dash.localize.gc2d
Computes localization weights using a Gaspari-Cohn 5th order polynomial in 2 dimensions
Syntax
Description
Calculates covariance localization weights for an assimilation using a specified cutoff radius. The method proceeds by using a haversine function to dtermine the distances between 1. proxy sites and state vector elements, and 2. proxy sites with one another. Then, covariance localization weights are calculated by applying a 5th order, Gaspari-Cohn polynomial in 2 dimensions to the distances. If the distance between two points is NaN, returns a weight of 1 (i.e. no localization).
Also specifies the length scale for the polynomial. By default, uses a length scale of 0.5, which sets the localization radius equal to the cutoff radius.
Input Arguments
stateCoordinates
numeric matrix [nState x 2]
The coordinates of the state vector elements (in decimal degrees). A matrix with two columns. The first column holds the latitude points, and the second column holds longitude. The method is agnostic to longitudes on -180:180 and 0:360 coordinates systems, so you may use either system or even a mix of both.
siteCoordinates
numeric matrix [nSite x 2]
The coordinates of the proxy / observation sites (in decimal degrees). A matrix with two columns. The first column holds the latitude points, and the second column holds longitude. The method is agnostic to longitudes on -180:180 and 0:360 coordinates systems, so you may use either system or even a mix of both.
R
positive numeric scalar
The localization radius (in kilometers).
scale
numeric scalar
The length scale to use for the Gaspari-Cohn polynomial. Must be on the interval 0 < scale <= 0.5. By default, uses a length scale of 0.5, which sets the localization radius equal to the cutoff radius.
Output Arguments
wloc
numeric matrix [nState x nSite]
The covariance localization weights between the state vector elements and proxyobservation sites.
yloc
numeric matrix [nSite x nSite]
The covariance localization weights between the proxy/observation sites and one another.