Read KNMI observations using hydropandas

This notebook introduces how to use the hydropandas package to read, process and visualise KNMI data.

Martin & Onno - 2022

Notebook contents

  1. Observation types

  2. Get KNMI data

  3. Get ObsCollections

  4. Precipitation

  5. KNMI climate scenario’s

  6. Evaporation

  7. Spatial interpolation

[1]:

import logging

import matplotlib.pyplot as plt
import numpy as np
import pandas as pd
from IPython.display import display
from scipy.interpolate import NearestNDInterpolator, RBFInterpolator
from tqdm import tqdm

import hydropandas as hpd
from hydropandas.io import knmi

[2]:

hpd.util.get_color_logger("INFO")

[2]:

<RootLogger root (INFO)>

Observation types

The hydropandas package has a function to read all kinds of KNMI observations. These are stored in an Obs object. There are three types of observations you can obtain from the KNMI:

  • EvaporationObs, for evaporation time series

  • PrecipitationObs, for precipitation time series

  • MeteoObs, for all the other meteorological time series

Get evaporation in [m/day] for KNMI station 344 (Rotterdam Airport).

[3]:

o = hpd.EvaporationObs.from_knmi(stn=344, start="2022")
display(o.head())
o.plot()

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable EV24 from 2022-01-01 to None

hydropandas.EvaporationObs

EV24_ROTTERDAM_344
unit m
y 441636.854285
source KNMI
x 90061.930891
location ROTTERDAM
station 344
crs EPSG:28992
meteo_var EV24
filename

EV24
YYYYMMDD
2022-01-01 01:00:00 0.0003
2022-01-02 01:00:00 0.0003
2022-01-03 01:00:00 0.0002
2022-01-04 01:00:00 0.0002
2022-01-05 01:00:00 0.0001 
[3]:

<Axes: xlabel='YYYYMMDD'>
../_images/examples_02_knmi_observations_5_3.png

Get precipitation in [m/day] for KNMI station 344 (Rotterdam Airport).

[4]:

o = hpd.PrecipitationObs.from_knmi(stn=344, start="2022")
display(o.head())
o.plot()

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable RH from 2022-01-01 to None

hydropandas.PrecipitationObs

RH_ROTTERDAM_344
unit m
y 441636.854285
source KNMI
x 90061.930891
location ROTTERDAM
station 344
crs EPSG:28992
meteo_var RH
filename

RH
YYYYMMDD
2022-01-01 01:00:00 0.0000
2022-01-02 01:00:00 0.0002
2022-01-03 01:00:00 0.0064
2022-01-04 01:00:00 0.0000
2022-01-05 01:00:00 0.0008 
[4]:

<Axes: xlabel='YYYYMMDD'>
../_images/examples_02_knmi_observations_7_3.png

Get temperature in [°C] for KNMI station 344 (Rotterdam Airport).

[5]:

o = hpd.MeteoObs.from_knmi(stn=344, meteo_var="TG", start="2022")
display(o.head())
o.plot()

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable TG from 2022-01-01 to None

hydropandas.MeteoObs

TG_ROTTERDAM_344
unit
y 441636.854285
source KNMI
x 90061.930891
location ROTTERDAM
station 344
crs EPSG:28992
meteo_var TG
filename

TG
YYYYMMDD
2022-01-01 01:00:00 12.4
2022-01-02 01:00:00 12.1
2022-01-03 01:00:00 11.6
2022-01-04 01:00:00 9.7
2022-01-05 01:00:00 6.7 
[5]:

<Axes: xlabel='YYYYMMDD'>
../_images/examples_02_knmi_observations_9_3.png

attributes

All PrecipitationObs, EvaporationObs and MeteoObs objects have the attributes:

  • name: meteo variable and station name

  • x: x-coordinate in m RD

  • y: y-coordinate in m RD

  • station: station number

  • unit: measurement unit

  • meta: dictionary with other metadata

[6]:

print(f"name: {o.name}")
print(f"x,y: {(o.x, o.y)}")
print(f"station: {o.station}")
print("unit", o.unit)
print("metadata:")
for key, item in o.meta.items():
    print(f"    {key}: {item}")

name: TG_ROTTERDAM_344
x,y: (np.float64(90061.9308913925), np.float64(441636.8542853093))
station: 344
unit
metadata:
    TG: Etmaalgemiddelde temperatuur (in graden Celsius) / Daily mean temperature in (degrees Celsius)

Get KNMI data

The from_knmi method can be used to obtain one type of measurements at one station. There are two ways to select the station.

  1. with the station number stn

  2. by specifying the xy coordinates, the station nearest to this coordinates is used.

Below both methods are used to obtain precipitation measurements. Notice that they return the same data because station 344 is nearest to the given xy coordinates.

[7]:

o1 = hpd.PrecipitationObs.from_knmi(stn=344)
o2 = hpd.PrecipitationObs.from_knmi(xy=(90600, 442800))
o1.equals(o2)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable RH from None to None
INFO:hydropandas.io.knmi.get_knmi_obs:get KNMI data from station nearest to coordinates (90600, 442800) and meteovariable RH

[7]:

True

read options

The from_knmi method has other optional arguments:

  • stn: station number.

  • start: the start date of the time series you want, default is 1st of January 2019.

  • end: the end date of the time series you want, default is today.

  • fill_missing_obs: option to fill missing values with values from the nearest KNMI station. If measurements are filled an extra column is added to the time series in which the station number is shown that was used to fill a particular missing value.

