Air Temperature Trends Research Articles

Alaska Terrestrial and Marine Climate Trends, 1957–2021

Abstract Some of the largest climatic changes in the Arctic have been observed in Alaska and the surrounding marginal seas. Near-surface air temperature (T2m), precipitation (P), snowfall, and sea ice changes have been previously documented, often in disparate studies. Here, we provide an updated, long-term trend analysis (1957–2021; n = 65 years) of such parameters in ERA5, NOAA U.S. Climate Gridded Dataset (NClimGrid), NOAA National Centers for Environmental Information (NCEI) Alaska climate division, and composite sea ice products preceding the upcoming Fifth National Climate Assessment (NCA5) and other near-future climate reports. In the past half century, annual T2m has broadly increased across Alaska, and during winter, spring, and autumn on the North Slope and North Panhandle (T2m > 0.50°C decade−1). Precipitation has also increased across climate divisions and appears strongly interrelated with temperature–sea ice feedbacks on the North Slope, specifically with increased (decreased) open water (sea ice extent). Snowfall equivalent (SFE) has decreased in autumn and spring, perhaps aligned with a regime transition of snow to rain, while winter SFE has broadly increased across the state. Sea ice decline and melt-season lengthening also have a pronounced signal around Alaska, with the largest trends in these parameters found in the Beaufort Sea. Alaska’s climatic changes are also placed in context against regional and contiguous U.S. air temperature trends and show ∼50% greater warming in Alaska relative to the lower-48 states. Alaska T2m increases also exceed those of any contiguous U.S. subregion, positioning Alaska at the forefront of U.S. climate warming. Significance Statement This study produces an updated, long-term trend analysis (1957–2021) of key Alaska climate parameters, including air temperature, precipitation (including snowfall equivalent), and sea ice, to inform upcoming climate assessment reports, including the Fifth National Climate Assessment (NCA5) scheduled for publication in 2023. Key findings include widespread annual and seasonal warming with increased precipitation across much of the state. Winter snowfall has broadly increased, but spring and autumn snowfalls have decreased as rainfall increased. Autumn warming and precipitation increases over the North Slope, in particular, appear related to decreased sea ice coverage in the Beaufort Sea and Chukchi Seas. These trends may result from interrelated processes that accelerate Alaska climate changes relative to those of the contiguous United States.

Attributing the drivers of runoff decline in the Thaya river basin

Study Region:The Thaya river basin provides multiple water uses in the transboundary region of Lower Austria and Southern Moravia. Due to the low precipitation (P) to reference evapotranspiration (ETo) ratio, the Thaya river basin is among the most sensitive to climate change in the region. Study Focus:The main objective is to understand the changes in the water balance variables including actual evapotranspiration (ET), P and runoff (RO) and their drivers for the period 1981–2020, and 2001–2020 in the case of using remote sensing data. New Hydrological Insights for the Region:The analyses confirm previously reported increasing trends in air temperature, ETo, and no trends in P. ET consistently increased during spring and decreased during summer, although insignificantly. This change was associated with a significant increase of spring vegetation development followed by summer stagnation. The spring RO shows significantly decreasing trends, especially in the upland water source areas. The correlation analysis reveals a different behavior along the altitude gradient, with ET in the uplands generally limited by available energy whilst in the lowlands by available water in spring. In summer, however, the entire basin is often water-limited, with a more pronounced limitation in the lowlands. Complex adaptation measures reflecting the different hydroclimate relations across the altitudinal gradient are needed to sustain the water dependent sectors operating in the region facing increasing aridity.

Diversity and Variability of the Course of Ice Phenomena on the Lakes Located in the Southern and Eastern Part of the Baltic Sea Catchment Area

The aim of the study is to determine the scale of differentiation and variability of ice phenomena on the lakes in the south-eastern part of the Baltic Sea catchment area. The analysis was performed based on data from the period 1961–2020 from 15 lakes located in Poland (10) and Belarus (5). The characteristics of ice phenomena were characterized, i.e., the length of their occurrence and ice cover, the thickness of ice cover and the number of breaks occurring in the ice cover in the given years were characterized. The analysis of the course of ice phenomena made it possible to distinguish three regions with an increasing length of ice phenomenon occurrence from west to east. The zones were the west of the Vistula, the east of it and the eastern part of the Belarusian Lake District. In the analyzed multi-year period, a shortening of the duration of ice phenomena and ice cover, a decrease in the maximum thickness of the ice and an increasing number of breaks in ice cover were observed. These data correlate with the upward trend in air temperature.

