Diurnal Temperature Range

This study examines the trends and variations in several indices of daily and extreme temperature and precipitation in Canada for the periods 1950-2003 and 1900-2003 respectively. The indices are based on homogenized daily temperature and adjusted daily precipitation measurements which are special datasets that include adjustments for site relocation, changes in observing programs and corrections for known instrument changes or measurement program deficiencies. For 1950-2003, the analysis of the temperature indices indicates the occurrence of fewer cold nights, cold days and frost days, and conversely more warm nights, warm days and summer days across the country. The results are generally similar for 1900-2003 but they also include a decrease in the diurnal temperature range in southern Canada and a decrease in the standard deviation of the daily mean temperatures for many stations in western Canada. The analysis of the precipitation indices for 1950-2003 reveals more days with precipitation, a decrease in daily intensity and a decrease in the maximum number of consecutive dry days. The annual total snowfall significantly decreased in the south and increased in the north and northeast during the second half of the twentieth century. The results are generally similar for 1900-2003. The national series for the century shows an increase in annual snowfall from 1900 to the 1970s followed by a considerable decrease until the 1980s which also corresponds to a pronounced downward trend in the frequency of frost days. No consistent changes were found in most of the indices of extreme precipitation for both periods. RESUMÉ [Traduit par la rédaction] Cette étude examine les tendances et les variations dans plusieurs indices de température et de précipitation quotidiennes et extrêmes au Canada durant les périodes 1950-2003 et 1900-2003, respectivement. Ces indices sont basés sur des mesures de températures quotidiennes homogénéisées et de précipitations quotidiennes ajustées, qui sont des données spéciales comportant des ajustements pour tenir compte de la relocalisation de sites, de changements dans les programmes d'observation et de corrections relatives à des changements d'instruments ou à des lacunes des programmes de mesure connues. Pour la période 1950-2003, l'analyse des indices de température indique une fréquence plus faible de nuits froides, de jours froids et de jours de gel et, réciproquement, plus de nuits chaudes, de jours chauds et de jours d'été dans le pays. Les résultats sont à peu près semblables pour la période 1900-2003 mais ils incluent également une diminution dans l'amplitude quotidienne de la température dans le sud du Canada et une diminution dans l'écart type des températures quotidiennes moyennes pour plusieurs stations de l'ouest du Canada. L'analyse des indices de précipitations pour la période 1950-2003 révèle un plus grand nombre de jours avec précipitation, une diminution dans l'intensité quotidienne et une diminution dans le nombre maximum de jours secs consécutifs. La chute de neige totale annuelle a diminué dans le sud et augmenté dans le nord et le nord-est de façon marquée au cours de la deuxième moitié du vingtième siècle. Les résultats sont à peu près semblables pour la période 1900-2003. La série nationale pour le siècle montre une augmentation dans la chute de neige annuelle de 1900 jusqu'aux années 1970, suivie d'une diminution considérable jusque dans les années 1980, qui correspond aussi à une tendance à la baisse prononcée dans la fréquence des jours de gel. On n'a trouvé aucun changement persistant dans la plupart des indices de précipitations extrêmes pour les deux périodes.

This research analyzes and summarizes some thermal behavior of various urban surfaces in time and space using high-resolution video thermal radiometer situated at a height of 103 m, in the city of Tel-Aviv. The physical properties of the various urban elements, their color, the sky view factor (SVF), street geometry, traffic loads, and anthropogenic activity are important among the factors that determine the radiant surface temperature in the urban environment. During daytime, asphalt paved roads and rooftops were found to be the warmest urban elements in our study area. In contrast, exterior walls and trees hold the highest surface temperatures at night. Open spaced surfaces that are exposed to direct solar radiation during daytime and to heat loss at night were characterized by the highest diurnal temperature range. The radiometric stationary experiment revealed the temperature differences between diverse urban coverage to be at most 10 • C; such maximum temperature differences were measured in the early noon hours. The minimal temperatures were observed just before sunrise, when the temperature contrasts (4-5 • C) were smaller than in the early noon hours. The daytime hours between 9-10 a.m. and 5-8 p.m. turned out to be problematic for remote sensing of the urban environment, because the thermal differences between different objects were found to be insignificant. A remote survey aiming to study the urban environment should be conducted twice: in the early morning hours before sunrise (5 a.m.) and in the early noon hours (12-1 p.m.). The knowledge of thermal behavior of various urban components is an important tool for designers and decision-makers. If utilized properly, it can lead to climatic rehabilitation in urban areas and a reduction of the UHI.

