Accelerated climate change and its potential impact on Yak herding livelihoods in the eastern Tibetan plateau

The Tibetan Plateau has experienced rapid warming like most other alpine regions. Regional assessments show rates of warming comparable with the arctic region and decreasing Asian summer monsoons. We used meteorological station daily precipitation and daily maximum and minimum temperature data from 80 stations in the eastern Tibetan Plateau of southwest China to calculate local variation in the rates and seasonality of change over the last half century (1960–2008). Daily low temperatures during the growing season have increased greatly over the last 24 years (1984–2008). In sites of markedly increased warming (e.g., Deqin, Yunnan and Mangya, Qinghai), daily and growing season daily high temperatures have increased at a rate above 5 °C/100 years. In Deqin, precipitation prior to the 1980s fell as snow whereas in recent decades it has shifted to rain during March and April. These shifts to early spring rains are likely to affect plant communities. Animals like yaks adapted to cold climates are also expected to show impacts with these rising temperatures. This region deserves further investigation to determine how these shifts in climate are affecting local biodiversity and livelihoods.     

Combined Impact of Climate Change,Cultivar Shift,and Sowing Date on Spring Wheat Phenology in Northern China

Distinct climate changes since the end of the 1980 s have led to clear responses in crop phenology in many parts of the world. This study investigated the trends in the dates of spring wheat phenology in relation to mean temperature for different growth stages. It also analyzed the impacts of climate change, cultivar shift, and sowing date adjustments on phenological events/phases of spring wheat in northern China(NC).The results showed that significant changes have occurred in spring wheat phenology in NC due to climate warming in the past 30 years. Specifically, the dates of anthesis and maturity of spring wheat advanced on average by 1.8 and 1.7 day(10 yr)~(-1). Moreover, while the vegetative growth period(VGP) shortened at most stations, the reproductive growth period(RGP) prolonged slightly at half of the investigated stations. As a result, the whole growth period(WGP) of spring wheat shortened at most stations. The findings from the Agricultural Production Systems Simulator(APSIM)-Wheat model simulated results for six representative stations further suggested that temperature rise generally shortened the spring wheat growth period in NC.Although the warming trend shortened the lengths of VGP, RGP, and WGP, the shift of new cultivars with high accumulated temperature requirements, to some extent, mitigated and adapted to the ongoing climate change. Furthermore, shifts in sowing date exerted significant impacts on the phenology of spring wheat.Generally, an advanced sowing date was able to lower the rise in mean temperature during the different growth stages(i.e., VGP, RGP, and WGP) of spring wheat. As a result, the lengths of the growth stages should be prolonged. Both measures(cultivar shift and sowing date adjustments) could be vital adaptation strategies of spring wheat to a warming climate, with potentially beneficial effects in terms of productivity.     

Detecting climate change signals in Saudi Arabia using mean annual surface air temperatures

Climate change signals in Saudi Arabia are investigated using the surface air temperature (SAT) data of 19 meteorological stations, well distributed across the country. Analyses are performed using cumulative sum, cumulative annual mean, and the Mann–Kendall rank statistical test for the period of 1978–2010. A notable change in SAT for the majority of stations is found around 1997. The results show a negative temperature trend (cooling) for all stations during the first period (1978–1997), followed by a positive trend (warming) in the second period (1998–2010) with reference to the entire period of analysis. The Mann–Kendall test confirms that there is no abrupt cooling at any station during the analysis period, reflecting the warming trend across the country. The warming trend is found to be 0.06 °C/year, while the cooling trend is 0.03 °C/year, which are statistically significant.     

