Table of Contents
What is Monsoon?
The term monsoon is derived from the Arabic word “mausim” which means season therefore, monsoon is a seasonal wind system in which there is a complete or almost complete shift in wind direction from summer to winter; this is due to the temperature differential between the adjacent land and sea. This wind system is usually associated with the Indian ocean which has a direct impact on the tropical weather. The monsoon winds are large-scale sea breezes that blow from cold to warm region
Monsoon season is often accompanied by a corresponding change in atmospheric circulation and precipitation in the summer rain such as the Indian subcontinent rain. The strongest monsoons tend to occur in Asia specifically in South and Southeast Asia. However, monsoon climate is also found to prevail in China, Philippines, Taiwan, Japan, Korea, the Northern coast of Australia, Malaysia in the south, southern parts of North America, Central America, northern areas of South America, and in western Africa. The monsoon that occurs in North America is not as strong as those in India due to a lower and smaller plateau, but the same patterns are followed even in other regions.
Causes of Monsoon
The vastness of Asia, the height of the Himalayas mountain and the location of the warm water in the south-eastern part create great differences in temperature between the landmass and the water bodies. This difference in temperature is the actual cause of the formation of the monsoon season.
Types of monsoons
- Summer monsoon
- Winter monsoon
- The North American Monsoon
- European Monsoon
- Australian monsoon
- Africa Monsoon
The summer monsoon or southwest monsoon is explained thus:
In summer the intense heating of the Asian continent by the sun causes air to expand and rise, when this happens, it lowers the air pressure and consequently sucks in air from the southern hemisphere, causing winds from the south to cross over to the equator. This creates the opposite effect of the Coriolis force in the northern hemisphere, causing it to change direction by over 90, resulting in the southwest monsoons. These winds are not only humid, but they have the ability to also travel a long distance over the Indian and the Pacific Ocean and as such gathers a lot of moisture. When these winds pass over the land, they are forced to rise, which causes them to cool and give up their moisture in the form of torrential rainfall. This usually starts in the southwest and move towards the northeast in the period of June to September.
Some other times, the shift in the wind directions can bring a “dry monsoon,” which could result in drought in the regions near the zone of the ocean. As this air starts on the landmass, it is dry and it doesn’t contain any water vapor. This is why the Central and South Asian regions remain very dry in winter.
The summer monsoon supplies three-quarters of the country’s yearly precipitation. These winds bring heavy rains towards the end of the summer due to high pressure concentrated in the Indian Ocean.They are winds that give maximum rainfall to India and to South and East Asia, they blow from the Indian Ocean to the warmer land. Most of the food production in India depends on these monsoons because of the abundance of rain comes with.
Winter monsoon or retreating monsoon is also called a northeast monsoon, is the opposite of the summer monsoon. These winds occur from October to December when the surface high-pressure system is strongest. In this monsoon, the winds reverse and blow in a land-to-ocean circulation just like the land breeze system. As the landmasses cool faster than the oceans, an excess in pressure builds over the continents causing the air over land to have higher pressure than that over the ocean. As a result, cold air over the land flows to the ocean and warm air moves from the ocean to the land. With this, air pressure begins to build over northern India, the Indian Ocean, and its surrounding atmosphere still holds its heat. This causes the cold wind to sweep down from the Himalayas and Indo-Gangetic Plain towards the vast spans of the Indian Ocean south of the Deccanpeninsula.
Northeast monsoon blows from land to sea unlike the southwest monsoon which blows from sea to land and it is generally less strong, cooler and drier (compared to the Summer Monsoon weather), with prolonged periods of successive cloudless days.Meanwhile, when this blows over the Bay of Bengal it acquires a great amount of water moisture and ultimately causes shower to the coast of Sri Lanka and Tamil Nadu. This air, however, when crosses the equator according to Ferrels Law blows over North Australia as the northeast monsoon and acquires a large amount of water moisture from the Indian Ocean causing heavy shower over northern Australia.
The North American Monsoon
This usually occurs in the middle of the summer once in a year when warm, moist air from the Gulf of California blows northeast and warm, moist air from the Gulf of Mexico blows northwest as a reverse. These two winds come in contact with each other at the Sierra Madre Occidental mountains in central Mexico. The monsoon releases moisture on the mountain ecosystem before reversing north to the U.S. states of Arizona, New Mexico, and Texas. Central Mexico and parts of the American Southwest receive heavy seasonal rains, but consistent winds are not present hence they don’t meet the condition of a true monsoon. The North American monsoon is the main source of water for most desert ecosystems in the region. However, when the water becomes too much, it interferes with the daily life and the economic activity of the people who are not used to very heavy rain.
Europe experienced severe summer thunderstorms, and the winds can change direction from summer to winter, this is happening due to the reappearance of westerly winds from the Atlantic which hits parts of Europe’s Northern Atlantic coastline, more precisely Ireland,Great Britain,Western Germany,Northern France, the Benelux countries and parts of Scandinavia. The westerly winds are common event during the winter in Europe only that they disappear at the time of spring (in late March and through April and May) and then starts all over again in June. For this reason, it is referred to as the s “the return of the westerly.
