WEATHER AND CLIMATE: WINDS, AIR MASSES, FRONTS AND PRECIPITATION | Facts and Details
Air masses are classified into groups depending on their basic This air mass originates over North Africa and the Sahara (a warm source region). across the British Isles, in a tropical maritime air mass, is south-westerly. 1a, 2a, 3a and 4a we can deduct that the air mass which interest the Congo the Central African territory, the meeting place of the north and south trade winds. Six basic types of air masses affect the weather of the British Isles. They can bring anything from tropical warm and humid days to arctic cold slightly from the continental polar (cP) air masses that develop over Siberia and northern Canada. However, approaching from the south and south-east in summer it can bring.
This usually occurs km south of the actual position of the ITCZ. The weather associated with the ITCZ is towering cumulonimbus clouds, heavy precipitation and high intensity rainfall mm per hour.
It moves north in June and south in January because of the tilt of the earth. It follows then that the ITCZ also moves north in summer and south in winter. In the winter the dry season, the dominant air mass is Tropical Continental with the dry Harmahatten wind blowing across nearly all of West Africa.
Only the coastal south remains under the influence of the mT air. This brings with it the convectional rainfall of the ITCZ. Following on behind is the mT air mass which is carrying large amounts of potential precipitation.
Lagos Jos Timbuktu 12 Rainfall in West Africa Rainfall varies dramatically over the region and can be described using — incidence, intensity and irregularity. Incidence is the variability within the year.
Similar to a person trying to walk straight across a spinning Merry-Go-Round, winds get deflected from a straight-line path as they blow across the rotating Earth.
In the Northern Hemisphere air veers to the right and in the Southern Hemisphere to the left. This motion can result in large circulating weather systems, as air blows away from or into a high or low pressure area.
Hurricanes and nor'easters are examples of these cyclonic systems. Air Masses North American airmassesAn air mass is a large body of air with generally uniform temperature and humidity. The area from which an air mass originates is called a "source region. The United States is not a favorable source region because of the relatively frequent passage of weather disturbances that disrupt any opportunity for an air mass to stagnate and take on the properties of the underlying region. The longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below.
The four principal air mass classifications that influence the continental United States according to their source region are: As these air masses move around the Earth they can begin to acquire additional attributes. For example, in winter an arctic air mass very cold and dry air can move over the ocean, picking up some warmth and moisture from the warmer ocean and becoming a maritime polar air mass mP - one that is still fairly cold but contains moisture.
If that same polar air mass moves south from Canada into the southern U. This is called a continental polar air mass cP. The Gulf Coast states and the eastern third of the country commonly experience the tropical air mass in the summer. Continental tropical cT air is dry air pumped north, off of the Mexican Plateau. If it becomes stagnant over the Midwest, a drought may result. Maritime tropical mT air is air from the tropics which has moved north over cooler water. Air masses can control the weather for a relatively long time period: Most weather occurs along the periphery of these air masses at boundaries called fronts.
Fronts Fronts are classified as to which type of air mass cold or warm is replacing the other.
For example, a cold front demarcates the leading edge of a cold air mass displacing a warmer air mass. A warm front is the leading edge of a warmer air mass replacing a colder air mass. If the front is essentially not moving i.
Fronts don't just exist at the surface of the Earth, they have a vertical structure or slope as well. Warm fronts typically have a gentle slope so the air rising along the frontal surface is gradual.
This usually favors the development of widespread layered or stratiform cloudiness and precipitation along and to the north of the front. The slope of cold fronts are more steep and air is forced upward more abruptly. This usually leads to a narrow band of showers and thunderstorms along or just ahead of the front, especially if the rising air is unstable.
Cold fronts typically move faster than warm fronts, so in time they "catch up" to warm fronts.
Atmospheric Dynamic and Raining Mechanisms in the Congo Basin
As the two fronts merge, an occluded front forms. In the occluded front, the cold air undercuts the cooler air mass associated with the warm front, further lifting the already rising warm air. Fronts are usually detectable at the surface in a number of ways. Winds usually "converge" or come together at the fronts.
