| Cloud is an important part of the earth-atmosphere system.Cloud microphysical parameters are the basis for studying the cloud physical processes and the effects of cloud radiation.Therefore,the use of cloud radar and other equipment for the ground-based remote sensing and retrieval of cloud parameters is necessary.Because of its short wavelength,35GHz millimeter-wave radar will produce non-negligible attenuation in the detection process.The paper uses the cloud radar data to make a preliminary correction.Using the IQ data of the 35-GHz Ka-band millimeter-wave cloud radar,the power spectrum data was processed,then the retrieval of the microphysical parameters of the stratus was performed,and the combined retrieval method with the cloud radar and microwave radiometer was compared.At the same time,the cirrus cloud microphysical parameters were retrieved.The main content of the paper and the conclusions drawn are as follows:(1)The cloud radar was corrected for complex refractive index,atmospheric attenuation and cloud attenuation.The results show that for a 35GHz cloud radar,the water’s complex refractive index is basically between 0.8 and 0.9,and the ice is between 0.173 and 0.178,which is much smaller than water.The maximum atmospheric attenuation coefficient can reach 0.1dB/km,and the total atmospheric double-pass attenuation can reach 0.3～0.6dB at 10km.The attenuation coefficient is calculated by using the spectrum distribution of the particles in the cloud and the corresponding attenuation section.The attenuation coefficient of the water cloud is generally about 1 dB/km,and the cumulative attenuation of the double-pass can reach 2 dB.The attenuation coefficient of the ice cloud and the cumulative attenuation of the double-pass are all in the order of 10-5,which is much smaller than that of the water cloud.(2)The power spectrum method can separate the vertical velocity of cloud airflow and the free fall velocity of cloud particles.Using the power spectrum to retrieve the parameters of the stratus cloud can eliminate the influence of air disturbance on the spectrum width,which is helpful to improve the cumulative accuracy.In the two layered cloud processes,the concentration of cloud particles(N0)is basically between 10 and 200/cm3,and the typical value is 80-100/cm3;the effective radius(Re)is between 15μm and 25μm;the liquid water content(LWC)is basically between the range of 0.01g/m3～1g/m3,a very small number reaches a maximum of 2g/m3.(3)The retrieval results of the power spectrum method and the "cloud radar-microwave radiometer" combined retrieval method are generally consistent,although they are somewhat different,reflecting the feasibility of the two schemes.Both have their advantages.The combined retrieval method add the data from microwave radiometers and can be used for retrieval of source data.Theoretically,the results are also more reliable.However,microwave radiometer data is greatly affected by attenuation and calibration.Ensure the accuracy of microwave radiometer data.(4)The method of retrieving the air turbulence spectrum width and the vertical velocity of air movement in the stratus cloud can not be applied to the cirrus cloud well.The number of cirrus clouds(N0)obtained by retrieval is smaller than that of the stratus and is basically between 0.5 and 50/cm3.The effective radius(Re)is between 20～40μm.The ice water content(IWC)is much smaller than the stratus cloud and is basically between 10-4 and 10-2g/m3. |
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