Temperature and thermal growing season variations along elevational gradients on a sub-alpine,temperate China

Fully and accurately studying temperature variations in montane areas are conducive to a better understanding of climate modeling and climate-growth relationships on regional scales. To explore the spatio-temporal changes in air and soil temperatures and their relationship in montane areas, on-site monitoring over 2 years (2015 and 2016) was conducted at nine different elevations from 2040 to 2740 m a.s.l. on Luya Mountain in the semiarid region of China. The results showed that the annual mean of air temperature lapse rate (ATLR) was 0.67 °C/100 m. ATLR varied obviously in different months within a range of 0.57~0.79 °C/100 m. The annual mean of the soil temperature lapse rate (STLR) was 0.48 °C/100 m. Seasonally, monthly mean soil temperature did not show a consistent pattern with regard to elevation. The relationships between air and soil temperatures showed piecewise changes. Soil was decoupled from the air temperature in cold winter and early spring. The parameters of the growing season based on the two temperature types had no corresponding relations, and seasonal mean of soil temperature showed the smallest value at mid-elevation rather than in the treeline ecotone. Based on these changes, our results emphasized that altitudinal and seasonal variability caused by local factors (such as snow cover and soil moisture) should be taken into full consideration in microclimate extrapolation and treeline prediction in montane areas, especially in relation to soil temperature.     

Twentieth-century trends in the thermal growing season in the Greater Baltic Area

Phenological data have shown an increase of ca. 10 days in European growing season length in the latter part of the twentieth century. In general, these changes have been associated with global warming. Here we present a study of thermal growing season (GS) trends in the Greater Baltic Area, northern Europe. Yearly dates for the start, end and length of the GS were computed for 49 stations in the studied area, using daily mean temperature measurements. Trends and tendencies of the GS parameters were analysed within the twentieth century. We also examined GS trends in long records (starting before 1850) from the region. The results show a general increase of the length of the GS of ca one week since 1951 in the area, where the most considerable change has occurred in spring (starting ∼6 days earlier). The largest increases were found at stations adjacent to the Baltic Sea and North Sea, where some Danish stations showed significant increasing trends in the length of the GS of more than 20 days. The only tendency for a shorter GS was found in Archangelsk, north western Russia. The three longest records displayed large inter-annual and decadal variability, with tendencies for increased frequencies of longer growing seasons since the 1950s.     

1960-2009年石羊河流域气候变化特征

利用线性倾向率和Mann-Kendall非参数检验及克里金（Kriging）空间插值法,分析石羊河流域气温、降水量和蒸发量3个气候要素的年代际时空变化特征。结果表明：1960-2009年石羊河流域气温最小增速为0.25 ℃/10 a,高于中国及全球平均增速,且石羊河流域东部地区增温速度大于流域西部;20世纪60年代石羊河流域气温为降低趋势,其他年代流域大部地区均为增温趋势,且这种增温趋势是突变的。石羊河流域各年代及50 a平均降水量流域西部地区均比东部地区增加明显,近50 a石羊河流域降水量的变化趋势大多数未通过显著性检验,流域降水量的变化是由于降水的年际振荡造成的。近50 a石羊河流域大部地区的蒸发量呈先减少后增加的趋势,除民勤外,流域各地区蒸发量的减少或增加均存在突变。石羊河流域气温持续升高和蒸发量增加及二者的协同关系可能导致区域干旱的加剧。     

1960-2010年中国华北东北地区热量资源时空变化

利用1960-2010年华北、东北地区165个气象站日平均气温资料,运用线性倾向估计等方法,对近51 a来≥0 ℃和≥10 ℃积温及其持续天数和起止日期的时、空分布特征进行分析,以了解气候变暖对华北、东北地区热量资源分布的影响。结果表明：近51 a来华北、东北地区气温增暖趋势明显,气候倾向率达0.32 ℃/10 a（P<0.001）,且与各项热量资源指标相关显著。随着气候变暖,≥0 ℃和≥10 ℃积温及持续天数普遍显著增加,其气候倾向率分别在（30 ℃·d）/10 a和2 d/10 a以上;2000年以后亚热带北界和暖温带北界在华北、东北地区均出现了北移,以亚热带北界移动幅度更大;20世纪90年代以后,一年两熟制种植北界在山西和辽宁两省明显北抬,平均移动幅度超过1.5个纬距。华北、东北地区≥0 ℃和≥10 ℃积温及持续天数普遍增加是受起始日期提前和终止日期延后共同影响,≥0 ℃前者比后者的影响更明显,≥10 ℃两者作用相当。     

