1970-2015年秦岭南北气温时空变化及其气候分界意义

基于秦岭南北70个气象站点观测资料,辅以极点对称模态分解方法（ESMD）,对秦岭南北近期气温时空变化特征进行分析,进而以日平均温≥ 10 ℃积温天数为主要指标,以1月0 ℃等温线变化为辅助指标,探讨秦岭山脉的气候分界意义。结果表明：① 1970-2015年秦岭南北气温变化具有同步性,呈现出“非平稳、非线性、阶梯状”的增暖过程,变化阶段可分为：1970-1993年为低位波动期、1994-2002年为快速上升期、2003-2015年为增温停滞期;② ESMD信息分解结果表明,秦岭南北气温变化以年际波动为主导,并未呈现出明显的线性增暖趋势;③ 在空间上,秦岭南北气温趋势呈现“同步增温,南北分异”的响应特征,即秦岭以北地区空间增温具有一致性,秦岭以南地区则呈现“西乡—安康盆地交界”、“商丹盆地”两个低值中心;④ 在气候变暖背景下,秦岭作为气候分界线的作用依然明显,但是南北响应方式存在差异。其中,秦岭以南,北亚热带北界沿山地“垂直上升”,汉江谷地热量资源逐年增加;秦岭以北,尽管以城市带为中心的增温区不断延展,但是冷月气温偏低的格局并未改变。     

北纬地区温度和卫星监测的植被活动节律变化的比较分析(英文)

Plant growth at northern latitudes is highly responsive to the climatic changes that have occurred over recent decades. However, the sensitivity of the phasing of the seasonal cycle of terrestrial ecosystems to a changing environment remains less widely understood. We present an investigation and comparative study of large-scale changes in seasonal cy-cling of both land surface temperature and plant growth. Our results have shown trends in-dicating a marked increased towards overall plant productivity by ~3% from 1982 to 2005, reduced trends in seasonal variation at low-mid latitudes by ~2%, increased trends in sea-sonal variations at mid-high latitudes by ~7%, and an earlier phase in northern terrestrial ecosystems (~1.1 days) in parallel with changes in the phasing of surface temperatures at northern latitudes over the 24 years in this study. These shifts in annual cycles of terrestrial vegetation appear to have a distinct geographical zonality and are dependent upon latitudinal changes in climatic variables. More conspicuous changes in overall vegetation productivity and the seasonal phase of ecosystems have been observed in Eurasia compared to North America, largely because of a more rapid rise in temperature. Our results state that changing climate boosts plant growth at northern latitudes, but also alters the phase and seasonal variations of the annual cycle of terrestrial ecosystems.     

Two centuries of temperature variation and volcanic forcing reconstructed for the northern Tibetan Plateau

Abstract

The northern Tibetan Plateau has been subject to recent warming far above the global average. With few instrumental climate records available for this region before the 1950s, paleoclimatic reconstructions must be used to understand annual-to-centennial-scale climate variations and local climate response to large-scale forcing mechanisms. We developed a maximum latewood density chronology of Qinghai spruce (Picea crassifolia) from the southern slope of the Qilian Mountains, northern Tibetan Plateau. Based on the chronology, we reconstructed August–September temperature for 1780–2008. The temperature reconstruction model accounts for 39.7% of instrumental temperature variance from 1957 to 2008, successfully capturing the most recent warming. Superposed epoch analysis indicated a volcanic forcing for temperature, resulting in pulses of cooler conditions that can persist for 2–4 years. Tree-ring data indicated that warm-dry and cold-wet climate combinations mainly occurred in northern Tibetan Plateau before CE 1900, and revealed a clear wetting and warming trend since the 1980s. Our study provides long-term perspective on recent climate change in northern Tibetan Plateau to guide expectations of future climate variability and aid sustainable development, and provides scenarios for climate change adaptation and inputs for climate models representing a broader range of conditions than those of historical climate records.     

