The stronger the area of low pressure, the stronger the winds experienced in its vicinity. At night the absorptive effect of clouds on outgoing longwave radiation, such as heat energy from the surface, allows for warmer night-time minimums in all seasons. Since clouds reflect sunlight, incoming shortwave solar radiation decreases, which causes lower temperatures during the day. Tropical cyclones can form during any month of the year globally but can occur in either the northern or southern hemisphere during December.Ītmospheric lift will also generally produce cloud cover through adiabatic cooling once the air temperature drops below the dew point as it rises, the cloudy skies typical of low-pressure areas act to dampen diurnal temperature extremes. When a convective low acquires a well-hot circulation in the tropics it is termed a tropical cyclone. Monsoon troughs reach their northerly extent in August and their southerly extent in February. When this occurs over the tropics in concert with the Intertropical Convergence Zone, it is known as a monsoon trough. Low-pressure areas can also form due to organized thunderstorm activity over warm water. Large-scale thermal lows over continents help drive monsoon circulations. 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. Thermal lows form due to localized heating caused by greater solar incidence over deserts and other land masses. A second is an area where wind divergence aloft occurs ahead of embedded shortwave troughs, which are of smaller wavelength.ĭiverging winds aloft, ahead of these troughs, cause atmospheric lift within the troposphere below as air flows upwards away from the surface, which lowers surface pressures as this upward motion partially counteracts the force of gravity packing the air close to the ground.The first is in the area 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).In meteorology, atmospheric divergence aloft occurs in two kinds of places: The formation process of a low-pressure area is known as cyclogenesis. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere (aloft). Winds circle anti-clockwise around lows in the northern hemisphere, and clockwise in the southern hemisphere, due to opposing Coriolis forces. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible rain or storms), while high-pressure areas are associated with lighter winds and clear skies. In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations.
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