A Time-Varying Interarrival Time Interval Threshold for Broken Particle Identification During Airborne Measurements

Abstract

The invention discloses a broken particle identification method with a time-varying arrival time interval threshold in the airborne measurement process, belongs to the technical field of signal processing, and is mainly used in image acquisition and preprocessing of airborne cloud precipitation particle measurement. This method is based on the statistics of the particle arrival time interval value that meets the requirements of the statistical particle number within a certain period of time, and through the fitting of the numerical distribution of the statistical arrival time interval, the distribution of the arrival time interval value of broken particles and natural particles is determined. The modal position of the broken particle can be determined to determine the inter-arrival time threshold of the broken particle; the broken particle artifact caused by the mechanical collision of the particle with the probe arm during the measurement process, or the interaction with the turbulence and wind shear generated by the probe housing can be analyzed. Identification and elimination help the instrument to measure more realistic cloud precipitation particle data. The invention can be used as the preprocessing of airborne cloud precipitation particle image collection, and has important significance for further using the airborne measured cloud precipitation particle image data to study cloud microphysics process.

Description

technical field [0001] The invention belongs to the technical field of signal processing, and in particular relates to a method for identifying image artifacts of broken cloud and precipitation particles during airborne measurement. Background technique [0002] Airborne cloud microphysics measurement is one of the main observation methods for modern cloud microphysics research. Aircraft cloud microphysics observations using airborne cloud precipitation particle imagers can be used not only for cloud precipitation physics research, but also for satellite radar and other remote sensing results. verification. From the particle images obtained by the airborne cloud precipitation particle imaging instrument, the particle image data contains many broken pseudo-particles. This includes both fragments formed by the mechanical collision and fragmentation of particles with the probe arm during the measurement process, as well as fragmented particle artifacts caused by the turbulent ...

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Problems solved by technology

[0003] The identification and elimination of broken pseudo-particles in the process of airborne measurement of cloud precipitation particle images has been carried out abroad. In 1978, Cooper of the US Bureau of Land Reclamation proposed to use the spatial distance to filter out the scattered and broken particles. Although The spatial distribution of broken particles is relatively close, but since the sampling rate of the particle image is proportional to the speed of the aircraft, the spatial distance between the particle images is also relatively close when the speed of the aircraft is relatively fast, while the actual flight speed of the aircraft It is difficult to keep constant, so the method based on spatial distance has great limitations in filtering out broken particles

In 2005, Korolev of the Canadian Ministry of Environment proposed a method of using the number of isolated particles to distinguish particle breakage artifacts. This method assumes that there can only be one isolated particle in a particle image frame, and when a particle breaks, many broken particles are recorded at the same time. In a particle image frame, but in many cases, many broken particle fragments are recorded by the instrument in a single form, so the method based on the number of isolated particles is not high in the accuracy of broken particle identification

In 2006, Field et al. of the US National Center for Atmospheric Research proposed a method to filter out broken particles using the arrival time interval threshold. The time interval between two natural particles entering the sampling area of ​​the instrument is shorter than the time interval between two adjacent fragments entering the sampling area of ​​the instrument, and the broken pseudo-particles can be identified with high accuracy, but this method is not time-varying. As a result, only a single time interval threshold is used to identify broken pseudo-particles. Considering the complex and changeable environment in the cloud, the distribution of cloud particles in various parts of the cloud is fluctuating and uneven, so a single fixed arrival time interval threshold method is difficult to fully and accurately identify broken pseudo-particles

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