Variation in road surface temperature due to topography and wind

Summary The present study involves a discussion of nocturnal temperature variation due to topography and prevailing wind speed. It is part of the ongoing project Applied climatology for increased traffic safety and road maintenance, which aims at a development of a local climatological model applicable to winter road conditions. The temperature recordings which are used are from sensors in the Swedish Road Weather Information System in the county of Skaraborg.During clear and calm nights, local air temperature differences have been related to different topographical environments. The main factors resulting in large temperature differences are the effect of wind shelter, stagnation or production of cold air, and of cold air advection.Variation in air temperatures during clear and windy nights has also been studied. At wind speeds higher than 4–5 m/s, the temperature variation is low. With decreasing wind speed the variation in temperature increases, but only for sensor sites which have some wind shelter by topography or vegetation.The air temperature variation which develops during clear nights affects the road surface temperature. In this paper, the connection between road surface temperature differences and air temperature variation is discussed. A linear relationship between the two variables exists.With 5 Figures     

冬季高速公路路桥温度变化规律及能量平衡分析

利用2009年10月-2010年3月湖北省武英高速凤凰关水库自动气象站逐时路、桥面温度和常规气象资料,分析了冬季典型天空状况（晴空、阴天）和天气过程（雾、降雨、降雪）中气温、路面温度和桥面温度的变化规律。结果表明,夜间桥面温度与气温接近,比路面温度低2℃,桥面0℃以下的低温维持时间为路面维持时间的2倍左右。利用下垫面能量平衡模型,分别计算冬季夜间晴空和阴天时路、桥面辐射能量收支变化情况,分析了夜间路面和桥面温度变化差异的原因,并对桥面比路面更易结冰的现象给出了理论解释。     

WP和NAO对中国东南部冬季温度的协同影响

利用NCEP/NCAR和ERA-Interim再分析资料,通过多元线性回归等分析方法,研究了西太平洋遥相关型(Western Pacific teleconnection,WP)和北大西洋涛动(North Atlantic Oscillation,NAO)的不同配置对中国东南部冬季气温的影响.结果 表明:WP正位相年,...     

A note on the relationship between temperature and water vapor over oceans, including sea surface temperature effects

An ideal and simple formulation is successfully derived that well represents a quasi-linear relationship found between the domain-averaged water vapor, Q (mm), and temperature, T (K), fields for the three tropical oceans (i.e., the Pacific, Atlantic and Indian Oceans) based on eleven GEOS-3 [Goddard Earth Observing System (EOS) Version-3] global re-analysis monthly products. A Q ? T distribution analysis is also performed for the tropical and extra-tropical regions based on in-situ sounding data and numerical simulations [GEOS-3 and the Goddard Cumulus Ensemble (GCE) model]. A similar positively correlated Q ? T distribution is found over the entire oceanic and tropical regions; however, Q increases faster with T for the former region. It is suspected that the tropical oceans may possess a moister boundary layer than the Tropics. The oceanic regime falls within the lower bound of the tropical regime embedded in a global, curvilinear Q ? T relationship. A positive correlation is also found between T and sea surface temperature (SST); however, for one degree of increase in T, SST is found to increase 1.1 degrees for a warmer ocean, which is slightly less than an increase of 1.25 degrees for a colder ocean. This seemingly indicates that more (less) heat is needed for an open ocean to maintain an air mass above it with a same degree of temperature rise during a colder (warmer) season [or in a colder (warmer) region]. Q and SST are also found to be positively correlated. Relative humidity (RH) exhibits similar behaviors for oceanic and tropical regions. RH increases with increasing SST and T over oceans, while it increases with increasing T in the Tropics. RH, however, decreases with increasing temperature in the extratropics. It is suspected that the tropical and oceanic regions may possess a moister local boundary layer than the extratropics so that a faster moisture increase than a saturated moisture increase is favored for the former regions. T,Q, saturated water vapor, RH, and SST are also examined with regard to the warm and cold “seasons” over individual oceans. The Indian Ocean warm season dominates in each of the five quantities, while the Atlantic Ocean cold season has the lowest values in most categories. The higher values for the Indian Ocean may be due to its relatively high percentage of tropical coverage compared to the other two oceans. However, Q is found to increase faster for colder months from individual oceans, which differs from the general finding in the global Q?T relationship that Q increases slower for a colder climate. The modified relationship may be attributed to a possible seasonal (warm and cold) variability in boundary layer depth over oceans, or to the small sample size used in each individual oceanic group.     

