Historical trends and variability of temperature extremes in two climate vulnerable regions of Bangladesh (original) (raw)
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Extreme temperature is the key indicator of extreme climatic events. The goal of this research was to better understand the long-term trends and shifting behaviors associated with Bangladesh's record-breaking high temperatures in the country's atmosphere. Data from 26 Bangladeshi meteorological stations collected between 1981 and 2018 was analyzed with RClim-Dex. The annual count of warm (cold) spell duration increased, according to the findings (decrease). In the coastal regions, this rising temperature trend is more pronounced. There were longer (shorter) periods of warm (cold) weather in the twentieth century than there were in the previous decade. As a result, the length of warm (cold) spells has become longer since the beginning of the twenty-first century, as compared to the last quarter of the twentieth century. There is little fluctuation in diurnal temperatures, but they are getting smaller and smaller. There is a 13% decrease in the Cold Spell Duration Indicator (CSDI), which indicates that we are in for a long, cold winter. At a rate of 14% per year, the Warm Spell Duration Indicator (WSDI) annual count suggests an extremely hot summer is imminent. Diurnal temperature range (DTR) values decreased by 1.1% year-round, raising the specter of climate extremes like the CSDI and WSD. An increasing (decreasing) trend in indicators of how long hot (cold) weather lasts indicates an increase (decrease) in Bangladesh's warm atmosphere. As a result, an increase in the number of extreme weather events, particularly along the coasts, should be expected across the country.
Spatial and sequential variability of extreme temperature events enthral the scientific community owing to their significant impact on global climate change. This study analysed trends in monthly data of temperature extremes of 23 meteorological stations of Bangladesh using Mann-Kendall test. Most of the stations showed significant increasing trend for both temperature extremes on monthly and annual scales. Most of the change points were detected during the last four decades and showed an upward trend. The results obtained from Sen's estimator vouchsafed that magnitudes of trend ranged from 0.007ºC to 0.034ºC per year and 0.014ºC to 0.049ºC per year for minimum and maximum temperature, respectively. The upward trend in both extreme temperatures pointed to global warming. The maximum number of significant trends was observed in monsoon and post-monsoon seasons for average maximum temperature. The upward trend in the monsoon and post-monsoon season may cause the drought and late winter in Bangladesh.
Trends and Spatial Heterogeneity of Climate Extremes in the Southwestern Region of Bangladesh
Chinese Journal of Urban and Environmental Studies, 2023
This study attempts to investigate the climatic variability in the southwestern area of Bangladesh focusing on temperature and precipitation extremes. Long-term daily records of temperature and precipitation from six weather stations spread over the study area were analyzed. A total of 20 yearly indices were calculated and testified for the trends with the Mann-Kendal test and Sen's estimator of slope at a 95% confidence interval. Moreover, one-way ANOVA and Tukey-Kramer post-hoc tests were applied to verify the spatial heterogeneity of the climatic indices among the meteorological stations. Findings revealed that Khulna is the worst affected area with significant changes in 12 climatic indices. Jessore and Faridpur followed Khulna with significant changes in 10 and 9 indices, respectively. Among the indices, significant changes in TN10p (frequencies of daily minimum temperature event that falls below the 10th percentile value), TX10p (frequencies of daily maximum temperature event that falls beyond the 10th percentile value), CSDI (cold spell duration indicator), and CDD (consecutive dry day) are the most common phenomenon in the studied region. Five out of six stations have been experiencing significant increasing trends for TN10p. That indicates an overall increase of extreme cold day frequencies in the area. Khulna station showed shreds of evidence of extreme cold temperature instances with a statistically significant fall in the minimum value of the yearly minimum temperatures (TNn). Besides, Khulna also experienced a statistically significant fall in the minimum value of the yearly maximum temperatures. Consistently, the area showed a significant trend of wider cold spells. Similarly, the extremely warm day frequencies have also been increasing significantly for the Khulna, Jessore, and Faridpur areas. Therefore, it is evident that the studied area has been experiencing temperature extremes. On the other hand, precipitation extremes are apparent for only Khulna and Jessore. Both these stations showed increasing trends in heavy precipitation events and wet spells (consecutive precipitation days). ANOVA outcome suggests that the study area has significant spatial heterogeneity in climatic indices. Precipitation indices show high spatial heterogeneity than those of temperature. Among the meteorological stations, Mongla and Ishwardi show the maximum departure than those of others. This study may help policy-makers, researchers, and academicians to take proper initiatives to reduce the impacts of changing climatic parameters in the coastal areas of Bangladesh.
