scientimate.windvelz1toz2#

Uz2_PowerLaw, Uz2_LogLaw, Uz2_LogLaw_Charnock = scientimate.windvelz1toz2(Uz1, z1, z2=10, alpha=1/7, z0=0.005, alpha_Charnock=0.0145)

Description#

Convert wind velocity from first height, z1 (m), to second height, z2 (m), (e.g. 10 (m)) above surface

Inputs#

Uz1

Wind velocity at z1 Height in (m/s)

z1

First Height (e.g. sensor height) in (m)

z2=10.0

Second Height that wind velocity is converted to in (m)

alpha=1/7
Exponent of power law velocity profile, Uz1/Uz2=(z1/z2)**(alpha)
water: alpha=1/11.5, open area: alpha=1/9.5, suburban area: alpha=1/7, urban area: alpha=1/5
z0=0.005
Surface roughness in logarithmic velocity profile in (m), U/Ustar=(1/0.41)*ln(z/z0)
water: z0=0.005 (m), open area: z0=0.02 (m), suburban area: z0=0.3 (m), urban area: z0=2 (m)
alpha_Charnock=0.0145
Charnock (1955) parameters to calculate ocean surface roughness, z0=alpha_Charnock*(Ustar^2/g)
Charnock (1955): alpha_Charnock=0.012, Garratt (1977): alpha_Charnock=0.0145, Wu (1980): alpha_Charnock=0.0185

Outputs#

Uz2_PowerLaw
Wind velocity at height of z2 above surface in (m/s)
calculated from power law velocity profile
Uz2_LogLaw
Wind velocity at height of z2 above surface in (m/s)
calculated from logarithmic velocity profile
Uz2_LogLaw_Charnock
Wind velocity at height of z2 above surface in (m/s)
calculated from logarithmic velocity profile
using Charnock (1955) relationship for wind over ocean

Examples#

import scientimate as sm
import numpy as np

Uz2_PowerLaw,Uz2_LogLaw,Uz2_LogLaw_Charnock=sm.windvelz1toz2(8,15,10)

Uz1=10.*np.random.rand(100)
Uz2_PowerLaw,Uz2_LogLaw,Uz2_LogLaw_Charnock=sm.windvelz1toz2(Uz1,15,10,1/7,0.005,0.0145)

References#

Charnock, H. (1955). Wind stress on a water surface. Quarterly Journal of the Royal Meteorological Society, 81(350), 639-640.

Garratt, J. R. (1977). Review of drag coefficients over oceans and continents. Monthly weather review, 105(7), 915-929.

Wu, J. (1980). Wind-stress coefficients over sea surface near neutral conditions—A revisit. Journal of Physical Oceanography, 10(5), 727-740.