Geomorphological evidence for late Holocene climatic change in northern Australia

The hypothesis that the late Holocene climate of northern Australia has been characterised by periods of reduced rainfall has been examined by constructing a detailed chronostratigraphy of climatically sensitive geomorphological sites, in particular dunefields and lake deposits. There is clear evidence of aridity during the last glacial period (c. 18,000 BP), and disturbance of coastal deposits by rising sea level until 5500 BP. Following the flooding of the shallow Sunda and Sahul shelves, the climate of northern Australia appears to have become increasingly variable with an arid trend interrupted by periods of increased rainfall between 3500 and 2800 BP, again between 2100 and 1600 BP and possibly twice during the last 1000 years. It is proposed that the dry episodes are associated with persistent, large‐scale sinking, dry south‐easterly flows over the Australian tropics inhibiting the onset of the north Australian monsoon. These are similar to flows associated with present‐day ENSO events. The pattern suggests that ENSO may be associated with a larger process which may not have begun to operate until the flooding of the shallow Sunda and Sahul shelves and the opening of the Indonesian throughflow between the Pacific and Indian oceans.     

隆冬异常升温北疆积雪提前融化

2007年1月下旬中期开始,新疆北部地区出现了一次异常的升温天气过程,1月27日~2月4日的9d中,北疆各地的43个气象站中,有14站的日最高气温突破同期历史极值,其中伊犁河谷的新源的日最高气温上升到13.3℃,突破同期历史极值3.0℃;有19站的9天平均气温突破同期历史极值,占总站数的44.2%。1月下旬本是新疆北部的积雪稳定积累期,但是2007年元月下旬异常升温天气的出现和持续,使北疆地区积雪提前融化,到2月初,北疆的博尔塔拉蒙古自治州、伊犁地区、乌鲁木齐市等地的积雪面积明显减少,乌鲁木齐地区的积雪覆盖度仅为25.84%,比15年同期平均值偏少5成。冬季是新疆增温幅度最大的季节,在气候变暖背景下,冬季极端天气气候事件的出现也越来越频繁,隆冬季节的异常升温造成气温偏高,使北疆地区的积雪提前融化。这些变化将对新疆水资源的时空分布产生重大影响,对当地生态环境将带来难以估测的影响。在全球气候变化背景下,更加需要加强对新疆等干旱地区极端天气气候事件的监测分析及其对生态环境、经济社会发展的影响等诸多领域的研究,使社会各界以积极的态度来科学客观地认识气候变化带来的后果,及早提出应对区域气候变化的对策,采取切实可行的措施减缓气候变化带来的负面影响。     

Ground temperature variation and its response to climate change on the northern Tibetan Plateau

Ground temperature plays a significant role in the interaction between the land surface and atmosphere on the Tibetan Plateau(TP). Under the background of temperature warming, the TP has witnessed an accelerated warming trend in frozen ground temperature, an increasing active layer thickness, and the melting of underground ice. Based on high-resolution ground temperature data observed from 1997 to 2012 on the northern TP, the trend of ground temperature at each observation site and its response to climate change were analyzed. The results showed that while the ground temperature at different soil depths showed a strong warming trend over the observation period, the warming in winter is more significant than that in summer. The warming rate of daily minimum ground temperature was greater than that of daily maximum ground temperature at the TTH and MS3608 sites. During the study period, thawing occurred earlier, whereas freezing happened later, resulting in shortened freezing season and a thinner frozen layer at the BJ site. And a zero-curtain effect develops when the soil begins to thaw or freeze in spring and autumn. From 1997 to 2012, the average summer air temperature and precipitation in summer and winter from six meteorological stations along the Qinghai-Tibet highway also demonstrated an increasing trend, with a more significant temperature increase in winter than in summer. The ground temperature showed an obvious response to air temperature warming, but the trend varied significantly with soil depths due to soil heterogeneity.     