Assessment of Temperature, Precipitation, and Snow Cover at Different Altitudes of the Varzob River Basin in Tajikistan

The analysis of precipitation, snow cover, and temperature based on measured data is important for many applications in hydrology, meteorology, climatology, disaster management, and human activities. In this study, we used long-term historical datasets from the Varzob River Basin (VRB) in Tajikistan to evaluate the trend and magnitudinal changes in temperature, precipitation, and snow cover area in the Anzob (upstream), Maykhura (midstream), and Hushyori (downstream) regions of the VRB using the original Mann–Kendall test, modified Mann–Kendall test, Sen’s slope test, and Pettitt test. The results revealed a decreasing trend in the mean monthly air temperature at Anzob station in the upstream region for all months except January, February, and December between 1960 and 2018 and 1991 to 2018. In each of the three regions, the mean annual temperature indicated a clear upward trend. Seasonal precipitation indicated a large increasing trend in January and February at the Anzob station from 1960 to 2018, but a significant downward trend in April in the upstream, midstream, and downstream regions between 1960 and 1990 and from 1991 to and 2018. In the VRB, almost all stations exhibited a downward trend in annual precipitation across all periods, whereas the upstream region showed a non-significant upward trend between 1960 and 1990. The monthly analysis of snow cover in the VRB based on ground data showed that the maximum increase in snow cover occurs in April at the Anzob station (178 cm) and in March at Maykhura (138 cm) and Hushyori stations (54 cm). The Mann–Kendall test, based on MODIS data, revealed that the monthly snow cover in the VRB increased in April and July while a decrease was recorded in February, September, November, and December from 2001 to 2022. The trend’s stable pattern was observed in March, May, August, and October.

Seasonal and regional contrasts of future trends in interannual arctic climate variability

Future changes in interannual variability (IAV) of Arctic climate indicators such as sea ice and precipitation are still fairly uncertain. Alongside global warming-induced changes in means, a thorough understanding of IAV is needed to more accurately predict sea ice variability, distinguish trends and natural variability, as well as to reduce uncertainty around the likelihood of extreme events. In this study we rank and select CMIP6 models based on their ability to replicate observations, and quantify simulated IAV trends (1981–2100) of Arctic surface air temperature, evaporation, precipitation, and sea ice concentration under continued global warming. We argue that calculating IAV on grid points before area-averaging allows for a more realistic picture of Arctic-wide changes. Large model ensembles suggest that on shorter time scales (30 years), IAV of all variables is strongly dominated by natural variability (e.g. 93% for sea ice area in March). Long-term trends of IAV are more robust, and reveal strong seasonal and regional differences in their magnitude or even sign. For example, IAV of surface temperature increases in the Central Arctic, but decreases in lower latitudes. Arctic precipitation variability increases more in summer than in winter; especially over land, where in the future it will dominantly fall as rain. Our results emphasize the need to address such seasonal and regional differences when portraying future trends of Arctic climate variability.

Performance analysis on the concentrated photovoltaic /thermal air collector with phase change material and vacuum double-glazing for temperature regulation

Although photovoltaic/thermal (PV/T) air collector has simple structure and strong pressure bearing capacity, there are problems such as low thermal efficiency, unstable output temperature, due to low heat transfer performance of air and fluctuating solar irradiation. To address the above issues, a concentrating photovoltaic/thermal air collector with phase change material and vacuum double-glazing (VDG-PCM-CPV/T) is proposed in this paper. The performance of VDG-PCM-CPV/T in three continuous days is studied and compared with the module with PCM and single-glazing (SG-PCM-CPV/T) and the module with single-glazing (SG-CPV/T) by establishing the mathematic model of the daytime and night. It is proven that VDG-PCM-CPV/T has certain advantages in alleviating the downward trend of air temperature caused by the decrease of solar irradiation, due to the constant temperature storage and heat release characteristics of PCM. At night, as the vacuum double-glazing has excellent heat preservation effect, the initial temperature of PCM in VDG-PCM-CPV/T is 5.00 °C higher than that of SG-PCM-CPV/T, enable VDG-PCM-CPV/T to obtain higher thermal efficiency in the next day. While, the electrical power of VDG-PCM-CPV/T is slightly lower than that of SG-PCM-CPV/T and SG-CPV/T. The exergy efficiency of VDG- PCM-CPV/T, SG-PCM-CPV/T and SG-CPV/T at peak is 1.70%, 1.10% and 2.00%, respectively.

