Apologies for the size of the attachment.
I'm looking for weather data for Beijing, and I see three weather files on the Energy plus site.
The first one is the CSWD (Chinese Standard Weather Data) source.
The second is the CTYW (Chinese Typical Year Weather) source
And the last is the SWERA (Solar & Wind Resource Assessment).
It seems like the first one has very strange solar radiation data - strange spikes that really look wrong. It also seems like the humidity numbers are too high - pretty much 100% most of the year.
The last two look more reasonable and are pretty similar (which would indicate that they are more reliable). However - they both show really low direct solar in the summer months (less than diffuse).
Has anyone had any experience with this? Which one should I use?
Vikram Sami, LEED AP
I hope the attachment goes through. It contains Beijing.bin (146 kb bin file converted from NCDC data year 2000) and Beijing.bin converted to Excel tables and charts (1.0 mb). It includes only 5% of the original 17 mb Excel tables and charts (6 mb zipped) in pdf.
Vikram,
I like your plots, but I have one suggestion - you should plot the total
and diffuse radiation as solid shades and the direct normal as the solid
line, since diffuse is always a subset of the total horizontal, while
the direct normal can be higher than either of the other two because of
the sun angles.
I helped in the creation of the CTYWs back about 14 years ago, and am
aware of the CSWD and SWERA efforts, but have not compared the three
sets in detail. I agree with you that the solar and humidity on the CSWD
look suspicious. Do the 3-4 months showing only a single temperature
line indicate that the wetbulb is identical with the drybulb, i.e., that
RH is at 100% for the whole month? That's hard to believe. Likewise, the
spikes in direct normal solar are no doubt a problem with the algorithm
used to distribute the measured daily to the hourly solar values.
The SWERA and CTYW both use similar raw data originally from the US
Climate Data Center. In both files, the solar is estimated using various
radiation models based on cloud cover and other climate parameters. When
"tuned" to measured data, these models have been found to be pretty
accurate on the aggregate, i.e., monthly or annual means, level, but can
be considerably off for any particular hour or day.
Joe Huang
Thanks Joe - this is good input. I didn't realize that you worked on this.
You're right - it does mean 100% humidity - which I think looks wrong.
Heres a view of the entire year from the CSWD file plotted over the entire year. That looks completely wrong to me. I think I'll stick with the CTYW or the SWERA.
[cid:image001.png at 01CB11FA.6037B1B0]
Vikram Sami, LEED AP