哈尔滨市典型森林对雪水量的影响研究

森林对于雪水资源的调控具有重要意义,目前在东北地区森林对雪水文生态过程的影响仍不明确。2012—2013年,以哈尔滨市试验林场为研究区域,选择区域内具有代表性的3种森林类型为研究对象,通过定期观测林内外的雪深、雪密度和雪水量,对不同森林及各雪水量的影响进行研究。结果表明:2013年3月9日为积雪量最大期,樟子松林和落叶松林的积雪深度分别比无林地的小20.1%(5.98 cm)和13.7%(4.08 cm);不同森林的地表雪密度与环境温度皆呈显著正相关,樟子松林和落叶松林的地表雪密度要小于白桦林和无林地的;樟子松林、落叶松林和白桦林的最大雪水量要分别比无林地的小32.9%、14.2%和7.0%,在融雪期间,樟子松林、落叶松林和白桦林的平均融雪速率分别为无林地的39%(1.21 mm/d)、70%(2.18 mm/d)和93%(2.89 mm/d),樟子松林的地表积雪比落叶松林、白桦林和无林地的要延迟10天完全融化;在整个冬季期间樟子松林、落叶松林和白桦林的累积截雪量分别为18.4 mm、7.95 mm和3.89 mm。综上所述,樟子松林对于降雪再分配的调控作用具有显著的影响,其稠密的冠层结构是重要的影响因素。

屋面材料对雪层持水量及积雪滑落的影响

为揭示屋面材料对屋面积雪滑落的影响规律,考虑混凝土、钢、膜与玻璃等常用屋面材料,对不同材料屋面上雪层的最大持水量及屋面-雪层剪切强度展开试验研究,并引入度日模型,建立屋面积雪滑落的判定方法,分析了屋面材料对屋面积雪滑落的影响。结果表明屋面积雪的最大持水量随屋面材料粗糙度的增大而增大;除玻璃外,屋面积雪滑落的临界温度也随屋面材料粗糙度的增大而增大。研究的结果为进一步探索屋面积雪滑落的机理提供重要参考依据。

春季积雪融化过程的模拟研究

为深入研究东北积雪在融化期融化速率、融雪水量及产流时积雪厚度的影响因素,选取积雪厚度、积雪密度、风速、温度4个因素,利用正交试验设计方法,采用室内模拟融化试验,对试验数据进行方差分析与线性回归分析,得出积雪在不同厚度、密度、不同风速、温度条件下,积雪融化速率、产流时刻雪深及融雪水量的影响规律。结果表明:在整个试验过程中,对积雪融化速率的影响为:风速 】积雪密度 】温度 】积雪厚度。温度是积雪融化外部能量的来源,温度越高,融化速率越快;风速通过运输外部能量和加速水分运移影响着积雪融化的快慢;自身的厚度与密度是积雪内部结构的基础,影响着水分在雪层间的储存与运移,从而影响积雪的融化速率。积雪融化前的初始厚度与密度对积雪产流时积雪厚度影响较大,风速与温度只影响产流时间长短,不影响产流时积雪厚度。积雪厚度、密度影响积雪融雪水量的多少,风速与温度只影响融化快慢,对融雪水量没有影响。

1960—2014年辽宁省冬季降水极值变化分析

利用1960—2015年辽宁省50个常规气象站和加密站的降水观测资料,对辽宁省冬季降水极值变化特征进行了分析。结果表明:1960—2014年辽宁省康平和义县地区冬季年平均极端降水频次最多,为1.7次;辽中地区冬季年平均极端降水频次最少,为1.0次。辽宁省冬季极端降水频次呈较明显的上升趋势并存在11、7 a和3 a的变化周期。辽宁省冬季区域性小雪、中雪、大雪及暴雪量级降水过程的年总频次极大值分别为32、8、4次和2次。辽宁省冬季连续性降水过程发生频次呈自东向西减少的空间分布特征,清原地区年平均连续性降水发生频次最大,达9次/10 a。单站冬季降水总量极值为95.0 mm。单站纯雪过程降水量及24 h、6 h、1 h降水量极值分别为42.0 mm、34.5 mm、20.0 mm和6.9 mm。

