wradlib Documentation - Bitbucket

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wradlib Documentation, Release 0.1.1 3.3.3 wradlib.trafo.idecibel wradlib.trafo.idecibel(x) Calculates the inverse of input decibel values 10.**(x/10.) Parameters x : a number or an array 3.3.4 wradlib.trafo.r2depth wradlib.trafo.r2depth(x, interval) Computes rainfall depth (mm) from rainfall intensity (mm/h) Parameters x : float or array of float rainfall intensity in mm/h interval : number time interval (s) the values of x represent Returns output : float or array of float rainfall depth (mm) 3.4 Z-R Conversions Module zr takes care of transforming reflectivity into rainfall rates and vice versa z2r r2z z2rEnhanced Conversion from reflectivities to rain rates. Calculates reflectivity from rain rates using Calculates rainrates from radar reflectivities using the enhanced 3.4.1 wradlib.zr.z2r wradlib.zr.z2r(z, a=200.0, b=1.6) Conversion from reflectivities to rain rates. Calculates rain rates from radar reflectivities using a power law Z/R relationship Z = a*R**b Parameters z : a float or an array of floats Corresponds to reflectivity Z in mm**6/m**3 a, b : Parameters of the Z/R relationship Standard values according to Marshall-Palmer are a=200., b=1.6 The German Weather Service uses a=256 and b=1.42 instead of the Marshall-Palmer defaults. Returns output : a float or an array of floats rainfall intensity in mm/h 3.4.2 wradlib.zr.r2z wradlib.zr.r2z(r, a=200.0, b=1.6) Calculates reflectivity from rain rates using a power law Z/R relationship Z = a*R**b 40 Chapter 3. Library Reference
wradlib Documentation, Release 0.1.1 Parameters r : a float or an array of floats Corresponds to rainfall intensity in mm/h a, b : Parameters of the Z/R relationship Standard values according to Marshall-Palmer are a=200., b=1.6 The German Weather Service uses a=256 and b=1.42 instead of the Marshall-Palmer defaults. Returns output : a float or an array of floats reflectivity in mm**6/m**3 3.4.3 wradlib.zr.z2rEnhanced wradlib.zr.z2rEnhanced(z) Calculates rainrates from radar reflectivities using the enhanced three-part Z-R-relationship used by the DWD (as of 2009) To be used with polar representations so that one dimension is cyclical. i.e. z should be of shape (nazimuths, nbins) –> the first dimension is the cyclical one. For DWD DX-Data z’s shape is (360,128). Parameters z : a float or an array of floats Corresponds to reflectivity Z in mm**6/m**3 must be a 2-D array Returns r, si : r - array of shape z.shape - calculated rain rates si - array of shape z.shape - calculated shower index for control purposes. May be omitted in later versions 3.5 Georeferencing polar2latlon polar2latlonalt polar2centroids polar2polyvert centroid2polyvert project create_projstr projected_bincoords_from_radarspecs Transforms polar coordinates (of a PPI) to latitude/longitude coordinates. Transforms polar coordinates to lat/lon/altitude coordinates. Computes the lat/lon centroids of the radar bins from the polar coordinates. Generate 2-D polygon vertices directly from polar coordinates. Calculates the 2-D Polygon vertices necessary to form a rectangular polygon ar Convert from latitude,longitude (based on WGS84) to coordinates in map proje Conveniently supports the construction of proj.4 projection strings Convenience function to compute projected bin coordinates directly from 3.5.1 wradlib.georef.polar2latlon wradlib.georef.polar2latlon(r, az, sitecoords, re=6370040) Transforms polar coordinates (of a PPI) to latitude/longitude coordinates. This function assumes that the transformation from the polar radar coordinate system to the earth’s spherical coordinate system may be done in the same way as astronomical observations are transformed from the horizon’s coordinate system to the equatorial coordinate system. The conversion formulas used were taken from http://de.wikipedia.org/wiki/Nautisches_Dreieck [accessed 2001-11-02] and are only valid as long as the radar’s elevation angle is small, as one main assumption of this method is, that the ‘zenith-star’-side of the nautic triangle can be described by the radar range divided by the earths radius. For lager elevation angles, this side would have to be reduced. 3.5. Georeferencing 41
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