Journal of Water and Climate Change, 2021
This study was intended to evaluate the variability and trends of climate extremes by incorporating daily data from Chattogram station and from the high-resolution Coordinated Regional Climate Downscaling Experiment (CORDEX) for two different time series. Here, we also focused on evaluating the performance of the selected RCMs (CanESM2, CSIRO, and GFDL from CORDEX) using Taylor diagrams and heat map analysis. Twenty-two extreme climate indices from ETCCDI were computed for 1950–1989 and 1990–2020 periods. Mann–Kendall and Sen's slope test were performed to estimate the trends from the indices from both station and RCMs data. Highly significant increasing trend for the warm days and warm nights’ frequencies were found, whereas, the frequency of cold days and cold nights indicated significantly decreasing trend. On the other hand, mild increasing trend in 1-day and 5-day maximum rainfall was detected. Also, the average annual precipitation has increased by 6% from the 1950–1989 to...
Trend analysis of maximum, minimum, and average temperatures in Bangladesh: 1961–2008
Theoretical and Applied Climatology, 2014
The present study is about the analysis of mean maximum and mean minimum temperatures carried out on annual, seasonal, and monthly timescales examining the data from 15 meteorological stations in Bangladesh for the period 1961-2008. Various spatial and statistical tools were used to display and analyze trends in temperature data. ArcGIS was used to produce the spatially distributed temperature data by using Thiessen polygon method. The nonparametric Mann-Kendall test was used to determine whether there is a positive or negative trend in data with their statistical significance. Sen's method was also used to determine the magnitude of the trends. The results reveal positive trends in annual mean and mean maximum temperatures with 95 % significance. Trend test reveals that the significant positive trend is found in June to November in case of mean maximum temperature, but according to the mean minimum temperature, the situation is different and a significant positive trend was found from November to February. The analysis of the whole record reveals a tendency toward warmer years, with significantly warmer summer periods and slightly colder winters. These warming patterns may have important impacts on energy consumption, water supply, human health, and natural environment in Bangladesh.
Appraising the historical and projected spatiotemporal changes in the heat index in Bangladesh
Theoretical and Applied Climatology
Climate change-derived extreme heat phenomena are one of the major concerns across the globe, including Bangladesh. The appraisal of historical spatiotemporal changes and possible future changes in heat index (HI) is essential for developing heat stress mitigation strategies. However, the climate-health nexus studies in Bangladesh are very limited. This study was intended to appraise the historical and projected changes in HI in Bangladesh. The HI was computed from daily dry bulb temperature and relative humidity. The modified Mann-Kendal (MMK) test and linear regression were used to detect trends in HI for the observed period (1985-2015). The future change in HI was projected for the mid-century (2041-2070) for three Representative Concentration Pathway (RCP) scenarios, RCP 2.6, 4.5, and 8.5 using the Canadian Earth System Model Second Generation (CanESM2). The results revealed a monotonic rise in the HI and extreme caution conditions, especially in the humid summer season for most parts of Bangladesh for the observed period (1985-2015). Future projections revealed a continuous rise in HI in the forthcoming period (2041-2070). A higher and remarkable increase in the HI was projected in the northern, northeastern, and south-central regions. Among the three scenarios, the RCP 8.5 showed a higher projection of HI both in hot and humid summer compared to the other scenarios. Therefore, Bangladesh should take region-specific adaptation strategies to mitigate the impacts of HI.
