Decrease In Diurnal Temperature Range Research Articles

Past and future trends of diurnal temperature range and their correlation with vegetation assessed by MODIS and CMIP6

Temperature anomalies and changes in the diurnal temperature range (DTR) are expected to pose physiological challenges to biota; hence, both spatial and temporal variations in DTR provide important insights into temperature-induced stress in humans, animals, and vegetation. Furthermore, vegetation could dampen temperature variability. Here, we use the Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data of Land Surface Temperature (LST) to evaluate the global variation in DTR and its rate of change in spatial and temporal scales for the two decades spanning from 2001 to 2020. We show that North America, Africa, and Antarctica, as well as the global mean, experienced statistically significant DTR rates of change over the last 20 years in either summer, winter, or the annual mean. The rates were all negative, indicating the day-night temperature differences are decreasing in those regions because night temperatures are increasing at a faster rate than day temperatures. MODIS data of the Normalized Difference Vegetation Index (NDVI) revealed a strongly negative correlation with DTR, with a spatial correlation coefficient of −0.61. This correlation demonstrates a prominent dampening effect of vegetation on diurnal temperature oscillations. For future DTR projections, we used 19 models in the Coupled Model Intercomparison Project 6 (CMIP6) to predict global DTR trends from 2021 to 2050 with low and high CO2 concentration scenarios. The high CO2 emission scenario projects significant decreases in DTR in circumpolar regions, central Africa, and India compared to the low CO2 scenario. This difference in the two scenarios underscores the substantial influence of increased global temperatures and elevated CO2 concentration on DTR and, consequently, on the ecosystems in certain regions.

Diurnal Temperature Range and Its Response to Heat Waves in 16 European Cities—Current and Future Trends

An important indicator of climate change is the diurnal temperature range (DTR), defined as the difference between the daily maximum and daily minimum air temperature. This study aims to investigate the DTR distribution in European cities of different background climates in relation to the season of the year, climate class and latitude, as well as its response to exceptionally hot weather. The analysis is based on long-term observational records (1961–2019) coupled with Regional Climate Model (RCM) data in order to detect any projected DTR trends by the end of the 21st century under intermediate and high emission greenhouse gases (GHGs) scenarios. The analysis reveals marked variations in the magnitude of DTR values between the cities, on the one hand, and distinct patterns of the DTR distribution according to the climate class of each city, on the other. The results also indicate strong seasonal variability in most of the cities, except for the Mediterranean coastal ones. DTR is found to increase during hot days and heat wave (HW) days compared to summer normal days. High latitude cities experience higher increases (3.7 °C to 5.7 °C for hot days, 3.1 °C to 5.7 °C for HW days) compared to low latitude cities (1.3 °C to 3.6 °C for hot days, 0.5 °C to 3.4 °C for HW days). The DTR is projected to significantly decrease in northernmost cities (Helsinki, Stockholm, Oslo), while it is expected to significantly increase in Madrid by the end of the 21st century under both the intermediate- and high-emission scenarios, due to the asymmetric temperature change. The asymmetrical response of global warming is more pronounced under the high-emission scenario where more cities at higher latitudes (Warsaw, Berlin, Rotterdam) are added to those with a statistically significant decrease in DTR, while others (Bucharest, Nicosia, Zurich) are added to those with an increase in DTR.

[Effect of diurnal temperature range on the number of elderly inpatients with ischemic stroke in Hunan Province].

