Thermal bioclimate in Strasbourg - the 2003 heat wave

This case study highlights the implications of the 2003 heat wave for the city of Strasbourg, France. The urban centers of France and other European countries were particularly affected by the heat wave. In some urban areas, the mortality rate was 60% above the expected value (Institute de Veille Sanitaire, 2003). The 2003 heat wave demonstrated once again that populations in urban centers are much more affected by extreme meteorological events than people living in rural areas. The aim of this analysis is to explore differences in thermal comfort conditions of (a) the city center of Strasbourg, and (b) its hinterland. The differences in thermal conditions existing between rural and urban areas are quantified by using a bio-climatological index termed physiologically equivalent temperature (PET). This index is based on the human energy balance and builds a relevant index for the quantification of the thermal environment of humans. We calculate the PET for the years 2003 and 2004 to highlight the temporal changes in the severity of climate extremes. The spatial scope of this study is improved compared to previous works in the field through the inclusion of PET calculations for five different sites on a central place in Strasbourg (Place Kléber). The calculations are characterized by different sky view factors and are compared to the reference site, which is located in a rural area. In the rural hinterland (Entzheim), the analysis of PET indicates a strong cold thermal stress during the winter months but no significant stress in summer. In 2003, summer temperatures were sensed as warmer compared to other years, but did not reach the extreme temperatures that may cause severe heat stress. For both the rural and the urban study sites PET was higher in the summer of 2003 than in 2004, which reflects the inferior thermal conditions in the urban area during the heat wave in 2003. For the entire study period, urban and rural day-time PET reached similar maximal values. Strong differences in PET, however, were observed between the rural and urban areas at night-time. The study of PET for several study sites on a central place in the city (Place Kléber) of Strasbourg for the years 2003 and 2004 showed that the sites with a higher sky view factor present higher values than sites with a lower sky view factor. The comparison of these PET values (Place Kléber) to the results for the rural area showed that during the day and the night the rural city of Entzheim has the lowest PET. During the day, the site at Place Kléber, which is located under a tree, has the lowest PET. The comparison of PET for the years 2003 and 2004 shows that PET in 2003 was about 5 to 7 K higher.     

Modeling of changes in thermal bioclimate: examples based on urban spaces in Freiburg, Germany

The Place of the Old Synagogue is a popular place in the city center of Freiburg, a medium-sized city in southwest Germany. It is going to be redesigned soon. In this paper the impact of urban street design and surface material on human thermal comfort is analyzed using the example of the Place of the Old Synagogue. The models SkyHelios, RayMan, and ENVI-met were applied to quantify and qualify the changes. All three models are freely available. Their combination allows analysis of development in long-term conditions, as well as changes in spatial distribution of thermal comfort, as well as of heat stress in summer. Results show that the models can provide valuable information. About the Place of the Old Synagogue, quantitative results show that the period with heat stress will become longer, while the intensity of heat stress increases. The spatial results show that the most significant changes are due to changes in shading. Nevertheless, an increase in thermal stress up to 10 °C is calculated for areas, where ground coverage changes from grass to pavement.     

Thermal comfort and tourism climate changes in the Qinghai–Tibet Plateau in the last 50 years

In this paper, the thermal comfort and its changes in the Qinghai–Tibet Plateau over the last 50 years have been evaluated by using the physiological equivalent temperature (PET), and a more complete tourism climate picture is presented by the Climate–Tourism–Information Scheme (CTIS). The results show that PET classes in the Qinghai–Tibet Plateau cover six out of the nine-point thermal sensation scale — very cold, cold, cool, slightly cool, neutral and slightly warm — and cold stress is prevailing throughout the year. A small number of slightly cool/warm and neutral days occur in summer months. There occur no warm, hot and very hot days. The frequency of PET classes varies among regions, depending on their altitude/latitude conditions. Xining, Lhasa and Yushu are the top three cities in terms of thermal favorability. With global warming, annual cumulative number of thermally favorable days has been increasing, and that of cold stress has been reducing. The change is more obvious in lower elevation than that in higher elevation regions. The improving thermal comfort in the Qinghai–Tibet Plateau might be a glad tiding for local communities and tourists. Besides PET, CTIS can provide a number of additional bioclimatic information related to tourism and recreational activities. CTIS for Lhasa and Xining shows that sunshine is plentiful all the year round, and windy days occur frequently from late January to early May. This is a useful bioclimatic information for tourism authorities, travel agencies, resorts and tourists.     

