weather and climate change in the weather in May - the hot high-pressure weather returns Following a rather cool days, it is now also in Central Europe really warm. The summer and the beginning of May had already given a short spell now comes with warm, moist air, lightning and thunder. How and why it happens, I want to tell about it a little ...
The weather machine
weather patterns on Earth is mainly driven by our sun, but her favor distributed very unequally. While the tropics, the equatorial region, then, with their high-energy solar radiation almost spoiled it behaves toward the poles rather neglected. The warming of the earth's surface is in fact the angle of incidence of sunlight-dependent. The flatter the incident radiation, the greater the surface on which they spread their energy, and the less is any piece of heated area, and vice versa. At the poles, the angle of the sun rays but is now again very flat, in the equatorial region, however, very steep. We are located in Germany, so about halfway in between. And then there's the change of day and night - the Earth rotates once every 24 hours on its axis and, above all yes even the seasons, Northern and Southern Hemisphere received during one revolution around the sun turns once more and sometimes less solar radiation, because this applies even more steeply to the northern hemisphere and flat flat on the southern hemisphere and the other times steeper in the northern hemisphere and to the southern hemisphere. The reason is that the rotational axis of the earth is not exactly perpendicular to the orbital plane around the sun but is tilted, ie by 23.5 °. In winter in the northern hemisphere, the north pole gets so from absolutely no sun (polar night) In the summer there seems indeed around the clock, the sun, but the angle of incidence of sunlight is as I said very flat, and so it is always still quite cold. In the area of the equator, however, the difference between summer and winter is low. Viewed over the whole year, the equatorial region is always heated well above the poles and in winter, this difference is larger than in summer. This temperature difference between equator and the poles carries over to the layers of atmosphere about it, because they get their heat as a stove by the different degrees of the sun heated the ground . The difference in temperature between tropical air from the warm equatorial region and polar cold air will be compensated, and that is what drives all that we as daily weather is always to experience again.
1: The formation of the seasons
Source: Wikipedia enlarged image by clicking !
weather patterns, which we'll look like in detail, plays mainly in the lowest layer of the Earth's atmosphere, the troposphere from that of below -where the heated ground -ever upwards colder is .. In extending the very dry stratosphere where the air is already very thin. It contains ozone, the shares of the dangerous ultraviolet radiation catches the sun warms us here. For this reason, the stratosphere is warmer than the upper troposphere (temperature inversion).
In the now following explanation of the weather we want to limit ourselves for the sake of clarity to the northern hemisphere. In the southern hemisphere which processes occur with opposite sign, but otherwise quite well off.
The tropical hot air and cold polar air may spread and meet in the middle latitudes slower on the so referred Polar Front aufeinander.Da the air pressure in the tropical hot air with increasing height decreases as the cold polar air is created in the height at the top troposphere , an air pressure differential (gradient) which is directed from the hot to cold air, that is from south to north (poleward ). The result is a gradient force, the one poleward directed winds aloft ( Jetstream ) causes, but which will in turn deflected by the Earth's rotation and thus becomes a West wind. It forms a west wind zone ( westerlies ) out that until down to earth interspersed. The temperature and hence pressure gradient is not anywhere on the polar front exactly the same size and in consequence, the wind speeds in each corresponding section of the jet streams . By such irregularities begins to meander Jetstream ( Rossby waves). The wave crests (high wedges) included hot tropical air, the wave valleys (troughs height) of cold polar air.
Figure 2: Jetstream with Rossby waves, dynamic high-and low pressure areas
Source: Lufthansa brochure enlarged image by clicking!
The amount of flow of the jet streams becomes alternately accelerated and then decelerated. On the back (west side ) of a wave trough of the jet streams (trough) is accelerated, the air because the air particles will learn not only the poleward gradient force, a centrifugal force directed in exactly the opposite direction. Thus, the upper air flow is slowed down and by the subsequent still with unabated air there is an air blockage (convergence). The air column in this convergence zone is gaining ground, so that increases the soil gas pressure. The air escapes around the outside of (divergence in soil) and forms a downward pressure vortex. In this way, the dynamic high-pressure area (anticyclone ), which rotate in the northern hemisphere and clockwise equatorward Comm. Since the air in such a high pressure system drops down and warms up, dissolve clouds, if present, very fast. On the front (east side) of a wave trough (trough), the velocity of the upper air flow to increase as the decelerating centrifugal force is eliminated. The speed comes with even braked subsequent air behind and there is no air (divergence). The air column in the divergence zone is losing mass, and falls of ground air pressure. The air flows in from all around (convergence on the ground), and there is an upward low-pressure vortices. In this way, the dynamic low-pressure areas (cyclones ) veer, which rotate in the northern hemisphere because of the Coriolis force counterclockwise and poleward .
Figure 3: Deflection of air particles moving through the Earth's rotation (Coriolis force ) The earth rotates on its axis (earth rotation) and the atmosphere of air particles rotate with it. The further north you get, the slower moving air particles in the direction of rotation, because the parallels are indeed getting smaller and thus the distance to be covered during a rotation of the earth getting shorter. When a moving air particles, for example, from the equator to the north, it gets so with a higher speed in the direction of rotation of the earth, as they have in the higher latitudes are air particles. Therefore it is urgent that in the direction of the Earth's rotation ahead to the east, is thus deflected to the right. An air particles moving from the north towards the equator, it gets a lower speed in the direction of the Earth's rotation with than to the lower latitudes, each already located air particles, and it is against this back. The particles of air is to the west, so also deflected to the right. An air particles moving at a medium latitude to the east in the direction of the Earth's rotation, so it is faster than the surrounding air particles, and it moves at a latitude equal to the higher speed is deflected to the right so to the south. An air particles on the other hand, moving to a middle latitude westward against the earth's rotation loses, compared to the ambient air particles of speed and looks for a corresponding end latitude. It is to the north, so also the right abgelenkt.In the figure, the blue arrows for the gradient force are (along a pressure gradient), which sets the air particles in motion. The red arrows represent the Coriolis force deflecting and the black arrows show the resulting motion of air particles. Source: Wikipedia
enlarged image by clicking !
The deflection by the Coriolis force incidentally also makes sure that the pressure balance between High and low pressure systems is not direct and straight path. The life of high and low pressure areas will be extended so great.
By proceeding from its low pressure center of rotation of warm air poleward collides with the cold air sector (warm front), in exchange for cold air equatorward collides with the hot air (cold front) in front. At the warm front, where the warm air glides slowly over the cooler air upward, forming layer clouds, and it often begins a long time to rain (steady rain). At higher altitudes, where it is colder, to form ice clouds (cirrus ). The cold front and the cold air behind it move much faster than the anticipatory warm air that rise because of their tendency has a less pronounced forward movement. The hot air is so permeated by and by the approaching cold air is not being given because it is easier to give a strong (unstable air stratification), and it forms a distinct cloudiness . In strong winds there is very heavy showers, often to thunderstorms with hail. The warm air sector is pushed together by little. is to unite warm and cold front, while a mixed Front ( occlusion ) disappeared completely until the warm air sector. Later the area of low pressure triggers altogether. The average life span of dynamic low-pressure areas is only about a week. To the cold fronts of older low-pressure areas may in turn be small wave disturbances and the formation of more dynamic cause low pressure areas (lows edge, daughter lows ).
Figure 4: Development and construction of a low pressure area low pressure area for Vilhelm Bjerknes (1862-1951), who developed the polar front theory, statements in the text. enlarged images by clicking !
For small wave disturbances of the Jetstreams at the Polar Front caused so dynamic high-and low-pressure vortex, like agitators for the mixing of hot and cold air and allow for a reduction of the temperature and pressure gradient between the equator and the Poland needs. The low-pressure systems are supported by the West drift to the east. In the areas under their migratory routes they provide changeable weather with clouds and frequent rain and overcast interim (between peaks) at relatively mild temperatures.
The Current weather conditions
We will now apply our newly acquired knowledge and turn our attention to the weather end of May. We use a recording of the European weather satellite Meteosat
orbiting the Earth in a geostationary orbit. The satellite is flying here on such a high track,
that he needs for a well
Earth orbit for a day, exactly the time it takes for the earth to rotate on its axis. Therefore, the satellite rotates exactly with the earth and always remains above the same place on the earth's surface.
