How to use harmony-py to subset and reformat SMAP data to GeoTIFF

Problem

How can I use NASA Harmony services via the harmony-py Python library to subset SMAP data by variable and bounding box and reformat the result to GeoTIFF?

Solution

from harmony import BBox, Client, Collection, Request
import datetime as dt

Initialize your Harmony client

harmony_client = Client()

Define which data set you’d like to access using the collection concept-id (see how-to for retrieving collection concept-ids). For this example, we’ll use SMAP L3 Radiometer Global Daily 36 km EASE-Grid Soil Moisture, Version 9 (SPL3SMP), C2938664585-NSIDC_CPRD.

collection = Collection(id='C2938664585-NSIDC_CPRD') 

Define your spatial bounds (min_lon, min_lat, max_lon, max_lat). The example below is over the Eastern United States.

bbox = BBox(-93.4,30.3,-77.0,44.5)

Define your temporal range (passed as a dictionary with “start” and “stop” keys, and dates supplied as datetime objects). The example below spans two days in December 2023.

temporal = {'start': dt.datetime(2023,12,12),'stop': dt.datetime(2023,12,13)}

Define the output file format. GeoTIFF is the only choice for reformatting SPL3SMP.

format='image/tiff'

Define the variable(s) within the original data you’d like to output to GeoTIFF.

variables = ['Soil_Moisture_Retrieval_Data_AM/soil_moisture']

Build the request

request = Request(
    collection = collection,
    spatial = bbox,
    temporal = temporal,
    format = format,
    variables = variables
)

Submit the request. This returns a Harmony job ID that can be used to check on progress.

job_id = harmony_client.submit(request)
job_id

‘abc20650-4239-434a-9fff-b54c160f38bf’

Check on Harmony job progress

harmony_client.wait_for_processing(job_id, show_progress=True)

[ Processing: 100% ] |###################################################| [|]

To view the url(s) for your staged files

url = list(harmony_client.result_urls(job_id))
url

[‘https://harmony.earthdata.nasa.gov/service-results/harmony-prod-staging/public/abc20650-4239-434a-9fff-b54c160f38bf/153252383/SMAP_L3_SM_P_20231213_R19240_001_Soil_Moisture_Retrieval_Data_AM_soil_moisture_subsetted_Soil_Moisture_Retrieval_Data_AM_soil_moisture_reformatted.tif’, ‘https://harmony.earthdata.nasa.gov/service-results/harmony-prod-staging/public/abc20650-4239-434a-9fff-b54c160f38bf/153252397/SMAP_L3_SM_P_20231212_R19240_001_Soil_Moisture_Retrieval_Data_AM_soil_moisture_subsetted_Soil_Moisture_Retrieval_Data_AM_soil_moisture_reformatted.tif’]

Download the results to your local directory.

futures = harmony_client.download_all(job_id, directory=".")
filelist = [f.result() for f in futures]  # get filepaths

./153252383_SMAP_L3_SM_P_20231213_R19240_001_Soil_Moisture_Retrieval_Data_AM_soil_moisture_subsetted_Soil_Moisture_Retrieval_Data_AM_soil_moisture_reformatted.tif ./153252397_SMAP_L3_SM_P_20231212_R19240_001_Soil_Moisture_Retrieval_Data_AM_soil_moisture_subsetted_Soil_Moisture_Retrieval_Data_AM_soil_moisture_reformatted.tif

Discussion

NASA Harmony is comprised of cloud-based services that allow you to customize many NASA data sets, providing the ability to subset, reproject and reformat files. Not all transformation services are available for all datasets. Table of Harmony services available for select SMAP data sets.

A longer form tutorial demonstrating NASA Harmony and the harmony-py Python library can be found here.