Variability Of Diurnal Temperature Range Research Articles

Interannual variability of diurnal temperature range in CMIP6 projections and the connection with large-scale circulation

Interannual variability of diurnal temperature range in CMIP6 projections and the connection with large-scale circulation

Spatial variability of diurnal temperature range and its associations with local climate zone, neighborhood environment and mortality in Los Angeles

Urbanization alters the Earth’s emissivity and leads to intraurban differences in temperature variations, including diurnal temperature range (DTR). Despite DTR as a factor of thermal discomfort and mortality risk worldwide, its spatial variability and intraurban associations with local climate zone (LCZ), neighborhood environment and mortality risk have not been investigated. This study first applied the LCZ framework to evaluate associations between climate-sensitive urban design and long-term DTR exposure in Los Angeles, a megacity with the largest DTR in the United States. Using fine-scale daytime and nighttime Landsat thermal imagery to quantify DTR, we found that compact low-rise areas had high DTR, high-rise areas with moderate DTR, and natural areas with the lowest. Young-age, non-white and low-income populations were vulnerable and exposed to high DTR. A spatial Bayesian Poisson regression confirmed that neighborhoods with higher DTR exhibited higher mortality risk after controlling for socioeconomic factors (relative risk: 1.047, 95% credibility interval 1.013–1.082). We did not observe a significant association between mean temperature and mortality in our study. As spatial variability of DTR induces heterogeneous exposure and the evidence that long-term DTR exposure is positively associated with mortality across neighborhoods, planners and policymakers should consider urban landscaping to mitigate large DTR for risk reduction.

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 < 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.

Beyond linear correlation: Strong nonlinear structures in diurnal temperature range variability over southern China

The correlation structure and dynamical properties in diurnal temperature range (DTR) variability over southern China during 1979–2018 are studied in this study. Detailed results show that the linear correlation of DTR variability can be well captured by the first-order autoregressive (AR (1)) process over most of the southern stations. Since the standard detrended fluctuation analysis (DFA) based on power law assumption is designed to determine the long-range correlation strength but not the short-term correlation strength, a novel way of modified DFA is proposed to estimate the parameter of AR (1) process well over the range of short time scales. Moreover, beyond the linear correlation, the strong nonlinear structures are also detected in DTR variability with marked residual structures, i.e. significant time-reversal asymmetry and/or residual delay maps (RDM) with trough-ridge asymmetry. The mixed structures of linear correlation and strong nonlinear features improve the understandings on the prediction and predictability of DTR variability.

Variability of diurnal temperature range over Pacific Island countries, a case study of Fiji

Diurnal temperature range (DTR) is an important index in climate change studies in addition to its influence upon environment and thermal comfort. Understanding variability in DTR at regional scales is, thus, important. In Fiji and other Pacific Island countries, DTR information is important in forecasting thermal comfort. This work is based on Fiji using gauge-based gridded mean monthly DTR data from the Climatic Research Unit (CRU). Annual and monthly DTR for the second half of the twentieth century to the present day are analyzed to establish temporal trends and spatial patterns. A combination of parametric and non-parametric tests was applied to investigate trend, correlation, simple linear regression, and interannual variability in the datasets. Findings show that DTR increases with an increase in latitude over Fiji. The mean monthly DTR between 6.58 and 7.37 °C in June and January coincide with winter and summer, respectively. Cumulative annual mean (CAM) of T, Tmx, and DTR showed increasing trends during the study period while the CAM of Tmn depicted a decreasing trend. Results suggest that DTR has a positive significant (insignificant) correlation with Tmx (T), but shows an opposing significant relationship with Tmn at 5% significance level. Each of DTR, Tmx, Tmn, and T experienced a general increase in values across the timeframe provided by the data. Records show an overall increase of 0.05 °C/decade in DTR. However, since the early 1990s, DTR has been characterized by a downward trend. Nonetheless, the overall trend of increasing DTR is explained by a greater increase in maximum temperatures over minimum temperatures. The observed rate of increase in DTR in warm months exceeds that in cold months. The findings form a baseline for further studies investigating the factors influencing DTR variability, and how the variability is affecting human thermal comfort.

