Next Article in Journal
On the Performances of Trend and Change-Point Detection Methods for Remote Sensing Data
Previous Article in Journal
Nonlocal CNN SAR Image Despeckling
Previous Article in Special Issue
First Evidence of Mesoscale Ocean Eddies Signature in GNSS Reflectometry Measurements
Open AccessArticle

The Polarimetric Sensitivity of SMAP-Reflectometry Signals to Crop Growth in the U.S. Corn Belt

1
Planetary Radar Radio Science Systems Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
2
Microwave Instrument Science Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(6), 1007; https://doi.org/10.3390/rs12061007 (registering DOI)
Received: 20 February 2020 / Revised: 18 March 2020 / Accepted: 19 March 2020 / Published: 21 March 2020
(This article belongs to the Special Issue Applications of GNSS Reflectometry for Earth Observation)
Crop growth is an important parameter to monitor in order to obtain accurate remotely sensed estimates of soil moisture, as well as assessments of crop health, productivity, and quality commonly used in the agricultural industry. The Soil Moisture Active Passive (SMAP) mission has been collecting Global Positioning System (GPS) signals as they reflect off the Earth’s surface since August 2015. The L-band dual-polarization reflection measurements enable studies of the evolution of geophysical parameters during seasonal transitions. In this paper, we examine the sensitivity of SMAP-reflectometry signals to agricultural crop growth related characteristics: crop type, vegetation water content (VWC), crop height, and vegetation opacity (VOP). The study presented here focuses on the United States “Corn Belt,” where an extensive area is planted every year with mostly corn, soybean, and wheat. We explore the potential to generate regularly an alternate source of crop growth information independent of the data currently used in the soil moisture (SM) products developed with the SMAP mission. Our analysis explores the variability of the polarimetric ratio (PR), computed from the peak signals at V- and H-polarization, during the United States Corn Belt crop growing season in 2017. The approach facilitates the understanding of the evolution of the observed surfaces from bare soil to peak growth and the maturation of the crops until harvesting. We investigate the impact of SM on PR for low roughness scenes with low variability and considering each crop type independently. We analyze the sensitivity of PR to the selected crop height, VWC, VOP, and Normalized Differential Vegetation Index (NDVI) reference datasets. Finally, we discuss a possible path towards a retrieval algorithm based on Global Navigation Satellite System-Reflectometry (GNSS-R) measurements that could be used in combination with passive SMAP soil moisture algorithms to correct simultaneously for the VWC and SM effects on the electromagnetic signals. View Full-Text
Keywords: GNSS-R; SMAP-R; VWC; vegetation opacity; crop type; crop height; soil moisture; crop health; crop productivity; agriculture GNSS-R; SMAP-R; VWC; vegetation opacity; crop type; crop height; soil moisture; crop health; crop productivity; agriculture
Show Figures

Graphical abstract

MDPI and ACS Style

Rodriguez-Alvarez, N.; Misra, S.; Morris, M. The Polarimetric Sensitivity of SMAP-Reflectometry Signals to Crop Growth in the U.S. Corn Belt. Remote Sens. 2020, 12, 1007.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop