Summer Air Temperature Research Articles

ИСПОЛЬЗОВАНИЕ ДАННЫХ РЕАНАЛИЗА ДЛЯ ИССЛЕДОВАНИЯ ЛЕДЯНОГО ПОКРОВА АЗОВСКОГО МОРЯ

The article presents an analysis of the results of the OSI-450 reanalysis as an alternative data source for the study of the ice cover of the Azov Sea. OSI-450 is the second major version of the OSI SAF Global Sea Ice Concentration Climate Data Record (CDR). The OSI-450 product is available for the period 1979 to 2015.Using licensed software ArcGIS 10.*, a model for data processing was created. The average long-term value of the ice cover for the period 2000–2015 according to the OSI-450 reanalysis data is 23.3 %, according to GIS data – 37.2 %; the maximum and minimum values are 43 % / 69.4 % and 8.2 % / 8 %, respectively. The correlation coefficient with the sum of average monthly air temperatures is minus 0.87 (air temperature for the winter season is a main factor that determines the ice conditions of the Sea of Azov). It is shown that the OSI-450 reanalysis data underestimate the ice extent for the season, but on the whole reproduces the long-term dynamics of the ice cover for the period under consideration. Based on the study, it was concluded that the OSI-450 reanalysis can act as an alternative source of data on the state of the ice cover, but taking into account correction factors.

夏期炎天下駐車時における車室内温度低減（吹出し方向の検討による運転席周りの温度低減）

In a car under summer solar radiation, the surface and air temperatures become very high, for example the air temperature around driver's seat was over 65 degree C. Thus, a ventilation system is one of the important methods for keeping comfortable thermal environment. In this study, in order to clarify the effect of temperature reduction around driver's seat, the experiment of measuring temperature and the numerical simulation under changing the blowing direction to driver's seat backrest in a car cabin were conducted. In case of flow rate of 100m3/h, it was found that the effects of temperature reduction on the driver's seat and around the driver's seat with FACE-C mode ventilation were remarkable compared with FACE mode ventilation.

Modeling past and future variation of glaciers in the Dongkemadi Ice Field on central Tibetan Plateau from 1989 to 2050

ABSTRACT Glacier mass balance change is among the best indicators of glacier response to climate change. Due to its inaccessibility and limited observation, little is known about the change to the Dongkemadi Ice Field (DIF) in the Tanggula Mountains located in the source region of the Yangtze River in central Tibetan Plateau. Here, an enhanced temperature index–based glacier model considering glacier area change was applied to study the temporal–spatial variation in mass balance on the DIF from 1989 to 2012 and to assess its response to climate change. The model was forced by reconstructed temperature and precipitation from adjacent national meteorological stations and validated by comparing with field observations from the Xiao Dongkemadi Glacier (XDG). Results show that the simulated mass balance is in good agreement with the observations (R 2 = 0.75, p < .001), and the model can reasonably reproduce well the glacier mass change. Then the model was applied to twenty individual glaciers in DIF and forced by the high-resolution regional climate model (RegCM3) from 2013 to 2050 to project their further variation. In the future, the mass balance of glaciers in DIF shows a continuously negative trend with a linear rate of −0.16 m water equivalent (w.e.) a−1 in representative concentration pathway (RCP) 4.5 and −0.35 m w.e. a−1 in RCP 8.5. Most of the glaciers’ equilibrium line altitudes (ELAs) will reach or exceed their maximum elevation after the 2030s. By coupling a modified volume–area scaling method with the mass balance model, results showed that areas of the individual glaciers in DIF will lose about 12.10 to 30.66 percent under RCP4.5 and 14.06 to 38.76 percent under RCP8.5, and the volume of the DIF will lose about 1.18 km3 in RCP4.5 and 1.44 km3 in RCP8.5 by the end of 2050. In addition, the terminuses of glaciers experienced the largest percentage losses and most of the glaciers’ front position will reach ~5,520 m a.s.l. in RCP 4.5 and 5,570 m a.s.l. in RCP 8.5, the latter of which is nearly close to the DIF average ELA in 1989. The clearly increasing summer air temperature may be the main reason for glacier shrinkage in the DIF. If the warming trend continues, glaciers in DIF may further retreat with continued glacial melt or even mostly disappear by the end of the century.

