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Variability of Relatlve Humidity in Bangladesh

C. MOUMITA
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

M. T. ISLAM
Graduate Training Institute, Bangladesh Agricultural University, Mymensingh. Bangladesh.

Abstract/ Executive Summary:

Mean relative humidity is analyzed over Bangladesh using 30 years climatic data from 1972 - 2001 at six stations. The study includes annual trends, five-years moving average, regional average and anomalies of relative humidity of different stations. It reveals that increasing trends of annual average relative humidity were recorded in Rajshahi, Sylhet, Barisal, Khulna and Chittagong stations by 0.259, 0.061, 0.104, 0.08 and 0.021%/year, respectively. Only decreasing trend was observed in Dhaka region. During the study period annual average relative humidity was statistically significant at 1 % level for Rajshahi and Barisal stations. It has an increasing trend over the country and increased at a rate of 0.078%/year during the studied period. The highest regional average of relative humidity was recorded over Barisal station while lowest value over Dhaka station during 1972 - 2001.

Keywords: Variability, Relative humidity, Meteorology

Location: Bangladesh Agricultural University, Mymensingh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Non-commodity: Analysis and interpretations

Objectives:

To study the nature of trends of relative humidity and its anomalies for the last 30 years during 1972 - 2001.

Methodology:

Relative humidity data were collected from Bangladesh Meteorological Department (BMD) and Bangladesh Agricultural Research Council (BARC), Dhaka. There were some missing data in some months at some stations. Data were considered to be missing when the records of data were not available. To maintain the continuity, the gaps were filled up by the time mean values of the existing years. Monthly mean data of relative humidity (%) at six stations i.e. Rajshahi (24⁰37^// N, 88⁰70^// E), Sylhet (24⁰90^// N, 91⁰88^// E), Barisal (22⁰75^// N, 90⁰ 37^// E), Khulna (22⁰78^// N, 89⁰ 53^// E), Dhaka (23⁰77^// N, 90⁰38^// E) and Chittagong (22⁰ 27^//N, 91⁰88^//E) from January, 1972 to December, 2001 were computed. Data were put in MS Excel and MSTATC for statistical analysis. Annual average and five years' moving average of relative humidity of different stations of Bangladesh were calculated to analyse the variation and trend line of relative humidity during 1972 - 2001. Regional averages of 30 years climatic data were calculated to find out the distribution of relative humidity. The regression equations and the coefficient of determination (R²) have been obtained through scatter diagrams by taking two indices at a time. The significance test of the coefficient of determination (R²) has been carried out by using t-test.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 31, No.2, 173-180,2007

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Increasing trends of annual average relative humidity were recorded in Rajshahi, Sylhet, Barisal, Khulna and Chittagong stations by 0.259, 0.061, 0.104 in 0.08 and 0.021 %/year, respectively. Only decreasing trend was observed in Dhaka. During the study period annual average relative humidity was statistically significant at 1 % level for Rajshahi and Barisal and it has an increasing trend over the country. The highest regional average of relative humidity was recorded over Barisal while lowest value was recorded over Dhaka in Bangladesh during 1972 - 2001.

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