"Python tutorial" geo-visualization

Matplotlib is a common data-drawing package for Python, and its drawing is powerful, while Basemap is a sub-package of matplotlib, responsible for map drawing. This article briefly describes how to draw a wind map with this package. Here's how:

Import command

1) Set up the working environment and import the package

%CD "F:\\dropbox\\python" import numpy as Npimport Matplotlib.pyplot as Pltimport datetimefrom mpl_toolkits.basemap Import Basemap, shiftgridfrom netCDF4 import Dataset

3) Set the time and read the data

yyyy=1993; mm=03; dd=14; Hh=00date = Datetime.datetime (yyyy,mm,dd,hh) urlbase= "Http://nomads.ncdc.noaa.gov/thredds/dodsC/modeldata/cmd_ pgbh/"Url=urlbase+"%04i/%04i%02i/%04i%02i%02i/pgbh00.gdas.%0 4i%02i%02i%02i.grb2 "%\ (yyyy,yyyy,mm,yyyy,mm,dd,yyyy,mm,dd,hh) data = Dataset (URL)

4) Data preprocessing

latitudes = data.variables[' lat '][::-1]longitudes = data.variables[' lon '][:].tolist () Slpin = 0.01*data.variables[' PRESSURE_MSL '][:].squeeze () slp[:,0:-1] = slpin[::-1]; Slp[:,-1] = Slpin[::-1,0]u = Np.zeros ((uin.shape[0],uin.shape[1]+1), np.float64) u[:,0:-1] = uin[::-1]; U[:,-1] = Uin[::-1,0]v = Np.zeros ((vin.shape[0],vin.shape[1]+1), np.float64) v[:,0:-1] = vin[::-1]; V[:,-1] = vin[::-1,0]longitudes.append (360.); longitudes = Np.array (longitudes) lons, lats = Np.meshgrid (longitudes,latitudes)

5) Set and draw the diagram

m = Basemap (resolution= ' C ', projection= ' ortho ', lat_0=60.,lon_0=-60.) FIG1 = Plt.figure (figsize= (8,10)) ax = Fig1.add_axes ([0.1,0.1,0.8,0.8]) Clevs = Np.arange (960,1061,5) x, y = m (lons, lats) Parallels = Np.arange ( -80.,90,20.) meridians = Np.arange (0.,360.,20.) CS1 = M.contour (x,y,slp,clevs,linewidths=0.5,colors= ' K ', animated=true) CS2 = M.contourf (x,y,slp,clevs,cmap= plt.cm.rdbu_r,animated=true) ugrid,newlons = Shiftgrid (180.,u,longitudes,start=false) vgrid,newlons = Shiftgrid (180. , v,longitudes,start=false) Uproj,vproj,xx,yy = \m.transform_vector (ugrid,vgrid,newlons,latitudes,31,31,returnxy= true,masked=true) Q = M.quiver (xx,yy,uproj,vproj,scale=700) qk = Plt.quiverkey (Q, 0.1, 0.1, + M/s, labelpos= ' W ') M.drawcoastlines (linewidth=1.5) m.drawparallels (parallels) M.drawmeridians (meridians) cb = M.colorbar (CS2, "bottom", Size= "5%", pad= "2%") Cb.set_label (' HPa ') ax.set_title (' SLP and Wind Vectors ' +str (date)) Plt.show ()

The output image is as follows

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