Deep permafrost boreholes in western Svalbard,northern Sweden and southern Norway

The first deep permafrost boreholes (>10 m) ever drilled in Scandinavia for climatic studies constitute part of a transect of deep mountain permafrost boreholes through the mountains of Europe established under the EU PACE (Permafrost and Climate in Europe) Project. In Scandinavia, PACE boreholes are located at Juvvasshøe, southern Norway, Tarfalaryggen in northern Sweden, and northernmost in the transect at Janssonhaugen, western Svalbard. This paper outlines the aims and objectives of the PACE programme, and describes in detail the Svalbard and Scandinavian permafrost boreholes.     

Recent air temperature changes in the permafrost landscapes of northeastern Eurasia

In the last two decades, climatic change has resulted in increased cryogenic activity in northeastern Eurasia, with adverse consequences for landscapes and socio-economic systems in the permafrost zone.The main purpose of this study was to assess the recent phases of warming, starting with Arctic warming. We performed a spatiotemporal analysis of climatic conditions during phases of maximum warming (i.e., 1935–1945, 1988–1995, and 2005–2009) in northeastern Eurasia and compared the magnitude of warming and its effect on permafrost among these critical periods. Our observations of permafrost landscape dynamics confirmed that the last two warming phases have played major roles in changing the environment.Data analysis has revealed regional patterns in the intensity of warming. Areas south of 60–62° latitude experienced no rise in air temperature during the Arctic warming period (1935–1945), whereas during 1988–1995, the center of warming shifted to the south of northeastern Eurasia. The last phase of warming (2005–2009) was characterized by maximum values of mean annual air temperature and the thawing index, and a decrease in the freezing index throughout northeastern Eurasia.     

Statistic-empirical modelling of mountain permafrost distribution in the Abisko region,sub-Arctic northern Sweden

The mountain permafrost distribution in the Abisko region in northern Sweden has been assessed using a combination of empirical and statistical analysis. The empirical data was obtained using the bottom temperature of snow cover (BTS) method, supported by continuous ground temperature measurements. The statistical analysis was based on 148 data points in total and used logistic regression to model the probability of permafrost occurrence. Further, Geographically Weighted Regression (GWR) was introduced as an exploratory tool for detecting non-stationarity in the relationships between permafrost and the independent variables models and showed to be a useful tool in the statistical analysis. As a result of the GWR analysis the region was divided into two subregions. The models show probabilities >0.8 for permafrost at elevations above 1300 m a.s.l. in the western part of the region. In the eastern part, the probabilities are likely to be influenced by the potential incoming shortwave summer radiation, indicating a probability >0.8 above 850 m a.s.l. on the north-east and east-facing slopes, above 1000 m on the west-facing slopes and above 1100 m a.s.l. on the south-facing slopes. Permafrost conditions throughout the region were found to be marginal and sensitive to current warming trends.     

Morphology and geotechnique of active-layer detachment failures in discontinuous and continuous permafrost, northern Canada

Fifty active-layer detachment failures triggered after forest fire in the discontinuous permafrost zone (central Mackenzie Valley, 65° N.) are compared to several hundred others caused by summer meteorological triggers in continuous permafrost (Fosheim Peninsula, Ellesmere Island, 80°N). Most failures fall into compact or elongated morphological categories. The compact type occur next to stream channels and have little internal disturbance of the displaced block, whereas the elongated types can develop on any part of the slope and exhibit greater internal deformation. Frequency distributions of length-to-width and length-to-depth ratios are similar at all sites. Positive pore pressures, expected theoretically, were measured in the field at the base of the thawing layer. Effective stress analysis could predict the instability of slopes in both areas, providing cohesion across the thaw plane was set to zero and/or residual strength parameters were employed. The location of the shear planes or zones in relation to the permafrost table and the degree of post-failure secondary movements (including headwall recession and thermokarst development within the failure track) differed between the localities, reflecting dissimilarity in the environmental triggers and in the degree of ground thermal disturbance.     

Warming but not thawing of the cold permafrost in northern Alaska during the past 50 years

Climate warming has not resulted in measurable thawing of the cold (-5°C to -10°C) permafrost in northern Alaska during the last half century. The maximum depths of summer thaw at five locations near Barrow, Alaska, in 2005 were within the ranges of the depths obtained at those same locations during the early 1950s. However, there has been a net warming of about 2°C, after a cooling of 0.4°C during 1953-1960, at the upper depths of the permafrost column at two of the locations. Thawing of permafrost from above (increase in active layer thickness) is determined by the summer thawing index for the specific year; any warming, or cooling, of the upper permafrost column results from the cumulative effect of changes in the average annual air temperatures over a period of years, assuming no change in surface conditions. Theoretically, thawing from the base of permafrost should be negligible even in areas of thin (about 100-200 m) permafrost in northern Alaska. The reported shoreline erosion along the northern Alaska coast is a secondary result from changes in the adjacent ocean ice coverage during the fall stormy period, and is not directly because of any "thawing" of the permafrost.     

A study of diurnal variation of the electromagnetic field in northern France using ancient recordings

Summary. From 1883 to 1901 magnetic elements were continuously recorded at the French Saint-Maur observatory. From 1893 to 1895, Earth potentials along two 15 km long orthogonal lines were also recorded. Moreover, from 1884 to 1885, Blavier,'Ingénieur des Télégraphes', used several some hundred kilométre long telegraphic lines to measure and record Earth potentials. Using this set of data we will study the daily variations of the telluric and magnetic fields and the way according to which these two fields are correlated.
The observed magnetotelluric tensor is antisymmétric when the long telluric lines are considered. It is not the case for the short lines. But, making use of a correction derived from the formalism developed by Le Mouel & Menvielle in the static distortion approximation, one can derive an impedance whose phase is equal to the phase of the impedance derived from the long line data.     

1960-2013年秦岭陕西段南北坡极端气温变化空间差异

作为气候变化研究的重要内容,极端气温研究对生态环境保护和灾害事件预警具有重要意义。根据1960-2013年秦岭32个气象站点的逐日气温资料,采用RClimDex软件、克里格插值法、线性倾向估计法和相关性分析法,研究秦岭山地陕西段（简称秦岭）气温的空间分布特点,以及极端气温的空间变化特征。结果表明：① 1960-2013年秦岭年平均气温、年最高气温和年最低气温分别为10.48 ℃、16.44 ℃和6.18 ℃;秦岭北坡气温在低海拔区高于南坡,在中、高海拔区低于南坡;南北坡的气温差值在低海拔区域最小,中海拔区域最大。② 秦岭极端气温的频率、强度和持续时间均表现为增加趋势,极端气温变化的敏感区域位于南坡的镇安、柞水和北坡的周至、户县。③ 秦岭北坡极端气温频率的变化更明显,秦岭南坡极端气温强度和持续时间的变化更明显;且北坡的增温主要发生在夜间,南坡的增温主要发生在白昼。④ 秦岭极端气温的变暖速率随海拔升高而增大,高海拔区域极端气温频率和强度的变化最明显,中海拔区域极端气温持续时间的变化最明显。     

Palaeolimnological evidence for recent climatic change in lakes from the northern Urals, arctic Russia

The recent sediments from two deep arctic lakes, Mitrofanovskoe and Vanuk-ty, situated in the permafrost belt within the Bolshezemelskaya Tundra in the northern Ural region, were studied for diatoms, chironomids, spheroidal carbonaceous particles and stable lead isotopes. The magnitudes and rates-of-change in diatom and chironomid assemblages were numerically estimated. Instrumental climate records were used to assess statistically the amount of variance in diatom and chironomid data explained by temperature. August and September air temperatures have a statistically significant effect on diatom composition at both lakes. At Mitrofanovskoe Lake, major compositional changes in diatom and chironomid assemblages occurred at the turn of the 20th century and might be related to the regional increase in temperature. Chironomid-inferred air temperature also increased by approximately 1 °C since the early 1900s. At both lakes diatom compositional changes, coincident with the increase in June and September temperatures, also occurred in the late 1960s. These compositional changes are correlated with the increase in diatom production, sediment organic content and diatom species richness, and are likely to be a diatom response to the lengthening of the growing season. These changes are also correlated with the circum-Arctic temperature increase from the 1960s. A chironomid response to the late 1960s temperature increase was less pronounced at both lakes. Pollution levels are relatively low and pollution history is unrelated to ecological changes. Both lead isotopes and spheroidal carbonaceous particles show a clear atmospheric pollution signal, peaking in the 1980s.     

