Compute the Frost Days Climate Index

This notebook computes the Frost Days index: starting from the daily minimum temperature (1980-1990) TN, the Frost Days index is the number of days where \(TN < 0°\)

As first step, let’s connect to the remote ECAS instance

from PyOphidia import cube
cube.Cube.setclient(read_env=True)

Current cdd is /home/ecasuser
Current session is https://ophidialab.cmcc.it/ophidia/sessions/28428206836738622831574257875438385/experiment
Current cwd is /
The last produced cube is https://ophidialab.cmcc.it/ophidia/6216/849438

Import input NetCDF data set (with minimum temperature in °K)

mintemp = cube.Cube(src_path='/public/data/ecas_training/E63_kp40_198001_199012_T2m_daymin_merged.nc',
    measure='temp2',
    import_metadata='yes',
    imp_dim='time',
    imp_concept_level='d', vocabulary='CF',hierarchy='oph_base|oph_base|oph_time',
    ncores=4,
    description='Min Temps'
    )

New cube is https://ophidialab.cmcc.it/ophidia/6217/849439

Identify the frost days: \(\{day \mid TN(day) < 273.15\}\) with apply (we are basically creating a mask)

frostdays = mintemp.apply(
    query="oph_predicate('OPH_FLOAT','OPH_INT',measure,'x-273.15','<0','1','0')"
)

Count the number of yearly frost days

count = frostdays.reduce2(
    operation='sum',
    dim='time',
    concept_level='y',
)

Subset on the first year

firstyear = count.subset(subset_filter=1, subset_dims='time')
firstyear.info()

Datacube Information
--------------------
+=============================================+==================+======+===========+====+==================+==========+
| PID                                         | CREATION DATE    | MEAS | MEASURE T | LE | NUMBER OF FRAGME | SOURCE F |
|                                             |                  | URE  | YPE       | VE | NTS              | ILE      |
|                                             |                  |      |           | L  |                  |          |
+=============================================+==================+======+===========+====+==================+==========+
| https://ophidialab.cmcc.it/ophidia/6217/849 | 2020-04-30 11:45 | temp | INT       | 3  | 96               |          |
| 442                                         | :00              | 2    |           |    |                  |          |
+=============================================+==================+======+===========+====+==================+==========+
Datacube Additional Information
-------------------------------
+==========+==========+===================+==============+=============+=========+=========+===+=================+
| DESCRIPT | HOST x C | FRAGMENTS x DATAB | ROWS x FRAGM | ELEMENTS x  | COMPRES | CUBE SI | U | NUMBER OF ELEME |
| ION      | UBE      | ASE               | ENT          | ROW         | SED     | ZE      | N | NTS             |
|          |          |                   |              |             |         |         | I |                 |
|          |          |                   |              |             |         |         | T |                 |
|          |          |                   |              |             |         |         |   |                 |
+==========+==========+===================+==============+=============+=========+=========+===+=================+
|          | 5        | 20                | 192          | 1           | no      | 456.000 | K | 18432           |
|          |          |                   |              |             |         | 000     | B |                 |
+==========+==========+===================+==============+=============+=========+=========+===+=================+
Dimension Information
---------------------
+======+========+======+===========+===============+=======+=======+==============+
| NAME | TYPE   | SIZE | HIERARCHY | CONCEPT LEVEL | ARRAY | LEVEL | LATTICE NAME |
|      |        |      |           |               |       |       |              |
+======+========+======+===========+===============+=======+=======+==============+
| lat  | double | 96   | oph_base  | cell          | no    | 1     |              |
|------|--------|------|-----------|---------------|-------|-------|--------------|
| lon  | double | 192  | oph_base  | cell          | no    | 2     |              |
|------|--------|------|-----------|---------------|-------|-------|--------------|
| time | double | 1    | oph_time  | year          | yes   | 1     |              |
+======+========+======+===========+===============+=======+=======+==============+
Execution time: 0.16 seconds

Plot the indicator on a map

%matplotlib inline
import warnings
warnings.filterwarnings('ignore')

import matplotlib.pyplot as plt
from mpl_toolkits.basemap import Basemap, cm, addcyclic, shiftgrid
import numpy as np

data = firstyear.export_array(show_time='yes')
lat = data['dimension'][0]['values'][:]
lon = data['dimension'][1]['values'][:]
var = data['measure'][0]['values'][:]
var = np.reshape(var, (len(lat), len(lon)))

fig = plt.figure(figsize=(15, 15), dpi=100)
ax  = fig.add_axes([0.1,0.1,0.8,0.8])

map = Basemap(projection='cyl',llcrnrlat=-90,urcrnrlat=90, llcrnrlon=-180,urcrnrlon=180, lon_0=0, resolution='c')

map.drawcoastlines()
map.drawparallels(np.arange( -90, 90,30),labels=[1,0,0,0])
map.drawmeridians(np.arange(-180,180,30),labels=[0,0,0,1])

var_cyclic, lon_cyclic = addcyclic(var, lon)
var_cyclic, lon_cyclic  = shiftgrid(180., var_cyclic, lon_cyclic, start=False)
x, y = map(*np.meshgrid(lon_cyclic,lat))

levStep = (np.max(var)-np.min(var))/10
clevs = np.arange(np.min(var),np.max(var)+levStep,levStep)

cnplot = map.contourf(x,y,var_cyclic,clevs,cmap=plt.cm.Blues)
cbar = map.colorbar(cnplot,location='right')

plt.title('Frost Days (year 1980)')
plt.show()

To clear your workspace before running other notebooks

cube.Cube.deletecontainer(container='E63_kp40_198001_199012_T2m_daymin_merged.nc', force='yes')