Low, mid and high daily climate scenarios , as per the International Panel on Climate Change (IPCC) were generated using the Australian Commonwealth Scientific and Industrial Research Organisation's (CSIRO's) global atmosphere models. These scenarios based on IPCC's 21st century emission scenarios that combine a variety of assumptions about demographic, economic and technological driving forces likely to influence such emissions in the future, were used as input to a crop model to predict the impact of climate change on wheat yield at a location in south-eastern Australia. At this locality there are important likely changes in the primary climatic variables of temperature, rainfall and solar radiation. Generally, we found a strong and consistent positive trend in mean diurnal temperature range, followed by a significant negative trend in wheat yield under three climate scenarios with and without elevated CO 2 concentration. It is possible that negative trends identified over the future decades may be artefacts of the method of substituting historical variance for future variance. We observed that from present climate to projected low, mid and high global warming scenarios, median wheat yield may decrease by about 29%. Under these scenarios, but with an elevated atmospheric CO 2 climate, median wheat yield may decrease by about 25%. The effect of elevated CO 2 reduces the severity of the warmer air temperatures and lower rainfall but the effect is small (4%). Advances in agronomy and breeding must boost crop yields by around 25% over the coming decades, to keep in step with predicted climate change. #

Tremendous efforts have been devoted to improve our understanding of the anthropogenic effects on the atmospheric temperature change. In comparison, little has been done in the study of the human impacts on the subsurface thermal environment. The objective of this study is to analyze surface air temperature records and borehole subsurface temperature records for a better understanding of the urban heat island effects across the ground surface. The annual surface air temperature time series from six meteorological stations and six deep borehole temperature profiles of high qualities show that Osaka has been undergoing excess warming since late 19th century. The mean warming rate in Osaka surface air temperature is about 2.0°C/100a over the period from 1883 to 2006, at least half of which can be attributed to the urban heat island effects. However, this surface air temperature warming is not as strong as the ground warming recorded in the subsurface temperature profiles. The surface temperature anomaly from the Osaka meteorological record can only account for part of the temperature anomaly recorded in the borehole temperature profiles. Surface air temperature is conventionally measured around 1.5 m above the ground; whereas borehole temperatures are measured from rocks in the subsurface. Heat conduction in the subsurface is much less efficient than the heat convection of the air above the ground surface. Therefore, the anthropogenic thermal impacts on the subsurface can be more persistent and profound than the impacts on the atmosphere. This study suggests that the surface air temperature records alone might underestimate the full extent of urban heat island effects on the subsurface environment.

Solar radiation is an important input to crop growth models used for risk management and assessment purposes. Methods are explored to estimate daily solar radiation in the Argentine Pampas, one of the most important agricultural areas in the world. Two scenarios are considered: (i) sunshine duration data are available for a given location, or (ii) only daily temperature (minimum and maximum) and precipitation records exist. If sunshine duration data are available, an association between this quantity and atmospheric transmissivity yields daily radiation estimates with a root mean square error (RMSE) of 1.5 MJ m −2 per day. Without sunshine duration records, daily temperature and precipitation can be used to estimate atmospheric transmittance and then compute daily radiation values. A model linking predictors that are proxies of cloudiness and atmospheric humidity to atmospheric transmittance was fitted using Generalized Additive Models (GAMs), a modern statistical technique that does not assume any a priori functional forms for the association between predictors and predictand. The errors in radiation estimates using temperature and precipitation are larger (RMSE of 3.2 MJ m −2 per day) than those derived from sunshine duration, but they are comparable to results for other locations and methods. Most importantly, daily radiation estimates have small bias and the errors show no systematic patterns with season or other variables.

