SMOS Optical Thickness Changes in Response to the Growth and Development of Crops, Crop Management, and Weather

dc.contributor.author Hornbuckle, Brian
dc.contributor.author Patton, Jason
dc.contributor.author VanLoocke, Andy
dc.contributor.author VanLoocke, Andy
dc.contributor.author Suyker, Andrew
dc.contributor.author Roby, Matthew
dc.contributor.author Walker, Victoria
dc.contributor.author Iyer, Eswar
dc.contributor.author Herzmann, Daryl
dc.contributor.author Endacott, Erik
dc.contributor.department Agronomy
dc.date 2021-09-22T15:14:01.000
dc.date.accessioned 2021-11-05T16:10:36Z
dc.date.available 2021-11-05T16:10:36Z
dc.date.copyright Fri Jan 01 00:00:00 UTC 2016
dc.date.issued 2016-07-01
dc.description.abstract <p>The Soil Moisture and Ocean Salinity (SMOS) remote sensing satellite was launched by the European Space Agency in 2009. The L-band brightness temperature observed by SMOS has been used to produce estimates of both soil moisture and <em>tau</em>, the optical thickness of the land surface. Although <em>tau</em> should theoretically be proportional to the amount of vegetation present within a SMOS pixel, several initial investigations have not been able to confirm this expected behavior. However, when the noise in the SMOS <em>tau</em> product is removed, <em>tau</em> in the U.S. Corn Belt, a region of extensive row-crop agriculture, has a distinct shape that mirrors the growth and development of crops. We find that the peak value of SMOS <em>tau</em> occurs at approximately 1000 degrees C day (base 10 degrees C) growing degree days after the mean planting date of maize (corn). We can explain this finding in the following way: <em>tau</em> is directly proportional to the water column density of vegetation; maize contributes the most to growing season changes in <em>tau</em> in the Corn Belt; and maize reaches its maximum water column density at its third reproductive stage of development, at about 1000 degrees C day growing degree days. Consequently, SMOS <em>tau</em> could be used to monitor the phenology of crops in the Corn Belt at a spatial resolution similar to a U.S. county and a temporal frequency on the order of days. We also examined the magnitude of the change in SMOS <em>tau</em> over the growing season and hypothesized it would be related to the amount of accumulated solar radiation, but found this not to be the case. On the other hand, the change in magnitude was smallest for the year in which the most precipitation fell. These findings are rational since SMOS <em>tau</em> at the satellite scale is in fact a function of both vegetation and soil surface roughness, and soil surface roughness is reduced by precipitation. To fully explain changes in SMOS <em>tau</em> in the Corn Belt it appears that it will be necessary to use in situ and remotely-sensed observations along with agro-ecosystem models to account for land management decisions made by farmers that affect changes in soil surface roughness and all of the relevant biophysical processes that affect the growth and development of crops.</p>
dc.description.comments <p>This is a manuscript of an article from <em>Remote Sensing of Environment</em> 180 (2016): 320, <a href="http://dx.doi/org/10.1016/j.rse.2016.02.043" target="_blank">doi: 10.1016/j.rse.2016.02.043</a>. Posted with permission.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/agron_pubs/115/
dc.identifier.articleid 1115
dc.identifier.contextkey 9560756
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath agron_pubs/115
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/Yr3K2mpr
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/agron_pubs/115/2016_VanLoocke_SMOSOptical.pdf|||Fri Jan 14 18:51:38 UTC 2022
dc.source.uri 10.1016/j.rse.2016.02.043
dc.subject.keywords Passive microwave remote sensing (microwave radiometry)
dc.subject.keywords Soil Moisture and Ocean Salinity (SMOS)
dc.subject.keywords L-band
dc.subject.keywords Optical thickness
dc.subject.keywords Vegetation
dc.subject.keywords Agriculture
dc.subject.keywords Annual crops
dc.subject.keywords Corn (maize)
dc.subject.keywords Soybean
dc.title SMOS Optical Thickness Changes in Response to the Growth and Development of Crops, Crop Management, and Weather
dc.type article
dc.type.genre article
dspace.entity.type Publication
relation.isAuthorOfPublication b88ab303-e9ba-4ac1-ba87-5ae642e91270
relation.isOrgUnitOfPublication fdd5c06c-bdbe-469c-a38e-51e664fece7a
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