Climate change affecting temperature and aridity zones: a case study in Eastern Inner Mongolia, China from 1960–2008

Recent climate change is substantially affecting the spatial pattern of geographical zones, and the temporal and spatial inconsistency of climatic warming and drying patterns contributes to the complexity of the shifting of temperature and aridity zones. Eastern Inner Mongolia, China, located in the interface region of different biomes and ecogeographic zones, has experienced dramatic drying and warming over the past several decades. In this study, the annual accumulated temperature above 10 °C (AAT10) and the aridity index, two key indicators in geographical regionalization, are used to assess warming and drying processes and track the movements of temperature and aridity zones from 1960 to 2008. The results show a significant warming at the regional level from 1960 to 2008 with an AAT10 increase rate of 7.89 °C·d/year (p?<?0.001) in Eastern Inner Mongolia, while the drying trend was not significant during this period. Spatial heterogeneity of warming and drying distributions was also evident. Analysis of warming and drying via piecewise regression revealed two separate, specific trends between the first 31 years (1960–1990) and the subsequent 18 years (1991–2008). Generally, mild warming and very slight wetting occurred prior to 1990, while after 1991 both warming and drying were significant and enhanced. Continuous warming drove a northward shift of temperature zones from the 1960s to 2000s, while aridity zones displayed enhanced temporal and spatial variability. Climate change effects on temperature and aridity zones imply that the patterns of cropping systems, macro-ecosystems, and human land use modes are potentially undergoing migration and modification due to climate change.     

Combined impact of climate change,cultivar shift,and sowing date on spring wheat phenology in Northern China

Distinct climate changes since the end of the 1980s have led to clear responses in crop phenology in many parts of the world. This study investigated the trends in the dates of spring wheat phenology in relation to mean temperature for different growth stages. It also analyzed the impacts of climate change, cultivar shift, and sowing date adjustments on phenological events/phases of spring wheat in northern China (NC). The results showed that significant changes have occurred in spring wheat phenology in NC due to climate warming in the past 30 years. Specifically, the dates of anthesis and maturity of spring wheat advanced on average by 1.8 and 1.7 day (10 yr)^?1. Moreover, while the vegetative growth period (VGP) shortened at most stations, the reproductive growth period (RGP) prolonged slightly at half of the investigated stations. As a result, the whole growth period (WGP) of spring wheat shortened at most stations. The findings from the Agricultural Production Systems Simulator (APSIM)-Wheat model simulated results for six representative stations further suggested that temperature rise generally shortened the spring wheat growth period in NC. Although the warming trend shortened the lengths of VGP, RGP, and WGP, the shift of new cultivars with high accumulated temperature requirements, to some extent, mitigated and adapted to the ongoing climate change. Furthermore, shifts in sowing date exerted significant impacts on the phenology of spring wheat. Generally, an advanced sowing date was able to lower the rise in mean temperature during the different growth stages (i.e., VGP, RGP, and WGP) of spring wheat. As a result, the lengths of the growth stages should be prolonged. Both measures (cultivar shift and sowing date adjustments) could be vital adaptation strategies of spring wheat to a warming climate, with potentially beneficial effects in terms of productivity.     

Variability of maximum and mean average temperature across Libya (1945–2009)

Spatial and temporal variability in daily maximum and mean average daily temperature, monthly maximum and mean average monthly temperature for nine coastal stations during the period 1956–2009 (54 years), and annual maximum and mean average temperature for coastal and inland stations for the period 1945–2009 (65 years) across Libya are analysed. During the period 1945–2009, significant increases in maximum temperature (0.017 °C/year) and mean average temperature (0.021 °C/year) are identified at most stations. Significantly, warming in annual maximum temperature (0.038 °C/year) and mean average annual temperatures (0.049 °C/year) are observed at almost all study stations during the last 32 years (1978–2009). The results show that Libya has witnessed a significant warming since the middle of the twentieth century, which will have a considerable impact on societies and the ecology of the North Africa region, if increases continue at current rates.     

