How to read the graphs?

The chart below shows location's sunrise, sunset, dawn and dusk times for the whole year. Start of dawn and end of dusk times are based on the definition of "civil twilight".

  1. Months (notation can be changed in preferences)
  2. Time (24-hour clock, e.g. 7 = 7:00 am, 12 = 12:00 noon, 17 = 5:00 pm)
  3. "Today"
  4. Darkness
  5. Dawn
  6. Sunshine
  7. Dusk
  8. Possible Daylight Saving Time starts/ends

E.g. on the marked day (3) in Tampere, Finland dawn begins at 04:43, the sun rises at 05:37 and sets at 21:20. Dusk ends and the darkness begins at 22:14.

Sun path diagram (also known as "solar path diagram", "sun chart" or "solar chart") is a visualization of the sun's path through the sky. This path is formed by plotting azimuth (left-right) and elevation (up-down) angles of the sun in a given day to a diagram.

To find out the position azimuth = 60, elevation = 30, for example, imagine standing at the center of the diagram heading to the true north. To find the azimuth angle 60, you must turn 60 degrees to the right. Now the altitude angle 30 can be located by raising your head 30 degrees from the horizon.

  1. Azimuth angle
  2. Elevation angle
  3. Sun's path today
  4. Sun's path on the 21st June
  5. Sun's path on the 21st December
  6. Sun's path during the equinox
  7. Sunrise
  8. Sunset
  9. Horizon

It can be seen from the diagram (3. "Sun's path today") that the sun rises from the North-East (azimuth = 60) in Tampere at 05:37. Sunset happens at 21:20 when the sun is in the North-West (azimuth = 300). On that day the elevation angle is approximately 40 degrees at noon.

Solar energy and surface meteorology

Insolation

The monthly average amount of the total solar radiation incident on a horizontal surface at the surface of the earth for a given month, averaged for that month over the 22-year period (Jul 1983 - Jun 2005). Each monthly averaged value is evaluated as the numerical average of 3-hourly values for the given month. Source: NASA Langley Research Center Atmospheric Science Data Center.

Clearness

The monthly average amount of the total solar radiation incident on a horizontal surface at the surface of the earth divided by the monthly average incoming top-of-atmosphere insolation for a given month, averaged for that month over the 22-year period (Jul 1983 - Jun 2005); (i.e. clearness index is the fraction of insolation at the top of the atmosphere which reaches the surface of the earth). 0 = very overcast and 1 = sunny. Source: NASA Langley Research Center Atmospheric Science Data Center.

Temperature

The monthly average air temperature for a given month, averaged for that month over the 22-year period (Jan 1983 - Dec 2004). Temperature values are for 10 meters above the surface of the earth. Each monthly averaged value is evaluated as the numerical average of 3-hourly values for the given month. Source: NASA Langley Research Center Atmospheric Science Data Center.

Wind speed

The monthly average wind speed for a given month, averaged for that month over the 10-year period (July 1983 - June 1993). Wind speed values are for 50 meters above the surface of the earth. Each monthly averaged value is evaluated as the numerical average of 3-hourly values for the given month. Source: NASA Langley Research Center Atmospheric Science Data Center.

Precipitation

The monthly average precipitation for a given month, averaged for that month over the period from 1961 to 1990. Source: New, M., Lister, D., Hulme, M. and Makin, I., 2002: A high-resolution data set of surface climate over global land areas. Climate Research 21.

Wet days

Number of days per month with precipitation >0.1 mm. Averaged over the period from 1961 to 1990. Source: New, M., Lister, D., Hulme, M. and Makin, I., 2002: A high-resolution data set of surface climate over global land areas. Climate Research 21.