Summer Air Temperature Research Articles

Spatial Configuration of Urban Greenspace Affects Summer Air Temperature: Diurnal Variations and Scale Effects

Optimizing the spatial pattern (spatial compositive and spatial configuration) of urban greenspace can effectively alleviate the urban heat island effect. While the relationship between air temperature (AT) and spatial composition of urban greenspace has been widely studied, this study aimed to investigate the relationship between AT and spatial configuration of urban greenspace and its diurnal variations and scale effects. Based on hourly AT data from 36 meteorological stations in Changsha, China, and land cover data interpreted from the Gaofen 2 remote sensing images, this study first quantified spatial composition (i.e., percent of greenspace) and spatial configuration (i.e., average patch area, patch density, edge density, landscape shape index, and mean shape index) of urban greenspace at different scales (30 m to 2000 m buffer surrounding the air station), then Pearson correlations (between AT and each landscape metric) and partial Pearson correlations (between AT and spatial configuration metrics with percent of greenspace controlled) were analyzed. Multiple linear regression was applied to model the variation of AT using the landscape metrics as independent variables. Finally, the variance partitioning analysis was performed to investigate the relative importance of spatial composition and spatial configuration of urban greenspace to explain the variation of AT. The results showed that (1) the temperature range reached 1.73 °C during the day and 2.94 °C at night. Urban greenspace was fragmented especially at small scales. (2) The Pearson correlation between AT and percent of greenspace fluctuated with the increase of scale and was generally higher during the day than during the night. (3) The spatial pattern of urban greenspace explained as high as 55% of the AT variation, showing diurnal variations and scale effects (i.e., a maximum of 0.54 during the day at 50 m buffer and a maximum of 0.55 during the night at 400 m buffer). (4) A higher percent of greenspace, more aggregated greenspace patches, and simpler greenspace shapes can generate a stronger cooling effect. (5) The relative importance of spatial composition and spatial configuration of greenspace varied among spatial scales and showed diurnal variations. These results emphasize the scale effect as well as diurnal variation of the relationship between urban greenspace spatial pattern and AT. These findings provide theoretical guidance for urban greenspace planning and management to improve the urban thermal environment in rapidly developing subtropical cities such as Changsha, China.

Dynamic simulation and exergy-economic assessment of solar thermal refrigeration systems in different climates

In this paper, the performance of solar-thermal cooling systems for air conditioning application is investigated in different climates of Iran. Diverse climate types are considered which makes the results applicable to other countries. Available commercial refrigeration cycles that are capable of integration with solar-thermal collector systems including the closed liquid absorption cycle, closed solid adsorption cycle, and desiccant cycle are studied. First, a solar and climatic map is proposed and the representative cities have been selected for each climate. Then, the climate parameters related to each region are extracted to create an hourly database. Also, the cooling load of a reference building is modeled based on the climate database, each refrigeration cycle is simulated using thermodynamic equations, and the dynamic model is generalized daily for the hot season in each city. In the last step, each cooling system is examined using an exergy-economic analysis, and technical and economic indicators are compared. The results show that the most suitable solar-thermal refrigeration cycle that can be installed in the central plateau and semi-arid areas of Iran is the closed-cycle liquid absorption system. The annual average exergy-economic factor and the annual solar fraction in this cycle are 0.7578 and 0.57, respectively. In the southern coastal areas, due to the high humidity and air temperature in summer, the solid desiccant refrigeration system with an exergy-economic factor of 0.6978 and a solar fraction of 0.2416 is preferred. The suitable solar-thermal refrigeration cycle in the cold and mountainous regions of Iran is a solid adsorption system with a silica gel absorber. The annual solar fraction and average annual exergy-economic factor in this cycle are 0.5158 and 0.7394. Also, in northern moderate regions, the solid adsorption refrigeration system with an average annual exergy-economic factor of 0.409 and average exergy efficiency of 0.12 is comparatively beneficial.

