Research On Parameterization Scheme Of Effective Radius And Dispersion Of Cloud Droplets In Marine Stratocumulus Cloud

The parameterization of the effective radius(re)of the oceanic stratocumulus and the parameterization of the dispersion(d)and cloud droplet number concentration(Nc)can effectively reduce the uncertainty of the first indirect effect of aerosol.Based on the VOCALS-REx field observations from the coastal areas of northern Chile and southern Peru to the southeastern Pacific Ocean in 2008 and the aircraft observation data from the POST field observations on the coast of California in 2008,this paper explores the vertical characteristics of marine stratocumulus clouds and the main factors affecting the computing power of the re-parameterization scheme.The improved parameterization formula for the re-parameterization scheme established by Lu et al.[10]is given,and the d-Nc parameterization scheme suitable for marine stratocumulus clouds is established.The specific conclusions are as follows:(1)The influencing factors of re in the cloud top entrainment zone of marine stratocumulus are liquid water content adiabatic ratio ARL,liquid water content LWC,d and Nc.The main factors of the change of the entrainment zone re relative to the non-entrainment zone are different due to the different entrainment strength.In the construction of re parameterization scheme,the correlation between d and strong entrainment,moderate entrainment and d-Nc in quasi-adiabatic state is introduced into the parameterization equation of re,which can effectively improve the calculation ability of re.(2)The re-parameterization scheme for marine stratocumulus clouds improved and constructed in this study is:re=103(3LWC/4πρw(-0.773d+0.646)Nc))1/3=103(3LWC/4πρw(-0.773(aNc+b)+0.646]Nc)1/3The prediction ability of the scheme is good,and the closed analysis with the observed value passes the 95%significance test.The scheme has the best prediction effect on re in strong entrainment,followed by medium entrainment,and finally quasi-adiabatic state.(3)The aerosol number concentration Na and vertical velocity w in marine stratocumulus clouds have a significant positive power exponential relationship with Nc and a negative power exponential relationship with d,respectively.The parameterization schemes of d and Nc under the influence of Na and cloud w are:d=0.24Na-0.25w-0.12 and NC=272.19Na0.91w0.07.Based on this,the parameterization scheme of d-Nc under the combined action of marine stratocumulus Na and w is constructed:d=(8.81 × 10-4Na-1.16w-0.19)NCThere is a good consistency between the above d-Nc parameterization scheme and the observed d-Nc fitting relationship.