Spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River during the period 2002–2011 based on the Advanced Microwave Scanning Radiometer for the Earth Observing System(AMSR-E) data

Detecting near-surface soil freeze-thaw cycles in high-altitude cold regions is important for understanding the Earth＇s surface system, but such studies are rare. In this study, we detected the spatial-temporal variations in near-surface soil freeze-thaw cycles in the source region of the Yellow River（SRYR） during the period 2002–2011 based on data from the Advanced Microwave Scanning Radiometer for the Earth Observing System（AMSR-E）. Moreover, the trends of onset dates and durations of the soil freeze-thaw cycles under different stages were also analyzed. Results showed that the thresholds of daytime and nighttime brightness temperatures of the freeze-thaw algorithm for the SRYR were 257.59 and 261.28 K, respectively. At the spatial scale, the daily frozen surface（DFS） area and the daily surface freeze-thaw cycle surface（DFTS） area decreased by 0.08% and 0.25%, respectively, and the daily thawed surface（DTS） area increased by 0.36%. At the temporal scale, the dates of the onset of thawing and complete thawing advanced by 3.10（±1.4） and 2.46（±1.4） days, respectively; and the dates of the onset of freezing and complete freezing were delayed by 0.9（±1.4） and 1.6（±1.1） days, respectively. The duration of thawing increased by 0.72（±0.21） day/a and the duration of freezing decreased by 0.52（±0.26） day/a. In conclusion, increases in the annual minimum temperature and winter air temperature are the main factors for the advanced thawing and delayed freezing and for the increase in the duration of thawing and the decrease in the duration of freezing in the SRYR.

Spatio-temporal reconstruction of air temperature maps and their application to estimate rice growing season heat accumulation using multi-temporal MODIS data

The accumulation of thermal time usually represents the local heat resources to drive crop growth.Maps of temperature-based agro-meteorological indices are commonly generated by the spatial interpolation of data collected from meteorological stations with coarse geographic continuity.To solve the critical problems of estimating air temperature(T a) and filling in missing pixels due to cloudy and low-quality images in growing degree days(GDDs) calculation from remotely sensed data,a novel spatio-temporal algorithm for T a estimation from Terra and Aqua moderate resolution imaging spectroradiometer(MODIS) data was proposed.This is a preliminary study to calculate heat accumulation,expressed in accumulative growing degree days(AGDDs) above 10 ℃,from reconstructed T a based on MODIS land surface temperature(LST) data.The verification results of maximum T a,minimum T a,GDD,and AGDD from MODIS-derived data to meteorological calculation were all satisfied with high correlations over 0.01 significant levels.Overall,MODIS-derived AGDD was slightly underestimated with almost 10% relative error.However,the feasibility of employing AGDD anomaly maps to characterize the 2001-2010 spatio-temporal variability of heat accumulation and estimating the 2011 heat accumulation distribution using only MODIS data was finally demonstrated in the current paper.Our study may supply a novel way to calculate AGDD in heat-related study concerning crop growth monitoring,agricultural climatic regionalization,and agro-meteorological disaster detection at the regional scale.

Contrast patterns and trends of lapse rates calculated from near-surface air and land surface temperatures in China from 1961 to 2014

The near-surface lapse rate reflects the atmospheric stability above the surface.Lapse rates calculated from land surface temperature(γTs)and near-surface air temperature( γTa )have been widely used.However,γTs and γTa have different sensitivity to local surface energy balance and large-scale energy transport and therefore they may have diverse spatial and temporal variability,which has not been clearly illustrated in existing studies.In this study,we calculated and compared γTa and γTs at^2200 stations over China from 1961 to 2014.This study finds that γTa and γTs have a similar multiyear national average(0.53°C/100 m)and seasonal cycle.Nevertheless,γTs shows steeper multiyear average than γTa at high latitudes,and γTs in summer is steeper than γTa ,especially in Northwest China.The North China shows the shallowest γTa and γTs,then inhibiting the vertical diffusion of air pollutants and further reducing the lapse rates due to accumulation of pollutants.Moreover,the long-term trend signs for γTa and γTs are opposite in northern China.However,the trends in γTa and γTs are both negative in Southwest China and positive in Southeast China.Surface incident solar radiation,surface downward longwave radiation and precipitant frequency jointly can account for 80%and 75%of the long-term trends in γTa and γTs in China,respectively,which provides an explanation of trends of γTa and γTs from perspective of surface energy balance.

