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You cannot download interactives. Weather is the state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloud cover. It differs from climate, which is all weather conditions for a particular location averaged over about 30 years.
Weather is influenced by latitude, altitude, and local and regional geography. It impacts the way people dress each day and the types of structures built.
Explore weather and its impacts with this curated collection of classroom resources. Catastrophic weather events include hurricanes, tornadoes, blizzards, and droughts, among others. As these massively destructive and costly events become more frequent, scientific evidence points to climate change as a leading cause. While they can often be predicted, the loss of life and property take an emotional and economic toll on the community impacted.
Explore these resources to teach your students about catastrophic weather events and how they impact every part of the world. Floods are events where water overflows onto land that is typically dry. This can occur when there is a large amount of rain, rapid snow or ice melt, a blast of water onto a coastline during a storm, or the failure of manmade infrastructures, such as dams or levees.
Floods are among the most expensive and frequent natural disasters in the United States, and as the impacts of climate change are more acutely felt, floods are expected to worsen.
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Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. 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.
The rice paddies of Southeast Asia depend on the seasonal monsoon. Photograph by James P. Asian-Australian monsoon. Monsoon Cup. Monsoon Zone. Also called a mudflow. The Asian monsoons mirror a similar antiphased and less intense seasonal climate system affecting northern Australia and New Guinea. The summer wet season progressively advances across each region but typically commences in April—May, finishing in September—October.
Even distant tectonic changes have contributed to the evolution of the Asian monsoon, producing widely varying climate conditions in different regions. Uplift of the Tibetan Plateau and the Himalayan mountains, driven by the collision of the Indian subcontinent with the Eurasian plate starting some 55 million years ago, has exerted significant influences on numerous physical phenomena across the region, including profound effects on the weather.
Conference attendees presented several examples of these effects. For example, the topographic barrier of the Himalayas strengthens the SAM, but it reduces rainfall across the Arabian Sea.
The growth of the Tibetan Plateau, meanwhile, may have a bigger impact in East Asia. The closure of the Tethyan oceanic gateway, for example, which separated the Mediterranean Sea from the Indian Ocean about 14 million years ago Ma , is seen as critical to the establishment of the Somali Jet, a strong air current that flows along the northeastern African coast and affects the monsoon by limiting the advance of the summer rain front.
And uplift in Siberia and Mongolia over the past 10 million years may have affected the winter monsoon. Oxygen isotope data in foraminifers can be corrected for global isotope changes and local temperature to isolate the effects of freshwater dilution from the Yangtze River, a relatively simple rainfall proxy.
This adjusted record of discharge implies that the EAM is more sensitive to greenhouse gas concentrations and high-latitude ice sheet forcing than solar heating of the continent, as previously proposed. Beginning about 13 Ma, the SAM winds began to strengthen, a phenomenon that is probably linked to the establishment of the East Antarctic ice sheet. The presence of this ice sheet strengthened the interhemispheric temperature gradient, leading to intensification of atmospheric and ocean circulation.
This change was followed by cooling of the Indian Ocean from 8 to 6 Ma. Together these effects reduced rainfall along the Himalayas but increased rainfall in peninsular India, the southern South China Sea, and Australia.
Freshening of the Arabian Sea at that time is linked to cooling and to Northern Hemisphere ice sheet expansion. Runoff from the Ganges-Brahmaputra and Irrawaddy Rivers, which is correlated with precipitation levels, increased after 5.
More recently, major changes occurred in monsoon cyclicity through the Mid-Pleistocene Transition, a significant shift in the behavior of glacial cycles that occurred 1.
It is clear that the Australian monsoon, which is linked to the Asian monsoon, follows a cycle that is driven more strongly by insolation, compared with the SAM and EAM.
The Australian monsoon and the SAM follow cycles that are antiphased: One cycle reaches its maximum rainfall and wind speed at the same time the other reaches its minimum.
Paleoprecipitation reconstructions based on leaf wax records indicate that the Himalayas were exposed to a wet monsoon through most of the Miocene 23—8 Ma , and precipitation levels were then relatively stable through the Pliocene until the beginning of the Pleistocene about 2.
Just as the uplift of the Himalayas and the Tibetan Plateau influenced the monsoons, the strength of the monsoons influenced the erosion of the Himalayas. The amount of carbonate minerals washed into the Bengal Fan , a submerged river delta in the Bay of Bengal, from weathered rocks upstream peaks at 5—13 Ma in the stratigraphic record, a further suggestion that the monsoon was especially strong during this period.
This discharge of carbonate-rich material coincides with erosion of the Tethyan Himalayas and initial unroofing tectonic and erosional removal of overlying units of the Lesser Himalayas after 8 Ma.