Multi-factor analysis of DTR variability over Israel in the sea/desert border

The contributions of twelve independent factors/variables to the magnitude of the local diurnal temperature range (DTR) in Israel were examined, and five to seven were found to contribute significantly. Israel was chosen due to its complex terrain with several climatic zones and proximity to the Mediterranean Sea. The seven sites for this study represent different terrains, from mountainous with a Mediterranean climate to desert. Each site had 6 years of data available. Stepwise analysis was performed in order to determine the contribution of each factor/variable at each site. The linear correlations between the DTR and each factor were calculated. These were carried out at each site for the whole year and for each season, separately. Relative humidity was found to have the largest DTR contribution at all sites, for 3 seasons, except summer at shoreline sites and in Jerusalem. The daily cloud cover and the wind speed had small contributions in most sites. The magnitude of the DTR was found to vary largely with location and to be considerably smaller in the seashore sites than those inland.

Variability of Diurnal Temperature Range During Winter Over Western Himalaya: Range- and Altitude-Wise Study

The current trends in diurnal temperature range, maximum temperature, minimum temperature, mean temperature, and sun shine hours over different ranges and altitudes of Western Himalaya during winter have been studied. Analysis of 25 years of data shows an increasing trend in diurnal temperature range over all the ranges and altitudes of Western Himalaya during winter, thereby confirming regional warming of the region due to present climate change and global warming. Statistical studies show significant increasing trend in maximum temperature over all the ranges and altitudes of Western Himalaya. Minimum temperature shows significant decreasing trend over Pir Panjal and Shamshawari range and significant increasing trend over higher altitude of Western Himalaya. Similarly, sunshine hours show significant decreasing trend over Karakoram range. There exists strong positive correlation between diurnal temperature range and maximum temperature for all the ranges and altitudes of Western Himalaya. Strong negative correlation exists between diurnal temperature range and minimum temperature over Shamshawari and Great Himalaya range and lower altitude of Western Himalaya. Sunshine hours show strong positive correlation with diurnal temperature range over Pir Panjal and Great Himalaya range and lower and higher altitudes.

Linking the southern annular mode to the diurnal temperature range shifts over southern Africa

ABSTRACTThe link between the diurnal temperature range (DTR) and the southern annular mode (SAM) over southern Africa for the October to December period during 1960 to 2012 is established using observations. The DTR shifts are consistent with the change of moisture and temperature advection over the subregion which is related to the SAM‐induced circulation alterations. As such, we consider these changing circulation patterns as playing the dominant role in different types of the DTR development. In fact, for the long‐term influence of changes in the large‐scale circulation over southern Africa, the SAM circulation may have substantially contributed to the long‐term development of cloud cover/precipitation, which can be used as a proxy for the DTR variability in recent decades. Therefore, cloud cover and precipitation changes acted as a disguise rather than the actual cause for the variations in DTR. At the same time, while the mean temperature trends over southern Africa are similar to the global trends that indicate general warming, this increase is superimposed on the significant DTR decadal variability. Consequently, the DTR can be considered as a possible radiative forced index independent of internal climate variations, which is able to provide additional information for the detection and attribution of climate change over southern Africa.

The Maritime Influence on Diurnal Temperature Range in the Chesapeake Bay Area

Abstract This study analyzes the influence of the Atlantic Ocean and Chesapeake Bay on the diurnal temperature range (DTR) reported by nearby weather stations. Coastal locations reported the smallest DTRs and DTR fluctuations, and DTR increased with distance from the ocean. Month of the year and airmass type also proved to be significant predictors of DTR. All locations showed a bimodal annual DTR pattern with peaks during the transitional seasons and experienced the greatest DTR during dry and/or warm air masses. Proximity to the ocean had the largest (smallest) influence on DTR during dry (moist) air masses with extreme (moderate) temperatures. Seasonally, the proximity to the ocean had the strongest impact on DTR during early–middle spring. A multiple regression model using distance from water, month, and airmass type explains over 30% of DTR variability in the area (p < 0.01). Airmass type has the largest influence on DTR, and changes in both air mass and month impacted the DTR of continental locations more than coastal locations. Land use, cloud cover, and wind speed/direction are additional variables that could account for differences not explained by the model.

