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1.
Extreme temperatures around flowering of wheat have the potential to reduce grain yield and at farm scale their impact can be spatially variable depending on topography. Twenty-five data loggers were installed at 0.8-m height across a 164-ha farm in the southern Mallee of Victoria, Australia to spatially record the daily course of temperatures around the average date of flowering of wheat in the region. The experiment was conducted during 2-years period. In 1 year, the farm had no crop cover and in another year the farm had a wheat crop. Multiple linear regression analysis techniques were used to fit models relating daily extreme temperatures to the farm topographic features of elevation, aspect and slope, and the average maximum and minimum temperatures of each day at the farm in order to identify areas of high risk of extreme temperatures around the time of the flowering of wheat. The fitted regression models explained 90% and 97% of the variability in maximum and minimum temperatures, respectively, when the farm had no crop cover and 80% and 94% of the variability in maximum and minimum temperatures, respectively, when the farm had a wheat crop cover. When the farm had no crop, only minimum temperature was partially explained by the topography however, both maximum and minimum temperatures were partially explained by the topography when the farm had a wheat crop. From this study it was concluded that, (1) high temperature variations were found across the farm (2) temperature variations were only partially explained from the developed model presumably due to the flatter topography of the farm and (3) the relationships obtained from this study could be used in a crop model which can explain variation in grain yield based on the topography of a field. 相似文献
2.
RECENT TRENDS IN TREE-RING RECORDS FROM HIGH ELEVATION SITES IN THE ANDES OF NORTHERN PATAGONIA 总被引：12，自引：0，他引：12
RICARDO VILLALBA JOSE A. BONINSEGNA THOMAS T. VEBLEN ANDREA SCHMELTER SIGFRIDO RUBULIS 《Climatic change》1997,36(3-4):425-454
A new set of tree-ring records from the Andes of northern Patagonia, Argentina (41° S) was used to evaluate recent (i.e., last 250 years) regional trends in tree growth at upper treeline. Fifteen tree-ring chronologies from 1200 to 1750 m elevation were developed for Nothofagus pumilio, the dominant subalpine species. Samples were collected along three elevational transects located along the steep west-to-east precipitation gradient from the main Cordillera (mean annual precipitation >4000 mm) to an eastern outlier of the Andes (mean annual precipitation >2000 mm). Ring-width variation in higher elevation tree-ring records from the main Cordillera is mainly related to changes in temperature and precipitation during spring and summer. However, the response to climatic variation is also influenced by local site factors of elevation and exposure. Based on the relationships between Nothofagus growth and climate, we reconstructed changes in snow cover duration in late spring and variations in mean annual temperature since A.D. 1750. Abrupt interannual changes in the mean annual temperature reconstruction are associated with strong to very strong El Niño-Southern Oscillation events. At upper treeline, tree growth since 1977 has been anomalously high. A sharp rise in global average tropospheric temperatures has been recorded since the mid-1970s in response to an enhanced tropical hydrologic cycle due to an increase in temperature of the tropical Pacific. Temperatures in northern Patagonia have been anomalously high throughout the 1980s, which is consistent with positive temperature anomalies in the tropical Pacific and along the western coast of the Americas at c.a. 40° S latitude. Our 250-year temperature reconstruction indicates that although the persistently high temperatures of the 1980s are uncommon during this period, they are not unprecedented. Tropical climatic episodes similar to that observed during the 1980s may have occurred in the recent past under pre-industrial carbon dioxide levels. 相似文献
3.
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
4.
Jaak Jaagus Agrita Briede Egidijus Rimkus Kalle Remm 《Theoretical and Applied Climatology》2014,118(1-2):57-68
Spatial distribution and trends in mean and absolute maximum and minimum temperatures and in the diurnal temperature range were analysed at 47 stations in the eastern Baltic region (Lithuania, Latvia and Estonia) during 1951–2010. Dependence of the studied variables on geographical factors (latitude, the Baltic Sea, land elevation) is discussed. Statistically significant increasing trends in maximum and minimum temperatures were detected for March, April, July, August and annual values. At the majority of stations, the increase was detected also in February and May in case of maximum temperature and in January and May in case of minimum temperature. Warming was slightly higher in the northern part of the study area, i.e. in Estonia. Trends in the diurnal temperature range differ seasonally. The highest increasing trend revealed in April and, at some stations, also in May, July and August. Negative and mostly insignificant changes have occurred in January, February, March and June. The annual temperature range has not changed. 相似文献
5.
