| libmf.gex - Mike Fiorino`s Collection of GrADS Extensions |
libmf.gex - Mike Fiorino`s Collection of GrADS Extensions
tcprop EXPR LON LAT RADIUS - Properties relative to lon/lat
mfhilo EXPR [METHOD[,OPTIONS] - Find max/min or H/L in 2D field
smth2d(EXPR[,N,nu1,...,nuN]) - Shuman smoother/de-smoother
uv2trw(U,V,[OPT],[LON,LAT]) - Find radial/tangential velocity
This library implements Mike Fiorino`s collection GrADS extensions, including his classic regrid2 regridding function as an extension now called re2, smth2d for applying the Shuman smoother-desmother and computing radial/tangential velocities relative to a lat/lon point. Commands are also provided to find H/L of a 2D field and to calculate properties of a tropical cyclone (TC).
These functions were initially developed as classic User Defined Function (UDFs) in GrADS v1.x. These extensions were later implemented as dynamic linked extensions in GrADS v1.10.
This command computes the EXPR properties relative to a point located at LON,LAT, typically a tropical cyclone. The parameters are returned to the calling GrADS script via script variable result.
Sample output:
tcprop for expr: psl Latc: 16.80 Lonc: 129.70 Radinf: 200 [nm] Bearing: 60 Hemi1: 60-240 Hemi2: 240-420 MAXCntRadGrad: 1.249e-02 minCntRadGrad: 8.694e-03 MeanCntRadGrad: 1.063e-02 [units: (out-ctr)/nm] MeanFieldInsideRadinf: 100573 Hemi1: 60-240 Hemi2: 240-420 MeanHemi1: 100572 MeanHemi2: 100573 QuadNE: 60-150 QuadSE: 150-240 QuadSW: 240-330 QuadNW: 330-420 MeanNE: 100598 MeanSE: 100545 MeanSW: 100548 MeanNW: 100597
EXPR - a valid GrADS expression
LON,LAT - longitude/latitude of the center
RADIUS - distance in nm away from LON,LAT to calculate properties
BEARING - direction (0-360 deg) to calculate mean of the field within
RADIUS in four quadrants and two hemispheres, e.g., of a TC is
heading towards the West (270 deg), then MeanHemi1 will be the right
hemisphere (North or right of track) and MeanHemi2 the left (South or
left of the motion). The quadrants are defined NE,SE,SW,NW relative to
BEARING (0 deg or North)
This command finds maximun/minimum values in a 2-D lat/lon field, returning the location and value between grid points via the GrADS script variable result.
EXPR is a GrADS valid expression
METHOD - can be either CL or GR
For method CL -- Contour-Level based from NCEP -- the OPTIONS are
MaXMin - specify L for lows only, H for highs only; A|B for both (case insensitive)
RADIUS - radius in nm, default is 120, bigger radius leads to finding fewer H/L
CINTINF - contour interval between max and nearby point; smaller contour interval leads to finding more negative extrema.
For method GR -- GRid-based written by Mike Firoino -- the OPTIONS are
MaXMin - specify L for lows only, H for highs only; A|B for both (case insensitive)
SORTby - d distance from either center of grid or a specified lat/lon; m order by mag/value at extrema; g by gradient; l by laplacian
PCNTILE - set percentile (0-100) of top N points sorted by gradient
LATC - set the latitude for distance [nm] calculations
LONC - set the longitude (deg E) for distance [nm] calculations
sExample + output:
vt=hcurl(u,v)*1e5
mfhilo vt gr b d 30 16.8 129.7
output in script variable result:
mfhilo GR method N: 7 maxmin: 0 pcntile: 30 latc: 16.80 lonc: 129.70 H 16.86 129.90 M: 20.3321 G: 100.0 L: 100.0 D: 12.22 GV: 2.2897 LV: 4.82068 H 17.03 127.69 M: 10.4799 G: 38.7 L: 28.8 D: 115.96 GV: 0.88574 LV: 1.38745 L 20.56 129.96 M: -5.2466 G: 100.0 L: 100.0 D: 226.19 GV: 1.09352 LV: 4.55874 L 17.94 125.36 M: -0.435871 G: 43.6 L: 23.0 D: 257.63 GV: 0.47636 LV: 1.04821 L 18.10 134.23 M: 0.00436844 G: 60.2 L: 25.6 D: 270.80 GV: 0.658458 LV: 1.16751 L 16.06 124.95 M: -0.726843 G: 26.8 L: 32.2 D: 276.80 GV: 0.293564 LV: 1.46846 L 14.40 134.67 M: -5.43262 G: 88.4 L: 41.8 D: 321.18 GV: 0.966466 LV: 1.90383 for the first output line (in grads script: sublin(result,2)):
H -- type of extrema High or Low 16.86 -- latitude 129.90 -- longitude M: 20.3321 -- magnitude G: 100.0 -- percentile of gradient L: 100.0 -- percentile of laplacian D: 12.22 -- great-circle distance [nm] away from latc (16.8) and lonc (129.7) GV: 2.2897 -- value of gradient in grid units (dx=i+1-i = 1) LV: 4.82068 -- value of laplacian in grid units
For method TM -- Tim Marchok, GFDL barnes-analysis scheme to locate extrema between grid points -- the OPTIONS are
LATC - first-guess latitude
LONC - first-guess longitude (deg E)
RADINF - search radiusm [nm]
ICTYPE - 0 -> cparm='nothing special'; 1 -> cparm='vmag' (special wind speed reatment); 2 -> cparm='zeta' (special vorticity treatment)
Example + Output:
mfhilo vt tm 16.8 129.7
mfhilo TM method for expr: vt Radinf: 250 [nm] ictype: 0 (0=> cparm=''nothing special', 1=> cparm='vmag'; 2=> cparm='zeta' GuessLon: 129.70 GuessLat: 16.80 FinalLon: 129.90 FinalLat: 16.85 FinalVal: 17.665 FinalValBesselIntrp: 20.3253
This function smooths a 2D field according to the Shuman (1957, MWR 357-361) smoother-desmoother algorithm; defaults N=1 nu1=0.5 nu2=-0.5 (light). For exampe, for a 3 passes, heavy filter enter
ga-> d smth2d(psl,3,0.5)
EXPR is a GrADS valid expression
N - number of fiter passes
ni1,...nuN - smoothing coefficients
This function returns the tangential (OPT=1, default) or radial (OPT=-1) velocity relative to a fixed LON,LAT. If no LON,LAT is provided, then the center of the grid is assumed the fixed point. For example,
ga-> d uv2trw(ua,va,-1)
displays the radial velocity, while
ga-> d uv2trw(ua,va)
displays the tangential velocity.
http://opengrads.org/ - OpenGrADS Home Page
http://cookbooks.opengrads.org/index.php - OpenGrADS Cookbooks
http://opengrads.org/wiki/index.php - OpenGrADS User Defined Extensions
http://www.iges.org/grads/ - Official GrADS Home Page
Michael Fiorino (mfiorino@gmail.com)
Copyright (C) 2009 Michael Fiorino
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
| libmf.gex - Mike Fiorino`s Collection of GrADS Extensions |