Haiti, Jamaica, etc.; the Pacific Ocean Islands, which include Fiji, Samoa, the Solomon Islands, Vanuatu, etc.; the Indian Ocean Islands, which include Comoros, the Maldives, Mauritius and the Seychelles; and the Mediterranean Sea Islands, which include Cyprus and Malta. ...

Land use and land cover change (LULCC) is primarily characterized as forest conversion to cropland for the development of agriculture. Previous climate modeling studies have demonstrated the LULCC impacts on mean climate and its long-term trends. This study investigates the diurnal and seasonal climatic response to LULCC in monsoon Asia through two numerical experiments with potential and current vegetation cover using the fully coupled Community Earth System Model. Results show that LULCC leads to a reduced diurnal temperature range due to the enhanced (reduced) diurnal cycle of the ground heat flux (sensible heat flux). Daily minimum surface air temperature (T min ) exhibits a clear seasonality over India as it increases most in the premonsoon season and least during the summer monsoon season. Similarly, a strong anticyclonic anomaly is present at 850 hPa over India in spring and over eastern China in autumn, but weak changes in circulation appear in winter and summer. In addition, the LULCC results in significant changes in the variability of the 2 m air temperature, as characterized by an enhanced variability in India and a reduced variability in northern China to eastern Mongolia in autumn and winter. Possible land-atmosphere feedback loops involving surface albedo, soil moisture, evapotranspiration, atmospheric circulation, and precipitation are offered as biogeophysical mechanisms that are responsible for the region-specific LULCC-induced diurnal and seasonal response.

Diurnal temperature range (DTR) is an important climate change index. Information on this parameter comes primarily from sparse and unevenly distributed observations of shelter air temperature. In this study, five years of GOES-8 based estimates of land surface temperature (LST) over the United States are used to evaluate DTR at high spatial resolution. The spatial and temporal patterns that emerged show a high degree of consistency with independent satellite estimates of the Normalized Difference Vegetation Index (NDVI). Specifically, the arid regions in the western and central U.S. have larger DTRs than the eastern United States or the northwest coast. When stratified by four major surface types, the western U. S. DTRs over these surface types are larger than over the eastern part. It is also observed that urban areas have the lowest DTRs especially over the polluted eastern U. S. The similarity of the DTR spatial and temporal patterns and variations of the independent satellite based vegetation index are encouraging and suggest that satellite based estimates of DTR carry a strong signal on surface conditions which are responsive to climate change.

Temperatures of the Arsia Mons caldera floor and two nearby control areas were obtained by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES). These observations revealed that the Arsia Mons caldera floor exhibits thermal behavior different from the surrounding Tharsis region when compared with thermal models. Our technique compares modeled and observed data to determine best fit values of thermal inertia, layer depth, and albedo. Best fit modeled values are accurate in the two control regions, but those in the Arsia Mons' caldera are consistently either up to 15 K warmer than afternoon observations, or have albedo values that are more than two standard deviations higher than the observed mean. Models of both homogeneous and layered (such as dust over bedrock) cases were compared, with layered-cases indicating a surface layer at least thick enough to insulate itself from diurnal effects of an underlying substrate material. Because best fit models of the caldera floor poorly match observations, it is likely that the caldera floor experiences some physical process not incorporated into our thermal model. Even on Mars, Arsia Mons is an extreme environment where CO 2 condenses upon the caldera floor every night, diurnal temperatures range each day by a factor of nearly 2, and annual average atmospheric pressure is only around one millibar. Here, we explore several possibilities that may explain the poor modeled fits to caldera floor and conclude that temperature dependent thermal conductivity may cause thermal inertia to vary diurnally, and this effect may be exaggerated by presence of water-ice clouds, which occur frequently above Arsia Mons.