近50年来辽宁省冻土的时空变化特征

利用辽宁省61个气象站1964—2013年的冻土观测资料,采用线性回归、相关性分析、不同气候期对比等方法,结合ArcGIS分析了辽宁省冻土的空间和时间变化特征。结果表明:辽宁省冻土随纬度呈带状分布;土壤冻结具有明显的季节变化特征,冻结期在10月至翌年5月,冬末春初冻结的面积和深度达到最大值;冻结日自北向南逐渐推迟,消融日则相反;在全球变暖背景下,冻土深度随温度的上升而减小;大部分地区年平均气温和地表温度与最大冻土深度呈显著负相关,是影响冻土深度的重要因素;从各气候期100cm等深度线也可以明显看出最大冻土深度呈逐渐减小趋势。     

气候增暖对广东省植物物候变化的影响

根据广东省气象观测资料和10个农业气象观测站的物候观测资料,分析了1982~2004年温度变化对广东省木本植物物候变化的影响,并建立了物候期差异与温度之间的关系模式,分析了当前气候增暖背景下物候期对温度变化的响应关系。结果表明:平均温度上升,木本植物春季物候期提前;平均温度下降,木本植物春季物候期推迟。物候期的提前与推迟对温度的上升与下降的响应是非线性的。在同等升降温幅度情况下,降温导致的物候期推迟幅度较升温导致的物候期提前幅度大。     

Using urban effect corrected temperature data and a tree phenology model to project geographical shift of cherry flowering date in South Korea

Temperate zone deciduous tree phenology may be vulnerable to projected temperature change, and associated geographical impact is of concern to ecologists. Although many phenology models have been introduced to evaluate climate change impact, there has been little attempt to show the spatial variation across a geographical region due to contamination by the urban heat island (UHI) effect as well as the insufficient spatial resolution of temperature data. We present a practical method for assessing climate change impact on tree phenology at spatial scales sufficient to accommodate the UHI effect. A thermal time-based two-step phenological model was adapted to simulate and project flowering dates of Japanese cherry (Prunus serrulata var. spontanea) in South Korea under the changing climates. The model consists of two sequential periods: the rest period described by chilling requirements and the forcing period described by heating requirements. Daily maximum and minimum temperature are used to calculate daily chill units until a pre-determined chilling requirement for rest release is met. After the projected rest release date, daily heat units (growing degree days) are accumulated until a pre-determined heating requirement for flowering is achieved. Model parameters were derived from the observed bud-burst and flowering dates of cherry tree at the Seoul station of the Korea Meteorological Administration (KMA), along with daily temperature data for 1923–1948. The model was validated using the observed data at 18 locations across South Korea during 1955–2004 with a root mean square error of 5.1 days. This model was used to project flowering dates of Japanese cherry in South Korea from 1941 to 2100. Gridded data sets of daily maximum and minimum temperature with a 270 m grid spacing were prepared for the climatological normal years 1941–1970 and 1971–2000 based on observations at 56 KMA stations and a geospatial interpolation scheme for correcting urban heat island effect as well as elevation effect. We obtained a 25 km-resolution, 2011–2100 temperature projection data set covering peninsular Korea under the auspices of the Inter-governmental Panel on Climate Change—Special Report on Emission Scenarios A2 from the Meteorological Research Institute of KMA. The data set was converted to 270 m gridded data for the climatological years 2011–2040, 2041–2070 and 2071–2100. The phenology model was run by the gridded daily maximum and minimum temperature data sets, each representing climatological normal years for 1941–1970, 1971–2000, 2011–2040, 2041–2070, and 2071–2100. According to the model calculation, the spatially averaged flowering date for the 1971–2000 normal is earlier than that for 1941–1970 by 5.2 days. Compared with the current normal (1971–2000), flowering of Japanese cherry is expected to be earlier by 9, 21, and 29 days in the future normal years 2011–2040, 2041–2070, and 2071–2100, respectively. Southern coastal areas might experience springs with incomplete or even no flowering caused by insufficient chilling required for breaking bud dormancy.     

