GI格局影响区域气温的尺度效应和空间分异特征——基于天津市的实证

绿色基础设施为应对气候变化提供了一种基于自然的解决方案,尤其在调节区域气温方面发挥着重要作用。既有关于绿色基础设施与区域气候关联性的研究主要关注规模数量对全局尺度气候因子的影响,对尺度变化及其空间异质性的讨论不足。以天津市为例,综合运用景观生态学和地理加权回归分析方法,在测度研究区绿色基础设施格局的基础上,深入探讨了绿色基础设施格局影响区域气温的尺度效应和空间作用规律。结果表明:1)绿色基础设施格局能够显著影响区域气温,且随着尺度增加各项格局指数与区域气温的相关程度均呈现先增大后减小的趋势,并在7km×7km尺度下达到峰值;2)各项格局指数与区域气温的相关程度整体上为面积类指数>聚集类指数>密度类指数>形状类指数;3)各项格局指数与区域气温的相关性具有空间非稳定性特征,其中半城市化地区的区域气温更易受到格局变化的影响。最后,提出以乡镇(街道)为单元的GI格局分区优化措施,以期为气候适应性规划设计和各类相关政策的制定提供科学指导。

1959—2005年我国冬季和夏季区域气温与日照、云量的相关分析

基于1959—2005年全国824站日平均气温和日照时数以及NCEP/NCAR总云量逐日资料,利用REOF方法,将我国冬、夏季平均气温分别分为4个和6个区。冬季4区为青藏高原以东、东北和内蒙古东部、青藏高原大部、新疆;夏季6区为西北东部和华北、长江黄河流域一带、西南南部和华南、东北和内蒙古东部、新疆中北部、南疆西部。除了夏季II区(长江黄河流域一带),冬季和夏季各区平均气温均呈上升趋势,且冬季的上升趋势更显著。消除总云量的影响后,除了冬季II区(东北和内蒙古东部),冬季和夏季平均气温与日照时数均呈正相关关系,但与冬季相比,夏季的正相关关系更显著;消除日照的影响后,在夏季I区(西北东部和华北大部)和VI区(南疆西部)以及冬季II区(东北和内蒙古东部),平均气温与总云量呈显著的负相关关系。

城市化进程对南京市区域气温变化的影响

20世纪90年代以来中国进入城市化快速发展阶段,城市规模迅速扩张,这在一定程度上对大气热环境产生了影响,如产生了城市热岛效应。文章基于南京气象站点观测数据、南京市统计年鉴以及landsat TM影像数据,选取人口密度、废气排放量、运营车辆、用电量、绿地覆盖面积、建成区面积6项指标构建城市化因子群,运用灰色关联度分析法对影响南京气温变化的因子群进行贡献度分析。首先,基于以往研究及南京市统计年鉴选取人口密度、废气排放量、运营车辆、用电量、绿地覆盖面积、建成区面积6项指标构建城市化因子群;其次,基于landsat TM影像数据利用监督分类方法提取建成区面积;最后,基于灰色关联度分析方法,定量计算出人口密度、废气排放量、运营车辆、用电量、绿地覆盖面积、建成区面积6项城市化因子分别对年均温、年最高温、年最低温、季均温、月均温以及不同时期温度均值的影响。研究发现,(1)1983─2011年期间,南京市气温呈明显递增趋势,20世纪90年代后期增温更为明显,1999─2007年年均温增长了1.50℃。(2)发现对于同一参考数列(年均温、月均温等)而言,其影响因子关联度整体排序是一致的:人口密度>建成区面积>废气排放量>运营车辆>用电量>绿地覆盖面积。(3)同一城市化因子对年均温变化、年最高温变化、年最低温变化的影响是不相同的。例如,人口密度对1983─2011年年均温变化影响最大,关联度达到了0.95;用电量、废气排放量和运营车辆对1983─2011年年最低温变化影响最大,其关联度分别为0.68、0.74、0.73。(4)同一城市化因子对不同月份气温变化的影响是不相同的,如人口密度与2月月均温之间的关联度最小,关联度为0.78;与3月月均温之间的关联度最大,关联度为0.93。(5)不同城市化因子随着时间的推移,对区域气温变化的影响也是不相同的。其中,人口密度、运营车辆以及建成区面积对气温变化的影响是立竿见影的效应;用电量和废气排放量对气温变化的影响是累加的效应;而城市绿地面积对气温的影响只是对温室气体吸收量多少的外在表现,一般绿地面积越多,吸收的温室气温也就越多,无附加影响。

