Variations In Thermal Conditions Research Articles

Effect of thermal environmental factors on female students during summer and spring season: promoting a sustainable campus initiative

PurposeThe present study was conducted at the female campus of the United Arab Emirates University (UAEU), with a specific emphasis on the outside environment. This study aims to explore the influence of external conditions, including AC (AC), Time of Day (TD) variations, and Landscape Sites (LS) differences, on changes in physiological temperatures. Specifically, the focus is on understanding the dynamics of skin and abaya temperature (AT) when exposed to transient thermal environments, considering factors such as AC, LS, and different TD. By investigating these parameters, the research aims to gain insights into the thermal dynamics experienced by female students at the UAEU campus which can further lead to evaluate the thermal comfort (TC).Design/methodology/approachThe study involved three college-aged female participants simulating a daily walk to class on a arid tropical university campus. Real-time thermal measures were captured at 10-min intervals using the FLIR Thermal Camera. Statistical analyses, including the Kruskal–Wallis test and Don Bonferroni pairwise comparisons, were employed to assess significant differences in thermal conditions based on AC, TD, and LS. These tests rigorously analyzed the data to identify statistically significant variations in thermal conditions among the specified factors. Additionally, temperature data from the ECMWF ERA5 dataset, covering global climate from January 1940 to the present, was utilized. The GRADS application on a Linux-based system was used for data visualization and map chart creation.FindingsThe study reveals a slight influence of AC on both Abaya temperatures (AT) and Skin temperatures (ST) during the summer, with more pronounced diurnal changes in the afternoon significantly affecting both metrics. Site characteristics minimally impact AT, but they have a noteworthy effect on ST. In the spring season, AT and ST remain unaffected by AC, while temporal fluctuations, particularly in the afternoon, exert a significant influence. LS variations show statistically insignificant impacts on both AT and ST. Additionally, temperature maps for specific 2023 dates provide distinctive trends in the UAE, offering insights into dynamic climatic conditions varying by season and TD.Originality/valueThe study aims to address a knowledge gap by investigating the influence of AC, TD, and LS variations on physiological temperature change, specifically focusing on skin and AT. This investigation is conducted in the context of individuals exposed to thermal environmental factors within a arid tropical university campus setting.Practical implicationsThis research contributes to the existing knowledge by providing specific data on thermal conditions within the campus, enabling informed decision-making for creating a more comfortable and conducive environment for the students, thereby contributing to the goal of a sustainable campus.

Topography formation driven by sublimation of pure species on icy airless worlds

Sublimation can drive morphologic changes on the surfaces of icy, airless worlds; the magnitude of these changes depends sensitively on their surface shape, subsurface geology, and volatility of the ice species present. To predict the steady-state and stability of the surface, we examine the molecular transport conditions and their constraints for several pure species sublimating from irregular surfaces in a free-molecular regime subject to variations in thermal conditions at or near the surface. We find that the temperature difference, ΔT∗ between the high and low points on the surface required for morphological instability changes of a given surface geometry increases as the volatility of the ice species increases. From Figure 4, for k=1 and Ts=150K, ΔT∗ is about 3K for H2O and 5K for CO2. Furthermore, we developed an analytical relationship between the saturation vapor pressure of a pure species, its surface geometry and temperature profile, and the required molecular transport conditions.

Microstructural and Mechanical Properties of CAP-WAAM Single-Track Al5356 Specimens of Differing Scale

The mass production of metallic components requires high agility in the working process conditioned by the necessity of building details of different shapes and sizes. Changing the size of the components theoretically influences the thermal dissipation capability of the same, which could lead to a change in their structure and mechanical properties. This is particularly important when aluminum alloys are concerned. For this reason, two Al5356 single-track specimens were built using the same technological conditions of layer deposition by varying only their geometrical size. In all cases, the specimens were wire and arc additively manufactured (WAAM) using a process based on gas metal arc welding (GMAW) in the cold arc pulse mode (CAP). The structure of both specimens was studied and defects along their surfaces were detected in the form of micro-pores and micro-cracks. A high concentration of undissolved Mg particles was also detected, along with some standalone Si particles. Uniformity in the build-up process was achieved, which led to the formation of nearly identical structures in the specimens. Subsequently, the resultant mechanical properties were also highly comparable. This indicates that the geometry-related variation in thermal conditions has an insignificant influence on the component’s structure and properties.

Genetic background and thermal regime influence adaptation to novel environment in the seed beetle, Callosobruchus maculatus.

