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I don't know if we have a thread on this already, I think we do, but I think for our newer posters on here it might help if we can educate them on the discrepancies between US sunshine hour measurements compared to the rest of the world. I don't know the exact details myself, all I do know is the US hours are overestimated significantly, by about 300 hours annually. So, what are the exact details and why are they not as reliable as the others? Why pick the others over the NOAA measurements, etc.
*Nei or Rozenn, if a thread like this exists already, maybe this can be merged and the old topic can be bumped up?
I don't know if we have a thread on this already, I think we do, but I think for our newer posters on here it might help if we can educate them on the discrepancies between US sunshine hour measurements compared to the rest of the world. I don't know the exact details myself, all I do know is the US hours are overestimated significantly, by about 300 hours annually. So, what are the exact details and why are they not as reliable as the others? Why pick the others over the NOAA measurements, etc.
*Nei or Rozenn, if a thread like this exists already, maybe this can be merged and the old topic can be bumped up?
lol, sounds like the topic for a college research project.
I think the difference is somewhere between 200 to 300+ depending on the type of climate. Boston is actually more than 300 hours difference as we have both methods available there, and the long term average for Boston is around 2250 hours, much less than the 2600 hours from NOAA.
If we're deducting hours from the US method to bring them in line with the rest of the world then I suppose something like 10% off across the board would be better than just taking off 200-300 no matter whether we're talking about Yuma or Seattle.
If we're deducting hours from the US method to bring them in line with the rest of the world then I suppose something like 10% off across the board would be better than just taking off 200-300 no matter whether we're talking about Yuma or Seattle.
I would be very surprised if San Diego or Miami were under 3000 hours if measured according to international standards.
It may be that the threshold for "bright sunshine" is lower in the US. In that case hazy high cloud could register as bright sunshine. Climates which experience such conditions more frequently would thus have their sunshine figures overstated to a greater extent than others. So it may not be fair to deduct a fixed percentage or number of hours from all cities.
I imagine the distinction between sunny and non-sunny conditions is much more clear cut in climates like Miami and San Diego since it's probably either sunny and dry or overcast with rain in those climates with little in between (although coastal fog in CA complicates matters). But in more northern climates intermediate conditions may be far more frequent. Hence, a 15% deduction may be warranted in the case of Vancouver, Detroit, Boston, etc. but not for Miami, Orlando and Los Angeles.
We can get some idea by examining sunshine figures for nearby climates in other countries. In the case of Miami we have Nassau with 2900 hrs and Havana with 3000. For San Diego nearby Tijuana claims 3000 hrs. So I don't think they're overstated by much.
I would be very surprised if San Diego or Miami were under 3000 hours if measured according to international standards.
It may be that the threshold for "bright sunshine" is lower in the US. In that case hazy high cloud could register as bright sunshine. Climates which experience such conditions more frequently would thus have their sunshine figures overstated to a greater extent than others. So it may not be fair to deduct a fixed percentage or number of hours from all cities.
I imagine the distinction between sunny and non-sunny conditions is much more clear cut in climates like Miami and San Diego since it's probably either sunny and dry or overcast with rain in those climates with little in between (although coastal fog in CA complicates matters). But in more northern climates intermediate conditions may be far more frequent. Hence, a 15% deduction may be warranted in the case of Vancouver, Detroit, Boston, etc. but not for Miami, Orlando and Los Angeles.
We can get some idea by examining sunshine figures for nearby climates in other countries. In the case of Miami we have Nassau with 2900 hrs and Havana with 3000. For San Diego nearby Tijuana claims 3000 hrs. So I don't think they're overstated by much.
From the "EducaPlus" site I see 2790 for Havana and 2838 for Nassau, so I think some significant reduction is probably needed for Miami. Not so sure about San Diego.
How does one go from solar radiation data to sunshine hours? I got hourly sunshine data for two stations (both in NY State). Can one just add up the number of hours above 120 W/m^2? Or do I need to know more details about the recorder?
I know nothing about this topic, but 300 hours is a lot, I have a hard time believing the difference is that much, when is all this extra sunshine being recorded?
Last edited by Infamous92; 07-02-2013 at 11:23 AM..
Reason: Spelling error.
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