Evaluation of SMAP downscaled brightness temperature using SMAPEx-4/5 airborne observations

N. Ye, J. P. Walker, R. Bindlish, J. Chaubell, N. N. Das, A. I. Gevaert, T. J. Jackson, C. Rüdiger

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The Soil Moisture Active and Passive (SMAP) mission, launched by the National Aeronautics and Space Administration (NASA) on 31st January 2015, was designed to provide global soil moisture every 2 to 3 days at 9 km resolution by downscaling SMAP passive microwave observations obtained at 36 km resolution using active microwave observations at 3 km resolution, and then retrieving soil moisture from the resulting 9 km brightness temperature product. This study evaluated the SMAP Active/Passive (AP) downscaling algorithm together with other resolution enhancement techniques. Airborne passive microwave observations acquired at 1 km resolution over the Murrumbidgee River catchment in south-eastern Australia during the fourth and fifth Soil Moisture Active Passive Experiments (SMAPEx-4/5) were used as reference data. The SMAPEx-4/5 data were collected in May and September 2015, respectively, and aggregated to 9 km for direct comparison with a number of available resolution-enhanced brightness temperature estimates. The results show that the SMAP AP downscaled brightness temperature had a correlation coefficient (R) of 0.84 and Root-Mean-Squared Error (RMSE) of ~10 K, while SMAP Enhanced, Nearest Neighbour, Weighted Average, and the Smoothing Filter-based Modulation (SFIM) brightness temperature estimates had somewhat better performance (RMSEs of ~7 K and an R exceeding 0.9). Although the SFIM had the lowest unbiased RMSE of ~6 K, the effect of cloud cover on Ka-band observations limits data availability.

LanguageEnglish
Pages363-372
Number of pages10
JournalRemote Sensing of Environment
Volume221
Early online date28 Nov 2018
DOIs
Publication statusPublished - Feb 2019

Fingerprint

Soil moisture
brightness temperature
Luminance
soil moisture
soil water
temperature
Temperature
Microwaves
downscaling
smoothing
Modulation
filter
evaluation
cloud cover
Catchments
NASA
Rivers
Availability
catchment
rivers

Keywords

  • Downscaled brightness temperature
  • Field experiment
  • SMAP
  • Validation

Cite this

Ye, N., Walker, J. P., Bindlish, R., Chaubell, J., Das, N. N., Gevaert, A. I., ... Rüdiger, C. (2019). Evaluation of SMAP downscaled brightness temperature using SMAPEx-4/5 airborne observations. Remote Sensing of Environment, 221, 363-372. https://doi.org/10.1016/j.rse.2018.11.033
Ye, N. ; Walker, J. P. ; Bindlish, R. ; Chaubell, J. ; Das, N. N. ; Gevaert, A. I. ; Jackson, T. J. ; Rüdiger, C. / Evaluation of SMAP downscaled brightness temperature using SMAPEx-4/5 airborne observations. In: Remote Sensing of Environment. 2019 ; Vol. 221. pp. 363-372.
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abstract = "The Soil Moisture Active and Passive (SMAP) mission, launched by the National Aeronautics and Space Administration (NASA) on 31st January 2015, was designed to provide global soil moisture every 2 to 3 days at 9 km resolution by downscaling SMAP passive microwave observations obtained at 36 km resolution using active microwave observations at 3 km resolution, and then retrieving soil moisture from the resulting 9 km brightness temperature product. This study evaluated the SMAP Active/Passive (AP) downscaling algorithm together with other resolution enhancement techniques. Airborne passive microwave observations acquired at 1 km resolution over the Murrumbidgee River catchment in south-eastern Australia during the fourth and fifth Soil Moisture Active Passive Experiments (SMAPEx-4/5) were used as reference data. The SMAPEx-4/5 data were collected in May and September 2015, respectively, and aggregated to 9 km for direct comparison with a number of available resolution-enhanced brightness temperature estimates. The results show that the SMAP AP downscaled brightness temperature had a correlation coefficient (R) of 0.84 and Root-Mean-Squared Error (RMSE) of ~10 K, while SMAP Enhanced, Nearest Neighbour, Weighted Average, and the Smoothing Filter-based Modulation (SFIM) brightness temperature estimates had somewhat better performance (RMSEs of ~7 K and an R exceeding 0.9). Although the SFIM had the lowest unbiased RMSE of ~6 K, the effect of cloud cover on Ka-band observations limits data availability.",
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Ye, N, Walker, JP, Bindlish, R, Chaubell, J, Das, NN, Gevaert, AI, Jackson, TJ & Rüdiger, C 2019, 'Evaluation of SMAP downscaled brightness temperature using SMAPEx-4/5 airborne observations', Remote Sensing of Environment, vol. 221, pp. 363-372. https://doi.org/10.1016/j.rse.2018.11.033

Evaluation of SMAP downscaled brightness temperature using SMAPEx-4/5 airborne observations. / Ye, N.; Walker, J. P.; Bindlish, R.; Chaubell, J.; Das, N. N.; Gevaert, A. I.; Jackson, T. J.; Rüdiger, C.

In: Remote Sensing of Environment, Vol. 221, 02.2019, p. 363-372.

Research output: Contribution to JournalArticleAcademicpeer-review

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AU - Walker, J. P.

AU - Bindlish, R.

AU - Chaubell, J.

AU - Das, N. N.

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AB - The Soil Moisture Active and Passive (SMAP) mission, launched by the National Aeronautics and Space Administration (NASA) on 31st January 2015, was designed to provide global soil moisture every 2 to 3 days at 9 km resolution by downscaling SMAP passive microwave observations obtained at 36 km resolution using active microwave observations at 3 km resolution, and then retrieving soil moisture from the resulting 9 km brightness temperature product. This study evaluated the SMAP Active/Passive (AP) downscaling algorithm together with other resolution enhancement techniques. Airborne passive microwave observations acquired at 1 km resolution over the Murrumbidgee River catchment in south-eastern Australia during the fourth and fifth Soil Moisture Active Passive Experiments (SMAPEx-4/5) were used as reference data. The SMAPEx-4/5 data were collected in May and September 2015, respectively, and aggregated to 9 km for direct comparison with a number of available resolution-enhanced brightness temperature estimates. The results show that the SMAP AP downscaled brightness temperature had a correlation coefficient (R) of 0.84 and Root-Mean-Squared Error (RMSE) of ~10 K, while SMAP Enhanced, Nearest Neighbour, Weighted Average, and the Smoothing Filter-based Modulation (SFIM) brightness temperature estimates had somewhat better performance (RMSEs of ~7 K and an R exceeding 0.9). Although the SFIM had the lowest unbiased RMSE of ~6 K, the effect of cloud cover on Ka-band observations limits data availability.

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