Objective: To study the effect of diurnal temperature range on the number of elderly inpatients with ischemic stroke in Hunan Province. Method: Demographic and disease data, meteorological data, air quality data, population, economic and health resource data of elderly inpatients with ischemic stroke were collected in 122 districts/counties of Hunan Province from January to December 2019. The relationships between the diurnal temperature range and the number of elderly inpatients with ischemic stroke were analyzed by using the distributed lag non-linear model, including the cumulative lag effect of the diurnal temperature range in different seasons, extremely high diurnal temperature range and extremely low diurnal temperature range. Results: In 2019, 152 875 person-times were admitted to the hospital for ischemic stroke in the elderly in Hunan Province. There was a non-linear relationship between the diurnal temperature range and the number of elderly patients with ischemic stroke, with different lag periods. In spring and winter, with the decrease in diurnal temperature range, the risk of admission of elderly patients with ischemic stroke increased (Ptrend<0.001, Ptrend=0.002);in summer, with the increase in diurnal temperature range, the risk of admission of elderly patients with ischemic stroke increased (Ptrend=0.024);in autumn, the change in the diurnal temperature range would not cause a change in admission risk (Ptrend=0.089). Except that the lag effect of the extremely low diurnal temperature range in autumn was not obvious, the lag effect occurred in other seasons under extremely low and extremely high diurnal temperature ranges. Conclusion: The high diurnal temperature range in summer and the low diurnal temperature range in spring and winter will increase the risk of admission of elderly patients with ischemic stroke, and the risk of admission of elderly patients with ischemic stroke will lag under the extremely low and extremely high diurnal temperature ranges in the above three seasons.

Changes in Diurnal Temperature Range Over Nigeria from 1960 to 2019

Diurnal temperature range (DTR) is an important derived variable used in detecting signature of observed climate changes. Understanding its changes in  recent time is important for managing and coping with climate change induced risks. This study analysed the long term trend and abrupt changes in  diurnal temperature range over Nigeria from 1960 to 2019. Descriptive statistics, Mann-Kendall trend test, Sen’s slope and Pettit’s tests were used to  assess the characteristics, trend, abrupt change and significance in annual DTR time series. Pearson correlation was used to examine the spatial  relationship between DTR and minimum temperature, maximum temperature, precipitation and cloud cover. Results showed that mean DTR amount  varied across spatio-temporal scales with steady increase from the coastal region, coupled with a weak inter-annual variability (CV &lt; 3%). The trend  analysis showed a significant decreasing DTR in most grid points (GP) and regions of Nigeria, with the exception of Enugu, Ado-Ekiti and Warri. Also a  significant negative trend was observed at the Guinea, Sudan and Sahel savanna regions. Abrupt changes occurred in the 1970s in the entire regions and  most of the GPs with Ado-Ekiti, Calabar, and Enugu occurred in 1991 while Maiduguri and Jos experienced such changes in 2011. Furthermore,  significant abrupt changes were observed at the following GPs and regions; Ikeja, Kaduna, Kano, Katsina, Sokoto, Yelwa, Yola, Guinea, Sudan and Sahel  Savannas. This decrease in DTR over most of the GP and the entire region indicate that the climate of Nigeria is becoming warmer possibly due to  environmental changes with precipitation and cloud cover being the major drivers of DTR variability in Nigeria. Thus, proper climate actions should be  taken through adaptation and resilient planning for the sustainable development of socio-economic and natural systems. 

Anthropogenic Influence on the Diurnal Temperature Range since 1901

Abstract The diurnal temperature range (DTR) as measured by the difference between daily maximum (Tmax) and minimum (Tmin) temperatures is of great importance to human health, ecology, and agriculture. The link of its long-term change to anthropogenic forcing is still unclear. This study shows evidence of human influence on long-term changes in DTR over the globe, five continents, and China during the past century (1901–2014). Using multiple observational datasets, we find a general decrease in the DTR over most of the global land since 1901, especially after the mid-1950s. Changes in DTR are due to different warming rates of Tmax and Tmin in response to external forcings. The climate models that participated in phase 6 of the Coupled Model Intercomparison Project Phase 6 (CMIP6) generally reproduce most of the changes in DTR, along with those in Tmax and Tmin. The models have underestimated the observed changes in DTR, however. A formal detection and attribution analysis shows that the anthropogenic forcing signal, including both greenhouse gas and aerosol emissions but dominated by the greenhouse gas emissions, is the main driver for these changes. The anthropogenic aerosol signal can be detected in Tmax and Tmin but not in DTR during the period of 1901–2014 over the globe and most continents. These indicate the observed decrease in DTR is not a simple response to anthropogenic aerosol emission. The natural signal is negligible in almost all the cases. Globally, anthropogenic influence is estimated to explain more than 90% of the observed changes in the three variables. In China, human influence is also clearly detected, although model simulated results on the regional scale have larger deviation. Significance Statement The diurnal temperature range (DTR) is of great importance in many areas. We compare multiple observational datasets with the simulations by climate models that participated in the latest phase (phase 6) of the Coupled Model Intercomparison Project (CMIP6), finding evidence of human influence on long-term changes in DTR over the past century (1901–2014) and robust evidence for the period since the early 1950s. The decrease in DTR as seen in the observational dataset is caused by different warming rates of daily maximum and daily minimum temperature in response to anthropogenic forcing, including both greenhouse gases and aerosols.