  • interval: time interval of the time series, default is ‘daily’

  • use_api: select the method to obtain the data, default is ‘True’

  • raise_exception: option to raise an error when the requested time series is empty. ***

The 3 examples below give a brief summary of these options

[8]:

# example 1 get daily average temperature (TG) from 1900 till now
o_t = hpd.MeteoObs.from_knmi("TG", stn=344, start="1960")
o_t.plot(figsize=(16, 4), grid=True);

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable TG from 1960-01-01 to None
../_images/examples_02_knmi_observations_15_1.png 
[9]:

# example 2 get daily average precipitation from 1972 with and without filling missing measurements
f, axes = plt.subplots(figsize=(16, 6), nrows=2, sharex=True, sharey=True)

o_rd = hpd.PrecipitationObs.from_knmi(
    "RD", stn=892, start="1972", end="2023", fill_missing_obs=False
)
o_rd.plot(figsize=(16, 4), ax=axes[0])

o_rd_filled = hpd.PrecipitationObs.from_knmi(
    "RD", stn=892, start="1972", end="2023", fill_missing_obs=True
)

o_rd_filled.loc[o_rd_filled["station"] == "892", "RD"].plot(
    ax=axes[1], label="oorspronkelijke metingen"
)
o_rd_filled.loc[o_rd_filled["station"] != "892", "RD"].plot(
    ax=axes[1], color="orange", label="opgevulde metingen"
)
axes[0].set_title("precipitation Giersbergen (1972-2023)")
axes[1].legend();

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 892 and variable RD from 1972-01-01 to 2023-01-01
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 892 and variable RD from 1972-01-01 to 2023-01-01
INFO:hydropandas.io.knmi._add_missing_indices:station 892 has no measurements before 1993-11-01 09:00:00
INFO:hydropandas.io.knmi.fill_missing_measurements:Filled 7975 observations from station 827 TILBURG -> 892 GIERSBERGEN
../_images/examples_02_knmi_observations_16_1.png 
[10]:

# see the station_opvulwaarde
display(o_rd_filled.head())

hydropandas.PrecipitationObs

RD_GIERSBERGEN_892
unit m
y 407500.0
source KNMI
x 138500.0
location GIERSBERGEN
station 892
crs EPSG:28992
meteo_var RD
filename

RD station
1972-01-01 09:00:00 0.0 827
1972-01-02 09:00:00 0.0 827
1972-01-03 09:00:00 0.0 827
1972-01-04 09:00:00 0.0 827
1972-01-05 09:00:00 0.0 827 
[11]:

# example 3 get evaporation
logging.getLogger().getEffectiveLevel()
logging.getLogger().setLevel(logging.INFO)

o_ev = hpd.EvaporationObs.from_knmi(
    stn=344, start="1972", end="2023", fill_missing_obs=True
)
o_ev

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable EV24 from 1972-01-01 to 2023-01-01
INFO:hydropandas.io.knmi._add_missing_indices:station 344 has no measurements before 1987-09-12 01:00:00
INFO:hydropandas.io.knmi.fill_missing_measurements:Filled 246 observations from station 210 VALKENBURG -> 344 ROTTERDAM
INFO:hydropandas.io.knmi.fill_missing_measurements:Filled 64 observations from station 348 CABAUW-MAST -> 344 ROTTERDAM
INFO:hydropandas.io.knmi.fill_missing_measurements:Filled 5499 observations from station 260 DE-BILT -> 344 ROTTERDAM

[11]:

hydropandas.EvaporationObs

EV24_ROTTERDAM_344
unit m
y 441636.854285
source KNMI
x 90061.930891
location ROTTERDAM
station 344
crs EPSG:28992
meteo_var EV24
filename

EV24 station
1972-01-01 01:00:00 0.0002 260
1972-01-02 01:00:00 0.0002 260
1972-01-03 01:00:00 0.0002 260
1972-01-04 01:00:00 0.0000 260
1972-01-05 01:00:00 0.0000 260
... ... ...
2022-12-28 01:00:00 0.0003 344
2022-12-29 01:00:00 0.0001 344
2022-12-30 01:00:00 0.0002 344
2022-12-31 01:00:00 0.0001 344
2023-01-01 01:00:00 0.0001 344

18629 rows × 2 columns

Get ObsCollections

You can read multiple Observation objects at once using the hpd.read_knmi method. The observations are stored in an ObsCollection object. Below an example to obtain precipitation (RH) and evaporation (EV24) from the measurement stations Rotterdam (344) and De Bilt (260).

[12]:

oc = hpd.read_knmi(stns=[344, 260], meteo_vars=["RH", "EV24"])
oc

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable RH from None to None
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable RH from None to None
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable EV24 from None to None
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable EV24 from None to None

[12]:
unit y source x location station meteo_var filename obs
name
RH_ROTTERDAM_344 m 441636.854285 KNMI 90061.930891 ROTTERDAM 344 RH PrecipitationObs RH_ROTTERDAM_344 -----metadat...
RH_DE-BILT_260 m 456790.999119 KNMI 140565.152506 DE-BILT 260 RH PrecipitationObs RH_DE-BILT_260 -----metadata-...
EV24_ROTTERDAM_344 m 441636.854285 KNMI 90061.930891 ROTTERDAM 344 EV24 EvaporationObs EV24_ROTTERDAM_344 -----metadat...
EV24_DE-BILT_260 m 456790.999119 KNMI 140565.152506 DE-BILT 260 EV24 EvaporationObs EV24_DE-BILT_260 -----metadata-...

other options in the read_knmi function are:

  • specify locations as a dataframe with x, y coordinates (RD_new), the function will find the nearest KNMI station for every location.

  • specify xmid and ymid which are 2 arrays corresponding to a structured grid to obtain the nearest KNMI station for every cell in the grid.

[13]:

locations = pd.DataFrame(index=["Rotterdam"], data={"x": 90600, "y": 442800})
display(locations)
hpd.read_knmi(locations=locations, meteo_vars=["RH"])
x y
Rotterdam 90600 442800 
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable RH from None to None

[13]:
unit y source x location station meteo_var filename obs
name
RH_ROTTERDAM_344 m 441636.854285 KNMI 90061.930891 ROTTERDAM 344 RH PrecipitationObs RH_ROTTERDAM_344 -----metadat... 
[14]:

hpd.read_knmi(xy=((90600, 442800),), meteo_vars=["RH"])

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable RH from None to None

[14]:
unit y source x location station meteo_var filename obs
name
RH_ROTTERDAM_344 m 441636.854285 KNMI 90061.930891 ROTTERDAM 344 RH PrecipitationObs RH_ROTTERDAM_344 -----metadat...

Precipitation

Using hydropandas 3 different precipitation products can be accessed:

  1. Daily data from a meteorological station

  2. Daily data from a neerslag (precipitation) station

  3. Hourly data from a meteorological station

All three products can be obtained using the from_knmi method. Product 1 and 2 can also be accessed without the api.

By default data is used from a meteorological station. Specify meteo_var='RD' to access data from a neerslag (precipitation) station.

[15]:

start = "2010-1-1"
end = "2010-1-10"

# daily meteo station (default)
precip1 = hpd.PrecipitationObs.from_knmi(stn=260, start=start, end=end)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable RH from 2010-01-01 to 2010-01-10

[16]:

# daily neerslag station
precip2 = hpd.PrecipitationObs.from_knmi(meteo_var="RD", stn=550, start=start, end=end)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 550 and variable RD from 2010-01-01 to 2010-01-10

[17]:

hpd.PrecipitationObs.from_knmi(
    stn=260, start="2026-1-1", end="2026-1-3", interval="hourly"
)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable RH from 2026-01-01 to 2026-01-03

[17]:

hydropandas.PrecipitationObs

RH_DE-BILT_260
unit m
y 456790.999119
source KNMI
x 140565.152506
location DE-BILT
station 260
crs EPSG:28992
meteo_var RH
filename

RH
2026-01-01 00:00:00 0.0000
2026-01-01 01:00:00 0.0000
2026-01-01 02:00:00 0.0000
2026-01-01 03:00:00 0.0000
2026-01-01 04:00:00 0.0000
2026-01-01 05:00:00 0.0000
2026-01-01 06:00:00 0.0000
2026-01-01 07:00:00 0.0000
2026-01-01 08:00:00 0.0001
2026-01-01 09:00:00 0.0003
2026-01-01 10:00:00 0.0014
2026-01-01 11:00:00 0.0017
2026-01-01 12:00:00 0.0002
2026-01-01 13:00:00 0.0000
2026-01-01 14:00:00 0.0000
2026-01-01 15:00:00 0.0002
2026-01-01 16:00:00 0.0004
2026-01-01 17:00:00 0.0000
2026-01-01 18:00:00 0.0000
2026-01-01 19:00:00 0.0000
2026-01-01 20:00:00 0.0001
2026-01-01 21:00:00 0.0000
2026-01-01 22:00:00 0.0001
2026-01-01 23:00:00 0.0013
2026-01-02 00:00:00 0.0006
2026-01-02 01:00:00 0.0007
2026-01-02 02:00:00 0.0010
2026-01-02 03:00:00 0.0015
2026-01-02 04:00:00 0.0005
2026-01-02 05:00:00 0.0012
2026-01-02 06:00:00 0.0021
2026-01-02 07:00:00 0.0017
2026-01-02 08:00:00 0.0015
2026-01-02 09:00:00 0.0011
2026-01-02 10:00:00 0.0004
2026-01-02 11:00:00 0.0002
2026-01-02 12:00:00 0.0004
2026-01-02 13:00:00 0.0002
2026-01-02 14:00:00 0.0005
2026-01-02 15:00:00 0.0000
2026-01-02 16:00:00 0.0001
2026-01-02 17:00:00 0.0000
2026-01-02 18:00:00 0.0000
2026-01-02 19:00:00 0.0000
2026-01-02 20:00:00 0.0001
2026-01-02 21:00:00 0.0005
2026-01-02 22:00:00 0.0000
2026-01-02 23:00:00 0.0000
2026-01-03 00:00:00 0.0001 
[18]:

# hourly meteo station (only works with api)
precip3 = hpd.PrecipitationObs.from_knmi(
    stn=260,
    start=start,
    end=end,
    interval="hourly",
)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable RH from 2010-01-01 to 2010-01-10

[19]:

# daily meteo station without api
precip4 = hpd.PrecipitationObs.from_knmi(
    stn=260,
    start=start,
    end=end,
    use_api=False,
)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable RH from 2010-01-01 to 2010-01-10

[20]:

# daily neerslag station without api
precip5 = hpd.PrecipitationObs.from_knmi(
    meteo_var="RD",
    stn=550,
    start=start,
    end=end,
    use_api=False,
)

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 550 and variable RD from 2010-01-01 to 2010-01-10

Below are the differences between the precipitation estimates from different station types.

[21]:

fig, ax = plt.subplots(figsize=(16, 4))
precip1["RH"].plot(
    ax=ax,
    drawstyle="steps",
    ls="--",
    lw=3,
    label=str(precip1.station) + "_dagelijks",
)

precip2["RD"].plot(
    ax=ax,
    drawstyle="steps",
    ls="--",
    lw=3,
    label=str(precip2.station) + "_dagelijks",
)

precip3["RH"].plot(
    ax=ax,
    drawstyle="steps",
    label=str(precip3.station) + "_uurlijks",
)

precip4["RH"].plot(
    ax=ax,
    drawstyle="steps",
    marker="o",
    label=str(precip4.station) + "_dagelijks_geen_api",
)

precip5["RD"].plot(
    ax=ax,
    drawstyle="steps",
    marker="o",
    label=str(precip5.station) + "_dagelijks_geen_api",
)


ax.legend()
ax.grid()
ax.set_ylabel("neerslag [m/dag]");
../_images/examples_02_knmi_observations_32_0.png

The locations of the stations can be plotted onto a map using the contextily package.

[22]:

import contextily as cx

oc = hpd.ObsCollection([precip1, precip2])

gdf = oc.to_gdf()

gdf = gdf.set_crs(28992)

gdf["name"] = gdf.index

ax = gdf.buffer(2000).plot(alpha=0, figsize=(8, 8))

gdf.plot("name", ax=ax, cmap="jet", legend=True, markersize=100)


cx.add_basemap(ax, crs=28992)
../_images/examples_02_knmi_observations_34_0.png

KNMI climate scenarios

You can read the transformed KNMI series for the ‘KNMI ‘23 Klimaatscenario’s’ using hpd.read_knmi_scenarios(). This function downloads all available data for one station, but can also be limited to specific variables, years and scenarios.

[23]:

# download all scenarios for station 550 and meteo variable TG
oc = hpd.read_knmi_scenarios(550, years=["2050"], meteo_vars=["TG"])

# plot all scenarios
f, ax = plt.subplots(figsize=(16, 4))
for o in oc.obs.values:
    o.loc["2020", o.meteo_var].plot(label=o.name[-2:], ax=ax, alpha=0.5)
ax.legend()
ax.set_title(f"{o.name[:-3]} scenarios")
ax.set_ylabel(o.unit)

---------------------------------------------------------------------------
HTTPError                                 Traceback (most recent call last)
Cell In[23], line 2
      1 # download all scenarios for station 550 and meteo variable TG
----> 2 oc = hpd.read_knmi_scenarios(550, years=["2050"], meteo_vars=["TG"])
      3
      4 # plot all scenarios
      5 f, ax = plt.subplots(figsize=(16, 4))

File ~/checkouts/readthedocs.org/user_builds/hydropandas/envs/stable/lib/python3.12/site-packages/hydropandas/obs_collection.py:855, in read_knmi_scenarios(stn, years, scenarios, evap, meteo_vars, name)
    793 def read_knmi_scenarios(
    794     stn: int | str,
    795     years: Iterable[Literal["2033", "2050", "2100", "2150"]] = (
   (...)    812     name: str = "",
    813 ):
    814     """Get KNMI climate scenario observations for a station.
    815
    816     Retrieves climate scenario data from KNMI and returns an ObsCollection
   (...)    853     ... )
    854     """
--> 855     oc = ObsCollection.from_knmi_scenarios(
    856         stn=stn,
    857         years=years,
    858         scenarios=scenarios,
    859         evap=evap,
    860         meteo_vars=meteo_vars,
    861         name=name,
    862     )
    864     return oc

File ~/checkouts/readthedocs.org/user_builds/hydropandas/envs/stable/lib/python3.12/site-packages/hydropandas/obs_collection.py:2917, in ObsCollection.from_knmi_scenarios(cls, stn, years, scenarios, evap, meteo_vars, name)
   2914 from .observation import EvaporationObs, MeteoObs, PrecipitationObs
   2916 # Fetch and process climate scenario data
-> 2917 obs_list = get_knmi_scenarios_obs_list(
   2918     stn=stn,
   2919     years=years,
   2920     scenarios=scenarios,
   2921     evap=evap,
   2922     meteo_vars=meteo_vars,
   2923     ObsClass={
   2924         "RD": PrecipitationObs,
   2925         "TG": MeteoObs,
   2926         "Q": MeteoObs,
   2927         "TX": MeteoObs,
   2928         "TN": MeteoObs,
   2929         "UG": MeteoObs,
   2930         "FG": MeteoObs,
   2931         "EV24": EvaporationObs,
   2932     },
   2933 )
   2935 # Create and return observation collection
   2936 meta = {
   2937     "stn": str(stn),
   2938     "years": years,
   2939     "scenarios": scenarios,
   2940     "evaporation_method": evap,
   2941 }

File ~/checkouts/readthedocs.org/user_builds/hydropandas/envs/stable/lib/python3.12/site-packages/hydropandas/io/knmi.py:2652, in get_knmi_scenarios_obs_list(stn, years, scenarios, evap, meteo_vars, ObsClass)
   2647     raise ValueError(
   2648         "ObsClass must be provided to map variables to observation classes."
   2649     )
   2651 # Get measurements data
-> 2652 dfs = get_knmi_scenarios_data(
   2653     stn=stn,
   2654     years=years,
   2655     scenarios=scenarios,
   2656     evap=evap,
   2657 )
   2659 units = {
   2660     "TG": "°C",
   2661     "RD": "m/day",
   (...)   2667     "EV24": "m/day",
   2668 }
   2669 meteo_vars = list(units) if meteo_vars is None else meteo_vars

File ~/checkouts/readthedocs.org/user_builds/hydropandas/envs/stable/lib/python3.12/site-packages/hydropandas/io/knmi.py:2537, in get_knmi_scenarios_data(stn, years, scenarios, evap)
   2535 # Download data from KNMI API
   2536 response = requests.get(URL_KNMI_TRANSFORMED_SERIES, params=params)
-> 2537 response.raise_for_status()
   2538 zipped = ZipFile(BytesIO(response.content))
   2540 # Read and process raw CSV files

File ~/checkouts/readthedocs.org/user_builds/hydropandas/envs/stable/lib/python3.12/site-packages/requests/models.py:1167, in Response.raise_for_status(self)
   1162     http_error_msg = (
   1163         f"{self.status_code} Server Error: {reason} for url: {self.url}"
   1164     )
   1166 if http_error_msg:
-> 1167     raise HTTPError(http_error_msg, response=self)

HTTPError: 422 Client Error: Unknown for url: https://klimaatscenarios-data.knmi.nl/api/v1/climate-series-data.zip?series_variables%5Bscenarios%5D%5B%5D=Ld&series_variables%5Bscenarios%5D%5B%5D=Ln&series_variables%5Bscenarios%5D%5B%5D=Md&series_variables%5Bscenarios%5D%5B%5D=Mn&series_variables%5Bscenarios%5D%5B%5D=Hd&series_variables%5Bscenarios%5D%5B%5D=Hn&series_variables%5Byears%5D%5B%5D=2050&series_variables%5Bstation%5D=550_De-Bilt_utrecht&series_variables%5Bdate_range%5D%5B%5D=1991-01-01&series_variables%5Bdate_range%5D%5B%5D=2020-12-31&series_variables%5Bclimate_variables%5D=temp

Evaporation

KNMI provides the Makking reference evaporation (meteo_var EV24). Hydropandas provides a posssibility to calculate three different types of reference evaporation from data of KNMI meteo stations:

  • Penman

  • Hargreaves

  • Makkink (in the same way as KNMI)

These three types of reference evaporation are calculated the same way as described by Allen et al. 1990 and STOWA rapport. Be aware that the last report is written in Dutch and contains errors in the units.

The following variables from the KNMI are used for each reference evaporation type:

  • Penman: average (TG), minimum (TN) and maximum (TX) temperature, de global radiation (Q), de windspeed (FG) en de relative humidity (PG).

  • Hargreaves: average (TG), minimum (TN) and maximum (TX) temperature

  • Makkink: average temperature (TG) and global radiation (Q)

Comparison Makkink

Lets compare Hypdropandas Makkink verdamping evaporation with the EV24 Makkink verdamping of the KNMI. When Hydropandas Makkink evaporation is rounded (on 4 decimals), the estimate is the same as for the KNMI estimate.

[24]:

ev24 = hpd.EvaporationObs.from_knmi(
    stn=260, start="2022-1-1"
)  # et_type='EV24' by default
makk = hpd.EvaporationObs.from_knmi(meteo_var="makkink", stn=260, start="2022-1-1")

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable EV24 from 2022-01-01 to None
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable makkink from 2022-01-01 to None

[25]:

f, ax = plt.subplots(2, figsize=(11, 4))
ax[0].plot(ev24, label=ev24.name)
ax[0].plot(makk.round(4), label=makk.name)
ax[0].set_ylabel("E [m/d]")
ax[0].set_title("Makkink evaporation")
ax[0].legend()
ax[1].plot(ev24["EV24"] - makk["makkink"].round(4))
ax[1].set_title("Difference Makkink KNMI and Hydropandas")
f.tight_layout()
../_images/examples_02_knmi_observations_40_0.png

Comparison Penman, Makkink en Hargreaves

On average Penman gives a higher estimate for reference evaporation than Makkink (~0.55mm). This can be explained by the fact that Penman takes into account windspeed and Makkink ignores this proces. Hargreaves is a very simple way of estimation the evaporation, only taking into account temperature and extraterrestial radiation. Therefore it gives a lower estimate for the reference evporatoin compared to the two other methods (~-0.35mm wrt Makkink).

[26]:

penm = hpd.EvaporationObs.from_knmi(
    meteo_var="penman", stn=260, start="2022-1-1"
).squeeze()
harg = hpd.EvaporationObs.from_knmi(
    meteo_var="hargreaves", stn=260, start="2022-1-1"
).squeeze()

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable penman from 2022-01-01 to None
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable hargreaves from 2022-01-01 to None

[27]:

f, ax = plt.subplots(figsize=(11, 4))
ax.plot(makk, label=makk.name)
ax.plot(penm, label=penm.name)
ax.plot(harg, label=harg.name)
ax.legend()

[27]:

<matplotlib.legend.Legend at 0x79781f44b4d0>
../_images/examples_02_knmi_observations_43_1.png

Spatial interpolation

Does interpolation matter? There are ways to interpolate evaporation datasets. However currently the nearest station is always used in HydroPandas’ methods. Does this give different results? Lets look into spatial interpolation of Makkink Evaporation data.

Get all stations where EV24 is measured

[28]:

tmin = "1950-01-01"
tmax = "2022-04-11"

stns = knmi.get_stations(meteo_var="EV24", start=tmin, end=tmax).sort_index()

Collect all EV24 data ever measured by KNMI

[29]:

# empty dataframe
df = pd.DataFrame(columns=stns.index)

for stn in tqdm(stns.index):
    df_stn = hpd.MeteoObs.from_knmi(
        meteo_var="EV24", stn=stn, fill_missing_obs=False, start=tmin, end=tmax
    )
    df[stn] = df_stn

df

  0%|          | 0/34 [00:00<?, ?it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 210 and variable EV24 from 1950-01-01 to 2022-04-11

  3%|▎         | 1/34 [00:00<00:27,  1.20it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 215 and variable EV24 from 1950-01-01 to 2022-04-11

  6%|▌         | 2/34 [00:01<00:18,  1.74it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 235 and variable EV24 from 1950-01-01 to 2022-04-11

  9%|▉         | 3/34 [00:02<00:22,  1.37it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 240 and variable EV24 from 1950-01-01 to 2022-04-11

 12%|█▏        | 4/34 [00:03<00:24,  1.22it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 249 and variable EV24 from 1950-01-01 to 2022-04-11

 15%|█▍        | 5/34 [00:03<00:21,  1.37it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 251 and variable EV24 from 1950-01-01 to 2022-04-11

 18%|█▊        | 6/34 [00:04<00:19,  1.47it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 257 and variable EV24 from 1950-01-01 to 2022-04-11

 21%|██        | 7/34 [00:04<00:17,  1.56it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable EV24 from 1950-01-01 to 2022-04-11

 24%|██▎       | 8/34 [00:05<00:18,  1.40it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 265 and variable EV24 from 1950-01-01 to 2022-04-11

 26%|██▋       | 9/34 [00:06<00:18,  1.36it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 267 and variable EV24 from 1950-01-01 to 2022-04-11

 29%|██▉       | 10/34 [00:07<00:17,  1.40it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 269 and variable EV24 from 1950-01-01 to 2022-04-11

 32%|███▏      | 11/34 [00:07<00:16,  1.44it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 270 and variable EV24 from 1950-01-01 to 2022-04-11

 35%|███▌      | 12/34 [00:08<00:16,  1.30it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 273 and variable EV24 from 1950-01-01 to 2022-04-11

 38%|███▊      | 13/34 [00:09<00:15,  1.39it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 275 and variable EV24 from 1950-01-01 to 2022-04-11

 41%|████      | 14/34 [00:10<00:15,  1.28it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 277 and variable EV24 from 1950-01-01 to 2022-04-11

 44%|████▍     | 15/34 [00:10<00:13,  1.38it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 278 and variable EV24 from 1950-01-01 to 2022-04-11

 47%|████▋     | 16/34 [00:11<00:12,  1.45it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 279 and variable EV24 from 1950-01-01 to 2022-04-11

 50%|█████     | 17/34 [00:12<00:11,  1.46it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 280 and variable EV24 from 1950-01-01 to 2022-04-11

 53%|█████▎    | 18/34 [00:13<00:12,  1.30it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 283 and variable EV24 from 1950-01-01 to 2022-04-11

 56%|█████▌    | 19/34 [00:13<00:11,  1.35it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 286 and variable EV24 from 1950-01-01 to 2022-04-11

 59%|█████▉    | 20/34 [00:14<00:09,  1.42it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 290 and variable EV24 from 1950-01-01 to 2022-04-11

 62%|██████▏   | 21/34 [00:15<00:09,  1.32it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 310 and variable EV24 from 1950-01-01 to 2022-04-11

 65%|██████▍   | 22/34 [00:16<00:09,  1.24it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 319 and variable EV24 from 1950-01-01 to 2022-04-11

 68%|██████▊   | 23/34 [00:17<00:08,  1.23it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 323 and variable EV24 from 1950-01-01 to 2022-04-11

 71%|███████   | 24/34 [00:17<00:07,  1.30it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 330 and variable EV24 from 1950-01-01 to 2022-04-11

 74%|███████▎  | 25/34 [00:18<00:07,  1.27it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable EV24 from 1950-01-01 to 2022-04-11

 76%|███████▋  | 26/34 [00:19<00:06,  1.23it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 348 and variable EV24 from 1950-01-01 to 2022-04-11

 79%|███████▉  | 27/34 [00:20<00:05,  1.27it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 350 and variable EV24 from 1950-01-01 to 2022-04-11

 82%|████████▏ | 28/34 [00:20<00:04,  1.22it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 356 and variable EV24 from 1950-01-01 to 2022-04-11

 85%|████████▌ | 29/34 [00:21<00:03,  1.29it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 370 and variable EV24 from 1950-01-01 to 2022-04-11

 88%|████████▊ | 30/34 [00:22<00:03,  1.26it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 375 and variable EV24 from 1950-01-01 to 2022-04-11

 91%|█████████ | 31/34 [00:23<00:02,  1.19it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 377 and variable EV24 from 1950-01-01 to 2022-04-11

 94%|█████████▍| 32/34 [00:24<00:01,  1.29it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 380 and variable EV24 from 1950-01-01 to 2022-04-11

 97%|█████████▋| 33/34 [00:25<00:00,  1.20it/s]

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 391 and variable EV24 from 1950-01-01 to 2022-04-11

100%|██████████| 34/34 [00:25<00:00,  1.33it/s]

[29]:
210 215 235 240 249 251 257 260 265 267 ... 330 344 348 350 356 370 375 377 380 391
YYYYMMDD
1987-03-26 01:00:00 0.0006 NaN 0.0006 NaN NaN NaN NaN 0.0005 NaN NaN ... NaN NaN NaN NaN NaN 0.0008 NaN NaN 0.0010 NaN
1987-03-27 01:00:00 0.0016 NaN 0.0015 NaN NaN NaN NaN 0.0016 NaN NaN ... NaN NaN 0.0016 NaN NaN 0.0017 NaN NaN 0.0024 NaN
1987-03-28 01:00:00 0.0008 NaN 0.0007 NaN NaN NaN NaN 0.0007 NaN NaN ... NaN NaN 0.0007 NaN NaN 0.0005 NaN NaN 0.0008 NaN
1987-03-29 01:00:00 0.0013 NaN 0.0007 NaN NaN NaN NaN 0.0010 NaN NaN ... NaN NaN NaN NaN NaN 0.0013 NaN NaN 0.0014 NaN
1987-03-30 01:00:00 0.0019 NaN 0.0021 NaN NaN NaN NaN 0.0016 NaN NaN ... NaN NaN 0.0017 NaN NaN 0.0015 NaN NaN 0.0018 NaN
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
2016-04-29 01:00:00 0.0023 0.0022 0.0020 0.0020 0.0015 0.0018 0.0014 0.0022 NaN 0.0021 ... 0.0023 0.0026 0.0023 0.0018 0.0022 0.0024 0.0019 0.0025 0.0025 0.0023
2016-04-30 01:00:00 0.0023 0.0021 0.0025 0.0020 0.0022 0.0027 0.0022 0.0014 NaN 0.0021 ... 0.0025 0.0021 0.0016 0.0014 0.0012 0.0015 0.0014 0.0010 0.0010 0.0009
2016-05-01 01:00:00 0.0023 0.0022 0.0029 0.0022 0.0021 0.0028 0.0026 0.0023 NaN 0.0026 ... 0.0027 0.0025 0.0022 0.0021 0.0021 0.0022 0.0021 0.0009 0.0011 0.0015
2016-05-02 01:00:00 0.0036 0.0035 0.0036 0.0034 0.0034 0.0035 0.0035 0.0035 NaN 0.0034 ... 0.0037 0.0036 0.0036 0.0035 0.0034 0.0031 0.0030 0.0029 0.0031 0.0031
2016-05-03 01:00:00 0.0029 0.0028 0.0022 0.0029 0.0028 0.0026 0.0027 0.0034 NaN 0.0030 ... 0.0026 0.0031 0.0033 0.0034 0.0034 0.0035 0.0034 0.0034 0.0036 0.0035

10632 rows × 34 columns

[30]:

df_stn

[30]:

hydropandas.MeteoObs

EV24_ARCEN_391
unit m
y 390120.746329
source KNMI
x 211170.177271
location ARCEN
station 391
crs EPSG:28992
meteo_var EV24
filename

EV24
YYYYMMDD
1991-02-13 01:00:00 0.0003
1991-02-14 01:00:00 0.0003
1991-02-15 01:00:00 0.0005
1991-02-16 01:00:00 0.0001
1991-02-17 01:00:00 0.0005
... ...
2022-04-07 01:00:00 0.0005
2022-04-08 01:00:00 0.0015
2022-04-09 01:00:00 0.0012
2022-04-10 01:00:00 0.0018
2022-04-11 01:00:00 0.0024

11381 rows × 1 columns

According to the KNMI, thin plate spline is the best way to interpolate Makkink evaporation. Thats also how they provide the gridded Makkink evaporation :

[31]:

xy = stns.loc[df.columns, ["x", "y"]]

for idx in tqdm(df.index[0 : len(df) : 2000]):
    # get all stations with values for this date
    val = df.loc[idx].dropna() * 1000  # mm
    # get stations for this date
    coor = xy.loc[val.index].to_numpy()
    if (
        len(val) < 3
    ):  # if there are less than 3 stations, thin plate spline does not work
        # options: linear, multiquadric, gaussian,
        kernel = "linear"

    else:
        kernel = "thin_plate_spline"
        # options:
        # 'inverse_quadratic', 'linear', 'multiquadric', 'gaussian',
        # 'inverse_multiquadric', 'cubic', 'quintic', 'thin_plate_spline'

    # create an scipy interpolator
    rbf = RBFInterpolator(coor, val.to_numpy(), epsilon=1, kernel=kernel)

    nea = NearestNDInterpolator(coor, val.to_numpy())

    # interpolate on grid of the Netherlands
    grid = np.mgrid[10000:280000:100j, 300000:620000:100j]
    grid2 = grid.reshape(2, -1).T  # interpolator only takes array [[x0, y0],
    #  [x1, y1]]
    val_rbf = rbf.__call__(grid2).reshape(100, 100)
    val_nea = nea.__call__(grid2).reshape(100, 100)

    # create figure
    fig, ax = plt.subplot_mosaic("AAAABBBBC", figsize=(10, 5.925))
    fig.suptitle(f"Makkink Evaporation [mm] {idx.date()}", y=0.95)
    vmin = 0
    vmax = 5

    ax["A"].set_title(f"Interpolation: {kernel}")
    ax["A"].pcolormesh(grid[0], grid[1], val_rbf, vmin=vmin, vmax=vmax)
    ax["B"].set_title("Interpolation: Nearest")
    ax["B"].pcolormesh(grid[0], grid[1], val_nea, vmin=vmin, vmax=vmax)
    ax["A"].scatter(*coor.T, c=val, s=100, ec="k", vmin=vmin, vmax=vmax)
    p = ax["B"].scatter(*coor.T, c=val, s=100, ec="k", vmin=vmin, vmax=vmax)
    cb = fig.colorbar(p, cax=ax["C"])
    cb.set_label("[mm]")
    fig.tight_layout()

100%|██████████| 6/6 [00:00<00:00,  8.34it/s]
../_images/examples_02_knmi_observations_51_1.png
../_images/examples_02_knmi_observations_51_2.png
../_images/examples_02_knmi_observations_51_3.png
../_images/examples_02_knmi_observations_51_4.png
../_images/examples_02_knmi_observations_51_5.png
../_images/examples_02_knmi_observations_51_6.png

The same method is implemented in Hydropandas for an ObsCollection.

