Linear trends in mean and extreme temperature in Xiongan New Area, China

On 1 April 2017 China established Xiongan New Area in Hebei Province, which was described as ‘a strategy crucial for a millennium to come＇. A point of interest for the public is to be aware of the historical climate change in this new area; however, results from previous global-scale or largerregional-scale averages provide relatively limited information because of the distinct regional differences in climate change. This study analyzes the changes in mean and extreme temperature in this area, based on homogenized daily temperature data for the period 1960–2016. The results show a significant warming in the indices of annual, summer, and winter mean temperature（Tmean）, maximum temperature（Tmax）, and minimum temperature（Tmin）. The linear rate of annual Tmean is 0.34 °C/decade. Temperatures on the hottest day, the warmest night, the coldest day, and the coldest night, every year, all show increasing trends, with the trends in the two nighttime-related indices being significant. An increasing occurrence of warm days, warm nights, hot days, and tropical nights, but a decreasing occurrence of cold days, cold nights, icing days, and frost days, are found, all of which are significant, except for the occurrences of hot days and icing days. A significant extension of the length of the thermal growing season is also found. The magnitudes of change in most of the temperature indices in Xiongan New Area are larger than those of the adjacent Jing-Jin-Ji and North China regional mean. These results could provide valuable information for policymakers, city planners, engineers, and migrants to this new area.

ANALYSIS OF THE CHARACTERISTICS OF RAINFALL AND LINEAR TREND IN MENGLUN, XISHUANGBANNA,SOUTHWEST CHINA

1 INTRODUCTION As one of the main factors affecting input and use of precipitation by forests, rainfall also makes a difference on partitioning of gross precipitation over the canopy, equilibrium of water amount in river basins and water cycling processes . In view of its poorlydefined four seasons in contrast to well-defined dry and wet spells in addition to its inland location, understanding of precipitation characteristics and tendencies is important for the study on local forestry hydrology. Relevant research has been documented, but few have dealt with multiple time scales at the hourly, daily, monthly and annual intervals. With the 1992 - 2003 automatic record of precipitation in Menglun, Xishuangbannan analyzed, its characteristics and trends are summarized to help in the study on forestry hydrology.

A Production Inventory Model of Constant Production Rate and Demand of Level Dependent Linear Trend

The proposed model considers the products with finite shelf-life which causes a small amount of decay. The market demand is assumed to be level dependent and in a linear form. The model has also considered the constant production rate which stops attaining a desired level of inventories and that is the highest level of inventories. Production starts with a buffer stock and without any sort of backlogs. Due to the market demand and product’s decay, the inventory reduces to the level of buffer stock where again the production cycle starts. With a numerical search procedure the proof of the proposed model has been shown. The objective of the model is to obtain the total average optimum inventory cost and optimum ordering cycle.

Oxygen and Carbon Isotope Composition in Primary Carbonatites of the World: Data Summary and Linear Trends

The article contains the results of statistical processing of a large summary of δ18О-δ13С isotope values in the primary carbonatites of the world. From literary sources, 1593 paired values δ18О-δ13С from 173 carbonatite occurrences of the world were collected. This report exceeds all previously published reports on С-О isotopes in carbonatites by quantity of the used values and carbonatite occurrences. Statistical data analysis is performed on diagrams in the coordinates δ18О (‰, V-SMOW) - δ13С (‰, V-PDV). For each carbonatite occurrence, not only the arithmetic mean values are calculated, but also the regression line. Distinct linear trend of δ18О-δ13С values is found in half of the carbonatite occurrences. The starting, middle, and ending points of the trend line are determined. The slope of the trend line (angular coefficient) varies over a wide range. The trend is dominated by an average angular coefficient of 0.30 (positive correlation δ18О-δ13С). In the literature, it is associated with the Rayleigh high-temperature fractionation of carbonatite melts or with their sedimentary contamination. Half of the carbonatite occurrences do not show a linear trend of δ18О-δ13С values, probably due to the combined action of multidirectional trends. The initial ratio 87Sr/86Sr in the used carbonatite occurrences varies from 0.701 to 0.708. Statistics show no correlation of 87Sr/86Sr with the δ18О-δ13С system.

