Regional Air Temperature Research Articles

Estimativa da Temperatura do Ar Utilizando Fatores Climáticos nas Regiões Canavieiras Brasileiras

Abstract This study aimed to estimate the minimum and maximum monthly air temperatures in the sugarcane regions of Brazil. A 30-year historical series (1988-2018) of maximum (Tmax) and minimum (Tmin) air temperatures from the NASA/POWER platform was used for 62 locations that produce sugarcane in Brazil. Multiple linear regression was used for data modeling, in which the dependent variables were Tmin and Tmax and the independent variables were latitude, longitude, and altitude. The comparison between estimation models and the real data was performed using the statistical indices MAPE (accuracy) and adjusted coefficient of determination (R2adj) (precision). The lowest MAPE values of the models for estimating the minimum air temperature occurred mainly in the North during February, March, and January. Also, the most accurate models for estimating the maximum air temperature occurred in the Southeast region during January, February, and March. The MAPE and R2adj values showed accuracy and precision in the models for estimating both the maximum and minimum temperatures, indicating that the equations can be used to estimate temperatures in sugarcane areas. The Tmin estimation model for the Southeast region in July shows the best performance, with a MAPE value of 1.28 and an R2adj of 0.94. The Tmax model of the North region for September presents higher precision and accuracy, with values of 1.28 and 0.96, respectively.

Association analysis on spatiotemporal characteristics of block-scale urban thermal environments based on a field mobile survey in Guangzhou, China

City blocks typically exhibit diverse thermal environmental characteristics due to their self-character complex spatial morphology and lateral thermal interactions from neighboring blocks. A field survey illustrating the spatiotemporal characteristics of block-scale thermal environments is urgently required to explore the inner-associated effects. A mobile survey method was conducted with two selected typical case regions during summer in Guangzhou, China. A block-based local climate zone (LCZ) mapping method was applied to the case regions, and diversified LCZ types that coexist in irregular states were obtained. Then, a multi-step data processing method integrating temporal correction and GIS-based spatial analysis was implemented to obtain the spatiotemporal distribution atlas of air temperature in LCZ blocks. Throughout this study, the air temperatures displayed time-varying characteristics and changed significantly with LCZ types. The correlation analysis showed that the sky view factor and pervious surface fraction present significant positive effects on block-scale air temperature during the daytime. Next, a spatial heterogeneity analysis conducted by fitted semivariogram curves at different times revealed the spatial variability of the urban thermal environment. Additionally, further spatial autocorrelation analysis of thermal interactions between blocks resulted in significant spatial cluster characteristics of air temperatures in the case regions.

Comparison of Noble Gas Temperature with Recent Mean Annual Air and Soil Temperature in different regions of Hungary

This paper describes the relation of noble gas temperature (NGT) and mean annual air (MAAT) and soil (MAST) temperature through studying water samples and meteorological data from six Hungarian regions. Alluvial plains, hilly and mountainous regions were studied to investigate the effects of geomorphological, hydrogeological and micro-climatic conditions. Water samples were collected from springs and wells fed from different aquifers. Comparing NGTs derived from these water samples with the MAAT and MAST values of the given region, we identified differences between the sampled areas. In case of the Geresd Hills, Mezőföld, Danube-Tisza Interfluves and Nyírség, the NGTs (13.0 ± 0.9 °C, 12.1 ± 1.1 °C, 12.1 ± 0.6 °C and 12.7 ± 1.6 °C, respectively) generally reflect MAST, however in karstic Bükk Mts. (6.8 ± 0.6 °C) and Mecsek Mts. (10.7 ± 1.9 °C) they are closer to MAAT. Consequently, it can be concluded that the direct relationship between noble gas temperature and mean annual air temperature is not always as well-defined as it is often assumed. It is shown that MAAT and MAST should be distinguished, especially when using NGT as a paleoclimate proxy.

