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通过对桂林最近２０ａ降雪过程的统计分析，得出桂林降雪天气的环流特征和相关要素，找出预报降雪的天气形势和预报指标，最后结合现有数值产品资料的检验应用，归纳降雪天气预报思路。 相似文献
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通过对2000年以来云南出现的4次强降雪过程进行分类对比分析和诊断分析, 结果表明:横槽型和北脊南槽型是4次强降雪的主要中高纬环流形势, 3次有南支槽配合, 1次无南支槽活动, 其中2次横槽型造成的强降雪范围广、强度大; 4次强降雪过程云南西侧都有充沛的水汽输送, 水汽通量增大 (即水汽的增加) 是云南强降雪的必备条件, 强降雪出现在较强水汽通量辐合区中, 且落区在辐合中心的偏东一侧、θse线陡立区附近以及暖湿不稳定区域; 强降雪在多普勒雷达上显示为20~30 dBz左右的层状云回波, 对流层中下层的高空冷暖平流和高空西南急流是有南支槽影响的强降雪天气的主要大尺度特征, 而低层偏东急流是无南支槽影响的强降雪的主要特征, 因此高低空急流的形成是强降雪的关键。 相似文献
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桂林降雪天气分析与预报 总被引：8，自引：1，他引：8
通过对桂林最近20a降雪过程的统计分析，得出桂林降雪天气的环流特征和相关要素，找出预报降雪的天气形势和预报指标，最后结合现有数值产品资料的检验应用，归纳降雪天气预报思路。 相似文献
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山东半岛冷流强降雪和非冷流强降雪的对比分析 总被引：3，自引：2，他引：1
利用1981—2000年常规气象观测和NCEP/NCAR再分析资料,采用合成分析和动力诊断分析方法,对冷流强降雪与非冷流强降雪的空间分布、大气环流、水汽输送、稳定度和垂直运动进行对比分析。结果表明：冷流强降雪是发生在槽后西北气流里的中小尺度不稳定降雪,非冷流强降雪是发生在槽前西南气流中大尺度稳定性降雪。冷流强降雪具有明显的地方性特点,是强冷空气对下垫面物理状态强迫响应的结果。提出强冷空气与渤海暖水面相互作用产生的大气边界层不稳定是产生冷流降雪的本质,在这种边界层不稳定层结中发生的降雪是冷流降雪的概念。 相似文献
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从全州产生降雪的天气特点、天气形势和降雪发生前后单站要素变化三个方面对全州县降雪天气进行分析,发现:北方强冷空气影响是造成降雪的主要原因,高空小槽东移或横槽转竖引导冷空气南下是造成全州降雪的主要环流形势;单站剖面图上14时的T、P、E曲线大多表现为降雪前气压升高、温度下降,降雪后气压普遍下降,气温回升,水汽压受多种因素影响,变化不规律,但在整个降雪过程中,水汽压大都在8hPa以下,较普通降水过程偏低。分析单站剖面图上等压线走向发现,降雪天气大多属于完全高压型和不完全高压型,积雪比较厚的情况大多发生在不完全高压类型中。 相似文献
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2010年冬季浙江两次强降雪过程的对比分析 总被引：3，自引：0，他引：3
利用NCEP1°×1°再分析资料,对浙江2010年冬季两次强降雪过程的环流形势和物理量场进行了分析和讨论.结果表明:两次过程都是北方冷空气与西南暖湿气流交汇所致,冷空气较强时,锋区迅速南压,降雪持续时间较短,暴雪产生在中低层切变线的风速辐合区中;而冷空气强度适中时,“冷垫”和静止锋长时间存在,降雪持续时间则较长,暴雪产生在低空急流的左前方;降雪区上空有明显的水汽通量辐合,水汽通量大值区的演变与降雪过程有较好的对应关系;低空辐合和高空辐散的配置是强降雪产生的有利动力条件,其强度越强,降雪也越强. 相似文献
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中国西天山季节性积雪热力特征分析 总被引：3，自引：0，他引：3
利用中国天山积雪雪崩站干、湿雪雪层内每隔5min一次的10层雪温数据,探讨了一次降雪过程后干、湿雪的雪层温度特征,对比分析了干、湿雪的雪面能量平衡方程中各分量的差异。结果表明:(1)整个冬半年积雪各层温度基本<0℃,雪温日变化振幅由雪面向下逐渐减小,积雪深层温度的波峰(谷)值稍滞后于积雪浅层温度极值1～2天。(2)湿雪冷中心的出现时间早于干雪,暖中心的出现时间晚于干雪,太阳辐射对湿雪的穿透深度大于干雪。(3)雪层温度振幅变化与能量吸收随雪深都呈指数衰减分布。积雪密度越大,吸收系数越小,穿透深度越大。(4)干雪雪面的感热通量和潜热通量几乎都为负值,积雪积累。湿雪雪面的潜热通量与感热通量方向相反,互相抵消,所以净辐射是导致湿雪消融的主要因素。 相似文献
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基于新疆昌吉州5个国家气象站2008—2010年积雪深度大于等于0 cm的实测地面温度与雪面温度,对0 cm地面温度（含最高、最低）、雪面温度（含最高、最低）及云量、日照时数、雪深进行统计分析,找出不同积雪深度下地面温度与雪面温度的关系,并以阜康市天池气象站2011年所有积雪日数据对关系模型作检验。结果显示：地面温度与雪面温度的关系有3个雪深分层：5 cm以下、6~40 cm和40 cm以上,积雪深度为0~5 cm时,地面温度与雪面温度差值很小,受雪深及天气条件影响明显,雪深6~40 cm,主要受雪深影响,雪深超过40 cm,地面温度趋于定值。 相似文献
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利用青海省甘德两次降雪过程的微气象观测数据,探讨了两场降雪过程雪深、雪密度、雪中含冰量、雪中含水量和雪面温度的变化情况,分析了地表反照率与雪密度、雪中含冰量及雪中含水量的关系,结合降雪过程近地面温、湿、风廓线特征分析了积雪对近地面温、湿、风梯度的影响。结果表明:积雪覆盖会导致地表反照率显著增加,降雪过后正午时地表反照率可高达0.8～0.9。随着积雪的消融,地表反照率逐渐减小;积雪反照率与雪密度和雪中含冰量呈正相关,与雪中含水量呈负相关;地表积雪覆盖会导致近地面温度梯度绝对值减小,相对湿度梯度绝对值在凌晨减小、午后增大,地表积雪覆盖对近地面风速梯度变化并无特定的影响。 相似文献
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A new, physically-based snow hydrology has been implemented into the NCAR CCM1. The snow albedo is based on snow depth, solar zenith angle, snow cover pollutants, cloudiness, and a new parameter, the snow grain size. Snow grain size in turn depends on temperature and snow age. An improved expression is used for fractional snow cover which relates it to surface roughness and to snow depth. Each component of the new snow hydrology was implemented separately and then combined to make a new control run integrated for ten seasonal cycles. With the new snow hydrology, springtime snow melt occurs more rapidly, leading to