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
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
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#
Regards
Luis
On Wed 4 Jul 2018, 22:12 Joe Huang via Bldg-sim, <
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
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
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,
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
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"
Hello,
FYI, I can think of at least one location where you'd find probably good
quality weather data in a *big urban center and not at an airport: Central
Park, New York City, USA*, though it's in a quite large park but there are
tall buildings all around it, see map
.
Note that in NOAA there's a weird thing going on where you have 4 stations
with different operating dates, one did 1943 to 2010, another 2010 to 2012
or so, and another started after that (I know I said there are four: one
did 17 days in august 2010 but overlapped another running one). Here are
the USAF-WBAN codes for the two most interesting:
725053-94728 #CENTRAL PARK (2012 to today)
725060-94728 #NEW YORK CENTRAL PARK (2010 to 2012)
This data is free and can be accessed at NOAA's ISD (see here
)
I looked at France's stations in the NOAA database too, since I have a
better clue of where things actually are, and it seems that there are a
bunch that aren't at an airport, but there are all in seaside towns, so
that is probably not what you're looking for...
Here are some stations you'll perhaps want to look at, I'm including the
three airports around central park too if you want to compare the data.
Don't mind the fact that the 'END" date is last year, I just haven't
refreshed this file since September 2017
USAF WBAN STATION NAME CTRY STATE ICAO LAT LON ELEV(M) BEGIN END KEEP
70020 99999 BOULOGNE FR 50.733 1.6 74 19730101 20170902 YES
72000 99999 PENMARCH FR 47.8 -4.367 19 19360102 20170902 YES
73150 99999 LA ROCHELLE FR 46.15 -1.15 10 19290801 20170902 YES
76410 99999 SETE FR 43.4 3.7 81 19360615 20170902 YES
76950 99999 CAP FERRAT FR 43.683 7.333 144 19730101 20100412 YES
725030 14732 LA GUARDIA AIRPORT US NY KLGA 40.779 -73.88 3.4 19730101
20170904 YES
725033 94728 NYC CENTRAL PARK US NY KNYC 40.779 -73.969 47.5 19431201
20100731 YES
725033 99999 NEW YORK CITY CENTRAL PARK US NY 40.767 -73.983 27 20100801
20100817 YES
725053 94728 CENTRAL PARK US NY KNYC 40.779 -73.969 42.7 20120801 20170904
YES
725060 94728 NEW YORK CENTRAL PARK US NY KNYC 40.779 -73.969 47.5 20100801
20120801 YES
744860 94789 JOHN F KENNEDY INTERNATIONAL AIRPORT US NY KJFK 40.639 -73.762
3.4 19730101 20170904 YES
Best,
Julien
--
Julien Marrec, EBCP, BPI MFBA
Owner at EffiBEM
T: +33 6 95 14 42 13
LinkedIn (en) *| *(fr
) :
2018-07-19 3:55 GMT+02:00 Joe Huang via Bldg-sim <
bldg-sim at lists.onebuilding.org>:
Dear Joe, Julien,
Thank you for the extensive replies and your suggestions.
The rainfall above an area is not very different between airfield and urban areas, but due to the buildings and trees that may shelter locations in build-up areas this can cause lower rainfall in those locations. As you mentioned the wind will be altered in a more significant way. One thing I would like to do is actually (re)define ?terrain parameters? for wind driven rain. A single number, such as in your example, hides the actual uncertainty behind that number. And for that I would like to find measured data, the location of which doesn?t matter that much.
The usage of weather stations for the purpose I am looking for is usually not an option as the location of weather stations is such that buildings and trees around the site don?t have an effect on the measurements (typically > 100 m around the site free of obstructions). For the model I am trying to build, the (uncertainty in the) effect of trees and buildings on rain and wind is exactly what I try to model. If you know of weather stations on such sites, I would be grateful if you could help me with that. I will also have a look at the weather stations in central park and see if they can help me.
As for the calculation presented, there are several methods (e.g. ISO15927, ASHRAE standard 55) and they mostly have the form of Rainfall*Wind_speed*cos(Wind_direction-Wall_normal), with possibly some factors. There is a bit more explanation in Climatological note 3 from Met Eireann, from which note 13 is an update, how they calculated the map.
As a site-note: the velocity of raindrops is dependent on the size of the droplet with larger drops having a higher speed (terminal velocity) that smaller ones.
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
Roel,
I have the following concerns about the approach you seem to be taking
to define terrain-parameters for wind-driven rain:
(1) you are still basing your investigation on a rather simplistic model
to derive wind-driven rain from the reported rain fall and wind speed,
i.e., do you know how reliable is that model?
(2) for these types of correlations, you might want to use wind speeds
at a much finer time resolution, since what's reported at the standard
weather stations are random snapshots at an hourly or half-hourly time
step.? You could consider using data from Personal Weather Stations
(PWS), that are typically at the 5 minute interval and many also have an
additional channel for gusts.? Such weather data, i.e., 5-minute data in
urban or suburban areas, are currently available for tens of thousands
of PWS, especially in North America and the UK, on web sites such as
Weather Underground (www.wunderground.com). One caveat would be to know
the placement of the PWS, which tend to be on rooftops (the problem is
worse for official weather stations that are supposed to be at 10 m
above the ground).?? If you're interested in the WU weather data, let me
know via e-mail.
I would not recommend using New York Central Park, or at least you
should compare the results to that from some other place that's less
atypical.?? The Central Park? weather station? is located at the
Belvedere (see attached map), which is an isolated building in the
middle of a large urban park that is in turn surrounded by tall
buildings and adjacent to some of the tallest buildings in the world.
Yes, I'm aware that the terminal velocity of raindrops varies with their
size.? However, I ignored that factor because any error due to using a
constant value would be small compared to all the other assumptions of
the model and besides, I don't think raindrop size is recorded in any
weather data.
Joe
BLDG-SIM had said this post was too large, so I'm resending it with the
picture size reduced.
Dear Joe,
Thanks again for taking the time to respond, it is much appreciated.
I would like to address your concerns, which I think evolve around the potential usage of the model I try to build. I am looking at the early design stages of buildings, when little is known and (long-term) local measurements are not available. In that case the dimensions/exact shape of the building are not known, but the risk of WDR might still be relevant. It is trying to find the balance between an easy to use model with limited input and higher accuracy with more input.
The reason to use (hourly) synoptic weather station data is that the quality of this data is checked and readily available. 5 or 10 minute data would indeed increase the accuracy of a model and the option of weather underground or the UK Met Office's WOW network (this was mentioned to me a couple of weeks ago by Matt Clark - Met Office) is interesting, but there is the uncertainty of the data quality and the caveat you mentioned.
And it is true that the drop size in not usually recorded, as far as I know few instruments exist that can do that accurately. I have seen some recent papers that try to address this, but apart from a few experiments I haven't seen widescale use. In the past there have been a few papers that describe the velocity and distribution of raindrops (Gunn and Kinzer, 1949; Best, 1950; Atlas et al., 1973+1977; Adirosi et al., 2016)
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
Roel