Rethinking spatiotemporal variations in air temperature over the Qilian Mountains, Western China, from 1979 to 2018

The Qilian Mountains region, located on the northeastern Tibetan Plateau, is a region in western China that is sensitive to climate change and serves as an important ecological security barrier. Previous studies mostly used meteorological stations to study climate change in the Qilian Mountains; however, due to the known distribution limitations (scarcity and inhomogeneity) of meteorological stations in mountainous areas, relevant results remain inconclusive. To address this issue, we used 30 meteorological stations in and around the Qilian Mountains and the China meteorological forcing dataset (CMFD) with a spatial resolution of 0.1° × 0.1° to comprehensively analyse the spatiotemporal distribution of and variation in the air temperature over the Qilian Mountains, with a particular focus on elevation-dependent warming (EDW); then, land surface albedo data from the ERA5-Land and MODIS products were employed to interpret the EDW. The results showed that the annual mean lapse rate in the Qilian Mountains is −0.56 °C/100 m. From 1979 to 2018, the air temperature over the Qilian Mountains experienced a significant upwards trend with an annual mean rate of 0.39 °C/decade, the maximum rate occurring in December–February (DJF, 0.56 °C/decade) and the minimum rate occurring in June–August (JJA, 0.28 °C/decade). Spatially, significant warming was found in most areas of the Qilian Mountains, and a slight cooling trend was found in the north and southeast. Unlike other typical areas, the Qilian Mountains showed reversed EDW during 1979–2018, i.e., the increasing trends in air temperature decreased with elevation, which was mainly caused by the reversal in EDW over the 1999–2008 period and could be largely explained by the change in land surface albedo.

Study on winter thermal environmental characteristics of the atrium space of teaching building in China's cold region

The thermal environment of atrium space is complex and its formation mechanism is special. The scientific evaluation of atrium space can help guide the development of appropriate ventilation and heating modes, reducing energy consumption and improving thermal comfort. Through field measurement and questionnaire, the indoor thermal environment and its un-uniform characteristics of the atrium space in winter, as well as the user's behavior habits and subjective thermal feeling are systematically analyzed. Statistical regression analysis method is used to fit and evaluate factors such as operative temperature and thermal comfort, quantitatively reveals the thermal environment needs of atrium users. The study demonstrate that the predicted thermal sensation vote is slightly cold, and the measured thermal neutral temperature of the occupants is lower than the predicted thermal neutral temperature. Furthermore, this study demonstrates the distribution of air temperature in horizontal direction and its influencing factors; in addition, reveals the trend of air temperature with time and height and establishes a fitting equation between air temperature and elevation. The data obtained in this study can provide valuable reference for the construction and operation of college atrium space in cold regions.

Increasing Risk of Spring Frost Occurrence during the Cherry Tree Flowering in Times of Climate Change

Climate change affects the agroecological conditions and persistence of cherry tree flowering. Detailed evaluation of minimum air temperature and occurrence of synoptic events occurrence during spring frosts within the cherry tree flowering in the Czech Republic (Central Europe) is missing. The main objective of this study was to evaluate the above-mentioned variables during the cherry tree flowering in different parts of the country from 1924 to 2012. Our question was how the frequency of frost days occurrence changed during the cherry tree flowering. A trend analysis was conducted with the Mann-Kendall test. The onset of the beginning of flowering and end of flowering shifted to an earlier date per the whole examined period (up to −13.9 and −8.1 days) and the period of flowering extended (up to 4.1 days). The shifts were more pronounced at higher elevations. During the period of the cherry tree flowering, the trend in change of the number of frost days was negative at the lowland station (−0.3 day) and positive at the highland station (+1.2 day). At all stations, “Ap3” synoptic event (anticyclone) occurrence during cherry tree flowering on days with the highest spring frost risk (Tmin at 2 m < −1.1 °C) prevailed. The positive trend of frost-day occurrence and the negative trend of minimum air temperature in cherry tree flowering indicate that blossoms are more endangered at higher elevations.

