The contributions of gauge-based precipitation and smap brightness temperature observations to the skill of the smap level-4 soil moisture product

Rolf H. Reichle, Qing Liu, Joseph V. Ardizzone, Wade T. Crow, Gabrielle J.M. De Lannoy, Jianzhi Dong, John S. Kimball, Randal D. Koster

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Soil Moisture Active Passive (SMAP) mission L-band brightness temperature (Tb) observations are rou-tinely assimilated into the Catchment land surface model to generate Level-4 soil moisture (L4_SM) estimates of global surface and root-zone soil moisture at 9-km, 3-hourly resolution with;2.5-day latency. The Catchment model in the L4_SM algorithm is driven with 1/48, hourly surface meteorological forcing data from the Goddard Earth Observing System (GEOS). Outside of Africa and the high latitudes, GEOS precipitation is corrected using Climate Prediction Center Unified (CPCU) gauge-based, 1/28, daily precipitation. L4_SM soil moisture was previously shown to improve over land model-only estimates that use CPCU precipitation but no Tb assimilation (CPCU_SIM). Here, we additionally examine the skill of model-only (CTRL) and Tb assimilation-only (SMAP_DA) estimates derived without CPCU precipitation. Soil moisture is assessed versus in situ measurements in well-instrumented regions and globally through the instrumental variable (IV) method using independent soil moisture retrievals from the Advanced Scatterometer. At the in situ locations, SMAP_DA and CPCU_SIM have comparable soil moisture skill improvements relative to CTRL for the unbiased root-mean-square error (surface and root-zone) and correlation metrics (root-zone only). In the global average, SMAP Tb assimilation in-creases the surface soil moisture anomaly correlation by 0.10–0.11 compared to an increase of 0.02–0.03 from the CPCU-based precipitation corrections. The contrast is particularly strong in central Australia, where CPCU is known to have errors and observation-minus-forecast Tb residuals are larger when CPCU precipitation is used. Validation versus streamflow measurements in the contiguous United States reveals that CPCU precipitation provides most of the skill gained in L4_SM runoff estimates over CTRL.

Original languageEnglish
Pages (from-to)405-424
Number of pages20
JournalJournal of Hydrometeorology
Volume22
Issue number2
DOIs
StatePublished - 2021

Keywords

  • Data assimilation
  • Hydrology
  • Land surface model
  • Precipitation
  • Remote sensing
  • Soil moisture

Fingerprint

Dive into the research topics of 'The contributions of gauge-based precipitation and smap brightness temperature observations to the skill of the smap level-4 soil moisture product'. Together they form a unique fingerprint.

Cite this