Rising trends of global precipitable water vapor and its correlation with flood frequency

Using 4 global reanalysis data sets, significant upward trends of precipitable water vapor(PWV) were found in the 3 time periods of 1958-2020, 1979-2020, and 2000-2020. During 1958-2020, the global PWV trends obtained using the ERA5 and JRA55 data sets are 0.19 ± 0.01 mm per decade(1.15 ± 0.31%)and 0.23 ± 0.01 mm per decade(1.45 ± 0.32%), respectively. The PWV trends obtained using the ERA5,JRA55, NCEP-NCAR, and NCEP-DOE data sets are 0.22 ± 0.01 mm per decade(1.18 ± 0.54%),0.21 ± 0.00 mm per decade(1.76 ± 0.56%), 0.27 ± 0.01 mm per decade(2.20 ± 0.70%) and 0.28 ± 0.01 mm per decade(2.19 ± 0.70%) for the period 1979-2020. During 2000-2020, the PWV trends obtained using ERA5, JRA55, NCEP-DOE, and NCEP-NCAR data sets are 0.40 ± 0.25 mm per decade(2.66 ± 1.51%),0.37 ± 0.24 mm per decade(2.19 ± 1.54%), 0.40 ± 0.26 mm per decade(1.96 ± 1.53%) and 0.36 ± 0.25 mm per decade(2.47 ± 1.72%), respectively. Rising PWV has a positive impact on changes in precipitation,increasing the probability of extreme precipitation and then changing the frequency of flood disasters.Therefore, exploring the relationship between PWV(derived from ERA5 and JRA55) change and flood disaster frequency from 1958 to 2020 revealed a significant positive correlation between them, with correlation coefficients of 0.68 and 0.79, respectively, which explains the effect of climate change on the increase in flood disaster frequency to a certain extent. The study can provide a reference for assessing the evolution of flood disasters and predicting their frequency trends.

Long-Term Trends in Pre-Summer Daytime and Nocturnal Extreme Hourly Rainfall in a Coastal City of South China

The long-term trends in the occurrence frequency of pre-summer daytime and nocturnal extreme hourly rainfall(EXHR) during 1988-2018 in Hong Kong and their spatial distributions are examined and analyzed. Despite a significant increasing trend observed in the occurrence frequency of pre-summer EXHRs during the investigated period,the increase in daytime and nocturnal EXHRs show distinct spatial patterns. Nocturnal EXHRs show uniform increasing trends over the entire Hong Kong. However, the increase in daytime EXHRs is concentrated over the northern or eastern areas of Hong Kong, indicating a downstream shift of pre-summer EXHRs in Hong Kong with regard to the prevailing southwesterly monsoonal flows in south China. The clustering of weather types associated with daytime and nocturnal EXHRs further reveals that the increase in EXHRs over Hong Kong are mainly contributed by the increase of the events associated with southwesterly monsoonal flows with relatively high speeds. During the past few decades, the southwesterly monsoonal flows at coastal south China have undergone a substantial weakening due to the increased surface roughness induced by the urbanization over the Guangdong-Hong Kong-Macao Greater Bay Area since 1990s,leading to enhanced low-level convergence and thus significant increase in EXHRs at coastal south China. Meanwhile,daytime sea-wind circulation at coastal south China is markedly enhanced during the investigated period, which is the main reason for the northward shift of daytime EXHRs in Hong Kong. In addition, the blocked southwesterly monsoonal flows at coastal south China are detoured eastward, leading to stronger convergence and increase in EXHRs at eastern coast of Hong Kong, especially during daytime, when the easterly sea winds prevail at the region.

近40年西藏昼夜降水量时空变化特征

基于1981—2020年西藏38个气象站点逐小时降水量资料,采用线性倾向估计、Pearson相关系数、Mann-Kendall突变检验等方法,分析近40年西藏昼夜降水量和夜降水率时空变化特征。结果表明:西藏多年平均的年昼降水量总体上自东向西减少,年夜降水量由东南向西北递减,夜降水量大于昼降水量;雅鲁藏布江中游是西藏夜降水率的中心地带;春季昼夜降水量与海拔高度相关性最显著,夏秋两季和全年的昼夜降水量与经度相关系数最大;夜降水率,在冬季是高纬地区大于低纬地区,而在夏秋两季则是高海拔地区小于低海拔地区。近40年,西藏73.7%的站年昼夜降水量均趋于增加,57.9%的站年夜降水率呈减少趋势,63.2%的站夜降水量变化趋势大于昼降水量;西藏平均年昼夜降水量均呈增加趋势且夜降水量增速大于昼降水量,主要表现在春夏两季;因冬春秋三季夜降水率均减小,导致年夜降水率趋于减小。从年代际变化来看,近40年中,20世纪80年代是年昼夜降水量最少的年代,最大值分别出现在21世纪10年代和20世纪90年代;夜降水率则在20世纪80年代最高、21世纪10年代最低。Mann-Kendall突变检验显示,西藏仅有春季昼夜降水量、冬季夜降水量分别在20世纪90年代末和21世纪初发生了气候突变,前者增多,后者变少;2004年、2011年和2009年分别是冬季、春季和年夜降水率的突变时间。