1960—2009年广西霾日时空变化特征

利用1960—2009年广西80个地面观测站资料,运用EOF、线性倾向估计等统计方法,分析了近50年广西霾日数的时空变化特征。结果表明:近50年广西霾日数总体呈上升趋势,与该地区人类活动和经济发展引起的污染排放增长密切相关;空间分布呈现出主要城市及其周边地区霾日多,边远地区及沿海地区霾日少的特点;广西霾天气主要发生在秋、冬季,以轻微霾 (能见度为5~10 km) 为主,且霾天气发生时的相对湿度8成以上介于70%~90%;除了空气污染之外,近50年风速呈下降趋势可能也导致更多的霾天气。     

1960—2009年辽宁区域性暴雪气候特征

利用1960—2009年辽宁58个测站逐日降水资料,分析了区域性暴雪气候变化特征。结果表明：辽宁区域性暴雪主要出现在每年11月下旬至翌年3月15日,2月为最多月。近50 a区域性暴雪过程次数呈上升趋势,并且存在9、5a和3a的周期变化;9a的周期变化信号一直存在,但强度自20世纪60年代末开始增强,70—80年代最强;5 a的周期变化信号自70年代初期开始出现,强度在70年代中期开始增强;3a的变化信号一直存在,强度在70年代中期、80年代最强。区域性暴雪过程次数和暴雪总量自东南部向西北部逐渐减少,空间分布有3个中心,分别为：沈阳—抚顺—本溪一带、鞍山附近和丹东凤城地区。辽宁区域性暴雪落区主要有4种分布,分别为中东部暴雪型、东部暴雪型、南部暴雪型和西部暴雪型。     

Ranking Regional Drought Events in China for 1960-2009

The spatiotemporal variations of the site and regional droughts in China during 1960–2009 were analyzed by applying a daily composite-drought index (CDI) to 722 stations in mainland China. Droughts frequently happened in a zone extended from Southwest China to the Yellow River, North China, and the southwestern part of Northeast China, with two centers of high frequency in North China and Southwest China. In Southwest and South China, droughts tend to happen during the winter. In North China and along the Y...     

Ranking Regional Drought Events in China for 1960--2009

The spatiotemporal variations of the site and regional droughts in China during 1960–2009 were analyzed by applying a daily composite-drought index (CDI) to 722 stations in mainland China. Droughts frequently happened in a zone extended from Southwest China to the Yellow River, North China, and the southwestern part of Northeast China, with two centers of high frequency in North China and Southwest China. In Southwest and South China, droughts tend to happen during the winter. In North China and along the Yellow River, droughts mainly occur during the winter and during May–June. During the past 50 years, the geographical distribution of site drought events showed high frequencies (0.9–1.3 times per year) in the upper Yellow River basin and North China, comparing with moderate frequencies (0.6–0.9 times per year) in Southwest China and the southwestern part of Northeast China and with lower frequencies over the middle and lower Yangtze River basin. And the frequencies increased over mainland China except for the upper reaches of the Yangtze River. A regional drought (RD) event is a widespread and persistent event that covers at least five adjacent sites and lasts for at least 10 days. There were 252 RD events in the past 50 years—five times per year. Most RD events lasted for <100 days and covered <100 stations, but the longest and largest RD event lasted for 307 days from 6 September 1998 to 9 July 1999 and covered 327 stations from North to Southwest China.     

1960—2009年咸宁市气候变化特征

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

1960-2009年咸宁市气候变化特征分析

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

我国南方地区1960-2009年冬季气温分析

利用1960~2009年我国南方地区277个测站逐日气温资料,通过旋转经验正交函数(REOF)将南方冬季(12月、1月、2月)地区划分成4个区域,采用气候趋势系数、气候倾向率和Mann-kendall(MK)法对日平均气温,日最高气温和日最低气温的时空分布特征进行研究。结果发现:三类气温整体皆自东南往西北方向递减;昼夜温差为减小趋势,减小显著区域为青藏高原、川西高原、川东、江淮地区及沿海局部区域;南方地区冬季整体呈升温趋势,上升趋势最大的为日最低气温0.411℃/10a,其次是日平均气温0.316℃/10a,最小的是日最高气温0.228℃/10a,而上升幅度最大为地形复杂海拔较高的青藏高原、云南和川西地区,其次是沿海地区、长江和黄河中下游地区,升温幅度最小的为川东、贵州、重庆、广西等地,而青海省河南站近50年为降温;日最低气温突变比日平均气温突变发生早,在1990年左右,而突变发生最晚的是日最高气温,在1997~1999年。     

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.     

