Measurements of the dielectric properties of seawater and NaCl solutions at 2.65 GHz

Abstract. We have measured the permittivity of representative samples of natural seawater, synthetic seawater, and aqueous NaC1 solutions over the frequency range 3-20 GHz, in 0.1-GHz steps and over the temperature range -2ø-30øC in 1 ø steps. Additional measurements have been made at spot frequencies (23.8, 36.5, and 89 GHz) and at selected temperatures between -2 ø and 30øC. The data from these measurements have allowed us to deduce an interpolation function for e(v, t, S) in the ranges 2 <-v <-20 GHz, -2 ø <-t <-30øC, and 20%0 <-S <-40%0 with a precision of 1%. If the frequency range is extended up to 40 GHz, the precision of the interpolation function is about 3%. The data have also allowed us to compare the permittivities of natural seawater, synthetic seawater, and aqueous NaC1 solution with the same salinities. Natural and synthetic seawater have the same permittivities within a 1% experimental error estimate. An aqueous NaC1 solution has a significantly different permittivity (up to about 6% difference, depending upon the frequency and temperature). IntroductionFor microwave remote sensing applications over the ocean using radars and radiometers, a precise knowledge of the emissivity and reflectivity properties of the sea surface is required. The dielectric permittivity of seawater e(v, t, S) for a frequency v, temperature t, and salinity S is a vital parameter in all models describing the interaction of a wind-roughened sea surface with microwave radiation.The main objectives of the research program were to (1) deduce an interpolation function for e(v, t, S) with a precision good enough to satisfy the technical improvements in radiometric sensitivities for use in radiative transfer models in the frequency range 1-100 GHz and (2) The goal of such models is to provide the permittivity and conductivity of seawater at any frequency as a function of the "salinity" and temperature. Such a model has to be based upon experimental data. We have found only three authors who report permittivity

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“…This observation corroborates the work of Weyl [1964] and Ho and Hall [1973], who found a similar difference.…”

Section: Seawater Permittivity At 89 Ghz As a Function Of Temperaturesupporting

confidence: 82%

New permittivity measurements of seawater

Ellison¹,

Balana²,

Delbos³

et al. 1998

Radio Science

203

140

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“…The figure shows the real part (left) and imaginary part (right) of the relative dielectric constant as a function of temperature for a salinity of 38.274 psu. For comparison, the red curves are the results from the model of Klein and Swift [3] which is based primarily on the earlier measurements of Ho [2,4]. Current results show about 1% difference in the real part and about 2% difference in the imaginary part of the dielectric constant compared to the Klein and Swift results.…”

Section: Resultsmentioning

confidence: 93%

“…The method is similar to that employed by Ho and Hall [2] with the exception that the cavity is operated in the transmission mode (two coupling loops) rather than the reflection mode adopted by Ho and Hall. This was done to require less power and avoid the potential for heating of the sample that was reported with the earlier data.…”

Section: Measurement Approachmentioning

confidence: 99%

Remote sensing of salinity: The dielectric constant of sea water

Vine

Lang

Utku

et al. 2011

2011 XXXth URSI General Assembly and Scientific Symposium

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Global monitoring of sea surface salinity from space requires an accurate model for the dielectric constant of sea water as a function of salinity and temperature to characterize the emissivity of the surface. Measurements are being made at 1.413 GHz, the center frequency of the Aquarius radiometers, using a resonant cavity and the perturbation method. The cavity is operated in a transmission mode and immersed in a liquid bath to control temperature. Multiple measurements are made at each temperature and salinity. Error budgets indicate a relative accuracy for both real and imaginary parts of the dielectric constant of about 1%.

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“…The loss tangent for 1-butanol. (217) and (218) and complete uncertainty analysis is given in Baker-Jarvis et al [116].…”

Section: ) 73mer2mentioning

confidence: 99%