气候变化背景下西藏高原地区界限温度时空变化特征

受全球气候变化影响,农牧业生产面临较大风险,研究界限温度时空变化对调整农业种植结构,实现农业可持续发展具有重要意义。利用近40a(1981-2020年)西藏38个气象站点逐日平均气温观测数据,采用线性倾向估计、Person系数、Mann-Kendall、优势分析等方法,分析了气候变暖背景下近40a西藏≥0℃、≥5℃和≥10℃界限温度(初日、终日、持续日数和活动积温)的时空变化特征。结果表明:(1)西藏≥0℃、≥5℃和≥10℃界限温度分布总体上表现为自东南向西北初日推迟、终日提早、持续日数缩短和积温减少的特征,并具有明显的海拔垂直地带性特征。1991-2020年与1981-2010年平均值比较,西藏各站三种积温均增加,以≥10℃积温增幅较大;绝大部分站点初日偏早、终日偏晚、持续日数偏多。(2)近40a西藏≥0℃、≥5℃和≥10℃初日、终日和持续日数的变幅以≥0℃最大,平均每10a初日提早3.2d、终日推迟3.5d、持续日数延长5.4d;积温增幅以≥10℃最大,为86.1℃·d·10a^(-1)。≥0℃、≥5℃持续日数增加是由于初日明显提早造成的,而≥10℃持续日数的增加因终日显著推迟导致。(3)≥0℃界限温度的线性倾向率(LTR),低海拔地区明显大于高海拔地区;≥5℃初日、积温LTR的最大值在低海拔地区,终日、持续日数LTR的最大值在中高海拔地区(3500-4000m);≥10℃初日LTR在中高海拔地区最大,终日、持续日数和积温LTR最大值出现在海拔4000-4500m地区。(4)20世纪80年代≥0℃、≥5℃和≥10℃初日偏晚、终日偏早、持续日数偏短、积温偏低;90年代初日、终日和持续日数正常,积温仍偏低;进入21世纪后,初日偏早、终日偏晚、持续日数增加、积温明显偏高,以21世纪10年代最明显。(5)≥5℃终日突变最早,发生在20世纪90年代初;≥10℃终日突变最晚,在21世纪10年代中期;初日、积温的突变分别出现在20世纪90年代中后期和21世纪初,持续日数突变点发生在20世纪90年代后期至21世纪中前期。

百色市冬季农业气候资源变化特征及未来趋势预估

为了应对气候变化对农业气候资源的影响,本研究围绕百色市冬季农业气候资源的合理开发利用展开。基于1970年12月-2023年2月期间,百色市12个国家气象观测站的逐日平均气温、降水量、日照时数数据,以及高分辨率区域气候模式RegCM4.4预估数据,采用线性趋势分析、Mann-Kendall突变检验、小波分析等方法,深入探讨了百色市冬季农业气候资源的分布特性、历史演变规律及未来变化趋势。研究发现,(1)百色市冬季热量资源较丰富,平均气温、≥10℃积温以右江河谷最高,北部山区最低;降水量具有南部多、北部少的特点;日照时数右江河谷北部和中部普遍高于其他地区。(2)1971-2023年百色市冬季气候呈暖湿化的趋势,冬季平均气温、≥10℃积温总体上均呈显著上升趋势,变化速率分别为0.18℃/10a、27.30℃·d/10a,均在1991年左右出现增高突变;降水量总体呈显著增加趋势,变化速率为5.27 mm/10a,在2010年出现增多突变;冬季日照时数呈显著减少趋势,变化速率为-10.36 h/10a。研究时段内4个要素均存在10~16 a的年代际尺度变化周期。(3)未来变化预估结果显示,在RCP4.5和RCP8.5情景下,2024-2080年百色市冬季平均气温和≥10℃积温均呈显著上升趋势,降水量变化趋势不显著;日照时数在RCP4.5情景下呈显著增加趋势。气候变暖给百色市冬季农业生产带来更好的热量条件,但降水量、日照时数波动变化较大,可能增加农业生产的不稳定性。

近50年浙江沿海地区降水变化特征分析

基于1971—2020年浙江沿海地区38个气象站点的逐日降水资料,运用线性倾向估计、滑动平均、Mann-Kendall检验等方法,对该地区近50年的降水变化特征进行了系统分析.结果表明:浙江沿海地区的降水量、极端降水强度及极端降水天数均呈现上升趋势;北部、中部沿海地区的降水量的年代际变化特征均呈现“少→多→少→多”的变化过程,而南部沿海地区则呈现“少→多”的变化过程;突变性检验的地区差异明显,北部沿海地区年降水量的突变现象出现在2013年,中部沿海地区出现在1973年和2012年,而南部沿海地区在20世纪70—80年代存在多个突变点;研究区的极端降水格局主要受热带气旋等因素的影响.该结果可以为浙江沿海地区的防灾减灾、海岸资源管理等提供科学依据和决策参考.

