'one sun' is 1000 W/m2
this 2013 graph of a seemingly clear blue sky day, may 31, from milford utah, note the peak is over 1000.
Solar irradiance - wiki - Irradiance on Earth's surface
"Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361 W/m2.[30] The Sun's rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000 W/m2 at sea level on a clear day. When 1361 W/m2 is arriving above the atmosphere (when the sun is at the zenith in a cloudless sky), direct sun is about 1050 W/m2, and global radiation on a horizontal surface at ground level is about 1120 W/m2.[31] The latter figure includes radiation scattered or reemitted by the atmosphere and surroundings. The actual figure varies with the Sun's angle and atmospheric circumstances. Ignoring clouds, the daily average insolation for the Earth is approximately 6 kWh/m2 = 21.6 MJ/m2."
this 2013 graph of a seemingly clear blue sky day, may 31, from milford utah, note the peak is over 1000.
Solar irradiance - wiki - Irradiance on Earth's surface
"Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361 W/m2.[30] The Sun's rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000 W/m2 at sea level on a clear day. When 1361 W/m2 is arriving above the atmosphere (when the sun is at the zenith in a cloudless sky), direct sun is about 1050 W/m2, and global radiation on a horizontal surface at ground level is about 1120 W/m2.[31] The latter figure includes radiation scattered or reemitted by the atmosphere and surroundings. The actual figure varies with the Sun's angle and atmospheric circumstances. Ignoring clouds, the daily average insolation for the Earth is approximately 6 kWh/m2 = 21.6 MJ/m2."