不同空间插值方法在区域气温序列中的应用评估:以东北地区为例

建立高精度、长时间序列的气温数据集对研究气候变化、作物生长发育、灾害评估等都有着十分重要的意义。本文以1971-2000年东北地区104个气象站点的气候标准值数据及年值观测资料为基础,利用空间插值方法对该区年平均气温进行插值,并结合参考格点气温数据集,从误差指标、气温特征值及气温时序变化曲线等方面评估时、空尺度上各方法的插值精度。结果表明:空间尺度上,基于局部薄盘光滑样条(PTPSS)函数且以高程为协变量的年平均气温插值结果最优,其均方根误差为0.341℃,平均绝对误差为0.264℃,其次为协同克里格(以高程为协变量),再次为普通克里格;时间尺度上,基于PTPSS以高程为协变量的年平均气温时序曲线与参考格点气温曲线的变化趋势最符合,两个数据集的年平均气温平均值、最大值和最小值时序变化曲线的相关系数均大于0.9。可见,以高程为协变量的局部薄盘光滑样条函数法最适于东北地区年平均气温插值。

基于改进LSTMs模型的区域中长期气温预测方法研究

结合残差网络阶跃连接的优点,基于长短期记忆网络模型(LSTM)和双向长短期记忆网络模型(BiLSTM),提出了对区域中长期气温预测准确率较高的DeepLSTMs网络模型.利用主成分分析对哈尔滨2007-2018年逐时气象资料进行降维,得到温度预测的主要影响因素,对气象要素进行预处理和重构,并结合DeepLSTMs网络模型对哈尔滨市中长期气温进行了大量的预测实验.结果表明,利用DeepLSTMs网络模型对该地区中长期气温的预测精度高于比较所用方法.

2015年华南区域模式贵州区域2 m气温预报偏差分析

运用2015年华南区域模式08时起报的2 m气温和贵州区域84个国家站观测气温资料,得到2 m气温偏差场,对偏差场进行了年平均、季节平均、指标站时间演变特征分析和Taylor diagram分析及主分量分析。发现年平均和季节平均得出气温偏差在不同模式预报时次存在差异,午后到傍晚时段最为显著,且以24 h为周期演变,最大平均绝对误差在4℃左右。季节平均还反映出温度偏差冬季偏高、夏季偏低;春秋季节相对较为平稳,且为冬季与夏季两种位相的过渡期。指标站的偏差时间演变规律与年平均和季节平均的结论基本一致,但偏差值明显大于年平均和季节平均;指标站的最大偏差出现在偏差位相转化的春季和秋季中,在夏季最为平缓。不同站点间气温偏差时间演变存在明显差异,海拔、纬度、天气系统都会影响模式的气温预报,从而影响偏差时间演变规律。Taylor diagram表明季节间的气温偏差在天气环流形势稳定、无明显冷空气活动的夏季,月平均的偏差波动幅度较小;对于受频繁活动冷空气影响的冬季和环流转换的春季,月平均的偏差波动幅度较大。PCA得出方差比占绝对优势的第1特征向量都为同一位相,全部站点气温偏差表现为相同的变化趋势和同性的空间分布特征。从第2特征向量开始出现位相的分化,刻画偏差变化趋势和空间分布特征更突出细节。第1、2特征向量对应的时间函数存在低频振荡特征,主要周期为10~20 d,与冷空气的低频活动和东亚季风的低频振荡一致。这些结论是下一步模式气温订正工作的依据。

利用气温序列均一性分析判断区域自动站数据质量

通过构建参考序列、找出间断点、结果集成等步骤对兴安盟突泉县8个区域地面气象站逐日平均气温进行均一性检验。结果表明:区域地面气象站气温资料均一性状况良好,数据质量可靠。

