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1.
Summary The variations and trends in annual and seasonal air temperatures in Greece were examined on the basis of ground measurements for 25 stations during the period 1951–1993, and satellite measurements for the south eastern Mediterranean during the period 1979–1991. Data were smoothed using a 5-year running mean and were thereafter examined by regression analysis to define trends in the long duration time series. Data were also examined to detect abrupt changes and trends in the long duration annual, winter and summer series of mean maximum, mean minimum and mean temperatures. An overall cooling trend was detected for the majority of stations in winter over the entire period; the same cooling trend was also recognised for the annual and summer mean values, although a reverse warming trend was detected around the mid-70s at several stations. Satellite measurements indicate a slight warming trend, although this is not statistically significant. Considering the results of the regression analysis and the statistical tests applied to the 25 stations, it may be concluded that annual mean temperatures are dominated by an overall cooling trend, with the exception of stations in urban areas where urbanisation effects may have resulted in a warming trend. Summer temperatures, however, exhibit a warming trend roughly after 1975 at most stations.With 5 Figures  相似文献   

2.
This study aims to investigate the precipitation trends in Keszthely (Western Hungary, Central Europe) through an examination of historical climate data covering the past almost one and a half centuries. Pettitt’s test for homogeneity was employed to detect change points in the time series of monthly, seasonal and annual precipitation records. Change points and monotonic trends were analysed separately in annual, seasonal and monthly time series of precipitation. While no break points could be detected in the annual precipitation series, a significant decreasing trend of 0.2–0.7 mm/year was highlighted statistically using the autocorrelated Mann-Kendall trend test. Significant change points were found in those time series in which significant tendencies had been detected in previous studies. These points fell in spring and winter for the seasonal series, and October for the monthly series. The question therefore arises of whether these trends are the result of a shift in the mean. The downward and upward shift in the mean in the case of spring and winter seasonal amounts, respectively, leads to a suspicion that changes in precipitation are also in progress in these seasons. The study concludes that homogeneity tests are of great importance in such analyses, because they may help to avoid false trend detections.  相似文献   

3.
This study analyzes the mean maximum and minimum temperature trends on a monthly, seasonal, and annual timescale by applying various statistical tools to data from 476 Spanish weather stations during the period between 1961 and 2006. The magnitude of the trends was derived from the slopes of the regression lines using the least squares method, and the nonparametric Mann–Kendall test was used to determine the statistical significance of the trends. Temperature significantly increased in over 60% of the country in March, June, spring, and summer in the case of maximum temperatures and in March, May, June, August, spring, and summer for minimum temperatures. At the annual resolution, temperatures significantly increased in over 90% of Spain with a rise of around 0.3°C/decade. The maximum temperature increased at a higher rate than the minimum temperature from midsummer to early winter as well as in winter, spring, and summer and also on an annual basis.  相似文献   

4.
Spatial patterns and temporal trends of precipitation in Iran   总被引：3，自引：0，他引：3  
Spatial patterns of monthly, seasonal and annual precipitation over Iran and the corresponding long-term trends for the period 1951–2009 are investigated using the Global Precipitation Climatology Centre gridded dataset. Results suggest that the spatial patterns of annual, winter and spring precipitation and the associated coefficients of variation reflect the role of orography and latitudinal extent between central-southern arid and semi-arid regions and northern and western mountainous areas. It is also shown that precipitation occurrence is almost regularly distributed within the year in northern areas while it is more concentrated in a few months in southern Iran. The spatial distribution of Mann–Kendal trend test (Z statistics) for annual precipitation showed downward trend in north-western and south-eastern Iran, whereas western, central and north-eastern exhibited upward trend, though not statistically significant in most regions. Results for winter and autumn revealed upward trend in most parts of the country, with the exception of north-western and south-eastern where a downward trend is observed; in spring and summer, a downward trend seems to prevail in most of Iran. However, for all seasons the areas where the detected trend is statistically significant are limited to a few spot regions. The overall results suggest that the precipitation is decreasing in spring and summer and increasing in autumn and winter in most of Iran, i.e. less precipitation during the warm season with a consequent intensification of seasonality and dryness of the country. However, since the detected trends are often not statistically significant, any stringent conclusion cannot be done on the future tendencies.  相似文献   

