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1.
Mann?CKendall non-parametric test was employed for observational trend detection of monthly, seasonal and annual precipitation of five meteorological subdivisions of Central Northeast India (CNE India) for different 30-year normal periods (NP) viz. 1889?C1918 (NP1), 1919?C1948 (NP2), 1949?C1978 (NP3) and 1979?C2008 (NP4). The trends of maximum and minimum temperatures were also investigated. The slopes of the trend lines were determined using the method of least square linear fitting. An application of Morelet wavelet analysis was done with monthly rainfall during June?CSeptember, total rainfall during monsoon season and annual rainfall to know the periodicity and to test the significance of periodicity using the power spectrum method. The inferences figure out from the analyses will be helpful to the policy managers, planners and agricultural scientists to work out irrigation and water management options under various possible climatic eventualities for the region. The long-term (1889?C2008) mean annual rainfall of CNE India is 1,195.1?mm with a standard deviation of 134.1?mm and coefficient of variation of 11%. There is a significant decreasing trend of 4.6?mm/year for Jharkhand and 3.2?mm/day for CNE India. Since rice crop is the important kharif crop (May?COctober) in this region, the decreasing trend of rainfall during the month of July may delay/affect the transplanting/vegetative phase of the crop, and assured irrigation is very much needed to tackle the drought situation. During the month of December, all the meteorological subdivisions except Jharkhand show a significant decreasing trend of rainfall during recent normal period NP4. The decrease of rainfall during December may hamper sowing of wheat, which is the important rabi crop (November?CMarch) in most parts of this region. Maximum temperature shows significant rising trend of 0.008°C/year (at 0.01 level) during monsoon season and 0.014°C/year (at 0.01 level) during post-monsoon season during the period 1914?C2003. The annual maximum temperature also shows significant increasing trend of 0.008°C/year (at 0.01 level) during the same period. Minimum temperature shows significant rising trend of 0.012°C/year (at 0.01 level) during post-monsoon season and significant falling trend of 0.002°C/year (at 0.05 level) during monsoon season. A significant 4?C8?years peak periodicity band has been noticed during September over Western UP, and 30?C34?years periodicity has been observed during July over Bihar subdivision. However, as far as CNE India is concerned, no significant periodicity has been noticed in any of the time series.  相似文献   

2.
A diagnostic study of 80 yrs(1901–80) of surface temperatures collected at West Lafayette, Indiana, has been found to be in tune with the global trend and that for the eastern two-thirds of the United States, namely, cold at the turn of the century, warming up to about 1940, and then cooling to present. The study was divided into two cold periods (1901–18, 1947–80) and a warm period (1919–46), based on the distribution of annual mean temperature. Decadal mean annual temperatures ranged from 10 °C in period I to 12.2 °C in period II, to 9.4 °C during the present cold period. Themean annual temperature for the 80 yr ranged from the coldest of 8.7 °C in 1979 to the warmest of 13.6 °C in 1939. Thedaily mean temperature for the entire 80-yr ranged from -4.7 °C on 31 January to 25.1 °C on 27 July. Thecoldest daily mean was -26.7 °C on 17 January, 1977, and thewarmest daily mean was 35 °C on 14 July, 1936. The range of values for thedaily mean maximum temperatures was -.2 °C on 31 January to 31.4 °C on 27 July. Corresponding values for thedaily mean minimum are -9.2 °C on 31 January and 18.7 °C on 27 July. The all-time extreme temperatures are -30.6 °C on 26 February, 1963 and 43.9 °C on 14 July, 1936. Climatic variability has been considered by computing the standard deviations of a) the daily mean maximum and minimum temperature per year, and b) the daily mean maximum and minimum temperatures for each day of the year for the 80-yr period. These results have shown that there is more variability in the daily mean maximum per year than in the daily mean minimum, for each year of the 80-yr period. Also the variability for both extremes has been greater in each of the two cold periods than in the warm period. Particularly noticeable has been theincrease in the variability of the daily mean minima per year during the current cooling trend. Further, it has been determined that the variability in the daily mean maxima and minima for each day of the year (based on the entire 80 yrs is a) two times greater in the winter than in the summer for both extremes, and b) about the same for each in the summer, greater for daily maximum in the spring and fall, but greater for the daily minimum during the winter. The latter result is undoubtedly related to the effect of snow cover on daily minimum temperatures. An examination of daily record maximum and minimum temperatures has been made to help establish climatic trends this century. For the warm period, 175 record maxima and 68 record minima were set, compared to 213 record minima and 105 record maxima during the recent cold period. For West Lafayette, the present climatic trend is definitely one of extreme record-breaking cold. Evidence has also been presented to show the substantial increases in snowfall amounts in the lee regions of the Great Lakes during the present cold period, due to the lake-induced snow squalls associated with cold air mass intrusions. The possible impact of the cooling trend on agricultural activities has also been noted, due to a reduced growing season.  相似文献   

