ANALYZING LONG-TERM TRENDS IN MONTHLY AND ANNUAL RAINFALL OVER WESTERN PART OF BANGLADESH (original) (raw)

Analysis of Rainfall Trends in the South-East Bangladesh

This paper explores annual and seasonal trends of rainfall in the South-East part of coastal Bangladesh over the period between 1980 and 2011. Non-parametric- Mann-Kendall and Sen’s test estimate is applied for detecting and estimating rainfall trends respectively. An assessment of rainfall data indicate amount of annual rainfall in South-East Bangladesh is increasing although this trend is not statistically significant. Seasonal analysis reveals least amount of rainfall occurs in winter and it is getting drier. However, trends analysis indicates the other three seasons, e.g. Pre-Monsoon, Rainy Monsoon and Post Monsoon, are becoming wetter. It is important to note that among all the seasons rainfall in Pre-Monsoon is increasing significantly (significant at p= 0.05 level) and the rate of increase is 8.5 mm/year.

Analysis of Long-term Rainfall Trends in Bangladesh

2021

The study of rainfall trends is critically important for Bangladesh whose food security and economy are dependent on the timely availability of water. Trends in monthly, seasonal, and annual rainfall on the eight divisions as well as all Bangladesh were examined in this study using a monthly data series of 40 years (1981–2020). Most of the divisions showed decreasing trend in monsoon seasonal rainfall but for only three divisions namely Dhaka, Rajshahi and Rangpur were statistically significant except in Chattogram division, whereas rainfall trend showed positive but not significant. On an annual scale, all divisions also showed a decreasing trend with insignificant exceptions in Dhaka and Rajshahi divisions, which showed a statistically significant trend. For all Bangladesh, no significant trend was detected for seasonal rainfall. Annual, pre-monsoon, monsoon and winter rainfall decreased, while post-monsoon rainfall increased at the national scale but was not significant. Only ann...

Time Series, Factors and Impacts Analysis of Rainfall in North-Eastern Part in Bangladesh

2013

The amount of rainfall received over an area is an important factor in assessing availability of water to meet various demands for agriculture, industry, irrigation, generation of hydroelectricity and other human activities. Over the study period of recent 30 years, trend values of monsoon average rainfall in Sylhet have decreased. This paper has measured the correlation coefficients between rainfall and time for Sylhet, where correlation coefficient for Sylhet is negative. In order to check the strength of linear relationship between rainfall and time, P-value has been measured. Due to various factors of Sylhet region of Bangladesh, there is a growing need to study the rainfall pattern, and also frequency of the heavy rainfall events. This study was checked annual average rainfall of 30 years for this region. It is hoped that this research may be of help to the concerned organizations and experts working on increasing rainfall problem in Chittagong.

Rainfall Variability and Linear Trend Models on North-West Part of Bangladesh for the Last 40 Years

American Journal of Applied Mathematics, 2016

Rainfall has been extensively considered as one of the initial point towards the apprehension of climate change courses. Bangladesh is recently experiencing climate change impact related to hazards like cyclone, rainfall, flood, draught etc. Climate variable like rainfall is the most important parameter which is linked with agricultural aspects too for this country. Most of the rain occurred during monsoon period in Bangladesh. This study investigates temporal variability of rainfall and liner trend models on the NorthWest part of Bangladesh over the period of 1975-2014 using data from the Bangladesh Meteorological Department. We computed and analyzed the linear trend models by using least square estimation. We estimated mean with standard deviation, cross-correlation and linear trends of annual and monsoon rainfall using MS Excel and SPSS v21. The variability of rainfall between the stations was measured by correlation test. The annual and monsoon rainfall has been found in decreasing trends in recent times. In some areas in the NorthWestern part of the country, the amount of annual and monsoon mean rainfall may be decreased abruptly comparing with average normal rainfall all over the country. The linear trend analysis of rainfall reveals a bit different trend for the last four decades. The observed data and linear trend line shows the decreasing trend of annual rainfall rate is 0.102 mm per year, whereas the decreasing trend of monsoon season rainfall rate is 0.080 mm per year. The time series statistical analysis of this study also provided the information about the correlation coefficients of rainfall among the selected five stations of the SouthWest region. The result of this study would hopefully help the planners and program managers to take necessary actions and to measure disaster management, agricultural production, drought mitigation, flood control etc.

CLIMATE CHANGE AND TREND OF RAINFALL IN THE SOUTH-EAST BANGLADESH

Rainfall has been widely considered as one of the starting point towards the apprehension of climate change courses. Various studies have indicated due to climate change rainfall pattern in Bangladesh is most likely to change which would have adverse impacts on lives and livelihoods of millions of people. This study investigates temporal variability of precipitation of the south-east coast of Bangladesh over the period of 1949- 2011. The Mann-Kendall test and the Sen’s slope estimators have been used to detect rainfall trends and to understand magnitude of changes. We find that after 1990 mean annual rainfall has increased significantly in the south east part of Bangladesh compare to the period between 1949 and 1989. The rate of increase is 10% that is 463 mm/year. However, this pattern of increase in rainfall is not evenly distributed among all the four seasons. Sixty three years (1949-2011) trend analysis shows that rainfall has increased significantly during pre-monsoon season. The rate of increase in rainfall during pre-monsoon season is 3 mm/year. Trend analysis of rainfall for the last two decades (1990-2011) reveals a bit different trend. It shows increasing trend of rainfall in monsoon season and decreasing trend of rainfall in pre monsoon and post monsoon season. Although these trends are not statistically significant. Sen’s test reveals rainfall during monsoon is increasing at the rate of 10 mm/year.

