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Variability and Trends of Summer Monsoon Rainfall over Bangladesh  [PDF]
MN Ahasan,Md AM Chowdhary,DA Quadir
Journal of Hydrology and Meteorology , 2010, DOI: 10.3126/jhm.v7i1.5612
Abstract: In this paper, the updated rainfall data of 50 years (1961-2010) for 30 selected rain gauge stations of Bangladesh have been used. The data were analyzed to investigate the variability and trends of summer monsoon (June- September) rainfall over Bangladesh. The possible teleconnection of monsoon rainfall variability with ENSO has also been investigated. Annual profile of the station mean monthly rainfall of Bangladesh shows a unimodal pattern with high rainfall between June-September (monsoon season) with highest in July and low rainfall between December – February with lowest in January. All Bangladesh mean summer monsoon rainfall is 1769.14 mm, standard deviation 209.16 mm (coefficient of variance 11.82 %) and annual country average rainfall is 2456.38 mm. Summer monsoon rainfall widely varies over the geographical areas with lowest in central-western part and highest in southeastern part with next highest in northeastern part of the country. The trend analysis shows that the trend of the country average monsoon rainfall is decreasing (-0.53 mm/year). The spatial distribution of the trend values indicates that the summer monsoon rainfall exhibits increasing trends at the rate of 5-6 mm/year in the NW region and 3-4 mm/ year in the south-central and extreme SE region. The eastern region exhibits decreasing trends of about -2 to -7 mm/year with highest (-6 to -7 mm/year) in the east-central part. The time series plot of country average summer monsoon rainfall shows the inter-annual variability in the timescales of 2-3 years and 4-6 years. The time series of 5 year moving average reveals existence of low frequency variability of timescales of 9-14 years. The time series of Bangladesh monsoon rainfall shows that there were 11 strong monsoon years and 8 weak monsoon years within the periods of 1961-2010 (50 years). The analysis of the decadal mean rainfall shows that the decades 1961-1970 and 1981-1990 were wet and the decades 1971-1980, 1991-2000 and 2001-2010 were dry. Floods in Bangladesh result from the excess rainfall occurring both inside and outside the country. Summer monsoon rainfall is characterized by active and weak (break) spells, which are associated with the fluctuation of monsoon rainfall in the time scales of 20-25 and 40-50 days. Such fluctuations are caused due to north-south movement of the monsoon trough. The fluctuations in the time scales of 4-7 and 10-14 days are associated with the formation of low pressure systems over the head Bay. The possible atmospheric teleconnections of summer monsoon rainfall with ENSO have also been
Rainfall Erosivity in Southeastern Nigeria
MN Ezemonye, CN Emeribe
Ethiopian Journal of Environmental Studies and Management , 2012,
Abstract: In developing land management plans to minimize erosion problem, it is imperative to provide quantitative information on aggressiveness of storms for identifying areas in the landscape which are sensitive to disturbances. The study established that rainfall erosivity (R) indices over Southeastern Nigeria range from very low to very high erosivity. Periods of very low erosivity coincided with the dry season months in the region while the very high R coincided with the rainy season peak periods (June-September). Calabar Owerri and Port-Harcourt recorded the highest erosive storms/ more months of very high erosivity index. The deterministic relationship between kinetic energy of rains and erosivity pattern observed for the different stations showed that erosive rains contribute significantly to detachment of soil materials in the study area. The need for proper land use management and maintenance of surface vegetal covers cannot be overemphasized with increased weather variability. Monitoring of hydrologic regime and climate –related factors in the region as well as defining areas most vulnerable to erosion would help in erosion disaster management.
A rainfall simulation model for agricultural development in Bangladesh  [PDF]
M. Sayedur Rahman
Discrete Dynamics in Nature and Society , 2000, DOI: 10.1155/s1026022600000339
Abstract: A rainfall simulation model based on a first-order Markov chain has been developed to simulate the annual variation in rainfall amount that is observed in Bangladesh. The model has been tested in the Barind Tract of Bangladesh. Few significant differences were found between the actual and simulated seasonal, annual and average monthly. The distribution of number of success is asymptotic normal distribution. When actual and simulated daily rainfall data were used to drive a crop simulation model, there was no significant difference of rice yield response. The results suggest that the rainfall simulation model perform adequately for many applications.