青藏、伊朗高原春夏季高层热力异常与我国夏季气温的关系

首先利用EOF方法,分析了0°～180°E,0°～60°N范围内100,150,200,250,300,400,500hPa等层次上温度场的时空变化特征,结果表明,青藏、伊朗高原的热力异常在300hPa温度场上有明显的体现。然后利用SVD方法,分析了青藏、伊朗高原地区300hPa温度场异常与我国区域气温的关系,分析表明:(1)伊朗高原大部和青藏高原中部、西北部6～8月300hPa温度与我国长江流域和江淮之间同期的气温有显著的正相关关系;(2)青藏高原东部、西北部4～5月300hPa温度与我国长江流域偏南地区6～8月的气温有显著的正相关关系。

不同下垫面数据和城市冠层参数化方案对江苏气温影响的个例分析

利用中尺度数值模式WRF,分别选用新旧两种下垫面资料和不同城市冠层模型设计试验,以江苏一次秋末高温天气个例(2014年11月20—21日)为背景,研究城市化进程对气温的影响和可能机制。将模式结果与江苏国家气象观测站和地面加密区域自动站观测资料进行对比,并分析3组试验结果发现:(1)采用BEP城市方案对2 m气温、2 m相对湿度和10 m风速等物理量的日变化模拟最优。(2)相比USGS数据,MODIS较新地表覆盖变化数据能更真实反映研究区域当前地表类型分布情况,且能提高近地面风温湿要素空间分布的模拟。(3)分析不同试验模拟的地表能量平衡过程差异,发现相比UCM单层城市冠层方案,BEP多层城市冠层方案在白天能更好模拟出城市地区的温度升高以及相对应的地表感热通量和地面热通量的增加。

Performance of Regional Integrated Environment Modeling System (RIEMS) in the Simulation of Surface Air Temperature over East Asia

Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs).These advantages have drawn significant focus on RCM development in East Asia.The Regional Integrated Environment Modeling System,version 2.0 (RIEMS2.0),has been developed from an earlier RCM,RIEMS1.0,by the Key Laboratory of Regional ClimateEnvironment for Temperate East Asia (RCE-TEA) and Nanjing University.A numerical experiment covering 1979 to 2008 (simulation duration from 1 January 1978 to 31 December 2008) with a 50-km spatial resolution was performed to test the ability of RIEMS2.0 to simulate long-term climate and climate changes in East Asia and to provide a basis for further development and applications.The simulated surface air temperature (SAT) was compared with observed meteorological data.The results show that RIEMS2.0 simulation reproduced the SAT spatial distribution in East Asia but that it was underestimated.The simulated 30-year averaged SAT was approximately 2.0°C lower than the observed SAT.The annual and interannual variations in the averaged SAT and their anomalies were both well reproduced in the model.A further analysis of three sub-regions representing different longitudinal ranges showed that there is a good correlation and consistency between the simulated results and the observed data.The annual variations,interannual variations for the averaged SAT,and the anomalies in the three sub-regions were also captured well by the model.In summary,RIEMS2.0 shows stability and does well both in simulating the long-term SAT in East Asia and in expressing sub-regional characteristics.

Characteristics and Changes of Cold Surge Events over China during 1960-2007

This paper demonstrates regional characteristics, a long-term decreasing trend, and decadal variations in the frequency of cold surge events based on daily mean temperature and daily minimum temperature data in China's Mainland from 1960 to 2008. During these 48 years four high frequency centers of cold surge events were located in Xinjiang, central North China, northeast China, and southeast China. A main frequency peak of cold surge events occurs in autumn for the four regions and another peak is detected in spring over northeast China and southeast China. The regional pattern of cold surge frequencies is in accordance with the perturbation kinetic energy distribution in October December, January, and February April. The long-term decreasing trend ( 0.2 times/decade) of cold surge frequencies in northeast China and decadal variations in China are related to the variations of the temperature difference between southern and northern China in the winter monsoon season; these variations are due to the significant rising of winter temperatures in high latitudes.

