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.
| Language | English |
|---|---|
| Pages | 363-372 |
| Number of pages | 10 |
| Journal | Remote Sensing of Environment |
| Volume | 221 |
| Early online date | 28 Nov 2018 |
| DOIs | |
| Publication status | Published - Feb 2019 |
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Keywords
- Downscaled brightness temperature
- Field experiment
- SMAP
- Validation
Cite this
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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 Journal › Article › Academic › peer-review
TY - JOUR
T1 - Evaluation of SMAP downscaled brightness temperature using SMAPEx-4/5 airborne observations
AU - Ye, N.
AU - Walker, J. P.
AU - Bindlish, R.
AU - Chaubell, J.
AU - Das, N. N.
AU - Gevaert, A. I.
AU - Jackson, T. J.
AU - Rüdiger, C.
PY - 2019/2
Y1 - 2019/2
N2 - 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.
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.
KW - Downscaled brightness temperature
KW - Field experiment
KW - SMAP
KW - Validation
UR - http://www.scopus.com/inward/record.url?scp=85057254019&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85057254019&partnerID=8YFLogxK
U2 - 10.1016/j.rse.2018.11.033
DO - 10.1016/j.rse.2018.11.033
M3 - Article
VL - 221
SP - 363
EP - 372
JO - Remote Sensing of Environment
T2 - Remote Sensing of Environment
JF - Remote Sensing of Environment
SN - 0034-4257
ER -