Comparison of Recently Proposed Causes of Climate Change

This paper compares the ideas contained in the main papers published on climate change since World War II to arrive at a suggested consensus of our present knowledge regarding climatic changes and their causes. Atmospheric carbon dioxide is only suggested as a cause in one theory, which, despite its wide acceptance by Politicians, the media, and the Public, ignores the findings in other studies, including the ideas found in the Milankovitch Cycles. It also does not explain the well-known NASA map of the changes between the global 1951–1978 and the 2010–2019 mean annual temperatures. The other theories by Oceanographers, Earth scientists, and Geographers fit together to indicate that the variations in climate are the result of differential solar heating of the Earth, resulting in a series of processes redistributing the heat to produce a more uniform range of climates around the surface of the Earth. Key factors are the shape of the Earth and the Milankovitch Cycles, the distribution of land and water bodies, the differences between heating land and water, ocean currents and gateways, air masses, and hurricanes. Low atmospheric carbon dioxide levels during cold events could result in too little of this gas to support photosynthesis in plants, resulting in the extermination of most life on Earth as we know it. The 23 ka Milankovitch cycle has begun to reduce the winter insolation received at the surface of the atmosphere in the mid-latitudes of the Northern Hemisphere starting in 2020. This results in extreme weather as the winter insolation reaching the surface of the atmosphere in the higher latitudes of the Northern Hemisphere decreases while the summer air temperatures increase. It heralds the start of the next glaciation. A brief outline is given of some of the climatic changes and consequences that may be expected in western Canada during the next 11.5 ka.

Improving children's outdoor thermal comfort: A field study in China's severely cold regions

This study used meteorological monitoring, subjective thermal perception surveys, and activity records to explore the factors that affect children's outdoor thermal comfort in China's severely cold regions. The Universal Thermal Climate Index (UTCI) was used to determine children's thermal benchmarks and calendar, based on which a strategy to improve thermal comfort was proposed. Results showed (1) significant differences in solar radiation and wind speed, but not in air temperature and relative humidity between different areas. (2) Different Microclimate parameters affected children's thermal perception in different seasons: solar radiation (G) in winter, air temperature (Ta) in summer. (3) Children tolerate the UTCI changes in winter than in summer. (4) Children's neutral UTCI in winter and summer were 9.7 °C and 17.6 °C, respectively, and its ranges were 2.3–17.1 °C and 13.6–21.7 °C, respectively. The thermal acceptability range by 80% of the interviewed children was 2.1–16.3 °C. (5) Based on these results, a thermal comfort improvement on two dimensions—children and the environment—was implemented. This study enriches basic research on children's outdoor thermal comfort and provides a reference for the construction of urban child-friendly spaces.

Summer litter decomposition is moderated by scale‐dependent microenvironmental variation in tundra ecosystems

Tundra soils are one of the world's largest organic carbon stores, yet this carbon is vulnerable to accelerated decomposition as climate warming progresses. The landscape‐scale controls of litter decomposition are poorly understood in tundra ecosystems, which hinders our understanding of the global carbon cycle. We examined the extent to which the thermal sum of surface air temperature, soil moisture and permafrost thaw depth influenced litter mass loss and decomposition rates (k), and at which spatial thresholds an environmental variable becomes a reliable predictor of decomposition, using the Tea Bag Index protocol across a heterogeneous tundra landscape on Qikiqtaruk–Herschel Island, Yukon, Canada. We found greater green tea litter mass loss and faster decomposition rates (k) in wetter areas within the landscape, and to a lesser extent in areas with deeper permafrost active layer thickness and higher surface thermal sums. We also found higher decomposition rates (k) on north‐facing relative to south‐facing aspects at microsites that were wetter rather than warmer. Spatially heterogeneous belowground conditions (soil moisture and active layer depth) explained variation in decomposition metrics at local scales (< 50 m2) better than thermal sum. Surprisingly, there was no strong control of elevation or slope on litter decomposition. Our results reveal that there is considerable scale dependency in the environmental controls of tundra litter decomposition, with moisture playing a greater role than the thermal sum at < 50 m2 scales. Our findings highlight the importance and complexity of microenvironmental controls on litter decomposition in estimates of carbon cycling in a rapidly warming tundra biome.

