Seasonal Temperature Trends Research Articles

Roles of dynamic and thermodynamic effects in seasonal mean surface air temperature trends over Central Asia during 1979–2018

Roles of dynamic and thermodynamic effects in seasonal mean surface air temperature trends over Central Asia during 1979–2018

Sea surface temperature trend analysis by Mann-Kendall test and sen’s slope estimator: a study of the Hai Phong coastal area (Vietnam) for the period 1995-2020

Based on the Mann-Kendall test and Sen’s slope method, this study investigates the monthly, seasonal, and annual sea surface temperature (SST) trends in the coastal area of Hai Phong (West of Tonkin Gulf) based on the measurements at Hon Dau Station from 1995 to 2020. The results show a sea surface warming trend of 0.02°C/year for the period 1995-2020 (significant level α = 0.1) and of 0.093°C/year for the period 2008-2020 (significant level α = 0.05). The monthly SSTs in June and September increased by 0.027°C/year and 0.036°C/year, respectively, for the period 1995-2020, and by 0.080°C/year and 0.047°C/year, respectively, for the period 2008-2020. SST trends in winter, summer, and other months were either different for the two periods or not significant enough. This may be due to the impact of ENSO, which caused interannual SST variability in the Hai Phong coastal with two intrinsic mode functions (IMF) signals a period of ~2 (IMF3) and ~5.2 years cycle (IMF4). A combination of these signals had a maximum correlation of 0.22 with ONI (Oceanic Niño Index) delayed by 8 months. ENSO events took ~8 months to affect SST at Hai Phong coastal area for 1995-2020 and caused a variation of SST within 1.2°C.

Variations in temperature in a tropical town: a case study

Trend analysis of temperature on a local scale provides vital clues to the changes in amplitude with time and possibly the reasons for the changes. The present paper attempts to examine the temporal and seasonal trends in temperature of a developing township, Pattambi, Kerala in India from 1950 to 2018. We used Mann-Kendall rank statistics to examine the historical temperature data. The results show a general increase in annual temperature, especially the mean annual maximum temperature of the region across the year with a statistically significant increasing trend. The same trend could be seen in the case of southwest monsoon temperature. Another notable observation from the study is the statistically significant decrement in the winter temperature of the region. The regional changes in the temperature will have much impact on the economy and society in the area since the local livelihood is heavily dependent on agriculture.

The analysis of annual and seasonal surface air temperature trends of southern and southeastern Bosnia and Herzegovina from 1961 to 2017

In some areas of the world, regional climate change is in good agreement with global climate change. This study brings new information about what defines climate change in the contact area of Adriatic Sea and Southeastern Europe, and conclusions are based on trend analysis of annual and seasonal temperatures in the southern and southeastern parts of Bosnia and Herzegovina. Trend analysis was applied on mean annual surface air temperatures, mean maximum temperatures, and mean minimum temperatures of all four seasons. This study used 4 meteorological stations: Livno, Bileća, Mostar, and Ivan Sedlo for 56 years. The main statistical method is the Mann-Kendall test. The total number of analysis is 48. A statistically significant positive trend was determined in 36 analysis, while in the rest of the tests this was not the case. The highest amount of temperature increase is present in the mean maximum summer air temperatures in Livno and Ivan Sedlo. Mean minimum autumn air temperatures had the smallest increase. Negative trend is present in the mean autumn surface air temperatures and mean maximum autumn temperatures. Using a geographical information system resulted in visualizing regional differences in the spatial distribution of isotherms. The study area has combined the influence of orography and maritime effects of the Adriatic Sea. Having in mind these results, the growing temperature has been recognized as a problem which needs more attention in Bosnia and Herzegovina. Unfortunately, official documents which propose economic adaptation on climate change in this country are not at a satisfactory level.