Michael A. Wulder Trisalyn A. Nelson Chris Derksen David Seemann 《Climatic change》2007,82(1-2):113-130
Twenty-four winter seasons (1978–2002) of mean February snow water equivalent (SWE) values were analyzed in an exploration of the spatial pattern of temporal variability in snow cover across the non-mountainous interior of Canada. The SWE data were derived from space-borne passive microwave brightness temperatures processed with a land cover-sensitive suite of algorithms. Spatial patterns in the frequency and amount of variability were investigated on an annual basis through comparisons with average trends over all 24 years. Changes in temporal variability through time were also investigated by comparing three eight year time periods to general trends. Analyses were synthesized at the ecozone scale in order to link results both to potential land cover influences on algorithm performance and climatological variability in SWE. Prairie and northern ecozones were typically found to be the most variable in terms of SWE magnitude. Analyses indicate that non-treed land cover classes are generally more variable than treed classes. The results also indicate that extreme weather events appear to be occurring with increasing consistency in the Prairie and Arctic regions. Discerning climatologically significant variability in the time series, compared to algorithm-related issues can be a challenge, but in an era of eroding surface observing networks the passive microwave time series represents an important resource for monitoring and detecting trends and variability in terrestrial snow cover. 相似文献
6.
利用建站以来鞍山站和海城乡村站的一日四次观测数据和逐日平均、最低和最高气温资料,对1951-2017年鞍山市年、四季和各月平均气温和极端气温变化特征及其变率进行了分析,并对鞍山城市热岛变化进行探讨。结果表明：1951-2017年鞍山市年平均最低气温的递增趋势最强、平均气温次之、平均最高气温最弱,且均通过显著性检验。1951-2017年鞍山市年极端最高气温变化呈弱递减趋势,1951-1987年（突变前）呈递减趋势、1988-2017年（突变后）为递增趋势。1951-2017年鞍山市年极端最低气温呈显著递增趋势,1951-1987年（突变前）较整个阶段递增趋势更强,1988-2017年（突变后）呈递减趋势;突变前后极端最高和极端最低气温呈反相变化特征。1958-2017年鞍山市年最低气温的城市热岛强度最大、平均气温次之,最高气温最小、递增趋势最弱;秋、冬季鞍山城市热岛强度较其他季节更强,热岛指数递增显著;在每日4次定时气温观测中,14时鞍山市热岛强度最小,热岛指数呈递减趋势,其余时次均呈显著递增趋势,其中,02时鞍山热岛强度最强;鞍山市平均气温变化呈显著增暖趋势,城市热岛强度和热岛指数均呈显著递增,夜间递增尤为突出,说明鞍山城市热岛的显著增强是鞍山市气候变暖的一个主要原因。 相似文献
7.
2011年深圳人体舒适度空间分布特征及影响因子分析 总被引：2，自引：0，他引：2
利用深圳多个区域自动气象站资料,采用考虑了气温、风速、相对湿度等要素的人体舒适度计算方案,计算了深圳地区的人体舒适度指数以及不同舒适等级天数,分析了城市地形地貌、路网密度和人口密度等因素对人体舒适度的影响。结果表明：深圳地区沿海比内陆舒适,全市全年舒适天数为7-9个月,夏季感觉热的天数约为2-3个月,冬季感觉冷的天数大部分地区为30 d左右。从不同地区人体舒适度指数的日变化特征来看,夏季比冬季更易受地理位置和下垫面等因素影响。地形地貌、海陆分布、城市规划等地理因素对人体舒适度均有一定影响,相关分析表明海拔高度、道路占地面积和人口密度与热-炎热日数呈对数关系。但在深圳的东部人口稀疏和道路占地较小地区也并非舒适宜人,也会出现较多炎热天气,这与该地区年平均风速相对微弱有直接关系。 相似文献
8.
