Earth sun relationship

Climatology I- Describes the sun and earth relationship. the planet, zones and the formation of climate

1. Earth Sun Relationship

2. What is Earth The third planet from the Sun and the only astronomical object known to harbour life

3. What is Sun? The  Sun  is the star at the centre of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth.

4. Earth’s rotation Turning eastward direction at uniform rate every 24 hours. The most intense incoming sola radiation occurs where the sun’s rays strike the earth at highest angle. As the sun angle decreases the beam of light is spread over a larger area and the intensity decreases due to thickness of atmosphere, increase in reflection and scattering of light. The tilt of axis is responsible for opposite seasons in northern and southern hemisphere.

5. Earth’s revolution Equinox – Wednesday, 20 March 2019 Sun lies directly above the equator Summer solstice – Friday, 21 June 2019 Sun lies directly above the tropic of Cancer Equinox - Monday, 23 September 2019 Axis of rotation parallel to sun rays. Winter – Sunday, 22 December 2019 Sun rays are direct at tropic of Capricorn

6. Solstices 6 months of night at the north pole. Marks the shortest day in the northern hemisphere. 6 months of night at the south pole.

7. Equinoxes The axis of earth’s rotation is still tilted but it is inclined sideways with respect to the sun. At these times, the tangent rays strike the poles so that the days & nights are equal over the entire earth. The autumnal equinox on September 22 indicates the beginning of autumn season in the northern hemisphere. March 22 is the first day of spring season & hence this date is known as the spring equinox. Equinoxes mark the transition between the two extreme seasons, summer & winter.

8. Weather Monsoon when most of the region’s average annual rainfall occurs. Winter is when the hemisphere is tipped away from the sun. Summer is when the hemisphere is tipped towards the sun. Monsoon is followed by Autumn Spring is time between winter and summer where the rise in temperature is pleasant

9. Solar Radiation The energy received by all the earth’s surface is in three forms of radiation Ultra-violet 290 nm to 280 nm, produces photo-chemical effects, bleaching, sunburn etc. Visible light 380 nm (violet) to 700 nm (red) Infra-red radiation 700 nm to 2300 nm, radiant head and some photo chemical effect. Solar radiation provides heat, light, and energy necessary for all living organisms. Infrared radiation supplies heat to all habitats, on land and in the water. Without solar radiation, Earth’s surface would be about 32°C colder.

10. Radiation at earth surface The sun’s radiation must make it through multiple barriers before it reaches Earth’s surface. The first barrier is the atmosphere. About 26% of the sun’s energy is reflected or scattered back into space by clouds and particulates in the atmosphere. Another 18% of solar energy is absorbed by the Ozone. Ozone absorbs ultraviolet radiation, while carbon dioxide and water vapor can absorb infrared radiation. The remaining 56% of solar radiation is able to reach the surface. 

11. Albedo The ratio of reflected radiation to the total intercepted radiation, in terms of percentage of reflected radiation. The albedo of earth’s atmosphere is 0.30 The moon’s is only 0.07, that means it absorbs most of the solar radiation striking its surface Fresh snow 0.75 – 0.90 Cloud tops 0.60 – 0.90 Old snow 0.50 – 0.70 Sand 0.15 – 0.35 Seas (high sun angle) 0.05 – 0.10 Forests 0.03 – 0.10

12. Heat loss by the earth surface The total amount of heat absorbed by the earth each year is balanced by a corresponding heat loss. Without the cooling the thermal balance of earth would not be maintained. By long-wave radiation to cold outer space, around 16% escapes to space. By evaporation as the surface liquid changes into vapour and mixes with the air. By convection air coming in contact with the warm earth surface becomes lighter and rises to the upper atmosphere and dissipates its heat to space.

13. Convection currents Winds are convection currents in the atmosphere. Trying to even out the differential heating of various zones. The movement pattern is modified by the earth’s rotation.

14. Regions Polar regions Tropic regions Desert

15. Global wind pattern At the maximum heating zones, air is heated by the hot surface. It expands, pressure decreased, it becomes lighter and rises vertically and flows off at a high level towards colder regions. Part of this air, cools down and descends at the surface in subtropics region. From here the cooler, heavier air is drawn in towards the equator from north and south.

16. The area where the air rises, where northern and southern winds meet, the tropical front is formed and is called Intertropical Convergence Zone (ITCZ) The polar easterlies are winds that are found between 60 and 90 degrees north and south latitude that blow from the poles and are deflected towards the west. Tropical easterlies or trade winds blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere and are located between 0 and 30 degrees north and south latitude. Prevailing Westerlies are winds located 30 to 60 degrees north and south of the equator that blow eastward towards the poles. Global wind pattern

17. Wind shifts When these winds are averaged over many years a well-defined pattern of large-scale ' cells ' of circulation appears. Engineer Cameron Beccario of NullSchool has created the EarthWindMap , a truly mesmerizing animated interactive view of global weather patterns using forecasted information from a variety of reliable sources.