Analysing the day/night seasonal and annual changes and trends in land surface temperature and surface urban heat island intensity (SUHII) for Indian cities

• Day/night seasonal and annual changes and trends (2001- 2018) in land surface temperature and surface urban heat island intensity (SUHII) for Indian cities (Lucknow, Kolkata and Pune). • Nighttime LST is a better indicator to study the urban heating effect due to its sensitivity towards urbanization. • Positive trends in mean annual daytime (0.003 to 0.059 °C/year) and nighttime (0.030 to 0.078 °C/year) LST are observed in all cities, except in Pune where urban cooling occurs during daytime. • Nighttime SUHII is positive for all cities with mean annual SUHII ranging from 1.34 to 2.07 °C. Understanding the patterns and possible causes of urban heat islands (UHI) effect due to urbanisation-induced anthropogenic activities is an important area in urban climatic research. Few studies on long-term thermal behaviour of Indian cities are available in the literature. Towards this, the present study investigates the day/night seasonal and annual changes and trends in land surface temperature (LST) and surface urban heat island intensity (SUHII) during the last two decades for three Indian cities (Lucknow, Kolkata and Pune) with distinct urban, physiographic and climatic setting. Moderate Resolution Imaging Spectroradiometer (MODIS) LST data products acquired during daytime and nighttime from 2001 to 2018 are processed and analysed for this purpose. MODIS-based aerosol optical depth (AOD) and normalised difference vegetation index (NDVI) products are used to understand the plausible reasons of change in LST and SUHII patterns. The urban (contiguous built-up) and non-urban (surrounding rural) areas are delineated by applying city clustering algorithm on MODIS Land Cover datasets of 500 m spatial resolution. Mann-Kendall and Seasonal-Kendall tests along with Theil-Sen estimator are used for trend analysis. The findings show that the diurnal temperature range (DTR) has decreased from 2001 to 2018 due to higher increase in nighttime LST as compared to daytime. Nighttime LST is a better indicator to study the urban heating effect due to its sensitivity towards urbanisation. Positive trends in mean annual daytime (0.003 to 0.059 °C/year) and nighttime (0.030 to 0.078 °C/year) LST are observed in all cities, except in Pune where urban cooling occurs during daytime. Increase in aerosol loading (with consequent decrease in air temperature and surface insolation) and vegetative cover over time are attributed as the primary reasons of urban cooling effect in Pune during daytime. Seasonal analysis indicate high warming rates during monsoon and summer seasons, particularly during nighttime (0.062 to 0.1 °C/year). Nighttime SUHII is positive for all cities with mean annual SUHII ranging from 1.34 to 2.07 °C. Statistically significant ( p <0.01) increasing trends are observed in mean annual SUHII (0.009 °C/year to 0.022 °C/year) for Kolkata and Pune. Decreasing trend in SUHII is observed over Lucknow due to higher rate of increase in LST in non-urban area as compared to urban area. The study highlights that geographical, physiographic and climatic setting along with anthropogenic processes in urban and its surrounding non-urban areas are critical towards understanding the causative factors in exacerbating the phenomenon of urban heating.

Seasonal variability in temperature trends and atmospheric circulation systems during the Eemian (Last Interglacial) based on n-alkanes hydrogen isotopes from Northern Finland

The Last Interglacial warm period, the Eemian (ca. 130–116 thousand years ago), serves as a reference for projected future climate in a warmer world. However, there is a limited understanding of the seasonal characteristics of interglacial climate dynamics, especially in high latitude regions. In this study, we aim to provide new insights into seasonal trends in temperature and moisture source location, linked to shifts in atmospheric circulation patterns, for northern Fennoscandia during the Eemian. Our study is based on the distribution and stable hydrogen isotope composition (δD) of n-alkanes in a lake sediment sequence from the Sokli paleolake in NE Finland, placed in a multi-proxy framework. The δD values of predominantly macrophyte-derived mid-chain n-alkanes are interpreted to reflect lake water δD variability influenced by winter precipitation δD (δDprec), ice cover duration and deuterium (D)-depleted meltwater. The δD values of terrestrial plant-derived long-chain n-alkanes primarily reflect soil water δD variability modulated by summer δDprec and by the evaporative enrichment of soil and leaf water. The δDprec variability in our study area is mostly attributed to the temperature effect and the moisture source location linked to the relative dominance between D-depleted continental and polar air masses and D-enriched North Atlantic air masses. The biomarker signal further corroborates earlier diatom-based studies and pollen-inferred January and July temperature reconstructions from the same sediment sequence. Three phases of climatic changes can be identified that generally follow the secular variations in seasonal insolation: (i) an early warming trend succeeded by a period of strong seasonality (ii) a mid-optimum phase with gradually decreased seasonality and cooler summers, and (iii) a late climatic instability with a cooling trend. Superimposed on this trend, two abrupt cooling events occur in the early and late Eemian. The Sokli δD variability is generally in good agreement with other North Atlantic and Siberian records, reflecting major changes in the atmospheric circulation patterns during the Eemian as a response to orbital and oceanic forcings.

