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Remote Sensing of Soil Moisture: An Overview in Relation to Coastal Soils
Victor Klemas†, Charles W. Finkl‡, and Nijad Kabbara§
School of Marine Science and Policy
University of Delaware
Newark, DE 19716, U.S.A.
†

Department of Geosciences
Charles E. Schmidt College of Science
Florida Atlantic University
Boca Raton, FL 33431, U.S.A.
‡

National Council for Scientific Research
Marine Research Center
Beirut, Lebanon
§

ABSTRACT

INTRODUCTION

Soil moisture plays an important role in the exchange of water and heat
energy between the land and atmosphere and is used in studies of global climate change. Soil moisture data are also required for reservoir management,
early warning of droughts, irrigation scheduling, and crop yield forecasting. Coastal soils in general span the gamut of soil properties necessary for
agriculture and maintaining natural environments, including transitional
wetlands. Beach characteristics, such as soil moisture, grain size and type,
are needed for determining substrate-bearing strength, modeling beach
erosion, and planning beach nourishment. Because microwave radiation
from soil is strongly dependent on moisture content, soil moisture has traditionally been mapped with airborne microwave radiometers. Innovative
antenna technology has enabled microwave radiometers on satellites, such
as Soil Moisture and Ocean Salinity and Aqua, to measure soil moisture on
a global scale. Better corrections for surface roughness, vegetation cover, soil
temperature, and topography must still be devised, and techniques for sensing soil moisture beyond the top few centimeters developed.

Soil moisture has an important role in the calculation of water and energy
budgets needed for climate studies. Soil moisture and sea surface salinity are
required to improve meteorological and climate predictions. The data are
also important for assessing agricultural conditions, irrigation management,
hydrologic problems, and studies of desertification, all of which are relevant
to the study of coastal zones where about 44% of the world’s population
lives within 150 km of the sea (United Nations Atlas of the Oceans, 2013).
Because microwave radiation is sensitive to soil moisture, passive and active microwave remote sensing provides a unique capability for mapping
soil moisture (Calvet et al., 2011). Early remote sensing of soil moisture
was performed from airborne platforms (Chanzy et al., 1997; Jackson et al.,
1999; John, 1992). More recently there are many sensors in space able to
provide information on surface soil moisture. Over the past few decades,
remotely sensed surface soil moisture datasets were obtained from scatterometer observations of the Active Microwave Instrument (AMI) on the
European Remote Sensing (ERS) satellites and the Advanced Scatterometer
(ASCAT) on MetOp; data were also obtained from observations of various
multifrequency radiometers, including the Advanced Microwave Scanning
Radiometer for the Earth Observing System (AMSR-E), the Scanning Multichannel Microwave Radiometer (SMMR), as well as the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). Despite the
importance of soil moisture information, until recently there have been

ADDITIONAL INDEX WORDS: Soil moisture sensing, remote sensing, soil
moisture, microwave radiometry of soil moisture, coastal soil moisture.

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