Characteristics of cloud drop spectra in tropical warm clouds |
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| Authors: | Paul S K Pillai A G Selvam A M Murty A S R |
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| Institution: | (1) Indian Institute of Tropical Meteorology, 411 005 Pune, India |
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| Abstract: | Characteristics of cloud drop spectra were studied using 400 samples obtained from 120 warm cumulus clouds formed during the summer monsoon season.The total concentration of cloud drops (N
T) varied from 384 to 884 cm–3 and the maximum concentration was observed in the layer below the cloud-top. The width of the drop spectrum was broader in the cloud-base region and in the region below the cloud-top. The spectrum was multimodal at all levels except in the cloud-top region where it was unimodal. The concentration of drops with diameter greater than 50  m (N
L) varied from 0.0 to 0.674 cm–3.N
L was larger in the cloud-base region.N
L decreased with height up to the middle level and thereafter showed an increase. In the cloud-top region no large drops were present. The computed values of the liquid water varied between 0.132 and 0.536 g m–3 and the mean volume diameter (MVD) varied between 8.1 and 12.0 m. The LWC and MVD showed a decrease with height except in the middle region of the cloud where the values were higher than the adjacent levels. The dispersion of the cloud drops was lower (0.65) in the cloud-top region and higher (1.01) in the cloud-base region.The observed cloud microphysical characteristics were attributed to vertical mixing in clouds induced by the cloud-top gravity oscillations (buoyancy oscillations) generated by the intensification of turbulent eddies due to the buoyant production of energy by the microscale-fractional-condensation (MFC) in turbulent eddies. |
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| Keywords: | Cloud drop spectra Turbulent eddies Microscale-fractional condensation (MFC) Cloud-top-gravity oscillations Vertical mixing |
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