3.
In this paper, temperature and rainfall data series were analysed from 34 meteorological stations distributed throughout Bangladesh over a 40-year period (1971 to 2010) in order to evaluate the magnitude of these changes statistically and spatially. Linear regression, coefficient of variation, inverse distance weighted interpolation techniques and geographical information systems were performed to analyse the trends, variability and spatial patterns of temperature and rainfall. Autoregressive integrated moving average time series model was used to simulate the temperature and rainfall data. The results confirm a particularly strong and recent climate change in Bangladesh with a 0.20 °C per decade upward trend of mean temperature. The highest upward trend in minimum temperature (range of 0.80–2.4 °C) was observed in the northern, northwestern, northeastern, central and central southern parts while greatest warming in the maximum temperature (range of 1.20–2.48 °C) was found in the southern, southeastern and northeastern parts during 1971–2010. An upward trend of annual rainfall (+7.13 mm per year) and downward pre-monsoon (?0.75 mm per year) and post-monsoon rainfall (?0.55 mm per year) trends were observed during this period. Rainfall was erratic in pre-monsoon season and even more so during the post-monsoon season (variability of 44.84 and 85.25 % per year, respectively). The mean forecasted temperature exhibited an increase of 0.018 °C per year in 2011–2020, and if this trend continues, this would lead to approximately 1.0 °C warmer temperatures in Bangladesh by 2020, compared to that of 1971. A greater rise is projected for the mean minimum (0.20 °C) than the mean maximum (0.16 °C) temperature. Annual rainfall is projected to decline 153 mm from 2011 to 2020, and a drying condition will persist in the northwestern, western and southwestern parts of the country during the pre- and post-monsoonal seasons.  相似文献   

4.
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   

5.
宿州雷暴气候特征及其灾变G ANN预测模型研究   总被引：1，自引：0，他引：1  
根据宿州市5个气象站1957-2008年雷暴日观测资料,利用数理统计方法分析了宿州雷暴的时空分布规律,以及雷暴与降水、温度的关系。结果显示：宿州属于多雷区,南部多于北部,南北相差3.21-4.65天;年际变化大,年累计雷暴日最多相差37天,初终雷及无雷期年际间振荡的幅度较为剧烈,52年来累计雷暴日线性减少的趋势明显,减少幅度为1.61-2.89天/10a;季分布以夏季最多,冬季最少;月分布呈单峰型,雷暴多集中在4-9月,以7月最多,12月最少;日分布呈单峰型,以16：00-18：00频率最大;多年平均月雷暴日数序列与相应的气温、降水量之间呈显著正相关。为了进一步预测雷暴的长期演变趋势,以埇桥为例建立了雷暴多发年份灰色人工神经网络组合预测模型,预测下一个雷暴多发年将发生在2025年。  相似文献   

6.
Temperature trends in Libya over the second half of the 20th century   总被引：1，自引：0，他引：1  
This paper investigates spatial variability of temperature trends over Libya in the second half of the 20th century. The study is based on complete and homogeneous time series of minimum, maximum, and mean temperature for ten observatories. During the investigated period (1951–1999), temperature trend analyses have experienced a downward trend in the maximum surface temperature (about –0.06°C decade–1) and an upward trend in the minimum surface temperature (about 0.23°C decade–1). Cooling tendency in maximum temperature is spatially more pronounced in inland stations compared to coastal stations. At the seasonal scale, maximum temperature cooling is more obvious in winter and spring, meanwhile minimum temperature warming is more pronounced in summer and fall. In accordance with global trends, the surface mean temperature has moderately risen at an average rate of 0.09°C decade–1. However, this trend has shown considerable temporal variability considering a more pronounced upward trend in summer and fall. In conjunction with other regional and global investigations, clear trends towards smaller diurnal range are presented (–0.28°C decade–1).  相似文献   