Trend Analysis of Selected Hydroclimatic Variables for the Hornad Catchment (Slovakia)

This study examines the trends in air temperature, precipitation and flow rates over a 50-year observation period (1961–2010) and compares two periods, 1961–1985 and 1986–2010. The research was carried out in terms of annual and monthly values. The research area is the Hornad River in Slovakia. The main aim of the study was to examine the evolution of precipitation, air temperature and flows in the Hornad River catchment area, as well as to identify the regions (sub-catchments) most vulnerable to climate change. Increasing trends in air temperature in the years 1961–2010 were found to be statistically significant (the Sen’s slope was between 0.0197 and 0.0239). On the other hand, a statistically significant downward trend in flows was recorded only at the Stratená station (a small mountain catchment, where the Sen’s slope was −0.0063). The remaining upward and downward trends were not statistically significant. Greater differences in the course of the trends were recorded on a monthly basis in individual multi-years. Increasing trends in air temperature were statistically significant from May to August in the period 1961–2010. No trends in precipitation were recorded in the period 1961–2010, and only an upward trend in precipitation was recorded in June from 1986–2010.

Climatology and significant trends in air temperature in Alagoas, Northeast Brazil

Climatology and significant trends in air temperature in Alagoas, Northeast Brazil

Influence of variability of climatic indicators onwater consumption of cotton

Processing and analysing average annual climatic parameters over 89 years revealed some trends in air temperature, relative air humidity, and precipitation in the typical grey soils (sierozem) region. These trends demonstrate sustained growth of the climatic indices. However, evaporation rates, deficit indices, and their movements, calculated and performed based on the above climatic parameters, have been decreasing with time. Over the recent years, such a downward tendency in climate elements change has reduced irrigation water requirements of early-ripening cotton plants. The article performs experimental data on evaporation rates measured using small-diameter evaporation pans about watertemperature and wind speed. In the region with typical grey soilsover quite a long observation period, significant changes in climatic elements have occurred, which have had a substantial impact on irrigation schedules and total water consumption of crops; these changes are the following: the rise of annual average air temperature by one degree, relative air humidity – by 25%, precipitation – by 40%.

The effects of biophysical and anthropogenic factors on the recent upper forest‐cover upward shift in the Romanian Carpathians

AbstractAimTo estimate the effects of environmental and human drivers on upper forest‐cover upward shift over the period 1945–2018.LocationRomanian Carpathians.MethodsUsing historical topographic maps and high‐resolution Sentinel‐2A satellite images, we delineated the location of the upper forest‐cover limit in 1945 and 2018 to obtain a binary raster with the “forest gains” and “no‐forest gains” for 1945–2018. The maps were overlapped over 12 independent variables to estimate how they affected the recent upper forest‐cover upward shift, and to predict its probability of expansion in the near future. To achieve this, logistic regression models were applied and then integrated into the GIS spatial analysis.ResultsForest gains of almost 35,000 ha have been detected at the upper forest limit in the study sites, leading to an average upward movement of 30 m (0.5 m per year), mainly at the altitudinal bands between 1,400 and 1,800 m a.s.l. (72%); only 9.7% of the gain was detected above the estimated potential climatic limit. The process was significantly inversely related to elevation (−17.3 ≤ β ≤ −5.7, p < 0.01), slope aspect (−1.5 ≤ β ≤ −0.4, p < 0.01), sheepfold numbers (−18.1 ≤ β ≤ −0.7, p < 0.01), and sheep (−18.3 ≤ β ≤ −0.6, p < 0.01) and cattle (−16.4 ≤ β ≤ −0.8, p < 0.01) populations. Strong direct effects were found for the slope angle (1.3 ≤ β ≤ 10.6, p < 0.01) and distance to sheepfolds (0.5 ≤ β ≤ 12.8, p < 0.01). A low contribution was indicated for the trend in mean air temperature (−1.1 ≤ β ≤ 4.3, p < 0.01), growing season length (−2.1 ≤ β ≤ 5.1, p < 0.01) and protective measures (−1.1 ≤ β ≤ 2.4, p < 0.01, for national parks; −1.8 ≤ β ≤ 1.2, p < 0.01, for natural parks).ConclusionsThe analysis demonstrated that decreased land‐use intensity and, in particular, declining traditional practices were the foremost mechanisms of the recent upper forest‐cover upward shift, whereas the effect of climate warming remains not so obvious.