Dominant modes of Diurnal Temperature Range variability over Europe and their relationships with large‐scale atmospheric circulation and sea surface temperature anomaly patterns

The relationships between the dominant modes of interannual variability of Diurnal Temperature Range (DTR) over Europe and large‐scale atmospheric circulation and sea surface temperature anomaly fields are investigated through statistical analysis of observed and reanalysis data. It is shown that the dominant DTR modes as well as their relationship with large‐scale atmospheric circulation and sea surface temperature anomaly fields are specific for each season. During winter the first and second modes of interannual DTR variability are strongly related with the North Atlantic Oscillation and the Scandinavian pattern, while the third mode is related with the Atlantic Multidecadal Oscillation. Strong influence of the Atlantic Multidecadal Oscillation and the Arctic Oscillation on spring DTR modes of variability was also detected. During summer the DTR variability is influenced mostly by a blocking‐like pattern over Europe, while the autumn DTR variability is associated with a wave train like pattern, which develops over the Atlantic Ocean and extends up to Siberia. It is also found that the response of DTR to global sea surface temperature is much weaker in spring and summer comparing to winter and autumn. A correlation analysis reveals a strong relationship between DTR modes of variability and the Cloud Cover anomalies during all seasons. The influence of the potential evapotranspiration and precipitation anomalies on DTR modes of variability is strongest during summer, but it is significant also in spring and autumn. It is suggested that a large part of interannual to decadal DTR variability over Europe is induced by the large‐scale climate anomaly patterns via modulation of cloud cover, precipitation and potential evapotranspiration anomaly fields.

U.S. Diurnal Temperature Range Variability and Regional Causal Mechanisms, 1901–2002

Abstract Long-term (1901–2002) diurnal temperature range (DTR) data are evaluated to examine their spatial and temporal variability across the United States; the early century origin of the DTR declines; and the relative regional contributions to DTR variability among cloud cover, precipitation, soil moisture, and atmosphere/ocean teleconnections. Rotated principal component analysis (RPCA) of the Climatic Research Unit (CRU) Time Series (TS) 2.1 dataset identifies five regions of unique spatial U.S. DTR variability. RPCA creates regional orthogonal indices of cloud cover, soil moisture, precipitation, and the teleconnections used subsequently in stepwise multiple linear regression to examine their regional impact on DTR, maximum temperature (Tmax), and minimum temperature (Tmin). The southwestern United States has the smallest DTR and cloud cover trends as both Tmax and Tmin increase over the century. The Tmin increases are the primary influence on DTR trend in other regions, except in the south-central United States, where downward Tmax trend largely affects its DTR decline. The Tmax and DTR tend to both exhibit simultaneous decadal variations during unusually wet and dry periods in response to cloud cover, soil moisture, and precipitation variability. The widely reported post-1950 DTR decline began regionally at various times ranging from around 1910 to the 1950s. Cloud cover alone accounts for up to 63.2% of regional annual DTR variability, with cloud cover trends driving DTR in northern states. Cloud cover, soil moisture, precipitation, and atmospheric/oceanic teleconnection indices account for up to 80.0% of regional variance over 1901–2002 (75.4% in detrended data), although the latter only account for small portions of this variability.

Associations of diurnal temperature range change with the leading climate variability modes during the Northern Hemisphere wintertime and their implication on the detection of regional climate trends

This study examines associations of diurnal temperature range (DTR) changes in observations at the global, hemispheric, subcontinental, and grid box scales with five leading climate variability modes, including the Arctic Oscillation (AO), hemispheric Pacific–North America (PNA)–like mode, Pacific Decadal Oscillation, El Niño Southern Oscillation (ENSO), and Antarctic Oscillation (AAO) during the Northern Hemisphere winter season (Jan–Mar). Winter DTR variability in most subcontinental regions is significantly related to variations in either the AO, or hemispheric PNA‐like mode, or ENSO index in the Northern Hemisphere. In the Southern Hemisphere, the DTR variability appears closely coupled with variations in the ENSO and AAO. From 1951 to 2000, variations in the circulation patterns account for a significant fraction of the DTR increase at all scales although the strength of these associations varies geographically. After removing the linearly congruent component of leading climate variability modes from the total wintertime DTR trends in the observations, statistically significant residual trends in DTR are still found at the global, hemispheric, and most subcontinental regions. Ensemble mean multimodel averaged DTR trends to major anthropogenic and natural forcing are significantly smaller than not only observed total DTR trends but also residual trends at these large scales. The implication of changes in the leading climate variability modes on the detection of regional DTR trends is discussed. We find that the detection of the regional response to combined anthropogenic and natural forcing is robust to the exclusion of trends related to changes of the five modes considered here.