a more reasonable late spring and summer distribution of snow cover. Little impact is seen on winter snow cover, since the new hydrology affects snow melt directly, but snowfall only indirectly, if at all. The influence of the variable grain size appears more important when snow packs are relatively deep while variable fractional snow cover becomes increasingly important as the snow pack thins. Variable surface roughness affects the snow cover fraction directly, but shows little effect on the seasonal cycle of the snow line. As an applicaion of the new snow hydrology, we have rerun simulations involving Antarctic and Northern Hemisphere glaciation; these simulations were previously made with CCM1 and the old snow hydrology. Relatively little difference is seen for Antarctica, but a profound difference occurs for the Northern Hemisphere. In particular, ice sheets computed using net snow accumulations from the GCM are more numerous and larger in extent with the new snow hydrology. The new snow hydrology leads to a better simulation of the seasonal cycle of snow cover, however, our primary goal in implementing it into the GCM is to improve the predictive capabilities of the model. Since the snow hydrology is based on fundamental physical processes, and has well-defined parameters, it should enable model simulations of climatic change in which we have increased confidence.This paper was presented at the Second International Conference on Modelling of Global Climate Variability, held in Hamburg 7–11 September 1992 under the auspices of the Max Planck Institute for Meteorology. Guest Editor for these papers is L. Dümenil 相似文献
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中国冬季多种积雪参数的时空特征及差异性 总被引：6，自引：2，他引：4
利用1979~2006年冬季中国站点最大雪深和站点雪日、卫星遥感雪深、积雪覆盖率和雪水当量5种积雪资料,从多角度深入细致地分析了我国冬季积雪的时空变化特征。结果表明:5种积雪资料的经验正交分解第一模态都表现为中国南、北方反位相的特征,即当新疆和东北三省-内蒙古地区积雪偏多(少)时,青藏高原和南方地区积雪偏少(多)。新疆和东北三省-内蒙古地区的雪深、积雪覆盖率和雪日随时间有逐渐增多的趋势,而其中边缘山区的雪水当量表现出减少的趋势,青藏高原地区的积雪表现出与其完全相反的特征。南方地区站点最大雪深和雪日表现出随时间减少的趋势,卫星遥感难以监测到该区积雪。相比较而言,卫星遥感资料比较适合高原和山区缺少气象站的地区及北半球更大区域积雪的研究,而站点资料更适用于中国中东部和平原地区积雪的区域研究。雪深、雪日、积雪覆盖率和雪水当量这些多样性积雪参数存在一定的差异性,因此5种积雪资料结合使用才能得到更准确的结论。 相似文献
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By using Comprehensive Land Surface Model (CLSM), three snow cases, i.e., France Col de Porte 1993/1994, 1994/1995 and BOREAS SSA-OJP 1994/1995, were simulated. The simulated results were compared with the observations to examine the capability of the model to describe the evolutions of snow cover under two different land cover conditions. Several sensitivity experiments were performed to investigate the effects of the parameterization schemes of some snow cover internal processes and vegetation on the model results. Results suggest that the CLSM simulates the basic processes of snow cover accurately and describes the features of snow cover evolutions reasonably, indicating that the model has the potential to model the processes related to the snow cover evolution. It is also found that the different parameterization schemes of the snowfall density and snow water holding capacity have significant effects on the simulation of snow cover. The estimation of snowfall density mainly impacts the simulated snow depth, and the underestimation (overestimation) of the snowfall density increases (decreases) the snow depth simulated significantly but with little effect on the simulated snow water equivalent (SWE). The parameterization of the snow water holding capacity plays a crucial