Cyclone

In meteorology, a cyclone is any significant system of winds that rotates counterclockwise to the north of the equator and clockwise to the south around a center of low air pressure. Except for the equatorial belt, cyclonic winds travel throughout almost all of the planet's surface. They are frequently accompanied by rain or snow. Anticyclones, which are wind systems that revolve around a high-pressure center, also occur in about the same regions. In contrast to cyclones, which spiral inward, anticyclones spiral outward, with the winds turning clockwise in the northern hemisphere and counterclockwise in the southern. These winds frequently do not produce precipitation and are typically not as intense as cyclonic winds. 

 

The middle and high latitude belts in both hemispheres are where cyclones are most common. Cyclones are dispersed quite uniformly throughout different longitudes in the Southern Hemisphere, since the oceans cover the majority of the land area. They typically originate in latitudes between 30° and 40° S and migrate primarily southeastward, maturing in latitudes about 60°. 

 

In the Northern Hemisphere, things are very different. There, continental landmasses reach all the way to the Arctic, and massive mountain ranges disrupt the midlatitude air currents, causing cyclone frequency to vary significantly (also anticyclones). The wind systems favor particular tracks. The main cyclone paths frequently travel to the east of mountain barriers and continental coastlines as they pass over the oceans. 

 

The extra tropical type of cyclones differ slightly from those that occur closer to the equator (i.e., at latitudes 10° to 25° north and south over the oceans). These wind systems, also referred to as tropical cyclones, have substantially smaller radii. Tropical cyclones normally have a diameter of only 100 to over 1,000 km, while extratropical cyclones can be approximately 1,000 to 4,000 km (620 to 2,500 miles) broad. They can also wreak a great deal of damage and have a tendency to be more violent than those that occur in the midlatitudes. 

 

Their wind speeds can exceed extra tropical cyclones' maximum of 30 meters per second (67 miles per hour), which is roughly 90 meters per second (200 miles per hour). Tropical storms with winds of at least 33 m/s (74 mph) averaged over one-minute intervals are referred to as hurricanes in the Atlantic and Caribbean while typhoons are used in the western Pacific and China Sea. Informally, the term "cyclone" is sometimes used to describe much smaller rotating events like tornadoes and dust devils, which may actually revolve anticyclonically.

 

Meteorology's term for small-scale, irregular air motions that are characterized by shifting winds is atmospheric turbulence. Because it stirs and mixes the air, turbulence is essential for the distribution of energy, water vapour, smoke, and other things both vertically and horizontally. Near the Earth's surface, atmospheric turbulence is different from that at higher altitudes. Under partly overcast and sunny sky, turbulence at low levels (within a few hundred meters of the surface) exhibits a noticeable diurnal variation, peaking around midday. 

 

This happens because as a result of the surface being heated by solar radiation, the air above it warms up and becomes more buoyant, and as a result, cooler, denser air descends to replace it. Low-level winds are very erratic due to the ensuing vertical air movement and flow disruptions around surface obstructions. When the air close to the ground becomes colder than the air above it during the night, a stable temperature inversion is established, and wind speed and gustiness both significantly decrease. 

 

Low-level air temperatures fluctuate between day and night much less and turbulence is practically constant when the sky is overcast. The frictional effects of surface topography on the wind are considerably diminished at altitudes of several thousand meters or more, and the small-scale turbulence typical of the lower atmosphere is absent. Although upper-level winds are typically very consistent, they can occasionally become too turbulent to have an impact on aviation. 

 

In meteorology and climatology, wind is the movement of air in relation to the Earth's surface. Climate and weather are significantly influenced and controlled by winds. Atmospheric pressure gradients, or changes in pressure along both the horizontal and vertical axes, create wind. As a result, the dispersion of winds and pressure are tightly connected. Winds typically circulate around cyclones and anticyclones, which are areas of relatively low and high pressure, respectively, near the Earth's surface. 

 

Around lows in the Northern Hemisphere they revolve in a counterclockwise direction, while around lows in the Southern Hemisphere in a clockwise direction. Similar to how wind systems rotate in the opposite direction from high centers. Instead of being closed, nearly circular systems nearer the Earth's surface, the pressure systems in the middle and upper troposphere are arranged in a series of high-pressure ridges and low-pressure troughs. They move in waves and interact to create an intricate pattern of ridges and troughs. 

 

The so-called standing waves, which feature three or four peaks and a comparable number of troughs in a broad area across middle latitudes of the Northern Hemisphere, are the largest wave patterns. The Southern Hemisphere's westerlies are far less severely impacted by standing disturbances. The small waves known as travelling waves have a wavelength of several hundred kilometers and are connected to these long standing waves. 

 

These travelling waves direct the genesis and motion of the near-surface cyclones and anticyclones to which they are connected. High latitudes typically have easterly winds close to the ground. The intertropical convergence zone (ICZ), also known as the thermal equator, migrates north and south with the seasonal position of the Sun. In low, tropical, and equatorial latitudes, the northeasterly trade winds travel toward the ICZ while the southeasterly trade winds move away from the ICZ. 

 

On each side of the ICZ, which delineates a constricted zone of relatively calm weather known as the doldrums, winds surge vertically and produce towering cumulonimbus clouds and torrential rain. After moving poleward towards the top of the troposphere, the winds then begin to descend once more in the subtropical belts of each hemisphere. From this point, trade winds once more blow in the direction of the Equator. The Hadley cells are these enormous cells with overturning air in both hemispheres at low latitudes. In the mid-latitudes, opposingly rotating wind systems known as Ferrel cells move upper tropospheric air toward the Hadley cells and surface air pole ward. The underlying latitudinal structure of pressure and air movement, and consequently, of climates, is caused by the three-dimensional pattern of winds over the Earth known as general circulation.

 

Local winds, which are connected with particular geographic regions and reflect the effect of physical features, operate on a smaller scale. The sea and land breezes, mountain and valley breezes, foehn winds (also known as chinook, or Santa Ana, winds), and katabatic winds are the most prevalent of these local wind systems. Local weather conditions and local winds both have a significant impact on the local climate. The daytime is typically the windiest time of the day because the Sun's warmth of the earth encourages the air to flip over while the descending currents preserve the angular momentum of high-altitude winds. The wind becomes less gusty and generally lighter at night.