Changes of Diurnal Temperature Range in Taiwan and Their Large-Scale Associations: Univariate and Multivariate Trend Analyses

By analyzing the long-term (1950-2007) variability of diurnal temperature range [DTR; daytime maximum (T max ) minus nighttime minimum (T min )] at 21 stations in Taiwan, this study applies univariate analysis, a trend-free prewhitening procedure combined with a modified Mann-Kendall test, and EOF-based multivariate trend analysis (TEOFA) to the ranked station DTR, T max , and T min . To reveal the large-scale associations with the local TEOFA results, this study also uses global gridded T max , T min , nighttime marine air temperature, and sea level pressure (SLP) datasets archived at the U.K. Meteorological Office Hadley Centre. On the basis of the signs and relative magnitudes between the annually-mean T max and T min trends, the stations can be classified into three types through univariate analysis. With a common increasing T min, type-A (type-B) stations have an increasing T min (T max ) faster than T max (T min ) whereas type-C stations have a decreasing T max . Both type-A and type-C (type-B) thus show(s) a decreasing (an increasing) DTR. For most stations, the increasing T min is the largest in December-February. In contrast, all type-B stations have an increasing T max peaking in June-August. Noticeably, six of nine type-B stations, either in the remote islands or in the seaports, are particularly influenced by the ocean. Three DTR trend modes stand out of TEOFA. The first mode, TEOF 1 , captures increasing DTR trends at four type-B stations and decreasing DTR trends elsewhere. The associated increasing T min (T max ) trend is consistent with the increasing (decreasing) clouds during nighttime (daytime) and is well-correlated with the large-scale patterns, suggesting that it is part of the global warming scenario. Nevertheless, TEOF 1 also captures a decreasing T max trend in Taiwan's highly developed western plains (i.e., type C) and eastern China where an increasing SLP pattern is observed, implying the anthropogenic forcings on DTR. TEOF 2 (TEOF 3 ) depicts the decadal-to-interdecadal DTR variability in central (northern) Taiwan. Evolution of TEOF 2 shows smaller (larger) amplitude before 1970s (after mid-1980s). The associated large-scale patterns suggest that TEOF 2 (TEOF 3 ) captures the relationship between an intensified (weakened) East Asian winter monsoon and La Nina (El Nino)-like condition in eastern (central) equatorial Pacific. Embedded in a Pacific-Japan-like teleconnection pattern, the southwestward intrusion of Pacific subtropical anticyclone in June-August that signifies the weakened southwesterly monsoon is also depicted by TEOF 2 .

Contrails, Natural Clouds, and Diurnal Temperature Range

Abstract The direct impact of aircraft condensation trails (contrails) on surface temperature in regions of high aircraft density has been a matter of recent debate in climate research. Based on data analysis for the 3-day aviation grounding period over the United States, following the terrorists’ attack of 11 September 2001, a strong effect of contrails reducing the surface diurnal temperature range (DTR) has been suggested. Simulations with the global climate model ECHAM4 (including a contrail parameterization) and long-term time series of observation-based data are used for an independent cross check with longer data records, which allow statistically more reliable conclusions. The climate model underestimates the overall magnitude of the DTR compared to 40-yr ECMWF Re-Analysis (ERA-40) data and station data, but it captures most features of the DTR global distribution and the correlation between DTR and either cloud amount or cloud forcing. The diurnal cycle of contrail radiative impact is also qualitatively consistent with expectations, both at the surface and at the top of the atmosphere. Nevertheless, there is no DTR response to contrails in a simulation that inhibits a global radiative forcing considerably exceeding the upper limit of contrail radiative impact according to current assessments. Long-term trends of DTR, the level of natural DTR variability, and the specific effect of high clouds on DTR are also analyzed. In both ECHAM4 and ERA-40 data, the correlation of cloud coverage or cloud radiative forcing with the DTR is mainly apparent for low clouds. None of the results herein indicates a significant impact of contrails on reducing the DTR. Hence, it is concluded that the respective hypothesis as derived from the 3-day aviation-free period over the United States lacks the required statistical backing.

Diurnal temperature range as an index of global climate change during the twentieth century

The usefulness of global‐average diurnal temperature range (DTR) as an index of climate change and variability is evaluated using observations and climate model simulations representing unforced climate variability and anthropogenic climate change. On decadal timescales, modelled and observed intrinsic variability of DTR compare well and are independent of variations in global mean temperature. Observed reductions in DTR over the last century are large and unlikely to be due to natural variability alone. Comparison of observed and anthropogenic‐forced model changes in DTR over the last 50 years show much less reduction in DTR in the model simulations due to greater warming of maximum temperatures in the models than observed. This difference is likely attributed to increases in cloud cover that are observed over the same period and are absent in model simulations.