[esp-r] Re: customizing climate data sets

[Crawley, Drury]

When working on evaluating a 75-story tower, e found that there could be significant variation in temperature and wind speed with multistory buildings. Looking into the literature, we found that we could calculate outdoor air temperature variation using the U.S. Standard Atmosphere (1976). According to this model, the relationship between air temperature and altitude in a given layer of the atmosphere is:

Tz = Tb + L ( Hz − Hb )

where
Tz = air temperature at altitude z
Tb = air temperature at the base of the layer, i.e., ground level for the troposphere
L = air temperature gradient, equal to –0.0065 K/m in the troposphere
Hb = offset equal to zero for the troposphere
Hz = geopotential altitude, defined by:

Hz = Ez / (E + z)

where
E = 6,356 km, the radius of the Earth
z = altitude.

For the purpose of modeling buildings in the troposphere, altitude z refers to the height above ground level, not the height above sea level. The height above ground is calculated as the height of the centroid, or area-weighted center point, for each zone and surface.
The air temperature at ground level, Tb, is derived from the weather file air temperature by inverting the equation above:

Tb = Tz,met - L ((Ezmet / (E + Zmet)) - Hb)

where
Tz,met = weather file air temperature (measured at the meteorological station)
zmet = height above ground of the air temperature sensor at the meteorological station.
The default value for zmet for air temperature measurement is 1.5 m above ground. 

Similarly, the relationship between wind speed and altitude (i.e., height above ground) is described in Chapter 16 of the Handbook of Fundamentals (ASHRAE 2005). The wind speed measured at a meteorological station is extrapolated to other altitudes with the equation:

Vz = Vmet ( δmet / Zmet ) ^αmet * ( Z / δ ) ^α

where
z = altitude, height above ground
Vz = wind speed at altitude z
α = wind speed profile exponent at the site
δ = wind speed profile boundary layer thickness at the site
zmet = height above ground of the wind speed sensor at the meteorological station
Vmet = wind speed measured at the meteorological station
αmet = wind speed profile exponent at the meteorological station
δmet = wind speed profile boundary layer thickness at the meteorological station.

The wind speed profile coefficients α, δ, αmet, and δmet, are variables that depend on the roughness characteristics of the surrounding terrain. Typical values for α and δ are shown in the following:

Wind Speed Profile Coefficients (ASHRAE Fundamentals 2005).
Terrain Description		Exponent, α		Boundary Layer Thickness, δ (m)
Flat, open country 		0.14 			270
Rough, wooded country 		0.22 			370
Towns and cities 			0.33 			460
Ocean 				0.10 			210
Urban, industrial, forest 	0.22 			370

The default value for zmet for wind speed measurement is 10 m above ground. The default
values for αmet and δmet are 0.14 and 270 m, respectively, because most meteorological
stations are located in an open field.


-----Original Message-----
From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Geissler Achim
Sent: Tuesday, March 18, 2008 12:22 PM
To: vincent lacour; esp-r at lists.strath.ac.uk
Subject: [esp-r] Re: customizing climate data sets

Hi Vincent,
air pressure: That is not important, as ESP-r uses a constant total pressure (hard-coded).
For temperatures, maybe, "Standard ICAO atmosphere", approx. 0.8 K / 100 m, as far as I recall.
For wind? Difficult. As wind speed is measured 10 m above grade, I would leave it as it is and check sensitivity at some stage. 
Mit freundlichen Grüssen / Best regards

Achim Geissler

> -----Original Message-----
> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r- 
> bounces at lists.strath.ac.uk] On Behalf Of vincent lacour
> Sent: Tuesday, March 18, 2008 10:44 AM
> To: esp-r at lists.strath.ac.uk
> Subject: [esp-r] Re: customizing climate data sets
> 
> Dr.QIU wrote :
> > vincent lacour,ÄúºÃ£¡
> >
> > 	it seems you should modify some data in "model context"-->"site
> data"
> > Qiu
> >
> > ======= 2008-03-18 01:04:12 ÄúÔÚÀ´ÐÅÖÐдµÀ£º=======
> >
> >> I got from DOE the climate set for a location very close to my 
> >> project,
> BUT my project is located at a much higher
> >> elevation (950 m above mean sea level vs. 200 m amsl for the 
> >> climate
> data set).  any idea how i could reasonably adjust
> >> the climate data set for my project location?
> >>
> >> Regards
> >>
> >> Vincent
> >>
> >>
> >> _______________________________________________
> >> esp-r mailing list
> >> esp-r at lists.strath.ac.uk
> >> http://lists.strath.ac.uk/mailman/listinfo/esp-r
> >
> > = = = = = = = = = = = = = = = = = = = =
> >
> >
> > ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡ÖÂ
> > Àñ£¡
> >
> >
> > ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡Dr.QIU
> > ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡zhongqiu at cityu.edu.hk
> > ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡2008-03-18
> >
> Thanks Qiu for your reply; however "model context"-->"site data" 
> includes latitude and longitude but it does not include elevation.
> The point is: a) how to adjust climate data for temperature?  should I 
> use the 2 degrees / 305 meters ratio across the board?
> b) What about air pressure and its decreasing with elevation?
> 
> Vincent
> 
> 
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