长江三角洲地区人体舒适度时空变化特征北大核心CSCD

基于1981~2020年ERA5逐小时再分析资料,采用通用热气候指数(Universal Thermal Climate Index,UTCI)计算方法,分析了气候变化背景下长江三角洲地区人体生理热响时空变化特征。研究表明:近40年长江三角洲地区人体无冷热胁迫气候条件的出现频率约为43.77%、热胁迫和冷胁迫出现频率分别约为22.42%和33.81%,其中,显著热胁迫和显著冷胁迫出现频率分别约为8.38%和1.58%;在空间分布上,长江三角洲地区无冷热胁迫气候条件的出现频率总体表现为南多北少地带性分布,兼有山区多平原少、沿海多内陆少分布特征,显著热胁迫主要出现在皖西和皖南的平原以及浙江的嘉绍平原和金衢盆地,显著冷胁迫主要出现在苏北、皖北和舟山以北的沿海岸区;在全球气候变暖背景下,长江三角洲地区UTCI值的年代际变化呈上升趋势,由1981~1990年13.83℃增加至2011~2020年14.75℃,人体生理热响应表征为冷胁迫减少、热胁迫增加、无冷热胁迫基本不变,春季无冷热胁迫时长的增加基本抵消了夏季无冷热胁迫时长的减少。     

Regional Distribution of Perceived Temperatures Estimated by the Human Heat Budget Model （the Klima-Michel Model） in South Korea

The regional distribution of perceived temperatures (PT) for 28 major weather stations in South Korea during the past 22 years (1983–2004) was investigated by employing a human heat budget model, the Klima-Michel model. The frequencies of a cold stress and a heat load by each region were compared. The sensitivity of PT in terms of the input of synoptic meteorological variables were successfully tested. Seogwipo in Jeju Island appears to be the most comfortable city in Korea. Busan also shows a high frequenc...     

Assessment of thermal bioclimate and tourism climate potential for central Europe—the example of Luxembourg

Tourism destinations often require information about climate to assess their climate potential. This can be performed in terms of mean conditions of relevant climatological parameters. For a user-friendly analysis and visualization of climate data relevant for tourism application in Luxembourg, information is prepared based on the facets of climate in tourism. Information on thermal comfort/stress conditions as well as aesthetical and physical parameters is considered. In the present study, relevant and sensible factors were identified and presented. Therefore, physiologically equivalent temperature, precipitation patterns and the Climate-Tourism/Transfer-Information-Scheme are applied. In addition, extreme events relevant for heat stress are analysed based on existing data sets (i.e. heat waves of 2010). Expected climatic conditions for the future are investigated using the projections of two different regional climate models. The results concerning climate change conditions reveal increasing heat stress and sultriness but decreasing cold stress. This information is the basis for an adequate assessment to provide relevant information for different environmental planning issues as well as for the growing tourism sector of Luxembourg.     

用标准有效温度和不舒适指标研究哈尔滨热舒适状况

为探讨哈尔滨市非采暖期自然热舒适状况,采用标准有效温度这一从人体生理角度得到的热舒适指标来进行研究.考虑到舒适感因人而异,在大多数实际环境条件下,即使对某一个人来说也并非尽善尽美,同时采用热不舒适指标来评价不舒适程度.以哈尔滨市2005年非采暖期(4月下旬至10月中旬)的逐时气温、相对湿度以及风速资料为基础,计算了该市春、秋季非采暖期(4月下旬至5月下旬、9月上旬至10月中旬)逐旬、夏季(6-8月)逐月每3小时的气温、相对湿度、风速平均值.假设夏季人们穿着的服装热阻为0.6clo(典型服装为长裤、短袖衬衫或裤、长袖衬衫),春、秋非采暖期服装热阻为0.9clo(典型服装为长裤,长袖衬衫,夹克衫),当人们活动量为1.0met时(如室内伏案工作),根据计算得到各气象要素平均值,对比热舒适图得到逐旬(月)的每3小时标准有效温度和不舒适指标.对比发现哈尔滨市非采暖期没有能够使80%的人感到满意的时间区域,大致只有5月下旬至9月上旬的10:00-18:00期间,能够达到70%的人感到满意.从4月下旬到5月上旬,平均来看一天中75%的时间感觉很冷,不舒适;而9月下旬至10月上旬,一天中有一半时间感觉很冷,不舒适.由这两个指标所得到的哈尔滨非采暖期热舒适状况比较符合实际,可以采用这两种指标作为人体舒适度研究的参考.     

A comprehensive analysis of physiologically equivalent temperature changes of Iranian selected stations for the last half century

As a preliminary and major step for land use planning of the coming years, the study of variability of the past decades’ climatic conditions with comprehensive indicators is of high importance. Given the fact that one of the affected areas by climatic change includes variability of thermal comfort, this study uses the physiologically equivalent temperature (PET) to identify and evaluate bioclimatic conditions of 40 meteorological stations in Iran. In this study, PET changes for the period of 1960 to 2010 are analyzed, with the use of Mann-Kendall non-parametric test and Pearson parametric method. The study focuses particularly on the diversity in spatio-temporal distribution of Iran’s bioclimatic conditions. The findings show that the mean frequency percentage of days with comfort is 12.9 % according to the total number of selected stations. The maximum and minimum frequency percentage with values of 17.4 and 10.3 belong to Kerman and Chabahar stations, respectively. The findings of long-term trend analysis for the period of 1960–2010 show that 55 % of the stations have significant increasing trend in terms of thermal comfort class based on the Pearson method, while it is 40 % based on Mann-Kendall test. The results indicate that the highest frequency of days with thermal comfort in the southern coasts of Iran relates to the end of autumn and winter, nevertheless, such ideal conditions for the coastal cities of Caspian Sea and even central stations of Iran relate to mid-spring and mid-autumn. Late summer and early autumn along with late spring can be identified as the most ideal times in the west and northwest part of Iran. In addition, the most important inhibiting factors of thermal comfort prove to be different across the regions of Iran. For instance, in the southern coasts, warm to very hot bioclimatic events and in the west and northwest regions, cold to very cold conditions turn out to be the most important inhibiting factors. When considering the variations across the studied period, an increase in the frequency of thermal comfort condition is observed in almost half of the stations. Moreover, based on Pearson and Mann-Kendall methods, the trend of changes in monthly averages of PET has decreased in most stations and months, which can lead to different consequences in each month and station. Thus, it is expected that due to PET changes in recent decades and to the intensified global warming conditions, Iran’s bioclimatic conditions change in a way that transfers the days with comfort to early spring and late autumn.     

基于标准有效温度和不舒适指标研究南京热舒适状况

采用标准有效温度和不舒适指标,分析了南京市热舒适状况。以南京市2010年全年的逐时气温和相对湿度资料为基础,计算了2010年逐月每小时气温和相对湿度平均值。通过假定在均匀的环境条件下,遮阴的室内,伏案工作活动量为1.0 met,夏季服装热阻为0.6 clo,春、秋、冬季服装热阻为0.9 clo,室内风速约为0.125 m/s,计算出各月逐时标准有效温度和不舒适指标。结果表明,南京市的热舒适状况具有明显的季节变化和日变化特征。季节变化特征显示：夏冬两季热舒适度偏低,夏季平均标准有效温度和不舒适指标分别为27.6℃和0.7,人体感觉偏热;冬季平均标准有效温度和不舒适指标分别为9.4℃和-2.8,人体感觉偏冷;春秋两季热舒适度指数高,春季平均标准有效温度和不舒适指标分别为19.7℃和-0.8,秋季为17.2℃和-1.3,人体普遍感觉舒适,但舒适期持续时间短,全年约62天。就日变化特征而言,冬季白天人体热舒适度普遍高于夜间,夏季则相反。上述结果能够较好地反映南京市人体的普遍热舒适感,可为旅游、建筑、医疗、交通等相关行业和部门提供参考。     

丽水市生态气候休闲养生适宜性分析

人们的休闲养生活动与气候条件和生态环境密切关联。选取反映气候综合状况的4项气候指数和表征生态环境质量的5项生态指标,对丽水市生态气候的休闲养生适宜性进行了分析。分析结果表明:丽水气候全年有8个月的人体舒适度气象指数BCMI等级达到"舒适"和"较舒适"级别,其中"舒适"级别有4个月;有11个月的气候适宜旅游度假(度假气候指数HCI60),其中"很适宜"级别月份有5个,"特别适宜"级别月份有1个;丽水冬季气候风寒指数WCI值在550 kcal/m~2·h以下,极少出现严寒天气,气候仅会对人体产生弱度冷胁迫;夏季丽水气候温湿度相对较高,尤其是7月温湿指数THI值可达80以上,城市区域的温湿胁迫较为强烈。丽水市生态环境优质,森林覆盖率为80.8%、物种丰度指数达0.96、断面水质达标率为98.9%、优良空气天数达360天,并拥有14个国家4A级旅游景区。国内21座城市生态气候数据的对比分析显示,丽水市气候指标占优、生态指标领先,其休闲养生适宜性在国内城市中具有突出优势。     