18. Annual wind shifts The global wind pattern shift from north to south and back again. Remaining broadly symmetrical about the inter-tropical convergence zone.

19. Influence of Topography The force, direction and moisture content of air flows are strongly influences by the topography. Air can be funneled by mountain ranges. Air flow deflected upwards, as it cools, releases moisture content. Rainfall characteristics vary between locations on windward and leeward slopes od mountain ranges.

20. energy cycle Gases in Earth’s atmosphere absorb some of the outgoing energy and return part of it to the Earth's surface. These gases (water vapour, carbon dioxide, methane, nitrous oxide, ozone and some others) act like a blanket by trapping some of the heat.

21. Controls of climate The most fundamental control of both weather & climate is the unequal heating & cooling of the atmosphere in different parts of the earth. Unequal heating occurs due to differential between high & low latitudes, between continents & oceans, between snow-covered & snow-free areas, between forested & cultivated land. These heating & cooling differences & the air movements they induce represent the overall general background control of climate.

22. Latitudinal variations in solar radiation Most basic climate control factor. In low latitudes the sun is high in the sky, the solar radiation intense & the climate is warm & tropical; in high latitudes the sun is lower in the sky, solar radiation is weaker and the climate is cooler. 2. Altitudes Temperature normally decreases with increasing altitude. When a high mountain chain lies in the path of prevailing winds, it acts to block the movement of air & hence the transfer of warm or cold air masses.

23. 3. Distribution of continents & oceans Continents heat & cool rapidly than oceans. Consequently non-coastal continental areas experience more intense summer heat & winter than oceanic areas. 4. Pressure & wind systems Differences in heating & cooling between high and low latitudes, land & water etc. lead not only to regional temperature contrasts but also to differences in atmospheric pressure which in turn induce air movements. Air in motion serves as a transporter of heat from regions of net heat gain to region of heat loss thus operating as a major climate control.

24. 5. Ocean currents Ocean currents both warm & cold, which are induced by the major wind systems are also an important climatic control. They are responsible in transporting warmth & chill in a north-south direction. 6. Local features The climate of a place is affected by a variety of local features such as the slope of the land, characteristics of vegetation & soil. In the northern hemisphere, south-facing slopes receive more direct sunlight & have a warmer climate than those with a northern exposure. Urban areas are usually warmer than the adjacent villages.

25. Coriolis force The tendency of the atmosphere to lag behind the earth’s rotation where the rotation is the fastest i.e. at the Equator. There is slippage at the boundary layer, between earth’s and the atmosphere called Coriolis force. The effect is experienced as a wind blowing in opposite direction to the earth’s rotation.

26. Solar Geometry "Solar Azimuth”  is the bearing of the sun from true south.  At solar noon, the sun is at true south and the solar azimuth angle is defined as 0. Morning angles are measured as negative. "Solar Altitude”  is the bearing of the sun above the horizon.  At sunrise and sunset, the solar altitude angle is 0.  At solar noon, the sun reaches its highest point (greatest altitude).  

27. Sun path While viewing the sun from different locations on the earth, the sun will rise and set from a different point on the horizon and move along different paths across the sky . To understand where you stand on the earth, it is specified by the latitude and longitude coordinates. The latitude and longitude will have significant effects on the sun path and hence affect the behavior of the sun’s lighting and heating characteristics .

28. Altitude is the angular distance above the horizon measured perpendicularly to the horizon. It has a maximum value of 90 at the zenith, which is the point overhead. Azimuth is the angular distance measured along the horizon in a clockwise direction.

29. Azimuth Lines - Azimuth angles run around the edge of the diagram. Altitude Lines - Altitude angles are represented as concentric circular dotted lines that run from the center of the diagram out. Date Lines - Date lines start on the eastern side of the graph and run to the western side and represent the path of the sun on one particular day of the year . Hour Lines - Hour lines are shown as figure-eight-type lines that intersect the date lines and represent the position of the sun at a specific hour of the day . The intersection points between date and hour lines give the position of the sun. The Sun path Diagram- Few terminologies

30. What is a Heliodon ? A heliodon is a device that simulates the angle at which sunbeams strike a physical model of a building or landscape.  All heliodons consist of one or more light sources and a mechanism to support the model and to rotate it through one to three axes.  Since the three variables of -latitude , -time of year , & -time of day determine sun angles, a heliodon must be adjustable for all three factors.   M any different types of heliodons exist but most utilize one light to simulate the sun. Most heliodons simulate sunbeams by a combination of moving the light source and rotating the model .   Only a few heliodons exist where our everyday experience is replicated by the model being fixed in a horizontal position and the light moves along three axes to adjust for all 3 variables.