An attempt is made in the present study to analyse observed and model simulated temperature extremes over Indian region. Daily maximum and minimum temperature data at 121 well-distributed stations for the period 1970-2003 have been used to study the observed changes in objectively defined values of temperature extremes. In addition, an assessment of future scenarios of temperature extremes associated with increase in the concentration of atmospheric greenhouse gases is done using simulations of a state-of-the-art regional climate modelling system known as PRECIS (Providing Regional Climate for Impact Studies) performed to generate the climate for the present (1961-1990) and future projections for the period 2071-2100. Observational analysis done with 121 stations suggests the widespread warming through increase in intensity and frequency of hot events and also with decrease in frequency of cold events. More than 75% stations show decreasing trend in number of cold events and about 70% stations show increasing trend in hot events. Percentage of stations towards the warming through intensity indices of highest maximum temperature, lowest minimum temperature is 78 and 71% stations, respectively. Remaining stations show opposite trends, however, most of them are statistically insignificant. Observational analysis for India as a whole also shows similar results. Composite anomalies for monthly temperature extremes over two equal parts of the data period show increase (decrease) in the frequency of hot (cold) events for all months. In general, PRECIS simulations under both A2 and B2 scenarios indicate increase (decrease) in hot (cold) extremes towards the end of twenty-first century. Both show similar patterns, but the B2 scenario shows slightly lower magnitudes of the projected changes. Temperatures are likely to increase in entire calendar year, but the changes in winter season are expected to be prominent. Diurnal temperature range is expected to decrease in winter (JF) and pre-monsoon (MAM) months.

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. Highlights • We have studied the trends of temperature (T) and diurnal temperature range (DTR) for the Arabian Peninsula, the Levant, and Iraq. • We used the nonparametric statistics Theil-Sen and Mann-Kendall and compared them to the normal linear slope. • We performed the study for five different periods (10-60 years) and compared the results. • For each of the T and DTR, we studied the trends for maximum, minimum, and average seasonal values over years. • We have provided an online visualization tool that shows the trends on maps, line charts, and fountain charts for the benefit of the readers of the journal. Electronic supplementary material The online version of this article (https://doi.

A high-quality monthly total cloud amount dataset for 165 stations has been developed for monitoring and assessing long-term trends in cloud cover over Australia. The dataset is based on visual 9 a.m. and 3 p.m. observations of total cloud amount, with most records starting around 1957. The quality control process involved examination of historical station metadata, together with an objective statistical test comparing candidate and reference cloud series. Individual cloud series were also compared against rainfall and diurnal temperature range series from the same site, and individual cloud series from neighboring sites. Adjustments for inhomogeneities caused by relocations and changes in observers were applied, as well as adjustments for biases caused by the shift to daylight saving time in the summer months. Analysis of these data reveals that the Australian mean annual total cloud amount is characterised by high year-to-year variability and shows a weak, statistically non-significant increase over the 1957-2007 period. A more pronounced, but also non-significant, decrease from 1977 to 2007 is evident. A strong positive correlation is found between all-Australian averages of cloud amount and rainfall, while a strong negative correlation is found between mean cloud amount and diurnal temperature range. Patterns of annual and seasonal trends in cloud amount are in general agreement with rainfall changes across Australia, however the high-quality cloud network is too coarse to fully capture topographic influences. Nevertheless, the broadscale consistency between patterns of cloud and rainfall variations indicates that the new total cloud amount dataset is able to adequately describe the broadscale patterns of change over Australia. Favourable simple comparisons between surface and satellite measures of cloudiness suggest that satellites may ultimately provide the means for monitoring long-term changes in cloud over Australia. However, due to the relative shortness and homogeneity problems of the satellite record, a robust network of surface cloud observations will be required for many years to come.

