根据气温变化率进行三角高程测量的折光改正

不同的气温梯度会产生不同的大气折射，根据测程前后两半段的气温梯度与－ ００３４２ 之差值，可将光线沿测程方向的折射分为４ 种类型，它们对三角高程测量的往返高差均值会产生不同的影响．利用测程两端及１４ Ｓ，１２ Ｓ，３４ Ｓ三点之间的气温变化率，模拟光程前、后两半段气温梯度的二次曲线；经数学推导，提出一种根据测程上不同区间的气温变化率直接对三角高程测量中的高差观测值进行大气折光改正且对４ 种折射类型均适用的方法．实验初步证明，运用该方法，只要同时测定两端点及３ 个以上特征点的气温，求得相应的测程区间气温变化率，据此直接对高差观测值进行折光改正，由此得到的三角高程测量往返高差均值与真值比较的标准差可缩小约５０ ％ ，即可较好地削弱大气折射对三角高程测量产生的影响．

我国近40年气温变化地域类型的研究

依据１９５１～１９９０年全国７０多个站点４０年的气温资料，采用相关分析和线性模拟的方法，从区域气候特征和气温变化趋势一致的角度，首先划分出气温变化的１０个地区，再根据气温变化率进行分型，最后在此基础之上归并成３个气温变化区域。

我国近四十年气温变化时空差异研究

文章通过对我国近４０年不同区域气温变化的分析发现，在我国东部地区大体以中亚热带为界，中亚热带以北地区具有冬季气温变暖，夏季气温变凉的趋势，中亚热带以南地区具有夏季气温变暖，冬、春季变冷的趋势；而深居大陆内侧的西部干旱地区和云南高原地区与同纬度其他地区相比，也各具特点。

近30年中国东部气温对土地覆被变化的敏感性

利用1979—2010年中国东部295个气象站点近30年逐年各月的月平均气温数据，分析气象站站点周围3km土地覆被变化和相应气温变化，研究中国东部地表土地覆被变化对站点气温变化的影响。结果表明：近30年研究区域内草地锐减，城市剧烈扩张，林地显著增加；站点气温年平均变化率在-0．2～0．9℃／10a之间，区域气温年平均变化率为0．38℃／10a；不同土地覆被上的气象站点气温变化率明显不同，按城市、农田、草地、林地的顺序依次减小；区域气温变化是多种覆被共阿作用的结果；土地覆被变化并非局地气温上升的唯一原因，却深刻地影响着局地年气温变化率。

秦岭—黄淮平原交界带中东部近50a气温变化特征分析

选取了交界带中东部1961—2006年的5个代表站点逐日气温资料,采用趋势系数、滑动平均等方法对年及各季气温变化特征进行诊断分析,并用Mann-Kendall对年平均气温时间序列可能的突变点进行了检测.结果表明,近50 a交界带中东部气温呈不显著上升趋势(0.086℃/10a),其中长葛的气温倾向率为0.18℃/10a,是年平均气温倾向率的2倍.春、秋、冬3个季节的平均气温50年来呈上升趋势,冬季上升幅度较大,气温变化率为0.31℃/10a,明显高于春、秋2季的0.1℃/10 a和0.14℃/10 a,夏季的平均温度呈下降趋势,气温变化率为-0.22℃/10a.利用Mann-Kendall突变检验方法对年平均气温进行检验的结果显示,气温在1963年和1997年发生突变.

商丘地区近47年气温变化特征分析

根据商丘市所辖8个代表站1961-2007年47年的逐月地面月平均气温资料，采用线性回归分析、滑动平均、累积距平等方法对气温变化趋势进行诊断分析，用滑动t-检验法、Yamamoto法、Mann-Kendall法等统计方法，对平均气温时间序列可能的突变点分别进行了检测。结果表明，近47年商丘年平均气温变化率为0.078℃/10年；其间经历了20世纪60-70年代的增暖期，80年代的气温变冷期，90年代中后期又进入了一个较强的增暖期；春、秋、冬3个季节的平均气温整体上都呈上升趋势，冬季上升幅度较大，气温变化率为0.382℃/10年，明显高于春、秋两季的0.084、0.049℃/10年；而夏季的平均温度整体上呈下降趋势，气温变化率为-0.169℃/10年。3种方法检测结果综合来看，四季突变时间不同，1993年是年平均气温由冷转为增暖的突变点，可信度达99%。

