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排序方式: 共有396条查询结果,搜索用时 15 毫秒
71.
中国西部积雪对我国汛期降水的影响 总被引:19,自引:6,他引:19
本文利用台站及卫星资料建立了中国西部积雪30年逐月时间序列。该序列是目前资料时间最长、最好的序列,为研究该区积雪月际和年际变化及其影响提供了较可靠的依据。中国西部冬春积雪对我国汛期降水的影响平均为负相关趋势,与6月降水的相关分布较有规律,冬春多(少),其它地区6月降水偏多(少)。我国西部多(少)雪对6月从份500hPa高度的变化是:高原北边高纬高度降低(升高)及副热地区升高(降低),有(不)利于高 相似文献
72.
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
73.
74.
The Summer Surface Energy Balance of the High Antarctic Plateau 总被引:1,自引:0,他引:1
Dirk?van?AsEmail author Michiel?van?den?Broeke Carleen?Reijmer Roderik?van?de?Wal 《Boundary-Layer Meteorology》2005,115(2):289-317
The summertime surface energy balance (SEB) at Kohnen station, situated on the high Antarctic plateau (75°00′ S, 0°04′ E,
2892m above sea level) is presented for the period of 8 January to 9 February 2002. Shortwave and longwave radiation fluxes
were measured directly; the former was corrected for problems associated with the cosine response of the instrument. Sensible
and latent heat fluxes were calculated using the bulk method, and eddy-correlation measurements and the modified Bowen ratio
method were used to verify these calculated fluxes. The calculated sub-surface heat flux was checked by comparing calculated
to measured snow temperatures. Uncertainties in the measurements and energy-balance calculations are discussed.
The general meteorological conditions were not extraordinary during the period of the experiment, with a mean 2-m air temperature
of −27.5°C, specific humidity of 0.52×10−3kg kg−1 and wind speed of 4.1ms−1. The experiment covered the transition period from Antarctic summer (positive net radiation) to winter (negative net radiation),
and as a result the period mean net radiation, sensible heat, latent heat and sub-surface heat fluxes were small with values
of −1.1, 0.0, −1.0 and 0.7 Wm−2, respectively. Daily mean net radiation peaked on cloudy days (16 Wm−2) and was negative on clear-sky days (minimum of −19 W m−2). Daily mean sensible heat flux ranged from −8 to +10 Wm−2, latent heat flux from −4 to 0 Wm−2 and sub-surface heat flux from −8 to +7 Wm−2. 相似文献
75.
青藏高原积雪的分布特征及其对地面反照率的影响 总被引:7,自引:3,他引:7
通过对1983年7月至1990年6月青藏高原主体58个格点积雪资料进行EOF分析发现,青藏高原主体积雪分布以西部兴都库什山脉。天山山脉以及南部喜马拉雅山脉为主;高原中部唐古拉山脉、北部昆仑山脉和东部巴颜喀拉山脉的积雪相对较少,青藏高原西部、南部的积雪变化与中部、北部和东部的积雪变化趋势存在反位相关系。另外,本文还对积雪对高原地面反照率的影响作了简单分析。 相似文献
76.
新疆积雪对气候变暖的响应 总被引:38,自引:1,他引:38
积雪对全球变暖的响应是当前正在争论的问题。文中通过地面气象台站和 SMMR微波卫星遥感两种积雪资料所建立的两个独立的积雪序列的一致性 ,证明前者在表现新疆积雪长期变化能力方面具有可靠性。阐明了积雪年际变化特征及其与冬季气温和降水量年际波动的关系 ,检验了积雪长期变化趋势。研究表明 ,虽然近 5 0 a来新疆冬季变暖十分显著 ,尤其 2 0世纪 90年代为最温暖的时期 ,但是积雪并未出现持续减少的现象 ;积雪长期变化表现为显著的年际波动过程叠加在长期缓慢的增加趋势之上。积雪年际波动是冬季降水量和气温两者年际波动共同作用的结果 ;冬季气温和降雪量变化受不同的欧亚环流振荡所控制 ;积雪增加趋势与降雪量趋势相一致 ,这可能是由于全球变暖导致海洋蒸发量增加 ,以及在寒冷干燥气候下积雪对降雪量变化更为敏感的缘故。 相似文献
77.
Snow interception is a crucial hydrological process in cold regions needleleaf forests, but is rarely measured directly. Indirect estimates of snow interception can be made by measuring the difference in the increase in snow accumulation between the forest floor and a nearby clearing over the course of a storm. Pairs of automatic weather stations with acoustic snow depth sensors provide an opportunity to estimate this, if snow density can be estimated reliably. Three approaches for estimating fresh snow density were investigated: weighted post-storm density increments from the physically based Snobal model, fresh snow density estimated empirically from air temperature (Hedstrom, N. R., et al. [1998]. Hydrological Processes, 12, 1611–1625), and fresh snow density estimated empirically from air temperature and wind speed (Jordan, R. E., et al. [1999]. Journal of Geophysical Research, 104, 7785–7806). Automated snow depth observations from adjacent forest and clearing sites and estimated snow densities were used to determine snowstorm snow interception in a subalpine forest in the Canadian Rockies, Alberta, Canada. Then the estimated snow interception and measured interception information from a weighed, suspended tree and a time-lapse camera were assimilated into a model, which was created using the Cold Regions Hydrological Modelling platform (CRHM), using Ensemble Kalman Filter or a simple rule-based direct insertion method. Interception determined using density estimates from the Hedstrom-Pomeroy fresh snow density equation agreed best with observations. Assimilating snow interception information from automatic snow depth measurements improved modelled snow interception timing by 7% and magnitude by 13%, compared to an open loop simulation driven by a numerical weather model; its accuracy was close to that simulated using locally observed meteorological data. Assimilation of tree-measured snow interception improved the snow interception simulation timing and magnitude by 18 and 19%, respectively. Time-lapse camera snow interception information assimilation improved the snow interception simulation timing by 32% and magnitude by 7%. The benefits of assimilation were greatly influenced by assimilation frequency and quality of the forcing data. 相似文献
78.
Snow cover patterns in a 9.4 km2 basin in the Austrian Alps are examined during spring and summer 1989. Digital mono-plotting from oblique aerophotographs is used for mapping. on the basis of a square grid with 25 m spacing, snow cover as mapped during nine surveys is analysed as a function of elevation and slope. During winter conditions the snow cover is found to be much better related to these terrain features than during the late ablation period. 相似文献
79.
Hydrological and hydrochemical parameters for two mountain basins are presented and compared. The analysis focuses on the hydrology during the winter, the cumulative outflow of sulphate and nitrate from the basin and a mass balance. An integrated model for the simulation of the amount and quality of snowmelt from seasonal snow cover is briefly described. The possible application of the model to other basins is considered. 相似文献
80.