The potential connection between China surface air temperature and the Atlantic Multidecadal Oscillation(AMO) in the Pre-industrial Period

One recent study by using instrumental records suggested the correlation between East Asian surface air temperatures(EATs)and the Atlantic Multidecadal Oscillation(AMO)reaches the maximum when the former leads the latter by 5–7 years.This seems to disagree with a previous well-realized point that the AMO modulates the decadal variation of EATs,since the atmosphere responds swiftly to sea surface temperature anomalies(SSTA)if therein.It implies that the AMO-EATs correlation should reach the maximum when they are simultaneous or the AMO leads EATs slightly,rather than that the EATs lead the AMO.Thus,this poses an issue about the reality of the newly found lead-lag correlation.Because the instrumental record in the natural climate system may be contaminated by human activities,the EATs-AMO lead-lag correlation derived from the instrumental records may not be a realistic connection of the natural climate system.Thus,whether the connection also exists in the proxies prior to the industrial is essential to answer the issue.In this study the EATs-AMO lead-lag connection is analyzed by using the reconstructed data in the last 500 years,together with the control experimental data with the prescribed pre-industrial forcing in a multiple of coupled climate system models,which attend the international CMIP5 program.The results suggest that the connection,the EATs lead the AMO,also exists in the period from the Little Ice Age(LIA)to the industrial,1500–1860AD.Therefore,the connection may be realistic in the natural climate system.The mechanisms for the connection are then discussed briefly.The results from this paper provide some insights into the connection of the AMO with East Asian climate.

青藏高原东北部MODIS地表温度重建及其与气温对比分析

通过遥感获取地表温度(地温,LST)可以弥补气象站LST数据局地性的不足。但受某些因素影响,遥感LST影像存在噪音像元,影响了LST数据的应用。本文提出了一种基于高程-温度回归关系的空间重建算法,对2008年青藏高原MODIS LST影像异常低值像元进行了重建,得到空间完整的LST时间序列。分别将原始LST和重建LST与研究区62个气象站最高气温进行对比分析,结果表明,重建前后LST与最高气温一致性很好,相关系数分别为0.88和0.91,各气象站平均相关系数达到0.898,LST一般高于气温,平均偏差为6.98℃。地气温差与海拔、土地覆盖、季节和噪音水平有关。海拔越高,地气温差越大;植被覆盖越好,地气温差越小;温度越高,温差越大。研究还发现,重建后的数据在森林覆盖区仍然残留噪音,这需要结合LST的质量控制信息做进一步研究。

以树轮宽度重建秦岭中段分水岭地区1—7月平均气温

根据秦岭中段分水岭地区秦岭落叶松树轮宽度指标,建立了该地区1814—2003年的树轮标准化年表。分析表明,该地标准化年表与当年1—7月平均气温显著相关。在此基础上设计转换方程,利用多元回归技术重建了秦岭中段分水岭地区的1—7月平均气温,重建序列的方差解释量为41.2%(F=15.062,p<0.0001),重建序列显示在过去190a中气温较低的时段主要有1814—1850年和1876—1889年;偏暖期主要有1851—1875年和1890—1933年;而1934—1990年这一时期气温变化幅度较小,气温相对比较稳定;1990年之后升温明显。

珠海小规模溪流水温与气温关系研究

使用最小二乘曲线拟合法、相关分析和互相关分析法，对中山大学珠海校区滨海水循环综合试验基地监测的2006年8月-2009年6月溪流水温、水位及气温数据进行分析。发现小规模溪流水温-气温可以用线性模型和logistic模型较好拟合，水温波动相对气温存在2．0h位相延迟，水温一气温相关程度与水位值呈负相关关系；使用Moflet小波滤波、功率谱分析及小波方差计算等方法对水温与气温的日周期、半日周期及季节性周期成分进行研究，探讨其周期大小以及周期成分能量等问题。

近50a青藏高原地面气温序列的重建

利用NCEP/NCAR500hPa高空再分析资料插补得到青藏高原1950—2000年50个海拔在3000m以上台站500hPa完整可靠的月平均温度序列。基于青藏高原地面气温和其上空500hPa温度有着密切关系,设计了这50个台站地面月平均温度序列的回归方案,用回归估计值将近50a各台站的现有月平均气温记录进行补齐、延长,得到重建的高原台站完整连续的地面月平均气温资料,并对回归效果进行独立样本实验。重建的青藏高原地面气温资料能够真实地反应高原实际气温的变化特征。

树轮记录的川西金川1713-2010年6月平均气温变化

利用采自川西高原金川情人海沟的云杉树轮样本,分析了树轮宽度与气候要素的关系。结果表明:树轮宽度指数与金川气象站6月平均气温具有显著的正相关关系。利用标准化树轮宽度指数重建了该区域1713—2010年6月平均气温序列,交叉检验及各项检验的参数表明重建方程是稳定可靠的。近298年来川西金川6月平均气温为18.2℃,经历了3个暖期和4个冷期。暖期时段为1825—1839、1854—1892和1951—1961年;冷期时段为1792—1804、1842—1853、1864—1893和1911—1924年。周期分析结果表明,重建序列存在2～3、7～8、20～30、32～64和70～130a的变化周期。