气候变化的事实与城市化的影响

本文利用8个高山站近50年逐日最高气温、最低气温和平均气温资料,分析了高山站近50年来气温的年变化、四季变化、无霜期及年平均气温的突变特征并探讨了城市化发展对气候的影响。通过探讨发现:(1)近50年来8个高山站的年平均气温、年平均日最高气温和年平均日最低气温都有升高的趋势,且呈现出一定的非对称性,纬度较高高山站的平均气温和日最低气温增温趋势大于纬度较低高山站。(2)8个高山站冬季气温都有明显的增温趋势,而且冬季气温的增温趋势大于春、夏、秋三季;庐山夏季年平均气温、年平均日最高气温和年平均日最低气温有微弱的降温趋势。(3)除天池外,近50年来,7个高山的无霜期天数及无霜期变化趋势率呈现除南高北低的现象,且无霜期天数都有增长的趋势;绝大多数高山年平均气温变化突变点和年平均气温显著上升起始年大都出现在20世纪90年代。(4)近50年来,人类活动及城市化只是在一定范围内对气候有一定的影响,但是并不是很大。

Effect of Altitude and Latitude on Surface Air Temperature across the Qinghai-Tibet Plateau

The correlation between mean surface air temperature and altitude is analyzed in this paper based on the annual and monthly mean surface air temperature data from 106 weather stations over the period 1961-2003 across the Qinghai-Tibet Plateau. The results show that temperature variations not only depend on altitude but also latitude, and there is a gradual decrease in temperature with the increasing altitude and latitude. The overall trend for the vertical temperature lapse rate for the whole plateau is approximately linear. Three methods, namely multivariate composite analysis, simple correlation and traditional stepwise regression, were applied to analyze these three correlations. The results assessed with the first method are well matched to those with the latter two methods. The apparent mean annual near-surface lapse rate is -4.8 ℃ /km and the latitudinal effect is -0.87 ℃ /°latitude. In summer, the altitude influences the temperature variations more significantly with a July lapse rate of -4.3℃/km and the effect of latitude is only -0.28℃ /°latitude. In winter, the reverse happens. The temperature decrease is mainly due to the increase in latitude. The mean January lapse rate is -5.0℃/km, while the effect of latitude is -1.51℃ /°latitude. Comparative analysis for pairs of adjacent stations shows that at a small spatial scale the difference in altitude is the dominant factor affecting differences in mean annual near-surface air temperature, aided to some extent bydifferences of latitude. In contrast, the lapse rate in a small area is greater than the overall mean value for the Qinghai-Tibet Plateau （5 to 13℃ /km）. An increasing trend has been detected for the surface lapse rate with increases in altitude. The temperature difference has obvious seasonal variations, and the trends for the southern group of stations （south of 33 o latitude） and for the more northerly group are opposite, mainly because of the differences in seasonal variation at low altitudes. For yearly changes, the temperature for high-altitude stations occurs earlier clearly. Temperature datasets at high altitude stations are well-correlated, and those in Nanjing were lagged for 1 year but less for contemporaneous correlations. The slope of linear trendline of temperature change for available years is clearly related to altitude, and the amplitude of temperature variation is enlarged by high altitude. The change effect in near-surface lapse rate at the varying altitude is approximately 1.0℃ /km on the rate of warming over a hundred-year period.

Effect of Aspect on Climate Variation in Mountain Ranges of Shennongjia Massif, Central China