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
9.
César N. Caviedes 《Climatic change》1990,16(1):99-114
Palynological, geomorphological, and relict vegetation evidence point to the existence of cooler and more humid conditions along semiarid and temperate Chile during the Pleistocene. Departing from an actualistic model, and utilizing a regression technique that includes significant independent variables on the basis of R
2 and F statistics, the best fit multivariable model was produced for annual rainfall and snowline elevation. Predicted values for rainfall are obtained by controlling sea surface temperatures and air temperatures (the most significant variables in the model) at different latitudes. A variation of only 1 °C of the winter sea and air temperatures induces more than a doubling of the annual precipitation in north-central Chile, and increases by nearly fifty percent in southern Chile. Entering the predicted values of precipitation and lowering the winter temperatures by 1 or 2 °C produces a slight depression of the snowline in semiarid north-central Chile and a significant descent in southern Chile. The predicted depression of the snowline coincided well with geomorphological evidence of glacial advances and fossil periglacial phenomena in the Andes. Cooling and increased precipitation during the Pleistocene pluvial elicited northward shifts of the temperate rainforest of southern Chile in the order of 7 deg latitude. 相似文献
10.
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12.
合肥市53年气温变化特征分析 总被引：5，自引：1，他引：4
利用1953-2005年安徽省合肥市逐日平均气温、最高气温和最低气温资料,应用最小二乘法和Morlet小波分析法,对合肥市温度变化进行了分析。结果表明,合肥市53a来年平均气温、年平均最高气温和年平均最低气温变化,均具有明显冷期和暖期交替的阶段性特点,而且冷期持续时间比暖期持续时间长;春季、秋季和冬季年平均气温均呈上升趋势,但增幅不同,冬季最大,春季次之,秋季最小,而夏季气温呈微弱的下降趋势;年极端最高气温呈微弱的下降趋势,年极端最低气温则呈强烈的上升趋势;年热积温呈下降趋势,年冷积温则呈明显的上升趋势;年平均气温、年平均最高气温和年平均最低气温变化具有明显的周期性,均存在30a左右的大尺度周期振荡,而中小尺度周期振荡则不相同。 相似文献
13.
应用均一化逐日气象观测资料,分析了北京地区1960—2008年气候变暖及主要极端气温指数的统计特征。结果表明：近49年来北京年平均气温增温速率约为0.39℃/10a,最高、最低气温变化具有明显的非对称性。霜冻日数和气温年较差呈现下降趋势,暖夜指数及热浪指数呈现上升趋势,除气温年较差外,其他极端气温指数的气候变率均在加大。北京年平均气温及极端气温指数主要存在21年、15～17年及准10年周期特征。年平均气温与极端气温指数之间存在较强相关性,气候变暖突变发生前后某些极端气温指数发生频率表现出明显差异。自1980年起,北京市区极端最高气温及其增温率明显高于近郊和远郊,高温日数市区多于近郊,近郊多于远郊;近、远郊极端最低气温温差高于城、近郊温差。 相似文献
14.
B. Geerts 《Theoretical and Applied Climatology》2002,73(3-4):107-132
Summary ?This is a sequel to a study of the empirical estimation of the annual-mean temperature at any location on land, using only
geographical information – latitude, elevation, distance from the nearer ocean shore at the same latitude – and coastal sea-surface
temperature. Here long-term mean station data and NCAR/NCEP (National Center for Atmospheric Research/National Centers for
Environmental Prediction) global re-analysis data are used to describe and estimate spatial patterns of annual range of monthly-mean temperatures. The two key influences on annual range are the latitude and the distance from the upwind shore.
Secondary factors include mountain barriers, shape of the local topography, elevation, and vicinity to large bodies of water.
An empirical relationship is derived, based on the two key factors alone, assuming zonal winds and adjustments for the effects
of mountain barriers and for the proximity to a sea to the north or south. An independent test of this relationship yields
errors around 1.0 K. The range estimates yield January and July average temperatures when combined with annual-mean temperatures.
