Tutorials

Contents

• Tutorials
  • Import the library
  • Extracting variable from a NetCDF file
  • Getting a regional slide of your data
  • Print basic info about a Variable
  • Computing time average

Import the library

>>> import geodat

Extracting variable from a NetCDF file

You can use getvar() for extracting one variable and its associated dimensions from a NetCDF file.

>>> # Extract sea surface temperature from a file sst.nc
>>> # "sst" is the variable name
>>> sst = geodat.nc.getvar("sst.nc", "sst")
>>> print sst
<geodat.nc.Variable sst(time,lat,lon), shape: (120, 180, 360)>

Getting a regional slide of your data

Suppose you already have a Variable sst, you can get a regional slice of it by simply calling the variable as a function:

>>> # This returns a new Variable
>>> sst_regional = sst(lat=(-20., 20.), lon=(100., 220.))
>>> sst_regional
<geodat.nc.Variable sst(time,lat,lon), shape: (120, 40, 120)>
>>> sst # unchanged
<geodat.nc.Variable sst(time,lat,lon), shape: (120, 180, 360)>

The specified range is inclusive. The example above will slice the region where 20S<=latitude<=20N and 100E<=longitude<=40W.

This is the same as calling getRegion().

>>> sst_regional = sst.getRegion(lat=(-20., 20.),
                                 lon=(100., 220.))

Other names referring to time, depth, latitude and longitude are also accepted:

Name	Other names (and their upper case)
Time	time, t
Longitude	longitude, lon, x
Latitude	latitude, lat, y
Depth	depth, dep, level, lev, z

You can also set the region when you load the data.

>>> # Extract regional sea surface temperature from a file sst.nc
>>> # Latitude: 20S-20N, Longitude: 100E-220E
>>> sst = geodat.nc.getvar("sst.nc", "sst",
                           lat=(-20., 20.), lon=(100., 220.))
>>> sst
<geodat.nc.Variable sst(time,lat,lon), shape: (120, 40, 120)>

This is in fact equivalent to calling getRegion() after getvar() and assigning it to sst.

Print basic info about a Variable

>>> sst.info()
<geodat.nc.Variable sst(time,lat,lon), shape: (120, 180, 360)>
Attributes:
    sst:_FillValue = 1e+20
    sst:standard_name = sst
    sst:description = HadISST 1.1 monthly average SST Climatology
    sst:long_name = Monthly 1 degree resolution SST
    sst:units = degK
    sst:history = ; From file: sst.nc
Dim: time = 15.5:349.7425 Unit: days since 0001-01-01 00:00:00
Dim: lat = -89.5:89.5 Unit: degrees_north
Dim: lon = 0.5:359.5 Unit: degrees_east

Computing time average

>>> print sst
<geodat.nc.Variable sst(time,lat,lon), shape: (120, 180, 360)>
>>> sst_tave = sst.time_ave()
>>> print sst_tave
<geodat.nc.Variable sst(time,lat,lon), shape: (1, 180, 360)>