Isentropic Analysis

The meteolib function isentropic_interpolation allows for isentropic analysis from model analysis data in isobaric coordinates.

fn = 'D:/Temp/nc/narr_example.nc'
f = addfile(fn)
pres = f['isobaric'][:]
tmpk = f['Temperature'][:]
u_wind = f['u_wind'][:]
v_wind = f['v_wind'][:]
sh = f['Specific_humidity'][:]
y = tmpk.dimvalue(-2)
x = tmpk.dimvalue(-1)

isentlevs = [296.]
pres, tmpk, u_wind, v_wind, sh = meteolib.isentropic_interpolation(isentlevs, pres,
    tmpk, u_wind, v_wind, sh, temperature_out=True)
rh = meteolib.relative_humidity_from_specific_humidity(pres, tmpk, sh) * 100

#plot
axesm(projinfo=f.proj)
geoshow('us_states')
geoshow('country')
# Plot rh
levs = arange(10., 106, 5)
grh = contourf(x, y, rh[0], levs, cmap='MPL_gist_earth_r', proj=f.proj)
colorbar(grh, orientation='horizontal', aspect=40, shrink=0.8,
    label='Relative Humidity')
# Plot the surface
clevisent = arange(0, 1000, 25)
cs = contour(x, y, pres[0], clevisent, colors='k', linewidths=1.0, proj=f.proj)
clabel(cs, fontsize=10, fmt='%i', drawshadow=False)
# Plot wind barbs
xx, yy = meshgrid(x, y)
wind_slice = slice(None, None, 6)
barbs(xx[wind_slice,wind_slice], yy[wind_slice,wind_slice], u_wind[0,wind_slice,wind_slice], v_wind[0,wind_slice,wind_slice],
    size=6, proj=f.proj)

axis([-122, -75, 25, 50])