7.
Temperature variability in Moosonee, Thunder Bay, and Toronto, Ontario, Canada is examined through a day-to-day variability framework. Statistical measures used in this study include standard deviation (SD), day-to-day temperature variability (DTD), DTD/SD ratio (G), change in day-to-day variability (ΔDTD), and threshold measures of 5°C and 10°C. ΔDTD is the difference between day-to-day change in temperature maximum (DTDtmax) and day-to-day change in temperature minimum (DTDtmin). A distinct seasonal trend is reflected in DTD in Moosonee, Thunder Bay, and Toronto, where ΔDTD is greatest during spring. Monthly ΔDTD averages in Toronto, Thunder Bay, and Moosonee are affected by seasonal variation, the lake effect, and the freeze-up of nearby waterbodies. Yearly averages of ΔDTD have significantly increased over the past recent years in Moosonee and Thunder Bay; a continual increase in climate variability may be detrimental to the subsistence lifestyle of those living in these areas.  相似文献   

8.
Variations in the Atlantic meridional overturning circulation (AMOC) between 1979 and 2008 are documented using the operational ocean analysis, the Global Ocean Data Assimilation System (GODAS), at the National Centers for Climate Prediction (NCEP). The maximum AMOC at 40°N is about 16?Sv in average with peak-to-peak variability of 3–4?Sv. The AMOC variations are dominated by an upward trend from 1980 to 1995, and a downward trend from 1995 to 2008. The maximum AMOC at 26.5°N is slightly weaker than hydrographic estimates and observations from mooring array. The dominant variability of the AMOC in 20°–65°N (the first EOF, 51% variance) is highly correlated with that in the subsurface temperature (the first EOF, 33% variance), and therefore, with density (the first EOF, 25% variance) in the North Atlantic, and is consistent with the observational estimates based on the World Ocean Database 2005. The dominant variabilities of AMOC and subsurface temperature are also analyzed in the context of possible links with the net surface heat flux, deep convection, western boundary current, and subpolar gyre. Variation in the net surface heat flux is further linked to the North Atlantic Oscillation (NAO) index which is found to lead AMOC variations by about 5?years. Our results indicate that AMOC variations can be documented based on an ocean analysis system such as GODAS.  相似文献   

9.
A detailed study of long-term variability of winds using 30 years of data from the European Centre for Medium-range Weather Forecasts global reanalysis (ERA-Interim) over the Indian Ocean has been carried out by partitioning the Indian Ocean into six zones based on local wind extrema. The trend of mean annual wind speed averaged over each zone shows a significant increase in the equatorial region, the Southern Ocean, and the southern part of the trade winds. This indicates that the Southern Ocean winds and the southeast trade winds are becoming stronger. However, the trend for the Bay of Bengal is negative, which might be caused by a weakening of the monsoon winds and northeast trade winds. Maximum interannual variability occurs in the Arabian Sea due to monsoon activity; a minimum is observed in the subtropical region because of the divergence of winds. Wind speed variations in all zones are weakly correlated with the Dipole Mode Index (DMI). However, the equatorial Indian Ocean, the southern part of the trade winds, and subtropical zones show a relatively strong positive correlation with the Southern Oscillation Index (SOI), indicating that the SOI has a zonal influence on wind speed in the Indian Ocean. Monsoon winds have a decreasing trend in the northern Indian Ocean, indicating monsoon weakening, and an increasing trend in the equatorial region because of enhancement of the westerlies. The negative trend observed during the non-monsoon period could be a result of weakening of the northeast trade winds over the past few decades. The mean flux of kinetic energy of wind (FKEW) reaches a minimum of about 100?W?m?2 in the equatorial region and a maximum of about 1500?W?m?2 in the Southern Ocean. The seasonal variability of FKEW is large, about 1600?W?m?2, along the coast of Somalia in the northern Indian Ocean. The maximum monthly variability of the FKEW field averaged over each zone occurs during boreal summer. During the onset and withdrawal of monsoon, FKEW is as low as 50?W?m?2. The Southern Ocean has a large variation of about 1280?W?m?2 because of strong westerlies throughout the year.  相似文献   

10.
Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999–2011 as well as moored velocity time series covering the period May 2005–June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.  相似文献   

