The role of orography on wind and rainfall distribution in and around a mountain gap: Observational study

Abstract

A study of rainfall distribution along the 30 km wide Palghat Gap (Lat. 10⁰46’) at about 97 m above mean sea level between Nilgiris (1 to 1.5km) shows the rainfall decrease gradually and continuously from the coast against the gap cross section. Along the sections north and south f the gap, the rainfall increases upto a certain height from the coast in the windward side and decreases gradually in the lee-side. It is seen that the percentage increase of rainfall at the mountain section with reference to the gap is about 100 per cent at a distance of 60 km from the coast and at a height of about 750 m and decreases thereafter before the peak of the barrier is reached. It is found also that the monsoon winds at the exit of the gap are twice or thrice of the wind speed at the gap.