Study On The Method Of Detecting Atmospheric Duct

Atmospheric duct is a anomalous structure obviously different from the standardatmosphere, which can cause electromagnetic (EM) wave rays lying in theatmospheric duct refracted towards the surface of the earth and make EM powertrapped or guided in a thin troposphere layer above the earth, using the duct, radarsystem can enhance the detect range or ultra horizon. Especially in the sea surface,evaporation duct is one kind of the atmospheric duct frequently appearing in themarine environment. In this paper, based on the introduction of basic atmosphericrefraction structure and the duct styles, the detecting method of atmospheric duct ismainly studied, and the main results obtained are the following:1. Detecting the atmospheric radio refractivity is the base for the atmosphericduct. Usually, the radio refractivity can be straight or remote detected, therefore, theatmospheric duct can be straight or remote detected. But the detection precision of theremote method not meets the demand.2.Detecting the evaporation duct, using the tethered aerostat system, microwaverefract meter，and the iron tower platform. The radio refractivity obtained from thetethered aerostat system and iron tower platform using the observation of atmospherictemperature, humidity and press. Compare the microwave refract meter with the irontower platform, the result shows that the iron tower platform usually has higher theevaporation duct height.3. Low altitude atmospheric duct can be computed using the sounding data, thesounding balloon is the mainly equipment for detecting the low altitude atmosphericduct. Using about20years Dalian sounding data, the frequency distributions ofatmospheric duct is computed, the statistics results reveal that the occurrenceprobability and parameter of atmospheric duct is highest in summer.4. A new method for region atmospheric duct diagnosis is found, using the GTS(Global Telecommunications System) global sounding data. The method is useful for study the region atmospheric duct.5. Remote sensing the atmospheric duct can use the GPS, sea clutter, and laserlidar. The remote sensing method has evidence advantage; therefore, the detectionprecision must be enhanced.