But the winter monsoon, where dry conditions prevail, is part of the pattern too. During winter, air descends over tropical continents as the part of the Hadley Circulation that is outside of the ITCZ. Descending air causes high pressure, and makes clouds and rain uncommon. The dry conditions during winter can even lead to drought if they are too intense or persist for too long.
Geography affects the amount of rainfall that an area receives as the ITCZ moves through the seasons. Low-level winds blow south towards the ITCZ, picking up moisture as they move over the warm, tropical ocean.
Meanwhile in India, dry air descending over land means there is little precipitation. During Northern Hemisphere summer, the ITCZ is north of the equator and monsoon rains fall in India and other parts of south Asia as winds blow north from the tropical ocean to the land, while northern Australia experiences very dry conditions as air descends.
When intense summer sunlight hits land, its energy is absorbed and transferred quickly back into the atmosphere. This means that, in summer, air over land is heated more than air over ocean, which shifts the ITCZ toward land regions.
In regions where continents lie north or south of the equator, as in Asia and Australia, this causes the ITCZ to shift farther off the equator during the summer season.
There is year-to-year variation in the amount of monsoon rainfall during summer. While this is a general pattern, it cannot be used to indicate exactly how much rain will fall in India in any particular summer.
So there must be other influences on the amount of rainfall, too. This is an area of active research. Rains will likely increase in wet regions as climate warms because warm air can hold more water; if the winds do not change, more water vapor in the atmosphere will produce more rain in the ITCZ.
Over ocean, where there is abundant water supply for the atmosphere, this is quite likely, but it is less clear how the amount of rain may change over land as climate warms. Whether or not winds will change enough to have a large effect on the rainfall is also unclear. During the dry season, land is expected to become drier because evaporation from land will increase in a warmer climate.
At the same time that rainfall is changing due to global climate change, natural year-to-year variability is happening as well. Other changes to the amount of rainfall may be caused by air pollution such as tiny particles released as coal, oil, and gas are burned. The amount of monsoon rain that falls each year is highly variable, according to records of rain in India collected since the s.
In parts of India monsoon rainfall has decreased some since Meanwhile, in the Philippines and other areas of the western North Pacific, the amount of monsoon rain has increased. Weak monsoon rains produced drought and famine over large parts of Africa in the s and s, but the West African monsoon rains have recovered somewhat since then. So there is evidence that monsoons are changing, but researchers are still investigating how the amount of monsoon rainfall will be affected by climate change in the future.
Farmers in monsoon regions rely on the wet summer months to grow crops. However the summer monsoon does not always bring the same amount of rainfall, and variations in rain have implications for agriculture and the economy. For example, in very little rain fell during the summer monsoon in India. In some areas rainfall was half of what is typical during the wet season and farmers could not plant their crops.
Farm animals starved; many were sold for a fraction of what they would have normally been worth because farmers were desperate. From wheat and rice to vegetables, cotton, and tea, Indian farmers grow a wide range of crops and the country uses more land for crops than any other country in the world million acres.
Crops depend on rain and, in India, more than three quarters of the annual rainfall occurs during the four months of the summer monsoon season. But during years when there is less rainfall than usual, crops die in the fields or cannot be planted at all. Take a look at the graphs to the left to see how the amount of grain crops produced by farmers in India including wheat, rice, and barley relates to the amount of rainfall.
While too little rainfall during the summer monsoon can cause dire conditions for farmers on land, too much rainfall and overly strong winds can make coastal waters unsafe, preventing fishermen throughout South Asia from heading to sea to catch the fish they depend on for income.
Monsoon rains can be harnessed as hydropower, a valuable energy resource. Reservoirs are filled during the summer monsoon rains and then the water is gradually released through dams, turning turbines to create electricity year-round. During years when there is little monsoon rainfall, the reservoirs are not replenished, limiting the amount of hydroelectric power produced during the year.
Because regions with a monsoon climate have distinctly wet and dry seasons, they are prone to floods and droughts, both of which are hazardous to health. During summer monsoons, heavy rainfall can cause flooding. Powerful floodwaters can drown victims and damage buildings, leaving people without homes and vulnerable to the elements.
During the summer monsoon in Pakistan and India, nearly people lost their lives during landslides and home collapses. Yet the main health hazards during summer monsoon season are diseases like cholera, dengue, chikungunya, and malaria, as well as stomach and eye infections.
Each year, as the summer monsoon season approaches, Indian hospitals prepare for high numbers of patients with these illnesses. When floods cause water purification systems to become compromised, diseases like cholera can spread through unclean drinking water.
Also, mosquitos that carry disease breed in open containers that fill with rainwater — from large water barrels and ponds to small coconut shells.
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