Trend Analysis of Meteorological Variables: Rainfall and Temperature

The Souss-Massa region in southwestern Morocco is characterized by a semi-arid climate with high variability in rainfall. Frequent droughts and flash flood events combined with overexploitation of water resources in recent decades have had a significant impact on the human security and the economy which is mainly based on agriculture, tourism and fishery. For better management of extreme events and water resources under changing climatic conditions, a study was carried out to quantify the seasonal and annual variability and trends in rainfall and temperature over the past three decades with data from three stations. Climatological representative of the Souss-Massa region. The Mann-Kendall (MK) non-parametric test and the Sen’s slope are used to estimate the monotonic trend and magnitude of the trend of the variables, respectively. Statistical analysis of the rainfall series data set highlights that the occurrence of rainfall is unpredictable and irregular and the both the seasonal and annual rainfall trend appears negative (downward) for all the three climatological stations. The minimum temperature shows a remarkable increasing trend both on annual and seasonal scale while the maximum temperature registers a slightly increasing trend. The study presents some new insights on rainfall and temperature trends that will have significant impacts on the surface and groundwater resources of the region under changing climatic conditions. The results can help to prioritize new strategies to mitigate the risk of droughts, of floods and to manage water resources to sustain the dependence of agriculture tourism and fishery sectors in the region. Doi: 10.28991/cej-2021-03091765 Full Text: PDF

Different forms of carbon, nitrogen, and phosphorus influence ecosystem stoichiometry in a north temperate river across seasons and land uses

AbstractNatural and human features on land result in differential loadings of carbon (C), nitrogen (N), and phosphorus (P) to rivers that influence within ecosystem processing. However, little is known about how land use, together with seasonal changes in climate and hydrology, influence the relative proportions of C, N, and P in rivers. To evaluate the spatial and temporal patterns in ecosystem‐level C: N: P stoichiometry, we sampled 13 sites once per season for 3 yr along the main stem of a north temperate river with winter ice‐cover that flows across a gradient of forested, urban, and agricultural landscapes. We found that C concentrations were rather stable along the continuum, whereas N and P rapidly increased downstream due to urban and agricultural land uses. The flow‐weighted C: N: P ecosystem stoichiometry ranged from 2319: 119: 1 in the most upstream site to 368: 60: 1 at the outlet. The dominant form of N generally shifted from dissolved organic nitrogen in upstream forested reaches to nitrate in more impacted, downstream reaches, and winter stoichiometry was enriched in inorganic N and dissolved P forms. Concentrations of all three elements were generally lower in spring during year‐high flow due to dilution. The spatial and temporal variation in stoichiometry in this north temperate river covered much of the range previously observed between litter ratios and the Redfield ratio. This suggests that even moderate human impacts can have profound effects on riverine ecosystem stoichiometry, and that these effects are modulated by seasonal trends in temperature and hydrology.