The aim of this study was to better understand the mechanisms of regional climate variation in mountain ranges with contrasting aspects as mediated by changes in global climate. It may help predict trends of vegetation variations in native ecosystems in natural reserves. As measures of climate response, temperature and precipitation data from the north, east, and south-facing mountain ranges of Shennongjia Massif in the coldest and hottest months(January and July), different seasons(spring, summer, autumn, and winter) and each year were analyzed from a long-term dataset(1960 to 2003) to tested variations characteristics, temporal and spatial quantitative relationships of climates. The results showed that the average seasonal temperatures and precipitation in the north, east, and south aspects of the mountain ranges changed at different rates. The average seasonal temperatures change rate ranges in the north, east, and south-facing mountain ranges were from –0.0210℃/yr to 0.0143℃/yr, –0.0166℃/yr to 0.0311℃/yr, and –0.0290 ℃/yr to 0.0084℃/yr, respectively, and seasonal precipitation variation magnitude were from –1.4940 mm/yr to 0.6217 mm/yr, –1.6833 mm/yr to 2.6182 mm/yr, and –0.8567 mm/yr to 1.4077 mm/yr, respectively. The climates variation trend among the three mountain ranges were different in magnitude and direction, showing a complicated change of the climates in mountain ranges and some inconsistency with general trends in global climate change. The climate variations were significantly different and positively correlated cross mountain ranges, revealing that aspects significantly affected on climate variations and these variations resulted from a larger air circulation system, which were sensitive to global climate change. We conclude that location and terrain of aspect are the main factors affecting differences in climate variation among the mountain ranges with contrasting aspects.

Evaluating the impacts of land use and land cover changes on surface air temperature using the WRF-mosaic approach

Satellite-derived land surface data in 1980 and 2010 were used to represent land use and land cover（LULC） changes caused by the rapid economic development and human activities that have occurred over the past few decades in East Asia and China. The effects of LULC changes on the radiation budget and 2-m surface air temperature（SAT） were explored for the period using the Weather Research and Forecasting（WRF） model. The mosaic approach, which considers the N-most abundant land use types within a model grid cell（here, N = 3） and precisely describes the subgridscale LULC changes, was adopted in the integrations. The impacts of LULC changes based on two 36-year integrations showed that SAT generally decreased, with the sole exception being over eastern China, resulting in decreased SAT in China（-0.062 °C） and East Asian land areas（EAL,-0.061 °C）. The LULC changes induced changes in albedo, which influenced the radiation budget. The radiative forcings at the top of the atmosphere were-0.56 W m-2 across the whole of China, and-0.50 W m-2 over EAL. Meanwhile, the altered roughness length mainly influenced near-surface wind speeds, large-scale and upward moisture fluxes, latent heat fluxes, and cloud fractions at different altitudes. Though the impacts caused by the LULC changes were generally smaller at regional scales, the values at local scales were much stronger.

Inhomogeneous trends in the onset date of extreme hot days in China over the last five decades

Using a homogenized daily maximum temperature(T_(max))dataset across China,this study characterized the spatiotemporal variation of the onset date of extreme hot days in a year(i.e.,FirstEHD)during 1960-2018.Inhomogeneous trends of FirstEHD over China during 1960-2018 can be found,with the advanced trend of FirstEHD over most parts in China,while a number of stations in North-Central China(NC)show the delayed trend of FirstEHD.Moreover,there exist interdecadal changes of FirstEHD trend,with a remarkable difference in the trend magnitude before and after the 1990s over South China(SC),and the sign of trend can even reverse from negative to positive after the 1990s in Xinjiang(XJ)and Yangtze River Basin(YR),and from positive to negative in NC.The overall trends of FirstEHD over NC,YR,and XJ during 1960-2018 are dominated by the trends before the 1990s,while they are dominated by the sharp advance after the 1990s over SC.It is further found that the trend of FirstEHD can generally be explained by the long-term trend in T_(max) over most parts of China,but the contribution from T_(max) variabilities is also non-negligible and can even account for more than 75% of the overall trend over NC.The possible factors responsible for the decadal changes in FirstEHD trends are also discussed.

How similar are annual and summer temperature variability in central Sweden?

