Monsoon climate

A monsoon is a large scale reversal in wind direction which occurs seasonally

across SE Asia and is associated with distinct dry and wet seasons.

How is it caused?

Movement of the ITCZ

The point of max insolation alters throughout the year and the ITCZ migrates accordingly; north in June (dragging low pressure over India) and south in December (dragging high pressure over central Asia).

How is it caused?Differential heatingSummer: Intense heating

of land mass. Oceans take longer to warm. This generates pressure differences leading to SW winds (Em and Tm air masses).

Winter: Land cools rapidly. Ocean retains warmth. Pressure change is reversed and winds move from NE (Tc and Pc from desert).

How is it caused?

Summer: SW Monsoon Winter: NE Monsoon

• ITCZ dragged North

• Low pressure over India

• Land warmer than seas

• Coriolis deflects northerly winds to the East

• Heavy rains move North along west and east coasts

• East rains deflected west due to Himalayas

• ITCZ dragged South

• High pressure over C.Asia

• Land cools rapidly

• Coriolis deflects southerly winds to the West

• Dry air dries further as it moves over Tibetan Plateau

• Air warms as it descends to the Indian plains

http://www.s-cool.co.uk/a-level/geography/weather-conditions/revise-it/types-of-monsoons

How is it caused?• Pattern of rainfall in

summer monsoon is altered by topography. Western Ghats create rain shadow in central India. Himalayas have same effect for central Asia.

• Some areas of SE India and Sri Lanka receive rainfall in Winter as winds pass over Bay of Bengal and gain moisture

Arrival and retreat of the monsoon rain

• There is a stepped progression and recession of the monsoon rains as they cross India.

• Sri Lanka usually has monsoon rainfall in early May whereas in Pakistan it is July.

• In winter, the retreat begins in September but will not reach Southern India until November

Monsoons and climate change

• The key question lies with the ability of the affected nations to cope with the changes –India, Pakistan, Bangladesh, Myanmar

• Half of global population rely on annual monsoon to bring water for agriculture

• Variations of timing and intensity will affect billions of people

• Frequency has increased (10%) since 1950s, severe rains have doubled

• Impacts of heavy rains – flash floods and landslides – if these intensify the agriculture suffers

• End of 21stC temps up 3C – some areas get more rain, others suffer drought

• Increases in cholera, hepatitis, malaria

Bangladesh

• Temperature up 1.5-2.0C by 2050

• Annual increase in precipitation of 10-15% by 2050

• More frequent and severe cyclones – why?

• Increased river discharge – why?

• Sea level rise of 3mm per year (world average is 2mm) and 1m by 2050 (15% loss of land)

• 13-30m people displaced

• Rice crop yield down 30%

• Mass migration to NE.India leading to?

• Coral reefs damaged

• Loss of Sundarban Islands – unique ecosystem (mangroves) biggest carbon sink in region, supports Bengal Tiger, Indian Python, Estuarine Crocodile

Responses to climate change

• No carbon emission restrictions – based on comparative levels and popn (4th globally)

• Investment in drought/flood resistant crops

• Increase photovoltaic production to 1 gigawattper year. 4 companies in the photovoltaic business have set up in 'Fab City', a proposed semiconductor-making hub outside Hyderabad

• Integrated Coastal Zone Planning – restoration of coral reefs and mangrove planting

• National Cyclone Risk Mitigation Programme

– Coastal zone mapping of topography to identify areas at high risk

– Construction of shelters and early warning systems

• Rajiv Ghandi plan to connect 79 million rural home to electricity – why?

• India’s Solar Mission - decentralised power including large scale and domestic generation