11.
西南地区臭氧空间分布及变化趋势   总被引：1，自引：0，他引：1  
本文利用2003年1月—2012年12月的MSR2臭氧总量月平均资料对四川盆地(28～31°N,104～106°E)、青藏高原(27～37°N,80～95°E)、云贵高原(23～27°N,98～106°E)3个区域的臭氧总量空间分布及变化趋势进行了对比分析。得到了以下结论,四川盆地常年存在臭氧总量最大值,青藏高原次之,云贵高原最低。在2003—2012年这10 a间西南地区臭氧总量总体呈上升趋势,这同全球臭氧总量近几十年的变化趋势相一致,其中上升趋势云贵高原四川盆地青藏高原。西南地区在这十年间分别出现了臭氧总量最小值年(2008年)和臭氧总量最大值年(2010年),其中青藏高原还出现了一个臭氧总量最小值年(2004年)。就臭氧总量季节变化而言,在2003—2012年10 a间西南地区臭氧总量在春季存在最大值,但是青藏高原的臭氧总量在秋季存在最小值,而四川盆地和云贵高原的臭氧总量在冬季存在最小值。  相似文献   

12.
Daily minimum temperature (Tmin) and maximum temperature (Tmax) data of Huairou station in Beijing from 1960 to 2008 are examined and adjusted for inhomogeneities by applying the data of two nearby reference stations. Urban effects on the linear trends of the original and adjusted temperature series are estimated and compared. Results show that relocations of station cause obvious discontinuities in the data series, and one of the discontinuities for Tmin are highly significant when the station was moved from downtown to suburb in 1996. The daily Tmin and Tmax data are adjusted for the inhomogeneities. The mean annual Tmin and Tmax at Huairou station drop by 1.377°C and 0.271°C respectively after homogenization. The adjustments for Tmin are larger than those for Tmax, especially in winter, and the seasonal differences of the adjustments are generally more obvious for Tmin than for Tmax. Urban effects on annual mean Tmin and Tmax trends are ?0.004°C/10 year and ?0.035°C/10 year respectively for the original data, but they increase to 0.388°C/10 year and 0.096°C/10 year respectively for the adjusted data. The increase is more significant for the annual mean Tmin series. Urban contributions to the overall trends of annual mean Tmin and Tmax reach 100% and 28.8% respectively for the adjusted data. Our analysis shows that data homogenization for the stations moved from downtowns to suburbs can lead to a significant overestimate of rising trends of surface air temperature, and this necessitates a careful evaluation and adjustment for urban biases before the data are applied in analyses of local and regional climate change.  相似文献   

13.
Changes over the twentieth century in seasonal mean potential predictability (PP) of global precipitation, 200 hPa height and land surface temperature are examined by using 100-member ensemble. The ensemble simulations have been conducted by using an intermediate complexity atmospheric general circulation model of the International Center for Theoretical Physics, Italy. Using the Hadley Centre sea surface temperature (SST) dataset on a 1° grid, two 31 year periods of 1920–1950 and 1970–2000 are separated to distinguish the periods of low and high SST variability, respectively. The standard deviation values averaged for the (“Niño-3.4”; 5°S–5°N, 170°W–120°W) region are 0.71 and 1.15 °C, for the periods of low and high SST variability, respectively, with a percentage change of 62 % during December–January–February (DJF). The leading eigenvector and the associated principal component time series, also indicate that the amplitude of SST variations have positive trend since 1920s to recent years, particularly over the El Niño Southern Oscillation (ENSO) region. Our hypothesis states that the increase in SST variability has increased the PP for precipitation, 200 hPa height and land surface temperature during the DJF. The analysis of signal and noise shows that the signal-to-noise (S/N) ratio is much increased over most of the globe, particularly over the tropics and subtropics for DJF precipitation. This occurs because of a larger increase in the signal and at the same time a reduction in the noise, over most of the tropical areas. For 200 hPa height, the S/N ratio over the Pacific North American (PNA) region is increasing more than that for the other extratropical regions, because of a larger percentage increase in the signal and only a small increase in noise. It is also found that the increase in seasonal mean transient signal over the PNA region is 50 %, while increase in the noise is only 12 %, during the high SST variability period, which indicates that the increase in signal is more than the noise. For DJF land surface temperature, the perfect model notion is utilized to confirm the changes in PP during the low and high SST variability periods. The correlation between the perfect model and the other members clearly reveal that the seasonal mean PP changed. In particular, the PP for the 31 years period of 1970–2000 is higher than that for the 31 years period of 1920–1950. The land surface temperature PP is increased in northern and southern Africa, central Europe, southern South America, eastern United States and over Canada. The increase of the signal and hence the seasonal mean PP is coincides with an increase in tropical Pacific SST variability, particularly in the ENSO region.  相似文献   

