Monsoon Winds

Introduction

Northern hemisphere and Southern hemisphere experiences winter and summer at different times of the year. This difference in temperature causes pressure difference between the hemisphere, causing winds to occur on a large scale.

These winds are deflected as they move across the earth, changing its direction. This is caused by Coriolis Effect due to the Earth’s rotation

Southwest Monsoon

Northern hemisphere experiences summer
Southern hemisphere experiences winter

Low Pressure develops over northern hemisphere
High Pressure develops over southern hemisphere

Winds move from south to the north
- Winds move from high pressure to low pressure

Winds are then deflected to the right at the equator

Lasts from June to September – hot and wet weather experienced over India and Bangladesh

Northeast Monsoon

Northern hemisphere experiences winter
Southern hemisphere experiences summer

High pressure develops over northern hemisphere
Low pressure develops over southern hemisphere

Winds blow from the north to south
- Winds move from high pressure to low pressure
- Winds deflected to the left at the equator

Winds blow across Asian Continent
- Does not blow across ocean/water body – wind is cold and dry
- India and Bangladesh experiences cold and dry weather
- Not much rain is experienced

Lasts from October to January

Tropical Monsoon Climate

High temperatures throughout the year
Annual temperature range (6degC) is higher than tropical equatorial climate
Distinct Wet and Dry seasons




India
- Wet rainy season (June – September)
o Onshore southwest monsoon
o 95% of rainfall during this period
o Monsoon crosses Indian Ocean to west coast of India
- Cool dry season (October to February)
o Lower temperatures
o Offshore northeast monsoon brings dry winds with no rain
o Possible rain
§ If monsoon blows over bay of Bengal
- Hot dry season (March – June)
o Sun is overhead at Tropic of Cancer
o Cloudless sky, low humidity
o No rain

Malaysia

- Temperature
o High throughout the year
o Regional variations in temperature – Relief factor
§ Central range of mountains
§ Influence of altitude on central range
§ High mountainsΰ low temperature

- Precipitation
o High annual rainfall
o Regional variations in rainfall – Relief factor
§ Central range on Peninsula
§ Mountains in Sumatra
§ Difference between leeward and windward slopes
· Windward – High rainfall
· Leeward – Low rainfall
o High rainfall at Northeast of peninsula
§ Windward slope of central range
§ Relief rain
§ Rain-bearing northeast monsoon winds (Nov-Jan)
o Reduced rainfall at West of peninsula
§ Onshore effect of SE monsoon is reduced by mountain presence in Sumatra
o Moderate rainfall at central highlands and southern areas
§ Relief rain
§ NE and SW monsoons
§ Convectional rain in the South
o Least rainfall – South Central and parts of West
§ Rain shadow location – only dry wind
§ Mountains in Sumatra also block most of the rain