Revisit the Upper Portion of the Japan Sea Proper Water: A Recent Structural Change and Freshening in the Formation Area

AbstractLong‐term transition in the deep water of the Japan Sea was investigated to understand how oceans respond to climate change. A basin‐scale density decrease in the upper portion of the Japan Sea Proper Water (UJSPW) by 0.01 σθ was detected from the period 1964–1985 (Period I) to that of 2001–2019 (Period II) using Argo‐ and ship‐based data sets. The density decrease was mainly due to a temperature increase of 0.3°C. Based on the pycnostad density, the UJSPW was redefined as the water mass of 27.30–27.33 σθ, along with the core density of 27.30–27.31 σθ. The dissolved oxygen (DO) and thickness in the UJSPW showed a notable decrease between the periods, along with the isopycnal surfaces flattening. Warming down to 700 m and freshening in the upper 300 m were observed in the winter UJSPW formation area in the northwestern Japan Sea. An influence of the hemispheric‐scale regime shift occurred in 1988/1989 on the UJSPW warming was suggested, along with the long‐term trend in the winter air temperature. The freshening in the formation area was attributable to the increase in winter precipitation in the Amur River basin and the decrease in winter sea‐ice extents in the Okhotsk and northern Japan Seas. The intensified stratification in the UJSPW formation area brought a decrease in the amount of the UJSPW formation through the prevention of winter deep convection, which resulted in the thinner thickness and lower DO in the UJSPW in Period II, along with the temperature increase.

Assessments of long-term precipitation and temperature variations during snow cover periods using high-elevation AMeDAS data in central Japan

Long-term hourly data records of the Automated Meteorological Data Acquisition System (AMeDAS) with snow depth measurements at three high elevation sites were analyzed in central Japan to assess the decadal scale winter climate variabilities with the effects of observation biases. Year-to-year variations of persistent snow cover periods (PSCPs) did not show a significant shortening trend with the delays of starting the PSCP associated with El Niño in December and forward to the ending of the PSCP with nationwide warming in March. Significant warming trends in the surface air temperature averaged in PSCPs were not identified, and length of the PSCP strongly contributed to the year-to-year variations of monthly averaged winter air temperatures. Long-term variabilities of precipitation records were primarily affected by changing the gauge type and data resolutions. After a simple correction of gauge undercatch by air temperature and wind speed, the amount of precipitation increased by around 20 % at the northern station but only by 3 % in the south due to frequent rain-on-snow events. In the two northern stations, snowfall amounts on the order of around 10 % were estimated to be missing in the precipitation records, where a long-term decreasing trend in occurrences of freezing precipitation was also found. The statistics calculated by AMeDAS data were verified using the data of the Vaisala Present Weather Detector in the Sugadaira Highland.

Observed changes in temperature and precipitation over Asia, 1901-2020

Asia is the largest continent in the world and home to 4.7 billion people. Climate change on this continent, therefore, attracts a significant amount of attention from scientists and policy-makers. However, observational studies of long-term climate change over the continent as a whole are lacking. Using updated, homogenized observational data from stations in Asia since 1901 and systematic-bias-adjusted data from stations in China after 1950, we analyzed the long-term trends of surface air temperature (SAT) and precipitation in Asia and China from 1901-2020. The results showed that (1) in the 120 yr between 1901 and 2020, the annual mean SAT rose significantly at rates of 0.13 ± 0.01 and 0.14 ± 0.03°C decade-1 in Asia and China, respectively. The year 2020 in Asia may have been the warmest year since the beginning of the 20th century. (2) Since 1901, in both Asia and China, the annual mean minimum temperature increased more than twice as fast as the maximum temperature, and the diurnal temperature range (DTR) dropped significantly. (3) From 1901-2019, the annual precipitation anomaly percentage in Asia showed a significant increasing trend at an average rate of 0.52 ± 0.10% decade-1, and the increase was more obvious in high latitudes than in low to mid-latitudes. (4) Since 1901, there has been no significant change in annual precipitation in China, but there was a weak and non-significant decrease in the first half of the 20th century and a significant increase after the mid 20th century. The results presented in this paper can help us understand the spatio-temporal patterns and causes of climate change in the Asian continent and Chinese mainland.

