[Bldg-sim] Wind driven rain data

Joe Huang yjhuang at whiteboxtechnologies.com
Wed Jul 18 18:55:02 PDT 2018


Roel,

I'm not an expert in this field of liquid precipitation, but here are my thoughts in 
response to your comments:

1) I'm not aware of drastic differences in rainfall between the airport and more urban 
areas of a city.  However, there are noticeable differences in wind speeds for which, in 
the absence of measured data, are accounted for in building energy modeling by 
TERRAIN-PARAMETERs dependent on the general site description, e.g., 1.00 for flat terrain 
such as an airport, 0.85 for rural, 0.67 for urban or forest, and 0.47 for urban centers 
with tall building, and the height difference between the measured data and the site.  if 
you're having difficulty in finding either measured wind speed or driving rain data (good 
luck!), I would suggest you just use the airport data and adjust that with a Terrain 
Parameter.

2) If you insist on getting rain and wind speed data for a suburban location, I'm sure 
those can be found among the 8,000+ weather stations for which I have hourly weather data, 
but the locations would be anywhere in the world.  Do you care where is the location?

3) The Met Eirerann paper describes a driving rain index, but does not provide the 
equation.  In thinking about it again (note that I've only thought about this after 
reading your original query), I think a plausible approach would be:

    a. find the approximate downward velocity of falling rain (a quick web search for "How 
fast do raindrops fall" gave the answer of 10 m/sec)

    b. divide that by the (adjusted) wind speed to get the fraction that would fall on a 
vertical surface, i.e., driving rain.

    c. multiply the "driving rain fraction" by the reported rain fall to get the amount of 
driving rain.

    c. use the wind direction to apportion the driving rain by the wall orientation.

It's still not clear to me what is the primary motivation for your investigation.  Is it 
to determine the amount of driving rain at a particular location or weather file?  to 
validate the method to calculate driving rain?  Or to just get a handle on how much 
driving rain is there ?

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 7/18/2018 5:43 AM, Roel Tersteeg wrote:
>
> Dear Joe and Luis,
>
> Thank you for your replies to my question and apologies for my very late reply to you 
> both. Unfortunately the data from official, synoptic weather stations is airfield data 
> and thus not applicable to my situation as there is no difference in microclimate (no 
> changes in wind or rainfall due to surrounding building). The same goes for the Met 
> Eireann information (if of interest, the Climatological notes 13 and 3 about wind driven 
> rain can also be found and downloaded here as well: 
> https://www.met.ie/education/publications/climatological-notes)
>
> I am looking specific for wind driven rain data, or indeed combined wind and 
> precipitation data that can be converted to wind driven rain, for different (sub)urban 
> settings. The suggestion for looking at ‘personal weather stations’ is very interesting, 
> although this has the issue of uncertainty about the quality of the measurements.
>
> Kind regards,
>
> Roel
>
> *From:*Luis Miguel Blanes Restoy <lmblanes at gmail.com>
> *Sent:* 06 July 2018 14:34
> *To:* Joe Huang <yjhuang at whiteboxtechnologies.com>
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Wind driven rain data
>
> Joe
>
> Try this link
>
> https://es.scribd.com/document/346851908/MET-Driving-Rain-Index-IRELAND#close_user_settings_menu
>
> Regards
>
> Luis
>
> On Thu 5 Jul 2018, 04:28 Joe Huang, <yjhuang at whiteboxtechnologies.com 
> <mailto:yjhuang at whiteboxtechnologies.com>> wrote:
>
>     Luis,
>
>     Thanks for the tip.  I went to the link, which by the way is for the Irish
>     Meteorological Service,  and read that it said, "The amount of rain received by a
>     wall correlates fairly well with the product of rainfall and the component of the
>     wind speed normal to the wall. This led Lacy and Shellard to propose the product of
>     the mean annual rainfall and the mean annual wind speed as a driving rain index
>     which is proportional to the total rainfall driven in one year on to a vertical
>     surface always facing the wind",  which is functionally quite close to what I was
>     envisioning, i.e., WDR = LP * f(wspd, wdir),  where LP is Liquid Precipitation or
>     Rainfall. However, when I clicked on the link to the actual paper cited,  the
>     Meteireann web site responded that "404: Page not found".  Therefore, I still don't
>     know the function that converts LP or rainfall to WDR.
>
>     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  for simulation-ready weather data
>
>     (o) (925)388-0265
>
>     (c) (510)928-2683
>
>     "building energy simulations at your fingertips"
>
>     On 7/4/2018 2:30 PM, Luis Miguel Blanes Restoy wrote:
>
>         Hi Roel and Joe
>
>         Did you look at available data from Met Eireann? There is a paper regarding WDR
>         index calculation method that may be of your interest. See below link.
>
>         https://www.met.ie/climate/what-we-measure/rainfall#
>         <https://www.met.ie/climate/what-we-measure/rainfall>
>
>         Regards
>
>         Luis
>
>         On Wed 4 Jul 2018, 22:12 Joe Huang via Bldg-sim, <bldg-sim at lists.onebuilding.org
>         <mailto:bldg-sim at lists.onebuilding.org>> wrote:
>
>             What is your definition for Wind-driven Rain?  Practically all weather
>             station reports, including official stations available in NOAA's ISD as well
>             as unofficial "Personal Weather Stations" hosted on WeatherUnderground,
>             contain information on liquid precipitation (LP), wind speed, and wind
>             direction.  Can the WDR be calculated from these standard parameters, maybe
>             as the LP * f(wspd, wdir) ?
>
>             Joe
>
>             On 7/4/2018 3:52 AM, Roel Tersteeg via Bldg-sim wrote:
>
>                 Dear all,
>
>                 For the verification of a model to estimate wind driven rain (WDR) I
>                 would like to use WDR data from different microclimates (rural,
>                 (sub)urban). I have access to several data sets of free field or
>                 airfield WDR measurements from different locations and the results from
>                 a measurement campaign in Vancouver. To better evaluate the model I
>                 would like to use measured data from one or more locations with
>                 different microclimates, not being free field or airfield sites.
>
>                 My question is if someone knows if measurements are available of wind
>                 driven rain in one or more microclimates?
>
>                 Kind regards,
>
>                 Roel Tersteeg MSc
>
>                 PhD-student
>
>                 Building Energy Research Group
>
>                 School of Architecture, Building and Civil Engineering
>
>                 Loughborough University
>
>                 T: +44 77 56 10 90 54
>
>                 E: R.M.Tersteeg at lboro.ac.uk <mailto:R.M.Tersteeg at lboro.ac.uk>
>
>             _______________________________________________
>             Bldg-sim mailing list
>             http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
>             To unsubscribe from this mailing list send  a blank message to
>             BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG
>             <mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20180718/5e6aa5ab/attachment-0002.html>


More information about the Bldg-sim mailing list