Climatic change on the Tibetan Plateau: Potential Evapotranspiration Trends from 1961–2000

Time series (1961–2000) of Penman-Monteith potential evapotranspiration estimates for 101 stations on the Tibetan Plateau and surrounding areas are analyzed in this paper. For the Tibetan Plateau as a whole potential evapotranspiration (PET) has decreased in all seasons. The average annual evapotranspiration rate decreased by 13.1 mm/decade or 2.0% of the annual total. Superimposed on this general decline are fluctuations ranging from app. 600 to 700 mm with above average rates in the 1970s and 1980s. On a regional basis, spatial trend distributions remain stable throughout the year with similar seasonal variations. Decreasing PET rates are more pronounced in winter and spring (80% of all stations) as compared to summer and autumn (58% of all stations). Maximum negative (positive) annual rates were recorded at two stations in the southern Qaidam Basin with –79.5 mm/decade (84.8 mm/decade) even though in general negative rates tend to be noticeably higher than positive rates.Changes in wind speed and to a lesser degree relative humidity were found to be the most important meteorological variables affecting PET trends on the Tibetan Plateau while changes in sunshine duration played an insignificant role. Stable daytime temperatures on the Tibetan Plateau have limited the importance of temperature trends for changes of PET rates. Negative evapotranspiration trends are therefore thought to be linked to a general decrease in intensity of the regional monsoon circulation rather than to reductions in sunshine duration. Reduced PET rates appear to be in contrast to a predicted increased hydrological cycle under global warming scenarios.     

晋西北地区马铃薯生态需水量对气候变化的响应

基于晋西北地区8个地面气象站1960~2010年的气象资料及马铃薯生育期平均资料,运用P-M公式,计算了马铃薯生态需水量,分析了生态需水量的时间演变特征及其对气候变化的响应。结果表明:晋西北地区马铃薯生态需水量整体上呈显著下降趋势,但不同时段下降幅度差异较大;风速和日照时数的变化对马铃薯生态需水量的影响最为突出。气候变暖对该地区马铃薯生态需水量的影响表明,气温的升高会增加马铃薯的需水量,且不同地区需水量的增幅不尽相同,气候变暖对寒冷地区马铃薯需水量的影响更加显著。     

湖南省油菜生育期间气候资源时空变化规律分析

利用湖南省1962—2010年96个气象站逐日气象资料及5个农业气象试验站1991—2010年油菜生育期观测资料,应用气候统计分析方法,分析了油菜主要生育期气候资源空间分布规律和年际变化特征。结果表明:湖南省油菜全生育期时长无明显地域性差异,生育期间大于等于0℃积温有明显的地域性差异。影响油菜生育期间的主要气象因子为气温和日照时数,不同生育期主要气象因子有所差异。各发育期气候资源空间分布不均,年际变化有差异。冬前苗期和角果发育期的积温呈增加趋势,越冬期的小于等于0℃和小于等于-3℃日数呈减少趋势,蕾薹期日照时数呈减少趋势,开花期和角果发育期日照时数呈增加趋势。总体而言,湖南油菜生育期间的气候资源及其变化趋势有利于油菜生长。     

Multiscale evolution of surface air temperature in the arid region of Northwest China and its linkages to ocean oscillations

Reference crop evapotranspiration (ETo) is one of the most important links in hydrologic circulation and greatly affects regional agricultural production and water resource management. Its variation has drawn more and more attention in the context of global warming. We used the Penman-Monteith method of the Food and Agriculture Organization, based on meteorological factors such as air temperature, sunshine duration, wind speed, and relative humidity to calculate the ETo over 46 meteorological stations located in the Yangtze River Delta, eastern China, from 1957 to 2014. The spatial distributions and temporal trends in ETo were analyzed based on the modified Mann-Kendall trend test and linear regression method, while ArcGIS software was employed to produce the distribution maps. The multiple stepwise regression method was applied in the analysis of the meteorological variable time series to identify the causes of any observed trends in ETo. The results indicated that annual ETo showed an obvious spatial pattern of higher values in the north than in the south. Annual increasing trends were found at 34 meteorological stations (73.91 % of the total), which were mainly located in the southeast. Among them, 12 (26.09 % of the total) stations showed significant trends. We saw a dominance of increasing trends in the monthly ETo except for January, February, and August. The high value zone of monthly ETo appeared in the northwest from February to June, mid-south area from July to August, and southeast coastal area from September to January. The research period was divided into two stages—stage I (1957–1989) and stage II (1990–2014)—to investigate the long-term temporal ETo variation. In stage I, almost 85 % of the total stations experienced decreasing trends, while more than half of the meteorological stations showed significant increasing trends in annual ETo during stage II except in February and September. Relative humidity, wind speed, and sunshine duration were identified as the most dominant meteorological variables influencing annual ETo changes. The results are expected to assist water resource managers and policy makers in making better planning decisions in the research region.     