Relationship between diurnal temperature range and emergency ambulance dispatches due to stroke in Guangzhou, China

BackgroundThe evidence between diurnal temperature range (DTR) and stroke remains controversial and sparse. We aimed to assess the relationship between DTR and emergency ambulance dispatches (EADs) due to stroke, and to explore whether there were effect modifications to the relationship. MethodsA Quasi-Poisson generalized linear regression combined with a distributed lag non-linear model was used to examine the relationship between DTR and EADs for stroke between January 1st 2011 and June 30th 2018 in Guangzhou, China. We estimated the effects of the low DTR and high DTR (defined as DTR below and above 10 °C respectively) on EADs. The effects of minimum, maximum, 5th, 25th, 50th, 75th, and 95th percentiles of DTR compared with the DTR of 10 °C were also analyzed. ResultsA total of 20,275 EADs for stroke were included for analyses, among which 17,556 EADs were used in the model further adjusted for age and sex. A quasi-U-shaped relationship between DTR and EADs over lag0–2 days was observed. For the low DTR, per 1 °C decrease in DTR was significantly associated with an increase of 2.64% (RR = 1.03, 95% CI: 1.01–1.04) for EADs, while per 1 °C increase for the high DTR was non-significantly related with an increased risk of EADs (RR = 1.01, 95% CI: 0.90–1.13). Significant effects of the 5th and 25th percentiles of DTR on EADs were found when compared with the DTR of 10 °C. No significant effect modifications by age, sex or season were found to the association between DTR and EADs. ConclusionsWe found a quasi-U-shaped relationship between DTR and EADs due to stroke in this study, while age, sex or season did not significantly modify the association between DTR and EADs. More high-quality evidence is needed to further explore and validate the relationship between DTR and stroke.

The long-term trend in the diurnal temperature range over Sri Lanka from 1985 to 2017 and its association with total cloud cover and rainfall

This study is focused on studying the long-term trend of the diurnal temperature range (DTR) in three temperature zones in Sri Lanka using daily maximum and minimum temperature data set for the recent 33-year (1985–2017). We investigate the potential reasons for the long-term trend in the DTR by studying the response of the DTR to Total Cloud Cover (TCC) and rainfall on a seasonal basis. On an annual basis, results indicate that the DTR significantly decreased per decade by −0.14 °C, −0.16 °C, and −0.18 °C over the high elevation temperature zone (HT), low-elevation temperature zone one (LT-2), and low elevation temperature zone two (LT-2), respectively. The annual decreasing trend of DTR in three temperature zones is mainly due to the larger increase in minimum temperature over the HT (0.13 °C/decade), LT-1 (0.23 °C/decade), and LT-2 (0.14 °C/decade) zones than the maximum temperature from 1985 to 2017. Furthermore, a decreasing trend in DTR is observed during the southwest monsoon (SWM), first inter-monsoon (FIM), second inter-monsoon (SIM), and northeast monsoon (NEM) seasons, where the most prominent decreasing trend in HT, LT-1, and LT-2 is seen in NEM (−0.19 °C/decade), SIM (−0.24 °C/decade), and SWM (−0.40 °C/decade) seasons, respectively. The strong inverse correlation between the DTR and TCC in all seasons indicates that increasing TCC influences the decrease in DTR over the HT, LT-1, and LT-2 zones. Concomitant increasing trends in rainfall during NEM, FIM, and SIM seasons may be one of the possible causes of the DTR decreases in the aforementioned seasons over three temperature zones in Sri Lanka.

