Characterizing Precipitation and Soil Moisture in the Arctic Using SMAP Satellite Data

Strategic Insights -

Recent research from the Finnish Meteorological Institute in Helsinki, Finland, has shed light on the complex relationships between precipitation and soil moisture in the Arctic region. Utilizing NASA's Soil Moisture Active Passive (SMAP) satellite, scientists have analyzed the patterns and interrelations between these critical components of the global water, energy, and biogeochemical cycles. The study's findings have significant implications for our understanding of the Arctic's hydrological and climatological processes.

Key Takeaways:

  • The research reveals a notable spatial and temporal variability in soil moisture, with a weaker correlation between precipitation and soil moisture in spring due to snowmelt and a stronger relationship in summer and fall.
  • Water bodies are found to complicate soil moisture retrieval, causing retrievals to saturate.
  • The SM2RAIN algorithm shows promising results in detecting rainfall areas, but estimating rainfall intensity is more challenging, particularly for light and very heavy rain.
  • The exponential decay time scale (t) of soil moisture drydowns exhibits limited spatial or temporal variability, with a positively skewed distribution and a mode of 1.6 days.
  • The lower bound of soil moisture (SM [min]) shows spatial variability and is higher near water bodies, with a prominent peak at 0.02 m³ m⁻³.
  • Grid cells with dense vegetation and low vegetation agree better with each other, indicating the impact of water bodies on soil moisture retrieval.

Statistics:

  • The study analyzed SMAP satellite data for Finland from April to September over 2018-2019.
  • The research estimated that 1.6 days is the mode of the exponential decay time scale (t) of soil moisture drydowns.
  • The median of the exponential decay time scale (t) is 4.0 days.
  • The lower bound of soil moisture (SM [min]) exhibits a median of 0.17 m³ m⁻³ and a mode of 0.14 m³ m⁻³.
  • Water bodies complicate soil moisture retrieval, causing retrievals to saturate.

Sources:

  • Finnish Meteorological Institute. (2025). Characterizing precipitation and soil moisture drydowns in Finland using SMAP satellite data. Hydrology and Earth System Sciences, 29(), 4791-4810. (http://www.hydrology-and-earth-system-sciences.net/)
  • COPERNICUS Publications. (n.d.). Hydrology and Earth System Sciences. (https://doi-org.sdpl.idm.oclc.org/10.5194/hess-29-4791-2025)