An experimental comparison on regional thermal environment of the high-density enclosed building groups with retro-reflective and high-reflective coatings

Highly-reflective coatings (HR-coatings) are used to reduce the building heat gain and thereby, alleviate urban heat island, but the solar radiation reflected by HR-coatings will be absorbed by the surrounding building surfaces and solar heat gain will not be reduced or even increase. To overcome this inherent optical defect of HR-coatings, Retro-reflective coatings (RR-coatings) are proposed to reflect solar radiation along the incident direction with the potential to improve the urban thermal environment. Selecting the reasonable reflective coating is important to improve outdoor thermal environment, especially for high-density enclosed building groups. According to this aim, RR-coatings and HR-coatings were covered on two small-scale models of high-density enclosed building groups. The regional albedo, wall temperature and air temperature were taken as the evaluation parameters to compare the impact of RR-coatings and HR-coatings on the regional thermal environment of the high-density enclosed building groups. Experimental results showed compared with HR-coating model, RR-coating model had better cooling potential, and its peak regional albedo was increased by 5.0%. And air temperature in enclosed space of RR-coating model was 2.3℃ lower than that of HR-coating model, but they were higher than outdoor natural air temperature. Moreover, compared to HR-coatings, covering RR-coatings could reduce the peak and average wall temperature by 2.5℃∼15.2℃ & 0.3℃∼3.8℃ in the daytime and 1.3℃∼7.9℃ & 0.2℃∼4.4℃ in the nighttime, and its application in the roof and east wall had the higher efficiency.

Factors Influencing the Interannual Variation in Biomass of Bottom-Cultured Yesso Scallop (Patinopecten yessoensis) in the Changhai Sea Area, China

Understanding how environmental factors impact the interannual variation in scallop growth and subsequently developing an easily obtained parameter to indicate this variation could provide a scientific basis for optimizing their aquaculture. In this study, we have set a growth scenario of uniformly sowed scallops of the same initial size in the Changhai sea area. The Yesso scallop culture ecosystem model was used to simulate the growth of bottom-cultured Yesso scallop each year from December 1, 2006 to November 30, 2017. The results show that the annual growth rate was higher in the northwest than in the southeast, and there were obvious high-value areas near the islands. The scallop biomass was significantly lower in 2009–2010 and reached its highest point in 2013–2014. Based on the match-mismatch conditions of bottom-water temperature, food availability, and the Yesso scallop growth process, three factors were determined: suitable growth days (SGD), restricted growth days (RGD), and food accumulation (FA). Subsequently, a multiple regression relationship was proposed with scallop biomass to explore the reasons affecting the interannual variations in scallop growth. We found that the anomaly of the contribution of SGD and FA for the scallop growth was small, and the interannual variation in scallop biomass was mainly regulated by RGD in winter. Our results indicated that the interannual variation in RGD in winter was closely related to the regional averaged air temperature in early winter. The air temperature in early winter is easily obtained in practice. Consequently, it could be used to predict the interannual growth of bottom-cultured scallops to improve aquaculture planning and management.

Numerical evaluation of the performance of two air distribution systems in a generic multi-layer vertical farm

The uniformity of the environmental conditions in a vertical farm can be poor due to multi-layer cultivation shelves, crop resistance to airflow, and excessive heat generated by artificial lighting, decreasing overall crop yield and quality. This study evaluates the performance of two air distribution systems, i.e., long-side air supply and short-side air supply, in a generic multi-layer vertical farm using a validated computational fluid dynamics (CFD) modeling approach. The simulation results show that under identical airflow rates, the average air temperature in crop regions from short-side air supply is higher than the long-side case. In addition, stagnation regions exist in both scenarios, where the removal efficiency of water vapor and heat is low. Further study is required to improve the uniformity of air distribution in crop regions.

Statistical analysis of regional air temperature characteristics before and after dam construction

Dam construction brings both benefits and harms to the ecological environment. This paper focuses on the impact of the construction of mega-dams on regional climate. Based on the national precipitation and temperature data from 1990 to 2012 from more than 2400 national stations of the National Meteorological Information Center, this paper analyzes Xiaolangdi Dam's influence on the Yellow River's climate and the Three Gorges Dam of the Yangtze River with geostatistics knowledge. The following results are obtained. (1) According to the analysis of the climate time and space distribution in the Yellow River Basin and the Yangtze River Basin, the dam's construction caused a drop in temperature in the reservoir area, which decreased by about 0.12 °C. On the other hand, the dam's construction also caused the temperature in the downstream area to rise by about 0.6 °C. (2) According to the analysis of regional climate correlation, the rise of the dam's water level will cause the temperature of the reservoir area to drop to a certain extent. The correlation between the temperature in the Three Gorges and the water level changes in the Three Gorges reaches −0.578. (3) According to regional climate statistics analysis, the dam's construction has reduced the temperature difference in the reservoir area.

