武威市初、终霜日气候特征

为了因地制宜,合理调整种植结构和布局,有效利用农业气候资源。利用1961—2014年武威市4个气象站点初、终霜日(最低地温≤0℃)观测资料,采用现代气候诊断分析方法,系统分析了该市年初、终霜日的时空变化特征。结果表明:受海拔高度、地形地势以及植被覆盖情况的影响,在空间分布上,武威市初霜日为山区早于荒漠区早于绿洲平原区,终霜日为山区晚于荒漠区晚于绿洲平原区,各地初、终霜日存在一定的异常性,正常初、终霜日均在60%左右,对农业生产造成危害的偏早和特早初霜日、偏晚和特晚终霜日的概率均在20%左右。在时间变化上,武威市初霜日呈显著推迟趋势,终霜日呈显著提早趋势,霜期呈显著缩短趋势,终霜日提早的幅度比初霜日推迟的幅度更大。初霜日和终霜日的时间序列均分别存在着8~10年和9~11年的准周期变化。初霜日在1998年发生了气候突变,终霜日在1996年发生了气候突变。     

InSAR技术在多年冻土区形变监测的应用

作为大地测量的一种新兴空间技术,合成孔径雷达干涉（synthetic aperture radar interferometry, InSAR）具有全天时、高精度、大范围和速度快的优点,逐渐被应用于多年冻土区地表形变监测中。通过综述多年冻土形变原理及InSAR监测多年冻土形变的应用实例,研究表明：在气候变暖的背景下,多年冻土区地表年际形变以下沉为主,多年冻土上限附近地下冰含量的大小是影响年际形变量的主要因素;活动层内土壤含水量影响着地表季节形变量的大小,不同类型多年冻土区的地表年际形变量和季节形变量存在着较大的差异。研究还表明,不同波长的SAR产品在不同类型多年冻土区的适用性不同,下垫面特征对利用InSAR获取地表形变量有较大影响,L波段的SAR数据在植被覆盖度较好的区域有更好的效果。由于InSAR的失相干问题,加之目前还缺少长时间、多类型、高频率的实测形变结果作为验证和标校数据,获取准确且连续的大范围形变数据较为困难。针对目前寒区研究需求,布设野外长期观测站点,建立适用于不同多年冻土区的地表形变反演算法,构建具有较高精度和较高时空分辨率的地表形变数据集具有重要的实践和科学意义。     

Frost susceptibility of soils——A confusing concept that can misguide geotechnical design in cold regions

Frost susceptibility is a concept widely used in cold region geotechnical design, to quantify the capacity of a soil in generating frost heave and frost damage. The laboratory test used to verify frost susceptibility of a soil is based on the measurement of frost heave generated in the soil under specific conditions. In reality this concept is, however, more related to the soil's potential to thaw weakening than to frost heave. Recent experimental studies show that frost non-susceptible soils like clean sand and clean gavel can also generate much ice segregation and frost heave if the conditions are favourable, hence challenging the usefulness and suitability of soil classification based on frost susceptibility. It is further shown that the concept is not suitable for design scenarios where frost heave itself is a serious hazard, such as in high-speed rail embankments.     

1961—2017年北疆初终霜日及霜期时空变化特征

利用1961—2017年北疆37个地面气象站逐日最低气温观测资料,结合常规气象统计方法,分析北疆地区初、终霜日和霜期的时空演变特征.结果表明:(1)北疆平均初霜日以2.2 d·(10a)-1速率推迟;平均终霜日以1.7 d·(10a)-1速率提前;平均霜期以3.9 d·(10a)-1速率缩短;初、终霜日和霜期的主周期均...     

Numerical analysis of frost effects in porous media. Benefits and limits of the finite element poroelasticity formulation

The aim of this paper is to analyse the performance of a finite element formulation usable for predicting the mechanical consequences of frost effects on porous media. It considers the characteristics of porous media and how the frost action can be assessed. The problem is then separated into two parts: thermal and poromechanical calculations. The constitutive equations developed in the framework of poromechanics are presented and the implementation in a usual finite element poroelasticity formulation based on Zuber's method is adopted. An analysis of the time‐step influence on the convergence rate is given and leads us to propose a simple method in order to obtain objectivity of the finite element response and avoid over‐long calculations. Frost effect simulations are carried out on real porous media (two fired clays) as a case study. Although the experimental behaviour of the porous media subjected to frost action is in accordance with some observations, the calculated strains appear to be overestimated compared with measurements. The problem could be largely attributable to the difficulty of assessing permeability evolution during frost development. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of snow and soil frost melting on the concentrations of suspended solids and phosphorus in two rural watersheds in Western Finland

Hydrological processes are known to have a considerable effect on nutrient transport from agricultural land to watercourses. In cold temperate regions peak discharges are caused not only by storm conditions but also by melting of snow and frost. The objective of this work was to investigate the effects of snow and frost melt on concentrations of phosphorus and suspended solids. The samples were taken using flowweighted automatic sampling techniques from two agricultural drainage basins. During the beginning of the snowmelt period the concentration of suspended solids was rather low by comparison with the total phosphorus concentration and the discharge. The different behaviour compared with the relationships found during storm conditions was probably caused by continuous extraction of the soil surface by low ionic concentration melt water, and to some extent by leaching from plant residues. The gradual decrease of total phosphorus concentration during the frost thawing period could be attributed to the gradually increasing proportion of the subsurface and ground water discharge in the runoff.     

湖北省钟祥第四纪冰缘融冻构造的发现及其意义

笔者于1986年在钟祥首次发现了第四纪地层间的冰缘融冻构造——古冰楔与揉皱,其时代为早更新世末期—中更新世初期。它的发现不仅为建立本区第四纪地层层序,而且为确定更新世北方冰缘冻土的南界和研究长江中下游更新世古气候环境的演变提供了重要的科学依据。