Assessment of trends of air temperature based on 140-year observations of V.A. Mikhelson Meteorological Observatory

The article deals with the test of the main hypothesis about regional climate warming based on the analysis of unique continuous long-term observations of air temperature in 1879-2018 at V.A. Mikhelson meteorological observatory. The authors present annual and seasonal trends of air temperature for 140 years, which indicate its increase practically during the entire observation period. All considered statistical series can be characterized by the normal distribution of random variables. The cyclical nature of changes in air temperature for all series relative to their long-term average values and a period of a clear significant increase in temperature, which falls on the last three decades of both annual values and seasonal time intervals, have been revealed. Statistical criteria determined a clearly heterogeneous pattern of this period in relation to both the previous observation years and the entire 140-year period; in particular, its average air temperature is quite higher, which proves the warming of the region's climate over the past decades. It has been noted that the degree of air temperature rise in winter is higher than in summer. Positive changes in the elements of the heat balance, both during the growing season and throughout the year, in particular, the improvement of the conditions for overwintering agricultural crops, predetermines the need for research in the possible expansion of their varieties for cultivation in the Moscow region. Based on a comprehensive analysis and logical conclusions, we made a hypothesis about the influence of intensive development of heated buildings around the meteorological station on the air temperature rise in the last half century; however, it is impossible to measure such an influence today, as well as the influence of global warming due to other factors.

Warming in Europe: Recent Trends in Annual and Seasonal temperatures

Contemporary climate warming is a key problem faced not only by scientists, but also all by humanity because, as is shown by the experience of recent years, it has multiple environmental, economic and biometeorological implications. In this paper, the authors identify the magnitude of annual and seasonal temperature changes in Europe and its immediate surroundings on the basis of data from 210 weather stations from 1951 to 2020. An analysis of temperatures in the 70-year period shows that air temperature has continued to grow linearly in Europe since 1985. The rate of temperature rise in three seasons of the year, namely winter, spring and summer, does not differ greatly. The highest growth over the 1985–2020 timespan was recorded in spring and the lowest in autumn—0.061 °C/year and 0.045 °C/year, respectively. In winter, the rise in temperature should be considered the least steady, as opposed to the summer when it displays the greatest stability. Overall, the warming intensifies towards the north-east of the continent. Such a strong gradient of change is especially perceivable in winter and spring, and is also marked in autumn. The opposite is true in summer, when it increases towards the south and south-west.

Recent trends in hydroclimate and groundwater levels in a region with seasonal frost cover

In cold climate, the main annual recharge event is spring snowmelt. Projections of groundwater storage hence depend on winter hydroclimate. Winter recharge is a factor of rain, melt and ground frost. Increases in winter rain and melt have already been observed. However, due to complex processes involved in ground frost formation and its natural patchy coverage, the effect of ground frost on recharge is poorly understood.The objective of the study is to improve the understanding of the connection between groundwater storage and hydroclimate in Sweden and Finland, a region with temperate and cold climate, from a seasonal frost cover perspective. In the study, annual, frost-free season and frost season temperature and precipitation trends in the climate regions are compared between one global and two regional reanalysis datasets. Effective precipitation and wet day frequency trends between 1980 and 2010 are compared to groundwater level trends for the same period. Trends are calculated using the Mann-Kendall test and Sen’s slope.The results show that the region is generally experiencing warming and increased precipitation. These trends are strongest in the frost season. Further, the global dataset systematically underestimates median temperatures and precipitation compared to the regional datasets. Effective precipitation trends are generally weak, and indicate wetting in the frost season and drying in the frost-free season. Wet day frequency trends are decreasing significantly on the regional scale in Finland, but with nearly no trends in Sweden. Groundwater levels in southern Finland and southeastern Sweden are declining significantly, while groundwater levels in southwestern Sweden are significantly rising. The results indicate that groundwater trends in southern Finland are linked to wet day frequency and effective precipitation trends in the frost-free season, and that trends in the frost season have no impact on annual groundwater level trends. In southern Sweden, groundwater level trends appear linked to annual and frost-free season trends in effective precipitation, though insignificantly. These trends may be explained by century-scale trends in precipitation drought indices identified by previous studies.