高速公路灾害性天气研究

:利用沪渝高速公路恩施-宜昌路段恩施附近的三岔口大桥(海拔708 m)自动站监测2013年6-8月(夏季)及2013年12月至2014年2月(冬季)逐日逐时次气象要素资料, 统计分析夏季、冬季路面温度与气温的变化特征及路面温度与气象因子的关系, 基于逐步引入因子线性回归分析方法建立路面温度统计模型, 并对模型的预报效果进行实验研究。结果表明:夏季路面最高温度受多种气象要素的影响, 与日最高气温、日平均气温、前一日路面最高温度、前一日路面平均温度呈正相关, 与相对湿度、24 h累计降水呈负相关。冬季路面最低温度与最低气温呈显著性相关。通过模型的效果实验, 发现夏季路面最高温度用日最高气温、日最小相对湿度及前一天物理量建立的模型预报结果与实况的变化趋势最为接近; 冬季路面最低温度用日最低气温、日最小相对湿度、日平均风速及前一天物理量建立的模型预报结果与实况的变化趋势最为接近。

     

Effects of meridional sea surface temperature changes on stratospheric temperature and circulation

Using a state-of-the-art chemistry-climate model,we analyzed the atmospheric responses to increases in sea surface temperature （SST）.The results showed that increases in SST and the SST meridional gradient could intensify the subtropical westerly jets and significantly weaken the northern polar vortex.In the model runs,global uniform SST increases produced a more significant impact on the southern stratosphere than the northern stratosphere,while SST gradient increases produced a more significant impact on the northern stratosphere.The asymmetric responses of the northern and southern polar stratosphere to SST meridional gradient changes were found to be mainly due to different wave properties and transmissions in the northern and southern atmosphere.Although SST increases may give rise to stronger waves,the results showed that the effect of SST increases on the vertical propagation of tropospheric waves into the stratosphere will vary with height and latitude and be sensitive to SST meridional gradient changes.Both uniform and non-uniform SST increases accelerated the large-scale Brewer-Dobson circulation （BDC）,but the gradient increases of SST between 60°S and 60°N resulted in younger mean age-of-air in the stratosphere and a larger increase in tropical upwelling,with a much higher tropopause than from a global uniform 1.0 K SST increase.     

An updated evaluation of the global mean land surface air temperature and surface temperature trends based on CLSAT and CMST

Climate Dynamics - Past versions of global surface temperature (ST) datasets have been shown to have underestimated the recent warming trend over 1998–2012. This study uses a newly updated...     

赤道中东太平洋海温关联指数及其与ENSO强弱作用年相关的研究

基于关联度区域平均的方法定义了赤道中东太平洋海表温度的关联指数(TPTI),这一关联指数与多种传统指数具有较多的共性,主要体现了赤道中东太平洋地区海温与其他区域作用强度的变化.同时,指数偏强的年份基本对应了强厄尔尼诺年和拉尼娜年,主要原因在于这些年份温度同步变化的覆盖区域较广,赤道中东太平洋对其他地区的作用较强.因此,厄尔尼诺和拉尼娜事件本身也包含了对全球气候变化的强作用年和弱作用年两种情况.这一关联指数与中国夏季降水联系的研究表明:春季和夏季关联指数与中国夏季降水经验正交分解第一模态的相关系数分别为-0.24和-0.38,前冬和春季关联指数与夏季降水在长江流域和东北地区等均有显著的相关,关联指数大值年和小值年对应的亚欧大陆和北太平洋区域的异常环流形势基本呈反位相配置.因此,这一关联指数具有应用于夏季降水预测的潜在价值,基于网络关联度的指数定义方法可能是气候变化信号指数定义之新的有效途径.     

Modes of variability of global sea surface temperature,free atmosphere temperature and oceanic surface energy flux

Monthly mean sea surface temperature (SST), free air temperature from satellite microwave sounding units (MSU) and oceanic surface energy fluxes are subjected to empirical orthogonal function (EOF) analysis for a common decade to investigate the physical relationships involved. The first seasonal modes of surface solar energy flux and SST show similar inter-hemispheric patterns with an annual cycle. Solar flux appears to control this pattern of SST. The first seasonal mode of MSU is similar with, additionally, land-sea differences; MSU is apparently partly controlled by absorption of solar near-infrared radiation and partly by sensible heat from the land surface. The second and third seasonal eigenvector of SST and solar flux exhibit semi-annual oscillations associated with a pattern of cloudiness in the subtropics accompanying the translation of the Hadley cell rising motion between the hemispheres. The second seasonal mode of MSU is dominated by an El Niño signal. The first nonseasonal EOFs of SST and solar flux exhibit El Niño characteristics with the solar pattern being governed by west-to-east translation of a Walker cell type pattern. The first non-seasonal EOF of MSU shows a tropical strip pattern for the El Niño mode, which is well correlated with the latent heat fluxes in the tropical east Pacific but not in the tropical west Pacific. Two possible explanations are: an increase in subsidence throughout the tropical strip driven by extra evaporation in the tropical east Pacific and consequent additional latent heat liberation; a decrease of meridional heat flux out of the tropics.     

Inertance of surface temperature variations

The index of inertance of surface temperature variations is proposed which supposedly reflects the damping effect of the ocean on the variations in atmospheric thermal conditions over the land. It is demonstrated that the climate variability and climate change are related to the index of inertance. Air temperature rose most intensively in the years of weak stabilizing effect of the ocean which restrains the climate warming. The general trend of the inertance weakening on the land in the second half of the 20th century led to the additional and more rapid warming and to the increase in climate extremity on the continents.     