Quantifying maize grain yield losses caused by climate change based on extensive field data across China

Climate change can have significant impacts on maize (Zea mays L.) grain yield. In this study, we used extensive multi-year field experimental data (n = 423) across different climatic regions of China to distinguish effects of different climate factors on maize grain yield and mimicking the effect of climate change, in particular, temperature and solar radiation. Across the years and climatic regions, the major driver for the yield difference was found to be the diurnal temperature range (DTR) and accumulated photosynthetically active radiation (PAR). 1 °C decrease in DTR and 100 MJ decrease in accumulated PAR resulted in 1.0 t ha−1 and 0.85 t ha−1 reduction in maize grain yield, respectively. 1 °C increase in growing season mean temperature (Tmean) and minimum temperature (Tmin) resulted in 0.83 t ha−1 and 0.67 t ha−1 maize grain yield reduction. By mimicking the effect of climate change on maize grain yield, it was found that 1 °C increase in Tmean resulted in 0.83 t ha−1 (5.8%) maize grain yield reduction. Decrease in PAR also decreased maize grain yield significantly and the 1% decrease in PAR decreased maize grain yield by 0.15 tons per ha. Among all the five cultivars in this study, yield reductions of ZD958 and NH101 induced by 1 °C increase in Tmean were the smallest compared to other three cultivars. The quantitative analysis can provide important guidance to predict possible quantitative outcomes of future changes in crop productivity due to climate change and search for effective mitigation strategies such as cultivar selection.

Exploring spatial and temporal trends of diurnal temperature range in the region of the Subarnarekha river basin India

This study analyzed the spatial and temporal trends of diurnal temperature range (DTR) for 35-years (1983–2017) in the region of the Subarnarekha river basin of Jharkhand, India. The daily data of maximum temperature (Tmax) and minimum temperature (Tmin) were habituated to compute the DTR, whereas rainfall data is used to measure its relationship with DTR, on a monthly annual and seasonal basis. Mann–Kendall test and Sen’s slope method has been used to detect the increasing or decreasing trends in climatic data with their statistical significance. The annual mean DTR of the basin is 11.97 °C With a maximum in pre-monsoon (16.36 °C) and minimum in monsoon (6.94 °C). A significant negative trend (− 0.31 °C/decade) was observed in annual DTR over the basin. On a seasonal basis, all four seasons show a negative trend in DTR with the largest significant decreasing trend in the pre-monsoon season (− 0.49 °C/decade). On an annual and seasonal basis, a significant negative correlation between DTR and rainfall is found, indicating that rainfall has a significant impact on the variation of DTR in this basin. A concomitant increase in rainfall might be one of the possible causes of the decreases in DTR in the basin.

Assessment of urban heat island warming in the greater accra region

The Greater Accra region is the most urbanized region in Ghana. Over the last decade, the region has undergone rapid population shift and urban sprawl. This has modified the natural environment of the area and led to the formation and warming of Urban Heat Island (UHI). Previous studies have not established enough evidence on the existence of UHI phenomenon in the region. For this reason, this study examined the existence, magnitude, and spatial extent of UHI warming as well as its effect on temperature extremes in the region. The study used Landsat satellite imagery captured in 1991, 2002 and 2017, and in-situ daily minimum and maximum temperature data spanning the period 1980 to 2017. The satellite images were processed and analyzed using an integrated Geographic Information System (GIS) and remote sensing technique while extreme temperature indices were assessed with the ClimPACT2 software. The study found that UHI existed in the region with an increasing spatial coverage and a magnitude of about 4.07 ∘C, 5.79 ∘C, and 4.86 ∘C in 1991, 2002, and 2017 respectively. The built-up and bare land areas experienced the strongest effect of UHI warming. In addition, enhanced UHI warming effect caused an increase in the frequency and intensity of warm temperature extremes in the region. A faster increase in night time temperatures than day time resulted in a decrease in diurnal temperature range of the region. Considering the high rate of warming amidst rapid urban expansion, more warming is expected in the region. This is expected to exacerbate climate extreme events and weather-related health issues. It is also expected to increase energy consumption, air pollution and human discomfort.