ГОРНЫЕ ЛЕДНИКИ СЕВЕРА РОССИИ: ИЗМЕНЕНИЯ ЗА ПОСЛЕДНИЕ ДЕСЯТИЛЕТИЯ ПОД ВОЗДЕЙСТВИЕМ ВАРИАЦИЙ КЛИМАТА

The purpose of the paper is to review the changes in the mountain glaciers of the Russia North, in its continental part under changing climate, the reaction of glaciers onto fluctuations, primarily air temperature and precipitation over recent decades. The review covers the reaction of climatic systems of the Russian North (Russian Subarctic and North of Baikal region) to climate changes of the late 20th century and the last decades of the 21st century. These are systems located in mountainous countries: the Polar and Subpolar Urals, Byrranga, the Putorana Plateau, the Orulgan, Suntar-Khayata, Chersky ranges, and the highlands of Chukotka, Kolyma and Koryakia. Judging by the obtained trend maps of the main climatic characteristics important for glaciation, the temperature increase from S to N in 1966- 2019 and a decrease in precipitation in approximately this direction contribute to a reduction in the area and mass of glaciers in Russian North. Methods for assessing the size of glaciation and their dynamics were based on a comparison of data from the Catalog of Glaciers of the USSR and later catalog issues (these are the Chukotka and Kolyma glacial systems) with the results of decoding satellite images (Landsat, ASTER, Sentinel-2) and expeditionary information. Most of the studied glacial systems are represented by small forms of glaciation, which are defined. Since estimates of glacier reduction are given for different systems for different periods of time, it was not the task of the review to compile an accurate single picture. The glacier reaction of varying size, morphological type, bedding, aspect is not the same even for approximately similar climate conditions. For each region, variations in mean summer air temperature and cold season precipitation of key (nearest) weather stations for the period from the onset of a positive trend in summer temperatures are given. Under conditions of prolonged climate change towards warming, the climate factor has become the most importrant, which is confirmed by the data presented in this work.

Causes of Daphnia midsummer decline in two deep meromictic subalpine lakes

Abstract Daphnia are key organisms in pelagic food webs, acting as a food resource for fish and predatory zooplankton and regulating phytoplankton through grazing. Its population dynamic follows regular seasonal patterns, with spring peaks followed by summer population declines (midsummer declines, MSDs). Midsummer declines show high inter‐annual variation, which has been attributed to different causes. However, the mechanisms controlling the MSD remain poorly understood, especially in deep stratified lakes. We tried to disentangle the factors causing Daphnia MSDs in Lake Lugano and Lake Iseo (in Switzerland and Italy), two deep peri‐alpine lakes with similar trophic status and vertical mixing dynamics, characterised by phosphorus accumulation in the hypolimnion and variable mixing during late‐winter turnovers. Specifically, we assessed the effects of three different hypothetical pathways according to which: (1) winter air temperature controls MSDs by influencing mixing depth during turnovers and epilimnetic phosphorus replenishment; (2) vernal air temperature influences MSD by accelerating the timing of spring population peak; and (3) summer temperature influences MSDs by increasing fish predation. We assessed the relative strength of these pathways using structural equation modelling on long‐term datasets for the two lakes (29 years for Lake Lugano and 19 years for Lake Iseo). Between the hypothesised pathways, the one driven by winter air temperature (through P replenishment) influenced Daphnia abundance in spring in both lakes, but the effects propagated to summer Daphnia abundance only in Lake Lugano. Additionally, summer Daphnia abundance was influenced by the summer air temperature through a positive (although weak) effect. By comparison, vernal air temperature had no detectable effects on summer Daphnia abundance. The results revealed marked differences between the meromictic study lakes and the shallow hypertrophic water bodies that were the focus of previous research on Daphnia MSD, and also between the two study lakes. The influence of epilimnetic P replenishment on the summer Daphnia abundance in Lake Lugano, which was recovering from past eutrophication, may have reflected the greater susceptibility of deep, stratified lakes to P depletion after spring compared to shallow hypertrophic lakes or reservoirs. This effect might not have been detected in Lake Iseo because P was more consistently depleted during the study period (i.e. variance in the predictor was too low to detect an effect). This study highlighted the complexity of the effects of climate variability on Daphnia MSD in deep lakes, showing that the responses can differ even between two neighbouring lakes with similar vertical mixing dynamics and trophic status. At the same time, the results suggest that future increases in winter air temperature, caused by global warming, may cause critically low densities of Daphnia during spring and summer and compromise the ability of zooplankton to control phytoplankton biomass.