Potential predictability of Eurasian spring snow water equivalent in IAP AGCM4 hindcasts

The potential predictability and skill of Eurasian spring snow water equivalent(SWE)are explored by using a suite of ensemble hindcast experiments with the fourth-generation IAP AGCM(IAP AGCM4)and observations for the period 1982–2012.IAP AGCM4 is generally capable of reproducing the spatial distribution of Eurasian spring SWE;nevertheless,the model overestimates the SWE over Eurasia,possibly because of positive precipitation biases in wintertime.IAP AGCM4 can successfully capture the long-term trend and leading pattern of Eurasian spring SWE.Additionally,the spring SWE anomalies are generally predictable in many regions over Eurasia,especially at high latitudes;moreover,IAP AGCM4 exhibits a remarkable prediction skill for spring SWE anomalies over Eurasia in many years during 1982 to 2012.In order to reveal the relative impacts of SST anomalies and atmospheric initial conditions on the seasonal predictability of Eurasian spring SWE,two additional sets of experiments are carried out.Overall,atmospheric initial anomalies have a dominant role,though the impact of SSTs is not negligible.This study highlights the importance of atmospheric initialization in seasonal climate forecasts of spring SWE anomalies,especially at high latitudes.

Assessment of Snow Cover Vulnerability over the Qinghai-Tibetan Plateau

By using daily air temperature and precipitation data, and the weather phenomena data of daily snowfall from 98 meteorological stations over the Qinghai-Tibetan Plateau （QTP）, this paper performs an ＂at-risk＂ evaluation on snowfall and accumulated snow over the QTP under current climate situation and future climate warming condition. When rainfall, snowfall, or accumulated snow weather phenomena occur, critical values are determined based on dally air temperature and precipitation for current climate conditions. Air temperature of 0 ℃ is defined as the critical value of temperature for rainfall or snowfall, while 0 ℃ air temperature and 4.0 mm （autumn） or 3.0 mm （spring） snowfall amounts are defined as the critical values for accumulated snowfall. Analyses based on the above critical values disclose that under current climate condition, stations with ＂at-risk＂ accumulated snow account for 33% and 36% of all stations, and the ＂at-risk＂ snowfall stations reach 78% and 81% in autumn and spring, respectively. Spatially, most stations with ＂at-risk＂ accumulated snow are located on the southern and eastern edge of the QTP, and stations with ＂at-risk＂ snowfall are also apparent at the northern edge. If the air temperature increases by 2.5 ℃ in 2050, only the snowfall at a few ＂at-risk＂ snowfall stations will transform into rainfall, while most ＂at-risk＂ accumulated snow stations will face the problem that snowfall is hardly accumulated. Additionally, most stations will become ＂at-risk＂ accumulated snow stations, indicating that both the snow depth and the snow cover duration will decline in most areas of the QTP, including a delay of the start date and an advancing of the end date of snow cover.

Discussion of Influences on Snow Water Equivalent at Utah Snow Courses

Snow data collection systems in the western United States were originally designed to forecast water supply and may be subject to several sources of bias. In addition to climate change and weather modification effects, site-specific effects may be introduced from vegetation changes, site physical changes, measurement technique, and sensor changes. This paper examines changes in Utah＇s snowpack conditions over the past decade compared with all previous measurement years, focusing on the 15 snow courses with the longest observational record within the state of Utah. Although patterns in snowpack data consistent with those that would be expected due to temperature h as greater declines at lower elevations and latitudes--were not identified, snow water equivalent decreased at sites with significant increases in vegetation coverage. Additionally, we provide a list of 22 snow courses in Utah that are best-suited for long-term climate analysis.