Pattern Recognition of Rainfall Using Wavelet Transform in Bangladesh  [PDF]
Abdur Rahman, Ataul M. Anik, Zaki Farhana, Sujit Devnath, Zobaer Ahmed
Open Journal of Statistics (OJS) , 2018, DOI: 10.4236/ojs.2018.81009
Abstract: The aim of the study is to explore the regional variation of changing patterns of rainfall in Bangladesh using wavelet transform. The study is completed using rainfall variation of the five regions of Bangladesh as Dhaka, Cox’s Bazar, Rajshahi, Bogra and Sylhet. The duration of the study period was 69 years for Dhaka, 64 years for Cox’s Bazar, 40 years for Rajshahi, 54 years for Bogra and 55 years for Sylhet. The results of the wavelet analysis reveals that, in Rajshahi the amount of rainfall are decreasing in a significant rate among the other study regions. It also explores the annual periodicity of rainfall for all the study regions along with a special 6-month periodicity in the Cox’s Bazar. In addition, this analysis also explores a dominating 3 - 4 year cycle of rainfall in all the study regions. Besides the climate change in Cox’s Bazar and Sylhet are pretty much alarming.
Response of Turmeric to Planting Material and Mulching in the Hilly Region of Bangladesh
M.K. Alam,Z. Islam,M.A.Rouf,M.S. Alam
Pakistan Journal of Biological Sciences , 2003,
Abstract: A field experiment was conducted at the Hill Agricultural Research Station, Khagrachari to find out a suitable planting material and mulch material for turmeric production in the hill slope of Chittagong Hill Tracts. Nine treatment combinations comprising 3 levels of planting material (mother rhizome, primary finger and secondary finger) and 3 levels of mulching (rice straw, sungrass and non-mulched) were compared. Mother rhizome showed better yield performance. Sungrass appeared the best mulching material for producing higher turmeric yield. Mother rhizome coupled with sungrass mulching gave significantly higher yields (387.6 g clump-1 and 29.4 t ha-1) of turmeric in hilly region of Bangladesh.
Regional Variation of Temperature and Rainfall in Bangladesh: Estimation of Trend  [PDF]
Abdur Rahman, Md. Jibanul Haque Jiban, Sohul Ahmed Munna
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.57066
Abstract:

This study mainly focuses on exploring the regional variation of the changing patterns of temperature and rainfall in Bangladesh. The analysis is based on the temperature and rainfall variation in Bangladesh over five regions as Dhaka, Cox’s Bazar, Rajshahi, Bogra and Sylhet. The duration of the study period was chosen as 1953-2012 for Dhaka, 1948-2012 for Cox’s Bazar, 1972-2012 for Rajshahi, 1958-2012 for Bogra and 1957-2012 for Sylhet. The findings of the non-parametric Mann-Kendal test reveals that significant increase of maximum temperature has been found in Cox’s Bazar and Sylhet. Significant decrease of maximum temperature has been found in Dhaka and Bogra. Significant increase of minimum temperature has been found in Dhaka and Cox’s Bazar whereas significant decrease has been found in Rajshahi. Significant decrease of rainfall has been found in Rajshahi among the study region. The maximum temperature increases significantly by 0.021 degree Celsius per year in Cox’s Bazar and Sylhet. In case of minimum temperature highest increase is found in Dhaka by 0.049 degree Celsius followed by Cox’s Bazar (0.038 degree Celsius per year) whereas significant decrease has been found in Rajshahi by 0.047 degree Celsius per year.

Tick and tick borne protozoan diseases of livestock in the selected hilly areas of Bangladesh  [cached]
U.K. Mohanta
International Journal of Agricultural Research, Innovation and Technology : IJARIT , 2011,
Abstract: To study the tick and tick borne protozoan diseases of livestock in the hilly areas of Bangladesh, an attempt was made to collect tick and blood samples from cattle, goat and gayal (Bos frontalis) from different areas of the three hill districts. In this study, two species of ticks namely, Boophilus microplus (92%) and Amblyomma testudinarium (21.6%) and two species of blood protozoa like Babesia bigemina (16.63%) and Anaplasma marginale (14.94%) were recorded. Seasonal prevalence of ticks was highest in summer (97%) in comparison to rainy (95%) and winter (86%) season. On the other hand, the seasonal prevalence of blood protozoa was highest in rainy season (45.45%) in comparison to summer (27.87%) and winter (16.55%). Again, animals aged more than 2 (two) years of age (52%) found to be more susceptible to blood protozoan diseases than animals aged between 1-2 years of age (33.97%). But none of the animals under one year of age were found to be infected with blood protozoan diseases.
