共查询到20条相似文献，搜索用时 290 毫秒
1.
Permafrost Thaw Accelerates in Boreal Peatlands During Late-20th Century Climate Warming 总被引：7，自引：0，他引：7
Philip Camill 《Climatic change》2005,68(1-2):135-152
Permafrost covers 25% of the land surface in the northern hemisphere, where mean annual ground temperature is less than 0°C. A 1.4–5.8 °C warming by 2100 will likely change the sign of mean annual air and ground temperatures over much of the zones of sporadic and discontinuous permafrost in the northern hemisphere, causing widespread permafrost thaw. In this study, I examined rates of discontinuous permafrost thaw in the boreal peatlands of northern Manitoba, Canada, using a combination of tree-ring analyses to document thaw rates from 1941–1991 and direct measurements of permanent benchmarks established in 1995 and resurveyed in 2002. I used instrumented records of mean annual and seasonal air temperatures, mean winter snow depth, and duration of continuous snow pack from climate stations across northern Manitoba to analyze temporal and spatial trends in these variables and their potential impacts on thaw. Permafrost thaw in central Canadian peatlands has accelerated significantly since 1950, concurrent with a significant, late-20th-century average climate warming of +1.32 °C in this region. There were strong seasonal differences in warming in northern Manitoba, with highest rates of warming during winter (+1.39 °C to +1.66 °C) and spring (+0.56 °C to +0.78 °C) at southern climate stations where permafrost thaw was most rapid. Projecting current warming trends to year 2100, I show that trends for north-central Canada are in good agreement with general circulation models, which suggest a 4–8 °C warming at high latitudes. This magnitude of warming will begin to eliminate most of the present range of sporadic and discontinuous permafrost in central Canada by 2100. 相似文献
2.
Summary Using the methods of running means and integral difference curves, the monthly and annual air temperatures in upper parts of the Bulgarian mountains are studied. Data from seven stations are used, covering the period 1930–1989. Records of mean, minimum and maximum air temperature for January, April, July, and October are analysed. Periods of warming and cooling in separate months of the year are identified. In upper parts of Bulgaria during recent years, the temperature record has shown a trend towards warming in winter and cooling in summer. Mean annual temperatures were observed to decrease between 1962 and 1981.With 5 Figures 相似文献
3.
Hugh A. L. Henry 《Climatic change》2008,87(3-4):421-434
Changes to soil freezing dynamics with climate change can modify ecosystem carbon and nutrient losses. Soil freezing is influenced
strongly by both air temperature and insulation by the snowpack, and it has been hypothesized that winter climate warming
may lead to increased soil freezing as a result of reduced snowpack thickness. I used weather station data to explore the
relationships between winter air temperature, precipitation and soil freezing for 31 sites in Canada, ranging from the temperate
zone to the high Arctic. Inter-annual climate variation and associated soil temperature variation over the last 40 years were
examined and used to interpolate the effects of projected climate change on soil freezing dynamics within sites using linear
regression models. Annual soil freezing days declined with increasing mean winter air temperature despite decreases in snow
depth and cover, and reduced precipitation only increased annual soil freezing days in the warmest sites. Annual soil freeze–thaw
cycles increased in both warm and dry winters, although the effects of precipitation were strongest in sites that experience
low mean winter precipitation. Overall, it was projected that by 2050, changes in winter temperature will have a much stronger
effect on annual soil freezing days and freeze–thaw cycles than changes in total precipitation, with sites close to but below
freezing experiencing the largest changes in soil freezing days. These results reveal that experimental data relevant to the
effects of climate changes on soil freezing dynamics and changes in associated soil physical and biological processes are
lacking. 相似文献
4.