Climate change is associated with the increase in both the mean and variability of thermal conditions. Therefore, the use of more realistic fluctuating thermal regimes is the most appropriate laboratory method for predicting population responses to thermal heterogeneity. However, the long- and short-term implications of evolving under such conditions are not well understood. Here, we examined differences in key life-history traits among populations of seed beetles (Callosobruchus maculatus) that evolved under either constant control conditions or in an environment with fluctuating daily temperatures. Specifically, individuals from two distinct genetic backgrounds were kept for 19 generations at one of two temperatures, a constant temperature (T = 29 °C) or a fluctuating daily cycle (Tmean = 33 °C, Tmax = 40 °C, and Tmin = 26 °C), and were assayed either in their evolved environment or in the other environment. We found that beetles that evolved in fluctuating environments but were then switched to constant 29 °C conditions had far greater lifetime reproductive success compared with beetles that were kept in their evolved environments. This increase in reproductive success suggests that beetles raised in fluctuating environments may have evolved greater thermal breadth than control condition beetles. In addition, the degree of sexual dimorphism in body size and development varied as a function of genetic background, evolved thermal environment, and current temperature conditions. These results not only highlight the value of incorporating diel fluctuations into climate research but also suggest that populations that experience variability in temperature may be better able to respond to both short- and long-term changes in environmental conditions.

Site-specific Cu clustering and precipitation in laser powder-bed fusion 17–4 PH stainless steel

Thermal gyrations inherent to metal additive manufacturing (AM) result in complex microstructural heterogeneities that are linked to the process parameters, geometry, and alloy composition. AM 17–4 precipitation hardened (PH) stainless steel displays heterogeneities due to its multi-phase microstructure where different as-built phases have been reported. These phases include austenite, martensite, and ferrite, as well as varying degrees of AM induced Cu clustering and/or precipitation. To enable a systematic study of the evolution of these strengthening phases, we utilize a non-standard concentric scan strategy to achieve variations in thermal conditions across a build. Using atom probe microscopy and thermal modeling, we show that the response of Cu varies across the build from no clustering at the outer regions to an increased tendency for Cu precipitation towards the center. Our results will enable the tuning of processing parameters to achieve homogenous Cu precipitation, and thus improve mechanical properties of AM 17–4 PH.

Multi-Scale Influence Analysis of Urban Shadow and Spatial Form Features on Urban Thermal Environment

In urban thermal environment research (UTE), urban shadows formed by buildings and trees contribute to significant variations in thermal conditions, particularly during the mid-day period. This study investigated the multi-scale effects of indicators, including urban shadows, on UTE, focusing specifically on the mid-day hours. It integrated field temperature measurements and drone aerial data from multiple city blocks. Considering both urban shadows and direct solar radiation, a linear mixed-effects model was employed to study the multi-scale effects of urban morphological indicators. Results showed that: (1) UTE is a multi-scale, multi-factor phenomenon, with thermal effects manifesting at specific scales. Under shadow conditions, smaller scales (10–20 m) of landscape heterogeneity and larger scales (300–400 m) of landscape consistency better explained temperature variations mid-day. Conversely, under direct sunlight, temperature was primarily influenced by larger scales (150–300 m). (2) Trees significantly reduced temperature; 100% tree canopy cover within a 10-m radius reduced air temperatures by approximately 2 °C mid-day. However, there is no significant correlation between temperature and green spaces. (3) Building area and height were significantly correlated with temperature. Specifically, an increase in building area beyond 150 m, especially within a 300-m radius, leads to higher temperatures. Conversely, building height within a 10–20 m range exhibits significant cooling effects. These findings provide crucial reference data for micro-scale UTE investigations during mid-day hours and offer new strategies for urban planning and design.

Temperature variability and metabolic adaptation in terrestrial and aquatic ectotherms

Thermodynamics is a major factor determining rates of energy expenditure, rates of biochemical dynamics, and ultimately the biological and ecological processes linked with resilience to global warming in ectothermic organisms. Nonetheless, whether ectothermic organisms exhibit general adaptive metabolic responses to cope with worldwide variation in thermal conditions has remained as an open question. Here we combine a model comparison approach with a global dataset of standard metabolic rates (SMR), including 1,160 measurements across 788 species of aquatic invertebrates, insects, fishes, amphibians and reptiles, to investigate the association between metabolic rates and environmental temperatures in their respective habitats. Our analyses suggest that variation in SMR after removing allometric and thermodynamic effects is best explained by the temperature range encountered across seasons, which always provided a better fit than the average temperature for the hottest and coldest month and mean annual temperatures. This pattern was consistent across taxonomic groups and robust to sensitivity analyses. Nonetheless, aquatic and terrestrial lineages responded differently to seasonality, with SMR declining – 6.8% °C−1 of thermal range across seasons in aquatic organisms and increasing 2.8% °C−1 in terrestrial organisms. These responses may reflect alternative strategies to mitigate the impact of increments in warmer temperatures on energy expenditure, either by means of metabolic reduction in thermally homogeneous water bodies or effective behavioral thermoregulation to exploit temperature heterogeneity on land.