烟台市蒸发量变化趋势及影响因子

利用烟台市1971—2010年蒸发量、气温、日照、降水和总云量资料,采用线性回归、相关分析、小波分析、逐步回归方法,对蒸发量变化趋势及其影响因子进行分析。结果表明,烟台年蒸发量存在2～3年的主周期和4～8、8～12年的次周期变化,春季、夏季、秋季和冬季蒸发量分别存在3～5、5～7、7～11和2～4年的周期变化。平均相对湿度的增加和日照时数的减少是蒸发量减少的主要原因,而影响各季节蒸发量变化的气象因子各有不同。日照时数和总云量是影响夏秋季节蒸发量变化的最主要因子,秋冬季节的蒸发量主要受平均相对湿度、日照时数和总云量的共同影响。     

中国地区日照时数近50年来的变化特征

根据国家气象信息中心给出的逐日日照时数资料, 利用经验正交函数分解(EOF)和Mann-Kendall方法分析了1956～2005年中国地区日照时数的变化趋势、突变情况、时空分布和季节变化特征。研究表明:中国绝大部分地区近50年来日照时数总量呈减少的趋势, 在1980年前后大部分观测站显示有突变, 20世纪 90年代之后减少趋势有所缓解, 保持在稳定偏低的状态;此类变化趋势在东南地区较西北地区更为显著。且日照时数的上述变化主要由于夏季日照的变化造成的。     

1961-2009年东北地区日照时数变化特征

根据1961-2009年东北地区104个气象站的日照时数、气温、降水、风速和相对湿度资料,利用趋势分析、Mann-Kendall分析和相关分析等方法,研究东北地区日照时数月、季、年的时空变化特征,同时还对可能影响日照时数的气候因子进行分析。结果表明：东北地区5月日照时数最高,12月日照时数最低。年日照时数呈显著减少趋势,平均每10 a减少40.5 h;除秋季日照时数变化不显著外,其他季节日照时数均显著减少。在20世纪80年代初期存在明显的突变,日照时数开始减少。东北地区日照时数大致呈西高东低的经向分布;除黑龙江北部地区外,其余大部地区日照时数均呈减少的趋势,其中吉林北部地区减少最为明显。东北地区日照时数与气温呈负相关关系,相关系数为-0.40;与降水呈负相关关系,相关系数为-0.37;与风速呈正相关关系,相关系数为0.53;与相对湿度呈负相关关系,相关系数为-0.32。前三者均通过了99.9 %的信度检验,相对湿度通过了99.5 %的信度检验。     

近60年深圳气候平均值变化特征分析

利用深圳国家基本气象站1953—2010年的观测资料,分析深圳气象要素平均值变化趋势和气候特点。结果表明,深圳总体呈现气温升高、降水量起伏、相对湿度下降和日照时数减少趋势。深圳的夏季延长、秋冬渐短,雷雨影响时段略有延长。另外,冬季平均气温的升高对深圳暖冬年份的判定有较为明显的影响,在气候评价等气候业务中需要注意这些差异。     

Spatiotemporal variations of potential evapotranspiration and aridity index in relation to influencing factors over Southwest China during 1960–2013

