# Symbols

### Latin symbols

 empirical constants in [Best 1950] drop spectrum (eq. 2.24) [m] area [m] catchment area empirical constant in [Best 1950] drop spectrum (eq. 2.24) slope of the fit function , in correlation plots [-] mean pressure coefficient empirical constant in [Best 1950] drop spectrum (eq. 2.24) , , , parameters in a general formula for raindrop spectra (eq. 2.25) [-] drag coefficient [-] - model constant [-] - model constant [-] - model constant [m] displacement height [m] raindrop diameter [m] median median drop size (eq. 2.20) [-] roughness parameter (eq. 6.5) [-] fraction of liquid water in the air comprised by drops with diameters less than (eq. 2.19) [m s] gravitational acceleration [m] internal boundary layer height [m] building height; obstacle height [-] turbulence intensities [-] driving rain ratio (eq. 2.28) [-] von Kármán constant (0.4) [m s] turbulent kinetic energy per unit of mass [m] stopping distance [m] characteristic eddy dimension (section 2.2.3) [m] smaller of (two times building height) and (building width), section 2.1.4 [m] integral length scale [kg] mass [kg m m] raindrop mass concentration spectrum [m m] raindrop number concentration spectrum [m m] parameter in [Marshall and Palmer 1948] drop spectrum (eq. 2.21) [-] number empirical constant in [Best 1950] drop spectrum (eq. 2.24) correlation coefficient; the coefficient of determination is (eq. 3.4) [mm h] rain intensity, also expressed in [kg m s] = [mm s] [mm h] driving rain intensity [-] Reynolds number [s] time [s] averaging and summation period, the periods are synchronised to clock and calendar; the first period of a day starts at 00h00. [s] pause between rain spells [s] sample time [s] precipitation time [s] integral time (eq. 6.7) [m s] friction shear velocity [m s] wind velocity vector [m s] longitudinal, lateral and vertical wind velocity [m s] raindrop velocity vector [m s] raindrop velocity in , and direction [m s] wind speed [m s] horizontal wind speed [m s] horizontal wind speed at 10 m height on open terrain with = 0.03 m and = 0 m [m s] wind velocity components ( is due north, west, upwards) [m s] wind velocity vectors according to the anemometer axis system [ml] effective volume of a rain gauge bucket [m s] terminal drop speed [kg m] liquid water content (i.e. amount of liquid water per unit of air) [m] building width [m] position coordinates ( is upwards) -axis quantity and -axis quantity of the fit function , in correlation plots [m] roughness length

### Greek symbols

 coefficient in Lacy's formula 2.29 coefficient in model 2 (eq. 5.4) exponent in Lacy's formula 2.29 exponent in model 2 (eq. 5.4) constant in eq. 6.8 exponent in model 2 (eq. 5.4) [m s] dissipation rate of [-] catch ratio (eq. 2.26) [] constant in function (fig. 5.23) for model 2 (eq. 5.4) [] angle (in chapter 6) [-] obstruction factor, eq. 2.35 [m] parameter in [Marshall and Palmer 1948] drop spectrum (eq. 2.21) parameter in [Ulbrich 1983] drop spectrum (eq. 2.23) [kg m s] dynamic viscosity (1.6-1.8 10 kg m s for air), [m s] kinematic viscosity (1.3-1.5 10 m s for air), [m s] turbulent or eddy viscosity [-] constant in function (fig. 5.23) for model 2 (eq. 5.4) [kg m] density [-] - model constant [-] - model constant [N m] turbulent shear stress [N m] surface shear stress (eq. 2.2) [kg m s m] raindrop mass flux spectrum (definition of in eq. 2.16) [] horizontal wind direction, angle from which the wind blows, clock wise from north (e.g. 270 is wind from west)

### Subscripts

 5, 10, 60 clock period 5, 10 and 60 min respectively air corrected, esp. for rain intensity: rain intensity is obtained by combining data of a tipping-bucket rain gauge and a rain indicator (see section 3.4.3) raindrop estimate (eq. 3.4) at façade horizontal (at reference unless otherwise indicated) measurement (eq. 3.4) P1, P2, ... measurement positions reference uncorrected, esp. for rain intensity: rain intensity is obtained by simply counting the tippings of a tipping-bucket rain gauge (see section 3.4.3) vertical (at reference unless otherwise indicated)

### Operators

 mean of fluctuating component of ( ) standard deviation of for , and by for the other values of , where is limited to the interval 0-1 (fig. 5.23)

Subsections
© 2002 Fabien J.R. van Mook
ISBN 90-6814-569-X
Published as issue 69 in the Bouwstenen series of the Faculty of Architecture, Planning and Building of the Eindhoven University of Technology.