用Python numpy计算相对涡度

时间:2014-04-29 19:27:32

标签: python numpy netcdf differentiation

我正在尝试计算相对涡度,即dV / dX - dU / dY,我目前正在使用numpy上的梯度函数。这是我的代码如下。我想知道是否有更好的方法来做这个,而不是在我想做dU / dY时尝试重塑数组。有一个更好的分化方法,给定一个数字只有U和Y的两个矩阵,我想区分你的Y.

import numpy as np
import netCDF4
import matplotlib.pyplot as plt
from numpy import *
import decimal
from netCDF4 import Dataset

ncfile= Dataset('test.nc','r')

#--------------------Reading in Variables---------------------------------#

lon      = ncfile.variables['lon'][:]
lat      = ncfile.variables['lat'][:]
UWind850 = ncfile.variables['U'][:,22,:,:] (time, level,lat,lon)
VWind850 = ncfile.variables['V'][:,22,:,:] (time, level,lat,lon)
time     = ncfile.variables['time'][:] 
MSLP     = ncfile.variables['PSL'][:]

# Variable[time,Longitude,Latitude]
#These values are equivalent to I,J and L in the netCDF file

t = 30  #time
x = 300 #longitude 
y = 240 #latitude


#-----------------------Calculating Vorticity-----------------------------#

dX = np.gradient(lon) #shape 300
dY = np.gradient(lat) #shape 240

#VWind850.shape (30,240,300)
#UWind850.shape (30,240,300)

dV = (np.gradient(VWind850))

#dV.shape(3,30,240,300) --The extra "3" dimension is caused by the gradient because 
#Its creating a Matrix for gradients by (time,latitude,longitude)

Vgradient =  dV[2]/dX



UWindTemp = np.reshape(UWind850,(30,300,240)) # I am reshaping so I can divide by dY



dU = (np.gradient(UWindTemp))
Ugradient =  dU[2]/dY
Ugradient = np.reshape(Ugradient,(30,240,300)) # Taking it back to normal


VORT= Vgradient - Ugradient 

# VORT.shape(time, latitude, longitude)
#-------------------------------------------------------------------------#

0 个答案:

没有答案