Potential applications of SMAP brightness temperature to improve permafrost monitoring in Arctic tundra area
Abstract
Surface organic layer thickness and soil moisture represent first order controls on permafrost active layer freeze/thaw (FT) dynamics in the northern high latitudes. However, it remains a significant challenge for models to represent such effects in the northern permafrost area. Satellite microwave remote sensing can capture significant dielectric changes resulting from landscape FT transitions or drying/wetting events, with enhanced sensitivity to soil surface and profile moisture and FT conditions at longer wavelengths such as L-band. Here, we explore the possibilities using SMAP brightness temperature (Tb) to improve regional permafrost monitoring through data analysis and modelling in the Arctic tundra area. Our analysis demonstrated that strong insulation of a very dry organic layer at surface modulates the response of underlying permafrost to surface thermal variations. This is not well represented in current models mostly due to uncertainties in soil moisture inputs or simulations including the SMAP Level 4 system. Model sensitivity analysis shows that different soil organic profiles can have a large impact on the soil moisture distribution along the active layer; SMAP Tb can provide information on surface soil moisture variations, which may help constrain the model representation of organic soil profile. The SMAP Tb also shows sensitivity to active layer refreezing process up to 20 cm below surface, which can be used to improve model representation of FT process. Preliminary simulations using a multi-layer microwave emission model in Alaska North Slope shows that the model can capture the seasonality of L-band Tb reasonably well (R≥0.4, RMSE≤5K), with largest errors during the transitional season. During spring thaw and summer period, Tb changes are mostly associated with surface wetting and drying events. During the fall and early winter period, Tb follows the changes in active layer liquid water content, with strong sensitivity to deeper (>10 cm) soils after surface soil freezes. Our results highlight the importance of accurately representing active layer soil moisture in regional permafrost monitoring. Future work include using SMAP Tb to evaluate the FT process representation in global land models in Arctic tundra area and model improvement in organic soil representation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H53E..06Y
- Keywords:
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- 1843 Land/atmosphere interactions;
- HYDROLOGY;
- 1855 Remote sensing;
- HYDROLOGY;
- 1866 Soil moisture;
- HYDROLOGY;
- 4262 Ocean observing systems;
- OCEANOGRAPHY: GENERAL