete. Anecdotal ice information should be collected to validate the map. 相似文献
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Role of soil freezing in future boreal climate change 总被引：3，自引：0，他引：3
We introduced a simple scheme of soil freezing in the LMDz3.3 atmospheric general circulation model (AGCM) to examine the potential effects of this parameterization on simulated future boreal climate change. In this multi-layer soil scheme, soil heat capacity and conductivity are dependent on soil water content, and a parameterization of the thermal and hydrological effects of water phase changes is included. The impact of these new features is evaluated against observations. By comparing present-day and 2×CO2 AGCM simulations both with and without the parameterization of soil freezing the role of soil freezing in climate change is analysed. Soil freezing does not have significant global impacts, but regional effects on simulated climate and climate change are important. In present-day conditions, hydrological effects due to freezing lead to dryer summers. In 2×CO2 climate, thermal effects due to freeze/thaw cycles are more pronounced and contribute to enhance the expected future overall winter warming. Impact of soil freezing on climate sensitivity is not uniform: the annual mean warming is amplified in North America (+15%) and Central Siberia (+36%) whereas it is reduced in Eastern Siberia (–23%). Nevertheless, all boreal lands undergo a strong attenuation of the warming during summertime. In agreement with some previous studies, these results indicate once more that soil freezing effects are significant on regional boreal climate. But this study also demonstrates its importance on regional boreal climate change and thus the necessity to include soil freezing in regional climate change predictions.
相似文献
| G. KrinnerEmail: Phone: +33-476-824241Fax: +33-476-824201 |
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本文对2016年12月4-5日新疆克拉玛依市出现历史罕见的冻雨天气过程,通过实况观测资料的综合分析,并利用WRF区域模式进行数值模拟,分析冻雨形成的环流形势、风场、大气层结以及冻雨区云系。结果表明,大尺度环流形势为西风带上弱波动东移,配合中低层西南急流,以及冷暖气团交汇,为冻雨的形成提供了必要的天气尺度条件。本次冻雨的形成机制为融化机制,水汽输送层主要位于冰晶层,水汽受冰晶效应充分凝结后再在暖层融化,落入冷层迅速冷却为冰粒或过冷却雨滴。逆温层是冻雨发生的主要条件,并且随着逆温层减弱,降水物的相态也从冰粒转为过冷却水。本次冻雨过程与南方冻雨不同的是,克拉玛依上空在降水前期就存在强逆温,并且在冻雨发生前逆温层出现减弱再加强的变化。 相似文献
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根据且末气象站1971-2012年冬季逐日气温资料,通过对冬季极端最低气温、日平均气温≤-10℃负积温、最低气温≤-18℃日数、≥1cm积雪持续日数等冻害气象因子进行标准化处理,运用主成分分析方法计算红枣综合冻害指数,并采用线性回归,man-kendall检验和小波分析方法对综合冻害指标进行分析,结果表明,综合冻害指数数值越小,冻害越严重;确定综合冻害指数≤-1.0时为红枣出现冻害的临界指标;冻害指数在1977年前后出现了一次增大突变;预测2013年红枣受冻可能性小. 相似文献
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I. S. Vasil’ev A. I. Vasil’ev Ya. I. Torgovkin 《Russian Meteorology and Hydrology》2012,37(3):170-176
The spatial distribution of long-term average air freezing and thawing indices in Yakutia was investigated using the data
of 156 meteorological stations located in this region. The regularities of variations of air freezing and thawing indices
are revealed depending on the impact of zonal, regional, and local environmental factors. The concrete correlations with the
latitude, longitude, and altitude are obtained. The effects of climatic processes and relief of regional and local levels
are estimated. Based on the revealed relationships, the 1 : 5000000-scale maps are plotted to demonstrate the spatial variations
of air freezing and thawing indices. 相似文献