2. Methods. 2.1 Temperature in the stratosphere relevant for BBOA from pyroCb events. The viscosity of organic aerosols depend strongly on temperature. Simulated zonal mean monthly temperatures for January and July were obtained from the Whole Atmosphere Community Climate Model (WACCM) for the year 2000 (see Fig. ). WACCM has 72 vertical levels from surface to about 140 km above surface level and a horizontal resolution of 1.9° latitude by 2.5° longitude. For the altitude range of 15 -32 km , the stratospheric temperatures vary from 177 -250 K (see Fig. ). As a result, we will focus on this temperature range throughout the remainder of this article.