APPLICATION OF BIG DATA TECHNOLOGIES TO ASSESS THE NATURAL MOISTURE OF THE TERRITORY

Due to the sharp changes in climatic conditions in Western Siberia, the most pressing problem is food security associated with forecasting crop yields. There is a need to estimate the natural wetness of the area on the basis of agroclimatic indicators, among which the sum of active air temperatures and precipitation is currently the most widely used.
 Background. However, for a comprehensive assessment of the wetness of the territory, it is necessary to take into account the climate energy resources associated with evaporation of different time resolutions (day, decades, months, vegetation period, year). The initial meteorological parameters are described in the form of poorly structured information of a large volume. Therefore, various technologies and algorithms of machine processing are used in the work.
 Purpose. The application of big data technologies to assess the natural moisture of the territory
 Materials and methods. With the help of the high-level Python programming language and engineering libraries, a comprehensive assessment of the territory was carried out using the example of Mirny of the Kochenevsky District of the Novosibirsk Region in the context of long-term average data and two years 2019 and 2020. That the use of machine processing technologies related to NoSQL data requests, creation of data set and big data slices allows to store and process meteorological parameters using cloud services of different time resolution. This makes it possible to significantly reduce the time for a comprehensive assessment of the territory according to agroclimatic parameters. As a result of the work, precipitation distribution, temperature, relative air humidity, evaporability, humidification coefficients (Ivanov-Vysotsky and Selyaninov hydrothermal coefficient) were obtained.
 Results. The paper proposes to use technologies of big data processing using Python, including pre-processing of poorly structured hydrometeorological data, execution of NoSQL queries, compilation of summary reports on agroclimatic parameters. Pre-processing consists of processing hourly meteorological data, filling gaps in the data, making slices in big data to process multi-temporal queries (day, month, growing season, year). By the example of Mirny farm in Kochenevsky district of Novosibirsk region (Russian Federation), big data processing was performed to calculate agroclimatic parameters to assess the natural moisture content of the area and yield forecasting.
 Conclusion. The practical significance of the work is as follows:
 - the application of big data processing technologies has significantly reduced the time for the labor-intensive process of assessing agrometeorological parameters;
 - obtained aggregated meteorological parameters of different temporal resolution (hours, days, decades, months) allowed us to identify a strong variability of agroclimatic conditions for the territory of Mirny farm Kochenevsky district, located in the forest-steppe zone of Western Siberia;
 - perform an integral assessment of agroclimatic conditions by calculating the integral indices of moisture, climate continentality, and agroclimatic potential.

Lake Dynamics Modulate the Air Temperature Variability Recorded by Sedimentary Aquatic Biomarkers: A Holocene Case Study From Western Greenland

AbstractQuantitative temperature reconstructions from lacustrine organic geochemical proxies including branched glycerol dialkyl glycerol tetraethers (brGDGTs) and alkenones provide key constraints on past continental climates. However, estimation of air temperatures from proxies can be impacted by non‐stationarity in the relationships between seasonal air and water temperatures, a factor not yet examined in strongly seasonal high‐latitude settings. We pair downcore analyses of brGDGTs and alkenones measured on the same samples through the Holocene with forward‐modeled proxy values based on thermodynamic lake model simulations for a western Greenland lake. The measured brGDGT distributions suggest that stable autochthonous (aquatic) production overpowers allochthonous inputs for most samples, justifying the use of the lake model to interpret temperature‐driven changes. Conventional calibration of alkenones (detected only after 5.5 thousand years BP) suggests substantially larger temperature variations than conventional calibration of brGDGTs. Comparison of proxy measurements to forward‐modeled values suggests variations in brGDGT distributions monotonically reflect multi‐decadal summer air temperatures changes, although the length of the ice‐free season dampens the influence of air temperatures on water temperatures. Drivers of alkenone variability remain less clear; potential influences include small changes in the seasonality of proxy production or biases toward specific years, both underlain by non‐linearity in water‐air temperature sensitivity during relevant seasonal windows. We demonstrate that implied temperature variability can differ substantially between proxies because of differences in air‐water temperature sensitivity during windows of proxy synthesis without necessitating threshold behavior in the lake or local climate, and recommend that future studies incorporate lake modeling to constrain this uncertainty.

Nutrient Flux under the Influence of Melt Water Runoff from Volcanic Territories and Ecosystem Response of Vilyuchinskaya and Avachinskaya Bays in Southeastern Kamchatka