义昌江流域水质水量演变规律分析

研究义昌江流域降水量、径流量和水质指标演变规律,可为流域水资源开发利用、水环境保护和水生态改善提供数据支撑。运用线性趋势回归检验法研究其变化趋势,采用有序聚类分析法对其进行突变分析;分析水质指标时空变化,并进行水质评价;基于Pearson相关分析和双累积曲线法,研究义昌江流域水质变化的原因。结果表明:降水量、径流量、溶解氧、高锰酸盐指数、氨氮、粪大肠菌群变化趋势不明显。一般情况下,下游大冲口断面水质比上游断面好;从季节变化来看,冬季水质大部分合格、水质较好;从年变化来看,水质变化波动;径流对溶解氧、氨氮的影响比降水和水温更大,水温对高锰酸盐指数、粪大肠菌群的影响比降水和径流更大;水质指标变化受自然因素和人类活动共同影响。

Variations Trend of Soil Temperature at Deep Layers in Xining from 1961 to 2010

[Objective] The aim was to analyze the changes trend of mean earth temperature at 0.8, 1.6 and 3.2 m deep to the ground in Xining from 1961 to 2010. [Method] Using the data of monthly mean soil temperatures at 0.8,1.6 and 3.2 m in Xining from 1961 to 2010, the linear trend, climatic anomalous and climate abrupt of deep soil temperature during recent 50 years were analyzed by using of linear trend analysis, accumulated variance and signal noise ratio methods. [Result] In terms of linear trend, the annual mean soil temperatures at 0.8 m in recent 50 years, as well as 1.6 and 3.2 m in recent 45 years displayed a weak increasing trend in Xining. Comparing with the average air temperature in the same period, the rising range of deep soil temperature is obvious less. The average soil temperatures at 0.8 m was the highest in 1980s, but it was the lowest in the 1960s. In spring, autumn and winter in the 1980s, the average soil temperature was a little higher than many other years at 1.6 m. In four seasons in the 1980s, the average soil temperature was obvious higher at 3.2 m. The annual soil temperatures at 0.8 m were anomalous warm in 1991, and from 1987 to 1992, as well as in 1994, 2007 and 2009. The annual soil temperatures at 3.2 m were anomalous warm. In the 1990s, there were four years which were anomalous warm at 3.2 m, as well as five years at 0.8 m and five years at 1.6 m. [Conclusion] The study provided theoretical basis for the development of climate changes in Xining.

蒙江流域近60年水沙演变特征研究

基于1960-2020年蒙江流域日降水资料、蒙江控制站太平站径流和输沙资料分析蒙江流域降水量、径流量和输沙量的演变特征及原因;运用线性趋势回归检验法分析其趋势成分;采用Mann-Whitney-Pettitt突变点分析法对其进行突变分析;采用Morlet小波分析法分析其周期成分。结果表明:除夏季降水量、径流量、输沙量和冬季降水量呈不明显的减少趋势外,其余序列呈不明显的增加趋势;年降水量、年径流量和年输沙量呈不明显的增加趋势,没有发生显著突变;年降水量序列存在4年、7年、20年、45年左右的周期;年径流量序列存在3年、7年、19年、50年左右的周期;年输沙量序列存在4年、6年、11年、16年、46年左右的周期;人类活动是引起蒙江流域年输沙量减少的主导因素。

1981-2020年河南省近地面风速时空分布特征

利用1981-2020年河南省日平均10 m风速观测资料,对河南省风速的时空分布特征进行了分析评估。结果表明,河南省风速的气候态具有明显的季节循环特征,在冬、春季节地表风速较大,夏、秋季节风速较小,并且呈现出东强西弱的空间分布特征。在年循环中2月到3月风速增幅最大,其余月份间的风速演变较为平缓。在风速变化趋势方面,空间分布主要表现为西升东降的特征,豫西从过去风速最弱的地区一跃成为近10年风速最大的地区,这也与其他地区风速整体变弱有关。风速EOF的第二模态表明,河南省风速同时也具有一定的年代际变化特征。此外,风速2-9年的年际变率弱于年代际的,即风速的短期变化具有平稳性;但在气候变化的大背景下,出现了系统性的变化趋势,且具有明显的区域性差异。