SEASONAL AND SPATIAL VARIATION OF PM10 IN AN URBAN AREA FROM ROMANIA

The cyclic variance of PM10 mass concentration in the urban area in the South-East of Romania has been analysed in the article. SE of Romania is considered to be a territory which has medium level of pollution for a period of last ten years, from 2009 to 2018. The spatial dispersion of PM10 concentration was obtained using the METI-LIS soft wear for each season. The objective of dispersion models is to evaluate how pollutant concentration is spread out taking into account the diffusion. The average measurements of PM10 and meteorological parameters as inputs has been used. An evident seasonal change of PM10 concentrations is observed in the article. In order to establish national measures for the improvement of the atmospheric pollution control it was analysed the mechanism of atmospheric pollution. It was observed that the air quality was overall better in spring and in summer in comparison to the other two periods. With regard to the seasonal variation characteristics of PM10 significant differences for the air quality registered in different months in the researched region were observed. The impact of air temperature on atmospheric pollution was insignificant in spring and autumn; moreover, precipitation was defined as an important influence factor upon the atmospheric pollution. The impact of precipitation on the possibility of atmospheric pollution was obviously different in the four seasons. The research results indicate the meteorological parameters that influence the air pollution become active during the cold seasonal days. It was shown that relative humidity and wind speed are the meteorological parameters that impact the PM10. It was found out that the probability of atmospheric pollution decreased with the increase of air temperature in summer. The research results also testify that the air pollution mapping could be enhanced using atmospheric dispersion models and in-situ measurements.

Estimation of Summer Air Temperature over China Using Himawari-8 AHI and Numerical Weather Prediction Data

This study proposed an instantaneous summer air temperature (Tair) estimation model using the Himawari-8 Advanced Himawari Imager (AHI) brightness temperatures (BTs) in split-window channels and other auxiliary data. Correlation analysis and stepwise linear regression were used to select the predictors for Tair estimation. Nine predictors such as AHI BTs in channels 14 and 15, elevation, precipitable water vapor (PWV), and relative humidity (RH) were finally selected. Stepwise linear regression and neural network (NN) methods were applied to construct summer Tair estimation models over China, respectively. The estimated Tair by linear and NN models was evaluated using the observed Tair from 272 meteorological stations over China. The results showed that AHI BTs in channels 14 and 15, elevation, PWV, and RH were more important for Tair estimation than other predictors. The accuracy of the NN models was better than the linear models. The correlation coefficient (R), root mean square error (RMSE), and bias were 0.97, 1.72°C, and 0.04°C, respectively, for the NN model and were 0.89, 3.28°C, and 0.07°C, respectively, for the linear model. About 75.6% of the Tair differences by the NN model were within 2.0°C, and even 45.8% were within 1.0°C. The performance of the Tair estimation model for each site was also investigated, and the accuracy of Tair estimation in southeast China is better than northwest China.