Trend analysis of long-term temperature time series in the Greater Toronto Area (GTA) 总被引：3，自引：2，他引：1
As the majority of the world’s population is living in urban environments, there is growing interest in studying local urban climates. In this paper, for the first time, the long-term trends (31–162 years) of temperature change have been analyzed for the Greater Toronto Area (GTA). Annual and seasonal time series for a number of urban, suburban, and rural weather stations are considered. Non-parametric statistical techniques such as Mann–Kendall test and Theil-Sen slope estimation are used primarily for the assessing of the significance and detection of trends, and the sequential Mann test is used to detect any abrupt climate change. Statistically significant trends for annual mean and minimum temperatures are detected for almost all stations in the GTA. Winter is found to be the most coherent season contributing substantially to the increase in annual minimum temperature. The analyses of the abrupt changes in temperature suggest that the beginning of the increasing trend in Toronto started after the 1920s and then continued to increase to the 1960s. For all stations, there is a significant increase of annual and seasonal (particularly winter) temperatures after the 1980s. In terms of the linkage between urbanization and spatiotemporal thermal patterns, significant linear trends in annual mean and minimum temperature are detected for the period of 1878–1978 for the urban station, Toronto, while for the rural counterparts, the trends are not significant. Also, for all stations in the GTA that are situated in all directions except south of Toronto, substantial temperature change is detected for the periods of 1970–2000 and 1989–2000. It is concluded that the urbanization in the GTA has significantly contributed to the increase of the annual mean temperatures during the past three decades. In addition to urbanization, the influence of local climate, topography, and larger scale warming are incorporated in the analysis of the trends. 相似文献
5.
赤峰地区近50a气候变化诊断分析 总被引：2，自引：1，他引：1
利用线性回归、累积距平和多项式回归法,对赤峰地区1951—1990年12个气象台站的月、季、年平均气温、最高气温、最低气温序列进行连续性变化趋势分析,确定该区域的气候变化趋势。应用Mann-Kendall法和滑动t检验法检验气温序列变化的不连续性,确定突变时间。结果表明:赤峰地区12个月的平均气温均有升温趋势,增温幅度从0.56℃/10a到0.15℃/10a,其中2月份最强。季节增温最显著的是冬季,其次是秋季和春季,夏季最弱。年平均气温增温率是0.28℃/10a,1988年是变暖的第一年,突变时间在1993年;年平均最低气温增温率是0.29℃/10a,1988年是变暖的第一年,突变时间在1988年;年平均最高气温增温率是0.26℃/10a,1993年是变暖的第一年,突变时间在1993—1996年附近;平均最低气温和最高气温的变暖时间具有不对称性。 相似文献
6.
利用1961—2004年我国西南地区322个站的气温观测资料, 分析了乡村站、小城市站、大中城市站和国家基准/基本站气温变化趋势特点, 着重研究了城市化对城镇站和国家站地面气温记录的影响程度和相对贡献比例。结果显示:区域平均的各类台站年平均气温呈现不同程度的上升趋势, 城市站、国家站的增温速率均高于乡村站。大中城市站和国家站的年平均热岛增温率分别为0.086 ℃/ 10a和0.052 ℃/10a, 其增温贡献率分别达57.6%和45.3%。与大多数地区不同, 西南地区的增温速率明显偏小。因此, 尽管平均热岛强度变化比许多地区弱, 但其相对贡献明显, 表明城市化对该区域气温趋势的绝对影响较弱, 但相对影响较强。另外, 城市热岛增温有明显的季节变化, 表现为秋季最强, 春季或冬季次之, 夏季最弱。热岛增温贡献率则为春季最大 (100%), 夏季次之 (73%以上), 秋季和冬季相对较小。这主要是因为春、夏两季背景气候变凉或趋势微弱, 热岛增温在实际增温中占有更高的比例。 相似文献
7.
Trend analysis of temperature parameters in Iran 总被引：1，自引：1，他引：0
In this study, long-term annual and monthly trends in mean maximum, mean minimum and mean temperature are investigated at 35 synoptic stations in Iran. The statistical significance of trends is assessed by the Mann–Kendall test. Most stations, especially those in western and eastern parts of country, had significant positive trends in monthly temperature time series in summer season. However, the maximum number of stations with the positive trend were observed in April (30 stations), and then in August (29 stations) while the negative trends were seen in February (16 stations) and March (15 stations). On annual scale, most stations in western and southern parts of Iran had significant positive trend. Overall, about 71%, 66% and about 40% of stations had statistically significant trends in mean annual temperature, mean annual minimum temperature and in mean annual maximum temperature, respectively. These results, however, indicate that the climate in Iran is growing warmer, especially in summer. 相似文献
8.