This is also called Indo-Australian Monsoons and is associated with the inflow of moist west to northwesterly winds which flows into the monsoon trough, producing convective cloud and heavy rainfall over northern Australia. These moisture-laden winds begin at the Indian Ocean and southern Asian waters. The north Australian wet season covers the monsoon months but can extend several months on either side. It generally starts from December all through the month of March and it is a major source of energy for the Hadley circulation during boreal winter. The Australians depend on the arrival of the monsoon rain for their agricultural and other economic activities.
Africa (West African and Southeast African Monsoon
Africa also experiences some weather patterns that show some seasonal differences from time to time. The two main types of African Monsoons are the West African Monsoon, which prevails during the Northern Hemisphere Summer (June through September), and the East African Monsoon with rains during spring and autumn. This monsoon is greatly fueled by the seasonal shifts of the Inter tropical Convergence Zone and the great seasonal temperature and humidity differences between the Sahara and the equatorial Atlantic Ocean.It migrates northward from the equatorial Atlantic in February, reaches western Africa on or near June 22, then moves back to the south by October. The dry, north easterly trade winds, and their more extreme form, the harmattan, are interrupted by the northern shift in the ITCZ and resultant southerly, rain-bearing winds during the summer.
Characteristics of the monsoon
- Monsoon is a seasonal wind in which there is a complete or almost complete reversal of wind direction. there is also a change in the characteristics of the monsoon wind.
- Due to the change the wind direction, the winter remains dry as it originates in the landmass and while crossing the ocean, It absorbs moisture and brings abundant rainfall on the landmass in summer.
- Monsoon is characterized by a sudden downpour of rainfall activity which extends inland in stages and may cover the entire country by the middle of July.
- Flood and drought usually take place within the same year in different parts of the country.
- However, the winter monsoon causes rainfall in the north-east coast of Sri Lanka, on the coast of Tamil Nadu, in West Japan and in the east coast of the Philippines.
- Monsoon rainfall is seasonal and it occurs between June and September over a short period of time.
- It is due to the effect of the monsoon, that the temperature is less between the winter and the summer in the low latitudes.
- The durability and intensity of monsoon in winter differ with the variation of the regions, for example, the intensity of winter is moderate in central Bangladesh and is simply unbearable in northern India during the same period.
- The intensity of winter is well felt in the mid-latitudes. During this time, the cold continental air mass can reach the mid-latitudes. The mid-latitudinal regions come under the influence of tropical air mass in summer. So, hot weather prevails there
Importance of Monsoon
- Monsoon season is widely beneficial and appreciated by city-dwellers, as it is a welcome relief from the climax of summer heat in June.
- The monsoon is important in many areas all around the world, the change in direction establishes a seasonal pattern of rainfall in summer in which many farmers depend for their cultivation of crops.
- The monsoon season is vital for the cultivation of oilseeds, cotton, and rice. Rice is mainly grown in the monsoon season in India. It can thrive in waterlogged soil, sustain submergence to an extent, and can moderately tolerate salinity, but cannot withstand drought.
- The summer monsoon is also important as hydroelectric plants highly depend on the abundant water collected during the monsoons for the production of electricity. electrical plants are driven by water collected during the monsoons.
- Large production of food crops is highly dependent on the monsoon season, this enables the import trades to take place without having to export food from the neighboring countries.
Effects of Monsoon
- The impact of monsoon climate is not the same everywhere, it can be mild in one region and very severe in other regions. For instance, if rains start late, or not heavy enough or too heavy, it can change the agricultural patterns and cause damages to people and the infrastructure in the affected areas.
- Prolonged monsoon season always results in waterlogged of houses and roads especially in slums even within the cities where drainage systems are created could be prone to flood.
- Changing the climate pattern of monsoon often leads to the destruction of the city’s infrastructure which could result in severe economic loss including damage to property and loss of lives. This is a similar occurrence that took place in 2005 flooding in Mumbai
- During very dry seasons such as the dry winter monsoon seasons, the rate at which evaporation occurs is usually too much, therefore the land will become drier as the evaporation increases. In warmer temperatures, lack of water as you all know reduces crop yields and gives rise to famine.
- Very heavy rain in the summer comes with massive flooding and landslides washing away not just the crops and homes but destroys many people and animals as well. However, The regions with very heavy flooding are prone to diseases outbreak and are mostly waterborne, some of these diseases that are likely to occur include cholera, dengue, malaria. Stomach and eye infections are more prevalent in the summers with heavier rainfall.
- During the winter when there is drought many animals starve due to little or lack of water and many farmers find it difficult to produce enough food for themselves and to supply to the dependent population, however, food is then imported from other parts of the world which significantly affects the income and well-being of many farmers and the state as well.
- Another impact of the monsoon season is the occurrence of bush fire, this is very common in the region of North American, southwestern United States and northern Mexico, the bush fire is linked to an increased amount of lightning brought on by a change in pressure and temperature of the wind. In areas where the lightning strikes repeatedly may result in severe injuries to humans, animals, and disruption of electrical wires and poles.