Assessment of Climate Variability among Seasonal Trends Using In Situ Measurements: A Case Study of Punjab, Pakistan

This research assessed the changes in spatial patterns and the seasonal trends in temperature, precipitation, and relative humidity over 36 years (1979–2014) using Climate Forecast System Reanalysis (CFSR) datasets. The evaluation of climate deviations was the prime objective of this research. The augmented Dickey–Fuller Test (ADF) was used to scrutinize whether the data was either stationary or non-stationary. The results of the ADF test showed that all the datasets were found to be stationary at lag order 3. To observe undulations in the time series data, trend analyses were done using Sen’s slope (SS), Mann–Kendall (MK), and Cox and Stuart (CS) tests. For all the statistical analyses, we considered the 5% significance level (α = 0.05) and p &lt; 0.05 to be statistically significant. We observed significant (p &lt; 0.05) trends in spring (MAM) and autumn (SON) for minimum temperature (Tmin) in Punjab. We also noted a significant (p &lt; 0.05) trend in precipitation during autumn (SON). Annually, all the variables showed a non-significant (p &gt; 0.05) trend for Punjab, Pakistan, during the period 1979–2014. Climate variability, such as a decrease in precipitation, higher temperature, and relative humidity fluctuations, were the reasons for the imbalance in the sustainability of Punjab, Pakistan.

Econometric Modelling of Carbon Dioxide Emissions and Concentrations, Ambient Temperatures and Ocean Deoxygenation

AbstractThis paper analysed several longitudinal data sets for investigating the dynamic inter-relationships between CO2 emissions and atmospheric concentrations, ambient temperatures and ocean acidification and deoxygenation. The methodological framework addressed issues such as the use of temperature ‘anomalies’, diffusion of CO2 to atmospheric stations, distributional misspecification and non-stationarity of errors affecting empirical models, and use of spline functions for modelling trends in temperatures. Longitudinal data on CO2 emissions for 163 countries and atmospheric CO2 concentrations at 10 stations, ambient temperatures from over 8,500 weather stations and seawater composition from over 380,000 oceanographic stations were analysed for 1985–2018 by estimating dynamic random effects models using maximum likelihood methods. The main findings were that CO2 emissions exhibited rapid upward trends at the country level, while minimum and maximum temperatures showed cyclical patterns; economic activity and population levels were associated with higher CO2 emissions. Second, there were gradual upward trends in annual and seasonal temperatures compiled at weather stations, and atmospheric CO2 concentrations were significantly associated with higher temperatures in the hemispheres. Third, there was a steady decline in dissolved oxygen levels, and the interactive effects of water temperatures and pH levels were significant. Overall, the results underscore the benefits of reducing CO2 emissions for ambient temperatures and for ocean deoxygenation. Synergies between CO2 emissions, ambient temperatures and ocean acidification are likely to exacerbate the melting of polar ice.

Effect of diurnal temperature change on cardiovascular risks differed under opposite temperature trends.

Temperature change between neighboring days (TCN) is an important trigger for cardiovascular diseases, but the modulated effects by seasonal temperature trends have been barely taken into account. A quantified comparison between impacts of positive TCNs (temperature rise) and negative situations (temperature drop) is also needed. We evaluated the associations of TCNs with emergency room (ER) visits for coronary heart disease (CHD) and cerebral infarction (CI) in Beijing, China, from 2008 to 2012. A year was divided into two segments dominated by opposite temperature trends, quasi-Poisson regression with distributed lag nonlinear models estimating TCN-morbidity relations were employed, separately for each period. High morbidities of CHD and CI both occurred in transitional seasons accompanied by large TCNs. Under warming backgrounds, positive TCNs increased CHD risk in patients younger than 65 years, and old people showed limited sensitivity. In the cooling periods, negative TCNs induced CHD risk in females and the elderly; the highest RR showed on lag 6 d. In particular, a same diurnal temperature decrease (e.g., - 2°C) induced greater RR (RR = 1.113, 95% CIs: 1.033-1.198) on old people during warming periods than cooling counterparts (RR = 1.055, 95% CIs: 1.011-1.100). Moreover, positive TCNs elevated CI risk regardless of background temperatures, and males were particularly vulnerable. Seasonal temperature trends modify TCN-cardiovascular morbidity associations significantly, which may provide new insights into the health impact of unstable weathers.

