wind.profile {bigleaf} | R Documentation |

## Wind Speed at a Given Height in the Surface Layer

### Description

Wind speed at a given height above the canopy estimated from single-level measurements of wind speed.

### Usage

```
wind.profile(
data,
z,
Tair = "Tair",
pressure = "pressure",
ustar = "ustar",
H = "H",
wind = "wind",
zr,
zh,
d = NULL,
frac_d = 0.7,
z0m = NULL,
frac_z0m = NULL,
estimate_z0m = TRUE,
stab_correction = TRUE,
stab_formulation = c("Dyer_1970", "Businger_1971"),
constants = bigleaf.constants()
)
```

### Arguments

`data` |
Data.frame or matrix containing all required variables |

`z` |
Height above ground for which wind speed is calculated. |

`Tair` |
Air temperature (deg C) |

`pressure` |
Atmospheric pressure (kPa) |

`ustar` |
Friction velocity (m s-1) |

`H` |
Sensible heat flux (W m-2) |

`wind` |
Wind speed at height zr (m s-1); only used if |

`zr` |
Instrument (reference) height (m) |

`zh` |
Canopy height (m) |

`d` |
Zero-plane displacement height (-) |

`frac_d` |
Fraction of displacement height on canopy height (-);
only used if |

`z0m` |
Roughness length (m), optional; only used if |

`frac_z0m` |
Fraction of roughness length on canopy height (-), optional; only used if |

`estimate_z0m` |
Should |

`stab_correction` |
Should stability correction be applied? Defaults to |

`stab_formulation` |
Stability correction function used (If |

`constants` |
k - von-Karman constant (-) |

### Details

The underlying assumption is the existence of a logarithmic wind profile above the height d + z0m (the height at which wind speed mathematically reaches zero according to the Monin-Obukhov similarity theory). In this case, the wind speed at a given height z is given by:

`u(z) = (ustar/k) * (ln((z - d) / z0m) - \psi{m}`

The roughness parameters zero-plane displacement height (d) and roughness length (z0m)
can be approximated from `roughness.parameters`

. `\psi{m}`

is omitted
if `stab_correction = FALSE`

(not recommended). If `estimate_z0m = TRUE`

,
z0m is first estimated from the wind profile equation and then used in the equation
above for the calculation of `u(z)`

(see e.g. Newman & Klein 2014).

### Value

A vector of wind speed at heights `z`

.

### Note

Note that this equation is only valid for z >= d + z0m, and it is not
meaningful to calculate values closely above d + z0m. All values in `heights`

smaller than d + z0m will return 0.

### References

Monteith, J.L., Unsworth, M.H., 2008: Principles of Environmental Physics. 3rd edition. Academic Press, London.

Newman, J.F., Klein, P.M., 2014: The impacts of atmospheric stability on the accuracy of wind speed extrapolation methods. Resources 3, 81-105.

### See Also

### Examples

```
heights <- seq(18,40,2) # heights above ground for which to calculate wind speed
df <- data.frame(Tair=25,pressure=100,wind=c(3,4,5),ustar=c(0.5,0.6,0.65),H=c(200,230,250))
ws <- sapply(heights,function(x) wind.profile(df,z=x,zr=40,zh=25,d=16))
colnames(ws) <- paste0(heights,"m")
```

*bigleaf*version 0.8.2 Index]