MET-O - Week 1 - Introduction to Meteorology and Oceanography PDF

MET-O Meteorology and Oceanography Bachelor of Science in Marine Transportation  MET-O Meteorology and Oceanography  At the end of the COURSE the students will be able to: CO1. COURSE Forecast weather conditions in a outcome particula...

MET-O Meteorology and Oceanography Bachelor of Science in Marine Transportation  MET-O Meteorology and Oceanography  At the end of the COURSE the students will be able to: CO1. COURSE Forecast weather conditions in a outcome particular area for a determined period based on all available information to maintain the safety of  At the end of the lesson the students will be able to: LO1.1. Understand the basic principles of meteorology and oceanography. Learning LO1.2. Recognize the different meteorological instruments and their outcome functions. s LO1.3. Grasp the foundational knowledge of tides and ocean currents. LO1.4. Calculate the tidal condition of a specified secondary port with the use of a Standard/secondary Form  1 Introduction to Meteorology and Oceanography CONT ENTS 2 Meteorological Instruments and Their Uses 3 Basics of Tides and Ocean Currents 4 Tides and Tidal Calculation WEEK 1 Introducti on to Meteorolo gy and Oceanogra phy 1 Introduction to Meteorology and Oceanography Marine Meteorology Introduction Marine meteorology is a subfield of meteorology, which deals with the weather and climate as well as the associated oceanographic conditions in marine, island, and coastal environments. The physical and dynamical foundations of marine meteorology are no different from other areas of meteorology, but the fundamental processes, which distinguish marine meteorology from other subfields of meteorology are the interactions between the ocean and the atmosphere. Therefore, the part of the physical oceanography dealing with the upper and coastal oceans, which are directly affected and influenced by weather is also considered an integral component of marine meteorology. 1 Introduction to Meteorology and Oceanography Marine Meteorology Marine meteorology is also unique in that it is a science geared toward the understanding and production of weather information in support of marine and coastal activities, including shipping, fishing, tourism, offshore oil drilling and mining operations, oil spill control, offshore wind and tidal energy harvesting, search and rescue at sea, and naval operations. 1 Introduction to Meteorology and Oceanography Marine Meteorology The physical processes associated with marine weather encompass not only complex marine environments from the open ocean to the coastal zone and from islands to marginal seas, but also broad dynamic scales. Small-scale phenomena include turbulence and eddies that occur within the boundary layers on both sides of the air– sea interface. These small-scale features play a major role in determining the air–sea momentum and heat and moisture fluxes that, in turn, affect the atmospheric and oceanic processes at other scales. 1 Introduction to Meteorology and Oceanography Marine Meteorology At meso- and synoptic scales, marine meteorology deals with phenomena such as coastal fronts, coastal low-level jets, land–sea breezes, coastal and sea fogs, coastal cyclones and tropical cyclones (including hurricanes and typhoons), as well as hazardous ocean conditions including storm surge, wind waves, and rip currents. At large and global scales, marine meteorology deals with the weather and climate associated with seasonal, intra-seasonal, and interannual variability in maritime environment, such as monsoons, trade wind systems, Madden–Julian oscillation, and El Niño/Southern Oscillation. 1 Introduction to Meteorology and Oceanography Marine Meteorology In the following, we will present the fundamental principles of marine meteorology and describe the observation, prediction, and application systems of marine weather and climate. 1 Introduction to Meteorology and Oceanography WEATHER ELEMENTS GENERAL DESCRIPTION OF THE ATMOSPHERE Introduction Weather is the state of the Earth’s atmosphere with respect to temperature, humidity, precipitation, visibility, cloudiness, and other factors. 1 Introduction to Meteorology and Oceanography WEATHER ELEMENTS Climate refers to the average long-term meteorological conditions of a place or region. All weather may be traced to the effect of the Sun on the Earth. Most changes in weather involve large-scale horizontal motion of air. Air in motion is called wind. This motion is produced by differences of atmospheric pressure, which are attributable both to differences of temperature and the nature of the motion itself. Weather is of vital importance to the mariner. 1 Introduction to Meteorology and Oceanography WEATHER ELEMENTS The wind and state of the sea affect dead reckoning. Reduced visibility limits piloting. The state of the atmosphere affects electronic navigation and radio communication. If the skies are overcast, celestial observations are not available; and under certain conditions refraction and dip are disturbed. When wind was the primary motive power, knowledge of the areas of favorable winds was of great importance. Modern vessels are still affected considerably by wind and sea. 1 Introduction to Meteorology and Oceanography The Atmosphere The atmosphere is a relatively thin shell of air, water vapor, and suspended particulates surrounding the Earth. Air is a mixture of gases and, like any gas, is elastic and highly compressible. Although extremely light, it has a definite weight which can be measured. A cubic foot of air at standard sea-level temperature and pressure weighs 1.22 ounces, or about 1/817th the weight of an equal volume of water. Because of this weight, the atmosphere exerts a pressure upon the surface of the Earth of about 15 pounds per square inch. 1 Introduction to Meteorology and Oceanography The Atmosphere As altitude increases, air pressure decreases due to the decreased weight of air above. With less pressure, the density decreases. More than three-fourths of the air is concentrated within a layer averaging about 7 statute miles thick, called the troposphere. This is the region of most “weather,” as the term is commonly understood. The top of the troposphere is marked by a thin transition zone called the tropopause, immediately above which is the stratosphere. Beyond this lie several other layers having distinctive characteristics. The average height of the tropopause ranges from about 5 miles or less at high latitudes to about 10 miles at low latitudes. 