The prediction of road surface state and simulation of the shading effect

In winter road maintenance, accurate predictions of road surface temperature and state (dry, wet, frost or ice) are valuable for road authorities and organisations to decide where and when to salt or grit roads. Obstructions caused by hills, buildings and trees near road-condition forecast sites both in the daytime and at night (the shading effect) reduce the accuracy of such predictions. This paper describes recent developments in the prediction of road surface state and the simulation of the shading effect, using the Icebreak model, which gives encouraging results.     

Dynamic normals of surface air temperature

Cited are the latest data on the contemporary climate changes in surface air temperature (to the year 2011 inclusive). Substantiated is the necessity of extending the concept on the normals and anomalies of surface air temperature under conditions of the changing climate. Formulated is a concept of “dynamic normals” and “dynamic anomalies” of surface air temperature taking account of current trends of climate change and interseasonal variations. It is proposed to adopt this concept both for the problems of forthcoming climate change assessments and for the long-range forecasting out of the “limit of predictability.” An adaptive regression method is proposed to compute such dynamic normals as a function of the indicator of global climate changes. Presented are the skill scores of dynamic normals as of “intermediate” forecasts (an analogue of the climate forecast under a changing climate).     

Effects of regional temperature,wind speed and soil wetness on spatial structure of surface air temperature

Summary Climate parameters are usually collected on some grid or pattern that is supposed to represent the unobserved neighborhood. Spatial dependence is a measure of the extent to which observed data represent the unobserved neighborhood. Geostatistical analyses provide procedures for measuring spatial dependence. In this study, semivariograms were estimated from hourly observations of screen-height air temperature obtained from a dense meteorological observation network. The range and spatial component normalized by the sill were estimated from the semivariogram in order to obtain information on the spatial structure of the air temperature. Zones of spatial correlation were delineated, using the range of the semivariogram. Scales of spatial correlation depended on the regional mean air temperature and regional wetness at the ground. The range or spatial scale for data collected in winter was larger than those in summer. The range under wet conditions was larger than under dry conditions. Effects of regional wind speed on range were different, depending on the regional mean air temperature. The normalized spatial component was used as an index for measuring continuities on the interpolation surface. The normalized spatial component generally increased as the range increased.With 5 Figures     

大洋间海表温度遥联与中国冬季气温的关系

利用SVD方法,在年代际和年际尺度上研究了各季北大西洋和北太平洋海表温度的遥相关关系,给出了冬季两个时间尺度上的遥联指数I,并分析了它们与同期中国冬季气温及亚太冬季风的相关关系.结果表明:北大西洋和北太平洋在两个时间尺度上的海表温度遥联均与同期中国冬季气温相关;特别在年代际尺度上两大洋海表温度遥联与我国河套以南及长江中游地区冬季气温有显著正相关.其影响途径可能是两大洋海温异常引起亚太冬季风异常、继而引起我国冬季气温异常.     

一种基于空间相关性和B样条曲面拟合的地面气温质量控制算法

将B样条曲面拟合算法引入到地面气温观测资料的质量控制当中,考虑到区域内各参考站与目标站观测值之间的空间相关性,提出了一种基于空间相关性和B样条曲面拟合的地面气温观测资料质量控制算法(Spatial Correlation and B-spline Surface Fitting,BSF)。选择2012—2014年南平站、南京站、太原站、拉萨站、景洪站和长春站以及周围300 km内参考站的02:00、08:00、14:00、20:00定时气温作为观测资料,结合平均绝对误差(Mean Absolute Error,MAE)、均方根误差(Root Mean Square Error,RMSE)、一致性指标(Index of Agreement,IOA)和纳什系数(Nash-sutcliffe Model Efficiency Coefficient,NSC)这4种评价参数对目标站地面气温资料进行质量控制分析。将BSF算法的质量控制效果分别与传统的反距离加权法(Inverse Distance Weighted,IDW)和空间回归检验法(Spatial Regression Test,SRT)进行对比,试验结果表明:在不同案例下,BSF算法的质量控制效果均优于IDW算法和SRT算法,能更有效地标记出气温观测数据中的可疑值。     

Historical effects of temperature and precipitation on California crop yields

For the 1980–2003 period, we analyzed the relationship between crop yield and three climatic variables (minimum temperature, maximum temperature, and precipitation) for 12 major Californian crops: wine grapes, lettuce, almonds, strawberries, table grapes, hay, oranges, cotton, tomatoes, walnuts, avocados, and pistachios. The months and climatic variables of greatest importance to each crop were used to develop regressions relating yield to climatic conditions. For most crops, fairly simple equations using only 2–3 variables explained more than two-thirds of observed yield variance. The types of variables and months identified suggest that relatively poorly understood processes such as crop infection, pollination, and dormancy may be important mechanisms by which climate influences crop yield. Recent climatic trends have had mixed effects on crop yields, with orange and walnut yields aided, avocado yields hurt, and most crops little affected by recent climatic trends. Yield-climate relationships can provide a foundation for forecasting crop production within a year and for projecting the impact of future climate changes.     

Role of sea surface temperature on the equatorial waves and intraseasonal oscillations

Theoretical and Applied Climatology - Ocean interactions are known to play a major role in the modulation of intraseasonal variability. The role of sea surface temperature (SST) and major oceanic...