Query: Most of the atmospheric moisture originates in the tropical ocean, and the difference between surface and upper atmospheric temperature determines how much of the moisture rises into the atmosphere.

Relevant passages:
Extratropical cyclone <=SEP=> Extratropical cyclones , sometimes called mid-latitude cyclones or wave cyclones , are low-pressure areas which , along with the anticyclones of high-pressure areas , drive the weather over much of the Earth . Extratropical cyclones are capable of producing anything from cloudiness and mild showers to heavy gales , thunderstorms , blizzards , and tornadoes . These types of cyclones are defined as large scale ( synoptic ) low pressure weather systems that occur in the middle latitudes of the Earth . In contrast with tropical cyclones , extratropical cyclones produce rapid changes in temperature and dew point along broad lines , called weather fronts , about the center of the cyclone .

Low-pressure area <=SEP=> A low-pressure area , low , or depression is a region where the topographic map is atmospheric pressure is lower than that of surrounding locations . Low-pressure systems form under areas of wind divergence that occur in the upper levels of the troposphere . The formation process of a low-pressure area is known as cyclogenesis . Within the field of meteorology , atmospheric divergence aloft occurs in two areas . The first area is on the east side of upper troughs , which form half of a Rossby wave within the Westerlies ( a trough with large wavelength that extends through the troposphere ) . A second area of wind divergence aloft occurs ahead of embedded shortwave troughs , which are of smaller wavelength . Diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below , which lowers surface pressures as upward motion partially counteracts the force of gravity .   Thermal lows form due to localized heating caused by greater sunshine over deserts and other land masses . Since localized areas of warm air are less dense than their surroundings , this warmer air rises , which lowers atmospheric pressure near that portion of the Earth 's surface . Large-scale thermal lows over continents help drive monsoon circulations . Low-pressure areas can also form due to organized thunderstorm activity over warm water . When this occurs over the tropics in concert with the Intertropical Convergence Zone , it is known as a monsoon trough . Monsoon troughs reach their northerly extent in August and their southerly extent in February . When a convective low acquires a well-hot circulation in the tropics it is termed a tropical cyclone . Tropical cyclones can form during any month of the year globally , but can occur in either the northern or southern hemisphere during November .   Atmospheric lift will also generally produce cloud cover through adiabatic cooling once the air becomes saturated as it rises , although the low-pressure area typically brings cloudy skies , which act to minimize diurnal temperature extremes . Since clouds reflect sunlight , incoming shortwave solar radiation decreases , which causes lower temperatures during the day . At night the absorptive effect of clouds on outgoing longwave radiation , such as heat energy from the surface , allows for warmer diurnal low temperatures in all seasons . The stronger the area of low pressure , the stronger the winds experienced in its vicinity . Globally , low-pressure systems are most frequently located over the Tibetan Plateau and in the lee of the Rocky mountains . In Europe ( particularly in the United Kingdom ) , recurring low-pressure weather systems are typically known as `` depressions '' .

Water vapor <=SEP=> Water vapor , water vapour or aqueous vapor is the gaseous phase of water . It is one state of water within the hydrosphere . Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice . Unlike other forms of water , water vapor is invisible . Under typical atmospheric conditions , water vapor is continuously generated by evaporation and removed by condensation . It is lighter than air and triggers convection currents that can lead to clouds .   Being a component of Earth 's hydrosphere and hydrologic cycle , it is particularly abundant in Earth 's atmosphere where it is also a potent greenhouse gas along with other gases such as carbon dioxide and methane . Use of water vapor , as steam , has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution .   Water vapor is a relatively common atmospheric constituent , present even in the solar atmosphere as well as every planet in the Solar System and many astronomical objects including natural satellites , comets and even large asteroids . Likewise the detection of extrasolar water vapor would indicate a similar distribution in other planetary systems . Water vapor is significant in that it can be indirect evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects .

Monsoon of South Asia <=SEP=> The monsoon of South Asia is among several geographically distributed global monsoons . It affects the Indian subcontinent , where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September . Yet it is only partly understood and notoriously difficult to predict . Several theories have been proposed to explain the origin , process , strength , variability , distribution , and general vagaries of the monsoon , but understanding and predictability are still evolving .   The unique geographical features of the Indian subcontinent , along with associated atmospheric , oceanic , and geophysical factors , influence the behavior of the monsoon . Because of its effect on agriculture , on flora and fauna , and on the climates of nations such as Nepal , India , Bangladesh , Bhutan , Pakistan , and Sri Lanka -- among other economic , social , and environmental effects -- the monsoon is one of the most anticipated , tracked , and studied weather phenomena in the region . It has a significant effect on the overall well-being of residents and has even been dubbed the `` real finance minister of India . ''