Urban heat island and differences in outdoor comfort levels in Glasgow, UK

From extensive outdoor comfort campaigns, preliminary outdoor comfort ranges have been defined for the local population of Glasgow, UK, in terms of two thermal indices: ‘Temperature Humidity Sun Wind’ (THSW) and ‘Physiological Equivalent Temperature’ (PET). A series of measurements and surveys was carried out from winter through summer 2011 during 19 monitoring campaigns. For data collection, a Davis Vantage Pro2 weather station was used, which was equipped with temperature and humidity sensors, cup anemometer with wind vane, silicon pyranometer and globe thermometer. From concurrent measurements using two weather stations, one located close to the city core and another located at a rural setting, approximately at a 15-km distance from the urban area of Glasgow, comparisons were made with regard to thermal comfort levels and to urban–rural temperature differences for different periods of the year. It was found that the two selected thermal indices (THSW and PET) closely correlate to the actual thermal sensation of respondents. Moreover, results show that the urban site will have fewer days of cold discomfort, more days of ‘neutral’ thermal sensation and slightly higher warm discomfort. The most frequent urban heat island intensity was found to be around 3° C, whereas the fraction of cooling to heating degree-hours for a T _base of 65 °F was approximately 1/12th.     

基于ENVI-met的福州大学校区冬季热环境模拟与热舒适度变化分析

选取福州大学校园教学区为研究区域,基于典型冬季日背景,运用三维非静力微气候模型ENVI-met,分析模拟校园热环境的差异变化及其热舒适度响应。结合实地勘测,对模型进行校准和验证。结果表明：ENVI-met模型能较好地表征室外热环境,准确预测温度和相对湿度的日变化趋势。混凝土路面、灰色地砖路面行人高度的日平均气温分别比草地高出0.1 ℃和0.3 ℃,逐时最大温差分别为0.68 ℃和0.65 ℃。建筑物阴影和树阴可降低行人高度的气温1.1—1.9 ℃;同一组团在有无遮阴的条件下,平均辐射温度（T_mrt）相差最大可达30 ℃;树木附近和建筑物组团内部生理等效温度（PET）值较小,比硬质路面低2—3个等级。无植被方案下,高温低湿区范围有所扩张,在垂直方向上的增温效应可伸展至10.5 m;风速最大增幅可达1.23 m·s^-1,平均辐射温度较高区域的面积增加了69.25%;热舒适区和热不适区面积分别增加了19.78%和2.03%。     

Observations of industrial fog,cloud and precipitation on very cold days

Abstract

Fog, cloud, and precipitation caused by the petrochemical plants in Edmonton, Canada, were studied on some of the coldest days of four winters. Typical morning temperatures were between –15 and –40° C. The investigation includes a comprehensive heat and vapour emission inventory, field studies of the local cloud physics, and observations of plume cloud dispersal and precipitation formation. Five field trips are discussed in detail.

The emission inventory indicated that the petrochemical plants released heat and vapour at a rate comparable to that of the city of a half million people. Thermal circulations in the industrial area were substantial but they were not strong enough to prevent some restriction of visibility when temperatures fell below –25° C, and an area‐wide restriction of visibility as deep ice fog set in at temperatures below –35°C. Widespread cloudiness caused by plant plumes was found to be caused by the combined influence of low temperatures and low wind speeds. Snowfall rates were generally very light but when meteorological conditions were right, the snowfall reduced visibility locally to 100 m and made roadways slippery.     

