Analysis of the statistical behavior of daily maximum and monthly average rainfall with rainy days variation in Sylhet (original) (raw)
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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.
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...
Multidisciplinary Science Journal
Bangladesh is one of the world's biggest deltas, making it especially susceptible to natural calamities due to its geographical location, population density, poverty, illiteracy, poorly constructed infrastructure, and so on (Biswas 2013). The average weather is commonly used to define climate. Climatic variables like temperature, rainfall, atmospheric pressure, humidity, and so on have recently received global attention (Panda and Sahu 2019). Considering the climate variables, Bangladesh can be classified as a three-season country: summer (March-May), monsoon (June-October), and winter (November-February) (Mondal and Hossain 2009). Climate change has an effect that is evident in rising temperatures as well as erratic rainfall (Asaduzzaman et al 2010; Hossain and Deb 2011). Hence, this unstable characteristic of rainfall results in water scarcity leading to a high risk of drought (Pal et al 2017). Climate change is a major threat to the world's food security and nutrition. Temperature and precipitation changes have already impacted agricultural output, and the cultivable land has shrunk considerably (Biswas 2013). Rajbhandari et al (2015) mentioned that, due to changes in the atmospheric condition, extreme temperature and rainfall changes might occur in the future. Climatic parameters like rainfall and temperature determine the conditions of the environment of a specific area which influences crop output (Modarres and da Silva 2007; Kumar and Gautam 2014). The geography of a particular area depends on climatic parameters like heavy rainfall or drought (Rajbhandari et al 2015). From 1901 to 2015, 0.78 inches of precipitation change was recorded around the world, resulting in soil erosion (Zhang et al 2010). Agriculture has suffered as a result of precipitation anomalies, particularly in developing countries. It has a significant impact on cropland areas in addition to crop yields. It is evident that during the last 20 years, farmers expanded their farmland by 9% (approximately) in order to remunerate their financial losses (Zaveri et al 2010). Agricultural production has been vastly affected by rainfall characteristics. The variability and distribution of rainfall in a region are important and useful, especially for agricultural activities. Seasonal changes in rainfall, on the other hand, are more important for floods because maximum randomness could result in a widespread flood (Yuan et al 2019). Rainfall is a major factor in flood distribution and flood risk management in various regions (Wang et al 2011). Therefore, understanding the characteristics of rainfall variability is important for the mitigation of disaster loss. The analysis Abstract Climate variability, particularly due to rainfall and temperature, has a significant impact on the country's economy and has garnered significant global attention. The magnitude of climatic factor fluctuations varies according to geographic locations. Meteorological parameter analysis is critical in countries where rainfed agriculture predominates. The current study examined the monthly variations in rainfall and temperature (maximum and minimum) over a 50-year period (1967 to 2017) in Sylhet region of Bangladesh. The non-parametric Mann Kendall test was used to detect the trend, and the Sen's slope estimation method was used to identify the trend value. A thorough analysis of the data (1967 to 2017) reveals that the monthly rainfall occurs during the monsoon season (June to September). In terms of temperature, the maximum temperature was found from June to September, indicating the monsoon season. Mann Kendall trend analysis shows that the seasonal monthly rainfall and minimum temperature trends are not statistically significant, with Sen's slope values of <0.001 and 0.034, respectively. The maximum temperature trend is significant, with a p value of 0.042. As a result, the study concludes that Sylhet's climate is changing.
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.
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 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
Spatio-Temporal Variability of Rainfall Over Bangladesh During the Time Period 1969-2003
Spatial and temporal variability of rainfall in Bangladesh has been studied in this paper from thirty-five years of rainfall data recorded at 24 rain gauges distributed over the country. Long-term annual average rainfall, coefficient of variation of annual rainfall, precipitation concentration and aridity indices at each station have been computed and then interpolated using kriging method within a geographic information system to show the temporal and spatial variability of rainfall. Mann-Kendall test has been used to analyze the trend in rainfall data in different recording stations and the Sen's slope method has been used to determine the magnitude of change. A moderate variation in inter-annual rainfall and high variation in Intra-annual rainfall in Bangladesh have been observed. Non-significant positive trend of annual, monsoon and pre-monsoon rainfall, and a negative trend in winter rainfall are found in Bangladesh. Spatial distribution of rainfall trends shows that rainfall is increasing in the coastal zone and northern Bangladesh, and decreasing in the central part of the country. A declining trend of precipitation concentration is also observed in most of the stations. These results may be a first indication of the precipitation response to global warming -a hypothesis which needs to be further investigated by means of climate model projections.
ANALYZING LONG-TERM TRENDS IN MONTHLY AND ANNUAL RAINFALL OVER WESTERN PART OF BANGLADESH
ICCESD 2020 Conference , 2020
Rainfall is the key climatic variable that governs the regional hydrologic cycle and availability of water resources. The climatic variability is referred to the long-term changes in rainfall, temperature, humidity, evaporation, wind speed and other meteorological parameters. In order to identify the change, quantification of environmental change is necessary that will be supportive to make forecast for future. This will result into a better planning and awareness for natural disasters. The objective of the study is to examine the rainfall variability over the western part of Bangladesh. This will give an understanding about trends or changes in rainfall over the studied region. In the current study, trend analysis has been carried out on monthly and annual rainfalls for the selected eleven rainfall stations located within the western part of Bangladesh. The well-known statistical trend analysis techniques including Mann-Kendall test and Sen's slope estimator are used to detect trends at the 5% significance level on time series data of the study area for the time period from 1948 to 2014. These tests are adopted to identify the change in magnitude and direction of existing trend over time. The analysis for trend detection using the Mann-Kendall test and Sen's slope estimator is undertaken in the XLSTAT 2016 platform. Trend detection of rainfall using the adopted techniques over 65 years shows increasing trend in monthly rainfall for four rainfall stations, namely Satkhira, Khulna, Jessore and Ishurdi stations. Three of them are located in the southwest coastal part of the study area. Furthermore, the analysis indicates similar trend in annual rainfall and the increasing trend is evidenced for three rainfall stations, namely Satkhira, Khulna and Ishurdi stations in which two are located in the coastal part. The findings of this analysis would be of interest to water resources managers and policy makers for the effective planning and management of water resources in Bangladesh.
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Variability and Trends of Summer Monsoon Rainfall over Bangladesh
Journal of Hydrology and Meteorology, 1970
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