Study on the statistical characterization of cloud cover in relation to selected climatic parameters

Abstract

The rate of cloud coverage in the sky is influenced by different climatic factors. That’s why, Cloud coverage and other climatic parameters related to it such as temperature, rainfall and relative humidity of Bangladesh is the main objective of this study. Data (1953 – 2011) of thirty five meteorological stations of Bangladesh have been collected to achieve the objectives. The source of these climatic data is the Bangladesh Meteorological Department (BMD). At first the data were processed by using tools Microsoft Office Access 2003. All the climatic data of different locations are analyzed in the basis of monthly, yearly and seasonally. It is identified from analysis that in Bangladesh large amount of cloud coverage occurs from the month of June to September and in July it is maximum. In July, about seven eighth portions of the sky are covered by cloud. Small amount of cloud coverage occurs from the month of November to May and minimum in the months of December and January. In the month of January and December, only one eighth portions of the sky are covered by the cloud. Clouds begin to form from the month of February and in July the cloud formation is in large extent. Again cloud formation starts to diminish from the month of September and in December and January the formation is in little extent. In Monsoon season cloud formation is high but it is low in Dry season in most of the districts of Bangladesh. Annual variation trend at different location represents that maximum cloud coverage occurs in Sylhet and minimum in Dinajpur. In Bangladesh temperature is maximum in April or May and is minimum in January. The average monthly temperature of the country varies from 9˚c to 37˚c. Maximum average temperature occurs in monsoon seasons (June to October) and minimum average temperature occurs in dry season (November to February). The average annual humidity in Bangladesh is 79.52%. In most of the location heavy amount of humidity occurs from the month of June to October and in July it is maximum but in March it is minimum. The range of relative humidity varies from 58.56% to 89.9%. From analysis, it is found that the average annual total rainfall of the country is about 2394.28 mm. Heavy rate of rainfall occurs in the months of June, July and August at the time of full monsoon and in July the rate is maximum. Minimum rate of rainfall occurs in the months December and January. Average annual maximum rainfall occurs in Teknaf (4065.241 mm) and Sylhet (4016.286 mm) and minimum rainfall occurs in Rajshahi (1484.92 mm). The correlation coefficient (r) between cloud cover with temperature, humidity and rainfall is large and positive. It means cloud cover rate is increased with the increasing value of temperature and humidity. It also means rainfall rate increases with the increasing of cloud cover in the sky.