Changes of temperature and precipitation extremes in a typical arid and semiarid zone: Observations and multi‐model ensemble projections

AbstractThe spatiotemporal changes of temperature and precipitation extremes in a typical arid and semiarid zone (Gansu Province, China) were investigated, including the latest observations (1960–2016) and the National Aeronautics and Space Administration Earth Exchange Global Daily Downscaled Projections (NEX‐GDDP) dataset that provides statistically downscaled Coupled Model Inter‐comparison Project Phase 5 (CMIP5) future climate projections (2017–2099) based on the Mann–Kendall test, linear regression, 5‐year smoothed average and Bayesian model average (BMA) methods. The results show the following: (a) Apart from a slight decrease of diurnal temperature range (DTR), other temperature extreme indices presented significant trends over 1960–2016. Annual regional nighttime temperature increased at a faster rate than daytime temperature. In the seasonal series, cool nights (TN10p) and cool days (TX10p) showed significant decreases and warm nights (TN90p) and warm days (TX90p) significantly increased in all seasons. (b) Precipitation extreme indices showed decreasing trends, except for the max 1‐day precipitation (RX1DAY) and simple daily intensity index (SDII) with a weaker coherence of spatial patterns. From the perspective of spatial characteristics, the western area had an increasing trend of total precipitation while the east had a significant decreasing trend. In the seasonal series, a significant increase of RX1DAY and the max 5‐day precipitation (RX5DAY) was found in winter, as compared with spring, summer and autumn. (c) Positive trends in warm indices (i.e., summer days, tropical days, warm nights and warm days) and negative trends in cold indices (i.e., frost days, ice days, cool nights and cool days) can be observed in the 21st century. A slightly decreasing consecutive dry days (CDD), together with obviously increasing heavy precipitation days (R10), extremely wet days (R99p), RX5DAY and SDII, suggests more extreme precipitation for 2017–2099. The results are of practical use in improving regional strategies for water resources and eco‐environment management, especially for arid and semiarid regions.

Land surface temperature variability across India: a remote sensing satellite perspective

Land surface temperature (LST) plays a key role in the surface energy budget computation and land surface process studies. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Aqua and Terra satellites provide comprehensive global LST estimates at a fine spatial resolution. The MODIS products were recently upgraded to Collection 6, and shown to be more accurate than its predecessor Collection 5 products. In this study, LST and its variability have been examined across India from Collection 6 of the Aqua MODIS data at 0.05° spatial resolution for the period of 2003 to 2017. All-India mean LST characteristics show distinctive features as compared to the well-documented mean characteristics of near-surface air temperature. All land cover types except permanent snow and ice, and cold desert areas exhibit bimodal peaks in seasonal variations of daytime LST. The daytime LST over the coldest and high-altitude regions of northern India shows anomalous positive linear relationship with NDVI at a monthly scale. However, monthly domain-mean daytime LST of cropland regions is largely negatively correlated with NDVI as compared to other land cover types. Results reveal that about 17% of the Indian landmass received its hottest LST during 2010 followed by 2016. Linear trend analysis for the 15-year period of mean annual LST shows a decrease in diurnal temperature range over most parts of the country due to rather rapid increase in nighttime LST than daytime LST, similar as changes in near-surface air temperature across the country.

