Decrease In Diurnal Temperature Range Research Articles

Contributions of radiative factors to enhanced dryland warming over East Asia

AbstractEnhanced near‐surface atmospheric warming has occurred over East Asia in recent decades, especially in drylands. Although local factors have been confirmed to provide considerable contributions to this warming, such factors have not been sufficiently analyzed. In this study, we extracted the radiatively forced temperature (RFT) associated with the built‐up greenhouse gases, aerosol emission, and various other radiative forcing over East Asia and found a close relationship between RFT and CO2. In addition, using climate model experiments, we explored the responses of temperature changes to black carbon (BC), CO2, and SO4 and found that the enhanced dryland warming induced by CO2 had the largest magnitude and was strengthened by the warming effect of BC. Moreover, the sensitivity of daily maximum and minimum temperature changes to BC, CO2, and SO4 was examined. It showed asymmetric responses of daily maximum and minimum temperature to radiative factors, which led to an obvious change of diurnal temperature range (DTR), especially in drylands. The DTR's response to CO2 is the most significant. Therefore, CO2 not only plays a dominant role in enhanced warming but also greatly affects the decrease of DTR in drylands. However, the mechanisms of these radiative factors' effects in the process of DTR change are not clear and require more investigation.

Impacts of climate change on cotton yield in China from 1961 to 2010 based on provincial data

To develop scientific countermeasures, the impacts of climate change on cotton yield during 1961–2010 in three major cotton-producing regions of China were studied by using the available provincial data. The results indicate that (1) a rise in average temperature increased the cotton yield in most provinces of Northwest China and the Yellow River valley; however, the rise in average temperature decreased the cotton yield in the Yangtze River valley. Moreover, cotton production across the entire study region was reduced by approximately 0.1% relative to the average during 1961–2010. (2) A decrease in diurnal temperature range (DTR) reduced cotton yield in some provinces, while a beneficial DTR effect was observed in the other provinces. Changes in DTR resulted in an average decrease in production by approximatly 5.5% across the entire study region. (3) A change in the amount of precipitation increased the cotton yield in some provinces; however, it caused a decrease in other provinces. The decrease in average production due to the change in precipitation was approximately 1.1%. We concluded that the changes in temperature and precipitation decreased cotton yields in China, while beneficial effects of temperature and precipitation existed in the cotton-growing regions of Northwest China during 1961–2010.

Spatiotemporal change of diurnal temperature range and its relationship with sunshine duration and precipitation in China

AbstractWe examined the spatiotemporal variation in diurnal temperature range (DTR) and discussed the reasons for the changes of DTR in China based on data from 479 weather stations from 1962 to 2011. Results showed that DTR decreased rapidly (0.291°C/decade) from 1962 to 1989 due to slightly decreased Tmax and significantly increased Tmin, but the decrease in DTR has stopped since 1990 as Tmax and Tmin kept pace with each other. During 1990–2011, DTR remained trendless, with slight increase in the 1990s and slight decrease after 2000. During the whole study period from 1962 to 2011, DTR decreased at a rate of 0.157°C/decade nationally. Spatially, decreases in DTR were greatest in Northeast China and lowest in Southwest China with a transect running from northeast to southwest showing the decreasing trends change from high to low. Seasonally, DTR decreases were greatest in winter and lowest in summer, and the magnitudes of decrease reduced from the north to south of China. The changes in DTR were closely correlated with changes in sunshine duration (SD) in China except the Tibetan Plateau, suggesting that SD decrease is an important contributor to the decrease of DTR through its influence on Tmax. In addition to the contribution of SD decrease, the increasing of precipitation played an important role in DTR decrease in Northwest China, the most arid region of China. It appeared that changes of cloud cover (CC) were not the reasons for DTR changes in the past 50 years as CC has decreased during the study period.

