Abstract
Knowledge of soil moisture conditions is important for modeling soil temperatures, as soil moisture influences the thermal dynamics in multiple ways. However, in permafrost regions, soil moisture is highly heterogeneous and difficult to model. Satellite soil moisture data may fill this gap, but the degree to which they can improve permafrost modeling is unknown. To explore their added value for modeling soil temperatures, we assimilate fine-scale satellite surface soil moisture into the CryoGrid-3 permafrost model, which accounts for the soil moisture's influence on the soil thermal properties and the surface energy balance. At our study site in the Canadian Arctic, the assimilation improves the estimates of deeper (>10 cm) soil temperatures during summer but not consistently those of the near-surface temperatures. The improvements in the deeper temperatures are strongly contingent on soil type: They are largest for porous organic soils (30%), smaller for thin organic soil covers (20%), and they essentially vanish for mineral soils (only synthetic data available). That the improvements are greatest over organic soils reflects the strong coupling between soil moisture and deeper temperatures. The coupling arises largely from the diminishing soil thermal conductivity with increasing desiccation thanks to which the deeper soil is kept cool. It is this association of dry organic soils being cool at depth that lets the assimilation revise the simulated soil temperatures toward the actually measured ones. In the future, the increasing availability of satellite soil moisture data holds promise for the operational monitoring of soil temperatures, hydrology, and biogeochemistry.
| Original language | English |
|---|---|
| Pages (from-to) | 1814-1832 |
| Number of pages | 19 |
| Journal | Water Resources Research |
| Volume | 55 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Mar 2019 |
| Externally published | Yes |
Bibliographical note
Funding Information:The authors are grateful to Beth Wrona, William Woodley, Justin Adams, Branden Walker, Tracy Rowlandson, and Rachel Humphrey for their efforts in collecting field data. They acknowledge funding by the Canadian Space Agency, ArcticNet, and NSERC (Discovery Grants Program; Changing Cold Regions Network). Simon Zwieback was supported by the Swiss National Science Foundation (P2EZP2_168789) and Moritz Langer by the Federal Ministry of Education and Research (BMBF; grant 01LN1709A). The in situ soil moisture and temperature data, as well as the colocated calibrated Radarsat-2 retrievals, are freely available from the URLs provided in the references (registration required) and so are the reanalysis data.
Publisher Copyright:
©2019. American Geophysical Union. All Rights Reserved.
Funding
The authors are grateful to Beth Wrona, William Woodley, Justin Adams, Branden Walker, Tracy Rowlandson, and Rachel Humphrey for their efforts in collecting field data. They acknowledge funding by the Canadian Space Agency, ArcticNet, and NSERC (Discovery Grants Program; Changing Cold Regions Network). Simon Zwieback was supported by the Swiss National Science Foundation (P2EZP2_168789) and Moritz Langer by the Federal Ministry of Education and Research (BMBF; grant 01LN1709A). The in situ soil moisture and temperature data, as well as the colocated calibrated Radarsat-2 retrievals, are freely available from the URLs provided in the references (registration required) and so are the reanalysis data.
| Funders | Funder number |
|---|---|
| Canadian Space Agency | |
| Natural Sciences and Engineering Research Council of Canada | |
| ArcticNet | |
| URLs | |
| Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung | P2EZP2_168789, 168789 |
| Bundesministerium für Bildung und Forschung | 01LN1709A |
Keywords
- data assimilation
- permafrost
- remote sensing
- soil moisture
- soil temperature