Orbital Forcing Strongly Influences Seasonal Temperature Trends During the Last Millennium

AbstractInsolation changes caused by the axial precession induce millennial trends in last millennium temperature, varying with season and latitude. A characteristic seasonal trend pattern can be detected in both insolation and modeled surface temperature response. In the extratropical Northern Hemisphere, the maximum insolation trend occurs around April/May, while the minimum trend occurs between July and September. The temperature trend lags behind insolation trend by around a month. Hence orbital forcing potentially affects long‐term trends in proxy data, which are often sensitive to a distinct seasonal window. We find that tree‐ring reconstructions based on early growing season dominated records show different millennial trends from those for late summer dominated proxies. The differential response is similar to that seen in pseudo proxy reconstructions when considering proxy seasonality. This suggests that orbital forcing has influenced long‐term trends in climate proxies. It is therefore vital to use seasonally homogeneous data for reconstructing multicentennial variability.

Seasonal temperature trends on the Spanish mainland: A secular study (1916–2015)

AbstractTrends in seasonal mean values of maximum and minimum temperature are analysed in the Spanish mainland from the new MOTEDAS_century database. This new data set has been developed combining the digitalized archives from the Spanish Meteorological Agency (AEMET) with information retrieved from Annual Books published by the former Meteorological Agency dating back to 1916, and covers the period 1916–2015. In all four seasons, mean seasonal temperature of maximum (Tmax) and minimum (Tmin) increased. The raising occurred in two main pulses separated by a first pause around the middle of the 20th century, but differed among seasons and also between maximum and minimum temperature. Analysis of the percentage of land affected by significant trends in maximum temperature reveals two increasing phases in spring and summer for Tmax, and in spring, summer, and autumn for Tmin. However, winter Tmax only rose during the recent decades, and autumn Tmax in the first decades. Negative significant trends were found in extended areas in spring Tmax, and in spring, autumn, and summer Tmin, confirming the first pause around the 1940's–1960's. Trends of seasonal mean values of Tmax and Tmin are not significant for at least the last 25–35 years of the study period, depending on the season. The areas under significant positive trend are usually more extended for Tmin than Tmax at any season and period. Areas with significant trend expand and contract in time according to two spatial gradients: south‐east to north‐west (east‐west) for Tmax, and west to east for Tmin. We hypothesize a relationship between atmospheric prevalent advection and relief as triggering factors to understand spatial and temporal differences in seasonal temperatures at regional scale during the 20th century in the Iberian Peninsula.

Seasonal trend analysis of minimum air temperature in La Plata river basin

Regional economies that depend predominantly on agriculture and livestock are heavily affected by changes in air temperature, one such case are the activities in La Plata river basin (LPB). Some studies suggest that variations in the seasonal cycle and season onset would affect efficiency in the use of radiation by vegetation. This paper evaluates the distribution of minimum temperature seasonality trends over LPB, describes the trends in the seasonal cycle, and detects changes of minimum temperature extremes characterized by the number of frost days and the frequency of warm and cold nights. The analysis includes absolute minimum temperature (TnMin) and minimum average temperature (TnMean) from ERA5 reanalysis for the 1980–2015 period. Significant positive trends in the amplitude of annual average TnMin and TnMean are observed over more than half the area (53.5% and 69.9% of the basin, respectively). Amplitude and phase parameters suggest that average minimum temperature underwent greater variation than absolute minimum temperature over LPB. The shifts in phase indicate that minimum temperatures occurred earlier than usual in the year considering the 35-year series. In general terms, there is a shift toward warmer conditions. This warming is evident in seasonal trends of minimum temperature as well as in the significant increase in the number of warm nights, a significant decrease of cold days and a significant decrease in the number of frost days in the highest Andes mountains in the west of the LPB.