Rainfall and rainy days trend in Iran 总被引：3，自引：0，他引：3
In this study, long-term annual and monthly trends in rainfall amount, number of rainy days and maximum precipitation in 24?h are investigated based on the data collected at 33 synoptic stations in Iran. The statistical significance of trend and climate variability is assessed by the Mann-Kendall test. The Linear trend analysis and the Mann-Kendall test indicate that there are no significant linear trends in monthly rainfall at most of the synoptic stations in Iran. However, the maximum number of stations with negative trends have been observed in April (29 station), and then in May (21 stations) and February (21 stations) and with positive trends in December (26 stations) and July (24 stations). The significant linear trends, with a significant level of 0.05, in annual rainfall have been noticed only at five stations. The monthly number of rainy days does not show any significant linear trend for most areas in Iran. The maximum number of stations with monthly negative trends in rainy days has also been observed in April with the minimum in December. In April, out of 24 stations with negative trends, 12 stations have a significant negative trend. Contrary to that, in October there is no significant linear trend. Most stations have positive trends in annual number of rainy days. Also, the monthly maximum precipitation in 24?h does not show any significant linear trend for most areas in Iran. The maximum number of stations with monthly negative trends in maximum precipitation has also been observed in February with the minimum in December. In spite of that, there are almost no significant precipitation variations in Iran during the last 50-odd years, the tendency of decreasing rainfall amount in April and increasing rainfall amount in December and July could indicate an eventual climate change in this area in the future. 相似文献
9.
Summary Northern Hemisphere monthly mean temperature anomalies during the twentieth century exhibit seasonal differences. To expose
the most significant intermonthly dissimilarities, here we investigate this issue in more details. We show that the trends
significantly differ for the months close to the equinoxes. Using the technique of multidimensional scaling analysis we find
that two underlying attributes are sufficient to acceptably describe the structure of the observed intermonthly dissimilarities.
Namely, these are the monthly sample percentiles around the 30th and the 70th together with the linear trends. We find that
intraannual temperature anomaly dissimilarities statistically depend on the seasonal cycles of the Northern Hemisphere oceanic
heat content, sea ice and snow cover and the Arctic sea ice cover as well as on the seasonality of the chaoticity of the Northern
Hemisphere atmospheric dynamics. We also speculate that the annual cycles of these ocean and cryosphere characteristics statistically
set the pattern for the observed course of linear warming over the calendar months. 相似文献
10.
呼和浩特市白塔机场气象观测要素分析 总被引：1，自引：0，他引：1
利用呼和浩特市白塔机场气象站1977--2010年月平均最高、最低气温,月降水量资料和1979--2010年月平均风速资料,分析了近34a气象要素变化特征。得出：呼和浩特白塔机场近34a来,（1）年平均气温、年降水量都没有明显的变化趋势,进入21世纪以来气候变率明显变大,气候不稳定性增加;（2）气温的年日较差明显增大,气候倾向率为0．4℃／10a;（3）年平均相对湿度在三个时段存在不同的变化特征;（4）年平均风速呈现出明显的减小趋势,平均每10a减小了0．3m·s^-1（5）四个要素中,气温年日较差由小变大的突变特征最为明显,1990年前后出现突变点;平均风速则存在由大转小的突变过程,突变时间点在1996年;年平均气温南低向高的突变过程较弱,且持续时间较短;年降水量和年平均相对湿度在近34a罩均不存在气候突变现象,气候状态相对稳定。呼和浩特机场气候与市区气候存在明显的差异．还需进一步深入分析。 相似文献
11.
根据青海省玉树站近58 a (1951~2008年)的逐月气温资料,利用线性回归、小波分析、M ann-Kendall法和S/R分析等方法,分析了该站春、夏、秋、冬季及年平均气温的变化特征,结果表明:1)近58 a来玉树站各季节和年平均气温均经历了先降后升的阶段,整体呈现出上升趋势,其中春季气温上升最快的阶段出现在20世纪80到90年代,其它季节和年平均气温出现在20世纪末到21世纪初;2)各季及年平均气温普遍具有准5 a的年际振荡;3)各季和年平均气温突变普遍发生在上世纪90年代;4)根据S/R分析得出,未来一段时期玉树站气温依旧保持增暖趋势,尤其在秋、冬季的增温显著。 相似文献
12.