Features of Multiannual Air Temperature Variability in Poland (1951–2021)

Over the last 71 years, the air temperature in Poland has increased on average by 0.28 °C per decade—which gives a total change in this period exceeding 2 °C. The subject of this study was an analysis of the long-term variability of the Polish climate in terms of thermal characteristics. The aim of the research was to verify the hypothesis on the lack of homogeneity of this change and to identify points of significant acceleration of the observed tendencies. The analysis utilized the average monthly air temperature at selected synoptic stations in Poland over the period 1951–2021. The values were then processed into a reference series using Alexandersson’s method, which provided synthetic information on the variability in thermal conditions in the country. The analyses were carried out on an annual and seasonal basis. The values of the trend coefficients (and their statistical significance) were also calculated in shorter periods (minimum 30 years), which enabled determination of the stability of the observed changes’ tendencies. In addition to the analysis of the basic characteristics, non-parametric tests (Wilcoxon, Kruskal–Wallis) were used to verify shifts between decades. The annual and seasonal analyses showed the existence of sub-periods with different directions and scales of the observed tendencies. Additionally, statistically significant changes in decadal characteristics were noted, e.g., in the decades 2001–2010 and 2011–2020 in the case of annual temperature, and 1961–1970 and 1971–1980 in the case of the winter season.

СЕЗОННЫЕ ВАРИАЦИИ ТЕМПЕРАТУРЫ ПОВЕРХНОСТИ ОХОТСКОГО МОРЯ И ПРИЛЕГАЮЩИХ РАЙОНОВ ПО ДАННЫМ СПУТНИКОВЫХ НАБЛЮДЕНИЙ И РЕАНАЛИЗА ERA5

Using the method of harmonic analysis and EOF decomposition of SST data for the surface of the Sea of Okhotsk and adjacent water areas (42–60° N, 135–160° E, SakhNIRO database and ERA5 reanalysis for 1998–2020), the main features of seasonal variations in thermal conditions were determined. It was revealed that the amplitude of the annual harmonic, which plays a decisive role in the seasonal variations of SST, generally decreases in the direction from west to east throughout the study area, the lowest values are in the zones of quasi- stationary upwellings. The phase increases along the northwest-southeast axis, the total shift is 24–25° (about 3 weeks). In the spatial distribution of the first mode (all values are positive), the water area of the Sea of Japan, the NWPO, and the southwestern part of the Sea of Okhotsk are characterized by high values. Its time function is characterized by a pronounced annual cycle, with a maximum in August–September and a minimum in February–March. The spatial distribution of the second mode has a nodal line running along the Kuril Islands from the Sea of Okhotsk side. The mode values vary along the northwest–southeast axis, with maximum positive values on the northwestern shelf of the Sea of Okhotsk and negative values in the remote part of the NWPO. The time function of the second mode has a positive maximum in July–August and a negative minimum in November–December. This nature of the second mode shows that, against the background of the main SST field described by the first mode, a peculiar seasonal “heat wave” is distinguished, propagating from the northwest to the southeast and passing along this axis in about three weeks, which is an important specific feature of the thermal regime of the study area.

Dynamic effects of frequent step changes in outdoor microclimate environments on thermal sensation and dissatisfaction of pedestrian during summer

