National Weather Service (NWS) Climate Prediction Center (CPC)
This suite of products from the National Weather Service's Climate Prediction Center provides soil moisture conditions in the U.S. at the daily and monthly scales, including total soil moisture, percentiles and anomalies, monthly and seasonal change, and outlooks.
Soil moisture is estimated by a one-layer Leaky Bucket hydrological model. The model takes as forcing observed precipitation and temperature and calculates soil moisture, evaporation, runoff, and snowpack (global daily version). The potential evaporation is estimated from observed temperature. Model parameters are constant spatially and tuned to reproduce runoff of several small river basins in eastern Oklahoma. This resulted in a maximum holding capacity of 760mm (or 29.9 inches) of water. Along with a common porosity of 0.47 this implies a soil column of 1.6 meter (=5.25 ft).
The hydrological model runs in two different configurations:
- Daily and monthly updates over the contiguous U.S. (CONUS): The daily soil moisture dataset in the current month is calculated with real-time daily precipitation and temperature from CPC in-house products with one-day lag. The observed monthly precipitation and temperature datasets over 344 Climate Divisions are from NOAA's National Centers for Environmental Information (1895–present) and are usually available on the 5th of the current month.
- Daily and monthly updates over the global (0.5x0.5 degree resolution) domain: The daily (1979–present) and monthly (1948–present) global soil moisture datasets are calculated with the observed CPC Unified Global Precipitation Analysis and CPC global surface air temperature analysis with one-day lag. The monthly update is usually available around the 5th of the current month.
Anomalies are defined as deviations from the 1991–2020 daily or monthly climatology. Percentiles are based on the period from 1895 (344 U.S. Climate Divisions) or 1979/1948 (global domain) to the most recent soil moisture records.