Water Brightness Temperature Research Articles

Quantitative analysis of influencing factors and interactions of thermal infrared polarization of water

ABSTRACTThermal radiation of water is polarized, and thermal infrared polarization characteristics are investigated to detect thermal infrared polarized remote sensing and theoretically support the interpretation of water remote-sensing processes. Quantitative analysis of the influence of detection angle, azimuth angle, wave band and temperature as well as their interactions in various polarized conditions on the thermal infrared polarized characteristics of water is conducted via orthogonal experiment design and spectrum analysis. Results show that the polarized brightness temperature of water decreases with the increase in detection angle and increases with the increase in temperature. Parabolic distribution occurs between the polarized brightness temperature and azimuth angle and the peak of the parabola is located near the azimuth angle of 180°. The polarized brightness temperature in the four wave bands is different and presents distinct characteristics in various detection conditions. The interaction between the temperature and detection angle has an extremely significant effect on the thermal infrared polarized characteristics of water. The research findings contribute new insights into water monitoring by the use of remote-sensing technology for its theoretical significance and practical value of the study in fully utilizing polarized information and promoting the development of quantitative remote sensing.

Мониторинг флуктуаций яркостной температуры воды в СВЧ-диапазоне

Цель исследования - в мониторинге флуктуаций Т воды в процессе ее испарения при температуре t = 42°С, критической для человека, с помощью СВЧ-радиометрии. Методика: проводился мониторинг изменения яркостной температуры Т воды в СВЧ-диапазоне частот 3,8-4,2 ГГц в процессе ее испарения при температуре в измерительной конусной полипропиленовой кювете t = 42°С. Измерения яркостной температуры проводились при помощи радиотермометра. Результаты. Обнаружено появление скачка яркостной температуры Т при температуре в измерительной конусной полипропиленовой кювете = 42°С. Скачок Т характеризовался фронтом нарастания яркостной температуры в этом диапазоне частот в диапазоне ~4°С с градиентом ~0,05°С/мин - 15°С/мин в зависимости от условий организации процесса испарения и резким спадом в течение 10 с, после чего наблюдалась следующая серия менее интенсивных флуктуаций. При этом температура воды оставалась постоянной. Заключение. Выявлены существенные изменения яркостной температуры воды в СВЧ-диапазоне при ее испарении при температуре воды в конусной измерительной кювете t = 42°С, наблюдается флуктуация в виде скачка Т порядка DТ ~4°C в исследуемой области температуры флуктуаций. При этом термодинамическая температура практически не изменяется. Наблюдаемые эффекты должны учитываться при разработке диагностических систем патологического состояния человека и при создании аналитических устройств. The purpose of the research consisted in detection of fluctuation of brightness temperature (T) of water in the area of the temperature Т = 42°С (that is critical for human) during its evaporation by SHF radiometry. Methods: Monitoring of the changes in brightness temperature of water in superhigh frequency (SHF) range (3.8-4.2 GHz) near the phase transition temperature of water Т = 42°С during its evaporation in the cone dielectric cell. The brightness temperature measurements were carried out using radiometer. Results: Fluctuation with maximum of brightness temperature was detected in 3.8-4.2 GHz frequency range near at the temperature of water Т = 42°С. It was characteristic for these T fluctuations that brightness temperature rise time in this range of frequencies in ~4°С temperature range with 0.05-15°С/min gradient and a sharp decrease during 10 s connected with measuring vapor conditions. Then nonintensive fluctuation series was observed. At that, the environment temperature remained constant. Conclusion: The significant increasing in brightness temperature of water during its evaporation in SHF range near the temperature of Т ~42°С were detected. It was shown that for water, Т pull with the amplitude DТ ~4°C are observed. At the same time, thermodynamic temperature virtually does not change. The observed effects can be used in the development of the systems for diadnostics of pathologies in human and analytical system.

Monitoring High-Water Conditions Using Nighttime Thermal Imagery

High-water conditions have been traditionally monitored from images registered during the daytime in the visible and near-IR bands. However, a number of factors may be at work that hinder reliable discrimination of high waters on daytime imagery. These factors include: specular reflection from the water, and the presence of semi-submerged ice and wet soil, each having reflectances similar to water. It is shown that night-time thermal images can be employed, on which only the natural emission of water and natural features is registered, in the reliable detection of flood waters (nighttime brightness temperature of water is higher).