Such estimates also carry an uncertainty of about 1.0 K. The procedure can be inverted, i.e. knowledge of the annual mean
and range can be used to infer location.
Received August 23, 2001; accepted June 17, 2002 相似文献
15.
Biogeophysical effects of historical land cover changes simulated by six Earth system models of intermediate complexity 总被引：12，自引：0，他引：12
V. Brovkin M. Claussen E. Driesschaert T. Fichefet D. Kicklighter M. F. Loutre H. D. Matthews N. Ramankutty M. Schaeffer A. Sokolov 《Climate Dynamics》2006,26(6):587-600
Six Earth system models of intermediate complexity that are able to simulate interaction between atmosphere, ocean, and land
surface, were forced with a scenario of land cover changes during the last millennium. In response to historical deforestation
of about 18 million sq km, the models simulate a decrease in global mean annual temperature in the range of 0.13–0.25°C. The
rate of this cooling accelerated during the 19th century, reached a maximum in the first half of the 20th century, and declined
at the end of the 20th century. This trend is explained by temporal and spatial dynamics of land cover changes, as the effect
of deforestation on temperature is less pronounced for tropical than for temperate regions, and reforestation in the northern
temperate areas during the second part of the 20th century partly offset the cooling trend. In most of the models, land cover
changes lead to a decline in annual land evapotranspiration, while seasonal changes are rather equivocal because of spatial
shifts in convergence zones. In the future, reforestation might be chosen as an option for the enhancement of terrestrial
carbon sequestration. Our study indicates that biogeophysical mechanisms need to be accounted for in the assessment of land
management options for climate change mitigation. 相似文献
16.
The role of terrestrial snow cover in the climate system 总被引：2，自引：0，他引：2
Steve Vavrus 《Climate Dynamics》2007,29(1):73-88
Snow cover is known to exert a strong influence on climate, but quantifying its impact is difficult. This study investigates
the global impact of terrestrial snow cover through a pair of GCM simulations run with prognostic snow cover and with all
snow cover on land eliminated (NOSNOWCOVER). In this experiment all snowfall over land was converted into its liquid–water
equivalent upon reaching the surface. Compared with the control run, NOSNOWCOVER produces mean-annual surface air temperatures
up to 5 K higher over northern North America and Eurasia and 8–10 K greater during winter. The globally averaged warming of
0.8 K is one-third as large as the model’s response to 2 × CO2 forcing. The pronounced surface heating propagates throughout the troposphere, causing changes in surface and upper-air circulation
patterns. Despite the large atmospheric warming, the absence of an insulating snow pack causes soil temperatures in NOSNOWCOVER
to fall throughout northern Asia and Canada, including extreme wintertime cooling of over 20 K in Siberia and a 70% increase
in permafrost area. The absence of snow melt water also affects extratropical surface hydrology, causing significantly drier
upper-layer soils and dramatic changes in the annual cycle of runoff. Removing snow cover also drastically affects extreme
weather. Extreme cold-air outbreaks (CAOs)—defined relative to the control climatology—essentially disappear in NOSNOWCOVER.
The loss of CAOs appears to stem from both the local effects of eliminating snow cover in mid-latitudes and a remote effect
over source regions in the Arctic, where −40°C air masses are no longer able to form. 相似文献
17.
Scenarios indicate that the air temperature will increase in high latitude regions in coming decades, causing the snow covered
period to shorten, the growing season to lengthen and soil temperatures to change during the winter, spring and early summer.
To evaluate how a warmer climate is likely to alter the snow cover and soil temperature in Scots pine stands of varying ages
in northern Sweden, climate scenarios from the Swedish regional climate modelling programme SWECLIM were used to drive a Soil-Vegetation-Atmosphere
Transfer (SVAT)-model (COUP). Using the two CO2 emission scenarios A and B in the Hadley centres global climate model, HadleyA and HadleyB, SWECLIM predicts that the annual
mean air temperature and precipitation will increase at most 4.8°C and 315 mm, respectively, within a century in the study
region. The results of this analysis indicate that a warmer climate will shorten the period of persistent snow pack by 73–93 days,
increase the average soil temperature by 0.9–1.5°C at 10 cm depth, advance soil warming by 15–19 days in spring and cause
more soil freeze–thaw cycles by 31–38%. The results also predict that the large current variations in snow cover due to variations
in tree interception and topography will be enhanced in the coming century, resulting in increased spatial variability in
soil temperatures. 相似文献
18.