Impacts of climate change on maize and winter wheat yields in China from 1961 to 2010 based on provincial data

SUMMARYThe impacts of climate change on maize and winter wheat yields in China from 1961 to 2010 were studied in the current paper, based on provincial data. The results indicated that rising average temperatures resulted in decreased maize yield in most of the study regions, and reduced maize production at a national scale by c. 3·4% relative to the average from 1961 to 2010. Moreover, the warming resulted in a decrease of winter wheat yield in the Huang-Huai-Hai and southwest regions and led to an overall loss in production of c. 5·8% at a national scale. The decrease of diurnal temperature range (DTR) affected maize yield adversely in the west and central regions, but a beneficial DTR effect was observed in the other provinces. The changes in DTR resulted in increased maize production at a national scale by c. 0·6%. However, the generally decreasing trends for DTR resulted in an increasing winter wheat yield in the northwest and south regions but a decreasing yield in the other provinces, and the production of winter wheat at a national scale was reduced by c. 2·9% because of changes in DTR. Changes in precipitation increased maize and winter wheat yields in some provinces but reduced crop yield in others. There was no significant effect of precipitation on maize production at a national scale, but the contribution of precipitation change reached c. 1·6% for winter wheat production.

Recent trends in daily temperature extremes over northeastern China (1960–2011)

Based on long-term, high-quality, and homogenous daily maximum and minimum temperature of 70 meteorological stations spanning the period from 1960 to 2011, the spatial and temporal characteristics of extreme temperature events in northeastern China have been investigated. A total of 14 indices are used to assess changes in extreme temperature distributions. All the temperature-based indices show patterns consistent with a general warming trend. The regional occurrence of the increase in warm nights (TN90p: 2.17 days/decade) and warm days (TX90p: 0.97 days/decade), and decrease in cool nights (TN10p: −1.80 days/decade) and cool days (TXx: −0.86 days/decade) was detected in the past 52 years. Moreover, the trend magnitudes in cold/warm nights are larger than those in cold/warm days, which indicate that trends in minimum temperature extremes are more rapid than trends in maximum temperature extremes, consistent with a long-term decrease in DTR. The other indices, including TNn, TNx, SU25, TR20, FD0, ID0, GSL, and DTR, show statistically significant changes except for Maximum and minimum values of maximum daily temperatures (TXx and TXn) which have statistically insignificant slopes at individual stations and in regional mean trend. For the majority of stations, significant increases are detected for heat related extremes such as summer days and tropical nights (SU25 and TR20) as well as for maximum and minimum values of minimum daily temperatures (TNn and TNx); With the exception of diurnal temperature range (DTR) and maximum daily maximum temperature (TXx), the other indices strongly correlate with annual mean temperature. In addition, there are high correlations among warm indices and among cold ones, respectively.

Analysis of temperature variability over north-west part of India for the period 1970–2000

The main aim of this study was to investigate the temporal trends in maximum (T max), minimum (T min) temperature and diurnal temperature range (DTR) at annual and seasonal basis for seven sites in north-west region of India. The analysis was carried out for period of 31 years (1970–2000). The magnitude of trends and their significance were determined using Sen’s slope and Mann–Kendall methods. Additionally, persistence analysis of annual average DTR and mean temperature (T mean) has been carried out using cumulative annual mean (CAM) method. It is clear from the results that during last three decades the majority of sites showed decrease/(increases) in DTR/(T min) trends for seasonal and annual time scale. While, trends in annual and seasonal T max were observed insignificant. CAM analysis demonstrated that T mean has increased consistently since 1987–1988 onwards at majority of the sites. Further, correlation analysis revealed that rainfall along with potential evapotranspiration may be one of the important reasons for observed DTR decrease.

Change point analysis of precipitation indices of Western Canada

The Markov chain statistical technique was employed to fill few missing values of daily precipitation observed at nine long-term (≥50 years of data) climate stations of Western Canada. Statistical properties of the gap filled precipitation data are compared with those of the original data to ensure that this approach preserves the statistical characteristics of the historical data. After gap filling missing data, 10 precipitation indices that represent magnitude and frequency of precipitation properties were computed from those 9 stations and the other 20 stations without missing records. Next, the Wilcoxon rank-sum test was used to detect possible change points of these precipitation indices. Based on the analysed results, there had been an increasing trend in the maximum number of consecutive wet days and the annual maximum 1-day precipitation and a decrease in the maximum number of consecutive dry days over most of British Columbia (BC). The annual total precipitation index of many stations had increased in southern BC and decreased in central parts of Canadian Prairies. Similar change was detected in the number of days when precipitation is equal and greater than 10 or 20 mm, and indices for the annual monthly maximum 1-day precipitation – precipitation that exceeds the 95 and 99 percentiles – and the simple precipitation intensity index. On the basis of the above results, the diurnal temperature range (DTR) of Western Canada has decreased, and predominant negative correlations between precipitation indices and DTR, it seems that Western Canada has generally become wetter since the middle of the 20th century partly because increase in the minimum daily temperature has been higher than the increase in the maximum daily temperature, leading to a decrease in DTR, which is likely related to climatic warming.

