Vertical distribution of snow cover and its relation to temperature over the Manasi River Basin of Tianshan Mountains,Northwest China

How snow cover changes in response to climate change at different elevations within a mountainous basin is a less investigated question. In this study we focused on the vertical distribution of snow cover and its relation to elevation and temperature within different elevation zones of distinct climatology, taking the mountainous Manasi River Basin of Xinjiang, Northwest China as a case study. Data sources include MODIS 8-day snow product, MODIS land surface temperature (LST) data from 2001 to 2014, and in situ temperature data observed at three hydrological stations from 2001 to 2012. The results show that: (1) the vertical distribution of snow areal extent (SAE) is sensitive to elevation in low (<2100 m) and high altitude (>3200 m) regions and shows four different seasonal patterns, each pattern is well correspondent to the variation of temperature. (2) The correlation between vertical changes of the SAE and temperature is significant in all seasons except for winter. (3) The correlation between annual changes of the SAE and temperature decreases with increasing elevation, the negative correlation is significant in area below 4000 m. (4) The snow cover days (SCDs) and its long-term change show visible differences in different altitude range. (5) The long-term increasing trend of SCDs and decreasing trend of winter temperature have a strong vertical relation with elevation below 3600 m. The decreasing trend of SCDs is attributed to the increasing trend of summer temperature in the area above 3600 m.     

2002—2018年叶尔羌河流域积雪时空变化研究

积雪是冰冻圈中较为活跃的因子,对气候环境变化敏感,其变化影响着全球气候和水文的变化。积雪覆盖日数(SCD)、降雪开始时间(SCOD)和融雪开始时间(SCMD)是影响地表物质和能量平衡的主要因素。使用MODIS无云积雪产品提取了叶尔羌河流域2002年7月-2018年6月逐日积雪覆盖率(SCP),基于像元计算了SCD、SCOD和SCMD,系统地分析了其空间分布与变化特征,并探讨了其变化的原因及积雪面积的异常变化与ENSO的联系。结果表明:(1)研究时段内,流域的积雪覆盖面积呈微弱减少趋势,与气温呈显著负相关,与降水呈显著正相关;2002-2018年,SCP随海拔的升高呈明显的线性增加趋势(R2=0.92、P<0.01));各海拔高度带最大SCP出现的月份大致随海拔的上升往后推迟,最小SCP出现月份无显著变化(集中在8月),海拔4000 m以下,春季的SCP小于冬季,海拔4000 m以上,春季的SCP大于冬季。(2)SCD、SCOD和SCMD有明显的海拔梯度,在流域内,从东北至西南,呈现出SCD增加,SCOD提前,SCMD推迟的特征;变化趋势上,流域91.9%的区域SCD表现为减少,65.6%的区域SCOD有往后推迟的趋势,77.4%的区域SCMD表现出提前的趋势。(3)2006、2008年和2017年积雪覆盖面积异常偏大,而在2010年则异常偏小,其原因可能是ENSO影响了积雪的变化。(4)以喀喇昆仑为主的高海拔地区,包括帕米尔高原东部的部分地区,其SCD、SCOD和SCMD分别表现出增加、提前和推迟的趋势,这种变化与其春秋温度的持续走低以及降水量的增加有关。     

Vertical distribution changes in land cover between 1990 and 2015 within the Koshi River Basin,Central Himalayas

The study of mountain vertical natural belts is an important component in the study of regional differentiation.These areas are especially sensitive to climate change and have indicative function,which is the core of three-dimensional zonality research.Thus,based on high precision land cover and digital elevation model (DEM) data,and supported by MATLAB and ArcGIS analyses,this paper aimed to study the present situation and changes of the land cover vertical belts between 1990 and 2015 on the northern and southern slopes of the Koshi River Basin (KRB).Results showed that the vertical belts on both slopes were markedly dif-ferent from one another.The vertical belts on the southern slope were mainly dominated by cropland,forest,bare land,and glacier and snow cover.In contrast,grassland,bare land,sparse vegetation,glacier and snow cover dominated the northern slope.Study found that the main vertical belts across the KRB within this region have not changed substantially over the past 25 years.In contrast,on the southern slope,the upper limits of cropland and bare land have moved to higher elevation,while the lower limits of forest and glacier and snow cover have moved to higher elevation.The upper limit of alpine grassland on the northern slope retreated and moved to higher elevation,while the lower limits of glacier and snow cover and vegetation moved northward to higher elevations.Changes in the vertical belt were influenced by climate change and human activities over time.Cropland was mainly controlled by human activities and climate warming,and the reduced precipitation also led to the abandonment of cropland,at least to a certain extent.Changes in grassland and forest ecosystems were predominantly influenced by both human activities and climate change.At the same time,glacier and snow cover far away from human activities was also mainly influenced by climate warming.     

基于HJ-1B数据的雪盖提取方法研究——以军塘湖流域为例

 HJ-1A、1B卫星具有较高的时间和空间分辨率,适合小流域尺度的积雪动态监测研究。本文基于HJ-1B数据,选取军塘湖流域,针对同时具有HJ-1B/CCD、IRS数据和只有HJ-1B/CCD数据两种情况展开雪盖提取方法研究。对于第一种情况,因研究区南端有大面积森林覆盖,会影响雪像元识别,选用[WTBX]NDSI[WTBZ]和[WTBX][STBX]S3[WTBZ][STBZ]两种雪盖指数,并利用[WTBX]NDVI[WTBZ]或TM影像反演的林区辅助判识积雪。结果表明:当有植被信息辅助分类时,两种雪盖指数均能较好提取出森林覆盖区的积雪,且提取结果基本一致,精度较高。对于第二种情况,因无法计算雪盖指数,采用光谱与纹理信息结合的SVM法提取雪盖,提取的面积和精度与上述方法相比略低,但很接近,说明在缺少[WTBX]IRS[WTBZ]数据的情况下,仅利用CCD仍可提取出较为准确的雪盖,满足实际应用需求。     

2001—2017年祁连山积雪面积时空变化特征

科学监测祁连山积雪面积及变化特征对该区域气候研究、雪水资源开发利用、环境灾害预报及生态环境保护等具有重要意义。基于2001—2017年MOD10A2积雪产品和气象数据,分析祁连山积雪面积动态变化特征及与气温降水关系。结果显示:(1) 2001—2017年祁连山积雪面积年际波动趋势较大,呈减小趋势,多年平均积雪面积约为5×104km2,占祁连山总面积的25. 9%;年内变化成"M"型,即在一个积雪年中有两个波峰和波谷,波峰出现在11月和1月,波谷出现在7月;季节变化波动趋势较大,夏冬季积雪面积减小趋势大于春季,秋季呈现略微增加趋势。(2)祁连山区积雪面积主要分布在3 000～4 000 m及4 000～5 000 m,积雪覆盖率随着海拔上升呈现逐渐增大的趋势;祁连山区不同坡向积雪覆盖面积差异较大,积雪覆盖率差异较小;积雪频率高值区呈典型的条带状分布,与祁连山地形相一致,呈西北—东南分布,且分布西部大于东部。(3)初步分析认为祁连山积雪面积变化对气温要素更敏感。     

A review of snow manipulation experiments in Arctic and alpine tundra ecosystems

Snow cover is one of the most important factors controlling microclimate and plant growing conditions for Arctic and alpine ecosystems. Climate change is altering snowfall regimes, which in turn influences snow cover and ultimately tundra plant communities. The interest in winter climate change and the number of experiments exploring the responses of alpine and Arctic ecosystems to changes in snow cover have been growing in recent years, but their outcomes are difficult to summarize because of the large variability in manipulation approaches, extents and measured response variables. In this review, we (1) compile the ecological publications on snow manipulation experiments, (2) classify the studies according to the climate scenarios they simulate and response variables they measure, (3) discuss the methods applied to manipulate snow cover, and (4) analyse and generalize the response in phenology, productivity and community composition by means of a meta-analysis. This meta-analysis shows that flowering phenology responded strongly to changes in the timing of snowmelt. The least responsive group of species were graminoids; however, they did show a decrease in productivity and abundance with experimentally increased snow covers. The species group with the greatest phenological response to snowmelt changes were the dwarf shrubs. Their abundance also increased in most long-term snow fence experiments, whereas species richness generally declined. We conclude that snow manipulation experiments can improve our understanding of recently observed ecosystem changes, and are an important component of climate change research.     

基于遥感监测的秦岭南北积雪日数时空变化及影响因素

以海拔依赖型变暖为理论基础,研究山地积雪对气候变暖的响应机制,是当前气候变化研究的热点问题。基于2000—2019年MODIS积雪物候数据,对秦岭南北积雪日数时空变化进行分析,探讨了秋冬两季厄尔尼诺指数（NINO）、青藏高原气压对积雪异常的影响。结果表明：(1) 2013年后秦岭南北气候由“变暖停滞”转为“增温回升”,积雪日数随之呈现转折下降,积雪日数≥10 d栅格占比由前期的35.1%下降为8.6%。(2)在垂直地带规律上,秦岭山地以1950～2000 m为临界点,大巴山区以1600～1650 m为临界点,低海拔地区积雪日数随海拔增加速率要低于高海拔地区。2100～3150 m海拔带是积雪日数的垂直变化的关键带;(3)在影响因素上,NINO C区、NINO Z区秋冬海温和青藏高原冬季高压,是秦岭山地、汉江谷地和大巴山区积雪异常的有效指示信号。当赤道太平洋中部秋冬海温偏低,且青藏高原冬季高压偏低时,上述3个子区积雪日数异常偏多。(4)在环流机制方面,相对于积雪日数偏少年,秦岭南北积雪日数偏多年1—2月0℃等温线位置偏南,低温环境为增加冰雪物质积累、延缓冰雪消融提供了气温条件;1月区域存...     

中国天山玛纳斯河流域积雪垂直分布及其与温度的关系（英文）

How snow cover changes in response to climate change at different elevations within a mountainous basin is a less investigated question. In this study we focused on the vertical distribution of snow cover and its relation to elevation and temperature within different elevation zones of distinct climatology, taking the mountainous Manasi River Basin of Xinjiang, Northwest China as a case study. Data sources include MODIS 8-day snow product, MODIS land surface temperature(LST) data from 2001 to 2014, and in situ temperature data observed at three hydrological stations from 2001 to 2012. The results show that:(1) the vertical distribution of snow areal extent(SAE) is sensitive to elevation in low(2100 m) and high altitude(3200 m) regions and shows four different seasonal patterns, each pattern is well correspondent to the variation of temperature.(2) The correlation between vertical changes of the SAE and temperature is significant in all seasons except for winter.(3) The correlation between annual changes of the SAE and temperature decreases with increasing elevation, the negative correlation is significant in area below 4000 m.(4) The snow cover days(SCDs) and its long-term change show visible differences in different altitude range.(5) The long-term increasing trend of SCDs and decreasing trend of winter temperature have a strong vertical relation with elevation below 3600 m. The decreasing trend of SCDs is attributed to the increasing trend of summer temperature in the area above 3600 m.     

北半球积雪/海冰面积与温度相关性的差异分析

积雪和海冰的时空变化对区域以及全球的气候、水文具有重要影响。基于雪冰数据和NCEP再分析气温数据,利用MK检验、滞后分析等方法,分析了积雪、海冰的时空变化特征及其与温度的相关特征。结果表明：1979-2013年,北半球积雪区、北极圈的年均温度呈显著上升的趋势,而积雪面积和海冰面积呈显著下降的趋势。在大部分地区,积雪覆盖频率随着温度的上升呈显著减少的趋势,但在中国长江中下游、青藏高原等局部地区,积雪覆盖频率随着温度的上升呈显著增加趋势。在大部分的近陆地海域,海冰覆盖频率随着温度的上升呈显著下降趋势。超前时间1~2个月的温度与海冰面积的负相关性最高。超前1~4个月的温度与积雪面积的负相关性最高。温度对海冰的影响时间比对积雪的影响时间长1~2个月。温度变化对海冰和积雪的影响存在一致性,但积雪和海冰对温度的响应时间存在差异,具有空间变异性。     

Thermal Regime of Rock and its Relation to Snow Cover in Steep Alpine Rock Walls: Gemsstock,Central Swiss Alps

Snow cover influences the thermal regime and stability of frozen rock walls. In this study, we investigate and model the impact of the spatially variable snow cover on the thermal regime of steep permafrost rock walls. This is necessary for a more detailed understanding of the thermal and mechanical processes causing changes in rock temperature and in the ice and water contents of frozen rock, which possibly lead to rock wall instability. To assess the temporal and spatial evolution and influence of the snow, detailed measurements have been carried out at two selected points in steep north‐ and south‐facing rock walls since 2012. In parallel, the one‐dimensional energy balance model SNOWPACK is used to simulate the effects of snow cover on the thermal regime of the rock walls. For this, a multi‐method approach with high temporal resolution is applied, combining meteorological, borehole rock temperature and terrain parameter measurements. To validate the results obtained for the ground thermal regime and the seasonally varying snowpack, the model output is compared with near‐surface rock temperature measurements and remote snow cover observations. No decrease of snow depth at slope angles up to 70° was observed in rough terrain due to micro‐topographic structures. Strong contrasts in rock temperatures between north‐ and south‐facing slopes are due to differences in solar radiation, slope angle and the timing and depth of the snow cover. SNOWPACK proved to be useful for modelling snow cover–rock interactions in smooth, homogenous rock slopes.     

近一千年来贺兰山积雪和气候变化

通过对历史文献中关于贺兰山积雪变化记录的研究,以及其他反映贺兰山气候变化的环境信息的分析,确认贺兰山地区西夏、元明时期为冷凉气候,积雪特征反映的气候变化与中国西部气候变化相一致。通过贺兰山与天山、太白山、点苍山积雪变化的比较,发现其时间变化过程和演化规律具有一致性,进而对12世纪寒冷期永久积雪下限进行推测。根据对一千年来贺兰山年日最低气温≤0℃日数的计算,认为12世纪寒冷期年平均气温较现代约低1.5²℃,推算当时贺兰山永久积雪下限为海拔3400³500m;以17世纪中叶为代表的小冰期年平均气温较现代约低1¹.5℃,推算当时贺兰山永久积雪下限为海拔3500³600m。     

博格达峰地区冰川和积雪变化遥感监测及影响因素分析

20世纪以来,随着全球气候变暖加剧,冰川和积雪普遍退缩,严重影响到人类的生存和社会经济的可持续发展,这一问题在我国西北干旱区的博格达峰地区及其周边地区尤为突出。以博格达峰地区为例,利用1990—2016年Landsat 5与Landsat 8遥感影像,对比分析归一化积雪指数（NDSI）、归一化冰雪指数（NDSII）、归一化主成分雪指数（NDPCSI）和缨帽转换湿度指数（WET）在博格达峰地区监测冰川和积雪的能力,同时结合研究区周边气温、降水数据和研究区地形数据,探讨博格达峰地区冰川和积雪面积变化与区域地形、气候间的响应关系。结果表明：（1） WET相对于NDSII、NDSI和NDPCSI精度值更高,可以替代NDSI、NDSII监测博格达峰地区冰川和积雪面积。（2） 博格达峰地区冰川和积雪面积呈持续退缩的趋势。1990—2016年,冰川和积雪面积减少率约20.07%,且年退缩率不断增加。（3） 高程、坡度和坡向对冰川和积雪面积变化的影响较显著,山地阴影对其影响较弱,气温的升高是冰雪面积减少的主要因素。     

基于GF-1的青藏高原东南部积雪分布及MODIS积雪产品适用性研究

青藏高原东南部海拔高,地形复杂,云量大,准确掌握该地区的积雪分布特征对于积雪灾害防治非常重要。论文以2013—2019年冬季积雪积累期云量符合要求的35景高分一号(GF-1)影像为基础,将全色影像和多光谱影像融合为2 m分辨率影像,通过目视解译获取了研究区积雪的空间分布特征,结合改进后的30 m分辨率SRTM DEM,探讨了地形对积雪分布的影响。结果表明：积雪像元在研究区范围内占比为33.1%。积雪的垂直分布特征明显：积雪在高程带4000~5000 m(高海拔)处分布较集中,积雪面积占比为18.1%;在高程带0~2000 m、2000~3000 m和6000~7000 m处积雪面积占比均不到0.1%。积雪在北坡、东北坡的分布比例较高,均为15%以上;在南坡、西坡、西南坡、东南坡分布比例较低,均为10%左右。将基于GF-1影像获取的积雪分布分别与同日获取的根据MODIS V6积雪产品计算的积雪比例(MODIS FSC)和积雪分布的对比表明,64.4%的MODIS FSC像元绝对误差不超过10%,MODIS积雪分布产品对含雪像元的漏分率和误分率平均为33.8%和32.7%,说明MODIS积雪产品在研究区的精度还具有较高的不确定性,其对低覆盖积雪反演的精度较差。这表明利用MODIS积雪产品研究青藏高原东南部积雪的时空变化特征时还需要对其积雪反演算法进行改进,同时亟需加强地面观测和基于多源遥感数据的积雪研究。研究结果可为青藏高原东南部雪冰灾害防治提供支撑。     

天山东部冰川积雪中大气粉尘的沉积特征

对我国天山东部三个研究点乌鲁木齐河源1号冰川、奎屯哈希勒根51号冰川和哈密庙尔沟平顶冰川积雪中大气粉尘沉积进行了分析研究。微粒特征分析表明,自西向东随着研究点地理环境的变化,积雪中不溶微粒的质量浓度、沉积通量和体积粒径分布众数都表现出增高趋势：奎屯哈希勒根51号冰川最小,乌鲁木齐河源1号冰川次之,哈密庙尔沟平顶冰川最大;三个研究点粒径0．57〈d〈26μm微粒的平均质量浓度分别是969μg／kg、1442μg／kg、3690μg／kg,年均沉积通量分别是58．2μg／cm^2、72．1μg／cm^2、73．8μg／cm^2。表明,哈密冰川受粉尘源影响较大．而乌鲁木齐河源与奎屯河源区受影响则相对较小。雪坑微粒浓度剖面和离子相关性分析表明,天山东部冰川积雪中污化层富含亚洲粉尘的富Ca^2＋、Na^2＋矿物;微粒体积一粒径分布众数介于3-22μm．粒径分布显示了单结构模式。研究区最近4年积雪的污化层剖面揭示了春季零星的粉尘浓度峰值以及沉积数量上较大的年际变化,意味着天山东部雪冰中粉尘沉积对大气环境变化的敏感性。     

Local Extremes in the Lidar‐Derived Snow Cover of Alpine Glaciers

Snow deposition and redistribution are major drivers of snow cover dynamics in mountainous terrain and contribute to the mass balance of alpine glaciers. The quantitative understanding of inhomogeneous snow distribution in mountains has recently benefited from advances in measuring technologies, such as airborne laser scanning (ALS). This contribution further advances the quantitative understanding of snow distribution by analysing the areas of maximum surface elevation changes in a mountain catchment with large and small glaciers. Using multi‐annual ALS observations, we found extreme surface elevation changes on rather thin borders along the glacier margins. While snow depth distribution patterns in less extreme terrain have presented high inter‐annual persistence, there is little persistence of those extreme glacier accumulations between winters. We therefore interpret the lack of persistence as the result of a predominance of gravity‐driven redistribution, which has an inherently higher random component because it does not occur with all conditions in all winters. In highly crevassed zones, the lidar‐derived surface elevation changes are caused by a complex interaction of ice flux divergence, the propagation of crevasses and snow accumulation. In general, the relative contribution of gravitational mass transport to glacier snow cover volume was found to decrease for glaciers larger than 5 km² in the investigated region. We therefore suggest that extreme accumulations caused by gravitational snow transport play a significant role in the glacier mass balance of small to medium‐size glaciers and that they may be successfully parameterized by simple mass redistribution algorithms, which have been presented in the literature.     

Vertical differentiation of land cover in the central Himalayas

Characterized by obvious altitudinal variation, habitat complexity, and diversity in land cover, the Mt. Qomolangma region within the central Himalayas is one of the most sensitive areas to climate change in the world. At the same time, because the Mt. Qomolangma region possesses the most complete natural vertical spectrum in the world, it is also an ideal place to study the vertical structure of alpine land cover. In this study, land cover data for 2010 along with digital elevation model data were used to define three methods for dividing the northern and southern slopes in the Mt. Qomolangma region, i.e., the ridgeline method, the sample transect method, and the sector method. The altitudinal distributions of different land cover types were then investigated for both the northern and southern slopes of the Mt. Qomolangma region by using the above three division methods along with Arc GIS and MATLAB tools. The results indicate that the land cover in the study region was characterized by obviously vertical zonation with the south-six and north-four pattern of vertical spectrum that reflected both the natural vertical structure of vegetation and the effects of human activities. From low to high elevation, the main land cover types were forests, grasslands, sparse vegetation, bare land, and glacier/snow cover. The compositions and distributions of land cover types differed significantly between the northern and southern slopes; the southern slope exhibited more complex land cover distributions with wider elevation ranges than the northern slope. The area proportion of each land cover type also varied with elevation. Accordingly, the vertical distribution patterns of different land cover types on the southern and northern slopes could be divided into four categories, with glaciers/snow cover, sparse vegetation, and grasslands conforming to unimodal distributions. The distribution of bare land followed a unimodal pattern on the southern slope but a bimodal pattern on the northern slope. Finally, the use of different slope division methods produced similar vertical belt structures on the southern slope but different ones on the northern slope. Among the three division methods, the sector method was better to reflect the natural distribution pattern of land cover.     

祁连山西段冰川积雪中大气粉尘沉积特征

基于2012 年夏季野外考察、微粒粒度测试和扫描电镜(SEM-EDX) 微观形貌观测研究, 对位于我国青藏高原东北缘的祁连山西段典型极大陆型冰川区老虎沟12 号冰川、野牛沟十一冰川积雪中大气粉尘沉积进行了分析研究。两冰川区积雪中微粒的平均质量浓度分别是3461 μg/kg、2876 μg/kg, 年均沉积通量分别是207.6 μg/cm²、143.8 μg/cm²。将本研究区与其他区域冰川积雪中粉尘浓度对比研究表明, 冰川受周边粉尘源区影响较大。雪坑微粒浓度剖面和离子相关性分析表明, 祁连山西段冰川积雪中污化层富含亚洲粉尘的富Ca²⁺、Na⁺矿物;微粒体积-粒径分布众数介于3~22 μm, 两冰川区的粒径众数分别为12.6 μm和12 μm, 粒径分布均显示了单结构模式, 同时反映了祁连山冰川区与毗邻的天山地区雪冰中粉尘粒径分布模式的相似性和粒径众数的差异性。通过SEM-EDX对粉尘颗粒的微观结构研究发现, 颗粒绝大多数为形貌不规则的矿物粉尘颗粒, 和很少数量的飞灰颗粒等。同时, 对粉尘来源结合Sr-Nd同位素测定和气团后向轨迹分析进行验证, 认为位于研究区北边的巴丹吉林沙漠是祁连山12号冰川区粉尘最可能的源区。     

