The WMO definition (threshold at 120 W/m2) is applicable only for the measurements of direct solar irradiance, using pyrheliometric sensors that are all the day moving to point always directly toward the sun position, with the surface of the sensor always perpendicular to the axis sun-sensor.
Pyrometer sensors, such as the Davis radiation sensor, are measuring mostly global irradiance. These sensors are not moving to follow the sun, and the surface of the sensor is parallel to the ground. And not pointed toward the sun With this type of sensors, the measured radiation ( even in absence of clouds) is highly dependent on the sun elevation. see https://library.wmo.int/viewer/68695/?offset=#page=333&viewer=picture&o=bookmark&n=0&q= > Le 3 mai 2024 à 16:59, [email protected] <[email protected]> a écrit : > > So, according to the WHO definition, days 26 and 27 were also days of full > sunlight. That's bogus. Yet, For Phoenix boosterism, they can claim even the > days 26 and 27 as days of sunshine. > > In fact, even during the months of July and August, when we enter the > monsoon, with full overcast and infrequent rain, rarely does the sensor drop > below 200 w/m^2. Only when a T-storm cell passes directly over the station > does it fall to 100 w/m^2 or less. -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/weewx-user/44E9AAA1-7ACE-455D-B178-E84EEF2109C3%40gmail.com.
