Rainfall and Temperature Analysis of Sonitpur 1901-2013
The State of Assam is one among eight states in the North Eastern Region of India (NER). It is also part of the Eastern Himalayan Bio-diversity Hotspot. Spread across 78438 sq km, Assam occupies 2.39% of India's Geographical Area.
With a 'Tropical Monsoon Rainforest Climate', Assam is a temperate region with average mean temperatures of 25ºC Celsius. Summers are the dominant season, starting late- April and lasting up to mid-October. Temperatures could soar to 38ºC Celsius accompanied by 90% humidity. Heavy rainfall and frequent thunderstorms provide much needed relief.
The winter months are very pleasant, starting late-October up to late-February. On cold days temperatures drop to as low as 8ºC Celsius. Average Mean emperatures during these months are at a very comfortable 20ºC Celsius. Spring (March and April) and autumn (September and October) with moderate temperatures and modest rainfall are the most comfortable seasons.
The topographical terms Assam lies between Tropical and Extra-tropical region. Geographically, it is located in the SE sector of the Tibetan Plateau with Brahmaputra and Barak valley. More than 100 tributaries carry the rain water from adjoining hilly areas including snowmelt water from the High hills of the Himalayan range. In meteorological terms, the seasons are Winter (January & February), Pre-Monsoon (March to May), SW-Monsoon (June to September) and post monsoon (Oct to Dec).
During SW-monsoon period wide spread rainfalls occur over entire NE Region due to the effect of Monsoon-lows, cyclonic circulation/Monsoon trough in lower level of atmosphere. Rainfall distribution of Assam/NE Region (Annual/ monsoon seasonal) shows a few heavy rainfall zones:
- Western Zone: Goalpara, Dhubri, Bogaigoan, Kokrahjarh, Chirrang etc.
- Eastern Zone: Lakhimpur, Digrugarh, Jorhat etc.
- Southern Zone : Karbianglong, Cachar, North Cachar Hill ( Barak Valley)
The central zone comprises of Nowgoan and southern part of Sonitpur and Darrang districts with occurrence of comparatively low rainfall with reference to the area around it.
The post monsoon season is the transient period between Monsoon and winter season. Scanty rainfall are seen during this period occasionally due to the western disturbance and remnant parts of Tropical Cyclonic storm which are formed over Bay of Bengal and moved across Bangladesh.