14.
The characteristics of Southern Cut-off Lows (CoLs) are studied for the period 1979–2008. The systematic identification of CoLs is realized by applying an original automated scheme using mean daily geopotential height and air temperature at 500?hPa NCEP-DOE II Reanalysis data. From closed lows’ trajectories established from the Equator to the polar jet stream, extratropical lows are analyzed and the stage of cut-off is defined as a secluded low presenting a cold core. From 4,843 cases the general CoL features are presented and confirm several previous results such as the geographic distribution which shows that they are more frequent in the latitudinal band contained between 20°S and 45°S and in close proximity to the continents. On a seasonal time scale, CoLs are more numerous from late summer to autumn, with a maximum of frequency in March/April. In winter (June–July–August), they are fewer but deeper than during the rest of the year. In the median domain (~32.5°S), the annual cycle of the frequency is bimodal and present two peaks during transitional seasons. In this zone, the seasonal cycle varies in accordance with the Semiannual Oscillation. Thereby, when the meridional gradient of temperature/pressure is reinforced between mid and high latitudes, CoLs are more frequent in the median domain. Over the period 1979–2008, the annual CoLs’ frequency exhibits a positive trend of about 25%. This increase is associated with a widening of the latitudinal domain of occurrence equatorward as well as poleward. The trend is linked with an abrupt positive shift in the number of CoLs’ generation between 1998 and 1999. The geographical distribution of CoLs frequency varies significantly in accordance with El Ni?o Southern Oscillation with more CoL’s at lower (higher) latitudes during La Ni?a (El Ni?o) events, principally in the Southern Pacific.  相似文献   

15.
新疆吉木萨尔县45年气候变化特征分析   总被引：6，自引：1，他引：6  
傅玮东  姚艳丽  李迎春 《气象》2007,33(6):96-101
利用吉木萨尔县1961-2005年历年日平均气温、最高（低）气温、降水量、日照时数、风速等资料，分析该县45年年际、年代际、四季及近10年的气候变化特征。得出：（1）吉木萨尔县45年全年及四季气温变化均呈上升趋势，尤其冬季增温最明显，为0．62℃／10年；且近10年是45年中最暖的时期。（2）45年来平均月最高气温变化不大；而月平均最低气温增温明显，尤其近10年平均月最低气温达45年中的最高。（3）45年全年降水量变化呈增湿趋势，变化倾向率为8．19mm／10年，其中：冬季和夏季降水量呈逐渐增多趋势；而春季和秋季平均降水量则呈缓慢减少的趋势。不同年代际全年和夏季降水量均以1990年代最多，1970年代最少。近10年的年降水量也呈增湿趋势，其中冬季降水量为45年中最多时期；秋季降水量为45年中最少时期。（4）45年中任何时段的日照时数和平均风速变化均呈减少（小）趋势。对当地生态环境的改善和农业经济发展等都有十分重要的意义。  相似文献   

16.
Changes in climatic parameters are often given in terms of global averages even though large regional variability is generally observed. The study of regional tendencies provides not only supplementary conclusions to more large-scale oriented results but is also of particular interest to local policy-makers and resource managers to have detailed information regarding sensible and influential climatic parameters. In this study, changes in precipitation for the Balearic Islands (Spain) have been analyzed using data from 18 rain gauges with complete daily time series during the period 1951–2006 and two additional sites where only monthly totals were available. Tendencies for maximum and minimum 2-m temperatures have also been derived using data from three thermometric stations with daily time series for the period 1976–2006. The thermometric stations are located at the head of the runways in the airports of the three major islands of the archipelago, where urbanization has arguably not had a relevant impact on the registered values. The annual mean temperature in the mid-troposphere and lower stratosphere has also been analyzed using the Balearics radiosonde data for the period 1981–2006. Results show there is a negative tendency for annual precipitation (163 mm per century) with 85% significance on the sign of the trend. An abrupt decrease in mean yearly precipitation of 65 mm is objectively detected in the time series around 1980. Additionally, the analysis shows that light and heavy daily precipitation (up to 4 mm and above 64 mm, respectively) increase their contribution to the total annual, while the share from moderate-heavy precipitations (16–32 mm) is decreasing. Regarding the thermometric records, minimum temperatures increased at a rate of 5.8°C per century during the 31 years and maximum temperatures also increased at a rate of 5.0°C per century, both having a level of statistical significance for the sign of the linear trend above 99%. Temperatures in the mid-troposphere decreased at a rate of ??5.4°C per century while a tendency of ??7.8°C per century is found in the lower stratosphere. The level of statistical significance for the sign of both the tropospheric and stratospheric linear trends is above 98% despite the great inter-annual variability of both series.  相似文献   