5: Conditions on May 27, 2008 at 12:00 UTC Source: http://www.metoffice.gov.uk/ enlarged image by clicking ! falls on the image once a mighty low of Iceland in the eye. Hot and cold front and occluded
shares his
front system are clearly visible (see also Figure 4). Another deep-centered west of Biscay extends with its front system in the arch of the British Isles, the Benelux countries and France. The first runners have already reached the western Germany. lies over central and eastern Europe an extensive high. The sky is there virtually cloudless
. By the unimpeded sunlight it is hot and dry.
Further information is available about the weather, we show a Höhenkarte.Sie
many shades indicating, respectively, in the amount of air pressure of 500 hPa
decreased (elevation in meters
Deka!). Since warm air will expand toward more than cold air, the air pressure is also correspondingly more slowly with increasing altitude. The warmer the air then dropped
umdso greater the height of the air pressure of 500 hPa
is. This gives in a summary map display then a 500 hPa
area as a kind of "landscape" with "mountains" and "valleys". In the red, orange and yellow areas, there is the warm air, the temperature increases from yellow to red, in green, blue and purple areas, however, the cold air, from green to blue to violet decreasing temperature. The isobars
the soil gas pressure are shown as white lines closed.
isobars connect the places of the same air pressure to each other. Small distances between them show a large pressure gradient and vice versa. The air pressure values are registered in the
isobars. The numbers on the 500 hPa
area indicate the prevailing temperatures. A black line marks the course of the polar front where the warm air from the tropics and the polar cold air collide with each other
and where the
Polarfrontjetstream runs (see above).
6: elevation map for satellite image from May 27, 2008 at 12:00 UTC clock Source: http://www.wetterzentrale.de/ enlarged image by clicking ! When Consider the elevation map is striking that
is the Iceland low, as might be expected in the direct sphere of influence
of
Polarfrontjetstreams . The Bay of Biscay deep, however, is completely off, detached from
Polarfrontjetstream and
westerlies , eye to eye with the extended high over Central and Eastern Europe.
such thing can happen whenever the temperature gradient significantly decreases the polar front. The flow rate is
in
Jetstream then also fell sharply, so that
the
Rossby waves are getting stronger. The very strong jet stream meandering
will then slow to the level of flow often breaks down completely. The dynamic high-and low-pressure areas in the West
drift are thus as it were "frozen". The ups then block the lows
(
blocking action "), which then dissolve from the west wind zone ("
cut off ") to" bypass "the obstruction.
poleward formed a new
Polarfontjetstream and a new
westerlies without
Rossby waves, with correspondingly high velocity
from. As no temperature compensation is possible over the temperature differences between tropical warm air and cold polar air are larger again, until by instabilities of the
Jetstreams again form
Rossby waves, may arise which also new dynamic high-and low pressure areas. Since the detached from the westerlies
lows were originally on the cold air side of the polar front, it is for them to areas of cold air supplied from the warmer ambient air
the warm air side fully enclosed. Therefore, they are also called cold air drops. As a cold upper low
relatively hot air - an unstable air stratification so - "suck" the air up. This cools, and develop many
clouds (
Cumulus, cumulonimbus
). Heavy rain (heavy rain, snow), and often thunderstorms (hail) are the result.
The Bay of Biscay deep is therefore a cold air drops, which ensure that within its sphere of influence
for severe thunderstorms. Since the low turns counterclockwise it will warm tropical air over the Mediterranean - where she can absorb a lot of moisture - approach to central Europe. The warm, moist air but is held back by the alps. She had no option other than to the windward side of the Alps to climb, while the windward side so cool. The water vapor in the air condenses, and it comes to cloud formation and rainfall. This condensation releases heat, called latent heat. It corresponds to the energy that was needed to evaporate the water over the Mediterranean and is now released in the reverse process, of course, again. The latent heat of rising air is fresh impetus, as long as it is warmer than the ambient air, can continue the climb. Also, water vapor condenses, as long as there is still enough of it. The energy released during the heat of condensation clouds drifting all in turn the formation of clouds at. For example, a pronounced swelling clouds with heavy precipitation and severe storms often form. On the leeward side of the Alps, the leeward side of the shed rain falls to the now very dry air heats up again and again. At the same height differences and shall be warmer than it originally was before the rise, as they still contain the latent heat. North of the Alps is blowing so a warm and dry Südföhn.