FREQUENCY STRUCTURE OF MAJOR RAINFALL EVENTS IN THE NORTH-EASTERN PART OF BANGLADESH
G. M. JAHID HASAN,RAQUIBUL ALAM,QUAZI NIRZZHORUL ISLAM,MD. SAKHAWAT HOSSAIN
Journal of Engineering Science and Technology , 2012,
Abstract: 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. The distribution of rainfall in time and space is, therefore, an important factor for the economic development of a country. Due to rapid urbanization in various parts of the north-eastern 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 monthly average rainfall from daily records of last 50 years for this region. In order to check the major events, time history of monthly rainfall data were transformed into frequency domain using the Fast Fourier Transform (FFT). Estimated peak frequency (11.98 month) depicts that major rainfall events of a year are occurring earlier than the previous year. The variability of rainfall in time scale was also checked from filtered signals, which is very useful for long-term water resources planning, agricultural development and disaster management for Bangladesh.
Correlogram Analysis of Trends and Cycles in Rainfall Over Southeastern Nigeria
M.N. Ezemonye,C.N. Emeribe
Pakistan Journal of Social Sciences , 2012, DOI: 10.3923/pjssci.2011.325.333
Abstract: Water resources in Southeastern Nigeria mainly depend on rainfall which is subject to great variability. Since, the wake of urbanization water use in the region has increase resulting in change in hydrological cycle. This study investigated the characteristics of oscillations that appear in the time series of annual rainfall amounts in Southeastern Nigeria with a view to predicting rainfall extremes. The analysis was carried out using the Autocorrelation Function Method. It was found that no significant trend was observed in all the climatic stations expect for Uyo within the periods of study (1982-2005). A general increase in annual rainfall amount was identified in almost all the stations from 1980 up to the end of the 20th century followed by a gradual decline or steady slope in the trend line of rainfall amounts. The study showed that highest rainfall amounts were mostly recorded between 1995 and 1997. From the correlogram analysis, a sequence of 4 years (Onitsha), 4, 6 and 15 years (Owerri), 5 years (Enugu), 3 years (Port-Harcourt), 1 year (Uyo), 10 years (Calabar), 1 year (Ikom) and 8 years (Ogoja) periodicities in cycles of high rainfall were determined in the study area. Cycles in rainfall deficiencies on the other hand yielded periodicities sequence of 10 and 11 years (Onitsha), 8 and 14 years (Owerri), 14 years (Enugu), 4, 7 and 10 years (Port-Harcourt), 12 years (Uyo), 12 years (Calabar), 3 years (Ikom) and 3 years (Ogoja). From the sequence of periodicities of cycles for rainfall deficiencies over Southeastern Nigerian similarities was observed between Uyo and Calabar and between Ikom and Ogoja pointing to the unique physical factors controlling the rainfall of these areas. Finally, results of the analysis are expected to provide information that would be helpful in formulating policies for mitigating flooding and drought in the region.
Identifying the dependency pattern of daily rainfall of Dhaka station in Bangladesh using Markov chain and logistic regression model  [PDF]
Mina Mahbub Hossain, Sayedul Anam
Agricultural Sciences (AS) , 2012, DOI: 10.4236/as.2012.33045
Abstract: Bangladesh is a subtropical monsoon climate characterized by wide seasonal variations in rainfall, moderately warm temperatures, and high humidity. Rainfall is the main source of irrigation water everywhere in the Bangladesh where the inhabitants derive their income primarily from farming. Stochastic rainfall models were concerned with the occurrence of wet day and depth of rainfall for different regions to model the daily occurrence of rainfall and achieved satisfactory results around the world. In connection to the Markov chain of different order, logistic regression is conducted to visualize the dependence of current rainfall upon the rainfall of previous two-time period. It had been shown that wet day of the previous two time period compared to the dry day of previous two time period influences positively the wet day of current time period, that is the dependency of dry-wet spell for the occurrence of rain in the rainy season from April to September in the study area. Daily data are collected from meteorological department of about 26 years on rainfall of Dhaka station during the period January 1985-August 2011 to conduct the study. The test result shows that the occurrence of rainfall follows a second order Markov chain and logistic regression also tells that dry followed by dry and wet followed by wet is more likely for the rainfall of Dhaka station and also the model could perform adequately for many applications of rainfall data satisfactorily.
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