The effect of background wind on summertime daily maximum air temperature in Kowloon, Hong Kong

The increased intensity of extreme weather events (e.g., heatwaves) that is predicted to occur due to global climate change could significantly impact human health, biodiversity, and infrastructure integrity in cities. As one of the most densely constructed cities in the world, Hong Kong has been experiencing increasingly intense heatwaves in recent years. However, the city presents a challenging site for studying urban climate due to its complex topography. Using observed weather data for clear summer (June to August) days from 2000 to 2020, we examine the relationship between background wind and daily maximum temperature in Kowloon, Hong Kong, and investigate how this relationship is affected by geographical location, land cover, and topography. We reveal the distribution of near-surface wind fields under calm weather conditions, which provides a basis for the analysis of relationship between background wind and maximum temperature in urban areas under windy conditions. We find that the maximum surface air temperature in coastal regions is significantly influenced by the background wind direction. For weather stations located in the Kowloon Peninsula, a larger background wind speed is associated with a faster increase in daily maximum temperature when the background temperature rises. We find that the mountain warming effect is influential in areas at the foot of a mountain, even though the maximum terrain height is only approximately 500 m a.s.l. These findings on the daily maximum temperature behavior under different background wind conditions provide a possible way to predict extreme high-temperature patterns in different regions of Hong Kong.

The result of the comparative use of OCO-2 information to find the relationship between changes in the atmospheric concentration of CO2 and air temperature in the Argentine Islands and Ukraine.

The results of comparative analysis of data of data of changes CO2 concentrations in the atmosphere over the polar regions adjacent to the "Akademik Vernadsky" station (the size of the study area 1.5° × 1.5°, or approximately 166 km by 75 km) were obtained satellite Orbiting Carbon Observatory (OCO-2) and air temperature according to ground meteorological observations at the "Akademik Vernadsky" station for 2014-2020. From obtained graph, we can see that the air temperature and CO2 concentration in the atmosphere over the study area tend to increase slowly. In addition, the analysis of the above results showed that in this way it is possible to determine the integrated trends in the impact of greenhouse gas content in the atmosphere on air temperature. A comparative analysis of data of data of changes CO2 concentrations according to OCO-2 between regions where there is a direct anthropogenic impact (Ukraine) and the region where anthropogenic impact is minimized (areas adjacent to the "Akademik Vernadsky" station) for 2014-2020. It was found that CO2 concentrations over areas with direct anthropogenic impact are growing much faster than over areas where there is no such impact at all. However, we see that CO2 concentrations tend to increase in both cases. Based on the obtained results, it was determined that conducting a comprehensive, simultaneous and consistent with satellite observations measurements of various series of variables, will provide an opportunity to optimize information of changes in climatic parameters (air temperature) in the polar regions.

Inter-annual Variability of Snowfall in the Lower Peninsula of Michigan

Winter snowfall, particularly lake-contributed snowfall, has a significant impact on the society and environment in the Great Lakes regions including transportation, tourism, agriculture, and ecosystem. Understanding the inter-annual variability of snowfall will provide sound basis for local community safety management and reduce its environmental impacts on agriculture and ecosystems. This study attempts to understand the trend and inter-annual variability in snowfall in the Lower Peninsula of Michigan (LPM) using statistical analysis based on snowfall measurements from eight weather stations. Our study demonstrates that snowfall has significantly increased from 1932 to 2015. Correlation analysis suggests that regional average air temperatures have a strong negative relationship with snowfall in the LPM. On average, approximately 27% of inter-annual variability in snowfall can be explained by regional average air temperatures. ENSO events are also negatively related to snowfall in the LPM and can explain ~8% of inter-annual variability. The North Atlantic Oscillation (NAO) does not have strong influence on snowfall. Composite analysis demonstrates that on an annual basis, more snowfall occurs during the years with higher maximum ice cover (MIC) than during the years with lower MIC in Lake Michigan. Higher MIC is often associated with lower air temperatures which are negatively related to snowfall. This study could provide insight on future snow related climate model improvement and weather forecasting.

