Wrong wind direction of vertcross

vertcross、interplevel、matplotlib.quiver を使って例を再現し、その後、断面の成分を 15 km の水平風プロットと比較します。まず vertcross のドキュメントと、関連するテストまたは実装を確認します。方向の不一致を説明または修正し、検証済みのプロット方法を文書化できれば完了です。

Background

Hi, all,

I'm trying to plot the wind quiver on the crosssection. But, I find the wind direction is wrong. Here're the details.

Read data and vertcross

import numpy as np
from wrf import getvar, interplevel, ALL_TIMES, CoordPair, vertcross, to_np, latlon_coords
from netCDF4 import Dataset
import matplotlib.pyplot as plt

data_dir = '../data/wrfchem/wrfout/20200901/lnox_500/'
file = data_dir+'wrfout_d04_2020-09-01_05:00:00_subset'
ncfile = Dataset(file)

# set cross
start_lon = 118.6
end_lon = 119
start_lat = 32.1
end_lat = 31.7

start_point = CoordPair(lat=start_lat, lon=start_lon)
end_point = CoordPair(lat=end_lat, lon=end_lon)

# get vars
u = getvar(ncfile, 'ua')
v = getvar(ncfile, 'va')
w = getvar(ncfile, 'wa')
wspd = getvar(ncfile, 'uvmet_wspd_wdir')
dbz = getvar(ncfile, 'dbz')
z = getvar(ncfile, 'z', units='km')

# vertcross and subset to 0-17 km
cross_u = vertcross(u, z, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True, meta=True).sel(vertical=slice(0, 17))
cross_v = vertcross(v, z, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True, meta=True).sel(vertical=slice(0, 17))
cross_w = vertcross(w, z, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True, meta=True).sel(vertical=slice(0, 17))
cross_dbz = vertcross(dbz, z, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True, meta=True).sel(vertical=slice(0, 17))
cross_wspd = vertcross(wspd, z, wrfin=ncfile, start_point=start_point, end_point=end_point, latlon=True, meta=True).sel(vertical=slice(0, 17))

# get xlabels
coord_pairs = to_np(cross_dbz.coords["xy_loc"])
xticks = np.arange(coord_pairs.shape[0])
xlabels = [pair.latlon_str() for pair in to_np(coord_pairs)]

fig, ax = plt.subplots(figsize=(10, 6))
ax.set_xticks(xticks[::20])
ax.set_xticklabels(['(' +s.replace(',', '\n') + ')' for s in xlabels[::20]], fontsize=4) # rotation

# plot wind
xs = np.arange(0, cross_w.shape[-1], 1)
ys = to_np(cross_w.coords['vertical'])
step = 2

# plot dbz
m = ax.contourf(xs[::step],
                ys[::step],
                to_np(cross_dbz[::step, ::step]),
                cmap='Reds'
               )


q = ax.quiver(xs[::step],
              ys[::step],
              to_np(cross_u[::step, ::step]+cross_v[::step, ::step]),
              to_np(cross_w[::step, ::step])
             )

plt.colorbar(m, label='dBZ')
plt.savefig('./cross.jpg', dpi=300)

Result:

Wind interpolated to 15 km

# Get the lat/lon coordinates
lats, lons = latlon_coords(u)

zlevel = 15  # km
u_zlevel = interplevel(u, z, zlevel)
v_zlevel = interplevel(v, z, zlevel)

step = 10

fig, ax = plt.subplots(figsize=(10, 6))
q = plt.quiver(to_np(lons[::step,::step]), to_np(lats[::step,::step]),
              to_np(u_zlevel[::step, ::step]), to_np(v_zlevel[::step, ::step])
             )

qk = plt.quiverkey(q, 1, 1.05, 10, r'$10 m/s}$', labelpos='E')
plt.plot([start_lon, end_lon], [start_lat, end_lat], '-r')
plt.title('Wind at 15 km level')
plt.savefig('./zlev.jpg', dpi=300)

Problem

As you can see, the wind at the 15 km level should blow from the start point to the endpoint.
But, the 15 km wind in the crosssection is the opposite.

Is there anything wrong with my method?
Thanks in advance!