The cause and impact of the Intertropical Convergence Zone
Also, temperature differences can be quite noticeable from one side of the front to another. Finally, the pressure on either side of a front can vary significantly. Here is an example of a location that experiences typical warm frontal passage followed by a cold frontal passage: Clouds lower and thicken as the warm front approaches with several hours of light to moderate rain. Temperatures are in the 50s with winds from the east.
WEATHER AND CLIMATE: WINDS, AIR MASSES, FRONTS AND PRECIPITATION
As the warm front passes, the rain ends, skies become partly cloudy and temperatures warm into the mid 70s.
Winds become gusty from the south. A few hours later, a line of thunderstorms sweeps across the area just ahead of the cold front. After the rain ends and the front passes, winds shift to the northwest and temperatures fall into the 40s and skies clear. Heat In bad heat waves many of those who are killed are elderly. A summer heat wave sets in many areas of Japan after the June rainy season is over. In many places it is very hot with little relief many days in a row.
Areas near mountains sometimes experience high temperatures associated with the foehn wind effect. Heat generated in Tokyo is blown against the mountains in Saitama. Unusually high summer temperatures have been attributed to global warming, rising air currents and very strong high pressure over the Pacific Ocean.
In high temperatures were blamed on rising air currents created by the La Nina phenomena in the Pacific and rising air currents in India, creating a funneling effect that strengthened the rising air currents over Japan. When extremely hot days and tropical nights continue for extended periods the asphalt of the roads and walls of buildings do not cool down sufficiently at night, resulting in high room temperatures in office buildings from early in the morning, This boosts demand for air conditioning and electricity.
During heat waves in Japan the sale of air conditioners, beer soft drinks and watermelons increases. Japanese, Chinese and Koreans crave watermelons when the weather is hot and give them as summer present at Bon events. Demand was so strong for watermelons in the heat wave of that shortages were reported and prices were significantly higher than what they were in and In some cities, temperatures in some cities have increased 5. In other cities, the seasons have occurred as many as 20 days earlier than they have in the suburbs.
In the summer the increases have been greatest between midnight and 5: In the winter, it means no snow in places that once had snow. In the autumn, leaves that used to change color in November now change in December. In the spring, flowers bloom when there uses to be snow. Heat is emitted from air conditioners and vehicles.
Weather Facts: Air masses and their sources | acryingshame.info
The highest temperature readings in cities usually occur along streets and are lowest in parks, gardens and rivers. Large cities act like radiators. During the day asphalt roads, car exhaust, roofs, car bodies and concrete building absorb heat. At night they release it, making the nights much warmer than they otherwise would be. Cities near large bodies of water draw in warm moist air in the afternoon as the heat trapped by the city starts to be released and warm air rises.
The moist air and the warm city air collide and push other air higher. As it rises it cools and creates clouds and rain. Prevailing winds blow the clouds so that down wind areas of large cities get more rain than areas upwind. The Japanese are attempted to battle heat island effect by replacing dirt fields in school yards with grass ones and using water-retentive blocks made from crushed, recycled asphalt and concrete as paving material.
The water-retentive blocks are just as strong as ordinary paving blocks but reduce heat and produce a cooling effect when water is evaporated from them. Because the blocks are made from recycled material they are also environmentally friendly. Tokyoites battle the heat island effect by splashing water all over the place on pavement and concrete.
Around Tokyo station trees were planted on rooftops, water-retentive pavement has been installed and a building was knocked down to create a wind channel to dissipate some of the heat that builds up there. New technology, water systems and grass allow gardens to built without damaging existing roofs. City planners have discussed building pipelines under the cities to bring in cool water from local bays.
Air conditioner sales have boomed in recent years. Precipitation In order for precipitation to form, particularly over a large area, several ingredients are necessary. First there must be a source of moisture. The primary moisture sources in the U. Winds around high and low pressure systems a subject of another lesson transport this moisture inland.
