# Other modules for geoscientists¶

Nikolay Koldunov

[email protected]

This is part of Python for Geosciences notes.

=============

Some of the things will not work on ZMAW computers (Iris, Cartopy).

In [31]:
%matplotlib inline
import matplotlib.pylab as plt
import numpy as np


## Cartopy¶

Cartopy is a library providing cartographic tools for python.

Some of the key features of cartopy are:

• object oriented projection definitions
• point, line, polygon and image transformations between projections
• integration to expose advanced mapping in matplotlib with a simple and intuitive interface

Simple plot:

In [16]:
fig, ax = make_cartopy(projection=ccrs.Robinson(), resolution='110m')
_ = ax.plot(lon, lat, transform=ccrs.Geodetic(), **kw)

In [1]:
import cartopy.crs as ccrs
import cartopy.feature as cfeature

In [5]:
plt.figure(figsize=(8,7))
lat = 53.565278
lon = 10.001389
ax = plt.axes(projection=ccrs.Mercator())
ax.set_extent([-20.,40.,32.,64.])
ax.coastlines(resolution='50m')
ax.scatter(lon,lat,300,transform=ccrs.Geodetic())

Out[5]:
<matplotlib.collections.PathCollection at 0x119982b00>
In [7]:
plt.figure(figsize=(8,7))
ax = plt.axes(projection=ccrs.Mercator())
ax.set_extent([-20.,40.,32.,64.])
ax.coastlines(resolution='50m',zorder=9)

ax.scatter(lon,lat,300,transform=ccrs.Geodetic(),zorder=10)

Out[7]:
<matplotlib.collections.PathCollection at 0x119c6aa90>
In [8]:
from cartopy.io.img_tiles import GoogleTiles, OSM,QuadtreeTiles,MapQuestOpenAerial,MapQuestOSM

In [9]:
plt.figure(figsize=(8,7))
ax = plt.axes(projection=ccrs.Mercator())
ax.set_extent([-20.,40.,32.,64.])
ax.coastlines(resolution='50m',zorder=9)
ax.scatter(lon,lat,30,transform=ccrs.PlateCarree(),zorder=10)

In [10]:
plt.figure(figsize=(8,7))
ax = plt.axes(projection=ccrs.Mercator())
ax.set_extent([9.95,10.05,53.55,53.6])
ax.scatter(lon,lat,500,transform=ccrs.Geodetic(),zorder=10)
gg_tiles = OSM()

In [12]:
from netCDF4 import Dataset
fl = Dataset('./air.2m.gauss.2016.nc')
air = fl.variables['air'][0,:,:]
lat = fl.variables['lat'][:]
lon = fl.variables['lon'][:]

In [13]:
from cartopy.util import add_cyclic_point

In [14]:
air_cyc, lon_cyc = add_cyclic_point(air, coord=lon)

In [15]:
plt.figure(figsize=(10,5))
ax = plt.axes(projection=ccrs.Robinson(central_longitude=120))
ax.coastlines()
gl = ax.gridlines(draw_labels=False) # Only PlateCarree and Mercator plots are currently supported.
ax.contourf(lon_cyc,lat,air_cyc, transform=ccrs.PlateCarree())

Out[15]:
<matplotlib.contour.QuadContourSet at 0x11b95ab70>

# Pydap¶

Pydap is a pure Python library implementing the Data Access Protocol, also known as DODS or OPeNDAP. You can use Pydap as a client to access hundreds of scientific datasets in a transparent and efficient way through the internet; or as a server to easily distribute your data from a variety of formats.

In [16]:
from pydap.client import open_url

In [21]:
dataset = open_url(u"http://icdc.cen.uni-hamburg.de/thredds/dodsC/ssmi_asi_icecon_arc2011")

In [23]:
print(dataset)

<DatasetType with children 'latitude', 'longitude', 'time', 'sea_ice_area_fraction', 'land'>

In [25]:
ice = dataset['sea_ice_area_fraction']

In [26]:
ice.shape

Out[26]:
(365, 896, 608)
In [35]:
ice.attributes

Out[35]:
{'_FillValue': 103,
'coordinates': 'latitude longitude time',
'long_name': 'sea-ice concentration',
'missing_value': 101,
'scale_factor': 1.0,
'standard_name': 'sea_ice_area_fraction',
'units': 'percent'}
In [36]:
plt.imshow(np.squeeze(ice[0,:,:]))
plt.colorbar()

Out[36]:
<matplotlib.colorbar.Colorbar at 0x11b12bef0>

## F2PY¶

The F2PY project is created to unify the efforts of supporting easy connection between Fortran and Python languages. Example below is from Using Python and FORTRAN with F2py.

Create FORTRAN file (use %%file instead of %%writefile if you on IPython < 1.0):

In [37]:
%%writefile FIB1.F
C FILE: FIB1.F
SUBROUTINE FIB(A,N)
C
C     CALCULATE FIRST N FIBONACCI NUMBERS
C
INTEGER N
REAL*8 A(N)
DO I=1,N
IF (I.EQ.1) THEN
A(I) = 0.0D0
ELSEIF (I.EQ.2) THEN
A(I) = 1.0D0
ELSE
A(I) = A(I-1) + A(I-2)
ENDIF
ENDDO
END
C END FILE FIB1.F

Writing FIB1.F


Compile it with f2py:

In [38]:
!f2py -c -m --fcompiler=gnu95 fib1 FIB1.F

running build
running config_cc
unifing config_cc, config, build_clib, build_ext, build commands --compiler options
running config_fc
unifing config_fc, config, build_clib, build_ext, build commands --fcompiler options
running build_src
build_src
building extension "fib1" sources
f2py options: []
f2py:> /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fib1module.c
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6
Post-processing...
Block: fib1
Block: fib
Post-processing (stage 2)...
Building modules...
Building module "fib1"...
Constructing wrapper function "fib"...
fib(a,[n])
Wrote C/API module "fib1" to file "/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fib1module.c"
copying /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/f2py/src/fortranobject.c -> /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6
copying /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/f2py/src/fortranobject.h -> /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6
build_src: building npy-pkg config files
running build_ext
customize UnixCCompiler
customize UnixCCompiler using build_ext
customize Gnu95FCompiler
Found executable /usr/local/bin/gfortran
customize Gnu95FCompiler using build_ext
building 'fib1' extension
compiling C sources
C compiler: gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/koldunovn/miniconda3/include -arch x86_64 -I/Users/koldunovn/miniconda3/include -arch x86_64

creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk
creating /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6
compile options: '-I/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6 -I/Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include -I/Users/koldunovn/miniconda3/include/python3.6m -c'
gcc: /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fib1module.c
In file included from /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fib1module.c:19:
In file included from /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fortranobject.h:13:
In file included from /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/arrayobject.h:4:
In file included from /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/ndarrayobject.h:18:
In file included from /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/ndarraytypes.h:1788:
/Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/npy_1_7_deprecated_api.h:15:2: warning: "Using deprecated NumPy API, disable it by "          "#defining NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION" [-W#warnings]
#warning "Using deprecated NumPy API, disable it by " \
^
/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fib1module.c:112:12: warning: unused function 'f2py_size' [-Wunused-function]
static int f2py_size(PyArrayObject* var, ...)
^
2 warnings generated.
gcc: /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fortranobject.c
In file included from /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fortranobject.c:2:
In file included from /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fortranobject.h:13:
In file included from /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/arrayobject.h:4:
In file included from /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/ndarrayobject.h:18:
In file included from /Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/ndarraytypes.h:1788:
/Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include/numpy/npy_1_7_deprecated_api.h:15:2: warning: "Using deprecated NumPy API, disable it by "          "#defining NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION" [-W#warnings]
#warning "Using deprecated NumPy API, disable it by " \
^
/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fortranobject.c:139:18: warning: comparison of integers of different signs: 'Py_ssize_t' (aka 'long') and 'unsigned long' [-Wsign-compare]
if (size < sizeof(notalloc)) {
~~~~ ^ ~~~~~~~~~~~~~~~~
2 warnings generated.
compiling Fortran sources
Fortran f77 compiler: /usr/local/bin/gfortran -Wall -g -ffixed-form -fno-second-underscore -arch x86_64 -fPIC -O3 -funroll-loops
Fortran f90 compiler: /usr/local/bin/gfortran -Wall -g -fno-second-underscore -arch x86_64 -fPIC -O3 -funroll-loops
Fortran fix compiler: /usr/local/bin/gfortran -Wall -g -ffixed-form -fno-second-underscore -Wall -g -fno-second-underscore -arch x86_64 -fPIC -O3 -funroll-loops
compile options: '-I/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6 -I/Users/koldunovn/miniconda3/lib/python3.6/site-packages/numpy/core/include -I/Users/koldunovn/miniconda3/include/python3.6m -c'
gfortran:f77: FIB1.F
/usr/local/bin/gfortran -Wall -g -arch x86_64 -Wall -g -undefined dynamic_lookup -bundle /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fib1module.o /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/src.macosx-10.7-x86_64-3.6/fortranobject.o /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk/FIB1.o -L/usr/local/Cellar/gcc/7.1.0/lib/gcc/7/gcc/x86_64-apple-darwin16.5.0/7.1.0 -L/Users/koldunovn/miniconda3/lib -lgfortran -o ./fib1.cpython-36m-darwin.so
Removing build directory /var/folders/yq/03v059jn4sg2xhnhpnrqkgcc0000gn/T/tmprf2kbptk


Import resulting fib1.so as python library:

In [39]:
import fib1


In [41]:
print(fib1.__doc__)
print(fib1.fib.__doc__)

This module 'fib1' is auto-generated with f2py (version:2).
Functions:
fib(a,n=len(a))
.
fib(a,[n])

Wrapper for fib.

Parameters
----------
a : input rank-1 array('d') with bounds (n)

Other Parameters
----------------
n : input int, optional
Default: len(a)



Use fib function:

In [42]:
import numpy as np

In [45]:
a=np.zeros(15,'d')
fib1.fib(a)
a

Out[45]:
array([   0.,    1.,    1.,    2.,    3.,    5.,    8.,   13.,   21.,
34.,   55.,   89.,  144.,  233.,  377.])