IMPACT OF TEMPERATURE CHANGE ON GROWTH OF LABEO ROHITA: DEVELOPMENT OF A GROWTH MODEL

Enhanced temperature is one of the most important drivers of climate change as evidenced by a perceptible rise of air and water temperature in various regions of India. Unit rise in water temperature affect the physiological features of freshwater fish in aquaculture. Investigations were conducted to assess the impact of increasing water temperature of 29 oC, 30 oC, 31 oC, 32 oC, 33 oC, 34 oC and 35 oC on the growth, Labeo rohita fingerlings reared for five weeks in aquarium. The fishes were fed pelletised feed ad libitum. Fish reared at 34 oC water temperature exhibited significantly (P<0.05) faster growth (SGR-2.36 % body weight per day) than those reared at other temperatures. The change in growth rates were insignificant between 29 oC, 30 oC, 31 oC and 32 oC treatment groups but growth rates significantly increased in the temperatures ranging from 32 oC to 34 oC and there after it decreased. A linear growth model of L. rohita fingerlings growth has been developed using the data generated. This simple growth model provided a reliable projection of growth (SGR %) with unit rise of temperature within the range of 29 o to 34 oC. This will help fish culturists to develop adaptation strategies with regard to suitability of fish species and fish culture practices under the climate warming scenarios. Key words: Temperature, Growth, Indian Major Carp, Labeo rohita

Influences of local hydroclimatology and teleconnections on Florida's precipitation and temperature variability

AbstractUnderstanding the influences of local hydroclimatology and two large‐scale oceanic‐atmospheric oscillations (i.e., Atlantic Multidecadal Oscillation (AMO) and El Niño‐Southern Oscillation (ENSO)) on seasonal precipitation (P) and temperature (T) relationships for a tropical region (i.e., Florida) is the focus of this study. The warm and cool phases of AMO and ENSO are initially identified using sea surface temperatures (SSTs). The associations of SSTs and regional minimum, maximum and average surface air temperatures (SATs) with precipitation are then evaluated. The seasonal variations in P‐SATs and P‐SSTs associations considering AMO and ENSO phases for sites in (1) two soil temperature regimes (i.e., thermic and hyperthermic); (2) urban and non‐urban regions; and (3) regions with and without water bodies, are analysed using two monthly datasets. The analyses are carried out using trend tests, two association measures, nonparametric and parametric statistical hypothesis tests and kernel density estimates. Decreasing (increasing) trend in precipitation (SATs) is noted in the recent multi‐decadal period (1985–2019) compared to the previous one (1950–1984) indicating a progression towards warmer and drier climatic conditions across Florida. Spatially and temporally non‐uniform variations in the associations of precipitation with SATs and SSTs are noted. Strong positive (weak negative) P–T associations are noted during the wet (dry) season for both AMO phases and El Niño, while significant (positive) P–T associations are observed across southern Florida during La Niña in the dry season. The seasonal influences are predominant in governing the P–T relationship over the regions with and without water bodies; however, considerable variations between El Niño and La Niña are noted during the dry season. The climate variability influences on P–T correlations for hyperthermic and thermic soil zones are found to be insignificant (significant) during the wet (dry) season. Nonparametric clustering is performed to identify the spatial clusters exhibiting homogeneous P–T relationships considering seasonal and climate variability influences.

Water availability influences thermal safety margins for leaves

Abstract One application of plant physiological heat tolerance measurements is the assessment of vulnerability to increasing environmental temperatures under climatic change. A thermal safety margin (TSM), the difference between physiological tolerance and environmental temperature, is a common metric for the assessment of plant thermal vulnerability. However, there are biological and methodological aspects to consider when evaluating thermal vulnerability that have the potential to substantially alter the assessments. Two such aspects include the leaf to air temperature relationship and the scale at which air temperature data are collected. We grew plants of a desert species, Myoporum montanum, in situ under water‐stressed and well‐watered conditions, and measured their leaf temperatures and photosynthetic heat tolerance (T50 threshold) every third day over 12 days in summer. Thermal safety margins were calculated based on leaf temperatures and compared to those calculated with local and regional air temperatures. We found that heat tolerance and the thermal vulnerability assessment of a plant changed with water status. When water was readily available, plants maintained wide leaf temperature safety margins and displayed partial homeothermy. When cooling via transpiration was limited, increasing leaf temperature corresponded with occurrences of leaf poikilo‐ and megathermy, higher heat tolerance and narrower safety margins. Our study shows high physiological heat thresholds are not necessarily reflective of wide safety margins, but instead can indicate a greater vulnerability and increased risk of heat stress exposure. Calculating TSMs using air temperatures can also substantially alter margin widths. Where possible, the use of leaf temperatures in assessments of thermal vulnerability will lead to more meaningful vulnerability assessments. We recommend considering the source and temporal pairing of temperature measurements as well as plant water status, when measuring and interpreting plant TSMs. A free Plain Language Summary can be found within the Supporting Information of this article.