• Subjects’ dynamic thermal responses to frequent microclimatic step changes are investigated. • Comparison between surveyed dynamic thermal sensation and predicted sensation is made. • Equivalent UTCI* based on SWI and frequent step change effectiveness is proposed. • Applicability of UTCI* in evaluating thermal sensations under frequent step changes is evaluated. • Impacts of frequent microclimatic step changes on thermal dissatisfaction in summer are revealed. Humans engaging in outside activities are more likely to be exposed to frequent spatiotemporal step changes in outdoor thermal conditions, as opposed to constant thermal conditions staying indoors. Understanding pedestrians’ thermal reactions to such dynamic thermal settings is helpful for enhancing outdoor thermal comfort by providing spatiotemporal variations in thermal conditions. In this study, 48 subjects were tested about their thermal perceptions while being exposed alternately to direct sunlight and shade at different defined frequencies, in a series of 45 min experiment period. The experiments were designed to create step changes in microclimate environments. The study was carried out from May to July in a university campus in Hong Kong with subtropical weather conditions. Results show that subjective thermal perceptions varied with alternating exposure to sunlight and shade at different frequencies. UTCI was modified to an equivalent UTCI* for evaluating thermal environments with frequent step changes by taking into account impacts of mixed changes in sun and wind conditions, alternating frequency and expectation on thermal perceptions. With a higher alternating frequency, there was reduced thermal dissatisfaction with hot summer days and a lower comfort requirement for shade, as well as the upper limit of acceptable UTCI* approaching 43.7 °C.

Influence of interface in electrical properties of 3D printed structures.

The aligned bond interfaces resulting from the layer-by-layer nature of material extrusion-based additive manufacturing (MEAM) leads to anisotropic properties in printed parts. This study examines the anisotropy in electrical impedance and its variation with print parameters. Samples consisting of a stack of filaments are used to study the interfaces, which are the fundamental building block of MEAM, in a controlled manner. Anisotropy was quantified using the ratio of the impedance measured across (Z-specimen) and along (F-specimen) the fiber orientation. Although the conductivity of the material was found to change with extrusion temperature, the Z/F ratio was found to be constant (2.15 ± 0.23), regardless of the variation in thermal conditions imposed by varying extrusion temperature and print speed. By varying the distance over which impedance was measured, impedance scaling was understood. The scaling was found to be dependent on the extrusion temperature regardless of the variation of print speed by 266%; ~12.5 Ω per interface for 190 °C while ~6.5 Ω per interface for 230 °C, one-third of which was found to be contributed by fiber. While studying the cause for significant impedance at the interface, scanning electron microscopy study shows absence of airgaps at the interface, and energy dispersion spectroscopy shows absence of oxidation at the interface. The implications of specimen design and characterization proposed here allows for examination of a wide range of print parameters with reduction in material, time, and cost. Thus, by investigating the role of print parameters and scaling of impedance with interfaces, we seek to provide a framework to model and predict electrical behavior of electric sensors and actuators made with MEAM.

Ground Frosts in Poland in the Growing Season

The ongoing climate warming affects, among others, and the variability of thermal conditions in spring and autumn are resulting in earlier dates of the beginning and end of the growing season. The present paper provides detailed characteristics of the phenomenon of ground frosts, addressing the question of whether the risk of frost-related damage in the extending growing season is still present. The assessment of temporal and spatial distribution of ground frosts (5 cm above ground level-AGL) in Poland in the thermal growing season (AT > 5 °C) was conducted on the basis of the results of air temperature measurements at 5 and 200 cm a.g.l. obtained from 52 station of the Institute of Meteorology and Water Management—National Research Institute for the period 1971–2020. The thermal growing season was calculated using the method by Gumiński. The following were calculated: the dates of the occurrence of ground frosts in spring and autumn, duration of the frost-free period, the number of days with frosts of various intensity, according to years, ten-day period and days in a year together with trends of change. The conducted analysis demonstrated that the number of days with frosts in the thermal growing season in the multiannual period under analysis (1971–2020) does not show any statistically significant changes. It was found that in the thermal growing season, the average number of days with ground frosts in Poland amounts to 28 and ranges in spring from 15 to 22, and in autumn from 8 to 12. Most frequently, approx. 49%, slight frosts are recorded, followed by moderate (29%), severe (15%) and very severe (7%). A positive effect of water reservoirs on decreasing the frequency and intensity of frosts, as well as sporadic occurrence of the phenomenon in the second half of June were demonstrated. Statistically significant earlier dates of disappearance of frosts in spring, later dates of occurrence in autumn and the lengthening of the frost-free period from approximately 2 days in the north-east of Poland to approximately 8.0 days over 10 years in the Pomerania region, create increasingly more favourable conditions for the cultivation of plants with high thermal requirements in Poland.