5.
The multiple time scale climate changes are studied and calculated with statistical analysis and wavelet transformation on the basis of daily series of observed data over the period 1901-2007 in Macau.The result shows that statistically significant oscillations with 2 to 5 years of period generally exist in the series of climate variables(e.g.annual mean surface air temperature and precipitation as well as evaporation etc.),but with obvious locality in time domain.The variation of annual mean surface air temperature has a quasi 60-year period.The phases of the 60-year variation approximately and consistently match that of Atlantic Multidecadal Oscillation(AMO).The oscillations of seasonal mean surface air temperature in summer and winter have the periods of quasi 30-year and quasi 60-year,respectively.These two periods of oscillations have statistically significant correlation with Pacific decadal oscillation(PDO) and AMO,individually.The multidecadal variations of the precipitation of the annually first flood period and annual evaporation are dominated by periods of quasi 30-year and quasi 50-year,respectively.  相似文献   

6.
1960-2009年咸宁市气候变化特征分析   总被引：1，自引：0，他引：1       下载免费PDF全文
利用1960-2009年咸宁市3个地面气象站气象资料,统计分析近50 a来该区域气温、降水等主要气候要素的年变化、四季变化及年代际变化的趋势特征。结果表明：近50 a研究区气温有上升趋势,气候倾向率为0.23℃/10a,年平均气温在20世纪90年代末发生突变。春秋季平均气温分别在2002年和1999年发生突变,夏季平均气温在2006年发生突变,冬季平均气温早在1990年发生突变。春季与秋季平均气温的变化比较一致,冬季平均气温对全球变暖响应最敏感,春秋与秋季对气候变暖的响应是比较敏感,而夏季对气候变暖的响应最为迟缓。近50 a年降水量呈波动但无明显增降的趋势,其中春夏两季变化趋势较为一致并有下降的趋势,且春夏降水量的变化主导着年降水量的变化;而冬季降水量有上升的趋势。通过对气温与降水变化趋势的比较,发现冬季对气候变化的响应最显著、其余季节无明显相关性。  相似文献   

7.
利用1960—2009年咸宁市3个地面气象站气象资料,统计分析近50 a来该区域气温、降水等主要气候要素的年变化、四季变化及年代际变化的趋势特征。结果表明：近50 a研究区气温有上升趋势,气候倾向率为0.23℃/10 a,年平均气温在20世纪90年代末发生突变。春秋季平均气温分别在2002年和1999年发生突变,夏季平均气温在2006年发生突变,冬季平均气温在1990年发生突变。春季与秋季平均气温的变化较一致,冬季平均气温对全球变暖响应最敏感,春季与秋季对气候变暖的响应较敏感,而夏季对气候变暖的响应最为迟缓。近50 a咸宁市年降水量呈波动但无明显增降的趋势,其中春夏两季变化趋势较为一致并有下降的趋势,且春夏降水量的变化主导着年降水量的变化;而冬季降水量有上升的趋势。通过对气温与降水变化趋势的比较,发现冬季对气候变化的响应最显著,其余季节无明显相关性。  相似文献   

8.
Summary  Temperature and precipitation records from 1949 to 1998 were examined for 25 stations throughout the State of Alaska. Mean, maxima, and minima temperatures, diurnal temperature range, and total precipitation were analyzed for linear trends using least squares regressions. Annual and seasonal mean temperature increases were found throughout the entire state, and the majority were found to be statistically significant at the 95% level or better. The highest increases were found in winter in the Interior region (2.2 °C) for the 50 year period of record. Decreases in annual and seasonal mean diurnal temperature range were also found, of which only about half were statistically significant. A state-wide decrease in annual mean diurnal temperature range was found to be 0.3 °C, with substantially higher decreases in the South/Southeastern region in winter. Increases were found in total precipitation for 3 of the 4 seasons throughout most of Alaska, while summer precipitation showed decreases at many stations. Few of the precipitation trends were found to be statistically significant, due to high interannual variability. Barrow, our only station in the Arctic region, shows statistically significant decreases in annual and winter total precipitation. These findings are largely in agreement with existing literature, although they do contradict some of the precipitation trends predicted by the CO2-doubling GCM’s. Received August 30, 1999/Revised March 21, 2000  相似文献   

