"Radiation approximation using the sun's azimuth angle and sunrise/sunset" to calculate ET doesn't make sense.
Solar Radiation is a crucial data to calculate ET, and radiation varies tremendously through the day depending on cloud cover and shades. WeeWX is actually capable of calculate the Theoretical Maximum Solar Radiation (maxSolarRad), but by using this data for ET calculation would be irrational. An approximation to convert Illuminance to Radiation - or vice-versa - by a multiple of ~120 is acceptable. So, the image underneath can be seen as a radiance example to compare measured vs theoretical. That is, the measured data rarely touches the theoretical. If ET of importance, then consider a PWS system that is capable of measuring radiance (there are some inexpensive systems available nowadays). X On Tuesday, November 19, 2019 at 12:01:33 AM UTC-5, Glen Napthali wrote: > > Hi, > I have been running weewx on a RPi with a fineoffset WH1080 for a year or > two. Recently I have thought it would be nice to calculate the daily ET to > help inform me about irrigation needs for my farm. The WH1080 doesn't have > a radiation monitor can an approximation be made using the sun's azimuth > angle and sunrise/sunset times? If possible how can it be done? > > -- 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/38fc9748-6643-4777-8e7e-6baf5d5bdf33%40googlegroups.com.
