Changes in diurnal temperature range in Bangladesh during the time period 1961–2008 Shamsuddin Shahid ⁎, Sobri Bin Harun, Ayob Katimon Department of Hydraulics and Hydrology, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM, Johor, Malaysia article info abstract Article history: Received 13 July 2011 Received in revised form 10 July 2012 Accepted 10 July 2012 Available online 20 July 2012 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. © 2012 Elsevier B.V. All rights reserved. Keywords: Diurnal temperature range Climate change Trend analysis Bangladesh 1. Introduction Diurnal temperature range (DTR) is a meteorological indicator associated with global climate change. Karoly et al. (2003) and Braganza et al. (2003) reported that a set of multiple climate indices, that are independent in internal climate variations, shows a coherent response to greenhouse forcing, and provides additional information for the detection and attribution of climate change in much the same manner as spatial fingerprints of climate change. Braganza et al. (2004) proposed that changes in daily maximum and minimum temperatures provide more information than the mean alone because trends in mean surface temperature can be due to changes in either maximum or minimum temperature, or relative changes in both. Therefore, the diurnal temperature range, i.e. the difference between maximum and minimum temperatures, may be useful in defining a signature of observed climate change that is less likely to show a common response to different radiative forcing mechanisms. DTR is considered as an important index of climate change and is receiving consider- able attention in various regions of the globe in recent times (Plummer et al., 1995; Kaas and Frich, 1995; Razuvaev et al., 1995; Price et al., 1999; Roy and Balling, 2005; Englehart and Douglas, 2005; Makowski et al., 2008; Jhajharia and Singh, 2011; Sang, 2012). It has been observed that global averaged DTR has decreased substantially during 1950–1990 (Karl et al., 1991; Easterling et al., 1997). The decrease in DTR has regional and seasonal characteristics. For most parts of the world, nighttime temperature has risen faster than the daytime temperature, producing a smaller DTR (Karl et al., 1991). However, in some places, daytime temperature has decreased while nighttime temperature has increased (Karl et al., 1993; Kukla and Karl, 1993). Though a number of studies have been carried out in the recent years on climate variability in Bangladesh (Rahman et Atmospheric Research 118 (2012) 260–270 ⁎ Corresponding author. Tel.: +60 7 5531624; fax: + 60 7 5566157. E-mail address: sshahid_ait@yahoo.com (S. Shahid). 0169-8095/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2012.07.008 Contents lists available at SciVerse ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos