Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations

Optical remote sensing (about 0.4~2.0 μm) indexes of soil moisture (SM) are valuable for some specific applications such as monitoring agricultural drought and downscaling microwave SM, due to their abundant data sources, higher spatial resolution, and easy-to-use features, etc. In this study, we ev...

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Autores principales:	Hao Sun, Hao Liu, Yanhui Ma, Qunbo Xia
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	optical remote sensing soil vegetation water content moisture drought Science Q
Acceso en línea:	https://doaj.org/article/6a56251caad74c73bfee57adca890702
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spelling	oai:doaj.org-article:6a56251caad74c73bfee57adca8907022021-11-25T18:54:59ZOptical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations10.3390/rs132246382072-4292https://doaj.org/article/6a56251caad74c73bfee57adca8907022021-11-01T00:00:00Zhttps://www.mdpi.com/2072-4292/13/22/4638https://doaj.org/toc/2072-4292Optical remote sensing (about 0.4~2.0 μm) indexes of soil moisture (SM) are valuable for some specific applications such as monitoring agricultural drought and downscaling microwave SM, due to their abundant data sources, higher spatial resolution, and easy-to-use features, etc. In this study, we evaluated thirteen typical optical SM indexes with aircraft and in situ observed SM from two field campaigns, the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) and 2016 (SMAPVEX16) conducted in Manitoba, Canada. MODIS surface reflectance products (MOD09A1) and Sentinel-2 multispectral imager Level-1C data were utilized to calculate the optical SM indexes. The evaluation results demonstrated that (1) the Visible and Shortwave Infrared Drought Index (VSDI) and Optical TRApezoid Model (OPTRAM) outperform the other eleven optical SM indexes as compared with aircraft and in situ observed SM. They also presented well consistence in temporal variation with the in situ observed SM. (2) The VSDI achieved comparable performance with the OPTRAM while the former has very simple calculation expression and the latter requires complex process to determine the dry and wet boundaries. (3) Both the VSDI and OPTRAM utilize two sensitive bands of soil and vegetation moisture, i.e., Red and SWIR bands, whereas the other eleven SM indexes only employ one sensitive band. This may be the main reason of the evaluation results. (4) Based on this recognition, improvements of the VSDI and OPTRAM were created and validated in this study through adding more sensitive band to VSDI and combining NDVI and modified VSDI into a new feature space for calculating the optical SM index as with OPTRAM. The results are conducive to selecting and utilizing the current numerous optical SM indexes for SM and drought monitoring.Hao SunHao LiuYanhui MaQunbo XiaMDPI AGarticleoptical remote sensingsoilvegetationwater contentmoisturedroughtScienceQENRemote Sensing, Vol 13, Iss 4638, p 4638 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	optical remote sensing soil vegetation water content moisture drought Science Q
spellingShingle	optical remote sensing soil vegetation water content moisture drought Science Q Hao Sun Hao Liu Yanhui Ma Qunbo Xia Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations
description	Optical remote sensing (about 0.4~2.0 μm) indexes of soil moisture (SM) are valuable for some specific applications such as monitoring agricultural drought and downscaling microwave SM, due to their abundant data sources, higher spatial resolution, and easy-to-use features, etc. In this study, we evaluated thirteen typical optical SM indexes with aircraft and in situ observed SM from two field campaigns, the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) and 2016 (SMAPVEX16) conducted in Manitoba, Canada. MODIS surface reflectance products (MOD09A1) and Sentinel-2 multispectral imager Level-1C data were utilized to calculate the optical SM indexes. The evaluation results demonstrated that (1) the Visible and Shortwave Infrared Drought Index (VSDI) and Optical TRApezoid Model (OPTRAM) outperform the other eleven optical SM indexes as compared with aircraft and in situ observed SM. They also presented well consistence in temporal variation with the in situ observed SM. (2) The VSDI achieved comparable performance with the OPTRAM while the former has very simple calculation expression and the latter requires complex process to determine the dry and wet boundaries. (3) Both the VSDI and OPTRAM utilize two sensitive bands of soil and vegetation moisture, i.e., Red and SWIR bands, whereas the other eleven SM indexes only employ one sensitive band. This may be the main reason of the evaluation results. (4) Based on this recognition, improvements of the VSDI and OPTRAM were created and validated in this study through adding more sensitive band to VSDI and combining NDVI and modified VSDI into a new feature space for calculating the optical SM index as with OPTRAM. The results are conducive to selecting and utilizing the current numerous optical SM indexes for SM and drought monitoring.
format	article
author	Hao Sun Hao Liu Yanhui Ma Qunbo Xia
author_facet	Hao Sun Hao Liu Yanhui Ma Qunbo Xia
author_sort	Hao Sun
title	Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations
title_short	Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations
title_full	Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations
title_fullStr	Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations
title_full_unstemmed	Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations
title_sort	optical remote sensing indexes of soil moisture: evaluation and improvement based on aircraft experiment observations
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/6a56251caad74c73bfee57adca890702
work_keys_str_mv	AT haosun opticalremotesensingindexesofsoilmoistureevaluationandimprovementbasedonaircraftexperimentobservations AT haoliu opticalremotesensingindexesofsoilmoistureevaluationandimprovementbasedonaircraftexperimentobservations AT yanhuima opticalremotesensingindexesofsoilmoistureevaluationandimprovementbasedonaircraftexperimentobservations AT qunboxia opticalremotesensingindexesofsoilmoistureevaluationandimprovementbasedonaircraftexperimentobservations
_version_	1718410528371507200

Optical Remote Sensing Indexes of Soil Moisture: Evaluation and Improvement Based on Aircraft Experiment Observations

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