Factors Contributing to the Spatial Variability of Satellite Estimates of Diurnal Temperature Range in the United States

Diurnal temperature range (DTR) is an important index of climate change that can be affected by many environmental factors. The impact of each of these factors on DTR is still much debated. We show that the cooling effect due to transpiration from dense vegetation on land surface temperature (LST) is more evident during daytime than nighttime, which makes the difference between daily maximum and minimum LSTs (LSTmax - LSTmin) or DTR decrease with vegetation; this is seen only during the growing season. DTR drops with soil moisture (SM) for all seasons. The effect of water vapor (WV) radiative forcing makes DTRs decrease during the warm seasons (summer and fall) and may have affected most significantly the dip of DTR during summer over the southern two-thirds of the eastern United States. During summer, the effects of vegetation and WV on the decrease in DTR are more significant than other factors such as SM and aerosols.

Impacts of Climate Change on Rice Yield in China From 1961 to 2010 Based on Provincial Data

The impacts of climate change on rice yield in China from 1961 to 2010 were studied in this paper, based on the provincial data, in order to develop scientific countermeasures. The results indicated that increase of average temperature improved single cropping rice production on national level by up to 11% relative to the average over the study period, however, it resulted in an overall loss of double cropping rice by up to 1.9%. The decrease of diurnal temperature range (DTR) in the major producing regions caused the decrease by up to 3.0% for single cropping rice production and 2.0% for double cropping rice production. Moreover, the contribution of precipitation change reached about 6.2% for single cropping rice production, but no significant effect for double cropping rice production in recent 50 years.

Analysis of diurnal air temperature range change in the continental United States

Diurnal temperature range (DTR) is an important indicator for climate change. In this paper, diurnal air temperature range variations of the continental United States over the past one hundred years were investigated to discover the temporal trend and spatial patterns. While the annual mean DTR of the United States has steadily decreased during the past decades, it is found that the decreased amplitude has spatial and seasonal patterns. Seasonal and spatial variations of DTR were analyzed for the four regions, northeastern, northwestern, southeastern, and southwestern. Fall and summer witnessed a significant decrease in DTR in all regions. Spring and winter, on the other hand, have experienced much smaller decreases. Temporal trend and spatial patterns of daily maximum and minimum temperatures were also investigated to gain insight of DTR change.

Late Winter Sea Ice in the Bering Sea: Predictor for Maize and Rice Production in Northeast China

AbstractIn this research, the linkage between late winter Bering Sea ice and maize/rice yields in northeastern China (NEC) is investigated. Results show that such ice influences NEC crop production and thus can be employed to predict harvest amounts. Further investigation reveals that positive anomalies of late winter sea ice cover can persist until spring and that spring sea ice can strengthen North Pacific Oscillation (NPO) positive-phase patterns, and vice versa. NPO significantly affects sea surface temperature (SST) over the North Pacific Ocean through sea–air interaction—in particular, in the Kuroshio region—that may persist until summer. In association with the positive SST anomalies, the polar vortex weakens and the western Pacific subtropical high strengthens, resulting in the convergence of southern and northern air masses over NEC. Moreover, both the southerly flow along the western flank of the western Pacific subtropical high and the easterly flow from the Japan Sea and the central Pacific region supply more water vapor transport; thus, an anomalous water vapor convergence center appears in NEC. With the anomalous updrafts, NEC exhibits positive precipitation anomalies. The greenhouse effect of water vapor results in an increase in minimum temperature, thereby leading to a decrease in diurnal temperature range (DTR). This increase in minimum temperature and decrease in DTR are primary factors favoring increases in rice and maize yields, respectively.