Temporal Changes in China’s Air Temperature Distribution and Its Impact on Hot Extreme Occurrence

The likelihood of experiencing hot extremes has drastically increased due to global warming. Using 554 ground-based air temperature stations, changes in the number of hot days (NHD) in the Chinese mainland during 1960 to 2011 was investigated. We found that the NHD of the current period (1991–2011) was 70% higher than that of the base period (1960–1990). This NHD increment was attributed to the increased summer air temperature mean and its extended hot tail length—defined as the range of the mean and 90th percentile of summer air temperature. To distinguish the relative contribution of air temperature mean and hot tail length change to the NHD occurrence, a numerical-based frame work was proposed. Results showed that global warming (mean temperature increase) contributes approximately 75% of the total NHD increment. Although the average contribution of the hot tail length change is relatively small, it dominates the NHD change in regions where global warming is insignificant, e.g., the central part of China. Results suggest that frameworks and models that fail to capture the air temperature tail changes will result in biased low hot extreme occurrence estimations. This low bias would be particularly significant in regions where the mean temperature change is marginal. Hence, capturing the tail change should be the key model evaluation criterion in regions where the annual mean temperature change is relatively insignificant.

Impact of Heat Resources on Rice Productivity in the Sarpinsky Lowland

The possibility of rice cultivation in the northern areas of rice sowing is determined by the sum of effective air temperatures (Σt ≥ 15 ∘C) over the growing season and its distribution over the vegetation phases of the plants. A long-term statistical and correlation analysis of rice productivity depending on the thermal resources of the Sarpinsky lowland at the Maliye Derbeta meteorological station for the period from 1964 to 2018 (correlation coefficient r = 0.68) is given. It is established that the sum of effective air temperatures varies from 3140.2 to 3999.7 ∘C, while the average annual value is 2820 ∘C. The highest yield (more than 5 t/ha) of rice grains is formed in years with the sum of effective temperatures over 3000 ∘C. The fluctuations of air temperature and their influence on the production process, and the yield of rice grains are analyzed, the results of which can be used as source data in modeling climate change scenarios and predicting rice grain production. The optimal amounts of effective air temperatures for the period April-September, ensuring the realization of the potential productivity of rice in the Sarpinsky lowland conditions, are determined.

Winter damage is more important than summer temperature for maintaining the krummholz growth form above alpine treeline

Abstract Understanding the processes that control alpine treelines, the elevational limits of tree growth forms, has been a central question in ecology and is growing in importance with concern over climate change. Cool summer air temperatures are currently thought to be the ultimate limiter of upright tree growth at alpine treelines globally. However, winter damage has long been recognized as a shaping force near alpine treelines. Low‐growing krummholz growth forms provide an opportunity to test hypotheses about the controls of upright growth in environments above current treelines. To distinguish between effects of growing season temperature, winter damage and their interaction on preventing upright growth in krummholz, we conducted a field experiment on krummholz growth forms of Pinus albicaulis over the summer and winter of 2015–2016 at 10 mountain top sites in the Tobacco Root Mountains, Montana, USA. We experimentally manipulated four factors using a fully crossed design: shoot position (natural low position in the krummholz mat vs. propped up above the krummholz mat), summer warming (warming chamber vs. ambient), winter exposure (shelter cage vs. exposed), and elevation position (local high vs. low krummholz limits). We also conducted an observational study of the climatic conditions associated with recent natural emergent stem establishment from krummholz. Experimentally propped shoots that were exposed in winter experienced the highest mortality (10%–50%), while propped shoots in shelter cages and shoots located within the krummholz mat, whether caged or not, had low mortality (0%–10%). Summer warming had little influence on shoot mortality. Surviving mat shoots had marginally higher growth rates than surviving propped shoots during the early growing season after treatments were established. Natural emergent stem establishment was associated with warmer than average summer temperatures, but also warmer winter temperatures, lower winter wind speeds, and lower snowpack. Synthesis. Our results suggest winter damage plays a more important role than does growing season temperature in maintaining the krummholz growth form. While warming may increase opportunities for emergent shoot establishment above krummholz mats, establishment of upright trees in the krummholz zone will also require climatic change that reduces wind and snow transport which cause winter damage.

