关键词: 北极海雾, 数值模拟, 电波传播, 衰减

Abstract: The Arctic region has a harsh climate and an important strategic location. The shortest straight distance between countries in North America, northern Europe and northern Asia is the path through the Arctic. Meteorological, navigation, communication, radar and other support are needed during the Arctic cruises. Arctic sea fog, which reduces the visibility at sea, can cause ships to lose their routes resulting in serious accidents such as grounding and collision. Sea fog can also cause radiowave propagation phenomena, such as atmospheric ducting over the horizon and serious attenuation of millimeter waves. Using the global reanalysis data, based on the mesoscale atmospheric numerical model suitable for the Arctic region, this paper successfully simulated the Arctic fog and its evolution and development encountered in the 4th Chinese National Arctic Research Expedition in the Arctic Ocean by improving the Noah land surface process scheme, the long wave radiation scheme (RRTMG scheme) and other settings. Based on Mie scattering theory and Rayleigh scattering theory, the unit distance attenuation values for millimeter wave and far infrared band were evaluated. For the two representative frequencies in the millimeter wave band (100 GHz and 30 GHz at the high and low ends of the frequency band), the attenuation value increased gradually with the water content of sea fog at the 30 GHz, but the change was gentle. At 100 GHz, the attenuation value increased rapidly with the water content of sea fog. For the two representative wavelengths of the infrared band (0.1 cm and 50 µm at the high and low ends of the band), the attenuation value increased gradually with the water content of sea fog at the wavelength of 0.1 cm, but the change was slow. At the wavelength of 50 µm, the attenuation value increased rapidly to hundreds of dB·km–1 with the water content of sea fog. The attenuation values of the two wavelengths differed greatly. For the same water content fog area, the far infrared attenuation value per kilometer was far greater than that of the millimeter wave. The attenuation values of high and low end of the millimeter wave band and at the highest end of the infrared wave band (0.1 cm) were generally less than a few tens of dB·km^–1, while the attenuation value at 50 µm, the lowest end of the infrared wave band, was several hundred dB·km^–1, which was much larger than other bands. The Polar WRF model can simulate and obtain more accurate characteristics of Arctic sea fog. The model can also be used to evaluate the spatial and temporal effects of Arctic sea fog on electromagnetic wave propagation attenuation and radio information system characteristics.

Key words: Arctic sea fog, numerical simulation, radiowave propagation, attenuation