This study investigated the spatial–temporal patterns and trends of potential evapotranspiration (ET₀) and aridity index (AI) over Southwest China during 1960–2013 based on daily temperature, precipitation, wind speed, sunshine duration, total solar radiation, and relative humidity data from 108 meteorological stations. The Penman–Monteith model, Mann–Kendall (M–K) test, moving t test, and Morlet wavelet method were used. The results indicated that ET₀ and AI across the region displayed decreasing trends, but the former was significant. After 2000, regionally average trends in ET₀ and AI increased rapidly, indicating that droughts increased over Southwest China in recent years. Spatially, the changes of ET₀ and AI were dissimilar and not clustered, either. Temporally, both ET₀ and AI displayed obvious abrupt change points over different timescales and that of AI was during the winter monsoon period. Significant periodic variations with periods of 27, 13, and 5 years were found in ET₀, but only of 13 and 5 years existed in AI. Correlation analysis revealed that the sunshine duration and wind speed were the dominant factors affecting ET₀ and that AI showed strong negative correlation with precipitation. The findings of this study enhance the understanding of the relationship between climate change and drought in Southwest China, while the mechanism controlling the variation in drought requires further study.     

1961—2015年新疆天山日照时数时空变化特征及其影响因素分析

采用新疆天山地区55个气象站1961—2015年逐月气象数据,用Mann Kendall突变检验、基于ArcGIS的混合插值及偏相关分析对天山日照时数年、季节特征及影响因素进行分析。结果表明：①天山日照时数年及季节均呈减少趋势,天山各区域变化差异显著,山区及天山北坡变化趋势明显于南坡。②天山北坡、天山南坡及天山山区年日照时数突变时间为1985年、1980年和1988年,云量和降水是导致突变发生的主导因素。③新疆天山年日照时数由西向东逐渐增加,平原多、山区少,春季呈“东北部多、西南部少”,夏季为 “东北部多、西南部少”,平原盆地高于山区,秋季呈现“北少南多,东多西少”,冬季由南向北逐渐减少。④云量、降水是导致天山地区日照减少的主要因素,少云区日照时数较多,多云区日照时数较少,天山云量减幅或增幅区域,日照时数突变量变化明显。     

Analysis of sky conditions using 40 year records of solar radiation data in China

Summary Forty years of daily global and diffuse radiation data have been used to characterize the atmospheric optical conditions at 14 premium radiation stations in China. The clearness index (K _T ), diffuse ratio (K _D ), and diffuse coefficient (K _C ) have been analyzed for long-term and seasonal variations, correlations of relative sunshine (R _S ) versus clearness index and diffuse coefficient, respectively. Two polynomial models have been developed to simulate clearness index and diffuse ratio by using relative sunshine data and have been shown to be reasonable at most of the 14 stations. The results show that there are significant declining trends in clearness index and increasing trends in diffuse ratio at most of the 14 premium radiation stations, but there are no significant trends for diffuse coefficient. The seasonal variations of clearness index are determined by the regional climate and changes with relative sunshine.     

1961～2005年云贵高原太阳辐射变化特征及其影响因子

利用云贵高原1961～2005年9个日射站辐射和气候观测资料以及能见度观测资料等,采用数理统计方法,研究了该区域到达地表太阳总辐射量(以下简称总辐射)变化特征及其影响因子.结果表明:该区年总辐射的空间分布特点是西部高于东部,丽江站最高(6207MJ·m-2·a-1),遵义站最低(3340MJ·m-2·a-1).1961...     

Effects of Climate Change on Evapotranspiration from Paddy Fields in Southern Taiwan

The major objective of this study was to investigate the effects of climate change on evapotranspiration from paddy fields. A sensitivity analysis of meteorological variables at the Kao-Hsiung station, one of meteorological stations in southern Taiwan, was carried out using the modified Penman formula. Forty-eight-year records of temperature, relative humidity, sunshine duration, wind speed, and precipitation depth comprised the database. Trend and persistence analyses of the data were performed using the Mann–Kendall test, the Cumulative Deviation test, Linear Regression, andthe Autocorrelation Coefficient. The results indicated that only temperature and relative humidity have significant long-term trends and persistence. Two climatic scenarios, viz. (1) linear extrapolation of climatic trends and (2) the predictions of General Circulation Models (GCMs), were assumed to investigate the effects of climate change on evapotranspiration. The study revealed that evapotranspiration from paddy fields increased under both climatic scenarios studied.     