Record-breaking extreme temperatures have been measured in the last two decades all over Turkey, with recent studies detecting positive trends in extreme temperature time series. In this study, nonstationary extreme value analysis was performed on extreme temperature time series obtained from fifty stations scattered over the seven geographical regions of Turkey. Basic characterization of the data set was defined through outlier detection, homogeneity, trend detection, and stationarity tests. Trend-including non-stationary extreme temperature time series were analyzed with non-stationary Generalized Extreme Value distribution. Three main physical drivers were considered as the leading causes that trigger the observed trends in extreme temperatures over Turkey: time, teleconnection patterns of the Arctic Oscillations, and those of the North Atlantic Oscillations. The results showed that most of the absolute annual minimum and maximum temperature time series are inhomogeneous while the possible breakpoints date back to the1970s and 1990s, respectively. More than half of the absolute annual maximum time series (26/50 and many of the absolute annual minimum time series (21/50) showed a positive trend. No negative trend was detected in the extreme temperature time series. Based on the frequency analysis of the 21 annual maximum time series, the non-stationary estimations of 50-year return levels were detected to be higher than in the stationary model (between 0.44 °C and 3.73 °C). The return levels in 15 of the 20 minimum temperature time series increased from 0.11 °C up to 12.28 °C. Elevation increases the nonstationarity impact on absolute minimum temperatures and decreases it on absolute maximums. The findings in this study indicate that the consideration of non-stationarity in extreme temperature time series is a necessity during return level estimations over the study area. 相似文献
19.
Earth surface temperatures are changing worldwide together with the changes in the extreme temperatures. The present study investigates trends and variations of monthly maximum and minimum temperatures and their effects on seasonal fluctuations at different climatological stations of Maharashtra and Karnataka states of India. Trend analysis was performed on annual and seasonal mean maximum temperature (TMAX) and mean minimum temperature (TMIN) for the period 1969 to 2006. During the last 38 years, an increase in annual TMAX and TMIN has occurred. At most of the locations, the increase in TMAX was faster than the TMIN, resulting in an increase in diurnal temperature range. At the same time, annual mean temperature (TM) showed a significant increase over the study area. Percentiles were used to identify extreme temperature indices. An increase in occurrence of warm extremes was observed at southern locations, and cold extremes increased over the central and northeastern part of the study area. Occurrences of cold wave conditions have decreased rapidly compared to heat wave conditions. 相似文献
20.
Summary We have examined station data from around the world to study the separate effects of the latitude (between 60° N–40° S),
elevation and distance inland, on the annual-mean screen temperature. In the first 200–400 km from some west coasts, screen
temperatures (after adjustment for elevation) rise inland, reaching a maximum called the ‘thermal-ridge temperature’ Tr. The
rise of temperature within this littoral fringe (of width F) depends mainly on the difference between the sea-surface temperature
off the west coast and the zonal mean. Further inland than such a fringe, adjusted temperatures generally decline eastwards,
approximately linearly, at a rate C. The rate is related to hemisphere and latitude.
Empirical relationships between latitude and the observed coastal sea-surface temperature, the near-shore screen temperature,
Tr, C and F for each continent are used to estimate annual mean temperatures on land. Independent estimates of this kind for
48 places, using a look-up table, differ overall by only 0.7 K from the actual long-term average annual mean temperatures.
This is less than half the error resulting from an assumption of zonal-mean temperatures. Basing estimates on coastal sea-surface
temperatures, instead of the look-up table, results in an average error of 1.0 K for the 48 places. The errors are comparable
with the standard deviation of annual mean temperatures during 30 years or so.
Received March 6, 2001 Revised July 30, 2001 相似文献