Cloud drop effective radius

The cloud drop effective radius (alternatively cloud effective radius or effective radius) is a weighted mean of the size distribution of cloud droplets.[1] The term was defined in 1974 by James E. Hansen and Larry Travis as the ratio of the third to the second moment of a droplet size distribution to aid in the inversion of remotely sensed data.[2] Physically, it is an area weighted radius of the cloud drop particles.

Mathematically, this can be expressed as ${\displaystyle r_{e}={\dfrac {\int \limits _{0}^{\infty }\pi \cdot r^{3}\cdot n(r)\,dr}{\int \limits _{0}^{\infty }\pi \cdot r^{2}\cdot n(r)\,dr}}}$.

The global effective particle radius has different values for water and ice clouds: the former is around 14 μm, whereas for ice it is around 25 μm. Studies also indicate that the effective cloud droplet radius is larger over oceans than over ground by 15%-20%. By contrast, the difference in the ice particle size over land and oceans is much smaller (only 5%).[3]

See also

• Liquid water content
• Raindrop size distribution

References

1. "Cloud Effective Radius". Goddard Earth Sciences Data and Information Services Center. Archived from the original on 24 July 2009. Retrieved 3 August 2009.
2. Hansen., J.E. and L.D. Travis (1974). "Light scattering in planetary atmospheres". Space Science Reviews. 16 (4): 527–610. Bibcode:1974SSRv...16..527H. doi:10.1007/BF00168069.
3. Stubenrauch, C. J.; Rossow, W. B.; Kinne, S.; Ackerman, S.; Cesana, G.; Chepfer, H; Di Girolamo, L.; Getzewich, B.; Guignard, A.; Heidinger, A.; Maddux, B. C.; Menzel, W.P; Minnis, P.; Pearl, C.; Platnick, S.; Poulsen, C.; Reidi, J.; Sun-Mack, S; Walther, A.; Winker, D.; Zeng, S.; Zhao, G. (2013). "Assessment of global cloud datasets from satellites: Project and Database initiated by GEWEX Radiation Panel". Bulletin of the American Meteorological Society. 94 (7): 1031–1049. Bibcode:2013BAMS...94.1031S. doi:10.1175/BAMS-D-12-00117.1.