Onset of the summer monsoon over the southern Vietnam and its predictability

The summer monsoon onset over southern Vietnam is determined through a new criterion based on both in situ daily rainfall at six selected stations provided by the Institute of Meteorology and Hydrology, Vietnam, and the zonal component of the wind at 1,000 hPa from the National Center for Environmental Prediction/Department of Energy Reanalysis 2. Over the period 1979–2004, the summer monsoon onset mean date is on 12 May, with a standard deviation of 11.6 days. The temporal and spatial structures of the atmospheric conditions prevailing during the onset period are detailed. Clear changes are seen in the zonal wind (strengthened over the Bay of Bengal and changed from negative to positive over South Vietnam) and in convection (deeper), in association with an intensification of the meridional gradients of sea level pressure at 1,000 hPa and of moist static energy at 2 m over Southeast Asia. The predictability of onset dates is then assessed. Cross-validated hindcasts based upon four predictors linked to robust signals in the atmospheric dynamics are then provided. They are highly significant when compared to observations (56% of common variance). Basically, late (early) onsets are preceded in March–April by higher (lower) sea level pressure over the East China Sea, stronger (weaker) southeasterly winds over southern Vietnam, decreasing (increasing) deep convection over the Bay of Bengal, and the reverse situation over Indonesia (120–140°E, 0–10°S).     

Trends in temperature and rainfall extremes in the Yellow River source region, China

Spatial and temporal changes in daily temperature and rainfall indices are analyzed for the source region of Yellow River. Three periods are examined: 1960–1990, 1960–2000 and 1960–2006. Significant warming trends have been observed for the whole study region over all the three periods, particularly over the period 1960–2006. This warming is mainly attributed to a significant increase in the minimum temperature, and characterized by pronounced changes in the low temperature events composing a significant increase in the magnitude and a significant decrease in the frequency. In contrast to the temperature indices, no significant changes have been observed in the rainfall indices at the majority of stations. However, the rainfall shows noticeable increasing trends during winter and spring from a basin-wide point of view. Conversely, the frequency and contribution of moderately heavy rainfall events to total rainfall show a significant decreasing trend in summer. To conclude, this study shows that over the past 40–45 years the source region of the Yellow River has become warmer and experienced some seasonally varying changes in rainfall, which also supports an emerging global picture of warming and the prevailing positive trends in winter rainfall extremes over the mid-latitudinal land areas of the Northern Hemisphere.     

On the relationship between Indian monsoon withdrawal and Iran’s fall precipitation onset

Indian monsoon is the most prominent of the world’s monsoon systems which primarily affects synoptic patterns of India and adjacent countries such as Iran in interaction with large-scale weather systems. In this article, the relationship between the withdrawal date of the Indian monsoon and the onset of fall precipitation in Iran has been studied. Data included annual time series of withdrawal dates of the Indian monsoon prepared by the Indian Institute for Tropical Meteorology, and time series of the first date of 25 mm accumulated precipitation over Iran’s synoptic weather stations in a 10-day period which is the basis for the cultivation date. Both time series were considered in Julian calendar with the starting date on August 1. The studied period is 1960–2014 which covers 55 years of data from 36 meteorological stations in Iran. By classifying the withdrawal dates of the Indian monsoon in three stages of late, normal, and early withdrawals, its relation with the onset of fall precipitation in western, southwestern, southern, eastern, central, and northern regions of Iran was studied. Results demonstrated that in four out of the six mentioned regions, the late withdrawal of the Indian monsoon postpones the onset of fall precipitation over Iran. No significant relation was found between the onset of fall precipitation in central region of Iran and the monsoon’s withdrawal date. In the western, southwestern, southern, and eastern regions of Iran, the late monsoon delays the onset of fall’s precipitation; while in the south Caspian Sea coastal area, it causes the early onset of autumnal precipitation. The lag in onset of fall precipitation in Iran which is coordinated with the late withdrawal of monsoon is accompanied with prolonged subtropical high settling over Iran’s plateau that prevents the southward movement of polar jet frontal systems. Such conditions enhance northerly wind currents over the Caspian Sea which, in turn, increase the precipitation in Caspian coastal provinces, which has a different behavior from the overall response of Iran’s climate to the late withdrawal of monsoon. In the phase of early monsoon withdrawal, the subtropical jet is located at the 200 hPa level in 32.5° north latitude; compared with the late withdrawal date, it shows a 2° southward movement. Additionally, the 500 hPa trough is also located in the Eastern Mediterranean, and the MSL pressure anomaly is between ? 4 to ? 7 hPa. The Mediterranean trough in the late withdrawal phase is located in its central zones. It seems that the lack of significant correlation between late withdrawal date of Indian monsoon and late fall’s precipitation onset in the central region of Iran depends on three reasons:1. Lack of adequate weather stations in central region of Iran.2. Precipitation standard deviations over arid and warm regions are high.3. Central flat region of Iran without any source of humidity is located to the lee side of Zagros mountain range. So intensification or development of frontal systems is almost prohibited over there.     