The diurnal temperature range in the CMIP5 models

This paper analyzes the diurnal temperature range (DTR) over land in simulations of the recent past and in future projections by 20 models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5). The annually averaged DTR is evaluated for the present-day climate using two gridded datasets (HadGHCND and CRU). The DTR varies substantially between different CMIP5 models, particularly in the subtropics, and is generally underestimated. In future projections of the high emission scenario RCP8.5, the models disagree on both the sign and the magnitude of the change in DTR. Still, a majority of the models project a globally averaged reduction in the DTR, with an increase over Europe, a decrease over the Sahara desert and a substantial decrease in DTR at high latitudes in winter. The general DTR reduction is partly linked to the enhancement of the downwelling clear sky longwave radiation due to greenhouse gases. At high latitudes in winter, the decrease in DTR seems to be enforced by an increase in cloudiness, but in most other regions counteracted by decreases in cloud fraction. Changes in the hydrological cycle and in the clear sky shortwave radiation also impact the DTR. The DTR integrates many processes and neither the model differences in the DTR nor in the change in DTR can be attributed to a single parameter. Which variables that impact the model discrepancies vary both regionally and seasonally. However, clouds seem to matter in most regions and seasons and the evaporative fraction is important in summer.

Impacts of Regional-Scale Land Use/Land Cover Change on Diurnal Temperature Range

The NCAR Community Atmosphere Model (CAM4.0) was used to investigate the climate effects of land use/land cover change (LUCC). Two simulations, one with potential land cover without significant human intervention and the other with current land use, were conducted. Results show that the impacts of LUCC on diurnal temperature range (DTR) are more significant than on mean surface air temperature. The global average annual DTR change due to LUCC is −0.1°C, which is three times as large as the mean temperature change. LUCC influences regional DTR as simulated by the model. In the mid-latitudes, LUCC leads to a decrease in DTR, which is mainly caused by the reduction in daily maximum temperature. However, there are some differences in the low latitudes. The reduction in DTR in East Asia is mainly the result of the decrease in daily maximum temperature, while in India, the decrease in DTR is due to the increase in daily minimum temperature. In general, the LUCC significantly controls the DTR change through the changes in canopy evaporation and transpiration. CitationHua, W.-J., and H.-S. Chen, 2013: Impacts of regional-scale land use/land cover change on diurnal temperature range. Adv. Clim. Change Res., 4(3), doi: 10.3724/SP.J.1248.2013.166.

Variability and trend of diurnal temperature range in China and their relationship to total cloud cover and sunshine duration

Abstract. This study aims to investigate the effect of total cloud cover (TCC) and sunshine duration (SSD) in the variation of diurnal temperature range (DTR) in China during 1954–2009. As expected, the inter-annual variation of DTR was mainly determined by TCC. Analysis of trends of 30-year moving windows of DTR and TCC time series showed that TCC changes could account for that of DTR in some cases. However, TCC decreased during 1954–2009, which did not support DTR reduction across China. DTRs under sky conditions such as clear, cloudy and overcast showed nearly the same decreasing rate that completely accounted for the overall DTR reduction. Nevertheless, correlation between SSD and DTR was weak and not significant under clear sky conditions in which aerosol direct radiative effect should be dominant. Furthermore, 30–60% of DTR reduction was associated with DTR decrease under overcast conditions in south China. This implies that aerosol direct radiative effect appears not to be one of the main factors determining long-term changes in DTR in China.

