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Meteorology&climatology
- 4. Phenomena Clouds Hurricane Tornado Storm Dust storm Lightning and Thunderbolt Rain Snow
- 21. Conclusions (1/2) Annual rainfall Population density GDP distribution
- 22. Conclusions (2/2) Katrina hurricane (2005) New Orleans after the Katrina
Notes de l'éditeur
- As you can see, my presentation is about Meteorology and Climatology, and these are the contents... I chose this theme because I find this field very interesting, spectacular and useful. -----
- Catalonia 08/09.03.10 -----
- The word "meteorology" comes from Greek μετέωρος, metéōros, that means “high in the sky“ or “suspended in the air”; and λογία, -log gos that means “science”. The science of the “suspended air ”. The, me teorology is a interdisciplinary scientific study of the atmosphere that explains the weather processes and forecasting. Weather is a set of all the phenomena occurring in a given atmosphere at a given time. We can talk about the weather at Hospitalet this morning. On the other side c limatology is from Greek κλίμα, klima, "region, zone"; and -λογία, -log os, is the study of climate, scientifically defined as weather conditions averaged over a period of time (of about 30 or 40 years) , and it is a branch of the atmospheric and geographic sciences too . Basic knowledge of climate can be used to weather forecasting. f.e. If you want to go on holidays to the other side of the world, you must consult the climate information to prepare your suitcases. And the average of the weather conditions is the climate. f.e. If you have to do an excursion to the countryside or the mountain, tomorrow morning you must consult the meteorological information. It shows that there is a strong relationship between climatology and meteorology. -----
- A meteorological phenomenon is a weather even t which can be explained by the principles of meteorology . Examples of the most espectaculars and dangerous meteorological phenomena for me are: Clouds: is a visible mass of droplets, in other words, little drops of water or frozen crystals suspended in the atmosphere . Hurricane: is a tropical cyclone, occurring in the North Atlantic Ocean or the Northeast Pacific Ocean . Tornado: is a violent, dangerous, rotating column of air which is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. S torm is any disturbed state of atmosphere . Lightning is an atmospheric discharge of electricity accompanied by thunder, which typically occurs during thunderstorms . D ust storm : is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front blows loose sand and dust from a dry surface Rain: is a liquid precipitation. -----
- According to the CMS (Catalonian Meteorological Service), Catalonia has 2 types of climate: - Oceanic (only in the Aran Valley area). - Mediterranean (rest of the territory). We also have another division in the Mediterranean climate. The littoral (near to the sea) , mountainous (the Pyrinees) and continental (the inner zones) . “ Hospitalet de Llobregat” is here (at the Barcelonès) and ha s a littoral Mediterranean one, because the city is near to the sea. Acording to the Catalonia’s Climate Atlas, t he annual average data for this town are the following: 17ºC of temperature. 452,1 mm of rainfall. 85 days of rain every year. -----
- To understand Catalonia’s climate first we have to situate it on the map. It is between 2 continents: with different characteristics (Europe and Africa). Africa is hotter than Europe. This represents that we can suffer heta and cold waves. Catalonia is between 2 seas: with different characteristics (Mediterranean and Cantabric) As you know, Cantabric is colder than Mediterranean. Catalonia has in front the Mediterranean sea and it’s not far from the Cantabric sea. Atmospheric dinamics: this is because of the global wind circulation, the storms enter across que cold Cantabric sea and are reactivated at the hot Mediterranean sea. Geographic factors: Catalonia has a great variety of orografy (Pirenees in front of Lleida plain) and latitude (from Cadaques to Ebre’s Delta). This represents the variety of divisions in the mediterranean climate. Another feature tis that the temperatures in winter are very gentle and in summer are very hot (exceptionally this winter was extremely cold and most of the latest summers have benn expecially hot) . The seasons when rainfall is more important are Spring and Autumn (exceptionally, this winter was very rainy). The average Temperatures are between: 4-5ºC (in the Aran Valley) and 17-18ºC (in southwest ). The annual a verage rainfall are between: 400 mm (in Lleida) and 1.200 mm (in Aran Valley). The Thornwaithe index classified Catalonia in 8 different areas according to the rain, the evaporation and the draining: from arid (brown, mainly the sudweat) to wet (blue, basicaly the north). -----
