Combining multiple Datasets

Objectives:

Show how to combine multiple ECCO v4 state estimate Datasets after loading.

Loading multiple Datasets

In previous tutorials we’ve loaded single lat-lon-cap NetCDF tile files for ECCO state estimate variables and model grid parameters. Here we will demonstrate merging the resulting Datasets together. Some benefits of merging Datasets include having a tidier workspace and simplying subsetting operations, the subject of a future tutorial.

First, we’ll load three ECCOv4 NetCDF state estimate variables and the model grid. For this exercise use the ECCOv4 NetCDF files in Format 2 (one NetCDF file corresponds to one variable and one year).

First let’s define our environment

[1]:

import numpy as np
import xarray as xr
import sys
import matplotlib.pyplot as plt
import json

[2]:

## Import the ecco_v4_py library into Python
## =========================================
#import ecco_v4_py as ecco

## -- If ecco_v4_py is not installed in your local Python library,
##    tell Python where to find it.  For example, if your ecco_v4_py
##    files are in /Users/ifenty/ECCOv4-py/ecco_v4_py, then use:

sys.path.append('/home/ifenty/ECCOv4-py')
import ecco_v4_py as ecco

[3]:

## Set top-level file directory for the ECCO NetCDF files
## =================================================================
# base_dir = '/home/username/'
base_dir = '/home/ifenty/ECCOv4-release'

## define a high-level directory for ECCO fields
ECCO_dir = base_dir + '/Release3_alt'

c point: SSH

[4]:

SSH_dir= ECCO_dir + '/nctiles_monthly/SSH/'
var = 'SSH'

# make use of the ``load_ecco_var_from_years_nc`` routine to
# load a single variable
ecco_dataset_A = ecco.load_ecco_var_from_years_nc(SSH_dir, \
                                                  var, \
                                                  tiles_to_load=[0,1,2,3],\
                                                  years_to_load=[2010])

to see the data variables in a dataset, use .data_vars:

[5]:

ecco_dataset_A.data_vars

[5]:

Data variables:
    SSH      (time, tile, j, i) float32 dask.array<chunksize=(12, 4, 90, 90), meta=np.ndarray>

As expected, ecco_dataset_A has one data variable, SSH, which has dimensions i, j, tile, and time. Its coordinates:

[6]:

ecco_dataset_A.SSH.coords

[6]:

Coordinates:
  * j        (j) int32 0 1 2 3 4 5 6 7 8 9 10 ... 80 81 82 83 84 85 86 87 88 89
  * i        (i) int32 0 1 2 3 4 5 6 7 8 9 10 ... 80 81 82 83 84 85 86 87 88 89
    XC       (tile, j, i) float32 dask.array<chunksize=(4, 90, 90), meta=np.ndarray>
    YC       (tile, j, i) float32 dask.array<chunksize=(4, 90, 90), meta=np.ndarray>
    rA       (tile, j, i) float32 dask.array<chunksize=(4, 90, 90), meta=np.ndarray>
  * tile     (tile) int32 0 1 2 3
    iter     (time) int32 dask.array<chunksize=(12,), meta=np.ndarray>
  * time     (time) datetime64[ns] 2010-01-16T12:00:00 ... 2010-12-16T12:00:00

u point: ADVx_TH

ADVx_TH is the horizontal advective flux of potential temperature in each tile’s x direction.

[7]:

ADVx_dir= ECCO_dir + '/nctiles_monthly/ADVx_TH/'
var = 'ADVx_TH'

# make use of the ``load_ecco_var_from_years_nc`` routine to
# load a single variable
ecco_dataset_B= ecco.load_ecco_var_from_years_nc(ADVx_dir, \
                                                 var, \
                                                 years_to_load=2010).load();
ecco_dataset_B.attrs=[]

ecco_dataset_B.data_vars

[7]:

Data variables:
    ADVx_TH  (time, tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0

ecco_dataset_A has one data variable, ADVx_TH, which has dimensions i_g, j, k tile, and time. ADVx_TH is a three-dimensional field.

