A Study On The Retrievals Of Cloud Microphysical Parameters And In-Cloud Turbulent Dissipation Rate By Using Millimeter-wave Cloud Radar Measurement

Clouds have an important influence on the weather and precipitation.The detection of cloud microphysical parameters(particle effective radius,drop number concentration,etc.)and macro-physical parameters(cloud height,cloud thickness)is essential to study cloud physical process and cloud radiation effects.This paper aims to the detection and retrieval of cloud parameters and in-cloud turbulence characteristics with a ground-based millimeter cloud radar.With the Doppler spectrum data,ambient vertical air velocity and cloud microphysical parameters are solved,and the relationships of vertical air motions to cloud microphysical parameters,to radar reflectivity factor,to Doppler velocity,to Doppler spectrum width,are completely studied and analyzed for understanding the cloud evolution.Turbulent dissipation rate ε and its distribution in clouds is obtained,and the fractional error in derived dissipation rate is evaluated.The conclusions are as follows:(1)Cloud particle effective radius increases as the updraft increase,and cloud drop number concentration decreases accordingly due to the collision-coalescence process.The distribution of liquid water content is in good agreement with the distribution of radar reflectivity factor.With the air updraft gets stronger,the cloud particles deposition speed gets weaker,and the Doppler spectrum width gets stronger.(2)The turbulent dissipation rate ε is strong near cloud base or cloud top,and ranges from 10-10 to 10-0 m2/s3.If the cloud is thinner,the turbulent dissipation rate in the cloud may be more uniform.In general,the turbulent dissipation rate in cirrus is smaller because the turbulence activity in the cloud is relatively weak.The turbulence intensity in the weak precipitation cloud increases rapidly before the precipitation,which is also very strong in the process of precipitation,and in the later period,the turbulence in the cloud will gradually weaken.(3)The Doppler spectrum validates that the turbulent inertial subrange has a-5/3 slope,according with a typical Kolmogorov theory.The two primary assumptions are demonstrated by examples used to retrieve turbulent dissipation rate.Under high turbulence conditions,the turbulent dissipation rate can be retrieved accurately and the fractional error in turbulent dissipation rate is small.However,with the decrease of the turbulent dissipation rate,the fractional error in the turbulent dissipation rate increases gradually.