Preliminary spectral characterization of snow in a high altitude tropical glacier and potential effects of impurities in snow on albedo of tropical glaciers     

Jean Emmanuel Sicart  Yves Arnaud 《水文研究》2007,21(26):3642-3644

This paper presents some preliminary measurements of snow spectral reflectance on the tropical Bolivian Zongo glacier. Measurements show a correct agreement with theoretical spectral albedo of pure snow in the near infrared region, but lower values in the visible region (by 10–20%) probably due to aerosols contained in snow. Impurity contents ranged from 10 to 100 ppmw in one‐week‐old snow collected from the Zongo glacier, but measurements are scarce. Large amounts of snowfall partly compensate the proximity of dust sources in mid‐latitude glaciers, whereas on outer‐tropical glaciers precipitations are not abundant and are very seasonal, and sources of aerosols are proximate. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Detecting Arctic snow and ice cover with FY-1D global data     

References： 《极地研究(英文版)》2007,18(1):54-62

Chinese meteorological satellite FY-1D can obtain global data from four spectral channels which include visible channel(0.58-0.68 μm) and infrared channels(0.84-0.89 μm,10.3-11.3 μm,11.5-12.5 μm).2366 snow and ice samples,2024 cloud samples,1602 land samples and 1648 water samples were selected randomly from Arctic imageries.Land and water can be detected by spectral features.Snow-ice and cloud can be classified by textural features.The classifier is Bayes classifier.By synthesizing five d ays classifying result of Arctic snow and ice cover area,complete Arctic snow and ice cover area can be obtained.The result agrees with NOAA/NESDIS IMS products up to 70%.  相似文献   

Estimation of net accumulation rate at a Patagonian glacier by ice core analyses using snow algae     

Shiro Kohshima  Nozomu Takeuchi  Jun Uetake  Takayuki Shiraiwa  Ryu Uemura  Naohiro Yoshida  Sumito Matoba  Maria Angelica Godoi 《Global and Planetary Change》2007,59(1-4):236

Snow algae in a 45.97-m-long ice core from the Tyndall Glacier (50°59′05″S, 73°31′12″W, 1756 m a.s.l.) in the Southern Patagonian Icefield were examined for potential use in ice core dating and estimation of the net accumulation rate. The core was subjected to visual stratigraphic observation and bulk density measurements in the field, and later to analyses of snow algal biomass, water isotopes (¹⁸O, D), and major dissolved ions. The ice core contained many algal cells that belonged to two species of snow algae growing in the snow near the surface: Chloromonas sp. and an unknown green algal species. Algal biomass and major dissolved ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, SO₄²⁻) exhibited rapid decreases in the upper 3 m, probably owing to melt water elution and/or decomposition of algal cells. However, seasonal cycles were still found for the snow algal biomass, ¹⁸O, D-excess, and major ions, although the amplitudes of the cycles decreased with depth. Supposing that the layers with almost no snow algae were the winter layers without the melt water essential to algal growth, we estimated that the net accumulation rate at this location was 12.9 m a^− 1 from winter 1998 to winter 1999, and 5.1 m from the beginning of winter to December 1999. These estimates are similar to the values estimated from the peaks of ¹⁸O (17.8 m a^− 1 from summer 1998 to summer 1999 and 11.0 m from summer to December 1999) and those of D-excess (14.7 m a^− 1 from fall 1998 to fall 1999 and 8.6 m a^− 1 from fall to December 1999). These values are much higher than those obtained by past ice core studies in Patagonia, but are of the same order of magnitude as those predicted from various observations at ablation areas of Patagonian glaciers.  相似文献   

东南极冰盖内陆深处几个雪坑离子浓度的初步研究   总被引：1，自引：1，他引：0  

任贾文  孙俊英  秦大河  效存德 《冰川冻土》2004,26(2):135-141

对南极中山站-Dome A断面距海岸800～1 100 km(海拔2 850～3 760 m)的内陆深处3个雪坑进行了雪层剖面观测和雪样化学分析.氧同位素、可见层位特征与主要阴、阳离子浓度的剖面对比分析表明, 同位素季节变化信号不明显, 而太阳辐射冰壳与某些离子(如Na 、 Cl-等)浓度变化有较好的对应.研究区域主要的几种离子如Na 、 Cl-和SO2-4等与东南极内陆其它区域雪坑中的相似, 但NO-3和NH 4有较大差异.在高原中心区域, NO-3沉积后很大部分又逸散返回大气, 因而雪层中平均浓度很低但表面处的浓度却异常地高.在海拔2 850 m处, 各种离子的浓度随深度增加而增加, 在海拔3 750 m处则为相反趋势, 在海拔3 380 m处趋势不明显.如果离子沉降速率保持不变, 这种特征意味着近20 a来降雪积累速率在高原中心区域为减少趋势, 在海拔较低的区域则为增加趋势.在所有雪坑中, Na 和Cl-具有非常好的正相关性, Cl-/Na 为1.24～1.61, 略高于海水中的值(1.168), 说明Cl-虽然主要来源与于海盐, 但仍有一小部分为其它来源.非海盐SO2-4在不同雪坑中显示出不同特征, 对其是否能指示火山喷发等问题还有待于进一步探讨.  相似文献   