17.
中国北极村气候变暖特征   总被引：2，自引：1，他引：1  
利用我国最北部的北极村气象站1963～2005年气温资料,通过计算气候倾向率和气候趋势系数,对该地区气候变化特点进行了分析。结果表明,43年来北极村气温有明显并稳定的上升趋势,年平均气温以每10年0．46℃幅度升高。各季及逐月平均气温都存在不同程度的变暖趋势,但是冬季升温最为剧烈,达每10年0．69℃,其中2月升温幅度为每10年1．02℃,为全年最大。秋季升温最弱,仅为每10年0．21℃。年平均最低气温（每10年0．59℃）和年极端最低气温（每10年0．74℃）比年平均最高气温（每10年0．37℃）和年极端最高气温（每10年0．27℃）升温幅度明显偏大。最低气温比最高气温对平均气温的年代际升温趋势贡献更为明显。  相似文献   

18.
利用1951—2010年大连市气温资料,采用气候趋势系数和气候倾向率、Mann-Kendal1突变分析等方法对年和季平均气温、最高最低气温变化特征进行了分析和突变检验。结果表明：大连市年和季平均气温呈上升趋势,进入21世纪,升温趋势有所减缓;大连市年平均气温的增温速率为0.33/10 a,明显高于近50 a中国平均增温...  相似文献   

19.
1951—2010年大连市气温变化特征   总被引：1，自引：0，他引：1  
利用1951—2010年大连市气温资料,采用气候趋势系数和气候倾向率、Mann-Kendal1突变分析等方法对年和季平均气温、最高最低气温变化特征进行了分析和突变检验。结果表明：大连市年和季平均气温呈上升趋势,进入21世纪,升温趋势有所减缓;大连市年平均气温的增温速率为0.33/10 a,明显高于近50 a中国平均增温速率0.22/10 a,更高于近50 a全球平均0.13/10 a的增温速率。大连市平均气温的升高主要发生在春季和冬季;年平均最低气温的升温幅度大于年平均最高气温的升温幅度;年、季平均气温存在突变,突变始于1987—1990年前后,突变前后平均气温均值相差较大;年、季平均最高气温和最低气温大都存在突变,但秋季平均最高气温无突变。  相似文献   

20.
Mountain ecosystems have been projected to experience faster rates of warming than surrounding lowlands. These changes in climatic conditions could have significant impacts on high-altitude Andean environments, affecting the quality and magnitude of their economic and environmental services. Even though long-term data in these regions are limited, it is important to identify any discernible long-term trends in local climatic conditions. Time series of several variables were analyzed to detect statistically significant long-term linear trends that occurred over recent years in a páramo ecosystem of the Colombian Central Andes. Records included cloud characteristics, sunshine, rainfall, minimum and maximum temperatures, diurnal temperature range, and relative humidity. Conditions of atmospheric stability were also explored. Total sunshine exhibited decreasing trends ranging from ?3.7 to ?8.5% per decade at altitudes around the pluviometric optimum. The strongest changes in sunshine occurred during the December-January-February season. Mean relative humidity observed at altitudes around and below this threshold showed increasing trends of +0.6 to +0.7% per decade. Annual rainfall and mean relative humidity above the optimum showed decreasing trends ranging from ?7 to ?11% per decade and from ?1.5 to ?3.6% per decade, respectively. Minimum temperatures on the coldest days and maximum temperatures on the warmest days exhibited increasing trends at all altitudes ranging from +0.1 to +0.6, and from +0.2 to +1.1°C per decade, respectively. Increases in minimum and maximum temperatures at higher altitudes were significantly greater than those observed in average at lower altitudes. The strongest changes in minimum temperatures, particularly, occurred during the December–January–February and June–July–August dry seasons. All these changes suggest that atmospheric conditions in the area are shifting from statically unstable conditions to conditionally unstable or statically stable conditions. Observed historical trends indicate that climate impacts and other human activities have stressed these unique and fragile environments.  相似文献   

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