The Indian Monsoon - Introduction

Residents of Mumbia, India wade through the streets in late July 2005 -

When a monsoon is mentioned, people conjure up images of torrential rain, massive flooding (such as the picture to the left) and mudslides. Those who respond in this manner would probably be surprised to learn that monsoons actually come in two varieties--a version typified by rainy conditions and another characterized by a general lack of precipitation. In India, for example, the summer monsoon is generally rainy while the winter monsoon is predominantly dry. This is not to suggest that it rains endlessly during India's summer monsoon and not at all during the duration of the winter monsoon.

Monsoon, derived from the Arabic term for season, refers to the dramatic seasonal shifts in prevailing wind direction and the resulting weather conditions that occur in many parts of the world. It is the combination of the shift in wind direction and the increase or decrease in precipitation that delineates the transition from one monsoon period to another.

Although differences exist in the criteria used for determining whether or not a region is monsoonal, meteorologists agree that most of the notable monsoon areas are located within that part of the Eastern Hemisphere that includes southeast Asia, Indonesia, northern Australia and India. The pages that follow will explain the meteorological features that promote the development of the monsoons so famous in this region. 

Undoubtedly, the summer monsoon and its associated precipitation is capable of causing considerable human suffering. Each year, thousands are forced to flee their homes to escape ravaging floods. Occasionally, entire villages are swept away in a torrent soup of mud and water. In many instances the victims are never found. In July of 2005, flooding near Mumbai (formerly known as Bombay) on India's west coast claimed the lives of nearly 1,000 people in a matter of just a few days.

Although the the summer monsoon has a destructive side, the precipitation received during its prominence is vital to the sustenance of millions of people. Farmers depend upon the rain to nourish their crops and a delay in the onset of the summer monsoon can lead to widespread starvation resulting from agricultural failure. Rice, the region's primary food source, is particularly dependent upon the timely arrival of copious amounts of rain. Even the deadly flooding delivers benefits, as overflowing rivers deposit much needed nutrients on adjoining farmland. The monsoon cycle is a necessary part of the life cycle in this region.

My examination of the southwest monsoon will concentrate on India, the Bay of Bengal, the Arabian Sea and that portion of the Indian Ocean immediately south of these areas. The next page provides a brief geographical overview.