when a front is moving in), or they can be small and local (e.g. The convergence of horizontal winds causes air to rise, whereas the divergence of horizontal winds causes downward motion of the air (subsidence). If there is sufficient moisture in the rising warm air, and the convergence of the air masses is energetic enough to lift the warm air high enough, clouds and precipitation … When the ascending air mass is stable or the same temperature as the surrounding air masses, the result of convection is nice puffy cumulus clouds. Colin Montheath/Hedgehog House/Minden Pictures/, Information about the device's operating system, Information about other identifiers assigned to the device, The IP address from which the device accesses a client's website or mobile application, Information about the user's activity on that device, including web pages and mobile apps visited or used, Information about the geographic location of the device when it accesses a website or mobile application. We also share information about your use of our site with our social media, advertising and analytics partners who may combine it with other information that you’ve provided to them or that they’ve collected from your use of their services. - Air masses warm and moist by the time they reach their destination - Produces heavy precipitation in winter in form of rain ... upper-level convergence of air must exceed low-level divergence of air (more air must be brought in above the anticyclone than is removed at the surface) Weird & Wacky, Copyright © 2020 HowStuffWorks, a division of InfoSpace Holdings, LLC, a System1 Company. Misty mountain scenes are a common sight since the sudden increase in elevation helps to generate cloud cover. These two air masses have been further divided into two types on the basis of the nature of the surface of the source regions (whether continen­tal or oceanic areas) e.g. The incoming wind from either side will trigger thermals in that area. Crossing valleys is made much easier when flying along such a convergence line. Convergence of Low-Level Air Masses. on sufficiently narrow islands like New Zealand, or the Canary Islands).  The location of the convergence line on a particular day depends on the strength of the valley breeze and the strength of the prevailing winds. They may also be noticeable by different (and often unusual) wind directions on the ground (e.g. The difference in cloud bases may be so great that it could be difficult to return from the lower side to the higher one. ITCZ (Intertropical Convergence Zone) is brought about by the convergence of the upper east and southeast exchange winds the zone surrounding Earth close to the Equator. This is often a phenomenon in Southern Tyrol when humid air from the Po valley gets pulled towards the Dolomites and forms much lower cloud bases in the South. This is marked by an area of low pressure. by spotting different wind directions on the surface of nearby lakes); by rows of misty veils, whirled-up dust above the ground in a valley, or sometimes even by visible differences in the clarity of two air masses.  Depending on the strength of the two valley breezes the meeting point may be either directly over the gap or to either side of it. Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. Trade winds in both hemispheres The Earth’s Coriolis force produces a westerly air stream along the Equator: in the northern hemisphere, the winds generally come from the north-east and, in the southern hemisphere, from the south-east. Since fronts are formed due to convergence of two air masses of contrasting temperatures and hence contrasting weather conditions are found from north to south or south to north. Convergence zones can occur at a very large scale (e.g. Convergence zones are areas where different air masses meet. If the air is entering an area of low pressure at the surface, winds curve inward and move up, known at convergence. On the other hand, Figure 2(a) shows that air masses are moving towards a line or a point; and Figure 2(b) shows that piling up of air is caused by air masses moving slower than those behind them. Convergence: When two air masses of the same temperature collide and neither is willing to go back down, the only way to go is up. Sometimes showers form less randomly in lines or bands when winds blow from different directions and collide. With a sea breeze the cooler air from the sea lifts the drier hotter land air and when the drier land air rises clouds and rain can occur.  