Climate change in the twenty-first century over China: projections by an RCM and the driving GCM

A regional climate model(RegCM4)is used to project climate change over China in the twenty-first century under the RCP4.5 and RCP8.5 pathways.The driving GCM is CSIRO Mk3.6.0(hereafter referred to simply as CSIRO),and the simulation(hereafter referred to as CdR)is run at a grid spacing of 25 km.The focus of the present paper is on the changes in mean surface air temperature and precipitation in December–January–February(DJF)and June–July–August(JJA)over China.Validation of the model performances is provided first,followed by a comparison of future changes projected by CSIRO and CdR.Substantial warming in the future is simulated by both models,being more pronounced in DJF compared to JJA,and under RCP8.5 compared to RCP4.5.The warming shows different spatial patterns and,to a less extent,magnitude between CSIRO and CdR.Precipitation change shows a general increase in DJF and a mixture of increase and decrease in JJA.Substantial differences between the two models are found in for precipitation change in JJA.The paper further emphasizes the uncertainties in climate change projection over the region.

STUDY OF DOUBLE RAIN BANDS IN A PERSISTENT RAINSTORM OVER SOUTH CHINA

Using the U.S. National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data at 1°× 1° o resolution, analysis is performed on a persistent heavy rainfall event with two rain bands to the south of the Yangtze River during 17-22 June 2005. The northern rain band was related to the atmospheric mass adjustment of cold front precipitation and the associated ageostrophic feature to the rear right of subtropical westerly jets, while the southern counterpart formed under the joint influence of easterly/westerly jets and the South Asian high （SAH）. The ageostrophic wind field to the rear right of the easterly jet center gives rise to an anti-circulation that favors the genesis of the southern belt. The feature ofdu/dt 〈0 around the SAH ridge line and to the rear right of the easterly jet streak results in a strong v - vg〈O field in the vicinity of the rain region as well as to its south. When westerly jets move southward, an intense v Vg〉0 feature appears to the north of the rain region, i.e., behind the center of the westerly jets. The associated mass adjustment leads to vigorous divergence over the rain region, which is responsible for the strong precipitation from the warm sector of the front. Also, a θe front at the middle level of the southern rain band and the cold front favor the release of instable energy to enhance the rainstorm. The southern and northern fronts approach each other and the two rain belts merge into one.

Regional Climate Change and Uncertainty Analysis based on Four Regional Climate Model Simulations over China

Four sets of climate change simulations at grid spacing of 50 km were conducted over East Asia with two regional climate models driven at the lateral bounda- ries by two global models for the period 1981-2050. The locus of the study was on the ensemble projection of cli- mate change in the mid-21st century （2031-50） over China. Validation of each simulation and the ensemble average showed good performances of the models overall, as well as advantages of the ensemble in reproducing present day （1981 2000） December-February （DJF）, June-August （JJA）, and annual （ANN） mean temperature and precipitation. Significant wanning was projected for the mid-21st century, with larger values of temperature increase found in the northern part of China and in the cold seasons. The ensemble average changes of precipitation in DJF, JJA, and ANN were determined, and the uncertainties of the projected changes analyzed based on the consistencies of the simulations. It was concluded that the largest uncertainties in precipitation projection are in eastern China during the summer season （monsoon pre-cipitation）.

Trend in Observed and Projected Maximum and Minimum Temperature over N-W Himalayan Basin

Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.

Coupling methods of global climate models and regional climate models

The future climate dynamical downscaling method is that output of general circulation models( GCMs) is employed to provide initial conditions,lateral boundary conditions,sea surface temperatures,and initial land surface conditions to regional climate models( RCMs). There are two methods of downscaling: offline coupling and online coupling. The two kinds of coupling methods are described in detail by coupling the Weather Research and Forecasting model( WRF) with the Institute of Atmospheric Physics of Chinese Academy of Sciences Atmospheric General Circulation Model Version 4. 0( IAP AGCM4. 0) in the study. And the extreme precipitation event over Beijing on July 212012 is simulated by using the two coupling methods. Results show that online coupling method is of great value in improving the model simulation. Furthermore,the data exchange frequency of online coupling has some effect on simulation result.

