ASA Ag Hackathon Workshop Series:
Volumetric Water Content

Dr. Leonardo M. Bastos

Note

The content below was partially based on the Crop-CASMA presentation and other related resources.

Introduction

Tracking crop condition and soil moisture content throughout the growing season can be important tools to:

  • Predict crop yields
  • Assess/predict levels of soil water content and its effects on crops
  • Predict droughts/floods

Introduction

  • However, measuring these conditions (crop and soil water) can be labor and cost-intensive especially at larger scales such as an entire country.

  • Due to that need, USDA and NASA worked together to launch 2 satellite missions to address this need.

USDA/NASA Crop Condition and Soil Moisture Analytics Tool (Crop-CASMA)

Crop-CASMA is a web-based geospatial application:

  • Designed to facilitate the utilization of the remotely sensed geospatial vegetation index and soil moisture data

  • Data derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and NASA Soil Moisture Active Passive (SMAP) missions

  • Designed to assess conterminous U.S. crop vegetation and soil moisture conditions

  • Check the interactive map

  • For this workshop, we will focus on SMAP.

NASA Soil Moisture Active Passive (SMAP)

  • NASA SMAP measures soil moisture from the top 5cm of the soil column

  • SMAP Level-4 datasets assimilate SMAP observations into physically-based numerical models of the land surface water, energy, and carbon cycles

  • Check this 3-min video for a quick intro to SMAP.

SMAP products

There are 7 data product levels depending on processing stage:

Note

We will focus on Level 4 data only.

SMAP Level 4 products

Even just within level 4 products, there are lots of variables!
They vary based on:

  • Variable of interest:
    • Volumetric water content
    • Soil moisture anomaly
    • Soil moisture condition (categorical)
  • Spatial resolution:
    • 1 km
    • 9 km

SMAP Level 4 products

Even just within level 4 products, there are lots of variables!
They vary based on:

  • Spatial extent (soil depth):
    • top soil (top 5 cm)
    • sub soil (top 100 cm)
  • Temporal resolution:
    • Every 3 hours
    • Daily
    • Every 3 days
    • Weekly
    • Multi-year average

SMAP Level 4 products

SMAP validation

SMAP-derived data is validated through a network of soil moisture sensing stations across the USA.

  • For more information on how SMAP products are derived and how they are validated, check the full paper here.

Resources

Let’s code!

  • Although we could access this data base using the interactive map, a more reproducible and automated way of doing it is through coding.

  • Let’s shift to the coding part of this workshop by downloading this GitHub repository.