a Ae aan ENBUB: WEXLER ¢ pao Yes, this is referable to the mass of dust. It depends on the sises. But about this stratospheric exchange, I agree with everything that Ben says about the lower portion of the stratosphere which you might say is isotrepically connected with the trepesphere. When you get up sbove into the stratosphere, then the direct exchange between it and the lower atmosphere becomes much more difficult to do because there are no isotropic surfaces that really penetrate up. up there, They are sostiy horisontal So, to get things way high up they are likely to stay there except by a very slow process of diffusion or fallout. Vary slow, but none of this very rapid quasi horizontal larze scale of exchange that 3en was taliing about. \ GBs How high? WEXLER: I would say that if you get up to 100,000 feet. GRICUSs My recollection is that in the case of Krakatoa is that they observed brilliant sunsets in the Sahara desert and other places and they persisted for a matter of months and possibly a year. These things were such as to indicate the presence of dust as scattering at a very high altitude well above the tropopause. WEXLER: That ie right. the stuff went. GRIGGSs That is how they estimated the height to which At least 160,000 feet. There was persistence of this dust in the high stratoschere a tong time. —, BOE ARCHIVES