[32]:

sd = "2022-01-01"
ed = "2022-12-31"
oc = hpd.read_knmi(
    stns=stns.index, starts=sd, ends=ed, meteo_vars=["EV24"], raise_exceptions=False
)
oc_et = oc.interpolate(xy=[(100000, 330000)])
eti = oc_et.iloc[0].obs
eti

INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 210 and variable EV24 from 2022-01-01 to 2022-12-31
WARNING:hydropandas.io.knmi.parse_data:No columns to parse from file. Returning empty DataFrame.
WARNING:hydropandas.io.knmi.get_timeseries_stn:No data for meteo_var='EV24' at stn=210 betweenstart=Timestamp('2022-01-01 00:00:00') and end=Timestamp('2022-12-31 00:00:00').
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 215 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 235 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 240 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 249 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 251 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 257 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 260 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 265 and variable EV24 from 2022-01-01 to 2022-12-31
WARNING:hydropandas.io.knmi.parse_data:No columns to parse from file. Returning empty DataFrame.
WARNING:hydropandas.io.knmi.get_timeseries_stn:No data for meteo_var='EV24' at stn=265 betweenstart=Timestamp('2022-01-01 00:00:00') and end=Timestamp('2022-12-31 00:00:00').
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 267 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 269 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 270 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 273 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 275 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 277 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 278 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 279 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 280 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 283 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 286 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 290 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 310 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 319 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 323 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 330 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 344 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 348 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 350 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 356 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 370 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 375 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 377 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 380 and variable EV24 from 2022-01-01 to 2022-12-31
INFO:hydropandas.io.knmi.get_knmi_obs:get data from station 391 and variable EV24 from 2022-01-01 to 2022-12-31

[32]:

hydropandas.EvaporationObs

100000_330000
unit
y 330000
source interpolation
x 100000
location
station NaN
crs
meteo_var EV24
filename

100000_330000
YYYYMMDD
2022-01-01 01:00:00 0.000254
2022-01-02 01:00:00 0.000570
2022-01-03 01:00:00 0.000330
2022-01-04 01:00:00 0.000142
2022-01-05 01:00:00 0.000157
... ...
2022-12-27 01:00:00 0.000151
2022-12-28 01:00:00 0.000260
2022-12-29 01:00:00 0.000101
2022-12-30 01:00:00 0.000141
2022-12-31 01:00:00 0.000077

365 rows × 1 columns

[33]:

etn = hpd.MeteoObs.from_knmi(
    xy=(100000, 330000), start=sd, end=ed, meteo_var="EV24", fill_missing_obs=True
)
etn

INFO:hydropandas.io.knmi.get_knmi_obs:get KNMI data from station nearest to coordinates (100000, 330000) and meteovariable EV24

[33]:

hydropandas.MeteoObs

EV24_WESTDORPE_319
unit m
y 360618.713456
source KNMI
x 48425.362049
location WESTDORPE
station 319
crs EPSG:28992
meteo_var EV24
filename

EV24 station
2022-01-01 01:00:00 0.0002 319
2022-01-02 01:00:00 0.0005 319
2022-01-03 01:00:00 0.0004 319
2022-01-04 01:00:00 0.0002 319
2022-01-05 01:00:00 0.0002 319
... ... ...
2022-12-27 01:00:00 0.0003 319
2022-12-28 01:00:00 0.0003 319
2022-12-29 01:00:00 0.0001 319
2022-12-30 01:00:00 0.0002 319
2022-12-31 01:00:00 0.0001 319

365 rows × 2 columns

As can be seen, for one location the interpolation method is significantly slower. Lets see how the values compare for a time series.

[34]:

fig, ax = plt.subplots(2, 1, figsize=(8, 6), sharex=True)
eti.plot(ax=ax[0])
etn.plot(ax=ax[0], linestyle="--", color="C1")
ax[0].set_title("Comparison Interpolated and Nearest Makkink Evaporation")
ax[0].set_ylabel("[mm]")
ax[0].grid()
ax[0].legend(["Interpolated", "Nearest"])

(eti.squeeze() - etn["EV24"].squeeze()).plot(ax=ax[1], color="C2")
ax[1].set_ylabel("[mm]")
ax[1].grid()
ax[1].legend(["Interpolated - Nearest"])

[34]:

<matplotlib.legend.Legend at 0x79781f4d7020>
../_images/examples_02_knmi_observations_56_1.png

The interpolated evaporation can also be collected for multiple points (using x and y in a list of DataFrame) in an ObsCollection

[35]:

oc_et = oc.interpolate(xy=[(100000, 320000), (100000, 330000), (100000, 340000)])
oc_et

[35]:
unit y source x location station meteo_var filename obs
name
100000_320000 320000 interpolation 100000 NaN EV24 EvaporationObs 100000_320000 -----metadata----...
100000_330000 330000 interpolation 100000 NaN EV24 EvaporationObs 100000_330000 -----metadata----...
100000_340000 340000 interpolation 100000 NaN EV24 EvaporationObs 100000_340000 -----metadata----...

The interpolation method is slow at first, but if collected for many different locations the time penalty is not that significant anymore.