Variability of meteorological elements shaping biometeorological conditions in Szczecin, Poland

In this study, the time and spatial variability of perceptible conditions, determined on the basis of effective temperature in the area of the Szczecin agglomeration are presented. The study was based on air temperature, relative humidity and wind speed data acquired during 2005?C2007 from three emissions stations located in the centre and on the outskirts of the city of Szczecin, Poland. The differences in the values of the measured meteorological components between the studied city locations, in terms of their magnitude and daily structure, were analysed by month and calendar season. The results demonstrate that the temperatures in the city centre were considerably higher throughout the daily cycle, which was most evident during the summer in contrast to winter when the differences were the lowest. Mainly June and July, at 17?C24 UTC (Coordinated Universal Time), were characterized by the average highest intensity of the urban heat island. Reduced relative humidity in the centre of Szczecin, as compared to the suburban areas, was observed particularly during summer. Throughout the daily cycle, this trend was also observed during spring, primarily during the night. Wind speed within the congested housing in the centre of Szczecin was over two-fold lower as compared to the unbuilt-up areas of the outskirts, irrespective of the time of the day and season of the year. Modification of the air humidity, thermal and anemometric conditions was reflected in a considerable variation in heat perception. In summer and spring, between 1300 and 2100 UTC, the most burdening biometeorological conditions, sensed as ??hot?? and ??very hot?? weather, prevailed in the city centre. During winter, on the other hand, the unbuilt-up areas on the city outskirts were the most unfavourable in terms of biothermal conditions, with the predominant categories of perceptible weather conditions throughout the daily cycle being ??cold?? and ??very cold??.     

1966—2018年秦皇岛气候舒适度时空变化特征

利用1966—2018年气象资料,采用气候舒适度评价及趋势分析方法,对秦皇岛地区近53 a气候舒适度变化进行分析。结果表明：秦皇岛北部山区、中部平原和东南沿海三个区域的气候舒适度变化趋势一致,存在空间差异性。整体上,秦皇岛气候舒适度以舒适至冷凉特征为主,各区域舒适和较舒适等级占47%—49%,冷不舒适等级占34%—37%,炎热及更热不舒适等级极少。近53 a,夏季、冬季气候舒适度均呈增暖趋势,冬季增暖幅度大于夏季。热不舒适日数自20世纪90年代开始激增且持续偏多,寒冷不舒适日数呈逐年代减少态势;在空间上,热不舒适日数随着测站高程和纬度的降低而增多,寒冷不舒适日数与之相反。5—10月气候舒适或较舒适,秦皇岛全域皆为旅游、疗养适宜期;7—8月无酷暑,“微热”的天气为人们提供畅游大海的有利气象条件;3月、4月和11月气候偏冷凉,是户外登山的大好时机;12月至翌年2月寒冷不舒适,不适宜大众旅游疗养,适宜开展冰雪旅游活动。因此,可以认为秦皇岛全域、全季皆适宜旅游,由此为秦皇岛市旅游开发与规划及研究气候变化对旅游业的影响提供依据,为来到“秦皇山海、康养福地”的康养群体提供生活和出游气象服务指导。     

2011年深圳人体舒适度空间分布特征及影响因子分析

利用深圳多个区域自动气象站资料,采用考虑了气温、风速、相对湿度等要素的人体舒适度计算方案,计算了深圳地区的人体舒适度指数以及不同舒适等级天数,分析了城市地形地貌、路网密度和人口密度等因素对人体舒适度的影响。结果表明：深圳地区沿海比内陆舒适,全市全年舒适天数为7-9个月,夏季感觉热的天数约为2-3个月,冬季感觉冷的天数大部分地区为30 d左右。从不同地区人体舒适度指数的日变化特征来看,夏季比冬季更易受地理位置和下垫面等因素影响。地形地貌、海陆分布、城市规划等地理因素对人体舒适度均有一定影响,相关分析表明海拔高度、道路占地面积和人口密度与热-炎热日数呈对数关系。但在深圳的东部人口稀疏和道路占地较小地区也并非舒适宜人,也会出现较多炎热天气,这与该地区年平均风速相对微弱有直接关系。     

以热量平衡为基础的体感温度模型及气候要素的效应分析

通过对丰季人体热量平衡方程的建立与计算，结合我国不同年龄段人群的新陈谢特点，分别建立了不同的体感温度模型，经与我国目前应用较为广泛的人体舒适度统计模型的计算结果相比较，证明以热量平衡为基础的人体感温度模型更具有普遍性。还分析了风，湿度，辐射对体感温度的影响效应。这些结果将为拓宽舒适度服务范围，建立以人体舒适度为核心的城市气象服务体系提供理论依据。     

Modelling of cloud formation due to air-sea interactions in an energy-active zone