Theoretical and Applied Climatology
Global mean temperature is continuously rising and causing changes in the extreme climatic events. Following these changes, climate extremes-the rare events that reside in the tail of the distribution of essential climate variables-are expected to be further intensified, more frequent, and prolonged. Changes in extremes would vary spatially from region to region and thus need regional assessment for future adaptation planning. This study assesses the climate extremes at 1.5°C, 2°C, and 4°C of global warming over Bangladesh which is one of the most vulnerable countries to climate change. Future changes in climate extremes are assessed using a subset of extreme temperature and precipitation indices devised by Expert Team on Climate Change Detection and Indices (ETCCDI). Projections from high-resolution regional climate model ensembles are used to derive extreme climate indices. Our analysis shows overall upward changes in warm indices and downward changes in cold indices at higher specific warming levels. We found a much higher increase in extreme rainfall compared with the annual total rainfall. Increasing variability of rainfall indices is found at higher specific warming levels. Our analysis also suggests a higher increase of temperature during the winter and post-monsoon seasons, as well as an increase in the 1-day and 5-day maximum rainfall during pre-and post-monsoon seasons. A significant regional difference is found in almost all the rainfall indices. The forecasted increase of extreme rainfall and consecutive dry days (CDD) over the northeast region indicates a possibility of an increase of flash floods in the future. Moreover, the increase in the extreme rainfall over the southeast region will increase the chances of landslides. Highlights • Spatiotemporal changes in extreme climate indices over Bangladesh at 1.5, 2, and 4°C SWLs are studied. • Bias-corrected high-resolution multi-model ensemble projections are considered over this region. • Post-monsoon and winter will likely be warmer in the future than other seasons. • Rainfall variability is likely to be increased in the future at higher SWLs. • The highest increase in extreme rainfall would be in the northeast and southeast regions.
Increase of Heat Index over Bangladesh: Impact of Climate Change
Heat Index describes the combined effect of temperature and humidity on human body. This combined effect is causing a serious threat to the health of people because of the changing climate. With climate change, climate variability and thus the occurrence of heat waves is likely to increase. Evidence is emerging from the analysis of long-term climate records of an increase in the frequency and duration of extreme temperature events in all over Bangladesh particularly during summer. Summer season has prolonged while winters have become short in Bangladesh. Summers have become hotter and thus affecting the lives of the people engaged in outdoor activities during scorching sun hours. In 2003 around 62 people died due to heat wave across the country. In this paper Bangladesh is divided in four regions and heat index has been calculated from 1960 to 2010 in these regions of the country. The aim of this paper is to identify the spots most vulnerable to heat strokes and heat waves due to high heat index. The results show upward trend of heat index in almost all the regions of Bangladesh. The highest increase in heat index value has been observed in areas of South-west region and North-west Region. The highest change in average heat index has been found in Jessore by almost 5.5 0 C.
Changes in diurnal temperature range in Bangladesh during the time period 1961–2008
Atmospheric Research, 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 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.
TREND ANALYSIS OF CLIMATIC EXTREME EVENTS FOR THE HAOR AREA OF BANGLADESH USING CLIMATIC INDICES
Proceedings of the 2ndInternationalConference on Civil Engineering for Sustainable Development (ICCESD-2014), 14~16 February 2014, KUET, Khulna, Bangladesh, 2014
The main objective of this study was to obtain the extreme event analysis of trends in nine country relevant annual extreme indices for all the seven Haor districts (Sunamganj, Habiganj, Maulvibazar, Netrakona, Kishorgonj, Sylhet, Brahmanbaria) of Bangladesh. The analysis have been obtained for four BMD metrological stations (Sylhet, Srimongal, Mymensing and Comilla) with a historical time span of near about 50 years (1960 to 2008) to represent the whole Haor area. The software used to process the analysis was the RClimdex 1.0. Long term daily rainfall and temperature (maximum and minimum) data have been used to prepare the input dataset for the software and data has been quality controlled and tested for homogeneity, before they were used for calculation of indices. The analysis has identified that the temperature increased for some extreme indices (SU25) in Haor area by the last half of the century. Moreover other climatic indices showed that the rainfall intensity in Haor area was also increasing for last 50 years.