Real-time Non-contact Millimeter Wave Characterization of Water-Freezing and Ice-Melting Dynamics
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Real-time Non-contact Millimeter Wave Characterization of Water-Freezing and Ice-Melting Dynamics Sudhandra Sundaram & S. K. Sundaram & Paul P. Woskov
Received: 11 October 2008 / Accepted: 11 December 2008 / Published online: 3 January 2009 # Springer Science + Business Media, LLC 2008
Abstract We applied millimeter wave radiometry for the first time to monitor waterfreezing and ice-melting dynamics in real-time non-contact. The measurements were completed at a frequency of 137 GHz. Small amounts (about 2 mL) of freshwater or saltwater were frozen over a Peltier cooler and the freezing and melting sequence was recorded. Saltwater was prepared in the laboratory that contained 3.5% of table salt to simulate the ocean water. The dynamics of freezing-melting was observed by measuring the millimeter wave temperature as well as the changes in the ice or water surface reflectivity and position. This was repeated using large amounts of freshwater and saltwater (800 mL) mimicking glaciers. Millimeter wave surface level fluctuations indicated as the top surface melted, the light ice below floated up indicating lower surface temperature until the ice completely melted. Our results are useful for remote sensing and tracking temperature for potentially large-scale environmental applications, e.g., global warming. Keywords Millimeter wave reflectivity . Freezing . Melting . Fresh/sea water . Remote sensing . Global warming
1 Introduction The dielectric properties (real (ε′) and imaginary (ε′′) permittivity) of ice and water have been extensively studied for cloud measurements and geophysical features advancing environmental and atmospheric sciences [1–6]. Recently, an empirical model [7] based on the parameterizations in Liebe et al. [8] and Hufford [9] (called the LH model) was S. Sundaram (*) Phillips Academy, Andover, MA 01810, USA e-mail: [email protected] S. K. Sundaram Pacific Northwest National Laboratory, Richland, WA 99352, USA P. P. Woskov Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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J Infrared Milli Terahz Waves (2009) 30:393–400
developed using empirical fits to published experimental data at frequencies < 1000 GHz for both ice and water, and limited to temperatures ≥ 0◦C for water. Laboratory measurements of the dielectric properties have been made and published by a number of researchers at millimeter and sub-millimeter wavelengths (~ 100–3000 GHz). Accurate measurement of the complex dielectric permittivity, ε = ε′ + iε′′, of ice and water at these frequencies are critical for using radar in these areas of application. The scattering of millimeter waves due to melting ice spheres and melting have been treated by many researchers [10, 11]. Maya et al. [12] have shown that the monitoring of the water of the leaf of the plant can monitor the aspect of the photosynthesis activity in real-time. They have also monitored the freezing process of the water in the refrigerator and the phase transition of water and ice. Recently, melting snow particles has bee
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