Notice that the coordinates of ecco_dataset_B is distinct from ecco_dataset_A. Specifically, ecco_dataset_B has a k dimension, and several new non-dimension coords such as drF and dyG

[8]:

ecco_dataset_B.coords

[8]:

Coordinates:
  * i_g        (i_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * j          (j) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * k          (k) int32 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
    Z          (k) float32 -5.0 -15.0 -25.0 -35.0 ... -5039.25 -5461.25 -5906.25
    PHrefC     (k) float32 49.05 147.15 245.25 ... 49435.043 53574.863 57940.312
    drF        (k) float32 10.0 10.0 10.0 10.0 10.0 ... 387.5 410.5 433.5 456.5
    dxC        (tile, j, i_g) float32 15583.418 15588.104 ... 23406.256
    rAw        (tile, j, i_g) float32 361699460.0 362790240.0 ... 364760350.0
    dyG        (tile, j, i_g) float32 23210.262 23273.26 ... 15595.26 15583.685
    hFacW      (tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
  * tile       (tile) int32 0 1 2 3 4 5 6 7 8 9 10 11 12
    time_bnds  (time, nv) datetime64[ns] 2010-01-01 2010-02-01 ... 2011-01-01
    iter       (time) int32 158532 159204 159948 160668 ... 165084 165804 166548
  * time       (time) datetime64[ns] 2010-01-16T12:00:00 ... 2010-12-16T12:00:00

v point: ADVy_TH

ADVy_TH is the horizontal advective flux of potential temperature in each tile’s y direction.

[9]:

ADVy_dir= ECCO_dir + '/nctiles_monthly/ADVy_TH/'
var = 'ADVy_TH'

ecco_dataset_C= ecco.load_ecco_var_from_years_nc(ADVy_dir, \
                                                 var, \
                                                 years_to_load=2010).load();
ecco_dataset_C.attrs=[]
ecco_dataset_C.data_vars

[9]:

Data variables:
    ADVy_TH  (time, tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0

ecco_dataset_C has one data variable, ADVy_TH, which has dimensions i, j_g, k tile, and time. ADVy_TH is a three-dimensional field.

Examining the dimensions and coordinates of these Datasets

Each of our three Datasets contain a single DataArray. Each of these DataArray objects has different horizontal dimension labels.

  • i and j for SSH
  • i_g and j for ADVx_TH
  • i and j_g for ADVy_TH
[10]:

print(ecco_dataset_A.data_vars)
print(ecco_dataset_B.data_vars)
print(ecco_dataset_C.data_vars)

Data variables:
    SSH      (time, tile, j, i) float32 dask.array<chunksize=(12, 4, 90, 90), meta=np.ndarray>
Data variables:
    ADVx_TH  (time, tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
Data variables:
    ADVy_TH  (time, tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0

Merging multiple Datasets from state estimate variables

Using the xarray method merge we can create a single Dataset with multiple DataArrays.

[11]:

# merge together
ecco_dataset_ABC = xr.merge([ecco_dataset_A, ecco_dataset_B, ecco_dataset_C]).load()

Examining the merged Dataset

As before, let’s look at the contents of the new merged Dataset

[12]:

ecco_dataset_ABC

[12]:

<xarray.Dataset>
Dimensions:    (i: 90, i_g: 90, j: 90, j_g: 90, k: 50, nv: 2, tile: 13, time: 12)
Coordinates:
  * tile       (tile) int64 0 1 2 3 4 5 6 7 8 9 10 11 12
  * j          (j) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * i          (i) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
    XC         (tile, j, i) float32 -111.60647 -111.303 -110.94285 ... nan nan
    YC         (tile, j, i) float32 -88.24259 -88.382515 -88.52242 ... nan nan
    rA         (tile, j, i) float32 362256450.0 363300960.0 ... nan nan
    time_bnds  (time, nv) datetime64[ns] 2010-01-01 2010-02-01 ... 2011-01-01
    iter       (time) int32 158532 159204 159948 160668 ... 165084 165804 166548
  * time       (time) datetime64[ns] 2010-01-16T12:00:00 ... 2010-12-16T12:00:00
  * i_g        (i_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * k          (k) int32 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
    Z          (k) float32 -5.0 -15.0 -25.0 -35.0 ... -5039.25 -5461.25 -5906.25
    PHrefC     (k) float32 49.05 147.15 245.25 ... 49435.043 53574.863 57940.312
    drF        (k) float32 10.0 10.0 10.0 10.0 10.0 ... 387.5 410.5 433.5 456.5
    dxC        (tile, j, i_g) float32 15583.418 15588.104 ... 23406.256
    rAw        (tile, j, i_g) float32 361699460.0 362790240.0 ... 364760350.0
    dyG        (tile, j, i_g) float32 23210.262 23273.26 ... 15595.26 15583.685
    hFacW      (tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
  * j_g        (j_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
    rAs        (tile, j_g, i) float32 179944260.0 180486990.0 ... 364150620.0
    dxG        (tile, j_g, i) float32 15584.907 15589.316 ... 23142.107
    dyC        (tile, j_g, i) float32 11563.718 11593.785 ... 15578.138
    hFacS      (tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
Dimensions without coordinates: nv
Data variables:
    SSH        (time, tile, j, i) float32 0.0 0.0 0.0 0.0 ... nan nan nan nan
    ADVx_TH    (time, tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0
    ADVy_TH    (time, tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0

