Dynamic Wind Adjustment

Description

Adjust a wind component for the fall of a sonde (dropsonde only).

The wind component series is first smoothed, and then a time tendency is computed for each data point. The observation is then adjusted according to the formula, using the previously calculated vertical velocity.

Formula

Basic correction

At each point in the U and V wind component series $w_{adj}(w_{orig}, dz, wavelength)$ is calculated as:

$w_{adj} = w_{orig} - \frac{dw_{orig} \times dz}{g}\\$ where:
$dw_{orig}$ is the first derivative of a Bspline fit of the wind component series using the given $wavelength$ (Aspen config parameter WindDynCorWL).

Blending interval near surface

In the last 4 seconds of a sounding, the blending interval is shortened to prevent oversmoothing of valuable wind data near the surface. For points within this interval, two separate corrected wind values are calculated: one using $dw_{orig}$ from the Bspline calculated with wavelength WindDynCorWL, the other using $dw_{orig}$ from a Bspline calculated with a wavelength of 4.0 seconds. The two corrections are then blended together:
$w_{final} = factor \times w_{adj} + (1 - factor) \times w_{blend}\\$ where $factor = \frac{endTime - currTime}{4.0}$

Source