ОКЕАНОЛОГИЧЕСКИЕ УСЛОВИЯ НА ЮГО-ВОСТОЧНОМ ШЕЛЬФЕ О. САХАЛИН ПО ДАННЫМ СЪЕМОК НА СТАНДАРТНЫХ РАЗРЕЗАХ И СПУТНИКОВЫХ НАБЛЮДЕНИЙ

The average monthly temperature and salinity distributions are analyzed for 7 standard sections crossing the area off the southeast coast of Sakhalin Island, built for the navigation period (June-November). The most significant seasonal changes in oceanological conditions occur in the fall, when the modified Amur River water transported by the ESC fills the northern and western parts of the study area, and surface waters are deepened to a depth of 50 m. Interannual variations in thermal conditions were determined by satellite data. In the spring months of 1998–2002 positive anomalies prevailed, and negative in 2011–2018; in summer the temperature of the surface layer is more stable. The spatial distribution of the first EOF mode is identical to the distribution of water temperature in the surface layer according to ship surveys and is characterized by higher values in the northern and western shallow and southeastern deep-sea parts of the study area. In its amplitude, cyclic variations with a period of 6–7 years, expressed in modulation of the annual harmonic, are traced. In the amplitude of the second mode, the climate shift that occurred in 2010 and expressed in a change in its sign from positive to negative is of great interest.

Low snowpack reduces thermal response diversity among streams across a landscape

AbstractSpatial and temporal variation in thermal conditions are important dimensions of aquatic landscapes, yet we do not understand how this heterogeneity will respond to climate change. Snowpack in many regions is declining but impacts on aquatic thermal regimes remain poorly understood. Our analyses of summer stream temperatures across a complex river basin in southwest Alaska show that loss of snowpack has disproportionate effects on water temperatures in streams that are cold under typical conditions, thereby homogenizing stream temperatures across the landscape during low snow conditions. Streams draining steep watersheds warmed from a summer average of 4–8°C between high and low snow years and became more responsive to variation in regional air temperature (as proxy for solar radiation), while streams draining flat watersheds changed negligibly. Our results suggest that conservation strategies for aquatic landscapes that focus on snow‐dominated cold‐water refugia may not be robust to future climate warming and changes in snowpack.

Egg Incubation Temperature Affects Development of Innate Immune Function in Nestling American Robins (Turdus migratorius).

The innate immune system provides important first-line defenses against invading pathogens and is considered especially important for developing organisms. However, we know little about how early-life conditions influence these defenses in wild animals. For oviparous species such as birds, embryonic development occurs in the egg, which can be subject to variation in thermal conditions. There is evidence from cavity-nesting species and species with precocial young that reduced incubation temperatures can result in reduced measures of innate immunity. Whether and how this thermal variation impacts innate immunity for open-cup-nesting species with altricial offspring has not been examined. In this study, we experimentally manipulated egg incubation temperature for American robins (Turdus migratorius) and compared the bacteria-killing ability (BKA) of the nestlings' blood plasma. We collected baseline and poststressor samples on day 7 and day 10 after hatch to gain additional insights into the ontogeny of this immune measure, as well as into whether any changes were linked to levels of the glucocorticoid hormone corticosterone (CORT). We found that nestlings incubated at the low treatment (36.1°C) had significantly reduced BKA compared with nestlings incubated at the high treatment (37.8°C) when controlling for the posthatch nest environment. We also documented a significant reduction in poststressor levels of BKA, as well as an increase in BKA from day 7 to day 10. We found a weak inverse association between CORT and BKA but no other indications that BKA was mediated via treatment-induced variation in CORT. Our results suggest that incubation temperature can affect development of innate immunity in open-cup-nesting passerines.

Climatic Changes in Thermal Conditions of Sea Areas in the Eastern Arctic at the Turn of the 20th and 21st Centuries

The interannual variability of sea surface temperature and air temperature in the coastal zone and adjacent areas of the East Siberian and Chukchi seas and the Arctic Ocean at the modern stage of the climate warming is analyzed. The analysis is based on data of routine observations at hydrometeorological stations obtained in 1980–2016, global meteorological network data and NOAA reanalysis data. The analysis of the spatiotemporal pattern of temperature variations and the zoning of water areas based on the features of modern climate changes are carried out using the EOF (Empirical Orthogonal Functions), cluster, and correlation analyses. The possible cause-effect relationships between these changes and variations in wind field components and climate indices are considered. The studies revealed, specified, and quantified the modern trends and regional features of interannual variability of thermal conditions in the selected areas.