Nutrient fluxes with river runoff can largely determine the state of coastal water ecosystems. The Vilyuchinskaya and Avachinskaya Bays of Kamchatka Peninsula were surveyed on 4–5 July 2022, just after the peak of the spring–summer flood of the Vilyucha and Avacha Rivers associated with the snow melting in volcanic areas. Additionally, water sampling was performed in river water in December 2022, in the period of winter low water. A general undersaturation of CO2 of surface waters was observed in the Vilyuchinskaya and Avachinskaya Bays. Strong supersaturation of CO2 of the near-bottom waters was observed, due to microbial destruction of organic matter, especially in Avachinskaya Bay. This organic matter was formed as a result of photosynthesis in the water column, which subsequently gravitated to the bottom and concentrated in specific bottom depressions in the studied bays. In these depressions, black sediments were found, in which sulfate reduction occurred. The porewater of sediments had a very high concentration of organic carbon, dissolved and organic nitrogen, and phosphates, as well as CO2 partial pressure. The source of nutrients for the studied bays is tephra (volcanic suspended particles), which covers all the watersheds, including the soil and snow, as a result of volcanic activity in the study region. Based on the calculated nutrient fluxes in river runoff for the summer and winter seasons and the DIN/DIP ratios in river, sea, and pore waters, the causes of phytoplankton blooms, including the occurrence of red tides, are discussed. The maximum flux of nutrients and, accordingly, phytoplankton blooms should be expected in the years with the highest volcanic activity and high summer air temperatures, since the melting of nutrient-rich snow and ice will be maximum. This will determine the flux of nutrients in the river runoff of the Kamchatka Peninsula and contribute to phytoplankton blooms.

Trees on the tundra: warmer climate might not favor prostrate Larix tree but Betula nana shrub growth in Siberian tundra (Lena River Delta)

Tundra is primarily a habitat for shrub growth, not trees, but growth of prostrate forms of trees has been reported occasionally from the subarctic tundra region. In the light of on-going climate change, climate sensitivity studies of these unique trees are essential to predict vegetation dynamics and potential northward expansion of boreal forest tree species into tundra. Here we studied one of the northernmost Larix Mill. trees and Betula nana L. shrubs (72°N) from the Siberian tundra for the common period 1980-2017. We took advantage of the discovery of a single cohort of prostrate Larix trees within a tundra ecosystem, i.e., ca. 60 km northwards from the northern treeline, and compared climate-growth relationships of the two species. Both woody plants were sensitive to the July temperature, however this relationship was stable across the entire study period (1980-2017) only for Betula nana chronology. Additionally, radial growth of Larix trees became negatively correlated to temperatures during the previous summer. In recent period moisture sensitivity between Larix trees and Betula nana shrubs was contrasting, with generally wetter soil conditions favoring Larix trees growth and dryer conditions promoting Betula nana growth. Our study indicates that Larix trees radial growth in recent years is more sensitive to moisture than to summer air temperatures, whereas temperature sensitivity of Betula nana shrub is stable over time. We provide first detailed insight into the annual resolution on Larix tree growth sensitivity to climate in the heart of the tundra. The potentially higher Betula nana shrub resistance to warmer and drier climate versus Larix trees on a tundra revealed in our study needs to be further examined across habitats of various soil, moisture and permafrost status.

Low sensitivity of net primary productivity to climatic factors in three karst provinces in southwest China from 1981 to 2019

Karst areas are sensitive to environmental changes due to their fragile ecological environments. It is imperative to explore the temporal and spatial variations in the characteristics of vegetation net primary productivity (NPP) and evaluate the influence of different driving factors on NPP. Taking three karst provinces in southwest China as the study area, where the historical vegetation changes and the mechanisms influencing these changes remain unclear; therefore, the present study used vegetation NPP data from 1981 to 2019 to analyze the temporal and spatial variations in the characteristics of vegetation NPP using slope trend analyses and the sequential Mann-Kendall test. The influence of each driving factor on vegetation NPP and the interaction between each driving factor were investigated using the optimal parameters-based geographic detector (OPGD) model. The results were as follows: (1) The annual variation of the total NPP in the study area from 1981 to 2019 showed a fluctuating growth trend, with a slow growth rate before 2005 followed by a rapid increase. (2) The annual fluctuations in the seasonal NPP in the study area were generally upward, and the total NPP of vegetation in summer was the highest, but the growth rate of NPP in autumn was the fastest, and the area with the largest increase in NPP in autumn was the largest. (3) NPP was related to natural factors, with slope being the primary influencing factor at the annual scale. However, at the seasonal scale, there were differences in the explanatory power of the influencing factors on vegetation NPP. The highest explanatory power was observed for surface soil moisture in spring, air temperature in summer, and precipitation in autumn and winter. (4) The spatiotemporal evolution of NPP characteristics was affected by the interaction among various natural factors. At the annual and seasonal scales, the interaction between each climatic factor and slope greatly enhanced the explanatory power of individual climatic factors. Taken together, the interaction between slope and precipitation contributes the most to NPP.