Rainfall variability and the trends of wet and dry periods in Bangladesh

International Journal of Climatology, 2010

Spatial patterns of annual and seasonal rainfall trends of Bangladesh over the time period 1958–2007 has been assessed using rainfall data recorded at 17 stations distributed over the country. Mann–Kendall trend test and the Sen's slope method are used to detect the significance and the magnitude of rainfall change, respectively. Historical dry and wet months are identified by using standardised precipitation index method and their trends are analysed to assess the possible change in wet and dry events in Bangladesh. The result shows a significant increase in the average annual and pre-monsoon rainfall of Bangladesh. The number of wet months is found to increase and the dry months to decrease in most parts of the country. Seasonal analysis of wet and dry months shows a significant decrease of dry months in monsoon and pre-monsoon. Copyright © 2009 Royal Meteorological Society

Rainfall Variation In Bangladesh: Trends, Factors And Effects

Management research and practice, 2013

Bangladesh has always been predominantly an agriculture based country. In early days, agricultural production was fully dependent on rainfall. Over the study period of recent 30 years, trend values of monsoon average rainfall in Chittagong, Dhaka and Rajshahi has risen as a consequence of the increase of the increase in rainfall. On the other hand, the trend value in Sylhet has declined with the decrease in rainfall. This paper has measured the correlation coefficients between rainfall and time for four stations: Chittagong, Dhaka, Rajshahi and Sylhet where correlation coefficient for Dhaka station and Sylhet station is maximum and negative respectively. This study indicates that climate change, global warming, destruction of hills etc. have disastrous effects on rainfall which is hampering not only the agricultural production but also the ecosystem. It is hoped that this research may be of help to the concerned organizations and experts working on this problem.

Climate Change and Trend of Rainfall in the South-East Part of Coastal Bangladesh

European Journal of Scientific Research

Rainfall has been widely considered as one of the starting point towards the apprehension of climate change courses. Various studies have indicated due to climate change rainfall pattern in Bangladesh is most likely to change which would have adverse impacts on lives and livelihoods of millions of people. This study investigates temporal variability of precipitation of the south-east coast of Bangladesh over the period of 1949-2011. The Mann-Kendall test and the Sen’s slope estimators have been used to detect rainfall trends and to understand magnitude of changes. We find that after 1990 mean annual rainfall has increased significantly in the south east part of Bangladesh compare to the period between 1949 and 1989. The rate of increase is 10% that is 463 mm/year. However, this pattern of increase in rainfall is not evenly distributed among all the four seasons. Sixty three years (1949-2011) trend analysis shows that rainfall has increased significantly during pre-monsoon season. Th...

Analysis of Rainfall Trends and Variability at Sylhet Region in Bangladesh

2016

Rainfall is the type natural process varies from place to place due to convective precipitation. In this study, rainfall data for the years 2001 to 2012 have been analyzed in terms of temporal and spatial characteristics in order to identify the change of rainfall trend and spatial distribution of annual rainfall over Sylhet region with a view to understand the pattern of rainfall trend (magnitude), by applying various numerical tools on the data obtained from 8 different climate stations. Surface Map of rainfall trends was created by applying different types of geo-statistical interpolation technique to visualize the detected tendencies. The findings revealed that a significant negative trend in rainfall was recorded in the entire Sylhet district within the period of 2001 to 2012. However, majority of the station revealed a negative trend, with Sulaghar, Lalakhal, Gobindogonj, Chattak, Sherupur, Sheola, Zakigonj, and Kanaighat stations showing significant trends of magnitude of -10...

Long-term trends in precipitation indices at eastern districts of Bangladesh

SN Applied Sciences

This study analyzed the trends of extreme daily rainfall indices over three meteorological stations located in the eastern region of Bangladesh from 1960 to 2000. The climate change-related indices included frequency-based indices: number of heavy rainfall days and consecutive dry and wet days, and intensity-based indices: annual wet-day rainfall total, daily and consecutive five-day maximum rainfall, very and extremely wet days and simple daily intensity index. The magnitude of trends in extreme rainfall indices time series was determined using the nonparametric Sen's slope estimator method, and the statistical significance of the trends was analyzed using the Mann-Kendall test. The rainfall trends exhibited regional patterns. Overall, results suggested an increase in annual rainfall over the study area; however, a tendency toward reduction of rainfall in the wet season was observed. Analysis of extreme rainfall indices demonstrated non-significant increase in frequency of heavy rainfall days, decrease in consecutive dry days and increase in consecutive wet days coupled with regional decline in daily and consecutive five-day maximum rainfall in the monsoon.