近57年巴彦淖尔市平均最高最低气温及日较差变化 总被引：1，自引：0，他引：1
利用1954年-2010年内蒙古巴彦淖尔市9个台站的月平均最高、最低气温观测资料,对巴彦淖尔市年、季平均最高、最低气温变化趋势的空间分布状况和时间变化特征进行了分析。结果表明,近57年来,巴彦淖尔市年平均最高气温的变化特征呈现北部增暖幅度明显大于南部,且近十年呈弱降温趋势;年平均最低气温与全国各地基本一致,呈明显的变暖趋势;无论是年还是季,平均最低气温的增暖幅度明显大于平均最高气温的增幅;年平均日较差多呈下降趋势,并在北部地区尤为明显,各季平均日较差亦均呈下降趋势,并以冬季的下降幅度为最大;年平均最高气温和最低气温的变化在年代际变化上基本呈现较为一致的变化,即57年来主要的变暖均是从20世纪80年代中期开始,均在90年代后期达到了近57年来的历史新高,最高气温近十年来又略有回落。 相似文献
13.
潮白河流域为北京主要供水源,其水资源量对北京用水保障至关重要,因此开展该流域在全球1.5℃和2.0℃升温下的径流预估研究具有现实意义。利用1961—2001年WATCH数据对SWAT水文模型进行率定和验证,在此基础上,应用第五次耦合模式比较计划(CMIP5)中5个全球气候模式在典型浓度路径(RCP4.5、RCP6.0和RCP8.5)下预估的全球1.5℃和2.0℃升温下的数据驱动SWAT模型,开展了潮白河流域气温、降水及径流量的变化预估研究,并量化评估由气候模式和RCPs导致的水文效应的不确定性。结果表明：(1) SWAT模型基本能较好地模拟潮白河流域的月径流特征,应用该模型进行气候变化对径流量的影响评估是可行的。(2)在全球1.5℃和2.0℃升温下,潮白河流域年平均温度较基准期(1976—2005年)分别增加1.5℃和2.2℃,年平均降水量也增加4.9%和7.0%。预估的年径流量在全球1.5℃升温下总体略有增加,盛夏和秋初的径流量占全年的比例也有所增加;在全球2.0℃升温下,年径流量增幅达30%以上,但夏季径流量占全年的比例明显减少。(3)在全球2.0℃升温下,潮白河流域极端丰水流量明显增加,洪涝发生风险增大。(4)未来气温、降水量和径流量的预估都存在一定的不确定性,在全球2.0℃升温下不确定性更大;相对而言,径流量的不确定性要远大于降水量的不确定性;无论是全球1.5℃升温下还是2.0℃升温下,预估不确定性主要来源于全球气候模式。 相似文献
14.
1951～2002年中国平均最高、最低气温及日较差变化 总被引：74，自引：8，他引：66
利用1951～2002年全国733个台站的月平均最高、最低气温资料,对我国年、季平均最高、最低气温变化趋势的空间分布状况和时间变化特征进行了分析.结果表明:近52年来,我国平均最高气温的变化特征呈现北方增暖明显、南方变化不明显或呈弱降温趋势;年平均最低气温全国各地基本一致,呈明显的变暖趋势;无论是年还是季,平均最低气温的增暖幅度明显大于平均最高气温的增幅;我国年平均日较差多呈下降趋势,并在我国北方地区尤为明显,各季平均日较差亦均呈下降趋势,并以冬季的下降幅度为最大;年平均最高气温和最低气温的变化在年代际变化上基本呈现较为一致的步伐,即52年来主要的变暖均是从20世纪80年代中期开始,均在90年代后期达到了近52年来的历史新高,近年来又略有回落. 相似文献
15.
Impact of recent climate change on the hydrology of coastal Mediterranean rivers in Southern France 总被引：2，自引：1，他引：1
The purpose of this paper is to analyse the regional impact of recent climate change on the water resources in southern France. We produced spatial reconstructions of the monthly evolutions of temperature, precipitation and water discharge in 15 watersheds of six coastal river basins and examined the major changes based on trend analysis for the last 40 years. In this part of the Mediterranean, the general warming trend was strongly enhanced by changes in the atmospheric circulation patterns, characterized by a northward extension of the subtropical high pressure domain during spring and summer. During these seasons, monthly warming rates could achieve almost twice the mean annual warming rates. Although annual precipitation did not follow clear trends, water discharge significantly decreased in one third of the watersheds and accounted for an estimated 20% reduction of the water resources in this region. This concerns both the highest and lowest watersheds. In the former, the reduction is likely the result of a temperature induced switch of snowfall to rainfall at high altitudes. In the latter, the reduction of discharge seems to come from lower groundwater levels, which may be related to the temperature increase too, but also have other origins. The recent climatic evolution is consistent with most modelling simulations for the future, indicating that the reduction of the water resources will hold on, probably still enhanced by decreases in precipitation. 相似文献
16.
