资源环境科技发展态势分析平台

The aerosol indirect effects (AIE) on cloud microphysical properties have been studied using ground-based in-situ measurements. Aerosol and cloud microphysical properties were collected from a high altitude site in the Western Ghats region of India, where clouds pass over the surface during South West monsoon. The AIE was estimated using cloud droplet number concentration (AIE_n) and cloud droplet effective radius (AIE_s) at different fixed liquid water content (LWC) bins. The AIE varied in the range 0.01–0.13 for LWC between 0.04 g m⁻³ and 0.26 g m⁻³. The maximum AIE_n and AIE_s (0.125 and 0.119) were observed at the lower LWC bin (0.06–0.07 g m⁻³). An overestimation in AIE_n is due to the dispersion effect. The offset was reduced and AIE_n became close to AIE_s after dispersion correction. Hence for the correct estimation of AIE using cloud droplet number concentration (N_c), dispersion correction should be considered. At the same time, the AIE estimate obtained using R_eff does not need correction as the dispersion effect is implicitly included. Relative dispersion can be viewed not only as the combined effects of σ and r, but also as the combined effects of cloud droplets of different sizes. Further, for the first time in India, the relative contribution by the smaller and medium size droplets to the total dispersion of cloud droplet size distribution (CDSD) at lower and higher LWC bins were studied. In lower LWC, the smaller size droplets are contributing maximum (71%) to the total N_c, whereas the medium size droplets are contributing maximum (61%) to the total dispersion. At higher LWC, the contribution to total N_c by the smaller size droplets was reduced by 20%, however contribution by the medium size droplets increased by 17%, compared to the lower LWC case. Hence at higher LWC, both smaller (42%) and medium (55%) size droplets have a significant role in the total dispersion of CDSD.