Interpolation problem in Temperature at 850 hPa

[Carlos Calvo Sancho]

Hello everyone, 

Last days I tried to run a script to postprocessate the temperature at 850 hPa but in the mountains chains the interpolation doesn't work well. I don't know why this don't work... I attached the script and a plot. 

#este programa é valido para un corte vertical

import numpy as np

from netCDF4 import Dataset

from mpl_toolkits.basemap import  Basemap

import matplotlib

matplotlib.use('Agg')

import matplotlib.pyplot as plt

from matplotlib.cm import get_cmap

import matplotlib.colors as mcolors

from datetime import datetime , timedelta 

from wrf import (interplevel, getvar, vertcross, smooth2d, latlon_coords, ALL_TIMES)

# Open the NetCDF file

#abrir o archivo no que queremos traballar

ncfile = Dataset("/Users/carlos-wrf/Documents/WRF/DanaSeptiembre.nc")

#todo esto é sempre igual

# Create polar stereographic Basemap instance.

lon = getvar(ncfile, "XLONG").values #transformo para obter só valores 

lat = getvar(ncfile, "XLAT").values

#para facer un corte vertical necesito centrar as latitudes e lonxitudes das miñas graficas, para a partir de aí traballar

cen_lat = float(ncfile.CEN_LAT)

cen_lon = float(ncfile.CEN_LON)

# lat_1 is first standard parallel.

# lat_2 is second standard parallel (defaults to lat_1).

# lon_0,lat_0 is central point.

# llcrnrlon = Longitud de la esquina inferior izquierda 

# llcrnrlat = Latitud de la esquina inferior izquierda 

# urcrnrlon = Longitud de la esquina superior derecha 

# urcrnrlat = Latitud de la esquina superior derecha 

m = Basemap(resolution='h',projection='lcc',llcrnrlon=lon[0,0],llcrnrlat=lat[0,0],urcrnrlon=lon[-2,-2],urcrnrlat=lat[-1,-1],lon_0=cen_lon,lat_1=cen_lat,lat_2=cen_lat)

#empezamos en 4,4 porque os bordes do modelo non son bos

# Coordinates

x, y = m(lon, lat)

 #Parallels.

parallels = np.arange(0.,90,5)

# Meridians

meridians = np.arange(-180.,180.,5)

#Loop for several plots

start_time=datetime(2019,9,8) #cando queremos empezar

delta=timedelta(hours=3) #cando canto actualizamos a imaxe

T_start = getvar(ncfile,"T",timeidx=0)

P_start = getvar(ncfile,"P",timeidx=0)

for d in range(0,25): #d es el número de pasos temporales que tenemos.

# Get the sea level pressure

 t2m = getvar(ncfile,"T2",timeidx=d)-273.15     #ºC

 p = getvar(ncfile, "pressure",timeidx=d)       #hPa

 #ht = getvar(ncfile, "z", units="dm")

 temp = getvar(ncfile,"temp",timeidx=d)-273.15              #ºC

 z = getvar(ncfile,"z",timeidx=d, units="dm")

 t850 = interplevel(temp, p, 850.0, missing=9.969209968386869e+36, squeeze=True, meta=False)

# Create figure

 plt.figure(figsize=(7,7)) #tamaño da figura creada

# Plotting

 clevs=np.arange(-5,30,1.75)

 cs1 = m.contourf(x,y,t850,clevs,cmap='nipy_spectral',extend='both') # vmin y vmax establecen los valores mínimos y máximos de la escala de colores

 cs2 = m.contour(x,y,t850, levels=clevs, colors="black", linewidths=0.5)

 plt.clabel(cs2, inline=0, fontsize=10, fmt="%i")

 plt.title(str(start_time)[0:10]+' T'+str(start_time)[11:13]+':00:00')

#dibuxar a forma de continentes e etc

 m.drawcoastlines()

 m.drawcountries()

 m.drawparallels(parallels,labels=[1,0,0,0],fontsize=8,linewidth=0.)

 m.drawmeridians(meridians,labels=[0,0,0,1],fontsize=8,linewidth=0.)

 cbar= m.colorbar(cs1,location='bottom',pad="5%",ticks=clevs)

 cbar.ax.tick_params(labelsize=7)

 cbar.set_label("$^{\circ}$C",fontsize=8)

  

 plt.savefig('/Users/carlos-wrf/Documents/test/t850_basic_'+str(start_time)[0:10]+'_'+str(start_time)[11:13]+'.png',dpi=300)

 plt.close()

 start_time=start_time + delta

[Federico Cutraro]

Hello Carlos, I'm pretty sure that the function interplevel don't extrapolate values below the surface. You could check if on the mountains the surface pressure is lower than 850 hPa.

Regards,

Federico

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[Domingo Cassain]

Hi Carlos.

can you solve your problem?

I'm new using WRF-Python and I have the same problem.

If you have the solution, can you make it available to us?

Regards

Cassain

[Dileepkumar R]

Hi Domingo,

I have also faced the same problem. Instead of  "wrf.interplevel" we should use "wtf.vinterp", in which we need to enable "extrapolate=True"

That's it.

Dileepkumar R

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[Domingo Cassain]

Hello Dileepkumar,

Thank you for your help. I applied it here and it worked well.

Best Regards.

Domingo Cassain

--

------------------------------------------------------------------------------------------------------

Domingo Cassain Sales

Doutor em Meteorologia (INPE)

Pesquisador em Modelagem Atmosférica (FUNCEME)

FUNCEME - Fundação Cearense de Meteorologia e Recursos Hídricos

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[Carlos Calvo Sancho]

Hello Domingo, 

Sorry for answer so late but I don't see it before. And, also, I don't resolve the problem... 

Can you upload the code to see it? 

Thank you. 

Carlos C. 

Hi Domingo,

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[Dileepkumar R]

Hi Carlo, 

############################################

import wrf

ncfile = Dataset("/Users/carlos-wrf/Documents/WRF/DanaSeptiembre.nc")

#p_levels = [1000.0, 975.0, 950.0, 925.0, 900.0, 875.0, 850.0, 825.0, 800.0, 775.0, 750.0, 700.0, 650.0, 600.0, 550.0, 500.0, 450.0, 400.0, 350.0, 300.0, 250.0, 225.0, 200.0, 175.0, 150.0, 125.0, 100.0]

#since  you need only 850hPa, so you can use 

p_levels = [850.0]

t850 = wrf.vinterp(wrfin=ncfile,field =temp, vert_coord='pressure', interp_levels = p_levels, extrapolate = True, field_type = None,log_p=True, timeidx=ALL_TIMES)

############################################

I hope it will work, if not please send me the error log. 

Also, check this page: https://wrf-python.readthedocs.io/en/latest/user_api/generated/wrf.vinterp.html

with regards,

Dileepkumar R

Postdoctoral Researcher,

Interdisciplinary Centre for Water Research (ICWaR),

Indian Institute of Sciences, Bangalore, 560012

 

[Carlos Calvo Sancho]

It's works!!!!! Thank you very much Dileepkumar!!

Best regards, 

Carlos C.