Climate Compensation and Indoor Temperature Optimal Measuring Point Energy Saving Control in VAV Air-Conditioning System

Temperature measuring point is the key to room environment control. Temperature measuring points and climate changes are directly related to the room control effect. It is of great theoretical and practical significance to study the temperature measuring points and control strategy based on climate compensation. In this study, first, the climate compensation concept in a heating system was introduced into a variable air volume (VAV) air-conditioning system. The heating load was modeled as a function of supply air temperature by analyzing the heat exchange. Based on each control link of subsystems, a climate compensation scheme is proposed to determine the optimal set-point of the supply air temperature. At the same time, a layout of multiple temperature measuring points of an air-conditioned room was studied. Furthermore, the optimal indoor temperature measuring point was determined using an adaptive weighted fusion method. Finally, simulation results show that the proposed method has better control effects on indoor temperature adjustment compared with the traditional method. The optimal supply air temperature in summer and winter was determined according to the proposed climate compensation scheme, and the supply air temperature was controlled using an improved single-neuron adaptive control strategy. Experimental results show that the maximum energy saving can reach up to 35.5% in winter and 6.1% in summer.

Temperature regime of Fibrist Histosols of the Bakchar Mire (West Siberia)

Temperature regime of Fibrist Histosols of the Bakchar Mire (West Siberia)

Thermal properties of active layer in permafrost regions with different vegetation types on the Qinghai-Tibetan Plateau

Active layer plays a key role in regulating the dynamics of hydrothermal processes and ecosystems that are sensitive to the changing climate in permafrost regions. However, little is known about the hydrothermal dynamics during freeze-thaw processes in permafrost regions with different vegetation types on the Qinghai-Tibetan Plateau (QTP). In the present study, the freezing and thawing processes at four sites (QT01, 03, 04, and 05) with different vegetation types on the QTP was analyzed. The results indicated that the impact on the soil water and heat during the summer thawing process was markedly greater than that during the autumn freezing process. Furthermore, the thermal-orbit regression slopes for all sites exhibited a homologous variation as the depth increased, with the slowest attenuation for the meadow sites (QT01 and QT03) and a slightly faster attenuation for the desert steppe site (QT05). The air and ground surface temperatures were similar in winter, but the ground surface temperature was significantly higher than the air temperature in summer in the radiation-rich environment at all sites on the QTP. The results also indicated that the n-factors were between 0.36 and 0.55 during the thawing season, and the annual mean temperature near the permafrost table was between − 1.26 and − 1.84 °C. In the alpine desert steppe region, the thermal conditions exhibited to show a warming trend, with a current permafrost table temperature of − 0.22 °C. The annual changing amplitude of the ground temperature at the permafrost table was different for different vegetation types.

Modeling present and future ice covers in two Antarctic lakes

AbstractAntarctic lakes with perennial ice covers provide the opportunity to investigate in-lake processes without direct atmospheric interaction, and to study their ice-cover sensitivity to climate conditions. In this study, a numerical model – driven by radiative, atmospheric and turbulent heat fluxes from the water body beneath the ice cover – was implemented to investigate the impact of climate change on the ice covers from two Antarctic lakes: west lobe of Lake Bonney (WLB) and Crooked Lake. Model results agreed well with measured ice thicknesses of both lakes (WLB – RMSE= 0.11 m over 16 years of data; Crooked Lake – RMSE= 0.07 m over 1 year of data), and had acceptable results with measured ablation data at WLB (RMSE= 0.28 m over 6 years). The differences between measured and modeled ablation occurred because the model does not consider interannual variability of the ice optical properties and seasonal changes of the lake's thermal structure. Results indicate that projected summer air temperatures will increase the ice-cover annual melting in WLB by 2050, but that the ice cover will remain perennial through the end of this century. Contrarily, at Crooked Lake the ice cover becomes ephemeral most likely due to the increase in air temperatures.

