The monsoons affect nearly a half of the world’s population and a delayed summer monsoon of even a few days can have a great impact. Water availability, hydroelectric power generation and agricultural production can be greatly affected by a delayed summer monsoon. A delay between rainy seasons can lead to a risk of deadly flooding due to an increase in average rainfalls.
What are monsoons?
A look at monsoons and what causes them can give us a better idea of why there are delays at times. Monsoons are winds that, in effect, reverse their directions between winter and summer. This usually brings on a marked change in local weather. Monsoons are experienced in many parts of the world to some extent. The Asian monsoons are probably the most famous, but the southwestern United States also experience a lesser monsoon circulation. Arizona and New Mexico have summer rainy periods due to the monsoon winds blowing in from the Gulf of Cortez
The summer monsoon usually originates over the ocean and brings in both warm and humid air that is conducive to precipitation. The monsoon winds occur in response to the sun heating the atmosphere. They are caused by the difference in temperature between oceans and continents. During the early summer the land mass heats up more quickly than ocean waters.
The Jet Stream
The jet stream that flows from the tropics can slow the summer monsoon. As summer progresses the subtropical jet stream moves northward. In Asia it must rise over the Himalayas so when it does, a summer monsoon cell develops. If the jet stream is slow to move this can cause the monsoon to be delayed.
It is believed that the patterns of winds and ocean temperatures that are altered during an El Niño also change high level jet stream winds. El Niño, what the change in the flow of water currents in the Pacific Ocean near the equator are called, can affect the weather in many other parts of the world. The wind patterns associated with El Niños appear to carry moist air away that would produce monsoon rains.
Recent studies have indicated that global warming can delay the start of the summer monsoon in South Asia that will significantly reduce rainfall. This will cause an eastward shift in monsoon circulation causing rain over the ocean and less over the land area.
There are various weather phenomena that can cause the delay of the summer monsoon. The effect can be devastating to those areas of the world that depend on the rain that accompanies the monsoon winds. The only factor that may be caused by humans is global warming. It is our duty to continue to study these effects and attempt to control the warming trend. Many human lives are at stake.