31. Energy consumption is the primary cause of climate change, and buildings use about 50% of the energy consumed. Buildings use energy primarily for heating, cooling, and lighting all of which are all greatly impacted by the sun.  Solar responsive design can significantly reduce this energy demand by harvesting the winter sun for heating, by rejecting the summer sun to reduce the cooling load.   Successful solar responsive design requires a thorough understanding of solar geometry and its impact on design.  Heliodons can teach developers, builders, and architects the basic concepts that will allow them to design low-energy solar-responsive buildings. Why should we use Heliodons ?

32. The Sun Simulator heliodon is conceptually clear because it imitates our everyday experience of the sun passing across the sky-dome , and the model being fixed on a horizontal ground plane. It is a large device usually greater than 10 ft (3 m) in diameter that cannot be easily moved. Although it is built for a particular latitude, the model support table can be tilted plus or minus 5 degrees yielding a 10 degree latitude range without loss of clarity. Because of annual symmetry, only seven arches are needed to simulate the 21st day of all 12 months. For example, only one arch is needed to define the sunpaths for both November 21 and January 21. The Sun Simulator has a light for each hour of daylight for each month . The switches that control these lights can be located on a control panel, in a wired remote control, or a wireless remote control. Since its lights are fairly far from the model , its accuracy is quite good. The further the lights are from the model the more parallel are the light rays when they reach the model on the support table. The large size also allows the use of fairly large architectural models, and it allows many people to simultaneously observe the simulation. Sun Simulator heliodon

33. The Sun Emulator heliodon is an intuitive and conceptually clear heliodon . It is completely manufactured in a factory and only needs to be plugged in when it is unpacked. Its footprint is about 6 x 6 ft (2 x 2 m), and it can be rolled around on its own casters. The seven rings that represent the sunpaths for the 21st day of each of the months can be rotated to simulate the time of day. The cradle that supports the rings can be rotated 90 degrees to simulate all latitudes from the equator to the poles. The time of year is selected by a rotary switch with 12 positions for the 12 months. The three main advantages of the Sun Emulator are: -shipped completely assembled, -can simulate all latitudes, and -is small enough to fit through a standard door. When folded up, the heliodon requires little storage space of about 3 x 6 ft (1 x 2 m).. Sun Simulator heliodon

34. Solar radiation – The Source of never Ending Energy The complete concept of harnessing solar energy to generate electricity is based upon the phenomenon of solar radiation Direct Normal Irradiance (DNI)  is the amount of solar radiation received per unit area by a given surface that is always held perpendicular to the incoming rays. Components of Solar Radiation Direct Radiation  (the radiation which comes directly from the sun) Diffused Radiation  (the radiation which is diffused by the sky, layers of atmosphere and other surroundings) Reflected Radiation  (the radiation which is reflected back by the lake, seas and other water bodies)

35. The total ground reflection is a sum of all the above three components. Although the sun’s energy output is fairly constant, the total solar radiation falling on the earth’s surface varies and depends on a lot of factors Atmospheric Conditions  (Cloud Cover, Ozone layer condition, etc.) Earth’s Rotation  (time of the day, solar activity, etc.) Earth’s Revolution  (distance between earth and sun, seasons, angle of inclination of earth’s surface, etc.)

36. Global insolation Solar insolation is affected by factors such as atmosphere, angle of the sun and distance. The thinner the atmosphere in which the sun is passing through, the more the insolation. Insolation is also at its highest when the sun is directly overhead in an area. This is also the shortest distance between the sun and an area.  World insolation maps show the amount of solar insolation in a given area at a given time. 

37. Cosine law The intensity on a tilted surface equals the normal intensity times the cosine of the angle of incidence. Atmospheric depletion The absorption of radiation by ozone, vapors and dust particles. The lower the solar altitude angle, the longer path of radiation through the atmosphere

38. Both weather and climate are characterized by the certain variables known as climatic factors . Solar radiation Ambient temperature Air humidity Precipitation Wind Sky condition FACTORS AFFECTING CLIMATE

39. Solar radiation is the radiant energy received from the sun. It is the intensity of sunrays falling per unit time per unit area and is usually expressed in Watts per square meter (W/m 2 ). The radiation incident on a surface varies and it depends on Geographical location (latitude and longitude) Orientation Seasons Time of day Atmospheric conditions 1. SOLAR RADIATION EXAMPLE: BUILDING ON A SOUTH FACING SLOPE IN SHIMLA WILL RECEIVE MORE RADIATION COMPARED TO OTHER ORIENTATIONS Solar radiation on surfaces normal to suns' rays is higher than on horizontal surfaces EFFECT OF ORIENTATION