Four mean temperature variables, namely maximum (MAX), minimum (MIN), mean (MEAN) and diurnal temperature range (DTR), were considered for 14 selected observational stations throughout Sudan. The objectives were to investigate the seasonal and annual regimes, the seasonal and annual trends, the intra-annual variability (IAV) by the coefficient of variation (CV), and the interrelationships between the temperature variables and percent of possible sunshine. A mounting evidence of daytime and nighttime warming since the 1940s until 2005 is presented. The exception is the dry season which is dominated by daytime cooling attributable to the damping effect of dust haze/storms. Apparently, the progressive drought across inland locations has raised the MAXs, and to a lesser extent the MINs, of the wet season over those for the hot season. Accordingly, maximum rates of 0.451 and 0.336°C decade-1 were found for the nighttime and daytime temperatures, respectively. The extreme eastern and western locations have been frequently dominated by the warmest trend rates obtained nationwide. The prevalence of significant decreases (increases) of DTR is more apparent in the dry, hot and annual series (wet series). Depending on the temperature variable under consideration, many stations possessed significant trends toward either increased or decreased variability of the within-year monthly values, i.e. IAV. The correlation between the time series of annual CV and extreme values for each of the four temperature variables shows generally that warmer climate in Sudan is associated with higher intra-annual temperature variability and vise versa, i.e. the CV is directly correlated with the highest value within the year, but inversely correlated with the lowest one. The findings of this investigation also indicate that the DTR is directly related to percent of possible sunshine, but the relationship of the latter parameter is not so clear with MAX, MIN and MEAN.

A comparison is made between mean maximum and minimum temperatures, Tx and Tn, respectively, taken at Khartoum International Airport (urban) and Shambat Agrometeorological Station (rural) in the capital of Sudan. The objective was mainly to examine the influence of urbanization on the monthly, seasonal and annual temperature observations for the time period 1941-2005. Strong evidence exists for a decrease in the diurnal temperature range (DTR) in all seasons on the urban site due to different combinations of trends in Tn and Tx. A reverse tendency is notable on the rural site. The effect in Khartoum appears to be greatest in the hot season and least in the wet season, and is because of more warmth in Tn than in Tx. Significant increasing rates of Tn are apparent at both stations in the series of the hot and wet seasons as well as for the year, but the urban site (Khartoum) is warming at a faster rate than the rural one, except in the wet season because of excess rainfall in the urban site. Higher intra-annual variability in temperature is pronounced for Shambat than for Khartoum, while mixed results are obtained with regard to inter-annual variability. The night-time temperature (Tn) experiences stronger urban effect than the daytime temperature (Tx). An urban heat island intensity (UHII) of up to 6.4°C occurred at night in May (hot season) compared to a maximum UHII of 4.1°C during the daytime in November (dry season). Significant trends of urban warming are conspicuous in Tn during the dry and hot seasons. On the other hand, significant trends towards urban cooling are observed in Tx in all the seasons. The results of the present study suggest that the estimated UHII in the temperature series for Khartoum must be removed before an assessment of climatic change is made.

Catchment runoff is the most widely used catchment scale measurement in modelling studies, and we have a reasonable degree of confidence in its accuracy. The advent of satellites gives access to a new suite of measurements taken over a defined spatial range. These measurements, principally reflected or emitted radiation, provide hydrologists with new possibilities for quantifying the state of a catchment. Surface temperatures can be readily measured by a satellite on a scale comparable to the size of a small catchment.

Unprecedented needle loss of mature forest stands occurred in natural Swedish montane forests during 1987. Pine (Pinussylvestris L.) and spruce (Picea abies [L.] Karst.) needles turned reddish-brown during the spring and early summer. An intensive study within a severely damaged pine population indicated that damage was primarily due to a coincidence of shallow snow cover and severe cold from mid-December 1986 to middanuary 1987. This resulted in unusually cold soils and late thawing of the soils. Acute drought stress then developed in late winter during a period of sunny weather and great diurnal temperature ranges. Thus, the study supports the classical theory of winter desiccation as an important component in population ecology of cold marginal forests in this part of the world. Historical data indicate that the present kind of damage was more frequent prior to the present century. It is suggested that cold-induced dieback is an important, but often overlooked, disturbance process in northern boreal forests relevant to Holocene forest history.