气候变暖对宁夏引黄灌区春小麦生产的影响

 对宁夏引黄灌区10个观测站1961-2004年春小麦生长发育期（3月上旬至7月上旬）的气温进行分析,结果表明：宁夏引黄灌区春小麦生长期的气候明显变暖。t检验结果表明,春小麦生长发育期日平均气温的突变发生在1989年,突变后的气温比突变前升高了0.7℃。在春小麦生长发育各阶段,气温都有所升高,但没有超出春小麦生长发育的适宜温度范围。引黄灌区春小麦的温度敏感系数在3月中旬至4月上旬及5月上旬至6月上旬为正值,这两个时段的气候变暖有利于春小麦生产;6月中旬至7月上旬及4月中下旬温度敏感系数为负值,这两个时段的气候变暖不利于春小麦生产。总体而言,气候变暖对春小麦单产的贡献为-2.6%。     

Trend analysis of long-term temperature time series in the Greater Toronto Area (GTA)

As the majority of the world’s population is living in urban environments, there is growing interest in studying local urban climates. In this paper, for the first time, the long-term trends (31–162 years) of temperature change have been analyzed for the Greater Toronto Area (GTA). Annual and seasonal time series for a number of urban, suburban, and rural weather stations are considered. Non-parametric statistical techniques such as Mann–Kendall test and Theil-Sen slope estimation are used primarily for the assessing of the significance and detection of trends, and the sequential Mann test is used to detect any abrupt climate change. Statistically significant trends for annual mean and minimum temperatures are detected for almost all stations in the GTA. Winter is found to be the most coherent season contributing substantially to the increase in annual minimum temperature. The analyses of the abrupt changes in temperature suggest that the beginning of the increasing trend in Toronto started after the 1920s and then continued to increase to the 1960s. For all stations, there is a significant increase of annual and seasonal (particularly winter) temperatures after the 1980s. In terms of the linkage between urbanization and spatiotemporal thermal patterns, significant linear trends in annual mean and minimum temperature are detected for the period of 1878–1978 for the urban station, Toronto, while for the rural counterparts, the trends are not significant. Also, for all stations in the GTA that are situated in all directions except south of Toronto, substantial temperature change is detected for the periods of 1970–2000 and 1989–2000. It is concluded that the urbanization in the GTA has significantly contributed to the increase of the annual mean temperatures during the past three decades. In addition to urbanization, the influence of local climate, topography, and larger scale warming are incorporated in the analysis of the trends.     

气候变暖对宁夏引黄灌区春小麦生产的影响

对宁夏引黄灌区10个观测站1961-2004年春小麦生长发育期（3月上旬至7月上旬）的气温进行分析,结果表明：宁夏引黄灌区春小麦生长期的气候明显变暖。t检验结果表明,春小麦生长发育期日平均气温的突变发生在1989年,突变后的气温比突变前升高了0.7℃。在春小麦生长发育各阶段,气温都有所升高,但没有超出春小麦生长发育的适宜温度范围。引黄灌区春小麦的温度敏感系数在3月中旬至4月上旬及5月上旬至6月上旬为正值,这两个时段的气候变暖有利于春小麦生产;6月中旬至7月上旬及4月中下旬温度敏感系数为负值,这两个时段的气候变暖不利于春小麦生产。总体而言,气候变暖对春小麦单产的贡献为-2.6%。     

Predicting the time of green up in temperate and boreal biomes

Direct observations as well as Normalized Difference Vegetation Index (NDVI) data from satellites have shown earlier leaf appearance in the northern hemisphere, which is believed to result from climate warming. The advance of leaf out to earlier times in the year could be limited or even reversed, however, as temperate and boreal trees require a certain amount of chilling in winter for rapid leaf out in spring. If this chilling requirement is not fulfilled, an increasing amount of warming is required. Implications of these chilling requirements at the biome level are not clear. One approach to estimate their importance is to generalize the exponential relationships between chilling and warming established for single species. Previous work using NDVI data suggests that this is indeed feasible but much has been limited to specific biomes or a very few years of data for the modelling. We find chilling requirements for northern temperate and boreal biomes by fitting various phenology models to green-up dates determined from NDVI using various methods and 12 years of data. The models predict that in northern middle and high latitudes the advance of green-up will be limited to a total of 4 to 5 days on average (but up to 15 days regionally) over the time period 2000–2060 as estimated using two contrasting climate simulations. This results from the exponentially increasing warming requirements for leaf out when winter chilling falls below a threshold as shown by a comparison with models that consider only spring warming. The model evaluation suggests an element of regional adaptation of the warming required for leaf out in large biomes.     

内蒙古地区采暖期变化特征及预测方法

利用内蒙古地区58个站点1961—2008年逐日平均气温资料,用数理统计等分析方法,参照采暖供热等相关规范,综合分析了内蒙古地区采暖期各要素变化特征,初步提出了采暖初日、终日和采暖期能源需求预测模型,并经过检验与实况基本相符。结果表明:①近48年内蒙古地区采暖初日推后、终日提前、采暖期缩短,说明随着气候变暖,内蒙古地区冬季变暖,寒冷期缩短。②内蒙古地区采暖期要素的变化与纬度的高低密切相关。纬度越高,采暖期缩短越多,使表征采暖能耗多少的采暖度日值减少越明显,采暖期能源消耗越少,节能减排潜力越大。③随着气候变暖,内蒙古地区冬季寒冷程度和寒冷期变短,采暖能源需求量减少,采暖能耗降低,其集中供热强度和耗热量降低,从而可减少CO_2、CH_4、SO_2等温室气体的排放强度。④采暖起止日、采暖长度以及采暖期能源需求与气温变化密切相关。由此构建的采暖初日、终日和能源需求预测模型,可信度较高,可根据月动力延伸预报产品,提早做出不同地区采暖起止日期和采暖期能源需求趋势预测,减少能源的浪费,为供热部门科学决策提供参考。     

Linking two centuries of tree growth and glacier dynamics with climate changes in Kamchatka