Temperature Effects on Recruitment and Individual Growth of Two Antagonistic Fish Species, Perch Perca fluviatilis and Roach Rutilus rutilus, from a Climate Change Perspective

Perch (Perca fluviatilis) in four boreal lakes and sympatric roach (Rutilis rutilis) in two of these lakes were studied by means of gill net sampling, and age and growth were analyzed to explore whether summer temperature affects recruitment and individual growth of the two species differently. Water temperature logging in the lakes showed a highly significant correlation with air temperature. Year-class strength of the perch was significantly positively affected by the summer air temperature, whereas the temperature effect was non-significant for the roach. There was a significant negative effect of year-class strength of one-year-old perch on roach year-class strength in one lake. ln one of the allopatric perch populations, the year-class strength correlation with temperature failed after biomass removal, probably because fishing affected the age structure. July–August air temperature had a significantly positive effect on individual growth rates of two- to five-year-old perch, whereas the effect on roach growth was less clear. The inclination of perch to predate its competitor, roach, as well as conspecifics, as well as accelerated individual growth, were shown to occur more frequently in years with abundant 1+ perch, i.e., the summer after the rise of a strong year-class. Climate warming may potentially favor perch recruitment and growth.

A multi-year study of ecosystem production and its relation to biophysical factors over a temperate peatland

Peatlands are among the largest stocks of soil carbon, which can be stored for thousands of years under well-wetted conditions. The main goals of the study were to assess annual and seasonal CO2 balances of a temperate peatland and the main biophysical factors affecting these CO2 fluxes. The studied peatland was usually a CO2 sink with a mean annual net ecosystem production (NEP) of 110±83 gCO2-C·m−2·yr−1 and extreme balances in 2006 (-17 gCO2-C·m−2·yr−1) and 2011 (194 gCO2-C·m−2·yr−1). Annual fluxes were not significantly correlated with biophysical variables, unlike seasonal data. Furthermore, the average air temperature in spring and summer was related to NEP at r2=0.65 and r2=0.61, respectively (warmer spring increased NEP while hot summer decreased NEP in these seasons). A decrease in daytime measured NEP during the summer period (June-August) was observed when TA exceeded 25 °C or VPD was above 15 hPa, respectively, due to the growing Reco and possibly plant photorespiration. These findings suggest a negative impact of ongoing global warming on temperate peatland CO2 balances.

Drivers of Forested Riparian Microclimate on the Olympic Peninsula of Washington State

Riparian zones have unique microclimates that support distinct assemblages of aquatic and terrestrial species, which in recent decades have resulted in a regulatory emphasis on riparian protections. However, an understanding of the drivers of riparian microclimate is still lacking. This study examined drivers of variability in summer air temperature and vapor pressure deficit in the riparian zones of 10 drainage basins (31 to 789 ha) on the western Olympic Peninsula, Washington. Model selection analysis was used to explore hypotheses about the influences of 3 types of drivers on microclimate: regional climate gradients, proximity to stream, and solar radiation. Proximity to stream had the strongest influence on microclimate; the air became warmer and drier with increasing distance from the stream and with increasing steepness of the stream valley slope. Basins at lower elevations (range = 28 to 362 m) had cooler, more humid microclimates, a pattern attributed to marine influence. Variation in microclimate was also associated with variation in solar exposure, modeled as a function of topography. Testing of canopy closure influence on microclimate was hindered by uniformly high canopy closure across the study area (87 to 98%) as a result of unmanaged, primarily second-growth stream buffers. Each of the microclimate drivers identified in this study was a function of topography, across a range of scales. By understanding these relationships between topographic variation and riparian microclimate, managers and researchers will be able to more accurately and efficiently delineate the extent of riparian microclimate influence.