煤矿区重构土壤剖面水气变化及其对温度梯度的响应

煤矿区用煤矸石作为基质进行土壤重构,恢复生态环境和土地复垦的立地条件工程大量存在。但是,煤矸石氧化放热过程会对重构土壤剖面的水气变化产生影响,进而影响矿区生态修复的效果。为了研究重构土壤的水气运动特征及其对温度梯度的响应,设计了一种重构土壤水气热耦合运移室内模拟装置。在重构土壤不同深度布设温湿度传感器连续监测重构土壤剖面含水量和温度,利用CO_(2)体积分数检测仪测定不同深度CO_(2)体积分数,并通过底部的加热装置对重构土壤进行加热,研究重构土壤温度分布及其对水气运动的影响。结果表明:Hydrus-1D软件能较好地模拟重构土壤剖面体积含水量分布,但水分入渗过程存在明显的滞后性,水分在土壤层累积。气体在扩散过程中也表现出了明显的滞后性,在80 cm矸石层累积。当底部加热时,重构土壤剖面会形成稳定的温度梯度。在温度梯度的作用下,重构土壤中的水分会从底部向上运动,导致底层含水量明显降低,而其他层的含水量均明显上升,其中60 cm层的含水量增速最大,为0.057%/h。此时,气体易在矸石层及层间界面累积,并且累积效应随着温度梯度的增加而增强。温度和含水量均会影响重构土壤气体的扩散,但温度梯度的增加会削弱含水量对气体扩散的影响。另外,在重构土壤层间界面可能存在一个“障碍带”,当水分和气体接触到层间界面“障碍带”时开始受阻,从而导致水分在土壤层开始累积,气体在矸石层及层间界面累积。

SCL与中国东部气候年代际变化

据宇地磁耦合原理 ,利用太阳黑子周期长度 (SCL)的变化及其与地磁场 (文中主要考虑地热 )的关系 ,模拟计算并重建了中国东部历史时期的气温序列变化 ,除了个别时段外 ,模拟曲线与修正后的竺可桢曲线十分相似 ;分析了 2 5 0 0a来中国东部气候的年代际变化 .结果表明 ,该曲线能较好地再现 2 5 0 0a来中国东部气候的冷暖变化 .对竺氏曲线中有争议的几个冷暖时段 ,如公元 15 0— 35 0年的温暖期、10 5 0— 115 0年的小气候适宜期等 ,模拟结果与后来研究者分析的结果相合 .中唐至五代的气候冷暖交替变化不稳定 .

基于公共建筑节能改造的室温调控方法

公共建筑能耗已成为我国建筑中的能耗大户,其暖通空调能耗也越来越大。文中在阐述公共建筑节能改造重要性的基础上,对暖通空调系统能耗进行了分析,研究了室温变化对建筑节能及室内热舒适的影响程度。进而针对不同的供暖空调方式,研究提出了相应的室温调控方法,这对于公共建筑的节能改造有一定的参考价值。

基于热湿分控模式的电子厂房空调系统节能改造

根据电子元器件生产车间显热负荷大,湿负荷小的特征,结合空调系统及工艺冷却不同的冷冻水温度需求,采用热湿分控空气处理模式对空调系统进行了综合节能改造,构建了高低温双冷源系统,取消了板式换热器及三次冷冻水泵,增加了自控系统对空调系统进行动态优化和运行调节。结果显示,改造后系统全年运行节能率为25.9%~32.8%,不仅能较好地满足生产工艺对环境的需求,且运行稳定,达到了预期的目的。

利用树轮宽度重建黄河源区1618—2009年5—6月最高气温

利用采集自青海省雪山乡的祁连圆柏建立树轮宽度标准年表,将标准年表与黄河源区内4个气象站各气象要素作相关分析,结果显示整个源区5—6月最高气温与标准年表相关性最显著,相关系数为-0.65。根据相关分析结果,重建了黄河源区1618—2009年5—6月最高气温距平序列,重建方程经过逐一剔除检验,方差解释量达42.2%,具有一定的可靠性。重建序列在近400年间先后经历了8个较暖时间段和8个较冷时间段,暖期时段有1644—1656、1727—1746、1786—1797、1817—1835、1860—1885、1916—1934、1952—1968和1992—2005年,冷期的时段分别为1632—1643、1657—1696、1747—1764、1798—1816、1836—1859、1898—1915、1935—1951和1969—1991年。对比本次重建序列与杂多、青藏高原东部以及长江源的气温重建序列,发现以上序列在公共时段变化趋势一致,另外,一些文献和历史记载也证实了此次重建的可靠性。