Thermals can then easily be triggered in the convergence zone where good climb rates can be found. Not only are horizontal changes in wind occurring during convergence and divergence but vertical changes as well. In our discussion of sinking and rising air we showed how air flows in (lows) and out (highs) in all direction near the surface. Lifting of air and convergence of air at the ground surface (cycolnic condition), and (v) Advection. This air mass. A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. If a cT air mass lingers over a region for any period of time, a severe drought can occur. Valley Breeze Convergence: during thermal days, air flows up along the valleys towards the mountains to replace the air that is lifted by mountain thermals. Fronts & Air Masses Chapter overview: • Anticyclones or highs • Air Masses o Classification o Source regions o Air masses of North America • Fronts o Stationary fronts ... convergence occurs. This results in a convergence of temperature and dewpoint at a rate of 4.4°F. One of the most spectacular convergence zones in the world is the long N-S line to the East of the Rocky Mountains. Air Masses.  Mountain breeze convergence appears in the middle of valleys where these winds meet and the air therefore has to rise. Some clouds form when air at the surface of the Earth is forced to rise. A Glider Pilot Learns to Play Mother Nature. Katabatic winds descending from the mountains in the evening can cause convergence zones in the middle of valleys. The ideal source region has a uniform surface (all land or all water), a uniform temperature, and is an area in which air … c) An air … ... Air masses. when a front is moving in), or they can be small and local (e.g. Since the converging air has nowhere else to … The air masses separated by a front usually differ in temperature and humidity. Convergence zones are areas where different air masses meet. The resulting effect is a decrease in thickness.  This is particularly true if the strength of the prevailing northerly winds is sufficient that the convergence line is pushed further to the South. Apply the convergence rate to the reported temperature and dewpoint to determine the height of the cloud base. – a zone of convergence of air masses along the equatorial trough-nicknamed ‘doldrums’ for lack of wind and stranded ships-shifts with seasons-can sometimes move too greatly, change pressure patterns too greatly, creating monsoons in Asiatic wind patterns subtropical high-pressure belt – an area of persistent high atmospheric pressure centered at about 30° N and 30° S latitude Convergence of low-level air plays a major role in the formation of cold and warm fronts. Differences in terms of tem­perature, humidity, precipitation, cloudiness, and wind direction are experienced along different fronts e.g., warm and cold fronts. Lee Convergence is the result of wind flowing around a mountain and meeting itself on the leeward side.  This seems to be a key phenomenon in Boulder, where the easterly valley breeze moves up along the canyons and foothills of the front range where it meets the prevailing westerly winds flowing over the Continental Divide. The colder air mass is heavier than the warmer air mass, therefore the lighter, warmer air rises over the top of the heavier, colder air. Clouds that are formed by these thermals tend to come and go quickly. Their air is carried from Mexico and the southwestern U.S., and only impacts U.S. weather during the summertime. 1. Low-level convergence occurs when winds from two systems are moving on a collision course. This phenomenon is called horizontal divergence. A convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions. Mountain Breeze Convergence: in German often referred to as “Umkehrthermik”. Inspiration – Videos That Will Get You Hooked.  Where two valleys meet (e.g. ... Divergences and Convergence Aloft. Also, the warm air is in contact with the cold air along the fronts, and this also cools. This is the point where the two Hadley cells meet. Convergence zones can occur at a very large scale (e.g. Daily adiabatic winds often cause convergence zones along the spine of mountain ridges when winds from both sides of the ridge converges. Convergence of a Valley Breeze with Prevailing Winds:  Where a valley breeze meets a prevailing wind blowing in the opposite direction, a convergence line forms that is often marked by noticeably different cloud bases. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front. These air masses can differ from each other based on their temperature, their humidity content, their level of stability, and/or their wind direction and speed. Air masses are large bodies of air that take on the characteristics of the surrounding area, or source region. Exchange Winds: Easterly breezes that circle the Earth close to the Equator. Such a mass has distinct boundaries and may extend hundreds or thousands of kilometres horizontally and sometimes as high as the top of the troposphere (about 10–18 km [6–11 miles] above the Earth’s surface). Air Mass Convergence: A good example for air mass convergence is when a sea breeze meets another airmass, or when see breezes meet from different directions (e.g. This causes air to converge, or come together, at the center of the low near the ground. Write down your answers and beside each describe the weather conditions it will bring. 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