- Atmosphere is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. It comes from Greek ἀτμός - atmos "vapor" and σφαῖρα - sphaira "sphere“. The Earth without atmosphere would be about –15ºC. We can say that the atmosphere is the Eath’s blanket. The Earth's atmosphere contains several different layers that can be defined according to air temperature... ... the temperature decreases at the troposphere and mesosphere, and increases at stratosphere and thermosphere. As you can see, the average temperature in the surface (ground) is 18ºC and in the tropopause is –50ºC. The tropopause is the thin area than separate the troposphere and the stratosphere. The decreasing rate in the troposphere is 6ºC/km (every km up represents 6ºC less). The troposphere begins at the surface and extends to between 7 km at poles and 17 km at intertropical areas (this is because hot air takes up more space than cold air). This other line shows the pressure variation. As you can see, the pressure decreases very fall because about 80% of the total mass of the atmosphere is contained in troposphere. It is also the layer where the majority of our weather phenomena occurs. As we can see in the graphic, at stratosphere we can find the called ozone layer, that protects us from ultraviolet beams. These reactions cause the temperature increases. The maximum ozone concentration is between 20 and 25 km. -----
- The meteorological variables indicate the weather in a given place and a given moment. The main weather indexs are these... -----
- To mesure the meteorological variables we need a weather station . It is a facility with instruments and equipment for observing the atmospheric conditions to provide information for weather forecasts . Here we can see the different equipments to measure the meteorological variables. We can measure the weather indexs from a manual observation or with an automatic system. Manual observations are taken at least once daily, while automated observations are taken at least once an hour. The measurements taken include temperature, barometric pressure, humidity, wind speed, wind direction, irradiation, evaporation and precipitation amounts. Wind , rain and irradiation measurements are taken as free of other obstructions as possible, while the rest of measurements are kept free from direct solar radiation inside a shelter box called Stevenson screen . Except for those instruments requiring direct exposure to the elements ( wind measure and rain gauge), the instruments should be sheltered in a vented box, usually a Stevenson screen, to keep direct sunlight off the thermometer and wind off the humidity measure . - A Stevenson screen or instrument shelter is an wood enclosure to shield meteorological instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them. It must be located over fresh ground, like grass. It forms part of a standard weather station. - An automatic weather station (AWS) is an automated version of the traditional weather station, either to save human labour or to enable measurements from remote areas. An AWS will typically consist of a weather-proof enclosure containing the data logger, rechargeable battery and the meteorological sensors . Here we have the data logger and the sensors of temperature, humidity, pressure, wind, irradiation and rain. -----
- Everybody knows that the temperature is one of the most helpful index. The meteorological information always begins or ends with this data. We can see the different temperature units, and the year of their definition. The symbol is the first letter of the scientist’s name who develop the scale (f.e. farenheit degrees are abreviated with a capital F letter). This unit was introduced by Gabriel Farenheit in 1714 (in eighteen century). The celsius degrees were introduced by the swedish astronomer Anders Celsius in 1740. In most of the world (except for United States , Belize, Myanmar, Liberia), the c elsius scale is used for most temperature measuring purposes. In the United States the most useful is the f ahrenheit scale . Temperature is measured with thermometers that may be calibrated to the variety of temperature scales with the freezing (melting) point of ice, and the boling point of water . f.e. farenheit scale is calibrated between 32ºF and 212ºF, and celsius scale between 0 and 100ºC. The most useful m eteorological thermometers to measur e the temperature of the atmosphere are: The liquid/capillary thermometer, which includes the alcohol and mercury thermometer, uses the expansion of the volume of a liquid to measure temperature. This type thermometer has a bulb at one end to maximize the amount of liquid that is changing in volume, and a narrow capillary to "amplify" the change in volume. - Mercury-in-glass thermometer . - Alcohol-in-glass thermometer: Alcohol is used in extremely cold conditions because it has a lower freezing point (- 130°C) than mercury (- 39°C). - Mercury thermometer has silvery colour and the alcohol one are blue or red coloured because alcohol is transparent. A special kind of capillary thermometer s , are the maximum and minimum thermometers. Recording maximum and minimum temperatures (of considerable public interest, especially during heat waves or during frosts) requires special thermometers. - The maximum thermometer has a constriction in the bore just above the bulb. When the temperature rises, the mercury is forced past the constriction, but when the temperature begins to fall the mercury is prevented from returning due to the constriction. Thus the thermometer will show the highest temperature reached. The clinical thermometer used to register your body temperature is also a maximum thermometer. - Alcohol is used in minimum thermometers because of its freezing point as I say before . These thermometers contain a small coloured metal index. As the temperature falls the index is drawn along with the alcohol as it retreats. After the lowest temperature is reached and the temperature starts to rise again, the alcohol rises in the tube but flows past the index, leaving its position fixed. The minimum temperature is read where the upper end of the index joins the alcohol meniscus. In the automatic weather stations is used an automatic thermometers. These instruments use different properties of metals , like conductivity and resistivity. One of the most known is the paltinum prove Pt-100. -----
