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Climate -basic

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the presentation contains general introduction about climatology...

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Climate -basic

  1. 1. Presented by- Ar.Abhinav Srivastav Assistant Professor B.Arch, M.A.R.D, M.Tech IIT-R CLIMATE BASIC
  2. 2. Outline o Definition o Difference between Weather and Climate o Solar Geometry [Nature of sun, earth-sun relationship, Different angles like latitude, longitude, Declination, Solar time, Hour angle, Angle of incidence etc.] o Elements of Climate [Temperature, Humidity, Vapour Pressure, Precipitation, Sky condition, Solar radiation, Wind, Special Characteristic, Vegetation] o References Climate-Basic Presented by-Ar.Abhinav Srivastav
  3. 3. Definition World wide climate classification Source-Wikipedia • As per Wikipedia.com- "average of weather conditions over a long period of time" • Scientifically- "It is the integration of the physical states of the atmospheric environment, characteristic of a certain geographical location". • As per Oxford dictionary- "region with certain conditions of temperature, dryness, wind, light etc." Climate-Basic Presented by-Ar.Abhinav Srivastav
  4. 4. Difference between Weather and Climate Weather Climate The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere "behaves" over relatively long periods of time. • Weather is basically the way the atmosphere is behaving, mainly with respect to its effects upon life and human activities. • The difference between weather and climate is that weather consists of the short-term (minutes to months) changes in the atmosphere. • In short, climate is the description of the long-term pattern of weather in a particular area. • Some scientists define climate as the average weather for a particular region and time period, usually taken over 30- years. It's really an average pattern of weather for a particular region. Climate-Basic Presented by-Ar.Abhinav Srivastav
  5. 5. Weather Climate • Most people think of weather in terms of temperature, humidity, precipitation, cloudiness, brightness, visibility, wind, and atmospheric pressure, as in high and low pressure. • In most places, weather can change from minute-to-minute, hour-to-hour, day-to-day, and season-to-season. • An easy way to remember the difference is that climate is what you expect, like a very hot summer, and weather is what you get, like a hot day with pop-up thunderstorms • When scientists talk about climate, they're looking at averages of precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, and hail storms, and other measures of the weather that occur over a long period in a particular place • For example, after looking at rain gauge data, lake and reservoir levels, and satellite data, scientists can tell if during a summer, an area was drier than average. Difference between Weather and Climate Climate-Basic Presented by-Ar.Abhinav Srivastav
  6. 6. Solar Geometry Nature of Sun Sun is a medium sized yellow star that may be considered as a sphere of intensely hot gaseous matter. The sun coalesced from a cloud of gas and dust formed 4.5 billion years ago. Earth goes round the sun in an elliptic orbit as shown in Figure, not to scale. The perihelion around January 2 each year; it is farthest around July 2 each year. Climate-Basic Presented by-Ar.Abhinav Srivastav
  7. 7. Solar Geometry The Earth’s daily rotation about the axis through its two celestial poles (North and South) is perpendicular to the equator, but it is not perpendicular to the plane of the Earth’s orbit. In fact, the measure of tilt or obliquity of the Earth’s axis to a line perpendicular to the plane of its orbit is currently about 23.5°. Climate-Basic Presented by-Ar.Abhinav Srivastav
  8. 8. Solar Geometry Climate-Basic Presented by-Ar.Abhinav Srivastav
  9. 9. Solar Geometry Sun-Earth Size, Position The geometry of the sun-earth relationships is shown schematically in Figure. The distance between the sun and earth varies by 1.7 % due to the elliptic orbit of the of the earth around the sun. The sun subtends an angle of 32' with the earth. Climate-Basic Presented by-Ar.Abhinav Srivastav
  10. 10. Solar Geometry Different Angles • Latitude and Longitude are the coordinates of a point ( location ) on earth's surface. A location on the earth’s surface may be specified by latitude, longitude and elevation. Elevation, does not directly enter into calculation of different angles though may effect solar radiation received. Climate-Basic Presented by-Ar.Abhinav Srivastav
  11. 11. Solar Geometry • The constant latitude and longitude lines, north pole, south pole and the equatorial plane. (Latitude, ɸ, is reckoned positive in the northern hemisphere and negative in the southern hemisphere. Longitudes, λ, is described along with "east" or "west", meaning that the location is situated to east or to west of the Greenwich meridian. Thus, the latitude varies from - 90° to + 90 ° and the longitude varies from 0 ° to 180 ° E or 0 ° to 180 ° W. Climate-Basic Presented by-Ar.Abhinav Srivastav
  12. 12. • The latitude of a point on the earth's surface is the angle between the equatorial plane and a line that passes through that point and is normal to the surface. The north pole is 90° N; the south pole is 90° S. The 0° parallel of latitude is designated the equator, the fundamental plane of all geographic coordinate systems. • The Longitude λ, of a point on the earth's surface is the angle east or west from a reference meridian to another meridian that passes through that point. • Latitude and longitude specify the position of any location on the planet, but do not account for altitude or depth. • Declination, δ, is the angular position of the sun at solar noon with respect to the place of the equator. Declination varies from - 23.450 to 23.450. • Solar Time is the time based on the apparent angular motion of the sun across the sky, with solar noon being the time the sun crosses the meridian of the observer. Solar time is used in all sun angle relationships. • Hour angle, ω, is the angular displacement of the sun east or west of the local meridian due to rotation of earth on its axis at 15° per hour. Solar Geometry Climate-Basic Presented by-Ar.Abhinav Srivastav
  13. 13. Solar Geometry • Angle of Incidence, θ, is defined as the angle between the sun's ray and the outer normal to a surface. • Sunset hour angle, ωs, is defined as the hour angle for which the sun's rays are parallel to the horizon. Climate-Basic Presented by-Ar.Abhinav Srivastav
  14. 14. Elements of Climate Climate of a place consists of the following elements • Temperature • Humidity • Vapour pressure • Precipitation • Driving Rain • Sky condition • Solar radiation • Wind • Special characteristic • Vegetation Climate-Basic Presented by-Ar.Abhinav Srivastav
  15. 15. Elements of Climate Temperature • Temperature is a degree of hotness or coldness. It can be measured using a thermometer. It's also a measure of how fast the atoms and molecules of a substance are moving. Temperature is measured in degrees on the Fahrenheit, Celsius, and Kelvin scales. • Temperature governs the design of buildings in terms of its thermal mass, openings, ventilation pattern and many others. • Temperature varies because of the heat exchange that takes place between building and its surroundings because of conduction, convection and radiation. Thus to achieve thermal comfort, heat exchange is targeted. K=C+273 F = 9/5(C) + 32 C/5 = (F-32)/9 = (K+273)/5 Thermometer Climate-Basic Presented by-Ar.Abhinav Srivastav
  16. 16. Elements of Climate Temperature As a broad description, monthly mean temperatures can be given for each of the 12 months. The average is taken between each day’s maximum and minimum and then the average of the 30days average is found (and possibly as many years average for the same month). To give an indication of diurnal variations, this can be supplemented by monthly mean maxima and minima. Units- Celsius °C Fahrenheit °F Kelvin °K Instrument- Thermometer Climate-Basic Presented by-Ar.Abhinav Srivastav
  17. 17. Elements of Climate Humidity • Humidity of air is described as Absolute Humidity and Relative Humidity. • Absolute Humidity (AH) is the amount of moisture actually present in unit mass or unit volume of air expressed in gram per Kilogram or gram per cubic meter. • Relative humidity (RH) is the amount of moisture present against the total moisture the air can hold at that temperature. It is expressed in terms of percentage. • RH is a more useful expression for designers as it gives the direct potential of evaporation. RH = AH × 100 SH Climate-Basic Presented by-Ar.Abhinav Srivastav
  18. 18. Elements of Climate Humidity Unit- g/kg g/cubic meter Hygrometer Climate-Basic Presented by-Ar.Abhinav Srivastav