MODIS observed snow cover variations in the Aksu River Basin,Northwest China

A major proportion of discharge in the Aksu River is contributed from snow-and glacier-melt water.It is therefore essential to understand the cryospheric dynamics in this area for water resource management.The MODIS MOD10A2 remotesensing database from March 2000 to December 2012 was selected to analyze snow cover changes.Snow cover varied significantly on a temporal and spatial scale for the basin.The difference of the maximum and minimum Snow Cover Fraction(SCF)in winter exceeded 70%.On average for annual cycle,the characteristic of SCF is that it reached the highest value of 53.2%in January and lowest value of 14.7%in July and the distributions of SCF along with elevation is an obvious difference between the range of 3,000 m below and 3,000 m above.The fluctuation of annual average snow cover is strong which shows that the spring snow cover was on the trend of increasing because of decreasing temperatures for the period of 2000-2012.However,temperature in April increased significantly which lead to more snowmelt and a decrease of snow cover.Thus,more attention is needed for flooding in this region due to strong melting of snow.     

中国天山西部季节性森林积雪物理特性

积雪特殊的物理特性对冰雪水文过程、积雪生态系统、不同尺度的气候系统有重要影响。目前对林下积雪物理特性缺乏系统性研究,因此对天山雪岭云杉林下季节性积雪深度、沉降速率、密度和含水率进行观测分析。结果表明：林下积雪深度小于开阔地;林下积雪沉降速率和新雪密实化率小于开阔地,且稳定期沉降速率小于融雪期。稳定期林下积雪密度小于开阔地,林下雪层密度最大值位于中粒雪层,开阔地则位于粗粒雪层;融雪期则全层密度趋于一致。稳定期林下雪层含水率随深度递减,开阔地雪层最大值出现粗粒雪层;融雪期雪层汗水峰值出现在细粒雪层,新雪层最小,林下雪层由细粒雪层到深霜层始终呈减小趋势,开阔地雪层由细粒雪层至中粒雪层逐渐减小,粗粒雪层至深霜层逐渐增大;稳定期雪层含水率日变化随深度的递减逐渐减小,开阔地大于林下;开阔地的新雪层和细粒雪层含水率的日变化大于林下,粗粒雪层到深霜层则小于林下。     

Sub-regional snow cover distribution across the southern Appalachian Mountains

Abstract

Snowfall in the Southern Appalachian Mountain region of the eastern US is characterized by much spatiotemporal variability. Annual snowfall totals vary by up to 75 cm, and variations in snowfall intensity can lead to large differences in the local snowfall distribution. Research has shown that the synoptic pattern associated with the snowfall strongly influences the regional-scale distribution of snow cover. However, topographic variability results in locally complex snow cover patterns that are not well understood or documented. In this study, we characterize the snow covered area (SCA) and fractional snow cover associated with different synoptic patterns in 14 individual sub-regions. We analyze 63 snow events using Moderate-resolution Imaging Spectroradiometer standard snow cover products to ascertain both qualitative and quantitative differences in snow cover across sub-regions. Among sub-regions, there is significant variation in the snow cover pattern from individual synoptic classes. Furthermore, the percent SCA follows the regional snowfall climatology, and sub-regions with the highest elevations and northerly latitudes exhibit the greatest variability. Results of the sub-regional analysis provide valuable guidance to forecasters by contributing a deeper understanding of local snow cover patterns and their relationship to synoptic-scale circulation features.