A mesoscale 3D numerical model is described, with which detailed calculations have been made of turbulence and wind characteristics in the atmospheric boundary layer (ABL), as well as cloud particle size distribution, longwave and solar radiation fluxes and flux divergences, and atmosphere-ocean heat exchange. Based on numerical experiments simulating winter conditions of the Newfoundland energy-active zone of the ocean (EAZO), atmosphere-ocean energy exchange is investigated. It is shown that the basic mechanisms for the EAZO formation involve the following processes: (i) at the hydrological front between cold and warm ocean currents, the fluxes of sensible and latent heat grow significantly; (ii) at this front, in a particular synoptic situation, overcast low-level cloudiness forms, screening solar radiation so that in winter, the radiation budget at the front is reduced, and the radiative flux into the ocean is less than the energy release to the atmosphere; (iii) frequent occurrence of such synoptic situations with cloudiness decreases the oceanic enthalpy and creates negative SST anomalies. The transport of these anomalies by currents to the western coasts of the continents causes anomalies of weather and climate.     

Cloud climate investigations in the Nordic region using NOAA AVHRR data

Summary A method to estimate monthly cloud conditions (monthly cloud frequencies) from multispectral satellite imagery is described. The operational cloud classification scheme SCANDIA (the SMHI Cloud ANalysis model using DIgital AVHRR data), based on high resolution imagery from the polar orbiting NOAA-satellites, has been used to produce monthly cloud frequencies for the entire year of 1993 and some additional months in 1991, 1992, 1994 and 1995. Cloud analyses were made for an area covering the Nordic countries with a horizontal resolution of four km. Examples of seasonal, monthly and diurnal variation in cloud conditions are given and an annual mean for 1993 is presented.Comparisons with existing surface observations showed very good agreement for horizontal cloud distributions but approximately 5% smaller cloud amounts were found in the satellite estimations. The most evident problems were encountered in the winter season due to difficulties in identifying low-level cloudiness at very low sun elevations. The underestimation in the summer season was partly fictious and caused by the overestimation of convective cloud cover by surface observers.SCANDIA results were compared to ISCCP (International Satellite Cloud Climatology Project) cloud climatologies for two selected months in 1991 and 1992. ISCCP cloudiness was indicated to be higher, especially during the month with anticyclonic conditions where a cloudiness excess of more than 10% were found. The regional variation of cloud conditions in the area was found to be inadequately described by ISCCP cloud climatologies. An improvement of the horizontal resolution of ISCCP data seems necessary to enable use for regional applications.The SCANDIA model is proposed as a valuable tool for local and regional monitoring of the cloud climatology at high latitudes. More extensive comparisons with ISCCP cloud climatologies are suggested as well as comparisons with modelled cloudiness from atmospheric general circulation models and climate models. Special studies of cloud conditions in the Polar areas are also proposed.With 14 Figures     

Potential climatic effects of cirrus contrails for the subarctic setting of Fairbanks, Alaska

Summary Continuous all-sky camera images supported by direct visual observations of jet contrails have been carried out in Fairbanks since March 2000. These data together with FAA information of all commercial flights and the twice-daily radiosonde data, give the meteorological conditions at flight level under which contrails are formed. If we correct for daylight and clear sky conditions, which make contrail observations possible, winter has the maximum and summer the minimum in the occurrence of contrails. This is a result to be expected, as the layer in which contrails can form has in winter nearly twice the thickness when compared to summer.In November 2002, a radiation station was added to the observations. For a contrail in the path between the sun and the observation point, we found a strong decrease in the direct beam radiation; this loss was in part compensated by increased diffuse radiation. The combined effect leads to a reduction in global radiation. However, the back radiation of the atmosphere in the infrared region of the spectrum increased somewhat. Altogether, this affects the net radiation negatively in the summer, but positively in the winter.Comparing the observed temperature conditions of clear days with those of high-level cloud cover, we found for 8 months of the year a higher temperature for days with clouds. For the other four months, May through August, clear days were warmer. On the average of the year, days with high-level cloudiness were warmer than clear days as well as days with low-level overcast.High-level cloudiness has increased in Alaska over the last decades. This increase in cloudiness was more pronounced under the much-traveled flight corridor from Anchorage to Europe than for more remote areas of Alaska. Further, we found a temperature increase for the same time period, which was most pronounced in winter, followed by spring, a result consistent of the expectations of increased high-level cloudiness.