1. Dimensions

Dimensions:    (i: 90, i_g: 90, j: 90, j_g: 90, k: 50, nv: 2, tile: 13, time: 12)

ecco_dataset_merged is a container of Data Arrays and as such it lists all of the unique dimensions its Data Arrays. In other words, Dimensions shows all of the dimensions used by its variables.

2. Dimension Coordinates

Coordinates:
Coordinates:
  * j          (j) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * i          (i) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * tile       (tile) int32 0 1 2 3 4 5 6 7 8 9 10 11 12
  * time       (time) datetime64[ns] 2010-01-16T12:00:00 ... 2010-12-16T12:00:00
  * i_g        (i_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * k          (k) int32 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
  * j_g        (j_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89

Notice that the tile and time coordinates are unchanged. merge recognizes identical coordiantes and keeps them.

3. Non-Dimension Coordinates

Coordinates:
    XC         (tile, j, i) float32 -111.60647 -111.303 -110.94285 ... nan nan
    YC         (tile, j, i) float32 -88.24259 -88.382515 -88.52242 ... nan nan
    rA         (tile, j, i) float32 362256450.0 363300960.0 ... nan nan
    time_bnds  (time, nv) datetime64[ns] 2010-01-01 2010-02-01 ... 2011-01-01
    iter       (time) int32 158532 159204 159948 160668 ... 165084 165804 166548
    Z          (k) float32 -5.0 -15.0 -25.0 -35.0 ... -5039.25 -5461.25 -5906.25
    PHrefC     (k) float32 49.05 147.15 245.25 ... 49435.043 53574.863 57940.312
    drF        (k) float32 10.0 10.0 10.0 10.0 10.0 ... 387.5 410.5 433.5 456.5
    dxC        (tile, j, i_g) float32 15583.418 15588.104 ... 23406.256
    rAw        (tile, j, i_g) float32 361699460.0 362790240.0 ... 364760350.0
    dyG        (tile, j, i_g) float32 23210.262 23273.26 ... 15595.26 15583.685
    hFacW      (tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
    rAs        (tile, j_g, i) float32 179944260.0 180486990.0 ... 364150620.0
    dxG        (tile, j_g, i) float32 15584.907 15589.316 ... 23142.107
    dyC        (tile, j_g, i) float32 11563.718 11593.785 ... 15578.138
    hFacS      (tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0

The list of non-dimension coordinates is now much longer. Like Dimensions, the non-dimension coordinates of the merged Dataset contain all of the non-dimension coordinates of the Data Arrays.

4. Attributes

Notice that all of the high level Dataset attributes are gone! Each of the three Datasets had different attributes and the merge routine simply drops them. The attributes of the Data variables remain intact:

[13]:

# (this json command makes Python dictionaries easier to read)
print(json.dumps(ecco_dataset_ABC.SSH.attrs, indent=2,sort_keys=True))

{
  "long_name": "Surface Height Anomaly adjusted with global steric height change and sea-ice load",
  "standard_name": "sea_surface_height",
  "units": "m"
}

Adding the model grid Dataset

Let’s use the merge routine to combine a Dataset of the model grid parameters with output_merged.