1960—2005年东北地区降雪变化特征研究

利用国家气象信息中心提供的逐日降水和逐日天气现象台站资料,在运用旋转经验正交函数（Rotated Empirical Orthogonal Function, REOF）和相关分析进行降雪分区的基础上,重点研究了46 a来东北地区降雪的时空分布、演变特征和长期气候趋势。结果表明：东北地区的山地是主要的降雪地区,而平原及平原南部是降雪较少的区域,降雪区域差异明显。在空间上,大兴安岭北部（长白山地区）是降雪增加（减少）最大的地区,小兴安岭地区（平原地区）是降雪增加（减少）较明显的地区。在时间上,东北北区降雪量呈增加趋势,且在20世纪90年代发生了突变,目前增加趋势显著,而东北南区降雪量是减少的。     

2009年黑龙江省主要粮食产区春播农情及气象服务调查

调研采取气象专家与地方气象局领导、农气人员、农业专家、农户面对面访谈的方式,并亲自到田间地头查看,结合当地农委的第一手材料,了解当前粮食主产区的春播开展情况、作物品种分布、土壤墒情、气象为农民服务的方式、满意度.通过调查找准今后气象服务的切入点,达到气象更好的服务于"三农".     

Precipitation fluctuations during the winter season from 1960 to 1995 over Emilia-Romagna, Italy

Summary ?The variability of the winter mean precipitation observed at 40 rainfall stations in Emilia-Romagna (a region in northern Italy) from 1960 to 1995 is examined. The results are compared with those obtained for the whole of Italy using records from 32 stations. Temporal variability of the time series is investigated by means of Mann-Kendall and Pettitt tests, in order to estimate the presence of trends and “change points”. Before analysis the original precipitation data set have been tested to detect the inhomogeneity points, using the Standard Normal Homogeneity Test (SNHT). Almost all stations situated in Emilia Romagna exhibit a significant decreasing trend in winter precipitation during the 1960–1995 period. The same characteristics are revealed, more significant in the northern and central part of the region, when the stations for all Italy are analysed. A significant downward shift in the winter precipitation is detected through the Pettitt test in Emilia Romagna, around 1980 at some stations, while the rest of the stations reveal the shift point occurrence around 1985. A significant downward shift in the winter precipitation is detected around 1985, when analysing the time series for all Italy. Spatial variability of winter precipitation is studied using the Empirical Orthogonal Function. The first pattern indicates that a common large-scale process could be responsible for the winter precipitation variability. The second EOF pattern shows an opposite sign of climate variability, which highlights the influence of relief on the precipitation regime. The time series associated with the first precipitation pattern (PC1) at both scales emphasises a significant decreasing trend and a downward shift point around 1985. The internal structure analysis of the North Atlantic Oscillation (NAO) index during the 1960–1995 period reveals a significant increasing trend and an upward shift around 1980. Strong correlation is also detected between PC1 (Emilia Romagna and at the scale of all Italy) and the NAO index. Thus, the changes detected in the winter precipitation around 1985 could be due to an intensification of the positive phase of the [NAO], especially after 1980. Received March 23, 2001; revised February 20, 2002; accepted March 3, 2002     

Modeling soil thermal and hydrological dynamics and changes of growing season in Alaskan terrestrial ecosystems

Abundant evidence indicates the growing season has been changed in the Alaskan terrestrial ecosystems in the last century as climate warms. Reasonable simulations of growing season length, onset, and ending are critical to a better understanding of carbon dynamics in these ecosystems. Recent ecosystem modeling studies have been slow to consider the interactive effects of soil thermal and hydrological dynamics on growing season changes in northern high latitudes. Here, we develop a coupled framework to model these dynamics and their effects on plant growing season at a daily time step. In this framework, we (1) incorporate a daily time step snow model into our existing hydrological and soil thermal models and (2) explicitly model the moisture effects on soil thermal conductivity and heat capacity and the effects of active layer depth and soil temperature on hydrological dynamics. The new framework is able to well simulate snow depth and soil temperature profiles for both boreal forest and tundra ecosystems at the site level. The framework is then applied to Alaskan boreal forest and tundra ecosystems for the period 1923–2099. Regional simulations show that (1) for the historical period, the growing season length, onset, and ending, estimated based on the mean soil temperature of the top 20 cm soils, and the annual cycle of snow dynamics, agree well with estimates based on satellite data and other approaches and (2) for the projected period, the plant growing season length shows an increasing trend in both tundra and boreal forest ecosystems. In response to the projected warming, by year 2099, (1) the snow-free days will be increased by 41.0 and 27.5 days, respectively, in boreal forest and tundra ecosystems and (2) the growing season lengths will be more than 28 and 13 days longer in boreal forest and tundra ecosystems, respectively, compared to 2010. Comparing two sets of simulations with and without considering feedbacks between soil thermal and hydrological dynamics, our analyses suggest coupling hydrological and soil thermal dynamics in Alaskan terrestrial ecosystems is important to model ecosystem dynamics, including growing season changes.     