From brightening to dimming in sunshine duration over the eastern and central Tibetan Plateau (1961–2005)

The Tibetan Plateau (TP) with an average elevation of over 4,000 m asl is the highest and most extensive highland in the world. We used monthly mean sunshine duration from the Chinese Meteorological Administration to examine the spatial and temporal variability of sunshine duration at 71 stations with elevations above 2,000 m asl in the eastern and central TP during the 1961–2005 period. The temporal evolution of the mean annual sunshine duration series shows a significant increase from 1961 to 1982 at a rate of 49.8 h/decade, followed by a decrease from 1983 to 2005 at a rate of ?65.1 h/decade, with an overall significant decrease at a rate of ?20.6 h/decade during the whole 1961–2005 period, which is mainly due to the summer and spring seasons. This confirms the evidence that sunshine duration in the TP ranges from brightening to dimming in accordance with sunshine duration trends in the rest of China. The surface solar radiation downwards from ERA-40 reanalysis data in the same region confirms the brightening/dimming phenomenon shown by the sunshine duration before/after the 1980s. Otherwise, additional climatic variables such as low cloud amount, total cloud amount, precipitation, relative humidity and water vapor pressure, in most cases, exhibit significant negative correlation with sunshine duration in the TP on an annual and seasonal basis before and after 1982, respectively. The trends of these variables suggest that changes in some of them might be related to the brightening and dimming detected with the use of sunshine duration measurements over the TP. We also hypothesize that the impact of anthropogenic aerosols upon the climatic variables analyzed cannot be rejected, especially in the significant increase in low cloud cover since approximately 1980.     

Concentration of trace gases in the lower troposphere,simultaneously recorded at neighboring mountain stations Part II: Ozone

Summary Long-term ozone recordings at different altitude levels, conducted in remote areas, can make a valuable contribution to an understanding of the background level of ozone, its periodical variations and possible long-term trends.The measuring stations (three high mountain stations between 740 and nearly 3000 m a.s.l. with small horizontal distance) are described together with recording and calibration procedures. Information is provided on the time history of all recordings since 1978, considering not only the annual means but also the monthly and 10-day means as a function of height. An analysis is presented of the annual variations which differ considerably in the respective height levels and—in three-dimensional diagrams—the correlation between daily and annual variation is shown as a function of height. Then follows a careful parameterization: analysis of the frequency distribution of the ozone concentration, correlation with relative humidity, relative sunshine duration, and temperature. It can be seen that the correlations are very different and partly inverse, depending on the altitude level.Many ozone profiles obtained between valley level and nearly 3000 m a.s.l. (cable car O₃ radiosonde) give a picture of the typical ozone profile for different meteorological situations and for the case of stratospheric intrusions of ozone into the troposphere. The stratospheric contribution of ozone to the tropospheric ozone budget is discussed.Since obviously a very high photochemical production rate can be established for ozone in the lowest layer above ground (correlation of O₃ with the daily variation of the sunshine duration) it was examined if this O₃ variation might be caused only by horizontal transport of ozone from remote areas with high anthropogenic activity by the daily quasiperiodical currents near the ground. But this is not the case.The correlation between ozone concentration, other trace gases such as nitrogen-oxygen compounds and hydrocarbons is shown.With 29 Figures     

Temporal and spatial variations of global solar radiation over the Qinghai–Tibetan Plateau during the past 40 years

