Climatic Dynamics of Monsoons – NASA SVS (2016)

The monsoon was noticed for the first time in India. It is a seasonal rain and wind pattern that occurs in many places on our planet. The quasi-regular atmospheric pattern is hugely influential in Human history. The first truly global economy was established in the Indian ocean by sea faring merchants who traveled from Africa and middle east all the way to Indonesia and Malaysia and back. Predictability of the wind patterns around the Indian Ocean was the defining factor. Take for instance the sugar trade. Arab sailor merchants brought sugar everywhere in the old world. Until the discovery of the new world Ottomans controlled its trade. Sugarcane completed it’s world journey a few centuries ago when it was brought to the Americas.

Scientific history of the monsoons began with Edmond Halley (1656-1742) who constructed a marvelous first map of major winds on a global scale. On his map, he particularly paid attention to the fine detail of the wind directions around India. Monsoon is an atmospheric phenomenon largely driven by winds therefore, his account and map became foundational. Halley hypothesized that the easterly winds alternating between northeast and southeast were caused by the diurnal cycle of the sun.

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Edmund Halley’s work was furthered by Henry Francis Blanford (1875-1889) who realized that Indian Monsoon was a recurring large scale climatic event. In 1864, cyclones hit eastern India, killing 70,000 and damaging the port of Calcutta. After this catastrophe, Blanford worked to establish a system of storm warnings in India. Blanford was appointed Imperial Meteorological Reporter and placed in charge of the Bengal Province Meteorological Department.

His long-term weather observations enabled him to make a connection between the snow status in the Himalayas and rainfall in the continental India. Based on his observations, in 1885, he was able to predict a monsoon season that will deliver less rainfall than expected and coined the term “deficient monsoon.” Blanfords prediction of drought was noticed by the Australian meteorologist Charles Todd and when another drought occurred in 1888, he realized that there was a synchrony in the events. This was examined later by Gilbert Walker who recognized the global scale of weather phenomena.

Monsoon predictions formed the foundation for the predictions of other large scale atmospheric events such as Atlantic hurricanes, North Atlantic Oscillation (NAO) and El Nino Southern Oscillation (ENSO).

Satellites and computerized climate models can help predict the monsoon patterns with more accuracy. Rains generated by monsoon rains support natural ecosystems and provide water essential for human activities like agriculture. Excess precipitation causes disasters in the region, including flooding of the major rivers and landslides. It is essential to understand how monsoons develop to minimize losses.

During the summer the land gets hotter, heating the atmosphere and pulling in cooler, moisture-laden air from the oceans. This causes pulses in heavy rainfall throughout the region. In the winter the land cools off and winds move towards the warmer ocean and suppressing rainfall on land. This pattern occurs in many parts of the World including North America and Australia. In fact, scientists suggest that monsoon rainforests in Australia have expanded within the savanna matrix. The expansion of tropics has been reported throughout the tropics worldwide. The expansion in Australia is thought to be linked to a long-term trend towards wetter climates, atmospheric CO2 enrichment, and changed fire regimes.

If you would like to see weather patterns interactively from all over the world including the surface temperatures and wind directions (and many more weather-related parameters) in real time check out the Earth School website.

World Meteorological Organization’s Southeast Asian Monsoon forecast:
http://www.climatecentral.org/gallery/maps/2016-south-asia-monsoon-outlook

 

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