Regional warming induced by urban surface expansion in Shanghai

To detect the impacts of urban surface expansion on surface air temperature at 2-m（SAT） in Shanghai, China, nested numerical integrations based on satellite-derived urban data between the 1980 s and 2010 s were performed using the Weather Research and Forecasting（WRF） model. Urban surface expansion induced an annual-averaged warming of 0.31 °C from 1980 to 2016 across the whole of Shanghai, showing the greatest intensity between 2010 and 2016. The values were 0.36, 0.78, and 0.75 °C over grids that were classified as urban in both time periods（U2 U）, landuse grids that changed from non-urban to urban（N2 U）, and urban areas（including U2 U and N2 U）, respectively, and revealed weak warming over the inner-ring areas because the urban surfaces had been there since the 1980 s, whereas warming areas were coincident with the outward expansion of the urban surface. Meanwhile, marked seasonal variations could be detected, which were greater in spring and summer but less in autumn and winter. The approximately homogenously distributed SAT maximum（weaker） and heterogeneously SAT minimum（stronger） contributed to the decreased diurnal temperature range. Regional warming induced by urban surface expansion was approximately 0.12 °C per decade, which accounted for 19% of the overall warming across the whole of Shanghai. The values were 0.11 °C per decade and 0.39 °C per decade over U2 U and N2 U, which accounted for approximately 17% and 42% of the overall warming, respectively, and resulted in approximately 41% of the overall warming over urban areas.

Runoff Responses to Climate Change in Arid Region of Northwestern China During 1960-2010

Based on runoff, air temperature, and precipitation data from 1960 to 2010, the effects of climate change on water resources in the arid region of the northwestern China were investigated. The long-term trends of hydroclimatic variables were studied by using both Mann-Kendall test and distributed-free cumulative sum （CUSUM） chart test. Results indicate that the mean annual air temperature increases significantly from 1960 to 2010. The annual precipitation exhibits an increasing trend, especially in the south slope of the Tianshan Mountains and the North Uygur Autonomous Region of Xinjiang in the study period. Step changes occur in 1988 in the mean annual air temperature time series and in 1991 in the precipitation time series. The runoff in different basins shows different trends, i.e., significantly increasing in the Kaidu River, the Aksu River and the Shule River, and decreasing in the Shiyang River. Correlation analy- sis reveals that the runoff in the North Xinjiang （i.e., the Weigan River, the Heihe River, and the Shiyang River） has a strong positive relationship with rainfall, while that in the south slope of the Tianshan Mountains, the middle section of the north slope of the Tianshan Mountains and the Shule River has a strong positive relationship with air temperature. The trends of rtmoff have strong negative correla- tions with glacier coverage and the proportion of glacier water in runoff. From the late 1980s, the climate has become warm and wet in the arid region of the northwestern China. The change in runoff is interacted with air temperature, precipitation and glacier coverage. The results show that streamflow in the arid region of the northwestern China is sensitive to climate change, which can be used as a reference for regional water resource assessment and management.

Interannual and Seasonal Changes in the Ice Cover of Glacial Lakes in the Snowy Mountains of Australia

Seasonal ice cover is uncommon on Australian lakes. In the Snowy Mountains, there are five natural, seasonally ice-covered lakes including Lake Cootapatamba, the highest lake in Australia. Blue Lake is the only one of the five lakes with sufficient volume to be relatively independent of short-term changes in ambient temperature, and therefore is the lake most likely to be of use in tracking long-term regional climate change. Ice forms on Blue Lake near the winter solstice and ice-breakup occurs from late September to November. Timing of breakup is related to spring temperature and, as such, mirrors the timing of general snow thaw in the mountains. The existence of historic photographs taken of the lake at about the time of ice breakup allows for the possibility of reconstructing a history of alpine climate and in 1905 ice breakup was probably as late as mid-December.

Changes to the Natural Regional Boundaries in China During 1961-2007

Daily temperature data from 599 stations across China for the years 1961 to 2007 were used to analyze the changes in the natural regional boundaries. The results show that the accumulated temperature ≥10℃ and its duration changed dramatically from the end of 1990s to the early 21 st century. The amplitude of natural regional boundaries was greater in the 21st century than it was in the 20th century. In the eastern region of China, the climatic zones were migrating generally northward, with the northern edge of the subtropical zone and the eastern section of the warm temperate zone showing an obvious northward shift of up to 1-3° of latitude. The climatic zones moved south in the Qinghal-Tibet Plateau, western Inner Mongolia, and some areas of western Xinjiang, and slightly to the north in other parts of the western region.