1 Introduction to Meteorology and Oceanography The Atmosphere The standard atmosphere is a conventional vertical structure of the atmosphere characterized by a standard sea level pressure of 1013.25 hectopascals of mercury (29.92 inches) and a sea-level air temperature of 15° C (59° F). The temperature decreases with height at the standard lapse rate, a uniform 2° C (3.6° F) per thousand feet to 11 kilometers (36,089 feet), and above that remains constant at –56.5° C (-69.7° F). The jet stream refers to relatively strong (greater than 60 knots) quasi- horizontal winds, usually concentrated within a restricted layer of the atmosphere. Research has indicated that the jet stream is important in relation to the sequence of weather. There are two commonly known jet streams. 1 Introduction to Meteorology and Oceanography The Atmosphere The sub-tropical jet stream (STJ) occurs in the region of 30°N during the northern hemisphere winter, decreasing in summer. The core of highest winds in the STJ is found at about 12km altitude (40,000 feet) in the region of 70°W, 40°E, and 150°E, although considerable variability is common. The polar frontal jet stream (PFJ) is found in middle to upper- middle latitudes and is discontinuous and variable. Maximum jet stream winds have been measured by weather balloons at 291 knots. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere The heat required to warm the air is supplied originally by the Sun. As radiant energy from the Sun arrives at the Earth, about 29 percent is reflected back into space by the Earth and its atmosphere, 19 percent is absorbed by the atmosphere, and the remaining 52 percent is absorbed by the surface of the Earth. Much of the Earth’s absorbed heat is radiated back into space. Earth’s radiation is in comparatively long waves relative to the short-wave radiation from the Sun because it emanates from a cooler body. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere Longwave radiation, readily absorbed by the water vapor in the air, is primarily responsible for the warmth of the atmosphere near the Earth’s surface. Thus, the atmosphere acts much like the glass on the roof of a greenhouse. It allows part of the incoming solar radiation to reach the surface of the Earth but is heated by the terrestrial radiation passing outward. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere Over the entire Earth and for long periods of time, the total outgoing energy must be equivalent to the incoming energy (minus any converted to another form and retained), or the temperature of the Earth and its atmosphere would steadily increase or decrease. In local areas, or over relatively short periods of time, such a balance is not required, and in fact does not exist, resulting in changes such as those occurring from one year to another, in different seasons and in different parts of the day. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere The more nearly perpendicular the rays of the Sun strike the surface of the Earth, the more heat energy per unit area is received at that place. Physical measurements show that in the tropics, more heat per unit area is received than is radiated away, and that in polar regions, the opposite is true. Unless there were some processes to transfer heat from the tropics to polar regions, the tropics would be much warmer than they are, and the polar regions would be much colder. Atmospheric motions bring about the required transfer of heat. The oceans also participate in the process, but to a lesser degree. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere If the Earth had a uniform surface and did not rotate on its axis, with the Sun following its normal path across the sky (solar heating increasing with decreasing latitude), a simple circulation would result, as shown in Figure 3402a. Figure 3402a. Ideal atmospheric circulation for a uniform and non-rotating Earth. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere However, the surface of the Earth is far from uniform, being covered with an irregular distribution of land and water. Additionally, the Earth rotates about its axis so that the portion heated by the Sun continually changes. In addition, the axis of rotation is tilted so that as the Earth moves along its orbit about the Sun, seasonal changes occur in the exposure of specific areas to the Sun’s rays, resulting in variations in the heat balance of these areas. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere These factors, coupled with others, result in constantly changing large-scale movements of air. For example, the rotation of the Earth exerts an apparent force, known as Coriolis force, which diverts the air from a direct path between high- and low-pressure areas. The diversion of the air is toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere. At some distance above the surface of the Earth, the wind tends to blow along lines connecting points of equal pressure called isobars. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere The wind is called a geostrophic wind if it blows parallel to the isobars. This normally occurs when the isobars are straight (great circles). However, isobars curve around highs and lows, and the air is not generally able to maintain itself parallel to these. The resulting cross-isobar flow is called a gradient wind. Near the surface of the Earth, friction tends to divert the wind from the isobars toward the center of low pressure. At sea, where friction is less than on land, the wind follows the isobars more closely. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere A simplified diagram of the general circulation pattern is shown in Figure 3402b. Figure 3402c and Figure 3402d give a generalized picture of the world’s pressure distribution and wind systems as actually observed. Figure 3402b. Simplified diagram of the general circulation of the atmosphere. 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere A simplified diagram of the general circulation pattern is shown in Figure 3402b. Figure 3402c and Figure 3402d give a generalized picture of the world’s pressure distribution and wind systems as actually observed. Figure 3402c. Generalized pattern of actual surface winds in January and February.  1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere A simplified diagram of the general circulation pattern is shown in Figure 3402b. Figure 3402c and Figure 3402d give a generalized picture of the world’s pressure distribution and wind systems as actually observed. Figure 3402d. Generalized pattern of actual surface winds in July and August. (See key with Figure 3402c.) 1 Introduction to Meteorology and Oceanography General Circulation of The Atmosphere A change in pressure with horizontal distance is called a pressure gradient. It is maximum along a normal (perpendicular) to the isobars. A force results which is called pressure gradient force and is always directed from high to low pressure. Speed of the wind is approximately proportional to this pressure gradient. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Doldrums A belt of low pressure at the Earth’s surface near the equator known as the doldrums occupies a position approximately midway between high pressure belts at about latitude 30° to 35° on each side. Except for significant intra-diurnal changes, the atmospheric pressure along the equatorial low is almost uniform. With minimal pressure gradient, wind speeds are lights and directions are variable. Hot, sultry days are common. The sky is often overcast, and showers and thundershowers are relatively frequent. In these atmospherically unstable areas, brief periods of strong wind occur. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Doldrums The doldrums occupy a thin belt near the equator, the eastern part in both the Atlantic and Pacific being wider than the western part. However, both the position and extent of the belt vary with longitude and season. During all seasons in the Northern Hemisphere, the belt is centered in the eastern Atlantic and Pacific; however, there are wide excursions of the doldrum regions at longitudes with considerable landmass. On the average, the position is at 5°N, frequently called the meteorological equator. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Trade Winds The trade winds at the surface blow from the belts of high pressure toward the equatorial belts of low pressure. Because of the rotation of the Earth, the moving air is deflected toward the west. Therefore, the trade winds in the Northern Hemisphere are from the northeast and are called the northeast trades, while those in the Southern Hemisphere are from the southeast and are called the southeast trades. The trade- wind directions are best defined over eastern ocean areas. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Trade Winds The trade winds are generally considered among the most constant of winds, blowing for days or even weeks with little change of direction or speed. However, at times they weaken or shift direction, and there are regions where the general pattern is disrupted. A notable example is found in the island groups of the South Pacific, where the trades are practically nonexistent during January and February. Their best development is attained in the South Atlantic and in the South Indian Ocean. In general, they are stronger during the winter than during the summer season. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Trade Winds In July and August, when the belt of equatorial low pressure moves to a position some distance north of the equator, the southeast trades blow across the equator, into the Northern Hemisphere, where the Earth’s rotation diverts them toward the right, causing them to be southerly and southwesterly winds. The “southwest monsoons” of the African and Central American coasts originate partly in these diverted southeast trades. Cyclones from the middle latitudes rarely enter the regions of the trade winds, although tropical cyclones originate within these areas. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Horse Latitudes Along the poleward side of each trade-wind belt and corresponding approximately with the belt of high pressure in each hemisphere, is another region with weak pressure gradients and correspondingly light, variable winds. These are called the horse latitudes, apparently so named because becalmed sailing ships threw horses overboard in this region when water supplies ran short. The weather is generally good although low clouds are common. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Horse Latitudes Compared to the doldrums, periods of stagnation in the horse latitudes are less persistent. The difference is due primarily to the rising currents of warm air in the equatorial low, which carry large amounts of moisture. This moisture condenses as the air cools at higher levels, while in the horse latitudes the air is apparently descending and becoming less humid as it is warmed at lower heights. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Prevailing Westerlies On the poleward side of the high-pressure belt in each hemisphere, the atmospheric pressure again diminishes. The currents of air set in motion along these gradients toward the poles are diverted by the Earth’s rotation toward the east, becoming southwesterly winds in the Northern Hemisphere and northwesterly in the Southern Hemisphere. These two wind systems are known as the prevailing westerlies of the temperate zones. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Prevailing Westerlies In the Northern Hemisphere this relatively simple pattern is distorted considerably by secondary wind circulations, due primarily to the presence of large landmasses. In the North Atlantic, between latitudes 40° and 50°, winds blow from some direction between south and northwest during 74 percent of the time, being somewhat more persistent in winter than in summer. They are stronger in winter, too, averaging about 25 knots (Beaufort 6) as compared with 14 knots (Beaufort 4) in the summer. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Prevailing Westerlies In the Southern Hemisphere the westerlies blow throughout the year with a steadiness approaching that of the trade winds. The speed, though variable, is generally between 17 and 27 knots (Beaufort 5 and 6). Latitudes 40°S to 50°S, where these boisterous winds occur, are called the roaring forties. These winds are strongest at about latitude 50°S. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS The Prevailing Westerlies The greater speed and persistence of the westerlies in the Southern Hemisphere are due to the difference in the atmospheric pressure pattern, and its variations, from the Northern Hemisphere. In the comparatively landless Southern Hemisphere, the average yearly atmospheric pressure diminishes much more rapidly on the poleward side of the high-pressure belt, and has fewer irregularities due to continental interference, than in the Northern Hemisphere. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Polar Winds Partly because of the low temperatures near the geographical poles of the Earth, the surface pressure tends to remain higher than in surrounding regions, since cold air is more dense than warm air. Consequently, the winds blow outward from the poles, and are deflected westward by the rotation of the Earth, to become northeasterlies in the Arctic, and southeasterlies in the Antarctic. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Polar Winds Where the polar easterlies meet the prevailing westerlies, near 50°N and 50°S on the average, a discontinuity in temperature and wind exists. This discontinuity is called the polar front. Here the warmer low-latitude air ascends over the colder polar air creating a zone of cloudiness and precipitation. In the Arctic, the general circulation is greatly modified by surrounding landmasses. Winds over the Arctic Ocean are somewhat variable, and strong surface winds are rarely encountered. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Polar Winds In the Antarctic, on the other hand, a high central landmass is surrounded by water, a condition which augments, rather than diminishes, the general circulation. The high pressure, although weaker than in the horse latitudes, is stronger than in the Arctic, and of great persistence especially in eastern Antarctica. The cold air from the plateau areas moves outward and downward toward the sea and is deflected toward the west by the Earth’s rotation. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Polar Winds The winds remain strong throughout the year, frequently attaining hurricane force near the base of the mountains. These are some of the strongest surface winds encountered anywhere in the world, with the possible exception of those in well-developed tropical cyclones. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation The general circulation of the atmosphere is greatly modified by various conditions. The high pressure in the horse latitudes is not uniformly distributed around the belts, but tends to be accentuated at several points, as shown in Figure 3402c and Figure 3402d. These semi-permanent highs remain at about the same places with great persistence. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Figure 3402c. Generalized pattern of actual surface winds in January and February. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Figure 3402d. Generalized pattern of actual surface winds in July and August. (See key with Figure 3402c.) 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation Semi-permanent lows also occur in various places, the most prominent ones being west of Iceland, and over the Aleutians (winter only) in the Northern Hemisphere, and in the Ross Sea and Weddell Sea in the Antarctic areas. The regions occupied by these semi-permanent lows are sometimes called the graveyards of the lows, since many lows move directly into these areas and lose their identity as they merge with and reinforce the semi-permanent lows. The low pressure in these areas is maintained largely by the migratory lows which stall there, with topography also important, especially in Antarctica. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation Another modifying influence is land, which undergoes greater temperature changes than does the sea. During the summer, a continent is warmer than its adjacent oceans. Therefore, low pressures tend to prevail over the land. If a climatological belt of high pressure encounters a continent, its pattern is distorted or interrupted, whereas a belt of low pressure is intensified over the same area. In winter, the opposite effect takes place, belts of high pressure being intensified over land and those of low pressure being weakened. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation The most striking example of a wind system produced by the alternate heating and cooling of a landmass is the monsoon (seasonal wind) of the China Sea and Indian Ocean. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation A portion of this effect is shown in Figure 3408a and Figure 3408b. In the summer, low pressure prevails over the warm continent of Asia, and relatively higher pressure prevails over the adjacent, cooler sea. Between these two systems the wind blows in a nearly steady direction. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Figure 3408a. The summer monsoon. Figure 3408b. The winter monsoon. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation The lower portion of the pattern is in the Southern Hemisphere, extending to about 10° south latitude. Here the rotation of the Earth causes a deflection to the left, resulting in southeasterly winds. As they cross the equator, the deflection is in the opposite direction, causing them to curve toward the right, becoming southwesterly winds. In the winter, the positions of high- and low-pressure areas are interchanged, and the direction of flow is reversed. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation In the China Sea, the summer monsoon blows from the southwest, usually from May to September. The strong winds are accompanied by heavy squalls and thunderstorms, the rainfall being much heavier than during the winter monsoon. As the season advances, squalls and rain become less frequent. 1 Introduction to Meteorology and Oceanography MAJOR WIND PATTERNS Modifications of the General Circulation In some places the wind becomes a light breeze which is unsteady in direction, or stops altogether, while in other places it continues almost undiminished, with changes in direction or calms being infrequent. The winter monsoon blows from the northeast, usually from October to April. It blows with a steadiness similar to that of the trade winds, often attaining the speed of a moderate gale (28–33 knots). Skies are generally clear during this season, and there is relatively little rain. 1 Introduction to Meteorology and Oceanography Any questions? 1 Introduction to Meteorology and Oceanography Q&A Session Thank you for listening!  To summarize this topic, we have discussed the Introduction to Meteorology and Oceanography: Determine latitude and line of Of the position using Pole Star Observation, within ±2° of the topic correct answer. Plot ship's position using position lines from Pole Star Observation within ±2.0 nm of the correct answer. END OF TOPIC WEEK 2 Meteorolo gical Instrumen ts and Their Uses 2 Meteorological Instruments and Their Uses Weather Instruments & Their Uses Meteorologists use a wide variety of different instruments to measure weather conditions, but many of these weather instruments fall into relatively common, overarching categories. Thermometers, for instance, come in traditional liquid-in-glass forms and newer electronic forms, but both measure temperature in Celsius and Fahrenheit. Other instruments measure aspects of weather like rainfall, pressure, humidity, wind direction, and wind speed. These instruments and measurements allow meteorologists to make predictions on weather conditions in the near future.  2 Meteorological Instruments and Their Uses Weather Instruments & Their Uses Weather stations are strategically positioned collections of many instruments. The provide crucial information for meteorology and weather forecasting. Stations often have many types of weather instruments that are all chosen to provide an accurate and expansive survey of the current weather conditions. To provide even more real time measurements hundreds of weather balloons are launched across the world every day; they float thousands of feet into the atmosphere carrying meteorological instruments to measure wind conditions, air temperature, and pressure in the sky. Because weather is so complicated, it helps to have as much data from very different altitudes and locations.  2 Meteorological Instruments and Their Uses Daily Temperatures A thermometer measures the high and low outdoor temperatures in degrees Fahrenheit and degrees Celsius. Meteorologists first used liquid-in-glass thermometers in the late 1800s, but they now use electronic maximum-minimum temperature sensor systems more frequently. The newer systems use an electronic temperature sensor to measure and record high and low temperatures. 2 Meteorological Instruments and Their Uses Atmospheric Pressure Barometers measure atmospheric pressure (sometimes also called barometric pressure), providing the measurement in millibars. Under most conditions, high and rising pressure indicates sunny weather, while low and falling pressure indicates approaching rainy storms. The traditional aneroid barometer first appeared in the 1840s. The micro-barograph also measures air pressure but records its continuous measurements on paper. There are many varieties of digital barometers and more analog measurement tools to measure atmospheric pressure. 2 Meteorological Instruments and Their Humidity Uses Sensors Hygrometers measure temperature and humidity using degrees Celsius and degrees Fahrenheit. One type of hygrometer, called a sling psychrometer, uses one dry and one wet bulb thermometer to measure the relative humidity, or amount of water vapor, of the air. Some older hygrometers used a sheaf of hair, which increases in length as relative humidity increases. 2 Meteorological Instruments and Wind Their Speed Uses Anemometers measure the direction and speed of wind in miles per hour. A common type of anemometer has three cups fixed to a mobile shaft. As the wind blows faster, the cups spin around faster. The actual speed of the wind shows up on a dial. Another type of anemometer uses a propeller instead of cups to accomplish the same function. 2 Meteorological Instruments and Wind Their Vane Uses A wind vane, also called a wind-sock, measures the direction of the wind at any given point in time. A weighted arrow spins around a fixed shaft and points north, south, east or west, typically marked on separate fixed shafts parallel to the arrow. 