9.
Summary In this study, trends of annual and seasonal surface air temperature time series were examined for 20 stations in Greece for the period 1955–2001, and satellite data for the period 1980–2001. Two statistical tests based on the least square method and one based on the Mann-Kendall test, which is also capable of detecting the starting year of possible climatic discontinuities or changes, were used for the analysis. Greece, in general, shows a cooling trend in winter for the period 1955–2001, whereas, summer shows an overall warming trend, however, neither is statistically significant. As a result, the overall trend of the annual values is nearly zero. Comparison with corresponding trends in the Northern Hemisphere (NH) shows that temperatures in Greece do not follow the intense warming trends. Satellite data indicate a remarkable warming trend in mean annual, winter and summer in Greece for the period 1980–2001, and a slight warming trend in annual, spring and autumn for the NH. Comparison with the respective trends detected in the surface air temperature for the same period (1980–2001) shows they match each other quite well in both Greece and the NH. The relationship between temperature variability in Greece and atmospheric circulation was also examined using correlation analysis with three circulation indices: the well-known North Atlantic Oscillation Index (NAOI), a Mediterranean Oscillation Index (MOI) and a new Mediterranean Circulation Index (MCI). The MOI and MCI indices show the most interesting correlation with winter temperatures in Greece. The behaviour of pressure and the height of the 500hPa surface over the Mediterranean region supports these results.  相似文献   

10.
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   

11.
Summary In this study, the trends of annual and seasonal precipitation time series were examined on the basis of measurements of 22 surface stations in Greece for the period 1955–2001, and satellite data during the period 1980–2001. For this purpose, two statistical tests based on the least square method and one based on the Mann-Kendall test, which is also capable of detecting the starting year of possible climatic discontinuities or changes, are applied. Greece, in general, presents a clear significant downward trend in annual precipitation for the period 1955–2001, which is determined by the respective decreasing trend in winter precipitation. Both winter and annual series exhibit a downward trend with a starting year being 1984. Satellite-derived precipitation time series could be an alternative means for diagnosing the variability of precipitation in Greece and detecting trends provided that they have been adjusted by surface measurements in the wider area of interest. The relationship between precipitation variability in Greece and atmospheric circulation was also examined using correlation analysis with three circulation indices: the well-known North Atlantic Oscillation Index (NAOI), a Mediterranean Oscillation Index (MOI) and a new Mediterranean Circulation Index (MCI). NAOI is the index that presented the most interesting correlation with winter, summer and annual precipitation in Greece, whereas the MOI and MCI were found to explain a significant proportion of annual and summer precipitation variability, respectively. The observed downward trend in winter and annual precipitation in Greece is linked mainly to a rising trend in the hemispheric circulation modes of the NAO, which are connected with the Mediterranean Oscillation Index.  相似文献   

12.
On the basis of the mean annual and seasonal temperatures from 30 meteorological stations in the Jinsha River Basin (JRB) from 1961 to 2008, the temperature trends are analyzed by using Mann–Kendall test and linear trend analysis. There is an increasing trend in mean annual and seasonal temperatures during this period, and the increasing trends in winter seem more significant than those in the other three seasons. The mean annual temperature has increased by 0.0158°C/year during the last 48 years. There are more than 70% of stations exhibiting increasing trends for annual and seasonal temperatures. The increasing trends in the headwater and upper reaches are more dominant than those in the middle and lower reaches. The largest increase magnitude occurred in the low temperature area, while the largest decrease magnitude occurred in the high temperature area. The decreasing trends are mainly characterized for the maximum temperature time series, and summer is the only season showing a slight and insignificant increasing trend. All the time series showed a statistically significant increasing trend at the level of α?=?0.05 for the minimum temperature time series. As a whole, the increasing magnitude of the minimum temperature is significantly greater than the decreasing magnitude of the maximum temperature.  相似文献   

13.
The following study investigates temperature and precipitation trends in instrumental time series between 1960 and 2006 at 88 meteorological stations located in the Upper Danube Basin. Time series were tested for inhomogeneities with several common homogeneity tests, trend magnitudes of annual and seasonal time series were calculated by least square fitting and the significance of trend values was checked and quantified by the Mann-Kendall test. The results confirm a particularly strong recent Climate Change in the investigation area. Increasing temperature trends show remarkably high trend values up to 0.8°C/decade in the summer season. The trends are highly significant for all investigated summer, spring and annual time series. Winter and spring temperature trends show consistently positive trend values as well even though some time series show no significance at all and the calculated trend values are smaller. Autumn temperature trends are mostly non-significant with low values (up to 0.3°C/decade) and several negative trends. Most of the highest trend values can be found in lower altitudes whereas stations situated in alpine regions tend to show low trend magnitudes and often exhibit non-significant results. Precipitation time series show positive as well as negative trends in the annual and seasonal analysis. At most stations a precipitation decrease in summer and autumn and an increase in winter was observed during the last 47?years whereas the spring and mean annual precipitation exhibits no change at all. But most time series are not conclusive since they show predominantly no significance and they often exhibit only low trend values.  相似文献   