The diurnal temperature range (DTR) is an important climate-change variable and, until recently, it was derived from station observations of surface air temperature (T a ). Station-based observations are sparse and unevenly distributed, making the use of satellites an attractive option for evaluating DTR. In this study, satellite-based estimates of DTR are evaluated against ground measurements of surface skin temperature (T s ) and compared with weather-station observations based on T a . Geographical and seasonal differences were identified in both ground-and satellite-derived DTRs. Estimates of DTR from station-observed air temperature represent all-sky conditions while satellite estimates of DTR from surface skin temperature represent clear conditions only. For both station observations and satellite estimates, DTRs at rural locations tend to be larger than at urban sites. The DTRs based on T s are larger than those derived from T a under both all and clear-sky conditions. Clouds tend to reduce the magnitude of the DTR. The station-observed DTRs are found to be larger in summer than in winter over the entire U.S. The satellite-derived DTRs are larger in spring and fall than in winter and summer over the eastern U.S., while they are larger in spring and summer than in fall and winter over the western part. Evapotranspiration from land vegetation and the effects of water-vapor radiative forcing have a major effect on the detected spatial and seasonal variations in the DTR patterns. Index Terms-Diurnal temperature range (DTR), effects of evapotranspiration, satellite-derived DTR, station observations of DTR, water-vapor radiative forcing (WRF) on DTR. I. INTRODUCTION T HE DIURNAL temperature range (DTR) is an important index of climate change [1] because DTR is susceptible to a variety of environmental effects including water vapor, cloudiness, and urban influences [2]. Until recently, most information on this parameter came from station air temperature (T a ) observations. During recent decades, DTR has been observed to decrease over the U.S. [3], [4] as well as over the globe [1], [5]. Kalnay and Cai [4] explain that this may be due to the impact of land-use changes, such as urbanization and agricultural development, while Trenberth [6] and Stone and Weaver [7] point out that changes in clouds and surface Manuscript

Series of tethered balloon soundings of temperature and humidity in Austria’s Gruenloch basin (floor elevation 1270 m MSL) on two June days showed that the water vapor mixing ratio fell by 2–3 g kg−1 overnight as dew or frost formed in the basin. After sunrise, the basin atmosphere remoistened as higher humidity was brought down into the basin from above and as evapotranspiration occurred from the basin floor and sidewalls. The latent heat released at night by the dewfall/frostfall was 33%–53% of the overall observed basin sensible heat loss, illustrating the important role of dew and frost formation on the nighttime heat budget of the basin atmosphere. An energy budget equation illustrates the decreasing importance of the latent heat release on the overall basin heat budget as ambient temperatures fall from summer to winter. Because the diurnal temperature range is frequently larger than the late-afternoon dewpoint depression, fog and clouds often form in this basin. The extreme te...

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The rationale for this study lies in the fact that the mid-latitude regions are largely affected by the global and regional scale circulation changes. Moreover, earlier studies emphasize that the variation in atmospheric concentration of heat-trapping gases, cloud amount and moisture contents produce substantial regional climatic changes. Therefore, it is of significant practical importance to analyze the sensitivity of mid-latitude regions to anthropogenic forcing, especially, the CO2 radiative forcing. This study assesses the role of CO2 radiative forcing in causing asymmetric diurnal changes over the mid-latitude semi-dry region using an idealized experiment conducted by single column (1-D) Radiative-Convective Model (RCM) of the diurnal cycle. The model is capable enough in highlighting the main features responsible for the observed diurnal asymmetry in the ground temperature. A significant decrease in the Diurnal Temperature Range (DTR) is observed in this region under doubled CO2 forcing. The amount of thermal radiation trapped by CO2 forcing in the presence of water vapors plays a key role in surface temperature changes and resultant decreasing of the DTR. It is further found that CO2 induced climatic feedbacks are equally important in producing diurnal asymmetry. To better understand the complete picture of the DTR variability, one needs to explore all the possible forcing and feedbacks such as caused by aerosols, water vapors and cloud amount along with their distribution in the atmosphere.

Observations indicate that greenhouse induced 20th century warming has been strongly modulated by variations in surface solar radiation. Between the 1950s and 1980s declining surface solar radiation ("global dimming") likely caused a dampening of global warming, whereas increasing surface solar radiation ("brightening") may have contributed to the rapid warming in the last two decades and possibly also the first half