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305 changes: 305 additions & 0 deletions DataTree/DataTree_Tutorial.ipynb
Original file line number Diff line number Diff line change
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{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"\n",
"# How to use `xarray.DataTree` with hierarchical data\n",
"\n",
"\n",
"## Overview: \n",
"\n",
"This notebook will demonstrate how to use `xarray.DataTree` with [_GPM IMERG Final Precipitation L3 Half Hourly 0.1 degree x 0.1 degree V07 (GPM_3IMERGHH_07)_](https://disc.gsfc.nasa.gov/datasets/GPM_3IMERGHH_07/summary) and use xarray's plotting capabilities to plot precipitation in the Gulf of Mexico during Hurricane Ida. GPM_3IMERGHH_07 is a L3 gridded product with a group hierarchical structure."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"import cartopy.crs as ccrs\n",
"import matplotlib.pyplot as plt\n",
"from xarray import open_datatree\n",
"from metpy.plots import ctables"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Opening the dataset with `open_datatree()`"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7 = open_datatree(\n",
" '~/Downloads/3B-HHR.MS.MRG.3IMERG.20210829-S073000-E075959.0450.V07B.HDF5', engine='h5netcdf'\n",
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This line is going to change once this is merged pydata/xarray-data#31

")\n",
"gpm_imerghh_7"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### List all of the groups with `.groups`"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7.groups"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Accessing variables in a nested groups\n",
"Nested variables and groups can be accessed with either dict-like syntax or method based syntax."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7['/Grid']\n",
"\n",
"# Returns only the data contained in the \"/Grid\" group"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7['/Grid/precipitation']"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7.Grid.precipitation"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Get the parent and child nodes from a group"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7['/Grid/Intermediate'].parent"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7.Grid.children"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### `Xarray.DataTree` objects and `xarray.Dataset` objects have the same key properties like:\n",
"\n",
"- `dims`: a dictionary mapping of dimension names to lengths, for the variables in a node, and a node’s ancestors.\n",
"\n",
"- `data_vars`: a dict-like container of DataArrays corresponding to variables in a node.\n",
"\n",
"- `coords`: another dict-like container of DataArrays, corresponding to coordinate variables in a node, and a node’s ancestors.\n",
"\n",
"- `attrs`: dict with metadata relevant to data in a node.\n",
"\n",
"With `DataTree` you can get these properties at any of the nodes (groups) they are defined in."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7.dims\n",
"# Note there are no dimensions, coordinates, or data variables defined at the root node"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7.attrs"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7['/Grid'].dims"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7['/Grid/Intermediate'].dims"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"gpm_imerghh_7['/Grid/Intermediate'].data_vars"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Plotting precipitation data with DataTree\n",
"Xarray’s plotting capabilities are centered around DataArray objects. To plot DataTree objects we access their relevant DataArrays in this case, `gpm_imerghh_7['/Grid/precipitation']`. \n",
"\n",
"We use the `.where()` method to get a subset of precipitation data over the Gulf of Mexico."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"precipitation_subset = gpm_imerghh_7['/Grid/precipitation'].where(\n",
" (gpm_imerghh_7['/Grid/precipitation'].lat >= 20)\n",
" & (gpm_imerghh_7['/Grid/precipitation'].lat <= 35)\n",
" & (gpm_imerghh_7['/Grid/precipitation'].lon >= -110)\n",
" & (gpm_imerghh_7['/Grid/precipitation'].lon <= -78),\n",
" drop=True,\n",
")"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Data masking\n",
"We add a data mask to the precipitation values that are zero."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"precipitation_subset_mask = precipitation_subset.where(precipitation_subset > 0.0)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Add a custom precipitation color map from [metpy](https://unidata.github.io/MetPy/latest/api/generated/metpy.plots.ctables.html)"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"clevs = [0, 1, 2.5, 5, 7.5, 10, 15, 20, 30, 40, 50, 70, 100, 150, 200, 250, 300, 400, 500, 600, 750]\n",
"norm, cmap = ctables.registry.get_with_boundaries('precipitation', clevs)\n",
"cmap"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Plot the data with `.plot()`\n",
"Note since this data is two-dimensional it calls `xarray.plot.pcolormesh()` by default with just the `.plot()` method."
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {},
"outputs": [],
"source": [
"# Set the figure size, projection, extent and grid lines to the plot\n",
"fig = plt.figure(figsize=(8, 8))\n",
"ax = plt.axes(projection=ccrs.PlateCarree())\n",
"ax.set_extent([-100, -80, 20, 35])\n",
"ax.coastlines()\n",
"gl = ax.gridlines(draw_labels=True, linewidth=1, color='black', linestyle='--')\n",
"gl.right_labels = False\n",
"gl.top_labels = False\n",
"\n",
"# Get the minimum and maximum values in the array\n",
"min = precipitation_subset_mask.min()\n",
"max = precipitation_subset_mask.max()\n",
"\n",
"# Plot the precipitation data\n",
"precipitation_subset_mask[0].plot(\n",
" x=\"lon\",\n",
" y=\"lat\",\n",
" ax=ax,\n",
" cmap=cmap,\n",
" cbar_kwargs={\"orientation\": \"horizontal\", \"pad\": 0.05},\n",
" vmin=min,\n",
" vmax=max,\n",
")\n",
"\n",
"plt.title('Half-hourly precipitation rate in the Gulf of Mexico on August 29, 2021 at 07:30')"
]
}
],
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"language_info": {
"codemirror_mode": {
"name": "ipython",
"version": 3
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"file_extension": ".py",
"mimetype": "text/x-python",
"name": "python",
"nbconvert_exporter": "python",
"pygments_lexer": "ipython3"
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"nbformat_minor": 2
}
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