role in the evolution of snow cover, especially in the ablation of snow cover. Larger snow water holding capacity usually leads to larger snow density and heat capacity by storing more liquid water in the snow layer, and makes the temperature of snow cover and the snow ablation vary more slowly. To a smaller snow water holding capacity, contrary is the case. The results also show that the physical processes related to the snow cover variation are different, which are dependent on the vegetation existed. Vegetation plays an important role in the evolution of soil-snow system by changing the energy balance at the snow-soil surface. The existence of vegetation is favorable to the maintenance of snow cover and delays the increase of underlying soil temperature. 相似文献
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Snow albedo is an important factor influencing the snow surface energy budget and snow melting,
yet uncertainties remain in the calculation of spectrally resolved snow surface albedo because the spectral
composition (visible versus near infrared) of the incident solar radiation is seldom available. The influence
of the spectral composition of the incoming solar radiation on the snow surface albedo, snow surface energy
budget, and final snow ablation is investigated through sensitivity experiments of four snow seasons at two
open sites in the Alps by using a multi-layer Snow-Atmosphere-Soil-Transfer scheme (SAST). Since the snow
albedo in the near infrared (NIR) spectral band is significantly lower than that in the visible (VIS) band,
and almost the entire NIR part of the solar radiation is absorbed in the top layer of the snow pack, given
a fixed amount of incoming solar radiation, a lower VIS/NIR ratio implies that more NIR radiation is
reaching the ground surface and more is absorbed by the top layer of the snow pack, therefore, speeding
up the snow melting and increasing the surface runoff, although a lesser part of the solar radiation in
the visible band is transmitted into and trapped by the sub-layer of the snow pack. The above VIS/NIR ratio
effect of the incoming solar radiation can result in a couple of days difference in the timing of snow
ablation and it becomes more significant in late spring when the total solar radiation is intensified with
seasonal evolution. Snow aging also slightly intensifies this VIS/NIR ratio effect. 相似文献
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近50年云南省降雪的气候变化特征 总被引：2，自引：1，他引：1
利用云南省1961-2008年120个测站逐日降雪资料,分析了云南省降雪频次和范围的时空特征和气候变化.结果表明:近50年云南省的年降雪频次和范围总体呈减少趋势,平均每年频次约减少4.5频次.各月的降雪频次和范围都呈负趋势.12月降雪频次减少趋势最显著,4月降雪范围减少趋势最显著.降雪频次长期趋势变化有明显的空间变化.对于年降雪频次西北部比东北部和东部减少得多,滇西北降雪频次每年约减少0.44频次.进一步对云南省年降雪量和积雪深度的长期趋势变化进行分析.云南省近50年,降雪范围逐步减少,年降雪量和平均最大积雪深度呈增加的趋势.说明近年来在云南气候趋于暖湿背景下,年降雪频次和范围呈逐渐减少趋势,但强降雪的频次却增加了. 相似文献
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亚洲季风模拟试验中青藏高原积雪强迫问题的讨论 总被引：10，自引：3，他引：10
青藏高原积雪对亚洲季风和东亚，南亚时旱涝灾害的影响，百余年来一直为中外气候学家所瞩目。近几年来用大气环流模式进行数值试验已成为该研究领域的主要手段，但是由于假设的积雪强迫不同，模拟结果很不一致。作者概据美国宇航局ＳＭＭＲ微波逐候积雪深度１０年的观测结果，提出了一个真实的青藏高原积雪强迫试验方案。 相似文献
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青藏高原东部牧区雪灾的气候特征分析 总被引：30，自引：21，他引：30
通过对 196 7— 1996年 2 5个测站的雪灾资料分析 ,揭示了青藏高原东部牧区有雪灾期从上年10月到当年 5月长达 8个月 ,雪灾在一年之中有 3个高发月 :11月、3月和 2月 ;雪灾主要发生在巴颜喀拉山南缘和东麓地区 ,近 30a来呈上升趋势。 196 8— 1976年冬春为一较长时段的雪灾发生的低值期 ,从 1977— 1992年有 3个高峰期和 2个低谷期 ,从 1993年开始又进入高发期 ;高原东部牧区冬春雪灾存在着明显的 5 6a的和较弱的 2 3a周期变化。本文中定义发生在 15月的雪灾为后冬雪灾 ,发生在10 12月的雪灾为前冬雪灾。研究表明 ,70年代是前冬雪灾的高发期 ,80年代末到 90年代是后冬雪灾的高发期。雪灾期西太副高的年际差异是雪灾发生年际振荡的一个可能原因 相似文献