40. 1. SOLAR RADIATION

41. 1. SOLAR RADIATION

42. Solar radiation is the most important weather variable that determines whether a place experiences high temperatures or is predominantly cold. The instruments used for measuring of solar radiation are the pyranometer and the pyrheliometer . 1. SOLAR RADIATION

43. HOW TO MEASURE SUNSHINE DURATION? Sunshine recorder essentially consists of a glass sphere mounted in a spherical bowl and a metallic groove which holds a record card. Sun's rays are refracted and focused sharply on the record card beneath the glass sphere, leaving burnt marks on the card. As the sun traverses, continuous burnt marks will appear on the card. Observers can measure the sunshine duration based on the length of the burnt marks. SUNSHINE RECORDER

44. The sunshine meter consists of three sensors. When sunlight is detected by the sensor, it will be transformed into electricity. Solar radiation can be calculated based on the generated voltage. The front sensor measures global solar radiation and is not shaded and receives sunlight from all around. The middle sensors and the rear sensors are partly shaded to avoid direct sunshine for measurement of diffuse solar radiation SUNSHINE METER

45. The temperature of air in a shaded (but well ventilated) enclosure is known as the ambient temperature; it is generally expressed in degree Celsius (ºC). Temperature at a given site depends on wind as well as local factors such as shading, presence of water body, sunny condition, etc. Stevenson’s screen can measure ambient temperature. 2. AMBIENT TEMPERATURE

46. STEVENSON’S SCREEN The Stevenson Screen or thermometer screen is a standard shelter (from rain, snow and high winds, but also leaves and animals) for meteorological instruments, particularly  wet and dry bulb thermometers used to record  humidity  and  air temperature It is kept 1.25m above the ground by legs to avoid strong temperature gradients at  ground level , has louvered sides to encourage the free passage of air, and is painted white to reflect heat radiation, since what is measured is the temperature of the air in the shade, not of the sunshine.

47. Air humidity, which represents the amount of moisture present in the air, is usually expressed in terms of ‘relative humidity’. Relative humidity is defined as the ratio of the mass of water vapour in a certain volume of moist air at a given temperature, to the mass of water vapour in the same volume of saturated air at the same temperature ; it is normally expressed as a percentage. It varies considerably, tending to be the highest close to dawn when the air temperature is at its lowest, and decreasing as the air temperature rises. 3. AIR HUMIDITY

48. Precipitation includes water in all its forms rain, snow, hail or dew. It is usually measured in millimeters (mm) by using a rain gauge . 4.PRECIPITATION

49. The standard rain gauge instrument generally consists of a funnel connecting to a graduated cylinder which is marked in millimeters. It has an outer cylinder which is 20 cm in diameter and 50 cm tall. When the rainwater overflows the inner cylinder, the large outer cylinder holds it. The amount of water in the outer cylinder and the inner cylinder are taken for rainfall measurement. Rain gauges should be placed in an open area where there are no obstacles like buildings or trees to block the rain. This is also to prevent the water collected on the roofs of buildings or the leaves of trees from dripping into the rain gauge after a rain, resulting in inaccurate readings.   RAIN GAUGE

50. Wind is the movement of air due to a difference in atmospheric pressure, caused by differential heating of land and water mass on the earth’s surface by solar radiation and rotation of earth. WIND

51. Wind speed can be measured by an anemometer and is usually expressed in meters per second (m/s). It is a major design consideration because it affects indoor comfort conditions by influencing the convective heat exchanges of a building envelope, as well as causing air infiltration into the building WIND

52. An  anemometer  is an instrument that measures wind speed and wind pressure. The most common type of anemometer has three or four cups attached to horizontal arms. The arms are attached to a vertical rod. As the wind blows, the cups rotate, making the rod spin. The stronger the wind blows, the faster the rod spins. The anemometer counts the number of rotations, or turns, which is used to calculate wind speed. Because wind speeds are not consistent, wind speed is usually averaged over a short period of time.  Wind speed helps indicate a change in weather patterns, such as an approaching storm, which is important for pilots, engineers, and climatologists.  ANEMOMETER

53. Sky condition generally refers to the extent of cloud cover in the sky or the duration of sunshine. Under clear sky conditions, the intensity of solar radiation increases; whereas it reduces in monsoon due to cloud cover. SKY CONDITION

54. The re-radiation losses from the external surfaces of buildings increase when facing clear skies than covered skies. The measurement of sky cover is expressed in oktas . For example, 3 oktas means that 3/8 th of the visible sky is covered by clouds. SKY CONDITION