| According to the observed data of Huangshan cloud droplets in June 2011 and July 2014,the correlation between relative dispersion(ε)and droplet concentration(N)was studied,and the factors which affecting the ε-N relationship were discussed.The result showed that there was a negative correlation between ε and N in the precipitation warming cloud.When N was low,ε was scattered in a larger range,and as ε increased,ε gradually converged.Analyzing the high-frequency center of ε-N distribution found that the negative correlation of ε-N was affected by ε-N negative correlation.When ε was large,the cloud droplet spectrum became wider and σ became larger,which was favorable for the collision-coalescence of cloud droplets.When ε was small,the cloud drop spectrum was narrower,σ became smaller,the scale was smaller,and the feature of the collision growth was relatively weak.By analyzing Tf,the negative correlation of ε-N was mainly caused by the collision process.With the increase of Tf,the negative correlation enhance and a was the main contribution.The parameterization of ε-N for warm precipitation clouds in Huangshan area was given.:ε = 0.2175 ×exp(-0.008224 × N)+ 0.3939 × exp(-0.00001388 × N).Used the TAU-2D model to study the effect of aerosol concentration and vertical speed on ε-N distribution in different height and stage of cloud.With the increasing of Na,N and LWC will increase,while ε and cloud droplet size will decrease.The ε of condensation stage and collision,stage decreased.with the increasing Na.When Na was low,ε of collision stage was greater than that of condensation stage but under the high Na background was opposite.In the low Na background,σ increased with height due to the increasing σ in the condensation and collision stage.In the high Na background,ε of condensation stage did not change with height,while the ε of collision stage decreased with the increasing height.There was a negative correlation between ε and N in the condensation and collision stage,and the degree of correlation weakened with the increase of Na.The ε-N negative correlation in the condensation stage did not change significantly with height.In the collision stage,the negative correlation of ε-N increased with height in the low Na background.With the increase of altitude in the high Na background,the negative correlation of ε-N decreased and became positively correlated at the high level cloud.Both ε and w were negatively correlated in the condensation and collision stage,while N and w were significantly positive correlations and were more significant in the collision phases.ε was affected by the combined effect of Na and w,and there were the aerosol-limited regime and updraft-limited regime of ε.The updraft-limited regime area mainly occured in the area where w was larger than 2m/s,and ε in this area decreased with the increase of w.Correspondingly,the aerosol-limited regime mainly occurs when w was small(w<2m/s),and the ε in this region decreased with the increase of Na.There were differences in the ε-N correlations which is in the updraft-limited regime or the aerosol-limited regime at different stages and heights in the cloud. |
