Natural water thermal radiation at a gigahertz frequency

Moscow State University of Civil Engineering, 129337, Yaroslavskoye Shosse, 26, Moscow, Russia

^* Corresponding author: GavrilinSN@mgsu.ru

Abstract

The radiation-temperature dependence for natural water in the temperature range of 50-90 degrees Celsius was experimentally investigated. Experimental studies were carried out using radiometer with central frequency 37.5 GHz. The fluctuation threshold of sensitivity of radiometer was equal 0.2 K, with a constant relaxation time of the order of one second. The thermodynamic water temperature was measured by a contact thermometer immersed in the water column. The measurements were carried out outdoors at an ambient temperature of about 24 degrees Celsius. A noticeable increase of radio brightness temperature (about 25 K) was detected in 50-90 degrees Celsius temperature range. The qualitative coincidence of the experimental data with the theoretical ones calculated using the Stogrin model is demonstrated. The obtained coincidence of experimental data with theoretical data makes it possible to use heated and cooled water to create thermal standards and use them for millimeter wavelengths antenna calibrations under field conditions. The radio contrast value of the radiation-temperature dependence in the temperature range under study makes it possible to detect thermal variations of the hydro objects surfaces. A significant contrast of the water thermal radiation in the range of gigahertz frequency can be used for water monitoring and achievement of the environmental sustainability of cities and settlements.