14.
利用龙岩市1960—2013年7个国家级气象站的逐日降水资料,采用Mann-Kendall趋势和突变检验法及Morlet小波功率谱分析方法,分析龙岩市降水的时空分布规律。结果表明,龙岩市年降水量呈微弱增加趋势,年际波动振幅较大。年降水量多年平均值为1 641 mm,最小值出现在1991年(1 139.9 mm),最大值则出现在1975年(2 286.9 mm),年降水时间序列存在显著的2~8 a的周期。降水主要集中在春季,春季降水量占全年降水量的38.2%左右,其次是夏季和秋季,冬季降水量最少,仅占全年降水量的11.5%。1—6月月平降水量呈现增长趋势,8—12月呈现递减趋势。北部和南部年降水量整体变化趋势基本一致,南部地区总体小于北部地区,只有极个别年份南部地区降水量大于北部地区。  相似文献   

15.
Abstract

Trends in Canadian temperature and precipitation during the 20th century are analyzed using recently updated and adjusted station data. Six elements, maximum, minimum and mean temperatures along with diurnal temperature range (DTR), precipitation totals and ratio of snowfall to total precipitation are investigated. Anomalies from the 1961–1990 reference period were first obtained at individual stations, and were then used to generate gridded datasets for subsequent trend analyses. Trends were computed for 1900–1998 for southern Canada (south of 60°N), and separately for 1950–1998 for the entire country, due to insufficient data in the high arctic prior to the 1950s.

From 1900–1998, the annual mean temperature has increased between 0.5 and 1.5°C in the south. The warming is greater in minimum temperature than in maximum temperature in the first half of the century, resulting in a decrease of DTR. The greatest warming occurred in the west, with statistically significant increases mostly seen during spring and summer periods. Annual precipitation has also increased from 5% to 35% in southern Canada over the same period. In general, the ratio of snowfall to total precipitation has been increasing due mostly to the increase in winter precipitation which generally falls as snow and an increase of ratio in autumn. Negative trends were identified in some southern regions during spring. From 1950–1998, the pattern of temperature change is distinct: warming in the south and west and cooling in the northeast, with similar magnitudes in both maximum and minimum temperatures. This pattern is mostly evident in winter and spring. Across Canada, precipitation has increased by 5% to 35%, with significant negative trends found in southern regions during winter. Overall, the ratio of snowfall to total precipitation has increased, with significant negative trends occurring mostly in southern Canada during spring.

Indices of abnormal climate conditions are also examined. These indices were defined as areas of Canada for 1950–1998, or southern Canada for 1900–1998, with temperature or precipitation anomalies above the 66th or below the 34th percentiles in their relevant time series. These confirmed the above findings and showed that climate has been becoming gradually wetter and warmer in southern Canada throughout the entire century, and in all of Canada during the latter half of the century.  相似文献   

16.
1958—2009年本溪地区气候变化特征   总被引：7，自引：4，他引：3       下载免费PDF全文
以本溪地区4个站点数据为基础,同时选取气温和降水2个主要的气象要素指标,采用线性倾向估计、Mann-Kendall和累积距平法,对1958—2009年本溪地区的气候变化进行探讨。结果表明：近52 a来,本溪地区年和春、秋季及冬季平均气温均呈明显的增温趋势。夏季虽有增温趋势,但是不显著。本溪地区春和冬季降水量均呈弱增加趋势,而年夏季及秋季降水量均呈下降趋势。总体来说,近52 a来本溪地区降水量呈下降趋势。本溪地区年和各季平均气温均先后在20世纪80年代末发生了突变。20世纪80年代以来,本溪地区相对进入了明显的暖期。年和各季的降水量均没有发生突变。  相似文献   

