Study On Key Technology Of Identifyinging And Evaluating Potential Aircraft Icing Regions

Aircarft icing has a significant influence on the safety of flight,recognition of potential aircraft icing regions and assessment of severity correctly and duly have a great value on ensuring people's lives and assets.In this paper,potential aircraft icing regions are recognized based on Minnis' s icing classification criteria which has been put into operation in the U.S.A.The feasibility of the classification criteria is tested by living examples.This paper is based on SBDART radiative transfer model.5 cloud parameters including: cloud phase products,cloud top temperature,cloud optical thickness,cloud particle effective radius and liquid water path are set as input to SBDART radiative transfer model.9 situations are considered to identity 5 icing intensity categories which named as none,low,mid,high,and unknown.5 cloud parameters are either from MODIS cloud data products or inversed from FY-2G geostationary meteorological satellite VIS and IR4 channels.Although 5 cloud parameters which are necessary for Minnis' s icing classification criteria are provided by MODIS cloud data products directly,MODIS can not meet the demand of the widely used in operation for a low temporal resolution which means we can not always get the data at the right time and place.Under this condition,however,geostationary meteorological satellite is a good choice.Cloud products of FY-2G do not include 5 cloud parameters needed by Minnis' s icing classification criteria,inversion procedure must be carried out at first.According to the fact that the reflection function of clouds at a non-absorbing band in visible wavelength region is mainly influenced by cloud optical thickness,while the reflection function at a water absorbing band in the near infrared is mainly influenced by cloud effective particle size,cloud optical thickness and cloud effective particle size can be inversed from FY-2G geostationary meteorological satellite VIS and IR4 channels with the help of SBDART radiative transfer model.Liquid water path can be calculated then and cloud microphysical parameters products based on domestic satellite are developed in operational trail.The main algorithms and process for inversion are also introduced in this paper.Apart from cloud optical thickness and cloud effective particle size,other factors(surface albedo,cloud top height,solar zenith angle,satellite zenith angle,relative azimuth angle)which influence inversion results are analyzed.Some sensitivity experiments are also carried out for particular purposes,whose results show that cloud optical thickness and cloud effective particle size are the main course of the differences between reflection function under different circumstances on two channel respectively.Finally,this paper takes the aircraft icing events occurred in Urumqi,Xinjiang and Jinan,Shandong as an example to illustrate the feasibility of the inversion method.By comparing the differences between MODIS cloud data products and 5 cloud parameters inversed from FY-2G geostationary meteorological satellite VIS and IR4 channels of the same time level.Statistics contrast analysis and error analysis shows great consistency between the recognized potential aircraft icing regions computed with two kinds of different data.