Advanced Sounding

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd

import metpy.calc as mpcalc
from metpy.cbook import get_test_data
from metpy.plots import add_metpy_logo, SkewT
from metpy.units import units

col_names = ['pressure', 'height', 'temperature', 'dewpoint', 'direction', 'speed']

sounding_data = pd.read_fwf(get_test_data('may4_sounding.txt', as_file_obj=False),
                 skiprows=5, usecols=[0, 1, 2, 3, 6, 7], names=col_names)

# Drop any rows with all not a number (NaN) values for temperature, dewpoint, and winds
sounding_data = sounding_data.dropna(subset=('temperature', 'dewpoint', 'direction', 'speed'
                       ), how='all').reset_index(drop=True)

pres = sounding_data['pressure'].values * units.hPa
temp = sounding_data['temperature'].values * units.degC
dewpoint = sounding_data['dewpoint'].values * units.degC
wind_speed = sounding_data['speed'].values * units.knots
wind_dir = sounding_data['direction'].values * units.degrees
u, v = mpcalc.wind_components(wind_speed, wind_dir)

# Create figure and set size
fig = plt.figure(figsize=(9, 9))
skew = SkewT(fig, rotation=45)

# Plot temperature, dewpoint and wind barbs
skew.plot(pres, temp, 'red')
skew.plot(pres, dewpoint, 'green')

# Plot wind barbs
my_interval = np.arange(100, 1000, 50) * units('hPa') #set spacing interval
ix = mpcalc.resample_nn_1d(pres, my_interval) #find nearest indices for chosen interval
skew.plot_barbs(pres[ix], u[ix], v[ix], xloc=1) #plot values closest to chosen interval

# Improve labels and set axis limits
skew.ax.set_xlabel('Temperature (\N{DEGREE CELSIUS})')
skew.ax.set_ylabel('Pressure (hPa)')
skew.ax.set_ylim(1000, 100)
skew.ax.set_xlim(-40, 59)

# Calculate LCL height and plot as black dot.
lcl_pressure, lcl_temperature = mpcalc.lcl(pres[0], temp[0], dewpoint[0]) #index 0 is chosen to lift parcel from the surface
skew.plot(lcl_pressure, lcl_temperature, 'ko', markerfacecolor='black')

# Calculate full parcel profile and add to plot as black line
prof = mpcalc.parcel_profile(pres, temp[0], dewpoint[0]).to('degC')
skew.plot(pres, prof, 'black', linewidth=2)

# Shade areas of CAPE and CIN
skew.shade_cin(pres, temp, prof, dewpoint)
skew.shade_cape(pres, temp, prof)

# Add emphasis to 0 degree isotherm with color change
skew.ax.axvline(0, color='c', linestyle='--', linewidth=2)

# Add the relevant special lines throughout the figure
skew.plot_dry_adiabats(t0=np.arange(233, 533, 15) * units.K, alpha=0.25, color='orangered')
skew.plot_moist_adiabats(t0=np.arange(233, 400, 10) * units.K, alpha=0.25, color='tab:green')
skew.plot_mixing_lines(pressure=np.arange(1000, 99, -25) * units.hPa, linestyle='dotted', color='tab:blue')

# Add the MetPy logo!
fig = plt.gcf()
add_metpy_logo(fig, 115, 100, size='small');

# Add a title
plt.title('Advanced Sounding');