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Probability Distribution of Relative Humidity and Surface of Nearly Assured Relative Humidity in Bangladesh

Manotosh Hawladar
PSO
Agricultural Statistics Division, BRRI, Gazipur

Md. Shahjahan Kabir
SSO
Agricultural Statistics Division, BRRI, Gazipur

Abstract/ Executive Summary:

Long-term relative humidity data of Bangladesh Meteorological Department (BMD) was analyzed (i) to select suitable probability distribution of monthly relative humidity for the months of May-October during which most of the annual rainfall concentrates in Bangladesh and (ii) to generate surface of nearly assured monthly relative humidity (i.e., minimum monthly relative humidity at 90% probability level) based on the selected probability distribution. Results revealed that Beta distribution may fairly be used to graduate probability distribution of monthly relative humidity for the selected months in Bangladesh. Surface maps were then constructed for nearly assured monthly relative humidity to generate information regarding monthly relative humidity across the country based on Beta probability distribution.

Keywords: Humidity, Probability distribution, Surface & assured monthly relative humidity

Location: Agricultural Statistics Division, BRRI, Gazipur

Start Date:

End Date:

Program Area: Socio-economic and Policy

Non-commodity: Weather/Climate

Objectives:

To determine probability distribution of monthly relative humidity .
To construct surface of nearly assured monthly relative humidity in Bangladesh.

Methodology:

The long-term daily relative humidity data for the period 1948-1999 collected by the Bangladesh Meteorological Department (BMD) for 30 weather stations have been utilized in this study. Normal distribution and Beta distribution were compared as the probable candidates to identify the best fitted model for graduating the probability distribution of monthly average relative humidity (%) for the months from May to October during which most of the rainfall occurs in Bangladesh. These distributions were checked for 18 weather stations of Bangladesh Meteorological Department (BMD) for which minimum 30 years’ daily relative humidity (%) data were available. Goodness of fit was judged by c² test. Selecting the appropriate distribution, monthly average relative humidity with 90% probability level were computed by solving the equation F(x,=0.90 ,where are the estimates of parameters of the selected distribution. These estimates of relative humidity thus obtained were treated as nearly assured relative humidity. These estimates at 30 weather stations of BMD were then used to construct surface of nearly assured monthly relative humidity across the whole country for each of the months from May to October. ARC View 2.1 spatial analyst was used to create the surface following Kriging interpolation module.

Source of Information: BRRI Annual Report 2005-06, 236-238, BRRI, Gazipur.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Probability distribution of monthly relative humidity can fairly be graduated by Beta distribution in Bangladesh.
Surface maps for the nearly assured monthly relative humidity (i.e., minimum monthly relative humidity at 90% probability level) constructed for each of the months from May to October can suitably be used to predict the nearly assured monthly relative humidity at any location of Bangladesh.

Knowledge Management: Report/Proceedings