Changes in Climatic Factors and Extreme Climate Events in Northeast China during 1961-2010

This study focuses on examining the characteristics of climate factors and extreme climate events in Northeast China during 1961- 2010 by using daily data from 104 stations, including surface air temperature, precipitation, wind speed, sunshine duration, and snow depth. Results show that annual mean temperature increased at a significant rate of 0.35℃ per decade, most notably in the Lesser Khingan Mountains and in winter. Annual rainfall had no obvious linear trend, while rainy days had a significant decreasing trend. So, the rain intensity increased. High-temperature days had a weak increasing trend, and low-temperature days and cold wave showed significant decreasing trends with rates of 3.9 d per decade and -0.64 times per decade, respectively. Frequency and spatial scope of low-temperature hazard reduced significantly. Warm days and warm nights significantly increased at 1.0 and 2.4 d per decade, while cold days and cold nights decreased significantly at -1.8 and -4.1 d per decade, respectively. The nighttime warming rate was much higher than that for daytime, indicating that nighttime warming had a greater contribution to the overall warming trend than daytime warming. The annual mean wind speed, gale days, and sunshine duration had significant decreasing trends at rates of-0.21 m s-1 per decade, -4.0 d per decade and -43.3 h per decade, respectively. The snow cover onset dates postponed at a rate of 1.2 d per decade, and the snow cover end date advanced at 1.5 d per decade, which leads to shorter snow cover duration by -2.7 d per decade. Meanwhile, the maximum snow depth decreased at -0.52 cm per decade. In addition, the snow cover duration shows a higher correlation with precipitation than with temperature, which suggests that precipitation plays a more important role in maintaining snow cover duration than temperature.

Asymptotic Solution for Coupled Heat and Mass Transfer During the Solidification of High Water Content Materials

This paper focuses on obtaining an asymptotic solution for coupled heat and mass transfer problem during the solidification of high water content materials. It is found that a complicated function involved in governing equations can be approached by Taylor polynomials unlimitedly, which leads to the simplification of governing equations. The unknown functions involved in governing equations can then be approximated by Chebyshev polynomials. The coefficients of Chebyshev polynomials are determined and an asymptotic solution is obtained. With the asymptotic solution, the dehydration and freezing fronts of materials are evaluated easily, and are consistent with numerical results obtained by using an explicit finite difference method.

Review of snow water equivalent microwave remote sensing

Accurate quantitative global scale snow water equivalent information is crucial for meteorology, hydrology, water cycle and global change studies, and is of great importance for snow melt-runoff forecast, water resources management and flood control. With land surface process model and snow process model, the snow water equivalent can be simulated with certain accuracy, with the forcing data as input. However, the snow water equivalent simulated using the snow process models has large uncertainties spatially and temporally, and it may be far from the needs of practical applications. Thus, the large scale snow water equivalent information is mainly from remote sensing. Beginning with the launch of Nimbus-7 satellite, the research on microwave snow water equivalent remote sensing has developed for more than 30 years, researchers have made progress in many aspects, including the electromagnetic scattering and emission modeling, ground and airborne experiments, and inversion algorithms for future global high resolution snow water equivalent remote sensing program. In this paper, the research and progress in the aspects of electromagnetic scattering/emission modeling over snow covered terrain and snow water equivalent inversion algorithm will be summarized.

Spatial distribution of 10m firn temperature in the Antarctic Ice Sheet

A database of Antarctic 10 m firn temperature was constructed using available borehole temperature measurements with data quality control to extend knowledge of Antarctic climate. Slopes from a high-resolution digital elevation model and the main ice divide were used to delineate main drainage sectors across Antarctica. In each drainage sector, a quantitative relationship between temperature and latitude, longitude and altitude was established using available tim temperature data. Quantitative relationships incorporating other factors affecting Antarctic air temperature such as atmospheric circulation and small-scale to- pography were used to derive a 10-km resolution grid map of surface temperature. The resulting temperature patterns presented a reasonable depiction of both large and small-scale variations in Antarctic 10 m firn temperature. This map is useful for many spatial variation studies, Antarctic ice sheet models, and comparison with satellite-derived temperature data and outputs of atmospheric general circulation models.