Load the model grid parameters

[14]:

# Load the llc90 grid parameters
grid_dir= ECCO_dir + '/nctiles_grid/'
grid_dataset = ecco.load_ecco_grid_nc(grid_dir, 'ECCOv4r3_grid.nc')
grid_dataset.coords

[14]:

Coordinates:
  * i          (i) int64 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * i_g        (i_g) int64 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * j          (j) int64 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * j_g        (j_g) int64 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * k          (k) int64 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
  * k_u        (k_u) int64 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
  * k_l        (k_l) int64 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
  * k_p1       (k_p1) int64 0 1 2 3 4 5 6 7 8 9 ... 42 43 44 45 46 47 48 49 50
  * tile       (tile) int64 0 1 2 3 4 5 6 7 8 9 10 11 12
    XC         (tile, j, i) float32 -111.60647 -111.303 ... -111.86579
    YC         (tile, j, i) float32 -88.24259 -88.382515 ... -88.07871 -88.10267
    XG         (tile, j_g, i_g) float32 -115.0 -115.0 ... -102.928925 -108.95171
    YG         (tile, j_g, i_g) float32 -88.17569 -88.31587 ... -88.02409
    CS         (tile, j, i) float32 0.06157813 0.06675376 ... -0.9983638
    SN         (tile, j, i) float32 -0.99810225 -0.9977695 ... -0.057182025
    Z          (k) float32 -5.0 -15.0 -25.0 -35.0 ... -5039.25 -5461.25 -5906.25
    Zp1        (k_p1) float32 0.0 -10.0 -20.0 -30.0 ... -5244.5 -5678.0 -6134.5
    Zu         (k_u) float32 -10.0 -20.0 -30.0 -40.0 ... -5244.5 -5678.0 -6134.5
    Zl         (k_l) float32 0.0 -10.0 -20.0 -30.0 ... -4834.0 -5244.5 -5678.0
    rA         (tile, j, i) float32 362256450.0 363300960.0 ... 361119100.0
    dxG        (tile, j_g, i) float32 15584.907 15589.316 ... 23142.107
    dyG        (tile, j, i_g) float32 23210.262 23273.26 ... 15595.26 15583.685
    Depth      (tile, j, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0 0.0
    rAz        (tile, j_g, i_g) float32 179944260.0 180486990.0 ... 364150620.0
    dxC        (tile, j, i_g) float32 15583.418 15588.104 ... 23406.256
    dyC        (tile, j_g, i) float32 11563.718 11593.785 ... 15578.138
    rAw        (tile, j, i_g) float32 361699460.0 362790240.0 ... 364760350.0
    rAs        (tile, j_g, i) float32 179944260.0 180486990.0 ... 364150620.0
    drC        (k_p1) float32 5.0 10.0 10.0 10.0 ... 399.0 422.0 445.0 228.25
    drF        (k) float32 10.0 10.0 10.0 10.0 10.0 ... 387.5 410.5 433.5 456.5
    PHrefC     (k) float32 49.05 147.15 245.25 ... 49435.043 53574.863 57940.312
    PHrefF     (k_p1) float32 0.0 98.1 196.2 ... 51448.547 55701.18 60179.445
    hFacC      (k, tile, j, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
    hFacW      (k, tile, j, i_g) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
    hFacS      (k, tile, j_g, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
    maskC      (k, tile, j, i) bool False False False ... False False False
    maskW      (k, tile, j, i_g) bool False False False ... False False False
    maskS      (k, tile, j_g, i) bool False False False ... False False False
    maskCtrlW  (k, tile, j, i_g) bool False False False ... False False False
    maskCtrlS  (k, tile, j_g, i) bool False False False ... False False False
    maskCtrlC  (k, tile, j, i) bool False False False ... False False False

Merge grid_all_tiles with output_merged

[15]:

ecco_dataset_ABCG= xr.merge([ecco_dataset_ABC, grid_dataset])
ecco_dataset_ABCG

[15]:

<xarray.Dataset>
Dimensions:    (i: 90, i_g: 90, j: 90, j_g: 90, k: 50, k_l: 50, k_p1: 51, k_u: 50, nv: 2, tile: 13, time: 12)
Coordinates:
  * tile       (tile) int64 0 1 2 3 4 5 6 7 8 9 10 11 12
  * j          (j) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * i          (i) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
    XC         (tile, j, i) float32 -111.60647 -111.303 ... -111.86579
    YC         (tile, j, i) float32 -88.24259 -88.382515 ... -88.07871 -88.10267
    rA         (tile, j, i) float32 362256450.0 363300960.0 ... 361119100.0
    time_bnds  (time, nv) datetime64[ns] 2010-01-01 2010-02-01 ... 2011-01-01
    iter       (time) int32 158532 159204 159948 160668 ... 165084 165804 166548
  * time       (time) datetime64[ns] 2010-01-16T12:00:00 ... 2010-12-16T12:00:00
  * i_g        (i_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
  * k          (k) int32 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
    Z          (k) float32 -5.0 -15.0 -25.0 -35.0 ... -5039.25 -5461.25 -5906.25
    PHrefC     (k) float32 49.05 147.15 245.25 ... 49435.043 53574.863 57940.312
    drF        (k) float32 10.0 10.0 10.0 10.0 10.0 ... 387.5 410.5 433.5 456.5
    dxC        (tile, j, i_g) float32 15583.418 15588.104 ... 23406.256
    rAw        (tile, j, i_g) float32 361699460.0 362790240.0 ... 364760350.0
    dyG        (tile, j, i_g) float32 23210.262 23273.26 ... 15595.26 15583.685
    hFacW      (tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
  * j_g        (j_g) int32 0 1 2 3 4 5 6 7 8 9 ... 80 81 82 83 84 85 86 87 88 89
    rAs        (tile, j_g, i) float32 179944260.0 180486990.0 ... 364150620.0
    dxG        (tile, j_g, i) float32 15584.907 15589.316 ... 23142.107
    dyC        (tile, j_g, i) float32 11563.718 11593.785 ... 15578.138
    hFacS      (tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
  * k_u        (k_u) int64 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
  * k_l        (k_l) int64 0 1 2 3 4 5 6 7 8 9 ... 40 41 42 43 44 45 46 47 48 49
  * k_p1       (k_p1) int64 0 1 2 3 4 5 6 7 8 9 ... 42 43 44 45 46 47 48 49 50
    XG         (tile, j_g, i_g) float32 -115.0 -115.0 ... -102.928925 -108.95171
    YG         (tile, j_g, i_g) float32 -88.17569 -88.31587 ... -88.02409
    CS         (tile, j, i) float32 0.06157813 0.06675376 ... -0.9983638
    SN         (tile, j, i) float32 -0.99810225 -0.9977695 ... -0.057182025
    Zp1        (k_p1) float32 0.0 -10.0 -20.0 -30.0 ... -5244.5 -5678.0 -6134.5
    Zu         (k_u) float32 -10.0 -20.0 -30.0 -40.0 ... -5244.5 -5678.0 -6134.5
    Zl         (k_l) float32 0.0 -10.0 -20.0 -30.0 ... -4834.0 -5244.5 -5678.0
    Depth      (tile, j, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0 0.0
    rAz        (tile, j_g, i_g) float32 179944260.0 180486990.0 ... 364150620.0
    drC        (k_p1) float32 5.0 10.0 10.0 10.0 ... 399.0 422.0 445.0 228.25
    PHrefF     (k_p1) float32 0.0 98.1 196.2 ... 51448.547 55701.18 60179.445
    hFacC      (k, tile, j, i) float32 0.0 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0 0.0
    maskC      (k, tile, j, i) bool False False False ... False False False
    maskW      (k, tile, j, i_g) bool False False False ... False False False
    maskS      (k, tile, j_g, i) bool False False False ... False False False
    maskCtrlW  (k, tile, j, i_g) bool False False False ... False False False
    maskCtrlS  (k, tile, j_g, i) bool False False False ... False False False
    maskCtrlC  (k, tile, j, i) bool False False False ... False False False
Dimensions without coordinates: nv
Data variables:
    SSH        (time, tile, j, i) float32 0.0 0.0 0.0 0.0 ... nan nan nan nan
    ADVx_TH    (time, tile, k, j, i_g) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0
    ADVy_TH    (time, tile, k, j_g, i) float32 0.0 0.0 0.0 0.0 ... 0.0 0.0 0.0

Examining the merged Dataset

The result of this last merge is a single Dataset with 3 Data variables, and a complete set of model grid parameters (distances and areas).

Merging and memory

Merging Datasets together does not make copies of the data in memory. Instead, merged Datasets are in fact just a reorganized collection of pointers. You may want to delete the original variables to clear your namespace, but it is not necessary.

Summary

Now you know how to merge multiple Datasets using the merge command. We demonstrated merging of Datasets constructed from three different variables types and the model grid parameters.