We summarize again:
are raging thunderstorms in Western Europe, Central and Eastern Europe under the influence of high pressure. Germany is right in the middle. So thunderstorms in the west and mostly sunshine In the south east of significantly increasing temperatures.
Health problems in high-pressure weather Man is like all other mammals in the position his body temperature, except for small daily fluctuations, largely constant at about 37 ° C hold and this with changing environmental conditions - hot and cold weather - But even with their own different metabolic state. Especially in the vital internal organs and the brain inside the body, then, must be for the smooth functioning always a constant temperature, core temperature, maintained. In the outer layers of the body, the body shell is clearly cooler and the temperature fluctuations may be greater. To keep the core temperature constant, it is necessary that produced by metabolic processes inner-heat and the heat emitted to the environment are exactly the same. The inner-heat is used primarily with the blood stream, to a lesser extent, by simple heat conduction in the outer tissues of the body shell. On the body surface, heat is then released through the skin by conduction, convection (air circulation) and evaporation processes (sweating) to the environment. The Daduchus cooled blood flows back inside the body.
Heat production and heat output are controlled by a control center in the hypothalamus of the brain via the autonomic nervous system.
The body's temperature regulation mechanism that has several temperature sensors in the skin and tissue is, at several points: The blood vessels in the skin dilate when it is warm (vasodilation), so that the skin blood flow increases. The blood pressure falls, heart rate and cardiac work are increasing. The increased blood flow then more heat escapes to the outside. The sweat production is increased and thus the evaporation on the skin. The additional evaporation has a strong cooling. At high humidity, the sweat evaporation is impeded significantly. Adequate cooling of the body is often not possible anymore, and there are likely to overheat. If it is cold, narrow the blood vessels of the skin (vasoconstriction) and thus the body is lost less heat. If there is still a greater loss of body heat, is such a tremor, with internal heat is produced. By the release of stress hormones increase blood pressure, cardiac workload and heart rate. Since the outer blood vessels are too close together, the vital organs and the brain to increase blood circulation.
7: The thermo-regulation, the control center is located in the hypothalamus of the brain is, in the blood vessels of the skin, sweat glands and the muscles. Source: http://fig.cox.miami.edu/ ~ cmallery/150/physiol/physiology.htm enlarged image by clicking!
high-pressure situations with high Temoeraturen burden so dramatically the circulation, especially if there is still a high humidity. This is particularly true for elderly and sick people. You should definitely avoid unnecessary efforts in such weather conditions. During the summer, a record in 2003, the hottest in Europe for 500 years (!) Died there, 70,000 people more than usual during this period 1518.473614 (
http://www.spiegel.de/wissenschaft/mensch/0, 00.html).
There are legitimately fear that such a hot summer as a result of climate change in the course of global warming, will soon no longer be the exception but the rule!
greenhouse effect, climate change and high-pressure weather The earth absorbs the sun's radiation, converts it into heat and heats turn the atmosphere from below. Part of the heat from the earth is radiated back into space (infrared radiation), but the greenhouse gas retention (carbon dioxide, water vapor, methane, nitrous oxide), but again a bit. The greenhouse gas molecules absorb namely certain selected wavelengths of infrared radiation and give most of it by shocks to neighboring molecules. The atmosphere is heated by a little. However, a small portion reaches as infrared counter-radiation - the same wavelength absorbed in the first was - back to earth to get this back again some heat and cools more slowly. The rest of the recorded Heat emitted by the greenhouse gas into space. The delay in cooling the earth warmed by the sun's rays to higher temperatures than if there were no greenhouse gases. The Earth's surface then radiates the temperature rise correspondingly more infrared radiation - with the many wavelengths that can not absorb the greenhouse gases (infrared window) - into space, so that a new radiation equilibrium is at a higher temperature level. The heated by the greenhouse effect the earth is its extra heat but also from the bottom of the lower atmosphere on the troposphere. The effects of greenhouse gases add up, but can also reinforce each other disproportionately. If for example the concentration of carbon dioxide (CO2) in the air, it is only a little warmer. The warmer air can hold more moisture. Water (H2O) is now but a much stronger greenhouse gas than carbon dioxide. This reinforced the H2O in the atmosphere of the relatively small greenhouse effect of CO2 (water vapor gain).