Tree-ring based temperature reconstructions have successfully inferred the past inter-annual to millennium scales summer temperature variability. A clear relationship between annual and summer temperatures can provide insights into tile variability of past annual mean tem- perature from the reconstructed summer temperature. However, how similar are summer and annual temperatures is to a large extent still unknown. This study aims at investigating the relationship between annual and summer temperatures at different timescales in central Sweden during the last millennium. The temperature variability in central Sweden can represent large parts of Scandinavia which has been a key region for dendroclimatological research. The observed annual and summer temperatures during 1901-2005 were firstly decomposed into different frequency bands using ensemble empirical mode decomposition （EEMD） method, and then the scale-dependent relationship was quantified using Pearson correlation coefficients. The relationship between the observed annual and summer temperatures determined by the instrumental data was subsequently used to evaluate 7 climate models. The model with the best performance was used to infer the relationship for the last millennium. The results show that the relationship between the observed annual and summer temperatures becomes stronger as the timescale increases, except for the 4--16 years timescales at which it does not show any relationship. The summer temperature variability at short timescales （2--4 years） shows much higher variance than the annual variability, while the annual temperature variability at long timescales （〉32 years） has a much higher variance than the summer one. During the last millennium, the simulated summer temperature also shows higher variance at the short timescales （2-4 years） and lower variance at the long timescales （〉1024 years） than those of the annual temperature. The relationship between the two temperatures is generally close at the long timescales, and weak at the short timescales. Overall the summer temperature variability cannot well reflect the annual mean temperature variability for the study region during both the 20th century and the last millennium. Furthermore, all the climate models examined overestimate the annual mean temperature variance at the 2--4 years timescales, which indicates that the overestimate could be one of reasons why the volcanic eruption induced cooling is larger in climate models than in proxy data.

Sensitivity of the Terrestrial Ecosystem to Precipitation and Temperature Variability over China

In this study, the sensitivities of net primary production(NPP), soil carbon, and vegetation carbon to precipitation and temperature variability over China are discussed using the state-of-the-art Lund-Potsdam-Jena dynamic global vegetation model(LPJ DGVM). The impacts of the sensitivities to precipitation variability and temperature variability on NPP, soil carbon, and vegetation carbon are discussed. It is shown that increasing precipitation variability, representing the frequency of extreme precipitation events, leads to losses in NPP, soil carbon, and vegetation carbon over most of China, especially in North and Northeast China where the dominant plant functional types(i.e., those with the largest simulated areal cover) are grass and boreal needle-leaved forest. The responses of NPP, soil carbon, and vegetation carbon to decreasing precipitation variability are opposite to the responses to increasing precipitation variability. The variations in NPP, soil carbon, and vegetation carbon in response to increasing and decreasing precipitation variability show a nonlinear asymmetry. Increasing precipitation variability results in notable interannual variation of NPP. The sensitivities of NPP, soil carbon, and vegetation carbon to temperature variability, whether negative or positive, meaning frequent hot and cold days, are slight. The present study suggests, based on the LPJ model, that precipitation variability has a more severe impact than temperature variability on NPP, soil carbon, and vegetation carbon.

Rates of temperature change in China during the past 2000 years

Using 24 proxy temperature series, the rates of temperature change in China are analyzed at the 30- to 100-year scales for the past 2000 years and at the 10-year scale for the past 500 years. The results show that, at the 100-year scale, the warming rate for the whole of China in the 20th century was only 0.6±1.6℃/100 a （interval at the 95% confidence level, which is used here- after）, while the peak warming rate for the period from the Little Ice Age （LIA） to the 20th century reached 1.1_＋1.2~C/100 a, which was the greatest in the past 500 years and probably the past 2000 years. At the 30-year scale, warming in the 20th century was quite notable, but the peak rate was still less than rates for previous periods, such as the rapid warming from the LIA to the 20th century and from the 270s-290s to 300s-320s. At the 10-year scale, the warming in the late 20th century was very evident, but it might not be unusual in the context of warming over the past 500 years. The exact timing, duration and magnitude of the warming peaks varied from region to region at all scales. The peak rates of the 100-year scale warming in the AD 180s-350s in northeastern China as well as those in the 260s-410s and 500s-660s in Tibet were all greater than those from the mid-19th to 20th century. Meanwhile, the rates of the most rapid cooling at scales of 30 to 100 years in the LIA were promi-nent, but they were also not unprecedented in the last 2000 years. At the 10-year scale, for the whole of China, the most rapid decadal cooling in the 20th century was from the 1940s to 1950s with a rate of -0.3±0.6℃/10 a, which was similar to rates for periods before the 20th century. For all regions, the rates of most rapid cooling in the 20th century were all less than those for previous periods.