Water resources and regional climate change: Almaty metropolis case

Water resource vulnerability in urbanized areas due to the impact of climatic factors manifests a complex and urgent challenge, assessing which is of great scientific, social, and applied significance. The intensity and changes of the hydrological characteristics of urban water objects differ significantly from these of natural water bodies. The condition of water objects is the most important indicator of the overall ecological well-being of a metropolis. This research aimed to evaluate the current (1971-2020) climate change and its influence on water resources during the warm period of the year based on the example of Almaty Metropolis. The study showed an increase of air temperature (from 0.17°С/10 years up to 0.41°С/10 years) at all target weather stations, with the greatest change observed in foothill areas (Almaty Joint Hydrometeorological Station ). The observed precipitation change fell within the limits of mean multiyear values. The calculated basic hydrological characteristics of river runoff showed an increase since 1990s explained by air temperature and glacier melt trends. The article proposes certain recommendations on considering the influence of natural factors on Almaty’s water resources, keeping in my mind that water management affects many areas of human activity.

Analysis of monthly, seasonal and annual air temperature variability and trends in Gujarat

Analysis of monthly, seasonal and annual air temperature variability and trends in Gujarat

Recent Trends of Mean Maximum and Minimum Air Temperatures in Bangladesh

The annual, seasonal, and monthly maximum and minimum air temperature time series for 34 stations in Bangladesh have been examined during the period 1981– 2020 in this study. Three statistical tests were used in the analysis namely Mann–Kendall, Sen’s slope estimator, and linear regression, respectively. 47% of stations experienced significantly rising maximum air temperature trends during the pre-monsoon, 100% during the monsoon, 74% during the post-monsoon, and 24% during the winter season, respectively. Similar findings have been made about minimum air temperatures during the pre-monsoon, monsoon, post-monsoon, and winter seasons in 41, 91, 41, and 35% of stations over Bangladesh. According to the linear regression technique, the significant increasing trends of the maximum air temperatures at Patuakhali and Mongla stations are 0.83°C/decade and 0.82°C/decade in February and October, respectively. Furthermore, at Sandwip and M. Court, the significant increasing minimum air temperature trends in July and March are 0.26°C/decade and 0.66°C/decade, respectively. The highest monthly maximum and minimum air temperature time series value falls (decreases) were seen in January over the stations at Mongla (-0.58°C/decade) and Sandwip (-0.63°C/decade), respectively. This information will be useful in developing adaptation plans to mitigate the harmful effects of climate change. Vulnerability assessments, disaster management, enhanced structure design, institutional reform, and antiextreme climate engineering are some of the viable climate change adaptation approaches in Bangladesh due to rising temperatures.

Analysis of Air Temperature and Precipitation Trends in Kandahar city, Afghanistan from 1990-2019

This study aims to analyze trends of three, annual average temperature, annual average T-max, annual average T-mini, and precipitation over the last 30 years 1990-2019 in Kandahar City, the western part of Afghanistan. For the purpose of analysis, available data from Afghanistan Meteorological Department (AMD) and Power Data Access Viewer dataset were used. First, daily average temperature and precipitation data were converted to monthly average data, then converted to annual average data for statistical calculation. The linear regression equation and trend magnitude was applied to identify the trend of temperature and precipitation. Analysis of the data demonstrated an upward trend in average temperature, average T-max, average T-mini, and downward precipitation, the most upward trend obtained in an annual average of T-mini and less upward trend in an annual average of T-max. Simultaneously, by increasing temperature, precipitation decreased which indicates dry and hot temperatures. The ongoing climate change affects various factors, especially agriculture, and socioeconomics. On this basis, it is recommended that the result could serve as a key in making plans and policies for those authorities involved in the planning. Further research is needed to identify other climatic parameters for a comprehensive understanding of the current and future climatic situation of the study area. Keywords: Air temperature, Precipitation, Climate change, Kandahar city, Trend line