Effect of atmospheric circulation on surface air temperature trends in years 1979\u20132018

The effect of atmospheric circulation on monthly, seasonal and annual mean surface air temperature trends in the years 1979–2018 is studied by applying a trajectory-based method on the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis data. To the extent that the method captures the effects of atmospheric circulation, the results suggest that circulation trends only had a minor impact on observed annual mean temperature trends in most areas. Exceptions include, for example, a decrease in annual mean warming by about 1 °C in western Siberia, and increased warming in central Europe and the Arctic Ocean. However, the effect of circulation trends on seasonal and particularly monthly temperature trends is more substantial. Subtracting the effect of circulation changes from the ERA5 temperature trends leaves residual trends with a smoother annual cycle than the original trends. The residual monthly mean temperature trends also tend to agree better with the multi-model mean temperature trends from models in the 5th Coupled Model Intercomparison Project (CMIP5) than the original ERA5 trends do, with a 42% decrease in the mean square difference over the global land area. However, the corresponding decrease in the mean square difference of the annual mean temperature trends is only 6%.

Temperature changes and elevation‐warming relationships in the Carpathian Mountains

AbstractThis paper investigates the elevation‐warming relationships across the Carpathian Mountains, using the 0.1° × 0.1° gridded daily air temperature dataset developed within the CARPATCLIM project, in order to understand the spatial patterns of annual and seasonal temperature trends and test the hypothesis of enhanced warming with elevation. Temperature trend and elevation‐warming analyses were conducted over the 50 years of the dataset (1961–2010). The vertical variations of five key isotherms relevant for the development of cold‐climate weathering, presence of permafrost (−2°C, 0°C, +2°C, +3°C) and spread of forest vegetation (July +10°C) were also examined. The Carpathian Mountains are under visible annual and seasonal warming (stronger in the summer and winter), both daytime and nighttime. The warming process shows a great spatial inhomogeneity, but is more pronounced in the lowlands of the region, generally below 1,000–1,200 m. The correlations between elevation and warming rates across the Carpathians have been found both to be positive and negative, while mostly significant at the 5% level. Evidence of enhanced warming with elevation was found to be related to the minimum temperature increase mostly across the NW and SW Carpathians, at both annual and seasonal scales (winter, summer and spring). Less prominent EDW signals have been identified in the NE, E and S Carpathians (summer), as well as in the NE Carpathians (spring). Parts of the detected temperature trends and EDW signals have been considered to be an effect of the changing atmospheric circulation (i.e. westerly intensification especially in the winter), although other mechanisms and processes could be involved (e.g. snow‐albedo feedbacks in the spring). These results could serve as a reference for further investigations of climate warming effects across the Carpathian Mountains region (e.g. ecological and geomorphic), especially in relation to the augmented summer heat stress (e.g. more frequent heatwaves) and milder winters (e.g. less freezing days).

Spatio-temporal variation and trends of long-term meteorological variables in Nigeria

Natural environmental disasters in the developing countries of West Africa are at alarming rate which necessitate the investigation of long-term trend of rainfall and temperature. Current variation, trends of temperature, and rainfall across Nigeria were investigated using parametric and non-parametric statistical tools. Meteorological data obtained from the Nigeria Meteorological Agency in Lagos, Nigeria, from 1970 to 2010 were used for this analysis. Seasonal and annual trends of maximum temperature, minimum temperature, and rainfall were carried out using Mann-Kendall and Sen’s slope methods. Long-term linear regression of these meteorological variables was analyzed across eighteen locations in the country. Spatial distribution of seasonal trends of these variables was also estimated for the four seasons in Nigeria. The result of the linear regression on temperatures and rainfall showed increasing trends in most of the locations across the country. Similarly, Mann-Kendall and Sen’s slope analysis showed a significant increasing trend in most areas across the country. Consequently, recent phenomena of environmental hazard such as an outbreak of airborne diseases and flooding leading to the collapse of buildings and various environmental disasters can be linked to the observed result.