Once the moisture is in place, clouds still need to form. The most effective way to do this is by lifting the air. This can be accomplished by forcing the air up and over mountains or, more commonly, by forcing air to rise near fronts and low pressure areas. So there must be a process es for the cloud water, or ice, to grow large enough to fall as precipitation. One process is called the collision and coalescence or warm rain process. In this process, collisions occur between cloud droplets of varying size, with their different fall speeds, sticking together or coalescing, forming larger drops.
Finally the drops become too large to be suspended in the air and they fall to the ground as rain. The other process is the ice crystal process. This occurs in colder clouds when both ice crystals and water droplets are present. In this situation it is "easier" for water vapor to deposit directly onto the ice crystals so the ice crystals grow at the expense of the water droplets. The crystals eventually become heavy enough to fall.
If it is cold near the surface it may snow, otherwise the snowflakes may melt to rain. The vertical distribution of temperature will often determine the type of precipitation rain vs. More often than not, the temperature does not decrease with height but increases, many times by several degrees, before decreasing.
This increase, then decrease is called an inversion. In winter, an inversion can be critical in determining the type or types of weather. As snow falls into the layer of air where the temperature is above freezing, the snow flakes partially melt. As the precipitation reenters the air that is below freezing, the precipitation will re-freeze into ice pellets that bounce off the ground, commonly called sleet. The most likely place for freezing rain and sleet is to the north of warm fronts.
The cause of the wintertime mess is a layer of air above freezing aloft. Freezing rain will occur if the warm layer in the atmosphere is deep with only a shallow layer of below freezing air at the surface. The rain falls back into the air that is below freezing but since the depth is shallow, the rain does not have time to freeze into sleet.
Upon hitting the ground or objects such as bridges and vehicles, the rain freezes on contact. Some of the most disastrous winter weather storms are due primarily to freezing rain.
Hail Hail is a form of precipitation that occurs when updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere where they freeze into ice. How fast does hail fall? We really only have estimates about the speed hail falls. However, the hailstone is not likely to reach terminal velocity due to friction, collisions with other hailstones or raindrops, wind, the viscosity of the wind, and melting.
Also, the formula to calculate terminal velocity is based on the assumption that you are dealing with a perfect sphere. Hail is generally not a perfect sphere! How does hail form? There are two ideas about hail formation. In the past, the prevailing thought was that hailstones grow by colliding with supercooled water drops. Supercooled water will freeze on contact with ice crystals, frozen rain drops, dust or some other nuclei.
Thunderstorms that have a strong updraft keep lifting the hailstones up to the top of the cloud where they encounter more supercooled water and continue to grow. The hail falls when the thunderstorm's updraft can no longer support the weight of the ice or the updraft weakens. The stronger the updraft the larger the hailstone can grow. Recent studies suggest that supercooled water may accumulate on frozen particles near the back-side of the storm as they are pushed forward across and above the updraft by the prevailing winds near the top of the storm.
Eventually, the hailstones encounter downdraft air and fall to the ground. Hailstones grow two ways: In wet growth, a tiny piece of ice is in an area where the air temperature is below freezing, but not super cold.
When the tiny piece of ice collides with a supercooled drop, the water does not freeze on the ice immediately. Instead, liquid water spreads across tumbling hailstones and slowly freezes.
The former becomes more stable, and the latter more unstable. Some older works use the term of an 'returning air mass'. This usually refers to maritime polar air that has been altered moving across the relatively mild Atlantic and is returning polewards eventually. The air masses prevalent for the British Isles are: Extremely cold temperatures and very little moisture.
Originating over the Arctic ocean in winter, when high pressure dominates and differs only slightly from the continental polar cP air masses that develop over Siberia and northern Canada. From the same source region, but less dry and less cold - in a way less extreme. Cold and dry, originating from high latitudes, typically as air flowing out of the polar highs. This air mass often brings the rattleing cold, dry and clear weather on a perfect winter day and also dry and warm weather on a pleasant day in summer.