not reach all the earth, but incoming solar radiation to the earth's surface and heat it, because part of the radiation is reflected from the bright clouds in outer space (reflected), and the earth's surface itself reflects a function by their nature a certain portion of solar radiation (albedo). Is the Earth's surface such as ice or even snow covered, or are there many clouds, so the Earth has a high albedo, and solar radiation is reflected to a large extent in space. A high albedo acts so cool. Another rather small portion of solar radiation is absorbed by the atmosphere directly (absorbed). Clouds cooling effect not only by their high albedo, but also are of the conflicting global warming. They keep the heat even better than all the greenhouse gases because they absorb infrared radiation infrared wave in all areas! Of these, one part passes as infrared counter-radiation back to the ground, the other is radiated directly into space. This radiation into space is smaller, the greater the vertical extent of clouds is because at higher altitudes, the cloud tops much colder than the bottom. The infrared radiation of the cloud top into space is significantly less than the infrared counter-radiation at the cloud base. Depending on cloud type outweighs their cooling effect and its greenhouse effect: ice clouds (cirrus) at high altitude allow sunlight through the most part, but absorb very well the infrared radiation coming from the ground and have therefore warming. Clouds consisting of small water droplets (Cumulus, Stratus), are very bright and therefore reflect the most sunlight. Although these clouds absorb infrared radiation from the ground very well, in this case outweighs the cooling effect.
primarily through the use of fossil fuels, the concentration of the greenhouse gas CO2 has increased significantly in the atmosphere. This was accompanied by a significant rise in average global temperature (global warming). In the northern hemisphere it is a disproportionate warming of the polar region (Arctic) to watch, because if it melts the Arctic sea ice is much darker ocean below the water surface to light. Solar radiation is a much lesser extent reflects, as before, so that the heating increased, because the dark surface absorbs solar radiation much better than a bright icy surface, heats up more, and then accordingly, the air layers above. It is a self-reinforcing positive feedback - the more ice melts, the greater the warming, which melts more ice, etc. - is that of a point to be unstoppable.
Due to global warming, for example, in the northern hemisphere high-pressure weather conditions to expect more and more. This is connected with the changing Polarfrontjetstreams in the Pole, which West- and Central Europe are increasingly coming under pressure influence. Then it is hot and dry. Reason for the shift is an "encroachment" of the tropical warm air and a "retreat" of the cold air in the short polar region. In the course of recent years disproportionate warming in the Arctic (see above) also reduces the temperature and hence pressure gradient at the polar front. The jet stream will result on average slower and more meandering, so that blocking anticyclones are favored. On the other hand, are formed but also more and more cold air drops, so heavy rainfall and severe thunderstorms are likely.
In winter, the Impact of a more meandering Polarfrontjetstreams something different: like a fast, little meandering jet stream includes the polar cold air like a wall one. Meanders of the jet stream due to a lower temperature and pressure gradient at the polar front, but more so the cold polar air from him no more right "trapped". Is because it accumulated massive cold air outbreaks to the south (cold air troughs and cold air drops), which places it right cold, and it can also lead to greater snowfall. The sudden onset of winter first pass where the cold air is moving forward at best, so relatively rapidly cooling continental land masses such as Central Asia.
8: Links: Quiet undulations of the jet stream (positive phase) favor mild, rainy summer by a strong westerly winds of the low-pressure areas. In winter, the cold polar air trapped well and it is also quite mild. Right: If the jet stream meanders more, blocking anticyclones are more likely, and the summers are hot and dry. In winter, it always comes back to cold air outbreaks to the south (negative phase. Source: [ http://www.washington.edu/ ] enlarged images by clicking! Jens Christian Heuer
