Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Patterns of Climate Change and Its Impacts in Northwestern Bangladesh

Samarendra Karmakar
Bangladesh Centre for Advanced Studies (BCAS), Dhaka, Bangladesh

Abstract/ Executive Summary:

Climatological data on different parameters like daily temperature, rainfall, maximum and minimum temperatures, relative humidity and pre-monsoon daily thunderstorm frequency over Rajshahi, Rangpur and Dinajpur for the period 1981-2016 have been used to study their temporal variations on a monthly, seasonal and annual basis. Rainfall data is also used to compute the non-rainy days (dry days), and the relative humidity is used to compute heat stress over the places under study. The trends of dry days and heat stress are studied. Daily maximum and minimum temperatures are used to find out the frequencies of temperature >36⁰C and temperature <10⁰C for studying trends of heatwaves and cold waves over the region. The temporal variations of all the parameters have increasing trends except for some parameters which have increasing trends from 2000. The study has revealed that the annual mean temperature has increasing trends in Rajshahi and Rangpur with increasing rates of +0.012 and +0.017⁰C/year respectively during 1981-2016. It has a decreasing trend in Dinajpur at -0.017⁰C/ year during 1981-2016. But the annual mean temperature at Dinajpur has increased trend at a rate of +0.014⁰C/year from 1990. Annual rainfall has decreasing trends at all stations under study. The rates of decreasing of annual rainfall are -8.946, -14.170 and -11.030 mm/year in Rajshahi, Rangpur and Dinajpur respectively. The study also reveals that the annual frequency of dry days has sharp increasing trends at the rates of +0.370, +0.096 and +0.205 day/year at Rajshahi, Rangpur and Dinajpur and the maximum increasing trend of annual dry days is at Rajshahi. The seasonal dry days have increasing trends from 2000 at all the places with much higher rates of increase. This will enhance the drought conditions in northwest Bangladesh. The annual mean heat stress over northwest Bangladesh indicates significant increasing trends at Rajshahi and Rangpur and decreasing trend at Dinajpur during the period 1981-2016; whereas the annual heat stress at Dinajpur has increased trends at +0.022/year since 1989. Rajshahi has the highest mean frequency of maximum temperature >36⁰C in the month of May whereas Dinajpur and Rangpur have the maximum mean frequency of maximum temperature >36⁰C in the month of April. Heat waves will be more long-lasting in Rajshahi during April-July.

Keywords: Climate change; Heat waves; Cold wave; Heat stress; Drought, Flood

Location: 1981-2016 at Rajshahi, Rangpur, Dinajpur, Ishurdi, Bogra, Mymensingh, Dhaka and Faridpur

Start Date: 00-00-1981

End Date: 00-00-2016

Program Area: Risk Management in Agriculture

Commodity: Climate change

Objectives:

The main objective of the present study is to investigate the trends of heat waves, cold waves, non-rainy days, humidity, thermal heat stress, thunderstorm frequency, some extreme events, and their impacts in northwestern Bangladesh.

Methodology:

Daily data on dry-bulb temperature, rainfall, humidity, minimum temperature and maximum temperature along with the frequency of thunderstorms at Rajshahi, Rangpur and Dinajpur for the period 1981-2016 are collected from Bangladesh Meteorological Department (BMD) and used in the study. From the daily data, monthly, seasonal and annual mean temperatures, humidity, frequency of non-rainy days, and total rainfall are computed. The daily highest values of maximum temperature and humidity in each month are computed for the period under study to find out the extreme cases of heat stress.

For spatial distributions of rainfall and temperature over northwest Bangladesh, the data of BMD for the period 1981-2016 at Rajshahi, Rangpur, Dinajpur, Ishurdi, Bogra, Mymensingh, Dhaka and Faridpur are used. The temporal variations of seasonal and annual temperatures, rainfall, non-rainy days and humidity are graphically prepared and the trends are computed. The annual mean temperature and rainfall are spatially distributed over northwest Bangladesh, and the spatial distributions of maximum and minimum temperatures during cold and heat waves are made. The monthly mean temperature and humidity along with the highest values of maximum temperature and humidity are used to compute Thom’s Temperature and Humidity Index (THI) for Rajshahi, Rangpur and Dinajpur stations according to the following the same formula (Thom, 1959):

THI=0.8 x T +RH / 100 x (T- 14.4) + 46.4

Where T is the dry-bulb or ambient temperature in ⁰C and RH is the humidity (%).