  19. 19. Elements of Climate Vapour Pressure • Vapour Pressure is a term which is less used in practical work. It is the partial pressure of the water vapour present in the air. • It can be used to calculate the humidity of the air. • The vapour pressure of saturated air is the same as the pressure of saturated vapour at the same temperature. • RH can be expressed as the ratio of the actual vapour pressure to the saturation point vapour pressure. • It can be related to other quantities using psychrometric chart. • Vapour Pressure is measured using vaporimeter. It is expressed in Newton per meter square (N/m square) RH = AH × 100 SH = 𝑃𝑣 × 100 𝑃𝑣𝑠 Climate-Basic Presented by-Ar.Abhinav Srivastav
  20. 20. Elements of Climate Precipitation • Precipitation is a collective term used for rain, snow, hail, dew and frost, that is , all forms of water deposited from atmosphere. • It is measured by rain gauges and is expressed in millimeter per a time unit (mm/day). • Values indicating the total precipitation for a month or year show the patter of dry and wet seasons. • Ever recorded maxima and minima indicate the reliability of rains and deviations from the average. • Maximum rainfall over 24 hrs is useful for prediction of floods and design of surface drainage. Rain-gauge Climate-Basic Presented by-Ar.Abhinav Srivastav
  21. 21. Elements of Climate Driving Rain • The building designer may want to know whether intense rains are associated with strong winds, in other words what is the likelihood of driving rain. • The driving rain index characteristics a given location and expresses the degree of exposure. • It is the product of annual rainfall (in m) and the annual average wind velocity (in meters per second: m/s)- thus its dimension is meter square per second. Climate-Basic Presented by-Ar.Abhinav Srivastav
  22. 22. Elements of Climate Sky condition • Sky conditions are usually described in terms of presence or absence of clouds. • It is expressed as a percentage/ proportion of sky covered by cloud (part on octets). • It is important to know the time and frequency of observations. • It is significant while designing for day lighting in buildings where sky luminance values are needed. • It is also important while designing roofs, overhangs and shading devices. Climate-Basic Presented by-Ar.Abhinav Srivastav
  23. 23. Elements of Climate Solar radiation • Solar Radiation at any place at a given point of time is expressed in W/m 2 . • This is the instantaneous intensity. • However for design purposes, along with the average intensity of solar radiation, duration of sunshine is also needed. • The intensity of radiation is recorded using solarimeter and heliometer while the duration of sunshine is calculated using simple sunshine recorder. Climate-Basic Presented by-Ar.Abhinav Srivastav
  24. 24. Elements of Climate Wind • Winds are basically convection currents in the atmosphere tending to even out the differential heating of various zones. The pattern of movements is modified by the earth's rotation. • The wind is measured by Anemometer. It gives the direction and speed of the wind. The speed is recorded in m/s. • For purpose of designing, the prevailing direction of wind along with the seasonal variation in direction and average velocity for each month should be used. Climate-Basic Presented by-Ar.Abhinav Srivastav
  25. 25. Elements of Climate Special characteristics • Most regions experience conditions which are particularly unfavorable, such as hail and thunder-stroms, line or arched squalls, earthquakes, tornadoes, hurricanes and dust storms. • Although such events may be rare, it is important to extract from metrological data their frequency, like duration and nature. • The designer must classify rare events into those which affect human comfort and those which may endanger the safety of buildings and the lives of inhabitants. • Discomfort-even if it impedes work or sleep-can be accepted if it is rare enough and lasts only for a few hours. • Structural safety, on the other hand must be guarrenteed however in frequent the danger. Climate-Basic Presented by-Ar.Abhinav Srivastav
  26. 26. Elements of Climate Vegetation • The picture of climate is incomplete without some notes on the character and abundance of plant life. • Although generally regarded as a function of climate, vegetation can in its turn influence the local or site climate. • It is an important element in the design of out-door spaces , providing sun- shading and protection from glare. • This section of the climatic survey may range from a few notes about local species of plant life to a lengthy compendium of the major native plants and trees-their shape and colour, also their preferred orientation and situation. Climate-Basic Presented by-Ar.Abhinav Srivastav
  27. 27. References Climate-Basic Presented by-Ar.Abhinav Srivastav