Overview
Gaisma website provides sunrise, sunset, dusk and dawn times for thousands of locations all over the world. Sun data is shown in table format for selected dates and as a graph for the whole year. Possible daylight saving times are taken in the account.
Solar Insolation data is useful for sizing solar arrays, controllers and batteries. Solar insolation, as presented in the data, includes average environmental and weather conditions for certain geographic locations. The units of solar insolation are kWh/m²/day. This means that in one 24 hour period, an area of one meter on each side (one square meter is 10.764 square feet) has the amount of solar energy in kilowatt-hours shown in the table, on the average. A solar array and battery reserve can be adequately sized for 24/7/365 radio operation by using the lowest insolation number of the year, usually in December for the northern hemisphere. The data does not include energy conversion efficiency of devices, so the losses encountered in energy conversion will need to be accounted for. The data also does not include local effects such as shading by trees, rain, or snow, etc. It is best to test a potential location by placing a sample solar array, controller, battery, constant load, and recording instrument to verify the available energy.
What does "Gaisma" mean?
"Gaisma" is a Latvian word, meaning "light".
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.