The climatic signal in varved sediments from Lake C2, northern Ellesmere Island, Canada

Annually-laminated clastic sediments preserve a high resolution proxy record of paleoclimate, provided that allochthonous sedimentation represents a response to meteorological forcing of watershed sediment transfer. Here, we demonstrate this linkage, and illustrate a calibration process using the most recent 40 years of a varve record from Lake C2 (82°50 N; 78°00 W), three years of field measurements, and meteorological data for 1951–92 from nearby AES weather station Alert. Field measurements were used to correlate proxies of the energy available for snowmelt (e.g. air temperature) and daily suspended sediment discharge (SSQ). Our calibration was extended through use of weather data from Alert. Both mean daily air temperature at Echo, and daily SSQ, were well correlated with air temperature at 600 m above Alert, as obtained from the 1200 Z (0800 LST) rawinsonde sounding. Accordingly, we used pooled 1990 and 1992 Alert 600 m data to predict the lagged daily sediment discharge into Lake C2 (adj. r ²=0.43). Daily values were summed each year in order to produce an annual series of predicted sediment transfer to the lake. The original varve chronology was based on eight sediment cores recovered from the deep basin of the lake (>80 m). Although low-frequency fluctuations of the varve and predicted SSQ series agree, slight tuning of the varve record optimizes the correlation between them. Adjustments were based on examination of weather data for specific years, reexamination of sediment core thin sections, and by aligning fluctuations in the two series which closely matched. Although the original chronology is reasonably well correlated with 600 m temperatures at Alert (for JJA mean, r=0.41, significant at 0.01), the adjusted chronology is both better correlated and contains a more precise climate signal (r=0.54 for July mean, significant at 0.01). This is the first calibrated varve record produced from Arctic lake sediments, and demonstrates that varves from Lake C2 contain a paleoclimatic record. We believe the post-facto manipulations required to produce the adjusted varve chronology are reasonable given the uncertainties inherent in varve counting, and the lack of any independent corroborating chronostratigraphic markers.This is the ninth in a series of papers published in this issue on the Taconite Inlet Lakes Project. These papers were collected by Dr R. S. Bradley.     

新疆冬季气温年际异常的主模态及其成因分析

基于新疆1961—2016年89个观测站冬季平均气温经验正交分解的空间模态,讨论了与各空间模态及其相联系的北半球中高纬度环流特征,结果表明：新疆冬季平均气温的年际异常空间模态分为全区一致类、南北反相类、东西反相类,根据这三类空间模态的正负位相不同分别分为一致偏冷型、一致偏暖型、北冷南暖型、北暖南冷型、东冷西暖型和东暖西冷型等6个空间分布型。新疆冬季平均气温各空间分布型的环流影响因子既表现了极地和中纬度环流相互作用,也有纬圈方向的波列传播的影响。当北半球中纬度西风偏弱,中高纬度环流经向度加大,乌拉尔山地区的高压脊发展和东亚大槽偏深,50°N以南为负高度距平,新疆冬季平均气温一致偏低;反之则一致偏高。北冷南暖型在40°N以北的区域与一致偏冷型的环流特征基本类似,但在中亚至新疆40°N偏南的区域位势高度偏高;北暖南冷型出现时,乌拉尔山负高度距平和东亚大槽偏弱,新疆上空为浅脊控制,新疆南部受脊后的浅槽影响。东冷西暖型和东暖西冷型区别在于中纬度的500 hPa正高度距平中心的位置和700 hPa气流方向。北极涛动（AO）、区域西风指数、乌拉尔山关键区因子、欧亚纬向环流指数、西藏高原-1指数、西藏高原-2指数、斯堪的纳维亚遥相关型指数(SCA)、亚洲区极涡面积指数等8个气候指数都对新疆冬季平均气温产生了重要的影响。