Chapters :


El Nino
  • El Nino refers to the unusual warming of the central and east-central equatorial Pacific Ocean which affects global weather. The warmer waters of the Pacific Ocean cause the winds in various regions to reverse, like the trade winds that come towards India.
  • This change of wind direction leads to warmer winters and summers and a decrease in rainfall during the monsoon. Most of the time, it also leads to drought.
  • There is also an opposite of an El Niño, called La Niña means The Little Girl in Spanish. This refers to times when waters of the tropical eastern Pacific are colder than normal and trade winds blow more strongly than usual.
  • Collectively, El Niño and La Niña are parts of an oscillation in the ocean-atmosphere system called the El Niño-Southern Oscillation, or ENSO cycle.
Effects of El Nino
  • El Nino affects global weather. It favors eastern Pacific hurricanes and tropical storms.
  • Recorded unusual rainfall in Peru, Chile, and Ecuador are linked to the climate pattern.
  • El Nino reduces the upwelling of cold water, decreasing the uplift of nutrients from the bottom of the ocean. This affects marine life and sea birds. The fishing industry is also affected.
  • Drought caused by El Nino can be widespread, affecting southern Africa, India, Southeast Asia, Australia, and the Pacific Islands. Countries dependent on agriculture are affected.
  • WHO report on the health consequences of El Nino forecasts a rise in vector-borne diseases, including those spread by mosquitoes, in Central and South America. Cycles of malaria in India are also linked to El Nino.
  • Over India, the El Nino has usually been the harbinger of drought and the La Nina of rain

Sustained variations in the difference between tropical western and eastern Indian Ocean surface temperatures are referred to as the Indian Ocean Dipole or IOD. It is also known as the Indian Niño, is an irregular sea – surface temperature oscillation in which the western Indian Ocean alternately becomes warmer and colder than the eastern part of the ocean. IOD and Indian Monsoon The Indian monsoon rainfall is influenced by a system of oscillating sea surface temperatures known as the Indian Ocean Dipole (IOD) in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean. A positive IOD leads to greater monsoon rainfall and more active (above normal rainfall) monsoon Local Winds  Differences in the heating and cooling of earth surfaces and the cycles those develop daily or annually can create several common, local or regional winds. Introduction to Land and Sea Breeze Take a walk along a dry beach on a hot early afternoon. No sooner than putting your barefoot in the sand, you start hopping and jumping and immediately run towards the sea to soak your scorching feet in the water. Yes, the sun heats both of them up. However, land and water do not heat up or cool down at the same pace. This differential heating and cooling of land and sea give rise to what are known as breezes, in the coastal areas. There are two types of breeze:
  • Sea Breeze
  • Land Breeze
What is Sea Breeze? This process takes place for the duration of the day. Both the sea, as well as the land surface is heated up by the sun.  The sea heats up slower than the land because it has a much higher heat capacity.  Thus, the temperature over the land surface increases, in turn, heating up the air around it.  An expansion occurs in the less dense warm air and an area over the land having low pressure is developed. At the same time on the top of the sea, a high-pressure area develops.  Due to the difference in pressure and the air flows from the high pressure over the sea to the low pressure over the land.  This flow of air from the sea to the land is termed as the sea breeze. Sea breeze is more prevalent on warm sunny days during the spring and summer. An amazing cooling effect and a noticeable temperature drop are experienced as a consequence of it.

What is Land Breeze?

This process takes place for the duration of the night and the above-mentioned process gets reversed.  Both, the land as well as the sea starts cooling down when the sun sets.  As the heat capacity of land is different than the sea it cools down quicker.  Thus, a low-pressure situation develops over the sea as the temperature above it is higher when compared to the land. Due to this, the air flows from the land to the sea which is termed the land breeze. Land Breeze Land breeze can occur at any time of year but are more prevalent during the fall and winter seasons when water temperatures are still fairly warm and nights are cool
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