All,

We were looking at weather data files for Sydney Australia,
(Sydney.Airport.947670), and we found that there is a of about an hour for
some of the data in AUS_NSW.Mascot-Sydney.Airport.947670_RMY versus
AUS_NSW.Sydney.947670_IWEC.

Please see the attached jpg. Looking at the direct normal radiation and
radiation-rose you can see that sun-rise and sun-set in RMY file happening
earlier. When combined with solar position calculations based location and
time this makes the sky to appear to be skewed, with more radiation from
the east. We found a similar pattern in AUS_NSW.Sydney.947680_RMY weather
file.

Which weather file is the one that you suggest us to use for the analysis?

Is there a known difference between the RMY and IEWC standard that would
account for this?

Is it because Sydney is near the eastern edge of its time zone, and the RMY
standard is defined in terms of actual local time rather than ?solar time?
and the IEWC standard were defined in terms of solar time rather than local
time?

Regards,

Mostapha

PS: I uploaded the jpeg file here because the list does not allow sending
me the email with the attachments (>200k): (
https://dl.dropbox.com/u/16228160/Sydney_Weather_Data_Comparision.jpg)