Characteristics of Surface “Melt Potential” over Antarctic Ice Shelves based on Regional Atmospheric Model Simulations of Summer Air Temperature Extremes from 1979/80 to 2018/19

Abstract We calculate a regional surface “melt potential” index (MPI) over Antarctic ice shelves that describes the frequency (MPI-freq; %) and intensity (MPI-int; K) of daily maximum summer temperatures exceeding a melt threshold of 273.15 K. This is used to determine which ice shelves are vulnerable to melt-induced hydrofracture and is calculated using near-surface temperature output for each summer from 1979/80 to 2018/19 from two high-resolution regional atmospheric model hindcasts (using the MetUM and HIRHAM5). MPI is highest for Antarctic Peninsula ice shelves (MPI-freq 23%–35%, MPI-int 1.2–2.1 K), lowest (2%–3%, <0 K) for the Ronne–Filchner and Ross ice shelves, and around 10%–24% and 0.6–1.7 K for the other West and East Antarctic ice shelves. Hotspots of MPI are apparent over many ice shelves, and they also show a decreasing trend in MPI-freq. The regional circulation patterns associated with high MPI values over West and East Antarctic ice shelves are remarkably consistent for their respective region but tied to different large-scale climate forcings. The West Antarctic circulation resembles the central Pacific El Niño pattern with a stationary Rossby wave and a strong anticyclone over the high-latitude South Pacific. By contrast, the East Antarctic circulation comprises a zonally symmetric negative Southern Annular Mode pattern with a strong regional anticyclone on the plateau and enhanced coastal easterlies/weakened Southern Ocean westerlies. Values of MPI are 3–4 times larger for a lower temperature/melt threshold of 271.15 K used in a sensitivity test, as melting can occur at temperatures lower than 273.15 K depending on snowpack properties.

The effects of environmental and biological factors on the length of Atlantic Salmon age‐1+ parr in three Maine drainages

AbstractObjectiveAtlantic Salmon Salmo salar in the United States have been the focus of recovery efforts for over 150 years, but long‐term analyses of juvenile demographics are limited. We examined how parr size (fork length [FL]) varied across three Maine drainages (East Machias, Narraguagus, and Sheepscot rivers) during 1980–2014 and was affected by habitat and biological variables using a long‐term electrofishing data set.MethodsWe fitted generalized additive mixed models (GAMMs) to determine how parr FL varied with explanatory variables, including mean summer air temperature, elevation, mean channel width, juvenile salmon density, age‐0 parr stocked, a metric for the number of effective fry stocked, and year. When examining model‐averaged GAMM results, we found that parr size varied throughout the 34‐year time period across the three drainages.ResultBetween 1980 and 2014, parr FL in the Sheepscot River drainage (mean = 143.9 mm) steadily increased (~5‐mm increase). Parr FL in the Narraguagus River drainage (mean = 124.4 mm) declined from 1980 to about 2005 and then increased from 2006 to 2014. Parr FL in the East Machias River drainage (mean = 127.7 mm) experienced a decrease of approximately 10 mm during the study period. Density dependence was evident across drainages, suggesting that habitats were at capacity or that parr were experiencing competition. Given that the production of parr in Maine is highly reliant on stock enhancement, localized high stocking densities may limit parr growth without further restoration or habitat improvements. Stocking intensities generally decreased in all three drainages after 2000, possibly relaxing density dependence and partially explaining the plateau or increase in FL during recent years in the Sheepscot and Narraguagus rivers. Relationships between FL and summer air temperature were drainage specific, while wide channels and lower elevations were consistently associated with larger parr.ConclusionGiven our results, management should continue to prioritize habitat improvements to improve local carrying capacity and potentially reduce density‐dependent growth so as to increase stock enhancement efficacy within an adaptive management framework at the southern edge of the Atlantic Salmon's range.

Glaciers Variation at ‘Shocking’ Pace in the Northeastern Margin of Tibetan Plateau from 1957 to 21st Century: A Case Study of Qiyi Glacier