2 Meteorological Instruments and Their Uses Rain Gauge A rain gauge measures the amount of rainfall. The standard rain gauge consists of a long, narrow cylinder capable of measuring rainfall up to 8 inches. Many rain gauges measure precipitation in millimeters, or to the nearest 100th of an inch. Other gauges collect the rain and weigh it, later converting this measurement into inches. There are also snow gauges designed to accurately measure snowfall. 2 Meteorological Instruments and Their Uses Hail Pad Hail pads measure the size of hail that falls during a storm. A standard hail pad consists of florist's foam and aluminum foil. The falling hail strikes the foil and creates dimples for the observer to measure after the storm. 2 Meteorological Instruments and Their Campbell Uses Stokes Recorder The Campbell Stokes Recorder measures sunshine. Sunlight shines into one side of a glass ball and leaves through the opposite side in a concentrated ray. This ray of light burns a mark onto a thick piece of card. The extensiveness of the burn mark indicates how many hours the sun shone during that day.  2 Meteorological Instruments and Tools Their Used inUses Meteorology Before the 1600s, knowledge of the Earth's atmosphere and weather was not exact. People mostly relied on experience with local weather events for forecasts. Aunt Sally could smell a snowstorm coming, and Uncle Jim's knee told of impending rain. Then simple devices, such as thermometers, barometers and weather-vanes, were invented that gave recordable data. As technology advanced from the 1800s onward, more sophisticated equipment allowed detection of regional and global weather patterns, and modern radar, satellites and computer modeling programs allow long-term weather predictions. 2 Meteorological Instruments and Their Equipment Temperature Uses Glass thermometers filled with either alcohol or mercury are standard equipment for measuring air, soil and water temperatures. Maximum and minimum temperature thermometers register the lowest and highest temperatures during a specific time period. The resistance temperature detector determines air temperatures based on changes in electrical resistance of specific metals due to temperature and gives a digital readout. Preferred for automatic weather stations, RTDs can supply a temperature reading every second. 2 Meteorological Instruments and Their Uses Atmospheric Pressure and Wind Barometers measure atmospheric pressure. Liquid barometers usually measure mercury contained within an evacuated tube, and the mercury level changes as atmospheric pressure increases or decreases. Aneroid barometers contain a fixed volume of air sealed within a unit equipped with a flexible membrane. As the membrane expands and contracts with changes caused by atmospheric pressure conditions, an attached needle points to the correct reading. Wind anemometers measure the direction and speed of wind. They usually incorporate a weather-vane tail and a fan to measure speed. 2 Meteorological Instruments and Their Moisture Uses Indicators There are several tools that measure humidity, or the percentage of water in air. The earliest was the hygrometer, which depends on a human hair expanding and contracting in response to humidity changes. The psychrometer detects the difference in temperature between a dry and a wet thermometer bulb to measure humidity. Other instruments include the electrical hygrometer, the dew-point hygrometer, the infrared hygrometer and the dew cell. Rain gauges measure rainfall, and snow gauges measure snowfall. 2 Meteorological Instruments and Their Weather Uses Balloons Weather balloons measure humidity, air pressure, temperature, wind speed and direction with units called radiosondes. Launched from 1,100 sites around the world twice a day, they rise to over 20 miles above the Earth, recording as they travel and transmitting the information back to meteorologists by radio waves. When the balloon bursts, the radiosonde parachutes back to Earth for recycling. Weather balloons give a vertical snapshot of atmospheric conditions in a given area. 2 Meteorological Instruments and Their High-Tech Uses Tools With the invention of radar in World War II, meteorological studies vastly improved. Conventional radar, Doppler radar and dual-polarization radar detect storm systems, their direction, speed, intensity and type of precipitation. Meteorological satellites orbiting the Earth began transmitting in 1962 and led to more complicated satellites. Geostationary Operational Environmental Satellites transmit photographic images of the Western Hemisphere every 15 minutes. Polar Operational Environmental Satellites take about 1.5 hours to orbit the Earth, providing information about weather, oceans and volcanic eruptions. Computer analysis of weather data and computer modeling of weather systems make long-term weather prediction on a global scale increasingly more accurate. 2 Meteorological Instruments and TypesTheir Uses of Old-Fashioned Weather Instruments Greek philosophers Aristotle and his pupil Theophrastus showed interest in weather phenomena more than three centuries before the start of the Common Era (CE). However, measuring tools and instruments were needed for the study of weather as a science, meteorology, to flourish. Functional weather instruments began with Galileo's invention of a rudimentary thermometer in the late 1500s. Many old-fashioned instruments continue to be used in private settings and small weather stations. 2 Meteorological Instruments and Their Uses Anemometers Italian architect Leone Battista Alberti (1404-1472) is credited with inventing the first useful anemometer, an instrument to measure wind speed. Alberti's anemometer used a swinging-plate; the angle at which the plate was displaced by the force of wind determined wind speed. In 1846, Irish astronomer Thomas Romney Robinson developed the rotating-cup anemometer that is still used in small weather stations. Robinson's old-fashioned anemometer uses four cups attached to a vertical rod at right angles. As the wind rotates the cups, the speed of the turns is converted to wind speed. 