Diurnal temperature range variation and its causes in a semiarid region from 1957 to 2006

ABSTRACTThe diurnal temperature range (DTR) is an important indicator of climate change, and it has decreased worldwide since the 1950s, particularly over arid and semiarid regions. This study analyses the effect of meteorological and anthropogenic factors on DTR variation to investigate the possible causes of DTR decreases in semiarid climates. The study region is located in northeast China, and the study period is from 1957 to 2006. There are three main results. First, the rate of decrease in the DTR is −1.24 K per 50 years. This decrease is mainly attributed to the increasing daily minimum temperature rate (Tmin, 2.24 K per 50 years), which is greater than the change in the daily maximum temperature (Tmax, 1.00 K per 50 years). Second, sunshine duration (SD) appears to be the most significant meteorological factor that determines the DTR through downward shortwave radiation (Rsw,d) and surface soil moisture (SM). The effect of Rsw,d is larger for Tmax than for Tmin; therefore, the decrease in Rsw,d results in a smaller increase in Tmax than in Tmin. On the other hand, the increase in SM can strengthen daytime latent heat release, and the increase in Tmax is then slowed because of the cooling effect of evaporation. The precipitation values and the leaf area index show a negative correlation with the DTR, whereas the cloud amount and the relative humidity appear not to be main causes of the DTR decrease in this region. Finally, atmospheric aerosols can reduce the SD by 0.27 h year–1 by decreasing atmospheric transparency, as indicated by an analysis of the Total Ozone Mapping Spectrometer Aerosol Index from 1979 to 2005. The decrease in direct solar radiation is the main cause of decreases in Rsw,d. These findings will provide references for DTR variation studies in similar climates.

Potential evapotranspiration and its attribution over the past 50 years in the arid region of Northwest China

Evaporation paradox and its attribution have become a hot research topic in hydrology in recent years. This study estimates the potential evapotranspiration (ET0) using modified Penman–Monteith method and analyzes the corresponding trend attribution based on the long-term meteorological data collected at 81 ground-based meteorological stations in Northwestern arid region of China during the period 1958–2010. The analysis results show: (1) The ET0 has exhibited an obvious decreasing trend until the early 1990s; however, the downward trend has been reversed to an upward trend after then. (2) Decrease in diurnal temperature range (DTR) and wind speed (WS) may lead to the decrease of ET0 during 1956–1993. The change of dominant factors in the ET0 trend has differences after the early 1990s; observed increase in WS is the primary factor contributing to the reversion of ET0. Copyright © 2012 John Wiley & Sons, Ltd.

Changes in diurnal temperature range in Bangladesh during the time period 1961–2008

Diurnal temperature range (DTR) is a meteorological indicator independent of internal climate variation and therefore, considered as a signature of observed climate change. It has been observed that global averaged DTR has decreased significantly in the last fifty years. However, the change in DTR has regional and seasonal characteristics. A study has been carried out in this paper to analyze the spatial and seasonal patterns in the trends of DTR in Bangladesh. Daily temperature data from 18 stations for the time period 1961–2008 has been used for the study. The result shows that both mean minimum and mean maximum temperatures of Bangladesh have increased significantly at a rate of 0.15°C/decade and 0.11°C/decade, respectively. However, the increase of minimum temperature compared to maximum temperature is not high enough to cause a significant change in average diurnal temperature range in Bangladesh. Seasonal DTR trends show a decrease in winter and pre-monsoon DTR, and an increase in monsoon DTR. Spatial distribution of DTR trends shows an increase of annual DTR in the southeastern coastal stations and decrease in the northern stations of Bangladesh. Significant negative relation between rainfall and DTR is observed in Bangladesh. Regression analysis shows that an annual increase of 1% of rainfall is correlated with a decrease of DTR by 0.1°C.

Changes in daily temperature and precipitation extremes in the Yellow River Basin, China

