A real world demonstration of cloud controlling radiation
The original text struck me as inappropriate so I’ve edited it. I put it down to being overtired. The original is archived if anyone wants to see it, just ask (there is a contact form), no questions asked on why.
This is a huge plot including hourly data from WMO3768 Farnborough, England, a synoptic Met Office station where I estimate the site meets WMO 2010 recommendation Class 1, although the presence of a triangular airfield runway layout surrounding the station will have some side effects.
A details view of the plot is only practical via PDF (201kB) Very likely the PDF will open looking as above so you need to set magnification and scroll around the plot, 100% is the intended view. Some details of interest are reproduced below at a normal scale.
This extract is labelled with the features.
Automatic equipment at the site allows deduction of the weather conditions, not ideal but seems to be sufficient to illustrate how cloud clamps temperature. Visibility data is horizontal and does not follow presence of cloud, can be very clear at the same time as 8 oktars. Cloud thickness is not given so the whole thing is the best I can do within real limitations.
The missing data was data failure for all Datapoint sites, unfortunately for a few hours during the coldest part of the coldest night so far. Outages occur every day at one site or another.
Third and Fourth of November was a descent into winter cold, were several of these step downs
Curiously one month earlier there was another.
The weather can be followed on the EUMETSAT weather videos where they are available, daytime only. Yes it tallies.
Maybe to people in other parts of the world the lack of “good” weather: don’t you get sunshine? will make this look dismal. It is, English weather, why we obsess. Clear sunny days are rare, probably <1%
Insolation. This is probably the first time you have seen a computed hourly plot with met station data for a specific ordinary weather station location. The plots shows this from July when insolation is already falling through to winter. Note that not only is insolation value dropping, sun angle and long atmospheric path length but more subtly the day length is shortening, a clear 24 hours is able to radiate more out to space than is received.
I’ve decided to stop there instead of going into annual insolation shape and temperature dataset shape, don’t match, more than sun is controlling things.
I’ve not provided data, lot of it, if you need it ask and we can discuss what is practical.
Post by Tim