Trend analysis of relative sea level rise or fall of the tide gauge stations in the Pacific

On the basis of the analytical results of the period components of monthly mean sea level of 236 stationsin the Pacific, the period components plus linear trend are ed to fit the monthly mean sea level series. The statisticalresults of linear trend Coefficients of these stations indicate that, if the abnormal values of sea-level rise and fall are neglected, the average rise rate of relative sea level in the Pacific is 1. 16 mm/a. Affected by nonuniformity Of land subsidence and other factors, the regional change of relative sea level rise or fall in the Pacific is greater. In the light of thepositive or negative values of linear trend coefficients as well as the geographical position of the sea area, zoning is madeof the sea level rise or fall in the Pacific including the coastal areas of China and Southeast Asia to obtain the averagerate of rise or fall in each sea area. The rise or fall trends of relative sea level obtained for the entire Pacific Ocean,west coast of North America, the northern and central South America, the greater part of the tropical Pacific and thecoastal Islands of Japan are basically in keeping with the other relevant results. The regional average estimated result ofthe relative sea level in the coast of East Asia is on the rise while the estimated results provided by Barnett tend todrop; the main cause of this nonuniformity is the number of stations selected and the distributional density.

毕节市秋绵雨时空特征分析

【目的】研究毕节市秋绵雨特征,对该地区秋收秋种农事安排具有指导意义。【方法】利用毕节市8个国家气象观测站1960—2022年9—11月逐日降水、日照资料,采用线性趋势和小波分析法,统计分析毕节市无日照条件下秋绵雨时空变化特征。【结果】1960—2022年,毕节市秋季降水量与日照时数均呈现下降趋势,无日照条件下降水量在时间上存在5 a、9 a、17 a、30 a的周期变化特征,主周期为17 a;毕节市东部受秋绵雨的影响较大,西部相对较小,总体上秋绵雨出现的频次在时间序列上呈波动下降趋势,有利于农业生产,且该地区秋绵雨集中出现在10月,9月中旬前完成秋收晾晒工作能有效避免秋绵雨的影响。【结论】近63 a,轻、中、重、特重等级秋绵雨发生的频次占比分别为44.1%、34.2%、18.5%、3.2%,且轻级秋绵雨存在6 a、20 a和32 a的变化周期,中级秋绵雨存在5 a、8 a、17 a和28 a的变化周期,重级秋绵雨存在7 a、18 a、35 a的变化周期,特重级秋绵雨存在13 a、21 a、41 a的变化周期,不同等级秋绵雨空间分布上整体呈东多西少分布。

重庆万盛雷电活动特征研究

利用重庆万盛国家气象观测站1978~2012年人工观测的雷暴资料和重庆市闪电监测网2008~2020年系统监测的万盛闪电定位资料,采用线性回归趋势方程、气候倾向率、Mann-Kendall突变检验、Morlet小波分析等方法对雷暴日和雷电日进行统计和差异性分析,得到万盛的雷电活动时间分布特征。

顾及气候时滞效应的黄河流域NDVI演变归因分析

采用Sen趋势分析和Mann-Kendall显著性检验、重力模型、多元线性回归方程、时滞偏相关、残差分析等地理统计方法,分析了黄河流域归一化植被指数(normalized difference vegetation index,NDVI)时空变化特征及其与气候的响应机制,评估了人类活动对NDVI的影响程度,得出以下结论:研究期内,流域内植被NDVI总体呈上升趋势,重心主要分布在流域东南部,东南部的NDVI增速增量明显大于西北部;流域内大部分地区的植被NDVI在生长季是以气温作为主要驱动因子;NDVI在植被生长季对气温的响应主要滞后约1个月,对降水的响应主要滞后约2个月;人类活动对流域内NDVI的影响程度由东南向西北递减,大部分地区的人类活动对植被NDVI起促进作用.

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959-2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s^(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.

The trend on runoff variations in the Lhasa River Basin

Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of the two hydrological stations （Lhasa and Tanggya） and the meteorological data of the three meteorological stations （Damxung, Lhasa and Tanggya）. The trends and the change points of runoff and climate from 1956 to 2003 were detected using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between runoff and climate change were analyzed using multiple linear regression. The major results could be summarized as follows： （1） The annual mean runoff during the last 50 years is characterized by a great fluctuation and a positive trend with two change points （around 1970 and the early 1980s）, after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides, the monthly mean runoff with a positive trend is centralized in winter half-year （November to April） and some other months （May, July and September）. （2） The trends of the climate change in the study area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter season.