广州设计大厦建筑设备节能改造方案简陈

介绍广州设计大厦节能改造项目中所采用的控制策略,对机电设备进行的节能控制管理,及针对部分标准楼层的风机盘管、新风机采取的节能控制方式。

基于递归径向基神经网络的航空发动机盘腔瞬态壁温预测

针对航空发动机空气系统盘腔瞬态壁温动态预测难的问题,提出了一种基于径向基神经网络的递归预测模型。通过时序数据多维重构的方法建立训练样本,强化径向基神经网络对“时滞性”的预测能力,分析了模型固有超参数和由多维重构引入抽样控制参数对模型预测精度的影响。采用简化的典型盘腔壁面换热模型结合公开的试验历程转速数据,构建了供模型训练和测试的瞬态壁温数据样本,以递归调用模型的方式完成了对测试样本时序数据的预测和验证。结果表明,与常规的径向基神经网络预测模型相比,该模型的平均相对预测偏差由3.0%降低至0.45%,有效提升了模型的预测精度。为航空发动机盘腔瞬态壁温异常监控及超温排故问题提供了一种新的预判方法。

基于本征正交分解的环境温度分布快速预测模型研究

本文基于Karhunen-Loeve分解的原理,使用本征正交分解方法(Proper Orthogonal Decomposition,POD)对高维非线性的流动及传热过程进行降阶,获得研究对象所处流场的各阶模态以用于温度场的重构预测。将本征正交分解模型预测温度分布的准确度及响应速度和通过流动及传热控制方程的离散求解获取温度分布的过程进行对比,对比结果显示本征正交分解具有较高的准确度和更加敏捷的温度预测响应速度,并且其预测过程占用更少的计算资源。结果显示,每次离散求解流动及传热控制方程约耗时93 s,而使用本征正交分解模型获取热环境所需的时间约为6 ms,并且后者的平均泛化误差小于5%。

1618～2009年黄河源区夏季最高气温变化规律分析

利用已重建的黄河源区1618～2009年5～6月最高气温序列,对该序列的空间代表性,突变及周期进行分析,揭示其长时间尺度变化规律.空间相关分析结果表明,此次重建的5～6月最高气温序列对黄河源区乃至整个青藏高原地区都具有很好的空间代表性.采用Cramer、滑动t检验、M-K和Yamamoto 4种检验方法对重建序列进行突变检验,发现在过去近400年间序列主要产生了3次正突变和3次负突变.经小波分析以及功率谱检验发现重建的最高气温序列存在2～4 a、6～8 a、20～24 a和32～40 a的显著周期.

On the effects of landscape configuration on summer diurnal temperatures in urban residential areas: application in Phoenix, AZ

The impacts of land-cover composition on urban temperatures, including temperature extremes, are well documented. Much less attention has been devoted to the consequences of land-cover configuration, most of which addresses land surface temperatures. This study explores the role of both composition and configuration—or land system architecture—of residential neighborhoods in the Phoenix metropolitan area, on near-surface air temperature. It addresses two-dimensional, spatial attributes of buildings, impervious surfaces, bare soil/ rock, vegetation and the “urbanscape” at large, from 50 m to 550 m at 100 m increments, for a representative 30-day high sun period. Linear mixed-effects models evaluate the significance of land system architecture metrics at different spatial aggregation levels. The results indicate that, controlling for land-cover composition and geographical variables, land-cover configuration, specifically the fractal dimension of buildings, is significantly associated with near-surface temperatures. In addition, statistically significant predictors related to composition and configuration appear to depend on the adopted level of spatial aggregation.

How skillful was the projected temperature over China during 2002–2018?

Climate change has attracted significant attention due to its increasing impacts on various aspects of the world,and future climate projections are of vital importance for associated adaptation and mitigation,particularly at the regional scale.However,the skill level of the model projections over China in the past more than ten years remains unknown.In this study,we retrospectively investigate the skill of climate models within the Third(TAR),Fourth(AR4),and Fifth(AR5)Assessment Reports of the Intergovernmental Panel on Climate Change(IPCC)for the near-term projections of near-surface(2 m)air temperature changes in China.Those models are revealed to be skillful in projecting the subsequent climatology and trend of the temperature changes in China during 2002-2018 from several to ten years ahead,with higher scores for the climatology than for the trend.The model projections display cold biases against observations in most of China,while the nationally averaged trend is overestimated by TAR models during 2002-2018 but underestimated by AR4 models during 2008-2018.For all emission scenarios,there is no obvious difference between the equal-and unequal-weighted averages based on the arithmetic averaging and reliability ensemble averaging method respectively,however the uncertainty range of projection is narrowed after weighting.The near-term temperature projections differ slightly among various emission scenarios for the climatology but are largely different for the trend.