Accelerating glacier shrinkage is one of the most consequential of global warming. Yet, projections for the region remain ambiguous because of the tremendous spatial heterogeneity, especially in the Qilian Mountains, where glacier melt runoff is a vital water resource for the arid downstream area. To better understand glacier changes in this region, this study took regional representative Qiyi Glacier as an example and applied an enhanced distributed surface mass balance (SMB) model to glimpse the SMB variation and possible impacts on melt runoff under the RCP 4.5 and RCP 8.5 scenarios. Further, we combined a modified volume-scaling method to update the glacier geometry gradually to enhance long-term reliability. When forced with observed daily temperature and precipitation, the reconstructed glacier SMB, from 1957 through 2013, agrees well with the in situ observations. The result indicates an abrupt change for SMB from positive to negative in 1992 and subsequent mass accelerated loss after 2000. The increased summer air temperature and the pattern of large-scale atmospheric circulation shifts might both cause these changes. Using projected climate forcing from as many as 31 coupled GCMs from the CMIP 5 ensemble, the Qiyi Glacier is projected to undergo sustained SMB loss throughout the 21st century for both RCPs. By 2100, the Qiyi Glacier will lose ~25 m water equivalent (w.e.) for RCP 4.5 and ~37 m w.e. for RCP 8.5. Whereas the glacier area will shrink by 43% for RCP 4.5 and 54% for RCP 8.5 relative to 2013 glacier content, corresponding to the volume of the Qiyi Glacier will lose by 54% for RCP 4.5 and by 65% for RCP 8.5, accordingly. Simultaneously, the glacier terminus will experience extreme melts. The terminus elevation of the Qiyi Glacier will retreat from 4310 m a.s.l. in 2013 to 4810 m a.s.l. (RCP 4.5) and 4838 m a.s.l. (RCP 8.5) by the end of 2100, which will exceed the multi-year average ELA (4749 m) from 1957 to 2013. If the warming trends keep and glaciers melt like the Qiyi Glacier with this ‘shocking’ rate, it will raise the possibility of crippling, long-term water shortages for Hexi corridors.

Relationship between Holocene lake water temperature and glacier meltwater on the northwestern Tibetan Plateau

Understanding the relationship between glacier meltwater and lake water temperature changes on the Tibetan Plateau (TP) is important for water resources management, environmental protection, and geological risk analysis. Summer temperature is one of the main factors affecting glacier evolution, yet we lack summer temperature records for high-altitude regions where glaciers are widely developed. In this study, we established a calibration between TEX86, which measures the abundance of aquatic isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) of Group I.1a aquatic Thaumarchaeota, and mean annual lake water temperature (MLWT) for 17 surface sediment samples from 10 lakes on the TP (MLWT = 4.1× TEX86 + 2.6 °C, R2 = 0.77). Given that lakes freeze during the cold season, MLWT is a record of the warm season temperature, especially the summer-biased temperature. We applied this calibration to reconstruct a Holocene MLWT record for Bangdag Co, a high-altitude hydrologically-closed lake (4909 m a.s.l.) on the northwestern TP, where glaciers are widely developed. The record shows low temperatures during the early Holocene, high temperatures during the middle Holocene, and a cooling trend during the middle to late Holocene. The MLWT is negatively correlated with the glacial meltwater volume during the early Holocene, indicating a large glacial meltwater influx to the lake at this time which resulted in low lake-water temperatures. Following the decrease in summer insolation during the middle to late Holocene, summer temperatures decreased and thus glacier meltwater production decreased. The MLWT shows a significant positive correlation with the glacial meltwater volume during the middle to late Holocene, which indicates that glacier meltwater barely influenced the MLWT, which was mainly controlled by the summer air temperature. Overall, when the air temperature decreased, the MLWT was low and the glacier meltwater production decreased. Our MLWT record for Bangdag Co agrees well with the cooling trend evident in summer temperature records and model simulations for the TP during the middle to late Holocene, which can be primarily attributed to decreasing summer insolation.

Hardwoods influence effect of climate and intraspecific competition on growth of woodland longleaf pine trees

AbstractLongleaf pine woodlands of the North American Coastal Plain are proposed to be resilient to climate change impacts, but little is known about changes in limiting factors to longleaf pine growth as climate has changed in late 20th century and early 21st century. Moreover, the role that neighborhood trees play in the context of climate change remains largely unexplored. We used static and moving window tree ring and climatic analyses to measure the effects of climate on longleaf pine growth at a site in southwest Georgia, USA. We then performed maximum likelihood analysis to examine the influence of neighboring hardwoods on the response of longleaf pine growth to the joint effects of competition and climate. Analysis of climate data from local stations in southwest Georgia over six decades indicated that mean air temperature decreased until the late 20th century then began to rise, and that the variability of spring and summer precipitation has increased. Tree ring and climate analyses indicated longleaf pine radial growth is sensitive to precipitation and air temperature, and that the strength of correlation of longleaf pine growth to summer air temperature and summer precipitation increased since the 1950s. Likelihood models, which were applied over a shorter (23‐year) period and explicitly incorporated competition, did not support a link between summer temperature and growth but did indicate summer precipitation increased growth. Furthermore, basal area (BA) of neighboring hardwoods was correlated with greater pine growth per millimeter of precipitation. BA of neighboring longleaf pine negatively affected growth of conspecific trees; the presence of hardwoods increased the competitive effect when BA of neighboring pine trees was low (<10 m2 ha−1) but decreased the competitive effect when BA of neighboring pine trees was high (≥10 m2 ha−1). These results suggest that retention or recruitment of hardwood trees when restoring longleaf pine woodlands may contribute to increased ability to withstand dry summers and may help to allay concerns of managers that retention of hardwoods will unduly affect growth of residual mature longleaf pines.

