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Cloud is a common weather phenomenon in the sky. It is formed by condensation of water vapor in the atmosphere. It is a suspension composed of water droplets, ice crystals or their mixtures. The infrared radiation characteristics of clouds are related to the particles phase state in clouds, the particle radius distribution and the cloud optical thickness. They are also affected by the sun, earth surface types and atmospheric conditions. In this paper, it introduces the physical parameters of the ice crystals in cloud, and researches the scattering characteristics of ice crystals. Based on radiation transfer algorithms, an ice cloud radiation model is established. The ice cloud infrared radiation is analyzed that the ice clouds infrared radiation varies with optical thickness. It shows that when the cloud optical thickness is not large, the radiance of ice clouds decreases with the increase of optical thickness.

For general power system, the thermal exhaust at the exit of funnel has obvious infrared radiation characteristics. In this paper, funnel exhaust plume about the dynamic system is modeled and analyzed. The 3D flow field of exhaust plumes is calculated based on CFD methods. A calculation method of high temperature exhaust plume's infrared radiation is obtained by spectral band model and calibration with C-G two parameters. And the effect of the detecting azimuth angle on the flow field and the infrared radiation of ship exhaust plumes is analyzed. It can be concluded that with the detection angles’ increasing, the space distribution of the exhaust plume shows a tendency to increase progressively. The difference of the radiation intensity of different detection angles can be up to 32.6%.

Aiming at the application requirements of infrared detection, the influence of earth background interference on plume radiation detection is investigated and discussed in this article. The infrared image of the earth&rsquo, s atmospheric background radiation is simulated by the spectral correlation based on the conversion model of the surface radiation with different bands. The infrared radiation image of the jet flame and the background is generated by overlapping the infrared radiation of the engine flame and the background radiation according to the detection angle of view. Through the image quality evaluation model, the detectability of the flame is analyzed. The simulating results show that the comprehensive statistical features such as image information entropy, variance and signal-to-clutter ratio can be used to evaluate the detectability of the engine flame.