The impact of courtyard geometry on its mean radiant temperature

For hot regions, studies have been advocating re-adopting the courtyard pattern for its thermal advantages. Aiming at developing thermally comfortable courtyards, studies have been exploring the impact of courtyards geometry on their shading and natural ventilation, which are the two environmental principles of courtyards. However, there is a lack of studies on the impact of manipulating courtyards geometry on the thermal sensation of occupants. This research investigates the impact of changing the courtyard geometry and the resulted shading on Mean Radiant Temperature (MRT) and Globe temperature (Tg). The latter represents the thermal perception of occupants and the former is the main effective factor on the thermal sensation of people in outdoor and semi-outdoor spaces. The research carried out simulation experiments to test 360 different courtyard configurations. The simulation experiments included using Envi-met and IES-VE simulation tools. The former was used to determine MRT and Tg, and the latter to determine shading levels. Baghdad was selected to represent an example of a hot city in which summer air temperature reaches around 50 °C. The results show that the difference in shading that results from changing the courtyard geometry can lead to a difference in MRT and Tg of up to 15°C.

REPRODUCTIVE POTENTIAL OF POTATO ACCESSIONS FROM THE VIR COLLECTION IN MURMANSK PROVINCE

Background. Knowledge of the reproductive potential in plants is of vital importance for potato cultivation in the Arctic environments.Materials and methods. From 2008 through 2017, 1594 potato cultivars with diverse maturation schedules from VIR’s collection were studied at the Polar Experiment Station of VIR. The material was evaluated according to the timing of their phenological phases (germination, budding, and flowering) and the possibility of their reproductive organs’ development.Results: With the same agricultural practice applied, cultivars of different maturation groups began to germinate and produce shoots at about the same time within the growing season, with a slight difference from 0.2 days (2010) to 3.3 days (2015). Further passing of phenological phases under the conditions of the Arctic depended on the mean daily air temperature and precipitation. The duration of the period from germination to flowering was largely affected by the temperature regime. The emergence of mass shoots was observed on average 18.5 ± 2.9 days after planting. The budding phase started 31.9 ± 4.7 to 43.0 ± 6.9 days after planting. The beginning of flowering occurred at the beginning of the third decade of July or 46.8 ± 4.9 to 57.5 ± 7.5 days after planting. The duration of the mass flowering of potato plants on average covered the time frame from the end of July to the middle of the third ten-day period of August. To move a potato plant from the budding phase to the flowering/mass flowering phase, a sum of effective July temperatures of 300°C is required. During the growing season, for all the years of the study, 97% of the varieties, as related to the total number of accessions, were able to set up buds; 85.7% entered the flowering stage; 63.3% moved to the stage of mass flowering; and 22.2% were able to set berries from self-pollination. According to the data of the long-term analysis of perennial agrometeorological data, the most favorable conditions for setting berries after potato self-pollination recurred every five years in the north. These conditions were formed under the sum of active air temperatures from 1170 to 1300°С (for June, July, and August), combined with insufficient provision of precipitation. Under the natural conditions in the north, the lack of moisture stimulates plants to enter the stages of flowering and fruit setting quicker and more intensively.Conclusion: The study made it possible to identify the optimal conditions for the fruit to be set by a potato plant in the north and also to acquire more data on the reproduction characteristics of potato cultivars.

Numerical study and in-situ measurement of temperature features of asphalt supporting layer in slab track system

Recently, asphalt supporting layer (ASL) has been adopted as a novel technology to waterproof subgrade and increase stability of slab track in China. Asphalt concrete is a typical thermal sensitive material and its mechanical properties are very susceptible to temperature conditions, which makes it very brittle at low temperature and easy to suffer from deformation at high temperature. Therefore, it is essential to investigate the temperature features of ASL in slab track during its service life. In this paper, the temperature distribution within ASL was studied by combining field recorded data and numerical simulation, and the effects of meteorological factors including air temperature, solar radiation, and wind speed were numerically studied with emphasis. The results show that the temperature within ASL distributed non-uniformly along the cross section of ASL, and the temperature of the area directly underneath the track slab was much more stable than other areas exposed to the air. The variation of meteorological factors including air temperatures, solar radiation and wind speed has significant effects on the temperature of ASL, but it takes hours for the change of meteorological factors to be seen within ASL. There is alinear relation between the change of ASL temperature and the variation of air temperature and solar radiation incident, but the influence of wind speed decreases with the increasing of wind speed. Meanwhile, the temperature of ASL is moresusceptible to solar radiation and wind speed in summer, and it is more easily affected by air temperature in summer.