An Assessment of the Economic Viability of Engine Wash Procedures on the Lifecycle Costs of an Aircraft Fleet.

Aircraft operators find themselves in a highly complex and competitive environment in which the economic pressure on companies is constantly increasing. In addition, annual air traffic is expected to increase by 4-5% (despite the Covid-19 pandemic), which requires significant improvements of aircraft efficiency. To address this on European and global scale, long-term economic and ecologic goals have been defined in the "Flightpath 2050" by the European Commission. One way to reduce both operating costs and environmental impact is to reduce aircraft fuel consumption. Regularly performed engine washes can reduce the accumulation of dirt and debris in the engine and partially restore the performance degradation as well as lower the wear and tear of the engine. This results in lower exhaust gas temperature and a slower aging engine with longer intervals between required maintenance events. &#x0D; Most engine wash studies have drawn their system boundary around the engine and consider only the one-time improvements that result from a wash. Long term effects that build on these improvements, such as changes in maintenance and replacement cycles, are usually not considered. Few studies are available that extend their system boundary and consider changes in maintenance costs. Yet the value of engine wash processes is often quantified on an insufficient setting, especially when environmental conditions and fleet effects are neglected. To estimate the overall benefit and assess the impact on lifecycle costs, a full evaluation of engine wash within an entire fleet is required and fleet effects such as the possibility of downrating the engine for a smaller aircraft should be considered. &#x0D; The aim of this work is to quantify the true value of engine wash procedures considering both physical constraints as well as operational fleet wide considerations. Using discrete event simulations at fleet level, a detailed investigation of the primary and secondary effects and a quantification of lifecycle costs will be performed. Particular attention will be paid to the influence on maintenance costs as well as the economic effect of increased time on wing. With the help of an improved environmental modeling and with the consideration of fleet effects, a holistic statement is possible.&#x0D; To investigate this problem, a lifecycle costing method, named LYFE, developed by DLR will be used. LYFE uses discrete event simulation to model the product lifecycle from order to operation until disposal of an aircraft fleet. For this analysis the tool will be extended to separate the lifecycles of the engines and those of the aircraft, so the engines can change the aircraft and the downrating of the engine for a smaller aircraft can be modeled. In order to represent the contamination and the performance degradation of the engines as realistically as possible, data on the outside air temperature, dust, pollution and other particles in certain regions at the various airports are also included in the tool. Furthermore, the option of derating the engine’s thrust is considered. The lifecycle of two different fleets will be simulated and studied. The difference between the two fleets is that the baseline fleet does not perform any engine washes, while the study fleet performs engine washes. Both fleets consist of different types of aircraft, so that downrating of the engines is possible and the entire lifecycles of the aircraft can be mapped. The evaluation follows two approaches: firstly, the engine wash is carried out and examined regularly; secondly, the intervals at which the engine wash is carried out are optimized in such a way that the lifecycle costs of the fleet are as low as possible. In both cases the number of engines necessary to operate the fleet will be the basis for an overall statement.&#x0D; With this holistic view of how engine washes within a fleet affect its lifecycle costs, a much more realistic statement about this on-wing maintenance action is possible.

Application of a Diatom Transfer Function to Quantitative Paleoclimatic Reconstruction — A Case Study of Yunlong Lake, Southwest China

Although diatom records from lake sediments have been used for quantitative paleoclimatic reconstruction, their validity and sensitivity have rarely been tested rigorously. At Yunlong Lake, an alpine lake in Southwest China, we studied the seasonal succession of diatom assemblages to produce a mean surface water temperature (MSWT) transfer function. In addition, based on the spatial distribution of surface diatom assemblages with water depth, we produced a diatom-water depth (WD) transfer function. Combined with the analysis of diatom assemblages in a sediment core (YL2013-A), changes in surface water temperature and water level over the last ∼100 years were quantitatively reconstructed using the diatom-based transfer functions. Comparison with records of regional meteorology and reservoir water capacity revealed that the diatom-based lake water level reconstruction is a sensitive indicator of short-term fluctuations in precipitation, and it also reflects a long-term stepwise rise in water level caused by the impounding and large-scale extension of the reservoir. In addition, the diatom-inferred MSWT is consistent with the changes in air temperature prior to large-scale human disturbance of the site. However, after the extension of the reservoir, although the regional air temperature continued to increase, the water temperature decreased substantially. This suggests that the large increase in lake water volume in the short term led to a decrease in the average water temperature, which in turn led to the occurrence of a diatom bloom in the cold season. The results demonstrate that diatom transfer functions based on modern observations of the same lake has a high environmental sensitivity and can be used for the quantitative reconstruction of regional climate change. Overall, our findings provide a foundation for the use of lake diatom records for quantitative paleoclimatic reconstruction on various timescales.

