[Bldg-sim] Errors in TMY3 Files

Thu Dec 24 05:34:37 PST 2020

:-)

Presenting metadata or applying checksums would pick out arithmetic or unit errors like 
what happened in the original TMY3s, but better documentation of the data and their 
provenance is the key to making sense of a weather file.  This thread has been talking 
about mistakes in the TMY3s, but I give credit to NREL for developing the TMY2/TMY3 format 
that added flags to every data element and included the actual time stamp.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 12/24/2020 3:28 AM, Chris Yates wrote:
> Like glazing, I'm often a bit lost when it comes to rooting out the right weather file. 
> In one instance, this has even led to purchasing the same data twice from CIBSE!
>
> I've thought that either better presentation of metadata or applying checksums to 
> weather files could get around this.
>
> Chris
>
> On Tue, Dec 22, 2020 at 1:11 AM Joe Huang via Bldg-sim <bldg-sim at lists.onebuilding.org 
> <mailto:bldg-sim at lists.onebuilding.org>> wrote:
>
>     I forgot to mention as an aside I noticed that NREL had taken the (revised) TMY3
>     files offline several months ago.  However, these TMY3s in EPW and BINM formats are
>     still available on my Web site at weather.whiteboxtechnologies.com/TMY3
>     <http://weather.whiteboxtechnologies.com/TMY3>. I'm also in the process of adding
>     the *.CSV format to the files now that they're gone from the NREL Web site.
>
>     Joe
>
>     Joe Huang
>     White Box Technologies, Inc.
>     346 Rheem Blvd., Suite 205A
>     Moraga CA 94556
>     yjhuang at whiteboxtechnologies.com  <mailto:yjhuang at whiteboxtechnologies.com>
>     http://weather.whiteboxtechnologies.com  <http://weather.whiteboxtechnologies.com>  for simulation-ready weather data
>     (o) (925)388-0265
>     (c) (510)928-2683
>     "building energy simulations at your fingertips"
>
>     On 12/21/2020 3:55 PM, Joe Huang wrote:
>>
>>     Interesting to see my work described by someone who was never involved. The
>>     original driver for doing that work was to correct the decimal mistake in some of
>>     the illuminance data that NREL had noted in 2005 but never corrected because the
>>     original developers had retired. The reporting of precipitation was an additional
>>     improvement I offered to NREL, and actually ended up the lion's share of the work
>>     because it required reprocessing all the source weather files.  Neither of these
>>     corrections/improvements should affect any other weather set developed from
>>     scratch.  i have always been careful to not infringe on NREL's branding of TMY for
>>     a number of reasons, one of which has just been shown that all TMYs are assumed to
>>     be related.
>>
>>     Joe
>>
>>     Joe Huang
>>     White Box Technologies, Inc.
>>     346 Rheem Blvd., Suite 205A
>>     Moraga CA 94556
>>     yjhuang at whiteboxtechnologies.com  <mailto:yjhuang at whiteboxtechnologies.com>
>>     http://weather.whiteboxtechnologies.com  <http://weather.whiteboxtechnologies.com>  for simulation-ready weather data
>>     (o) (925)388-0265
>>     (c) (510)928-2683
>>     "building energy simulations at your fingertips"
>>     On 12/21/2020 3:04 PM, Linda Lawrie via Bldg-sim wrote:
>>>     the TMY3 files on climate.onebuilding.org <http://climate.onebuilding.org> have
>>>     been corrected from the document posted by Joe Huang on the tmy3 site.  But I
>>>     think that was for precipitation.
>>>
>>>     the TMYx files would never have had this problem as they come from a different
>>>     source of our creation for the TMYx files.
>>>
>>>     And, as I remember, the illuminance problem was corrected by NREL at some point
>>>     after their first post.
>>>
>>>     ------
>>>     Linda
>>>
>>>     FIBPSA, FASHRAE
>>>     http://climate.onebuilding.org <http://climate.onebuilding.org/> - free repository
>>>     of climate data for building simulation
>>>     Climate.onebuilding is a FREE service not supported by any outside organization or
>>>     government agency.
>>>
>>>
>>>
>>>>     Does anyone know if the errors described in TMY3 files in this post from Joe
>>>>     Huang on Jan 14 2015 still exist in files on the http://climate.onebuilding.org/
>>>>     <http://climate.onebuilding.org/> website? And were these errors also fixed in
>>>>     TMYx files?
>>>>
>>>>     Specifically I’m interested in this issue:
>>>>
>>>>
>>>>     1) Illuminance. The TMY3s contain values for Global Horizontal, Direct Normal,
>>>>     Diffuse
>>>>     Horizontal, and Zenith Illuminance that are calculated based on the sun position
>>>>     and solar
>>>>     radiation. Although the documentation states that the units are 100 lux for the first
>>>>     three illuminances, and 10 candela/m2 for the Zenith Illuminance, all the TMY3
>>>>     files used
>>>>     these units only for the period Jan. 2-31, and for the rest of the year used
>>>>     units of lux
>>>>     and candela/m2, respectively. NREL put out a notice in August 2008 (see the link
>>>>     listed
>>>>     earlier) informing users of this discrepancy and promising a corrected version
>>>>     that didn't
>>>>     make it out until now! In this revision, we've decided to keep the units in the
>>>>     original
>>>>     TMY3 documentation, i.e., 100 lux or 10 candela/m2, which is the same as what was
>>>>     in the
>>>>     TMY2, and avoids the superfluous five-digit precision.
>>>>
>>>>     If I use a TMY3 or TMYx file from the climate.onebuilding.org
>>>>     <http://climate.onebuilding.org> website, am I getting a TMY3 or TMYx version in
>>>>     which these issues are corrected?
>>>
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