2 Meteorological Instruments and Their Uses Barometers The barometer, an instrument for measuring air pressure, was invented by Italian mathematician and physicist Evangelista Torricelli in 1643. Using observation of how a siphon works, Torricelli used a mercury-filled tube to determine atmospheric pressure at sea level. In an old-fashioned mercury barometer, the weight of the atmosphere forces mercury up a calibrated tube. The heavier the air, the more pressure exerted on the mercury. 2 Meteorological Instruments and Their Uses Hair Hygrometer Water-absorbing properties of hair were used in 1783 to develop the first hygrometer, an instrument for measuring humidity. This old- fashioned hygrometer was calibrated by first determining the length of a hair at total dehydration and at total saturation, or 0 percent humidity and 100 percent humidity, respectively. Relative humidity then could be calculated by using these two set points. 2 Meteorological Instruments and Sling Their Uses Psychrometer As an instrument for measuring humidity, the sling psychrometer came into use during the 19th century. This old-fashioned weather instrument used two identical mercury thermometers mounted on a wooden paddle. The bulb of one of the thermometers is wrapped in wet absorbent materials. A person then whirls (slings) the handle around through the air and the thermometer with the wet bulb cools rapidly compared to the other due to evaporation properties of water. The temperature difference between the two thermometers can then be converted to relative humidity. 2 Meteorological Instruments and Their Uses Thermometers Galileo's thermometer measured heat by observing the changes in the density of water in glass-filled bulbs. This method of liquid in a sealed glass bulb or tube was used to design and develop a number of old-fashioned instruments that work on the principle of the changes in water when heated and cooled to measure temperature changes. 2 Meteorological Instruments and Their Different Uses Types of Anemometers An anemometer is a device for measuring the force or speed of the wind. This instrument has been around since at least 1450. Many different types of anemometers are on the market, each with unique characteristics. Some of the devices measure more than just wind speed. Some people for fun build their own anometers -- that's something you might want to try as well. 2 Meteorological Instruments and Their Different Uses Types of Anemometers Cup The cup or rotational anemometer is one of the oldest types of anemometers. The cups are placed onto a vertical axis, and when the wind presses against them, this causes the cups to rotate around. The faster the cups rotate, the faster the wind speed. Cup anemometers usually have digital readouts. Researchers, educational institutions and meteorologists worldwide use this type of anemometer for research and commercial activities. 2 Meteorological Instruments and Their Different Uses Types of Anemometers Hot Wire Hot wire or thermal flow anemometers measure both the wind speed and pressure. The device is a long rod and at the tip is a hot wire or hot bead. The anemometer is placed into a location and as wind moves over the hot wire, the wire is cooled. A direct relationship exists between the rate at which the wind is flowing and how cool the wire becomes. You can find this type of anemometer in the heating, ventilating and air-conditioning businesses -- it measures the airflow through building ducts. 2 Meteorological Instruments and Their Different Uses Types of Anemometers Windmill The windmill anemometer measures both wind speed and direction. The anemometer has a propeller located at the front of the device and a large tail section. As the wind blows, it presses against the propeller, making it spin. The rotational speed of the propeller indicates how fast the wind is moving at any time. 2 Meteorological Instruments and Their Different Uses Types of Anemometers Pressure Tube A pressure tube anemometer is called a wind-sock. These devices are found around airports. Material is made into a tube shape and is connected to wires. As the wind blows, it catches the larger end of the tube. This anemometer provides wind direction because the larger end of the sock will move into the wind. The faster the wind blows, the higher the tube raises off the ground. Pressure tubes do not provide readouts but are relative measurements of wind speed. 2 Meteorological Instruments and Their Different Uses Types of Anemometers Ultrasonic Ultrasonic anemometers send sonic pulses across a path to a sensor on the opposite side. As the wind moves more quickly, the pulses are disrupted. A measurement of this disruption provides accurate wind data. An ultrasonic anemometer has no moving parts and can detect even small changes in the wind. The device typically has four sensors arranged in a square pattern. Some units come with built-in heaters. 2 Meteorological Instruments and Their Different Uses Types of Anemometers Laser Doppler Laser Doppler anemometers utilize the Doppler effect to determine the flow of air. Commonly used for high-tech applications such as in jet engines, the laser Doppler can measure even the slightest changes in airflow. This type of anemometer is also used in river hydrology. 2 Meteorological Instruments and What Their Uses Units Do Barometers Measure In? A barometer is an instrument used to measure air pressure and track weather systems. The most common unit of measurement used in barometers is the millibar (mb). 2 Meteorological Instruments and What Their Uses Units Do Barometers Measure In? Fact A millibar is a form of metric measurement, with one millibar equaling one one-thousandth of a bar or 100 pascals, which is equivalent to one newton per square meter. Use Millibars are used to measure atmospheric pressure or altitude. Normal atmospheric pressure measures 1,013.2 millibars. Features The two types of barometers are mercury and aneroid. In a mercury barometer, millibars measure how high the mercury column climbs a vertical glass tube. Aneroid barometers don’t use liquid of any kind, instead employing a flexible-walled evacuated capsule. 