Selection of general circulation models for the projections of spatio-temporal changes in temperature of Borneo Island based on CMIP5

A study has been conducted to evaluate the changes in temperature of Borneo Island for different representative concentration pathway (RCP) scenarios through statistical downscaling of an ensemble of general circulation models (GCMs) selected using entropy-based methods. A combination of past-performance and envelope approaches was used for the selection of GCM ensemble from a pool of 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) GCMs. Ranking of the GCMs was done separately at each grid point by using three entropy-based feature selection methods. Climate Research Unit (CRU) gridded temperature data was used as dependent variable and the simulated temperature of different GCMs for the period 1961–2005 was used as independent variable for the selection of GCMs. The scores obtained by the GCMs at different CRU grids were aggregated using compromise programming method and then ranked for entire Borneo Island using group decision-making method. Linear scaling method was applied to remove the biases in GCMs, followed by random forest (RF)–based regression method to generate multi-model ensemble projections. The results revealed that FIO-ESM, MRI-CGCM3, GFDL-CM3, and IPSL-CM5A-MR are the most suitable GCMs for the projection of temperature in the study area. The projection of temperature using the selected GCMs indicated increase in temperature in the Borneo Island, particularly in the southwest regions. The minimum temperature was projected to increase more (3.3 to 4.7 °C) compared with maximum temperature (3.0 to 4.6 °C) and thus, the diurnal temperature range (DTR) was projected to decrease gradually until the end of the twenty-first century. Increase in average and maximum temperatures was projected more during the southwest (SW) monsoon compared with the northeast (NE) monsoon. The study indicated that large increase in temperature and decrease in DTR would have significant impact on ecology and bio-environment of the island which have one of the dense ecological diversities in the world.

Declining diurnal temperature range in the North China Plain related to environmental changes

The decreases in diurnal temperature range (DTR) observed in most regions are generally linked to the increase in cloud cover. However, declining clouds and rising aerosols observed over the North China Plain (NCP) of China make it elusive to elucidate the underlying mechanisms behind the declining DTR observed in this region. Here, we analyze the changes in DTR characteristics in the NCP based on 54-year surface temperature observations, in combination with collocated environmental variable measurements. Overall, there is a significant declining trend of DTR from 1960 to 2014 at a rate of − 0.12 °C/decade, largely due to a larger increase in minimum temperature during the night. The cloud effect on DTR is further explored by comparing DTR under clear-sky and overcast conditions, which exhibits a distinct annual cycle with a minimum in summer and a maximum in winter. The decreasing rate of DTR under overcast condition is − 0.30 °C/decade, much faster than the rate of − 0.17 °C/decade under clear-sky condition, indicating steady increases in the nighttime warming effect of middle- or high-clouds. Also, the elevated aerosol concentration could contribute to the declining DTR, due to the cooling effect of aerosols. Moreover, the effect induced by sunshine duration and water vapor on DTR cannot be ignored either. All of the aforementioned environmental variables combine to affect the long-term trend of DTR, despite their different roles in modulating DTR. Our findings call for better understanding of the influence of environmental factors on regional climate system at the diurnal timescale.

Seasonal trends of air temperature and diurnal range in the Arabian Peninsula, the Levant, and Iraq: a spatiotemporal study and development of an online data visualization tool

As the temperature and the diurnal temperature range (DTR) influence our life in many fields like agriculture and health, changes in either parameter may affect our current and future plans in such areas. This paper investigates the variability of temperature and DTR in the Levant and the Arabian Peninsula (172 stations in 12 countries) in different study periods of 10, 25, 40, 50, and 60 years. The data were tested for homogeneity using four standard tests, and we used the nonparametric statistics Mann-Kendall and Theil-Sen to calculate trend significance, direction, and magnitude in time series. Our results show a significant warming trend in 45–60% of the region with an average increase of 0.65, 0.43, and 0.30 °C/decade for the 25-, 40-, and 50-year study periods. The highest number of stations that have a significant increase in temperature occurs in spring and summer. On the other hand, decreasing DTR trends occur in about 31% of the region, mostly in the south of the Arabian Peninsula at 0.60 °C/decade. This work, additionally, provides an interactive online tool that shows the trends and temperature on zoomable maps, charts, and other visuals to station level. This tool could benefit researchers and strategic planners for the studied region. In many stations, we found that there are a significant increase in temperature and a decrease in DTR which reflect a severe change in the climate that should be considered in future planning. We recommend expanding this study to cover precipitation and other meteorological factors.

