Soil Moisture & Freeze–Thaw

From SMAP freeze/thaw products to NISAR-era retrievals, newest first.

2026
Xu, X., Yueh, S. H., Huang, H., Wang, T., Das, N., Entekhabi, D., & Colliander, A. A Semi-Empirical Modeling for Soil Moisture Retrieval Using High-Resolution SAR Data. IEEE JSTARS.
2026
Huang, H., Xu, X., & Yueh, S. H. Analysis of L-Band Radar Signatures of Surface Topography, Soil Moisture, and Vegetation Water Content. IEEE JSTARS, 19.
2025
Kumawat, D., Ebtehaj, A., Xu, X., Colliander, A., & Kumar, V. An Autoencoder Architecture for L-band Passive Microwave Retrieval of Landscape Freeze-Thaw Cycle. IEEE TGRS.
2025
Huang, X., Papale, L. G., Lavalle, M., Del Frate, F., Fattahi, H., Chan, S. K., Lohman, R. B., Xu, X., & Kim, Y. Optimizing the Radiative Transfer Model Using Deep Neural Networks for NISAR Soil Moisture Retrieval. IEEE JSTARS, 18, 12697–12712.
2025
Kim, S.-B., Xu, X., Kraatz, S., Colliander, A., Cosh, M. H., Kelly, V., & Siqueira, P. Soil Moisture Estimates Using L-Band Airborne SAR Over Forests Replicating NISAR Observations. IEEE JSTARS, 18, 7364–7373.
2025
Hodges, E., Chew, C. C., Small, E. E., Bai, D., Al-Khaldi, M. M., Ouellette, J. D., …, Xu, X., et al. A Merged CYGNSS Soil Moisture Product Using a Minimum Variance Estimator. IEEE TGRS, 63, 1–15.
2025
Colliander, A., Cosh, M. H., Bourgeau-Chavez, L., Kelly, V. R., Kraatz, S., Siqueira, P., …, Xu, X., et al. SMAP Validation Experiment 2019–2022 (SMAPVEX19–22): Field Campaign to Improve Soil Moisture and Vegetation Optical Depth Retrievals in Temperate Forests. IEEE JSTARS, 18, 10749–10771.
2022
Yueh, S. H., Shah, R., Chaubell, M. J., Hayashi, A., Xu, X., & Colliander, A. A Semiempirical Modeling of Soil Moisture, Vegetation, and Surface Roughness Impact on CYGNSS Reflectometry Data. IEEE TGRS, 60.
2019
Kim, Y., Kimball, J. S., Xu, X., Dunbar, R. S., Colliander, A., & Derksen, C. Global Assessment of the SMAP Freeze/Thaw Data Record and Regional Applications for Detecting Spring Onset and Frost Events. Remote Sensing, 11(11), 1317.
2017
Derksen, C., Xu, X., Dunbar, R. S., Colliander, A., Kim, Y., Kimball, J. S., et al. Retrieving landscape freeze/thaw state from Soil Moisture Active Passive (SMAP) radar and radiometer measurements. Remote Sensing of Environment, 194, 48–62.
2016
Xu, X., Derksen, C., Yueh, S. H., Dunbar, R. S., & Colliander, A. Freeze/Thaw Detection and Validation Using Aquarius' L-Band Backscattering Data. IEEE JSTARS, 9(4), 1370–1381.
2014
Kim, S., Moghaddam, M., Tsang, L., Burgin, M., Xu, X., & Njoku, E. G. Models of L-Band Radar Backscattering Coefficients Over Global Terrain for Soil Moisture Retrieval. IEEE TGRS, 52(2), 1381–1396.

Snow & SWE

Ten-plus years of radar remote sensing of snow water equivalent.

2026
Yueh, S. H., Xu, X., Wang, T., & Chaubell, M. J. Interferometric Coherence Modeling of Radar and Reflectometer Observations Related to the Temporal and Spatial Variabilities of Snow Depth and Rough Surface. IEEE TGRS, early access.
2022
Tsang, L., Durand, M., Derksen, C., Barros, A. P., Kang, D. H., Lievens, H., …, & Xu, X. Review article: Global monitoring of snow water equivalent using high-frequency radar remote sensing. The Cryosphere, 16(9), 3531–3573.
2017
Shah, R., Xu, X., Yueh, S., Chae, C. S., Elder, K., Starr, B., & Kim, Y. Remote Sensing of Snow Water Equivalent Using P-Band Coherent Reflection. IEEE GRSL, 14(3), 309–313.
2014
Chang, W., Tan, S., Lemmetyinen, J., Tsang, L., Xu, X., & Yueh, S. H. Dense Media Radiative Transfer Applied to SnowScat and SnowSAR. IEEE JSTARS, 7(9), 3811–3825.

Electromagnetic Scattering Physics

The wave physics underneath the retrievals.

2013
Tsang, L., Ding, K. H., Huang, S., & Xu, X. Electromagnetic Computation in Scattering of Electromagnetic Waves by Random Rough Surface and Dense Media in Microwave Remote Sensing of Land Surfaces. Proceedings of the IEEE, 101(2), 255–279.
2012
Xu, X., Tsang, L., & Yueh, S. Electromagnetic Models of Co/Cross Polarization of Bicontinuous/DMRT in Radar Remote Sensing of Terrestrial Snow at X- and Ku-band for CoReH2O and SCLP Applications. IEEE JSTARS, 5(3), 1024–1032.
2010
Ding, K. H., Xu, X., & Tsang, L. Electromagnetic Scattering by Bicontinuous Random Microstructures With Discrete Permittivities. IEEE TGRS, 48(8), 3139–3151.
2008
Liang, D., Xu, X., Tsang, L., Andreadis, K. M., & Josberger, E. G. The effects of layers in dry snow on its passive microwave emissions using dense media radiative transfer theory based on the quasicrystalline approximation (QCA/DMRT). IEEE TGRS, 46(11), 3663–3671.

Under Review

Submitted in 2026.

2026
SMAP and the Land Carbon Cycle. Remote Sensing of Environment. in review
2026
InSAR Phase Data Assimilation for Bayesian SWE Estimation. The Cryosphere. preprint · in open review
2026
The NASA SMAP Earth Observation Satellite Mission. Proceedings of the IEEE. in review

Data Products

2018
Xu, X., Dunbar, R. S., Derksen, C., Colliander, A., Kim, Y., & Kimball, J. S. SMAP L3 Radiometer Global and Northern Hemisphere Daily 36 km EASE-Grid Freeze/Thaw State, Version 2. NASA NSIDC DAAC.

A complete, continuously updated list is on Google Scholar and ORCID.