Plasticity in phytoplankton annual periodicity: an adaptation to long-term environmental changes

Because phytoplankton communities exhibit seasonal patterns driven by changes in physical factors, grazing pressure, and nutrient limitations, climate change, in combination with local phosphorus management policies are expected to impact phytoplankton annual dynamic. We used long-term monitoring data from Lake Geneva (from 1974 to 2010) to test if changes in phytoplankton seasonal succession across years is related to re-oligotrophication, inter-annual variability in thermal conditions, and Daphnia sp. density. We used a Bayesian method to identify species assemblages and wavelet analysis to detect transient dynamics in seasonal periodicity. A decrease in phosphorus concentrations appeared to play a major role in the inter-annual replacement of species assemblages. Furthermore, some species assemblages exhibited a change in their seasonal periodicity that was most likely induced by changes in Daphnia sp. density. Finally, we demonstrated that flexibility in the pattern of phytoplankton seasonal successions played a stabilizing role at the community level. The results suggest that phenology and inter-annual changes in seasonal dynamics of phytoplankton assemblages are important components to consider for explaining long-term variability in phytoplankton community.

Microscale mobile monitoring of urban air temperature

BackgroundMobile air temperature monitoring is a promising method to better understand temperature distributions at fine spatial resolutions across urban areas. The study objectives were to collect microscale measurements for evaluate different data sources used to assess heat exposure in greater Vancouver, Canada. MethodsMobile air temperature monitoring was conducted on foot at least twice for each of 20 routes. First, the mobile data were compared with 1-minute measurements from the nearest fixed site. Second, the mobile data from runs corresponding with Landsat overpass days were compared with satellite-derived land surface temperature (LST). Third, the mobile data were compared with estimates from a previously developed heat map for the region. ResultsMobile measurements were typically higher and more variable than simultaneous fixed site measurements. Correlations between mobile measurements and LST were weak and highly variable (r2=0.04–0.38). The z-score differentials between mobile measurements and the heat map suggested that spatial variability in temperatures is captured by the heat map. ConclusionMicroscale measurements confirm that fixed sites do not characterize the variability in thermal conditions within nearby streetscapes. Microscale monitoring of air temperatures is a valuable tool for temporally and spatially evaluating other high resolution temperature data within small areas.

Variability of growing degree days in Poland in response to ongoing climate changes in Europe

An observed increase in air temperature can lead to significant changes in the phenology of plants and, consequently, changes in agricultural production. The aim of the study was to evaluate the spatial differentiation of thermal resources in Poland and their variability during a period of changing thermal conditions in Europe. Since the variability of thermal conditions is of paramount importance for perennial crops, the study focused on apple, plum, and cherry orchard regions in Poland. The analysis was conducted for the period of 1951–2010 using air temperature daily data. Thermal resources have been defined using the growing degree days (GDD) index calculated independently for the whole year and during in frost-free season for three air temperature thresholds: 0, 5, and 10 °C, which determine the non-winter period, growing season, and the period of full plant growth, respectively. In addition, due to the high significance for perennials in particular, the incidence and intensity of frost during flowering were calculated. In this study, a detailed analysis of the spatial differentiation of thermal resources was first performed, followed by an evaluation of long-term variability and associated change patterns. The obtained results confirmed an increase in thermal resources in Poland as a consequence of the lengthening of the growing season. However, the frequency and intensity of spring frost, especially during flowering or even during ripening of plants, remain a threat to harvests in both the eastern and western parts of the country.

A large‐scale latitudinal pattern of life‐history traits in a strictly univoltine damselfly

1. Variation in thermal conditions and season length along latitudinal gradients affect body size‐related traits over different life stages. Selection is expected to optimise these size traits in response to the costs and benefits.2. Egg, hatchling, larval and adult size in males and females were estimated along a latitudinal gradient of 2730 km across Europe in the univoltine damselfly Lestes sponsa, using a combination of field‐collection and laboratory‐rearing experiments. In the laboratory, individuals were grown in temperatures and photoperiod simulating those at the latitude of origin, and in common‐garden conditions.3. The size of adults sampled in nature was negatively correlated with latitude. In all populations the females were larger than the males. Results from simulated and common‐garden rearing experiments supported this pattern of size difference across latitudes and between sexes, suggesting a genetic component for the latitudinal size trend and female‐biased size dimorphism. In contrast, hatchling size showed a positive relationship with latitude, but egg size, although differing between latitudes, showed no such relationship.4. The results support a converse Bergmann cline, i.e. a negative body size cline towards the north. This negative cline in body size is probably driven by progressively stronger seasonal time and temperature constraints towards the higher latitudes and by the obligate univoltine life cycle of L. sponsa. As egg size showed no relationship with latitude, other environmental factors besides temperature, such as desiccation risk, probably affect this trait.