如何通过 metpy 制作锋生的横截面

Question

我想做锋生横截面我的代码是

  domain_1 = os.path.abspath(filenames_in)
info = os.path.join(domain_1, filename)
data = xr.open_dataset(info)
data = data.metpy.parse_cf().squeeze()
print(data)
p1 = data['level'].values[:]* units.hPa
start = (56, -9)
end = (56.5, -6)
cross = cross_section(data, start, end).set_coords(('latitude', 'longitude'))
r,le,t,w =xr.broadcast(cross['r'],cross['level'],cross['t'],cross['w'])
# print('r',r.shape)
# print(le)
# print('w',w.shape)
# print(w)
theta=mpcalc.potential_temperature(level,t)
cross['Potential_temperature'] = xr.DataArray(theta, coords=t.coords, dims=t.dims)
ptemp=cross['Potential_temperature']
cross['u'] = cross['u']
u = cross['u']
cross['v'] = cross['v']
v = cross['v']
# Set subset slice for the geographic extent of data to limit download
lon_slice = slice(-40, 20)
lat_slice = slice(70, 40)
# Grab lat/lon values (GFS will be 1D)
lats = data.latitude.sel(latitude=lat_slice).values
lons = data.longitude.sel(longitude=lon_slice).values
# Compute dx and dy spacing for use in vorticity calculation
dx, dy = mpcalc.lat_lon_grid_deltas(lons,lats)
front = mpcalc.frontogenesis(ptemp, u, v, dx[None,:, :], dy[None,:, :], x_dim=-1, y_dim=-2)
tmpk = data.t.metpy.sel(
    latitude=lat_slice, longitude=lon_slice).metpy.unit_array.squeeze()
uwnd = data['u'].metpy.sel(
    latitude=lat_slice, longitude=lon_slice).metpy.unit_array.squeeze()
vwnd = data['v'].metpy.sel(
    latitude=lat_slice, longitude=lon_slice).metpy.unit_array.squeeze()
potent_temp=mpcalc.potential_temperature(p1[:,None,None], tmpk)
fronto = mpcalc.frontogenesis(potent_temp, uwnd, vwnd, dx[None, :, :], dy[None, :, :], x_dim=-1, y_dim=-2)
# f=cross_section(fronto, start, end).set_coords(('latitude', 'longitude'))

总有一些错误。如何修复它不知道是先计算锋生再用交叉函数还是先用交叉函数再计算锋生。两个都试了，还是找不到横截面。

ValueError: operands could not be broadcast together with shapes (0,120,241) (19,100)

如果先计算锋生再用交叉函数

lon_slice = slice(-40, 20) 
lat_slice = slice(70, 40) 
subset = data.metpy.sel(latitude=lat_slice, longitude=lon_slice)
subset['potential_temperature'] = mpcalc.potential_temperature(
subset['level'],
subset['t'])
subset['frontogenesis'] = mpcalc.frontogensis(
subset['potential_temperature'],
subset['u'],
subset['v'])
start = (56, -9) end = (56.5, -6)
cross = cross_section(subset, start, end).set_coords(('latitude', 'longitude'))

我总是遇到这个错误

ValueError: Data missing required coordinate information. Verify that your data have been parsed by MetPy with proper x and y dimension coordinates and added crs coordinate of the correct projection for each variable.

Answer 1

鉴于 MetPy's frontogensis calculation 在二维水平网格上运行，您确实需要在获取横截面之前计算锋生。同样，子集应该在计算之前完成，因为 MetPy 尚不支持延迟计算。此外，当您让 MetPy 为您处理这些问题时，您通常会运行减少错误，而不是手动处理网格增量和单位数组，如下所示：

domain_1 = os.path.abspath(filenames_in) info = os.path.join(domain_1, filename) data = xr.open_dataset(info) data = data.metpy.parse_cf().squeeze() print(data)

lon_slice = slice(-40, 20) lat_slice = slice(70, 40) subset = data.metpy.sel(latitude=lat_slice, longitude=lon_slice)

subset['potential_temperature'] = mpcalc.potential_temperature( subset['level'], subset['t'] ) subset['frontogenesis'] = mpcalc.frontogensis( subset['potential_temperature'], subset['u'], subset['v'] )

start = (56, -9) end = (56.5, -6) cross = cross_section(subset, start, end).set_coords(('latitude', 'longitude'))

（假设您的数据具有适当的 'units' 属性以及水平和垂直对齐的网格。如果不是这种情况，打开后将需要进行一些额外的数据清理。）

如何通过 metpy 制作锋生的横截面

how to make a cross section of frontogenesis by metpy

metpy