- The Pressure is one of the most importants variables for the weather forecast. Its symbol is a capital P. Ist depends on the high, as I said (have said) before. Pressure sensors take a variety of forms. The first one was invented by Torricelli in 1643. Mercury barometers use an evacuated tube, and Mercury rises or falls within this tube as the atmospheric pressure changes, pushing the Mercury higher or lower in the tube. People says that pressure is high when its over 1.013 Hpa and low when it is under 1.013 hPa. Another ones include aneroid barometers. As shown in the picture of the aneroid barometer, this instrument relies on a sealed, flexible unit which contains air at a fixed volume (the called Vidie capsules). As the atmospheric air pressure changes, this membrane expands and contracts, altering the position of a needle on the barometer. Finally a barograph is a recording aneroid barometer. It produces a paper or foil chart called a barogram that records the barometric pressure over time. -----
- We can predict the weather forecast seeing the trend of the Atmospheric Pressure. The called normal Pressure is equal to 1.013 hPa. When the pressure is higher than this we expect a sunny day... ... and when the pressure is lower a cloudy day.
- Psychrometry are a part of thermodinamics that study the properties of vapor mixtures, like humidity. The term derives from the Greek psuchron (ψυχρόν) meaning "cold" and metron (μέτρον) meaning "means of measurement". Humidity is the amount of water vapor in the air. Humidity may also be expressed as specific, absolut or relative humidity... The last one is an important metric used in forecasting weather. Saturation: is the higher amount of humidity in a given parcel of air ( maximum humidity - 100%). The dew point is the temperature to which a given parcel of air must be cooled, in this point we have the called dew point and the air vapor condense into water (and the vapor becomes water) . The condensed water is called dew. The dew point is a saturation point. Relative humidity of 100% indicates the dew point is equal to the current temperature and the air is maximally saturated with water. The instruments to mesure the humidity amount are... - The hygrometer uses the fact that some materials (like some metalls and human hair) changes in length in response to changes in humidity, with the material becoming longer when the relative humidity increases. Thus as the humidity changes, so the needle adjusts in position, in response to changes in the length of the hair. Such an instrument may seem to be a curiosity, but in fact humidity measuring instruments which depended on human hair were common for many years. - In a psychrometer, there are two thermometers, one with a dry bulb and one with a wet bulb. The dry thermometer is a normal mercury in glass thermometer, and the wet thermometer has its bulb inside a tube with water. Evaporation from the wet bulb cool the temperature, so that the wet-bulb thermometer usually shows a lower temperature than that of the dry-bulb thermometer, which measures dry-bulb temperature. You can consult a table to know the relative humidity as from the 2 temperatures. -----
- The heat index (HI) is a parameter that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature. The human body normally cools itself by perspiration, or sweating, which evaporates and carries heat away from the body. However, when the relative humidity is high, the evaporation rate is reduced, so heat is removed from the body at a lower rate causing it to retain more heat than it would in dry air. -----
- Evaporation is how the water from oceans, seas and lakes abandon the surface to form the clouds. Is a type of vaporization of a liquid, that occurs only on the surface of a liquid. The measure of this parameter is important too for the farmers to understand how much water their crops will need. Evaporimeter, sometimes called atmometer, is an instrument that measures the rate of evaporation of water into the atmosphere. The Piché evaporimeter uses an inverted graduated cylinder of water with a filter-paper seal at the mouth. Evaporation takes place from the wet filter paper and thus depletes the water in the cylinder, so that the rate of evaporation can be read directly from the graduations marking the water level. Pan evaporation is a measurement that combines or integrates the effects of several climate elements: temperature, humidity, solar radiation, and wind. Evaporation is greatest on hot, windy, dry days; and is greatly reduced when air is cool, calm, and humid. (Pan evaporation measurements aid the farmers to understand how much water their crops will need). -----
