Notice that most precipitation occurs in the tropics and swings north and south of the equator with the seasons. This seasonal shift in the location of tropical precipitation indicates a shift in the location of the ITCZ and is the reason why there are distinct wet and dry seasons on tropical continents.
Patterns of precipitation through the year Image: University of Oregon. From December until February, the monsoon rains move south of the equator towards Australia while South Asia experiences dry monsoon conditions. There is even an East Asian monsoon that brings summer rain to China, Japan, and Korea, but it is caused by a different type of wind pattern associated with the jet stream.
Monsoons bring large amounts of rain to a location, often leading to large-scale vegetation growth. Image: University of Oregon. Monsoon winds in the tropical parts of North America, Central America, and South America cause the amount of rainfall to vary with the seasons, even in areas where precipitation is plentiful and rainforests thrive.
From June to August, which are summer months in the Northern Hemisphere, there is more rainfall north of the equator in Costa Rica, Nicaragua, Panama, and western Mexico. From December to February there is more rainfall south of the equator in Brazil. The North American monsoon does bring moisture from the warm waters of the Pacific into the U. Southwest, but its peak rainfall occurs in Mexico, and the U. These areas are typically dry but can receive enough rainfall to quell a wildfire if moist monsoon winds blow in summer.
An area of summer rainfall along the U. East Coast is associated with what some might call a mid-latitude version of monsoon rainfall. Meanwhile, sub-Saharan Africa becomes particularly hot and dry in winter as air descends from high in the atmosphere to the ground as part of the Hadley Circulation.
The locations of the heaviest tropical rainfall from December to February top and June to August bottom. Images: UCAR. Rajeev told the Indian press on Friday June 12, , after a full night of rain. He referred to winds even though people cared more about the rains that had just started. Air warmed in the tropics rises, flows towards the poles, then downward in the subtropics, and back to the equator.
Image: UCAR. Sunlight, and the energy it brings to Earth, is the driving force behind the Hadley Circulation. Sunlight heats land and ocean surfaces near the equator.
The warmed surface releases energy into the atmosphere, in the form of heat and evaporated water. As it flows toward the poles, this air cools and drops down toward the surface of the Earth in the subtropics, near 30 degrees latitude north or south of the equator. As air rises near the equator and then flows poleward, it leaves an area of fewer air molecules at the equator.
This is a region of low pressure because there is a smaller mass of air left over the equator. Air from the subtopics, north and south of the equator, flows in to fill the space, completing the loop of Hadley Circulation. Water vapor condenses as air rises and cools in the ITCZ, forming clouds and falling as rain. The ITCZ can be seen from space as a band of clouds around the planet.
This is where monsoon rainfall occurs. If the Earth were not rotating, winds would blow directly towards the Intertropical Convergence Zone from the north and south. But the Earth is rotating — making a full turn on its axis each day — which turns the wind to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It also affects the movement of ocean currents and the direction of rotation in hurricanes.
The onset and strength of a monsoon are hard to predict, but once they start the altered winds can remain in place for months. Monsoons can often bring significant rainfall increases but this is dependent on the geography of the particular place. The rain associated with monsoons can differ depending on where you are, but precipitation can sometimes last for days without stopping. Large expanses of rolling grasslands known as savannas generate their own climate, bringing hot weather all year round.
There are distinct dry seasons, where no rain will fall at all for months. Then short wet seasons, bringing heavy rains most afternoons, with hot, humid conditions throughout the rest of the day. Diseases such as cholera, dengue, malaria, as well as stomach and eye infections are also more prevalent in the summers with heavier rains according to World Monsoons.
Many of these diseases are spread though water systems that have been overloaded and have been unable to clean the water used for drinking, cleaning, and so on. The North American Monsoon System also brings the start of the fire season in the southwestern United States and northern Mexico, according to NOAA report due to the increased amount of lightning brought on by pressure and temperature changes.
The amount of lightning, up to tens of thousands of strikes per night in some regions according to the study, not only brings fires to the region but also power disruptions, and severe injuries. According to a study by Yen Yi Loo, Lawal Billa, and Ajit Singh , a group of scientists from Malaysia, published in Geoscience Frontiers in , the effects of global warming on a monsoon can potentially be devastating due to frequent shifts and changes in precipitation levels and timelines.
World Monsoons estimates that there will be an increase in rainfall during the summer monsoon seasons in the next 50 to years. Greenhouse gases, such as carbon dioxide, can make warm air hold onto more water only to release it as rain over already soaked areas. During the dry winter monsoon seasons, it is believed that the land will become drier as evaporation increases in warmer temperatures.
On shorter timescales, the amount of rainfall during a summer monsoon may be changed year to year by a variety of factors including air pollution, according to World Monsoons. Much of this research is going into how to better predict future and current rainfalls and winds, such as described in an article published in on Science Daily from the Office of Naval Research. The greater the knowledge about the workings of a monsoon, the more accurately the onset and strength can be predicted.
When approximately half of India's population works in agriculture and agriculture makes up eighteen percent of India's GDP, according to Stratfor , for example, the shifting in both timing of a monsoon and the amount of rain, can lead to big problems.
With all of the ongoing research, perhaps the problems can turn into solutions. This huge monsoon wind system then stretches into the Indian Ocean. Finally, it reaches its end on the Indian coast of Africa.
Monsoon winds exist in other parts of the world, too. The North American monsoon happens once a year, usually in the middle of summer. Warm, moist air from the Gulf of California blows northeast, while warm, moist air from the Gulf of Mexico blows northwest. These two winds meet over the Sierra Madre Occidental mountains in central Mexico. The monsoon brings moisture to the mountain ecosystem before continuing north to the U.
The North American monsoon can be a natural aid to firefighter s. Summer temperatures in Arizona regularly reach more than degrees Fahrenheit, making wildfire s difficult to contain. The North American monsoon is also the primary water source for most desert ecosystems in the region. However, it can also confuse and interrupt daily life for people and businesses not used to dealing with heavy rain.
Also known as the Monsoon Zone. Monsoon usually refers to the winds of the Indian Ocean and South Asia, which often bring heavy rains. Summer Monsoon The summer monsoon is associated with heavy rainfall. Winter Monsoon The Indian Oceans winter monsoon, which lasts from October to April, is less well-known than its rainy summer equivalent.
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