Description Usage Arguments Details Value References

View source: R/wind_conversions.R

Converts maximum 10-m 1-minute symmetric sustained wind speed to gradient wind speed. The conversion factor depends on whether the storm is over land or water.

1 | ```
calc_gradient_speed(vmax_sfc_sym, over_land)
``` |

`vmax_sfc_sym` |
A numeric vector of 1-minute sustained wind speed at 10 meters, with motion asymmetry removed (m / s). |

`over_land` |
TRUE / FALSE of whether the storm is over land (TRUE) or water (FALSE). |

This function uses the following conversion:

*
Vmax,G = Vmax,sym / fr*

where:

*Vmax,G*: Max gradient-level 1-min sustained wind (m / s)*Vmax,sym*: Max 10-m 1-min sustained wind with motion asymmetry removed (m / s)*fr*: Reduction factor (see below)

The function uses a reduction factor based on Figure 3 in Knaff et al., 2011.
If over water and within 100 kilometers of the storm's center,
the ratio of gradient wind speed to surface wind speed is
assumed to be 0.90. If over land, this reduction factor is reduced
by 20% (*0.9 * 0.8 = 0.72*).

For this calculation, we assume
that the radius of
maximum wind for all storms is 100 kilometers or smaller (in the code,
we do not calculate *R_max* until after we estimate
gradient wind speed from surface wind speed, so we don't have that
storm-specific estimate to use here).

A numeric vector with maximum gradient-level 1-min wind speed (m / s).

Knaff JA, DeMaria M, Molenar DA, Sampson CR, and Seybold MG. 2011. An automated, objective, multiple-satellite-platform tropical cyclone surface wind speed analysis. Journal of Applied Meteorology and Climatology 50(10):2149-2166

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