Source of Information: Journal of Engineering Science 10(2), 2019, 33-48

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

On the basis of the present study, the following conclusions can be drawn: i. The annual mean temperature ranges from about 24.4⁰C in the north and 25.2⁰C in the south over northwest Bangladesh. From the spatial distribution of seasonal mean temperature, it has been found that the seasonal mean temperature ranges are 18.0-18.2⁰ 25.6-27.8 28.2-28.8 and 24.2-24.6⁰C in winter, pre-monsoon, monsoon and post-monsoon seasons respectively. The monsoon means the temperature is higher than that of the pre-monsoon temperature. ii. Annual mean temperature has increasing trends in Rajshahi and Rangpur with increasing rates of +0.012 and +0.017⁰C/ year respectively. It has a decreasing trend in Dinajpur at -0.017⁰C/ year. The seasonal mean temperature at Rajshahi and Rangpur has increasing trends in all the seasons, except the winter season when the temperature has decreasing trend at Rajshahi. The maximum rate of increase in monsoon mean temperature is +0.024⁰C/year in Rajshahi. The seasonal mean temperature in Dinajpur has decreasing trends except for the monsoon season when it has an increasing trends. The maximum decreasing trend in mean temperature is -0.052⁰C/ year during winter season in Dinajpur. iii. Annual rainfall has decreasing trends at Rajshahi, Rangpur and Dinajpur. The rates of decreasing of annual rainfall are -8.946, -14.170 and -11.030 mm/year in Rajshahi, Rangpur and Dinajpur respectively. The seasonal rainfall has also decreasing trends in northwest Bangladesh except the premonsoon season when it has increasing trend in Rajshahi and the post-monsoon season when there is increasing trends in Rangpur and Dinajpur. The decreasing trends in monsoon season are very high and significant with rates of decrease of -6.788, -13.800 and -9.870 mm/year in Rajshahi, Rangpur and Dinajpur respectively. iv. Annual frequency of days with minimum temperature <10⁰C has increasing trend (+0.035 days/year) at Rajshahi and decreasing trends at Rangpur (-0.123 days/year) and Dinajpur (-0.119 days/year). The duration of cold waves may increase in future at Rajshahi and decrease at Rangpur and Dinajpur. v. Rajshahi has the highest mean frequency of maximum temperature >36⁰C in the month of May whereas Dinajpur and Rangpur have the maximum mean frequency of maximum temperature >36⁰C in the month of April. Heat waves will be more long lasting in Rajshahi during April-July. The annual frequency of heatwave days with Tmax >36⁰C has an increasing tendency in northwest Bangladesh. vi. Non-rainy days (dry days) are maximum in January and December with the frequency of 30 days. It is minimum during the monsoon months with the lowest minimum frequency of 10-11 days in July and then it increases slowly up to December. The annual frequency of dry days has sharp increasing trends at the rates of +0.037, +0.096 and +0.205 days/year at Rajshahi, Rangpur and Dinajpur and the maximum increasing trend of annual dry days is at Rajshahi. The seasonal dry days have increasing trends from the year 2000 at all the places with much higher rates of increase. vii. During the period 1981-2016, the annual mean RH has increasing trends at Rajshahi and Dinajpur at the rates of +0.99% and +0.253% whereas the decreasing trend of -0.096% per year at Rangpur. The annual and seasonal mean relative humidity have definite decreasing trends since 1998 in the northwestern part of the country. viii. The annual mean heat stress over northwest Bangladesh indicates significant increasing trends at Rajshahi and Rangpur and decreasing trend at Dinajpur during the period 1981-2016. But the annual heat stress at Dinajpur has increased trends at +0.022/year since 1989. ix. The monthly and seasonal frequencies of thunderstorms during the pre-monsoon season have increasing trends over northwest Bangladesh.

Knowledge Management: Journal