Glaciers around the world retreated as the climate warmed substantially. For the majority of alpine and arctic areas, however, the lack of meteorological data over a long period makes it difficult to build long-term climate and glacial fluctuation relationships, emphasizing the importance of natural proxy archives. Here we use the 230-year record of stem radial growth of birch trees (Betula ermanii) from the treeline forests above the receding glaciers in eastern maritime Kamchatka to analyse temporal variations of climate as well as glacial advance and retreat. Glaciers in Kamchatka Peninsula represent the southern limit of glaciation in far eastern Eurasia, which makes them prone to global warming. Using instrumental climate data (1930–1996) from local meteorological stations, we find that the July temperature had most prominent positive impact on birch growth. On the contrary, smaller ring increments are associated with the positive summer and net annual ice mass balance of Koryto Glacier. The prevailing trend of higher summer temperatures and lower snowfall over the past 70 years has enhanced tree growth while causing the glacier’s surface to lower by about 35 m and its front to retreat by about 490 m. Assuming these same relationships between climate, tree growth, and glacier mass balance also existed in the past, we use tree rings as a proxy record of climatically induced temporary halts in the glacier’s retreat over the past two centuries, which in total was over 1,000 m. Both direct observations and tree ring proxies indicate several prolonged warm periods (1990s, 1960s, 1930–1940s, 1880–1900s) interspersed with cooler periods (1984–1985, 1970–1976, 1953–1957, 1912–1926, 1855–1875, 1830–1845, 1805–1820 and 1770–1780) when the glacier re-advanced, creating several consecutive terminal moraine ridges. We conclude that birch tree-rings are suitable for assessing tree growth/climate/glacial relationships over a longer timescale in maritime Kamchatka.     

Frost-free season lengthening and its potential cause in the Tibetan Plateau from 1960 to 2010

Frost-free season was an important index for extreme temperature, which was widely discussed in agriculture and applied meteorology research. The frost-free season changed, which was associated with global warming in the past few decades. In this study, the changes in three indices (the last frost day in spring, the first frost day in autumn, and the frost-free season length) of the frost-free season were investigated at 73 meteorological stations in the Tibetan Plateau from 1960 to 2010. Results showed that the last frost day in spring occurred earlier, significantly in 39 % of the 73 stations. For the regional average, the last frost day in spring occurred earlier, significantly at the rate of 1.9 days/decade during the last 50 years. The first frost day in autumn occurred later, significantly in 31 % of the stations, and the regional average rate was 1.5 days/decade from 1960 to 2010. The changing rate of the first frost day in autumn below 3,000 m was 1.8 times larger than the changing rate above 3,000 m. In addition, the first frost day in autumn above 3,000 m fluctuated dramatically before the early 1990s and then it was later sharply after the early 1990s. The frost-free season length increased significantly at almost all stations in the Tibetan Plateau from 1960 to 2010. For the regional average, the frost-free season lengthened at the rate of 3.1 days/decade. The changing rate of the frost-free season length below 3,000 m was more significant than the changing rate above 3,000 m. Eight indices of large-scale atmospheric circulation were employed to investigate the potential cause of the frost-free season length change in the Tibetan Plateau during the past 50 years. There was a significant relationship between the frost-free season length and the Northern Hemisphere Polar Vortex indices. The weakening cold atmospheric circulation might be an essential factor to the Tibetan Plateau warming since 1960.     

近50年我国探空温度序列均一化及变化趋势

利用1958—2005年我国116个站探空温度序列研究了我国高空温度变化趋势。首先通过静力学质量控制和两相回归法对原始序列进行了均一化处理。我国探空温度序列存在明显的间断点, 间断点的订正对于序列的趋势影响较为显著。缺测率是影响我国探空温度序列应用性的重要因子, 也是区域平均趋势统计中台站取舍的指标, 减少台站总数会削弱我国对流层升温和平流层降温的变化趋势。分析表明: 70%作为最小资料有效率标准最为合理。为满足最小资料有效率, 选取92个站统计我国高空温度变化趋势的区域平均值。结果表明: 1958-2005年, 平流层下层和对流层上层降温, 对流层中、低层升温; 高空温度变化趋势与研究时段明显相关, 1958-1978年我国高空大气整层均为降温; 1979—2005年, 对流层中低层升温最为明显, 增暖的幅度随高度增加而减小, 400 hPa以上各层转为降温。对流层的升温始于20世纪80年代, 升温幅度与全球尺度的平均值有所不同。