Arctic river temperature dynamics in a changing climate

AbstractClimate change in the Arctic is expected to have a major impact on stream ecosystems, affecting hydrological and thermal regimes. Although temperature is important to a range of in‐stream processes, previous Arctic stream temperature research is limited—focused on glacierised headwaters in summer—with limited attention to snowmelt streams and winter. This is the first high‐resolution study on stream temperature in north‐east Greenland (Zackenberg). Data were collected from five streams from September 2013 to September 2015 (24 months). During the winter, streams were largely frozen solid and water temperature variability low. Spring ice‐off date occurred simultaneously across all streams, but 11 days earlier in 2014 compared with 2015 due to thicker snow insulation. During summer, water temperature was highly variable and exhibited a strong relationship with meteorological variables, particularly incoming shortwave radiation and air temperature. Mean summer water temperature in these snowmelt streams was high compared with streams studied previously in Svalbard, yet was lower in Swedish Lapland, as was expected given latitude. With global warning, Arctic stream thermal variability may be less in summer and increased during the winter due to higher summer air temperature and elevated winter precipitation, and the spring and autumn ice‐on and ice‐off dates may extend the flowing water season—in turn affecting stream productivity and diversity.

Temporal and spatial variations of urban climate and derivation of an urban climate map for Xi'an, China

Rapid urbanization have increased the sensitivity of urban environment to extreme weather. To improve the deteriorating urban environment, the current situation of urban climate should be evaluated systematically and applied to the planning process. This study reports on the temporal and spatial variability of urban climate and introduces a method for constructing an urban climate map based on spatial statistical analysis of field measurement data. Taking Xi’an, a metropolis in northern China, as the case study, we first conducted a 3-year meteorological investigation, including air temperature, relative humidity, and wind speed in both summer and winter. Meanwhile, five indicators with potential impacts on urban climate were selected to describe the urban characteristics. Then, the geographic information system was applied to integrate the meteorological data and urban characteristic data in order to assign more meteorological data. Next, three types of meteorological single-factor and thermal comfort spatial distribution maps were derived. The k-means clustering analysis method was then employed to classify three types of meteorological factors into seven zones in horizontal spatial dimension. Finally, urban climate maps were generated. This study can help planners quickly distinguish urban climate-sensitive and valuable zones in order to make better strategies for future development.

Snow is an important control of plant community functional composition in oroarctic tundra

The functional composition of plant communities is a critical modulator of climate change impacts on ecosystems, but it is not a simple function of regional climate. In the Arctic tundra, where climate change is proceeding the most rapidly, communities have not shifted their trait composition as predicted by spatial temperature–trait relationships. Important causal pathways are thus missing from models of trait composition change. Here, we study causes of plant community functional variation in an oroarctic tundra landscape in Kilpisjärvi, Finland. We consider the community-weighted means of plant vegetative height, as well as two traits related to the leaf economic spectrum. Specifically, we model their responses to locally measured summer air temperature, snow conditions, and soil resource levels. For each of the traits, we also quantify the importance of intraspecific trait variation (ITV) for between-community functional differences and trait–environment matching. Our study shows that in a tundra landscape (1) snow is the most influential abiotic variable affecting functional composition, (2) vegetation height is under weak local environmental control, whereas leaf economics is under strong local environmental control, (3) the relative magnitude of ITV differs between traits, and (4) ITV is not very consequential for community-level trait–environment relationships. Our analyses highlight the importance of winter conditions for community functional composition in seasonal areas. We show that winter climate change can either amplify or counter the effects summer warming, depending on the trait.