Changes in the temperature and precipitation extremes in China during 1961–2015

Based on daily maximum temperature (Tmax), daily minimum temperature (Tmin) and daily precipitation collected from 1867 meteorological stations in China from 1961 to 2015, the spatiotemporal variations in temperature and precipitation extremes and their associations with large-scale atmospheric and oceanic circulation patterns were analyzed using linear trend analysis, Pearson correlation analysis and Mann-Kendall method. Results indicate that both the maximum Tmin (TNx) and the minimum Tmin (TNn) had increased significantly at rates of 0–0.5 °C and 0.2–1.0 °C per decade respectively in most of China, whereas the trends in the maximum Tmax (TXx) and the minimum Tmax (TXn) were not significant, resulting in a decrease of diurnal temperature range (DTR) at rates of 0–0.7 °C per decade in most of northeastern China, northern China and western China. The percentage changes in TXn and TNn were much higher than those of TXx and TNx. For precipitation indices, simple daily intensity index (SDII) and extremely wet-day precipitation (R99p) had increased at rates of 0.10 mm/day and 2.6 mm per decade respectively, but the trends of maximum 1-day precipitation (Rx1day), maximum 5-day precipitation (Rx5day) and total wet-day precipitation (PRCPTOT) were not significant in China. The spatial trends of five precipitation indices were also not significant in almost the whole of China. Higher percentage changes of precipitation indices were mainly appeared in western China. Most of climatic indices had positive correlation with Atlantic multidecadal oscillation (AMO) and negative correlation with East Atlantic/Western Russia (EA/WR). The variations of TXx and TNx were more related to the variability of AMO and EA/WR in China, and those of TXn and TNn were more associated with the Arctic oscillation (AO) in northeastern China, northern China and northern Xinjiang. The variations of precipitation indices were not significantly related to the circulation patterns in the vast majority of China.

Global diurnal temperature range (DTR) changes since 1901

Previous observational analyses show that the land-surface diurnal temperature range (DTR) has decreased in the past 6 decades worldwide. Based on a newly developed China Meteorological Administration–Land Surface Air Temperature (CMA-LSAT) dataset, we analyzed the DTR changes between 1901 and 2014. Results indicate that the global land surface DTR significantly decreased at a rate of − 0.036 °C decade− 1 over the 1901–2014 period, mainly due to the large decrease in DTR from 1951 to 2014. For the first half of the twentieth century, most grid boxes (spatial resolution 5° × 5°) show a positive DTR trend, with the positive trends of 32.4% grid boxes being statistically significant, leading to a large and significant increase of 0.048 °C decade− 1 in DTR. However, a dramatic reversal in DTR change occurred in early 1950s, with most parts of global lands exhibiting a shift from increasing to decreasing trends. The global land average DTR decrease during 1951–2014 was − 0.054 °C decade− 1, with 45.0% grid boxes showing significant negative trends. The reverse phenomenon is more obvious in the Northern Hemisphere than that in the Southern Hemisphere. For the periods 1979–2014 and 1998–2014, the decreasing trends in DTR mainly occur in the Northern Hemisphere. The DTR in the Southern Hemisphere experienced much larger increases during the two recent periods than during the period 1951–2014. Asia, Eastern North America, and Australia exhibited widespread decreases in DTR, although the trend pattern for global DTR is generally mixed during 1979–2014 and 1998–2014. There is a good negative correlation between DTR and precipitation in the Northern Hemisphere from 1901 to 2014, with a correlation coefficient of − 0.61. The change in precipitation and number of volcanic eruptions, and the “early brightening” of Europe (Stockholm) all benefit the increase of DTR at global and regional scales in the first half of the twentieth century.