Spatiotemporal changes in climatic extremes in the Yellow River Basin from 1959 to 2008 were investigated on the basis of a suite of 27 climatic indices derived from daily temperature and precipitation data from 75 meteorological stations with the help of the Mann–Kendall test, linear regression method and GIS technique. Furthermore, the changes in the probability distribution of the extreme indices were examined. The results indicate: (1) The whole basin is dominated by significant increase in the frequency of warm days and warm nights, and dominated by significant decrease in the frequency of cold days and cold nights. Although trends in absolute temperature indices show less spatial coherence compared with that in the percentile-based temperature indices, overall increasing trends can be found in Max Tmax (TXx), Min Tmax (TXn), Max Tmin (TNx) and Min Tmin (TNn). (2) Although the spatial patterns and the number of stations with significant changes for threshold and duration temperature indices are also not identical, general positive trends in warm indices (i.e., summer days (SU25), tropical nights (TR20), warm spell duration indicator and growing season length) and negative trends in cold indices (i.e., frost days, ice days and cold spell duration indicator) can be found in the basin. Annual nighttime temperature has increased at a faster rate than that in daytime temperature, leading to obvious decrease in diurnal temperature range. (3) The changes in precipitation indices are much weaker and less spatially coherent compared with these of temperature indices. For all precipitation indices, only few stations are characterized by significantly change in extreme precipitation, and their spatial patterns are always characterized by irregular and insignificant positive and negative changes. However, generally, changes in precipitation extremes present drying trends, although most of the changes are insignificant. (4) Results at seasonal scale show that warming trends occur for all seasons, particularly in winter. Different from that in other three seasons, general positive trends in max 1-day precipitation (Rx1DAY) and max 5-day precipitation (Rx5DAY) are found in winter. Analysis of changes in probability distributions of indices for 1959–1983 and 1984–2008 indicate a remarkable shift toward warmer condition and a less pronounced tendency toward drier condition during the past decades. The results can provide beneficial reference to water resource and eco-environment management strategies in the Yellow River Basin for associated policymakers and stakeholders.

Reduced diurnal temperature range does not change warming impacts on ecosystem carbon balance of Mediterranean grassland mesocosms

Daily minimum temperature (Tmin) has increased faster than daily maximum temperature (Tmax) in many parts of the world, leading to decreases in diurnal temperature range (DTR). Projections suggest that these trends are likely to continue in many regions, particularly in northern latitudes and in arid regions. Despite wide speculation that asymmetric warming has different impacts on plant and ecosystem production than equal-night-and-day warming, there has been little direct comparison of these scenarios. Reduced DTR has also been widely misinterpreted as a result of night-only warming, when in fact Tmin occurs near dawn, indicating higher morning as well as night temperatures. We report on the first experiment to examine ecosystem-scale impacts of faster increases in Tmin than in Tmax, using precise temperature controls to create realistic diurnal temperature profiles with gradual day–night temperature transitions and elevated early morning as well as night temperatures. Studying a constructed grassland ecosystem containing species native to Oregon, USA, we found that the ecosystem lost more carbon at elevated than ambient temperatures, but remained unaffected by the 3 °C difference in DTR between symmetric warming (constantly ambient + 3.5 °C) and asymmetric warming (dawn Tmin = ambient + 5 °C, afternoon Tmax = ambient + 2 °C). Reducing DTR had no apparent effect on photosynthesis, probably because temperatures were most different in the morning and late afternoon when light was low. Respiration was also similar in both warming treatments, because respiration temperature sensitivity was not sufficient to respond to the limited temperature differences between asymmetric and symmetric warming. We concluded that changes in daily mean temperatures, rather than changes in Tmin/Tmax, were sufficient for predicting ecosystem carbon fluxes in this reconstructed Mediterranean grassland system.

Precipitation and temperature trends for the Southwest China: 1960–2007

AbstractDaily temperature and precipitation data from 136 stations of Southwest China (SWC) during the last five decades, from 1960 to 2007, were analysed to determine the spatial and temporal trends by using the Mann–Kendall trend test. Results show that SWC has become warmer over the last five decades, especially in the recent 20–25 years. The increasing trends in winter months are more significant than those in the months of other seasons, and spatially Tibet, Hengduan mountains area and west Sichuan Plateau have larger temperature trend in magnitude than the other regions have. A downward trend was detected in Sichuan Basin also, but the region with cooler temperature was shrinking due to the statistically significant increasing trend of temperature after 1990s. Both annual and seasonal means of daily maximum and minimum temperatures show an increasing trend, but trend magnitude of minimum temperature was larger than that of maximum temperature, resulting in the decrease of diurnal temperature range for SWC in the last 50 years. Annual precipitation showed slightly and statistically insignificant increasing trend, but statistically significant increasing trend has been detected in winter season while autumn witnessed a statistically significant decreasing trend. The results could be a reference for the planning and management of water resources under climate change. Copyright © 2010 John Wiley & Sons, Ltd.