Global solar radiation is of great significance to the balance of ground surface radiation, the energy exchange between the Earth’s surface and atmosphere, and the development of weather and climate systems in various regions. In this study, the monthly global radiation recorded at 23 stations over the Qinghai–Tibetan Plateau (QTP) was utilized to estimate global solar radiation (Q) from sunshine duration and to obtain improved fits to the variation coefficients of the monthly Angström–Prescott model (APM). The modeling results were evaluated by calculating the statistical errors, including mean bias error, mean absolute error, root mean square error, and mean relative error. We demonstrate that the monthly Q values can be predicted accurately by APM over the QTP. We also assess the variations of Q values at 116 meteorological stations by APM over the QTP during 1961–2000. The analysis shows that the annual mean sunshine duration amounted to more than 3,000 h over the whole plateau, implying promising prospects for economic applications of solar energy. During the past 40 years, the mean global solar radiation has been relatively high in the western QTP, extending northward to the Inner Mongolian Plateau. Although its decadal variations in the QTP and surrounding regions were inconsistent, the anomaly values of global solar radiation were generally positive during the 1960s and 1970s, indicating that the QTP’s global solar radiation has increased during those periods. The anomaly values were negative during the 1980s and 1990s, showing that the plateau’s global solar radiation has decreased during those periods. Global solar radiation over the QTP is negatively proportional to latitude but positively proportional to altitude and relative sunshine duration. Three factors, the sunshine duration, latitude, and altitude, exert great influence on global surface radiation, of which sunshine duration is most significant. A high-variation-coefficient zone of global solar radiation occurred in the western part of the QTP but, on average, the variation coefficient of the plateau’s global solar radiation was only 0.031, suggesting that the variation in global radiation was relatively stable over the whole QTP.     

Models for obtaining daily global solar irradiation from air temperature data

The study presents a critical assessment of the possibility of global solar irradiation computation by using air temperature instead of sunshine duration with the classical Ångström equations. The reason for this approach comes from the fact that, although the air temperature is a worldwide measured meteorological parameter, this is rarely used in solar radiation estimation techniques. More than that, the literature is very silent concerning the testing of such models in Eastern Europe. Two new global solar irradiation models (to be called AEAT) related to solar irradiation under clear sky conditions and having the minimum and maximum daily air temperature as input parameters were tested and compared with others from the literature against data measured at five stations in Romania in the year 2000. The accuracy of AEAT is acceptable and comparable to that of the models which use sunshine duration or cloud amount as input parameters. Since temperature-based Ångström correlations are strongly sensitive to origin, the approach for AEAT as a tool for potential users is presented in detail. Additionally reported is a new method to increase the generality of AEAT concerning the extension of the geographical application area. Based on overall results it was concluded that air temperature successfully substitutes sunshine duration in the estimation of the available solar energy.     

海南岛0 cm地温变化特征及其相关气象要素

利用海南岛17个气象观测站1980-2018年逐月0 cm地温及气象要素资料,通过数理统计方法分析了海南岛年和四季的0 cm地温时空变化特征及其与气象要素的关系.结果表明:海南岛年平均0 cm地温呈显著上升趋势,秋季升温对年平均0 cm地温的升高有主要贡献,春季次之.M-K检验表明年与春秋两季0 cm地温在20世纪90...     

On the variations of sunshine duration in Austria

Summary The seasonal and annual duration of sunshine in Austria during the 30 year period 1960–1989 is analyzed and the trends during this time interval are mapped. It is shown that sunshine decreased in the northern and eastern parts of Austria. In the mountain regions only small changes can be seen but there is some evidence that in the high mountain regions a remarkable increase in sunshine duration has taken place.Dedicated to O. Univ.-Prof. Dr. F. Steinhauser.With 7 Figures     

海南岛蒸发量的变化特征及其影响因子分析

利用海南岛18个气象观测站1966—2001年逐日20cm口径小型蒸发皿蒸发量及气象要素资料,通过数理统计方法分析了海南岛年和四季的蒸发量变化特征及气象因子对蒸发量的影响。结果表明:从时间上看,海南岛年蒸发量变化呈波动式下降,蒸发量的减少主要出现在春季,冬季和夏季次之。从空间上看,年蒸发量呈东北少、西南多的分布,其大值区主要集中在西南部,小值区主要集中在东北部和中部地区。M-K检验说明年与春冬两季蒸发量的变化呈下降趋势且在1994年前后发生突变。影响蒸发量变化的因子中,日照时数和风速是造成蒸发量减小的主要因子,降水量的影响仅次于风速和日照时数,而气温不是造成海南岛蒸发量减小的主要因子,相对湿度可能是海南岛的蒸发量减小的影响因子。