Deepened snow in combination with summer warming increases growing season nitrous oxide emissions in dry tundra, but not in wet tundra

Impacts of increased winter snowfall and warmer summer air temperatures on nitrous oxide (N2O) dynamics in arctic tundra are uncertain. Here we evaluate surface N2O dynamics in both wet and dry tundra in West Greenland, subjected to field manipulations with deepened winter snow and summer warming. The potential denitrification activity (PDA) and potential net N2O production (N2Onet) were measured to assess denitrification and N2O consumption potential. The surface N2O fluxes averaged 0.49 ± 0.42 and 2.6 ± 0.84 μg N2O–N m−2 h−1, and total emissions were 212 ± 151 and 114 ± 63 g N2O–N scaled to the entire study area of 0.15 km2, at the dry and wet tundra, respectively. The experimental summer warming, and in combination with deepened snow, significantly increased N2O emissions at the dry tundra, but not at the wet tundra. The deepened snow increased winter soil temperatures and growing season soil N availability (DON, NH4+-N or NO3−-N), but no main effect of deepened snow on N2O fluxes was found at either tundra ecosystem. The mean PDA was 5- and 121-fold higher than the N2Onet at the dry and wet tundra, respectively, suggesting that N2O might be reduced and emitted as dinitrogen (N2). Overall, this study reveals modest but evident surface N2O fluxes from tundra ecosystems in Western Greenland, and suggests that projected increases in winter precipitation and summer air temperatures may increase N2O emissions, particularly at the dry tundra dominating in this region.

Infl uence of ecological factors on the start date of the colorado potato beetle lLeptinotarsa decemlineata (Say) (Coleoptera, Chrysomelidae) emergence from overwintering sites in the Central forest-steppe priobskii agro-landscape region

As a result of long-term studies, the complex e ect of the depth of soil freezing, depth of snow cover, the amount of precipitation, the temperature of air and of soil at a depth of 0-20 and 20-40 cm, the sum of e ective temperatures on the start date of the adult Leptinotarsa decemlineata (Say) emergence from the soil in potato plantings was established in the Central Forest-Steppe Priobskii Agro-Landscape Region. The average values of these environmental factors for the period from September of the previous year to June of the current year by 27.2% determined the emergence date of the overwintered imago. The share of the conditions of the previous year in uence was 50.5, and the conditions of the current year, 31.1%. The appearance of the overwintered adults was delayed when they had gone for overwintering in moist and cool soil. In November, the emergence date begins to be a ected by the depth of snow cover and the depth of soil freezing (the in uence shares 86.8 and 79.5%, respectively), and their e ect together with the factors listed accounted for 35.3%. In December, the same trend was observed, but the air temperature was not considered. In January, the importance of the parameter of the soil temperature increased to 84.3%, and that of the complex of factors in 26.7% of cases. In February, the same trend was observed, and the share of the in uence all previously listed factors increased to 43.0%. From March, the impact of the depth of soil freezing and the depth of snow has decreased to 42.3%, and from April, the sum of rain precipitation and air temperature began to in uence in 81.8 and 65.8% of cases, respectively. In May, the start date of the pest appearance is a ected only by the soil temperature at a depth of 0-20 and 20-40 cm - 80.7 and 94.0%, respectively, and by photoperiod - 91.1%. In June, the main factors were the amount of rain precipitation and the soil temperature - 100%, while the impact of accumulated SET was 50.0%. Thus, in this region, on average, the beginning of the adults’ Exit from the soil starts on June 17 ± 12 days, when the average daily air temperature reaches +19.1 ± 5.8 °C, the sum of rain precipitation (at air temperature > 10 °C) - 70.7 ± 39.1 mm, and the soil at a depth of 0-20 and 20-40 cm warms up to +17.6 ± 3.8 °C and +14.8 ± 2.5 °C, respectively. The SET in this period is 149.0 ± 64.1 degree days.