17.
1980～2014年中国生态脆弱区气候变化特征分析   总被引：1，自引：0，他引：1  
为了全面把握20世纪80年代以来中国生态脆弱区气候变化的特征,利用基于全国2000多个站点的格点化逐月资料,对中国典型生态脆弱区1980～2014年的日平均气温、日最高和最低气温、降水、相对湿度、风速和蒸发皿蒸发量的变化特征进行了分析。结果表明:（1）中国生态脆弱区日平均气温、日最高和最低气温几乎都呈上升趋势;日平均气温增幅北方大于南方;北方生态脆弱区日平均气温、日最高和最低气温、南方生态脆弱区日最低气温的季节增幅多为春季最大,秋季或冬季最小。（2）全区平均降水变化趋势不明显;生态脆弱区降水距平百分率春季多为增长趋势,夏季多为减少趋势,秋、冬季和年北方多为增长趋势,南方多为减少趋势。（3）相对湿度以减少趋势为主,只有黄土高原南部脆弱区秋、冬季和干旱半干旱区脆弱区冬季相对湿度距平百分率的趋势为正,这几个正值区同时也是降水增长大值区。（4）风速基本为减少趋势,春季减少趋势最大。（5）全区平均蒸发皿蒸发量春、夏季和年为减少趋势,冬季为增长趋势;北方生态脆弱区蒸发皿蒸发量四季和年多呈减少趋势;南方生态脆弱区蒸发皿蒸发量春、夏季以减少趋势为主,秋、冬季和年呈增长趋势。  相似文献   

18.
Variations of precipitation amounts, atmosphere circulation, and relative humidity at three high mountainous stations in Bulgaria are investigated. The research period is 1947–2008. Three stations are peaks Musala (2,927?m), Cherni Vrah (2,293?m), and Botev (2,378?m). Homogeneity checks were performed. Some adjustments of monthly precipitation amounts were done due to the change of rain gauge placements. Methods employed in this research are statistical—trend analysis, multiple linear regression, autocorrelation, spectral analysis, correlation, etc. The main conclusion is that annual precipitation amounts in high mountainous parts of Bulgaria decrease over the last six decades. These trends are statistically significant in lower and northern stations of Cherni Vrah and Botev. Observed tendencies are due mainly to precipitation in months of the cold part of the year—from October till March and also June. Atmospheric circulation, on an annual basis, shows a decrease in the number of cyclones and an increase of the number of anticyclones. Atmospheric pressure has no significant change during the research period. Relative humidity, on an annual basis, increases at the two western stations (Musala and Cherni Vrah) and decreases at Botev peak. Multiple regression statistical modeling shows good results at stations Cherni Vrah and Botev. Station Musala is more difficult to model with the five predictors used because of the winter months. Correlation coefficients reveal a good connection between precipitation amounts at all three stations. Only Botev station has a significant cycle in precipitation distribution, which is about 3.7?months.  相似文献   

19.
根据河北省辛集气象站近54 a（1957-2010年）的月平均地面观测资料,采用气候统计学方法,分别从气温及降水的趋势变化、周期变化、突变特征等方面进行分析,总结该市近54 a气温及降水的变化特征。结果表明：1）近54 a来辛集市年平均气温、各季平均气温及极端最低气温呈显著上升趋势,四季中冬季增温趋势最明显,夏季增温幅度最弱,极端最低气温上升而极端最高气温下降,导致气温日较差减小;2）在20世纪60年代,年平均和冬季气温表现出准2～3 a的显著年际变化周期,年平均和春季气温还表现出准7 a的显著年际周期特征;3）该市年降水量近54 a来整体呈先增加后减少的变化趋势;4）年和夏秋季降水量在20世纪60年代均表现出准3～4 a的周期特征,而在春季准7 a的年际振荡贯穿始终;5）辛集市的气温变化趋势以及突变开始时间与全国、河北省以及石家庄地区近50 a气温变化基本一致,但该市的降水量变化则略有不同,降水量变化的长期趋势不显著且突变不明显,主要是由于降水量的时空变化差异性较大。  相似文献   

20.
1961—2008年昆山市气候变化特征   总被引：2，自引：2，他引：0       下载免费PDF全文
利用1961—2008年昆山市气温、降水量和日照时数等主要气象要素资料,通过线性趋势方程、滑动平均等统计方法,探讨了近48 a昆山市气候变化特征。结果表明：昆山市年平均气温和四季平均气温均呈升高趋势,其中春季增温最明显,冬季次之;年平均最低气温的增温速度高于最高气温;降水量总体呈略上升趋势,冬、夏两季降水量增加明显,春、秋季降水量则呈减小趋势,但不显著,降水年际变化幅度较大;年总日照时数和各季日照时数均呈下降趋势,其中尤以夏季减少最明显。  相似文献   

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