Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 6 2005 10.5194/acpd-5-11911-2005 http://www.atmos-chem-phys-discuss.net/5/11911/2005/ http://www.atmos-chem-phys-discuss.net/5/11911/2005/acpd-5-11911-2005.html http://www.atmos-chem-phys-discuss.net/5/11911/2005/acpd-5-11911-2005.pdf 11911 11928 2005-11-22 The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius I. M. Lensky lenskyi@mail.biu.ac.il D. Rosenfeld Department of Geography and Environmental Studies, Bar-Ilan University, Ramat-Gan, Israel Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel A 3-min 3-km rapid scan of the METEOSAT Second Generation geostationary satellite over southern Africa was applied to tracking the evolution of cloud top temperature (<i>T</i>) and particle effective radius (<i>r_e</i>) of convective elements. The evolution of <i>T</i>-<i>r_e</i> relations showed little dependence on time, leaving re to depend almost exclusively on <i>T</i>. Furthermore, cloud elements that fully grew to large cumulonimbus stature had the same <i>T</i>-<i>r_e</i> relations as other clouds in the same area with limited development that decayed without ever becoming a cumulonimbus. Therefore, a snap shot of <i>T</i>-<i>r_e</i> relations over a cloud field provides the same relations as composed from tracking the time evolution of <i>T</i> and <i>r_e</i> of individual clouds, and then compositing them. This is the essence of exchangeability of time and space scales, i.e., ergodicity, of the <i>T</i>-<i>r_e</i> relations for convective clouds. This property has allowed inference of the microphysical evolution of convective clouds with a snap shot from a polar orbiter. The fundamental causes for the ergodicity are suggested to be the observed stability of <i>r_e</i> for a given height above cloud base in a convective cloud, and the constant renewal of growing cloud tops with cloud bubbles that replace the cloud tops with fresh cloud matter from below.