Changing growing season observed in Canada

It is theoretically interesting for climate change detection and practically important for agricultural producers to know whether climate change has influenced agroclimatic conditions and, if so, what the potential impacts are. We present analyses on statistical differences in means and variances of agroclimatic indices between three 30-year periods in the 20th century (i.e., 1911–1940, 1941–1970 and 1971–2000). We found many occurrences of statistically significant changes in means between pairs of the three 30-year periods. The findings consistently support agroclimatic trends identified from trend analysis as an earlier growing season start and an earlier end to spring frost (SF), together with an extended growing season, more frost-free days (FFD) and more available heat units were often found in the later 30-year periods as compared to the earlier ones. In addition, this study provides more detailed quantitative information than the trend signals for the practical interests of agricultural applications. Significant changes were detected for SF and FFD at a much larger percentage of stations between the latter two 30-year periods (1941–1970 vs. 1971–2000) as compared to the earlier two periods (1911–1940 vs. 1941–1970). In contrast, changes in variances of the selected agroclimatic indices were less evident than changes in their means, based on the percentage of stations showing significant differences. We also present new climate averages of the selected agroclimatic indices that can be useful for agricultural planning and management.     

Evaluating the vegetation growing season changes in the arid region of northwestern China

Temperature has long been accepted as the major controlling factor in determining vegetation phenology in the middle and higher latitudes. The influence of water availability is often overlooked even in arid and semi-arid environments. We compared vegetation phenology metrics derived from both in situ temperature and satellite-based normalized difference vegetation index (NDVI) observations from 1982 to 2006 by an example of the arid region of northwestern China. From the satellite-based results, it was found the start of the growing season (SOS) advanced by 0.37 days year^?1 and the end of the growing season (EOS) delayed by 0.61 days year^?1 in Southern Xinjiang over 25 years. In the Tianshan Mountains, the SOS advanced by 0.35 days year^?1 and the EOS delayed by 0.31 days year^?1. There were almost no changes in Northern Xinjiang. Compared with satellite-based results, those estimates based on temperature contain less details of spatial variability of vegetation phenology. Interestingly, they show different and at times reversed spatial patterns from the satellite results arising from water limitation. Phenology metrics derived from temperature and NDVI conclude that water limitation of onset of the growing season is more severe than the cessation. Phenology spatial patterns of four oases in Southern Xingjiang show that, on average, there is a delay of the SOS of 1.6 days/10 km of distance from the mountain outlet stations. Our results underline the importance of water availability in determining the vegetation phenology in arid regions and can lead to important consequences in interpreting the possible change of vegetation phenology with climate.     

1960-2009年武汉城区与郊区气候季节变化

利用1960-2009年武汉城区与郊区气象站逐日平均气温资料,采用相同气候季节划分方法,系统分析武汉城区与郊区气候季节起始时间、季节长度的变化趋势及其差异。结果表明：1980-2009年,武汉城区入春、入夏时间比郊区分别提前10 d和5 d,入秋、入冬时间城区比郊区推迟;武汉夏季长度城区比郊区长12 d,冬季、春季长度城区比郊区短6 d和5 d。1960-2009年武汉四季平均起始时间城区与郊区差别较小,但四季最早、最晚出现时间年际差别较大;武汉入春、入夏时间城区与郊区均提前,入秋、入冬时间均推后,但城区四季变化较显著,郊区仅入秋变化显著;武汉城区夏季长度呈极显著延长,冬季长度呈较显著缩短,城区春季、秋季及郊区四季长度变化均不显著。2000-2009年武汉城区与郊区季节起始时间和季节长度的变化较大,这是因为近10 a武汉作为中部地区崛起的支点,城区发展迅速。