- Nephology (from the Greek word nephos for 'cloud') is the study of clouds and cloud formation. British meteorologist Luke Howard was a major researcher within this field, establishing a cloud classification system at the begining of the nineteen century. Cloud: A cloud is a visible mass of droplets, in other words, little drops of water or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. Clouds have been classified by various systems according to form, altitude, and the physical processes generating them. - Low clouds will form between Earth surface and 2-3 km (St, Cu, Sc). - Middle clouds will form between Earth 2-3 km and 6-8 km (Ns, As, Ac). - High clouds will form between 6-8 km and tropopause, 10-12 km (Ci, Cc, Cs). - Vertical clouds will form under 2 km and rises until the tropopause (Cb). The rainy clouds are Ns (warm weather front) and Cb (cold weather front). The World Meteorological Organization (International Cloud Atlas, 1956) classifies the clouds in 10 genre. -----
- Precipitation is any product of the condensation of atmospheric water vapor that is spare d down by gravity and deposited on the Earth's surface. Snow is a type of precipitation with form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Hail is a form of solid precipitation which consists of balls or irregular lumps of ice, that are individually called hail stones. Coalescence is the process by which two or more raindroplets merge (0r band) during contact to form a single large droplet. -----
- A rain gauge (also known as a udometer or a pluviometer or an cup) is a type of instrument used by meteorologists to measure the amount of liquid precipitation over a set period of time. A normalized pluviometer is called Hellman, and it consist in a big vessel calibrated to collect the rain. Pluviograph: An instrument for measuring the amount of water that has fallen, with a feature to register the data in real time to demonstrate rainfall over a short period of time, often an automated graphing instrument. -----
- Wind is the flow (movement) of air. - The Beaufort Scale is an empirical measure for describing wind speed based mainly on observed sea conditions. Level 0 (calm) to 12 (hurricane). Fujita: from 0 to 5, is a scale for rating tornado intensity, based on the damage tornadoes inflict on human-built structures and vegetation. Saffir-Simpson goes from 1 (12 beaufort) to 5 (250 kph). - Wind direction is reported by the direction from which it originates. For example, in this image wind blows from the east (to the west). Weather vanes (also called rooster vanes) pivot indicates the direction of the wind. At airports, windsocks are primarily used to indicate wind direction, but can also be used to estimate wind speed by its angle of hang. Wind speed is measured by anemometers, most commonly using rotating cups or propellers. - A wind rose is a graphic tool used by meteorologists to give a succinct view of how wind speed and direction are typically distributed at a particular location. This chart is divided in 8 courses (rumbs): mains are N,S, W, E, and secondary NE, SE, NW, SW. -----
- Wind chill is the apparent temperature felt on exposed skin due to wind. The degree of this phenomenon depends on both air temperature and wind speed. The wind chill temperature or factor is always lower than the air temperature for values where the wind chill formula is valid. -----
- As I have explained , meteorology and climatology are very important for our lifes. In the first graphic, we see the annual rainfall, and in the second the population density. There is a narrow relation ship between the two representations, because the yellow areas of the first plot (the less rainy zones like the north of the African continent or the west Australia) coincide with the low population zones of the second one, and the green areas (that indicates more rain, like the southwest Asian countries) coincide with the red areas (that indicates more population). The third one presents the distribution of the earth wealth. The GDP are the gross domestic product or the gross domestic income. This is a is a basic measure of a country's economic power ( output ) . This graphic shows too a narrow relation ship with the climatological first one. -----
- And finally, these 2 sciences helps us learn more about how to predict natural disasters (like hurricanes, floodings, droughts, climate change...) and prevent more destruction. The first and the second graphic shows the Katrina hurricane and his effects in New Orleans, in 2005 August. The third one shows the temperature trend according to the IPCC (Intergovernmental Panel for Climate Change), and warn us of future climate variation. In this graphic we can see the global surface temperature change for the dif f erent raise scenarios. We expect that this century the temperature increases between 1,1 and 6,4ºC. These sciences are very helpful too in our daily life, because help us to choose what to wear everyday, or when we have to take an umbrella. Another example that moves a large amount of money , are t he motor racing s like formula 1. In this races is basic to know the forecasting , to try the correct tyres. F1 has 3 types of tires for a race: dry, intermediate, and extreme. -----