不同积雪深度下地面温度与雪面温度的相关     

王秀琴  卢新玉  王金风 《气象科技》2013,41(6):1068-1072

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   

杭州市典型雨转雪天气成因及预报模型   总被引：1，自引：0，他引：1  

李进  陈勇明  毛则剑  周娟 《气象科技》2020,48(3):396-405

利用2008—2018年的NCEP(1°×1°)再分析资料、常规气象观测资料和降雪加密观测资料,选出杭州地区10次典型的雨转雪天气过程,从大尺度环流背景和动力、水汽以及热力因子等物理量场结构方面展开研究,最终得出杭州冬季典型雨转雪天气的预报模型:①大尺度环流配置需满足能为雨转雪天气的形成提供有利的水汽、动力抬升以及中低层上暖下冷的逆温或等温层结条件;②水汽和动力因子等物理量须满足产生纯雪的特定条件;③杭州温度层结须为T_(2m)≤1.5℃、T_(925)≤-4.0℃、T_(850)≤0℃、T_(700)≤-1.0℃和T_(500)≤-10.0℃。此外,进一步补充了杭州可能产生大雪甚至暴雪量级降雪的特定条件。最终选取2019年初的2次典型降水过程进行预报回报检验。  相似文献   

An empirical formula to compute snow cover fraction in GCMs   总被引：10，自引：0，他引：10  

WU Tongwen  WU Guoxiong 《大气科学进展》2004,21(4):529-535

There exists great uncertainty in parameterizing snow cover fraction in most general circulation models (GCMs) using various empirical formulae, which has great influence on the performance of GCMs. This work reviews the commonly used relationships between region-averaged snow depth (or snow water equivalent) and snow cover extent (or fraction) and suggests a new empirical formula to compute snow cover fraction, which only depends on the domain-averaged snow depth, for GCMs with different horizontal resolution. The new empirical formula is deduced based on the 10-yr (1978-1987) 0.5°× 0.5° weekly snow depth data of the scanning multichannel microwave radiometer (SMMR) driven from the Nimbus-7 Satellite. Its validation to estimate snow cover for various GCM resolutions was tested using the climatology of NOAA satellite-observed snow cover.  相似文献   

Impact of vegetation feedback on the mid-Pliocene warm climate     

ZHANG Ran  JIANG Dabang 《大气科学进展》2014,31(6):1407-1416

Studying the vegetation feedback during warm periods of the past can lead to better understanding of those in the future.In this study,we conducted several simulations to analyze vegetation feedback during the mid-Pliocene warm period.The results indicate that the main features of vegetation change in the mid-Pliocene were a northward shift of needleleaf tree,an expansion of broadleaf tree and shrub,and a northward expansion of grass,as compared to the pre-industrial period.The global annual mean warming ratio caused by vegetation feedback was 12.1％,and this warming ratio was much larger in northern middle and high latitudes.The warming caused by vegetation change was directly related to the surface albedo change and was further amplified by snow/sea ice-albedo feedback.  相似文献   

一次华北气旋造成北京特大暴雪天气过程分析     

詹正杰  尹仔锋  乔林  赵玮  孙秀忠 《沙漠与绿洲气象(新疆气象)》2014,8(5):10-15

利用北京延庆站和海淀站风廓线产品、微波辐射计产品、北京市雷达产品(南郊和车道沟)、北京市58个称重雨量站观测资料、FY-2E卫星云图、常规气象资料综合分析2012年11月3到4日北京暴雪天气过程。分析表明：降水相态(雨、雪)由华北气旋的锋面性质和锋面位置决定;过程雨雪量由气旋的强度、持续时间和水汽通道维持时间决定;风廓线和微波辐射计产品资料在雨雪开始时间、雨雪相态转换方面有明显的指示性作用。  相似文献   

A Dipole Pattern of Summer Precipitation over Mid-high Latitude Asia and Related Snow Cover Anomalies in the Preceding Spring          下载免费PDF全文

HAN Jin-Ping  LIU Ge  XIN Yu-Fei 《大气和海洋科学快报》2014,(4):364-368

A dipole pattern of summer precipitation over the mid-high latitudes of Asia, which is characterized by opposing summer precipitation variations between the Mongolian and Northeast China （MNC） region and the West Siberian Plain （WSP）, is found to be clear and stable on both interdecadal and interannual scales during 1981- 2011. Spring snow cover anomalies over a small region within the WSP and the Heilongjiang River （HR） region are closely related to the variation of this dipole mode during the subsequent summer, and they can therefore be considered as forecasting factors. Our statistical results imply a potential process explaining the relationship between the spring snow anomalies and the summer rainfall dipole. Corresponding to the snow anomalies, Rossby waves propagate along a path from the WSP region, via the Mongolian Plateau, to the Stanovoy Range during summer. At the same time, Rossby-wave energy divergences and convergences along this path maintain and reinforce an anomalous cyclone and anticyclone pairing over the Asian continent, which is significantly linked to opposite summer precipitation anomalies between the MNC and WSP regions. Numerical experiments are need- ed to further confirm the above conjecture and demonstrate the detailed physical mechanisms linking the spring snow cover anomalies and summer precipitation dipole.  相似文献