17.
Temperature and precipitation fluctuations in the Czech Republic during the period of instrumental measurements 总被引：2，自引：0，他引：2
Rudolf Brázdil Pavel Zahradní?ek Petr Pi?oft Petr ?těpánek Monika Bělínová Petr Dobrovolny 《Theoretical and Applied Climatology》2012,110(1-2):17-34
The history of early meteorological observations using instruments in the Czech Lands is described (the longest temperature series for Prague-Klementinum starts in 1775, precipitation series for Brno in 1803). Using the PRODIGE method, long-term monthly temperature and precipitation series from selected secular stations were homogenised (for 10 and 12 stations, respectively). All the seasonal and annual temperature series for the common period 1882–2010 show a significant positive linear trend with accelerated warming from the 1970s onwards. No significant linear trends were disclosed in the series of seasonal and annual precipitation totals. Correlation coefficients between the Czech series analysed decrease as distances between measuring stations increase. A sharper decrease of correlations for precipitation totals displays much weaker spatial relationships than those for mean temperatures. The highest correlations between all stations appeared in 1921–1950, the lowest in 1891–1920 (temperature) and 1981–2010 (precipitation). Wavelet analysis reveals that very distinct annual cycles as well as the slightly weaker semi-annual ones are better expressed for temperature series than for precipitation. Statistically significant cycles longer than 1?year are temporally unstable and sporadic for precipitation, while in the temperature series cycles of 7.4–7.7 and 17.9–18.4?years were recorded as significant by all stations in 1882–2010 (quasi-biennial cycle of 2.1–2.2?years for half the stations). Czech homogenous temperature series correlate best with those of the Northern Hemisphere for annual, spring and summer values (with significant correlation coefficients between 0.60 and 0.70), but this relation is temporally unstable. Circulation indices, such as the North Atlantic Oscillation Index (NAOI) and the Central European Zonal Index (CEZI), may explain the greater part of Czech temperature variability, especially from December to March and for the winter; however, this relationship is much weaker, or even random, for precipitation series. Further, relationships with the Southern Oscillation Index (SOI) are weak and random. Relatively weak coincidences exist between statistically significant cycles in the Czech series and those detected in NAOI, CEZI and SOI series. 相似文献
18.
A dataset of air temperature and precipitation time series (1959?C2008) from 61 stations across Shanxi, China is used to analyze the climate change. The monotonic trends and step (abrupt) trends for annual and seasonal series data of mean air temperature and total precipitation are tested by using Mann?CKendall test and Mann?CWhitney test, respectively. The results show that annual mean air temperature has increased by 1.20°C during the past 50?years. Winter, spring, and autumn have experienced a significant increase in air temperature. The step trend for annual mean air temperature is different from, but closely related with, those for seasonal mean air temperature. Spatially, there is an enhanced warming trend from south to north in Shanxi, and the most remarkable warming occurs in northern Shanxi. Annual precipitation has decreased by 99.20?mm during the past half century. The decrease is mainly caused by precipitation decline in rainy season (June?CSeptember), though precipitation in post-rainy season (October?CNovember) also tended to decrease. An abrupt decrease in precipitation has occurred since late 1970s. Decrease in precipitation is highest in central Shanxi and in the area along the west fringe between Sanchuan River and Fenhe River in western Shanxi. 相似文献
19.
20.
This study investigated the trends in rainfall and temperature and the possibility of any rational relationship between the trends over the homogeneous regions over India. Annual maximum temperature shows an increasing trend in all the homogeneous temperature regions and corresponding annual rainfall also follow the same pattern in all the regions, except North East. As far as monthly analysis is concerned, no definite pattern has been observed between trends in maximum and minimum temperature and rainfall, except during October. Increasing trends of maximum and minimum temperature during October accelerate the water vapor demand and most of the lakes, rivers, ponds and other water bodies with no limitation of water availability during this time fulfills the water vapor demand and shows an increasing trend of rainfall activity. This study shows there exists no direct relationship between increasing rainfall and increasing maximum temperature when monthly or seasonal pattern is concerned over meteorological subdivisions of India, however we can make a conclusion that the relation between the trends of rainfall and temperature have large scale spatial and temporal dependence. 相似文献