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Polar Front
In meteorology, the polar front is the weather front boundary between the polar cell and the Ferrel cell around the 60° latitude, near the polar regions, in both hemisphere. At this boundary a sharp gradient in temperature occurs between these two air masses, each at very different temperatures. The polar front arises as a result of cold polar air meeting warm tropical air. It is a stationary front as the air masses are not moving against each other and stays stable. Off the coast of eastern North America, especially in winter, there is a sharp temperature gradient between the snow-covered land and the warm offshore currents. The polar front theory says that mid-latitude extratropical cyclones form on boundaries between warm and cold air. In winter, the polar front shifts towards the Equator, whereas high pressure systems dominate more in the summer. See also * Polar vortex * Horse latitudes The horse latitudes are the latitudes about 30 degrees north and sou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stationary Front
A stationary front (or quasi-stationary front) is a weather front or transition zone between two air masses when both air mass is advancing into the other at speeds exceeding 5 knots (about 6 miles per hour or about 9 kilometers per hour) at the ground surface. On weather maps, it's illustrated as a solid line of alternating blue spikes pointing to the warmer air mass and red domes facing the colder air mass. Development A stationary front may form when a cold or warm front slows down or grows over time from underlying surface temperature differences, like a coastal front. Winds on the cold air and warm air sides often flow nearly parallel to the stationary front, often in opposite directions along either side of the stationary front. A stationary front usually remains in the same area for hours to days and may undulate as atmospheric waves move eastward along the front. Stationary fronts may also change into a cold or warm front and may form one or more extratropical or mid-latit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intertropical Convergence Zone
The Intertropical Convergence Zone (ITCZ ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal equator though its specific position varies seasonally. When it lies near the geographic Equator, it is called the near-equatorial trough. Where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage that is more common in Australia and parts of Asia. Meteorology The ITCZ was originally identified from the 1920s to the 1940s as the ''Intertropical Front'' (''ITF''), but after the recognition in the 1940s and the 1950s of the significance of wind field convergence in tropical weather production, the term ''Intertropical Convergence Zone'' (''ITCZ'') was then applied. The ITCZ appears as a band of clouds, usually thunderstorms, that encircle the globe near the Equator. In the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horse Latitudes
The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as subtropical ridges, or highs. It is a high-pressure area at the divergence of trade winds and the westerlies. Origin of the term A likely and documented explanation is that the term is derived from the "dead horse" ritual of seamen (see Beating a dead horse). In this practice, the seaman paraded a straw-stuffed effigy of a horse around the deck before throwing it overboard. Seamen were paid partly in advance before a long voyage, and they frequently spent their pay all at once, resulting in a period of time without income. If they got advances from the ship's paymaster, they would incur debt. This period was called the "dead horse" time, and it usually lasted a month or two. The seaman's ceremony was to celebrate having worked off the "dead horse" debt. As west-bound shipping from Europ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polar Vortex
A circumpolar vortex, or simply polar vortex, is a large region of cold, rotating air that encircles both of Earth's polar regions. Polar vortices also exist on other rotating, low-obliquity planetary bodies. The term polar vortex can be used to describe two distinct phenomena; the stratospheric polar vortex, and the tropospheric polar vortex. The stratospheric and tropospheric polar vortices both rotate in the direction of the Earth's spin, but they are distinct phenomena that have different sizes, structures, seasonal cycles, and impacts on weather. The stratospheric polar vortex is an area of high-speed, cyclonically rotating winds around 15 km to 50 km high, poleward of 50°, and is strongest in winter. It forms in Autumn when Arctic or Antarctic temperatures cool rapidly as the polar night begins. The increased temperature difference between the pole and the tropics causes strong winds and the Coriolis effect causes the vortex to spin up. The stratospheric polar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Summer
Summer is the hottest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, the earliest sunrise and latest sunset occurs, daylight hours are longest and dark hours are shortest, with day length decreasing as the season progresses after the solstice. The date of the beginning of summer varies according to climate, tradition, and culture. When it is summer in the Northern Hemisphere, it is winter in the Southern Hemisphere, and vice versa. Timing From an astronomical view, the equinoxes and solstices would be the middle of the respective seasons, but sometimes astronomical summer is defined as starting at the solstice, the time of maximal insolation, often identified with the 21st day of June or December. By solar reckoning, summer instead starts on May Day and the summer solstice is Midsummer. A variable seasonal lag means that the meteorological centre of the season, which is based on average temperature pattern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High Pressure Systems
A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interplays between the relatively larger-scale dynamics of an entire planet's atmospheric circulation. The strongest high-pressure areas result from masses of cold air which spread out from polar regions into cool neighboring regions. These highs weaken once they extend out over warmer bodies of water. Weaker—but more frequently occurring—are high-pressure areas caused by atmospheric subsidence: Air becomes cool enough to precipitate out its water vapor, and large masses of cooler, drier air descend from above. Within high-pressure areas, winds flow from where the pressure is highest, at the center of the area, toward the periphery where the pressure is lower. However, if the planet is rotating, the straight direction of the air flow f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can also be used for any other celestial body that is roughly spherical. In spatial (3D) geometry, as applied in astronomy, the equator of a rotating spheroid (such as a planet) is the parallel (circle of latitude) at which latitude is defined to be 0°. It is an imaginary line on the spheroid, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid with the plane perpendicular to its axis of rotation and midway between its geographical poles. On and near the equator (on Earth), noontime sunlight appears almost directly overhead (no more than about 23° from the zenith) every day, year-round. Consequently, the equator has a rather stable daytime temperature throug ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-latitude Cyclone
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 severe 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. Terminology The term " cyclone" applies to numerous types of low pressure areas, one of which is the extratropical cyclone. The descriptor ''extratropical'' signifies that this type of cyclone generally occurs outside the tropics and in the middle latitudes of Earth between 30° and 60° latitude. They are term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Winter
Winter is the coldest season of the year in polar and temperate climates. It occurs after autumn and before spring. The tilt of Earth's axis causes seasons; winter occurs when a hemisphere is oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. In many regions, winter brings snow and freezing temperatures. The moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value; that is, the Sun is at its farthest below the horizon as measured from the pole. The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice. The earliest sunset and latest sunrise dates outside the polar regions differ from the date of the winte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Caribbean Sea, and to the west and south by the Pacific Ocean. Because it is on the North American Plate, North American Tectonic Plate, Greenland is included as a part of North America geographically. North America covers an area of about , about 16.5% of Earth's land area and about 4.8% of its total surface. North America is the third-largest continent by area, following Asia and Africa, and the list of continents and continental subregions by population, fourth by population after Asia, Africa, and Europe. In 2013, its population was estimated at nearly 579 million people in List of sovereign states and dependent territories in North America, 23 independent states, or about 7.5% of the world's population. In Americas (terminology)#Human ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tropics
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to as the tropical zone and the torrid zone (see geographical zone). In terms of climate, the tropics receive sunlight that is more direct than the rest of Earth and are generally hotter and wetter as they aren't affected as much by the solar seasons. The word "tropical" sometimes refers to this sort of climate in the zone rather than to the geographical zone itself. The tropical zone includes deserts and snow-capped mountains, which are not tropical in the climatic sense. The tropics are distinguished from the other climatic and biomatic regions of Earth, which are the middle latitudes and the polar regions on either side of the equatorial zone. The tropics constitute 40% of Earth's surface area and contain 36% of Earth's landmass. , the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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