The major controlling factor over the monsoon climate is its relationship to the monsoon circulation.The Monsoon is a seasonal change in wind direction.
The “classic” monsoon circulation of Asia exhibits an onshore flow of air (air moving from ocean towards land) during the summer or high-sun season, and offshore air flow (air moving from land toward water) during the winter or low-sun season. The change in direction is due to the difference in the way water and land heat.
The monsoon climate has a high mean annual temperature and a small annual temperature range like equatorial climate.
As shown in the climograph for Mangalore, India the average annual temperature is 27.05 oC (80.7oF) but only has an annual temperature range of 3.6 oC (2oF).
A greater variation in the mean monthly temperatures .
In northern hemisphere, autumn and winter are experienced between october and february. Monsoon countries in the north experience lower temperature during these month.
Between March and September, it is spring and summer in the northern hemisphere. Temperatures increase and monsoon countries experience warmer weather during this period.
The diurnal temperature range varies with the wet and dry seasons.
The Wet season, extensive cloud cover and most of incoming solar radiation during the day and traps the outgoing solar radiation during the day and traps the outgoing radiation at night.
The diurnal temperature is small.
Seasonality of its precipitation is the hallmark and most well-known characteristic of the monsoon climate. Many think that the term “monsoon” means wet weather, when in fact it describes an atmospheric circulation pattern.
Though the annual amount of precipitation is quite similar to that of the rain forest, monsoon precipitation is concentrated into the high-sun season.
Maritime equatorial and maritime tropical air masses travel from the ocean on to land during the summer, where they are uplifted by either convection or convergence of air to induce condensation.
Locally, Orographic (Relief) uplift is an important mechanism for promoting precipitation. As air travels into the Indian subcontinent, it is uplifted by the Himalayas, causing cloud development and precipitation.
The low-sun season is characterized by a short drought season when high pressure inhibits precipitation formation.
In the case of the Asian monsoon, the replacement of the thermal low with the subsidence of the Siberian High suppresses uplift. Air masses that dominate this period are dry given their continental origin or stability.
A distinct dry season from October to May, when the temperature are lower, the interior of Asia is a region of high pressure. Wind blow over the land in a north east direction , carrying little or no moisture with them. These cool , dry North East Monsoon winds blows toward areas of low pressure and do not bring rain.
A wet season from June to September, when the wind change in direction, the wind blow in the region of low pressure. Winds blow across the equator and blow over the oceans, they are warmer and carry a lot of moisture. They bring alot of rain. Total rainfall can reach 600 mm
TROPICAL MONSOON FOREST
Found in tropical areas with a distinct dry season. Examples part of India, Bangladesh, South east Asia, China, South Central Africa, the West Indies, Central and South America and Australia.
Structure of the forest
Tropical Monsoon forest has three layered structure.
1.Canopy tree– from 25 to 30 m tall and grow closely together to form a continuous canopy layer. Epiphytes and lianas and parasitics plants are found on the canopy.
2.Understorey layer– a layer of shorter tree about 15 m.
3.Ground layer– very dense layer of shrubs.
TYPES OF TREES
Most of trees are deciduous trees which shed all their leaves over the same period of time. The trees shed their leaves during the dry season.
Tropical Monsoon forest are hardwoods
Examples are Teak and Rosewoods
Waxy, leathery and hairy broad leaves with drip tips to help the tree get rid of excessive water quickly during the wet season.
Dry season shed their leaves to prevent loss of water by transpiration.
Roots are deep to anchor into the soil firmly and provide good support for the trees. Deep roots also allow the trees to tap the underground water during the dry seasons.