Winter–spring warming in the North Atlantic during the last 2000 years: evidence from southwest Iceland

Abstract. Temperature reconstructions from the Northern Hemisphere (NH) generally indicate cooling over the Holocene, which is often attributed to decreasing summer insolation. However, climate model simulations predict that rising atmospheric CO2 concentrations and the collapse of the Laurentide Ice Sheet caused mean annual warming during this epoch. This contrast could reflect a seasonal bias in temperature proxies, and particularly a lack of proxies that record cold (late fall–early spring) season temperatures, or inaccuracies in climate model predictions of NH temperature. We reconstructed winter–spring temperatures during the Common Era (i.e., the last 2000 years) using alkenones, lipids produced by Isochrysidales haptophyte algae that bloom during spring ice-out, preserved in sediments from Vestra Gíslholtsvatn (VGHV), southwest Iceland. Our record indicates that winter–spring temperatures warmed during the last 2000 years, in contrast to most NH averages. Sensitivity tests with a lake energy balance model suggest that warmer winter and spring air temperatures result in earlier ice-out dates and warmer spring lake water temperatures and therefore warming in our proxy record. Regional air temperatures are strongly influenced by sea surface temperatures during the winter and spring season. Sea surface temperatures (SSTs) respond to both changes in ocean circulation and gradual changes in insolation. We also found distinct seasonal differences in centennial-scale, cold-season temperature variations in VGHV compared to existing records of summer and annual temperatures from Iceland. Multi-decadal to centennial-scale changes in winter–spring temperatures were strongly modulated by internal climate variability and changes in regional ocean circulation, which can result in winter and spring warming in Iceland even after a major negative radiative perturbation.

The use of stable oxygen and nitrogen isotopic signatures to reveal variations in the nitrate formation pathways and sources in different seasons and regions in China

Nitrate (NO3−) is one of the most important inorganic ions in fine particulate (PM2.5) and drives regional haze formation; however, the NO3− sources and formation mechanisms in different seasons and regions are still debated. Here, PM2.5 samples were collected from Kunming and Nanning in southwestern China from September 1, 2017, to February 28, 2018 (spanning warm and cold months). We measured the daily O and N isotopic compositions of NO3− (δ18O–NO3− and δ15N–NO3−), estimated the δ18O–HNO3 values produced by different oxidation pathways, and quantified the NO3− formation pathways based on the isotope mass-balance equation. Our results showed that the δ18O–NO3− values in Kunming (65.3 ± 7.6‰) and Nanning (67.7 ± 10.1‰) are close to the δ18O–HNO3 values arising from the OH radical pathway (POH, 54.7 ± 1.2‰ to 61.2 ± 1.8‰), suggesting that the δ18O–NO3− values are mainly influenced by POH, which showed a contribution greater than 74%. Stronger surface solar radiation and higher air temperatures in low-latitude regions and warm months increased the amount of HNO3 produced by POH and reduced the amount of HNO3 produced by PN2O5, which produced low δ18O–NO3− values. Increased air pollution emissions decreased the contribution from POH and increased the contribution from N2O5 and NO3 pathways (PN2O5+NO3). The δ15N–NO3− values of PM2.5 in Kunming (7.3 ± 2.8‰) were slightly higher than those in Nanning (2.8 ± 2.7‰). The increased NOx emissions with positive isotopic values led to high δ15N–NO3− values in northern China and during cold months. A higher fNO2 (fNO2 = NO2/(NO + NO2), temperature, and contribution of POH produced lower N isotope fractionation between NOx and δ15N–NO3−, which was found to further decrease the δ15N–NO3– values in southwestern China and during warm months.

