Convert netcdf "land" variable to latitude and longitude with Python

Question

I have a global meteorological dataset and I want to access the data for a certain grid (lat,lon). However, the data is compressed, i.e. the parameters of interest do not have the dimensions (lat, lon), but "land". "land" is a 1D array of integers.

I imported the file in python using

import scipy.io.netcdf as netcdf

path = '/path/.../ncfile.nc'

ncfile = netcdf.netcdf_file(path,'r')

Then I checked what variables there were and found that, e.g. the "Rainf" variable has the dimensions (tstep, land). I researched this on the internet and found the file landmask_gswp.nc (http://dods.ipsl.jussieu.fr/gswp/Fixed/landmask_gswp.nc), which is supposed to contain the information I need, that is, how to extract the information (lat, lon) from "land". This file contains the variables nav_lat, nav_lon and landmask. nav_lat and nav_lon relate, to my understanding, the coordinate variables x and y to latitude and longitude. "landmask" is a 2D array and contains the information ocean = 0 or land = 1. Indeed, the number of landpoints agrees with the length of my "land" 1D array. However, I cannot figure out how to extract the (lat, lon) information from it. Any help would be much appreciated.

I hope I made my problem somewhat understandable; I am not experienced with programming and/or using netcdf, so I hope that you can help out! Thanks in advance!

DHB · Accepted Answer · 2014-09-10 13:34:05Z

1

Some others might find this helpful, so here's the answer to the problem. A friend figured it out for me. "land" is the index of the flattened array nav_lat, nav_lon, i.e. the first entry of "land" corresponds to the latitude: lat.flat[land[0]] and lon.flat[land[0]].

answered Sep 10, 2014 at 13:34

DHB

114 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

N1B4 Over a year ago

Ah gotchya now. You can also use numpy reshape to convert that flattened 1D array to 2D to match the lat/lon arrays.

N1B4 · Accepted Answer · 2014-09-09 18:45:58Z

0

You can extract variables from ncfile using

lat = ncfile.variables['nav_lat'][:,:]
lon = ncfile.variables['nav_lon'][:,:]

This will create 2D numpy arrays lat and lon.

answered Sep 9, 2014 at 18:45

N1B4

3,4631 gold badge23 silver badges25 bronze badges

1 Comment

DHB Over a year ago

Hi and thanks for your answer. I think I might not have formulated my problem properly. I know how to get lat and lon if there are variables named nav_lat and nav_lon. My problem is that in my original netcdf file, there are no variables lat and lon, but only a variable "land", which is 1D. My question is: How do I extract the information (lat, lon) from the 1D array "land"?

Collectives™ on Stack Overflow

Convert netcdf "land" variable to latitude and longitude with Python

2 Answers 2

1 Comment

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related