Unidirectional trends in annual and seasonal climate and extremes in Egypt

The presence of short- and long-term autocorrelations can lead to considerable change in significance of trend in hydro-climatic time series. Therefore, past findings of climatic trend studies that did not consider autocorrelations became a questionable issue. The spatial patterns in the trends of annual and seasonal temperature, rainfall, and related extremes in Egypt have been assessed in this paper using modified Mann-Kendal (MMK) trend test which can detect unidirectional trends in time series in the presence of short- and long-term autocorrelations. The trends obtained using the MMK test was compared with that obtained using standard Mann-Kendall (MK) test to show how natural variability in climate affects the trends. The daily rainfall and temperature data of Princeton Global Meteorological Forcing for the period 1948–2010 having a spatial resolution of 0.25° × 0.25° was used for this purpose. The results showed a large difference between the trends obtained using MMK and MK tests. The MMK test showed increasing trends in temperature and a number of temperature extremes in Egypt, but almost no change in rainfall and rainfall extremes. The minimum temperature was found to increase (0.08–0.29 °C/decade) much faster compared to maximum temperature (0.07–0.24 °C/decade) and therefore, a decrease in diurnal temperature range (− 0.01 to − 0.16 °C/decade) in most part of Egypt. The number of winter hot days and nights are increasing, while the number of cold days is decreasing in most part of the country. The study provides a more realistic scenario of the changes in climate and weather extremes of Egypt.

Air temperature conditions in northern Nordaustlandet (NE Svalbard) at the end of World War II

This article presents the results of an investigation into air temperature conditions in northern Nordaustlandet (NE Svalbard) based on meteorological observations made by German soldiers towards the end of World War II (1944/1945) and 4 months after its end. Traditional analysis using mean monthly data was supplemented by a detailed analysis based on daily data: maximum temperature, minimum temperature and diurnal temperature range. The latter kind of data made it possible to study such aspects of climate as the number of “characteristic days” (i.e., the number of days with temperatures exceeding specified thresholds), day‐to‐day temperature variability, and duration, onset and end dates of thermal seasons. The results from Nordaustlandet for the warmest period of the early 20th century warming period (ETCWP) were compared with temperature conditions both historical (the end part of the Little Ice Age) and contemporary (different sub‐periods taken from the years 1981–2017) to estimate the range of warming during the ETCWP.Analysis reveals that the expedition year 1944/1945 in Nordaustlandet was, in the majority of months, the warmest of all analysed periods, that is, both historical and contemporary periods. The study period was markedly warmer than 1981–2010 (mean annual −6.5 vs. −8.4 °C) but colder than the periods 2011–2016 (−5.7 °C) and 2014–2017 (−5.8 °C). The majority of mean monthly air temperatures in the ETCWP lies within two standard deviations of the modern 2014–2017 mean. This means that values of air temperature in the study period lie within the range of recent temperature variability. All other thermal characteristics show changes in accordance with expectations associated with general warming of the Arctic (i.e., a decrease in diurnal temperature range and number of cold days, and an increase in number of warm days). The latter days were most common in the ETCWP.

Trends in mean maximum temperature, mean minimum temperature and mean relative humidity for Lautoka, Fiji during 2003–2013

The current work observes the trends in Lautoka’s temperature and relative humidity during the period 2003–2013, which were analyzed using the recently updated data obtained from Fiji Meteorological Services (FMS). Four elements, mean maximum temperature, mean minimum temperature along with diurnal temperature range (DTR) and mean relative humidity are investigated. From 2003–2013, the annual mean temperature has been enhanced between 0.02 and 0.080C. The heating is more in minimum temperature than in maximum temperature, resulting in a decrease of diurnal temperature range. The statistically significant increase was mostly seen during the summer months of December and January. Mean Relative Humidity has also increased from 3% to 8%. The bases of abnormal climate conditions are also studied. These bases were defined with temperature or humidity anomalies in their appropriate time sequences. These established the observed findings and exhibited that climate has been becoming gradually damper and heater throughout Lautoka during this period. While we are only at an initial phase in the probable inclinations of temperature changes, ecological reactions to recent climate change are already evidently noticeable. So it is proposed that it would be easier to identify climate alteration in a small island nation like Fiji.