Regularities of soil temperature changes during the period with snow cover in modern climatic conditions of the Eurasian Subarctic

The influence of snow cover on the dynamics of soil temperature in the modern climatic conditions of the Eurasian Subarctic was investigated through a quantitative assessment of the features of the seasonal and long-term variation of parameters. Seasonal and long-term values of soil temperature for stable snow period decrease from west to east: a decrease of snow thickness and air temperature from west to east of Eurasia leads to a weakening of the heat-insulating properties of the snow cover with a significant decrease in regional air temperatures. With the emergence of a stable snow cover, the soil temperature seasonal and long-term standard deviation sharply decreases compared to the autumn and spring periods. With the appearance of snow cover, the soil temperature standard deviation drops sharply compared to the autumn and spring periods. An exception is the northeast of Siberia: here, a relatively small thickness of snow determines a noticeable dependence of the course of soil temperature on the dynamics of surface air temperature. There are no significant long-term trends in soil temperature due to its low variability during winter period. Analysis of the course of the studied characteristics anomalies showed an insignificant and non-systematic number of their coincidences. Currently, we have not found similar research results for large regions. The revealed patterns can be used in the analysis of the results of monitoring the state of the land surface, in the development of remote sensing algorithms, in the refinement of predictive scenarios of environmental changes.

Spatiotemporal variations and regional differences in air temperature in the permafrost regions in the Northern Hemisphere during 1980–2018

Surface air temperature is an important factor for the permafrost thermal state in the Northern Hemisphere. It is therefore necessary to understand the variations and regional differences in air temperature to determine the interactions between permafrost degradation and climate change. In this study, we used observational data from the National Centers for Environmental Information, the China Meteorological Administration, and the World Data Centre for Meteorology to quantitatively analyze the variations and regional differences in air temperature from 1980 to 2018. The results demonstrated that the annual mean air temperatures were low in continuous permafrost regions and high in sporadic and isolated permafrost regions, with a significant warming rate of 0.371 ± 0.086 °C/decade. Air temperatures warmed the slowest during the winter and fastest during the spring, and no “warming hiatus” was observed in the permafrost regions of the Northern Hemisphere. The spatial patterns of freezing degree-days (FDDs) and thawing degree-days (TDDs) had different spatial characteristics. The decreasing rate of FDDs was −6.97 °C·days/year, while the increasing rate of TDDs was 6.4 °C·days/year. The air temperatures and warming trends had largely regional differences with respect to high latitude, transitional, and high altitude permafrost regions. Air temperature and its warming trend was the highest in high altitude regions. In addition, air temperature warming trends gradually decreased from the continuous permafrost zone to the island permafrost zone. The FDDs had a significant decreasing trend from the continuous permafrost zone to the island permafrost zone, whereas TDDs exhibited the opposite trend. The results indicate that the air temperature warming rate in the permafrost regions was approximately 2.0 times that of the global warming rate, and 1.3 times the global land warming rate from 1980 to 2018. These findings offer a perspective on the differences in permafrost and its thermal state across different regions under climate change.

Microclimate and habitat heterogeneity as important drivers of soil Collembola in a karst collapse doline in the temperate zone

AbstractChanges in well‐delimited Collembola communities along a steep microclimatic gradient at the entrance of Silická ľadnica Ice Cave, Slovakia, were investigated after 10 years (2007, 2017). We focused on the occurrence of psychrophilic and endemic species occupying this unique karst collapse doline and their response to climatic singularities in the given years as well as the increasing trend in regional air temperature. The soil temperature means at sites across the doline slope corresponded with climatic trends in the periods 2006–2007 and 2016–2017. Significantly lower average soil temperatures but significantly higher mean abundances, species richness, and diversity indices of the collembolan communities were recorded at sites during the second study period, which was characterized by more favorable soil microclimatic conditions (temperature and moisture content) compared to the first period. The dominance structure and community composition of the studied assemblages appeared to be relatively constant after 10 years, indicating stable collembolan communities, especially at cold sites at the bottom of the doline. Redundancy ordination analysis documented a clear delimitation of the communities in relation to the soil temperature, pH, and C:N ratio in both periods. Long‐term (30‐year) regional climatic data showed an increasing trend of annual air temperature means and precipitation. However, an increase in the number and abundance of xerothermophilous species and a decline in psychrophilic species (mostly endemic) along the gradient as a potential response of the increasing regional temperature were not observed, suggesting the high resilience of these communities. Microclimate and habitat heterogeneity are probably major drivers of soil Collembola communities along the steep microclimatic gradient of a karst collapse doline, which was observed by the repeated sampling after 10 years. Karst dolines as potentially important local sources of ɑ‐diversity will likely become increasingly indispensable refugia for local biodiversity under ongoing global warming, thus deserving reliable conservation.