2 Meteorological Instruments and What Their Uses Units Do Barometers Measure In? Types Aside from millibars, other units of measure used in barometers include pounds per square inch, pascals and inches of mercury. Function A highly sensitive unit of measurement, one millibar indicates a change of one tenth of one percent in the atmospheric pressure. 2 Meteorological Instruments and TypesTheir Uses of Hygrometers Hygrometers are instruments that measure humidity, or the amount of water vapor in the air. These devices are essential for weather measurement and forecasting, and for maintaining optimal storage conditions for moisture-sensitive materials. Using a hygrometer to measure humidity levels inside your home can help you decide whether you need a dehumidifier. High levels of water vapor can promote mold growth and food spoilage and may cause serious problems for people who have allergies. 2 Meteorological Instruments and TypesTheir Uses of Hygrometers Psychrometers This type of hygrometer uses two thermometers to measure humidity through evaporation. One is a wet-bulb thermometer and one is a dry-bulb thermometer. To measure relative humidity, the user wraps a wet cloth around the base of the wet-bulb thermometer. Whirling the device, or blowing air across the bulbs, causes the water in the wet cloth to evaporate, cooling the thermometer. The amount and rate of cooling depends on the amount of water in the air. By noting the difference in temperature between the two thermometers, and referring to a standard chart, it's possible to calculate relative humidity. A similar device called a hygrodeik includes a nomograph, which is a chart with a movable needle. The nomograph notes the two different temperatures, and the needle moves to the chart's corresponding temperature coordinates as evaporation proceeds. The needle's final position on the graph shows the relative humidity. 2 Meteorological Instruments and TypesTheir Uses of Hygrometers Electrical Hygrometers These hygrometers contain a semiconductor, which usually comprises a thin layer of lithium chloride. The semiconductor measures the change in electrical resistance as the amount of water vapor in the air changes. Humidors and other storage areas are often equipped with electrical hygrometers, in order to maintain humidity at the correct level and prevent excess water vapor from ruining sensitive materials. 2 Meteorological Instruments and TypesTheir Uses of Hygrometers Dew-Point Hygrometers Dew-point hygrometers measure humidity with a polished metal mirror that cools at a constant air pressure and water vapor content until moisture begins to condense on the surface. The temperature at which condensation forms is called the dew point. Meteorologists use the dew point to predict weather conditions associated with high humidity, like fog, snow, mist and rain. These conditions are most likely to occur when the dew point is identical to the air temperature. Dew point gives a better overall picture of atmospheric water saturation than relative humidity, which depends on the temperature of the air, and changes when the air temperature changes. By contrast, the dew point temperature provides an absolute measurement of how much moisture is actually present in the air. 2 Meteorological Instruments and TypesTheir of RainUses Gauges Rainfall is measured at thousands of weather stations across the United States using various types of rain gauges. These vary in complexity from simple measuring cylinders to sophisticated optical detectors. The simplest kind has been used at U.S. weather offices for more than 100 years. Measuring Cylinder Rain Gauge The simplest and most widely used rain gauges simply consist of a large cylinder, a funnel and a plastic measuring tube. As rain falls to the ground, it is collected by the funnel and travels to the plastic measuring tube. The amount of rain collected within a day can be read off the measuring tube. The 8-inch Standard Rain Gauge, or SRG, is based upon this simple water-collection system and has been used in weather offices for more than 100 years. 2 Meteorological Instruments and TypesTheir of RainUses Gauges Tipping-Bucket Rain Gauge The tipping-bucket rain gauge consists of a funnel within a cylinder located above a pair of buckets that are balanced about a horizontal axis. Rain enters the funnel, pours into the cylinder and drains into the bucket. When a certain amount of water has been collected, the bucket tips and causes the second bucket to quickly move into position to collect rain. The buckets typically tip over after collecting 0.01 inches (0.03 centimeters) of rain. Each time this occurs, an electronic signal is sent to a computer. Monitors can count the number of electrical signals to estimate total precipitation within a given time. 2 Meteorological Instruments and TypesTheir of RainUses Gauges Weighing Rain Gauge A weighing rain gauge consists of cylinder that is placed upon an electronic scale. As water enters the cylinder, the weight increases and provides an indirect measure of rainfall. The electronic scales are either connected to a chart that traces rainfall over time or a computer that logs the data. The weight of water can be easily converted to inches of rainfall by using the density of water and the dimensions of the measuring cylinder. 2 Meteorological Instruments and TypesTheir of RainUses Gauges Optical Rain Gauge Optical rain gauges consists of a light source, such as a laser, and an optical detector. As rain drops fall through the gap between the laser and optical detector, the amount of light hitting the optical detector is reduced. The variation in light intensity upon the optical detector is proportional to rainfall. Optical rain gauges were developed in the late 1990s and are relatively expensive.