UCLA

Prior studies have shown that high levels of aerosols in the environment of convective clouds can cause the convection to become more vigorous through a five step process. Tropical cyclones (TCs) start as clusters of convective clouds; intense convection is important for the development of the cluster into a TC. This study tests the hypothesis that high aerosol content in the vicinity of a convective cloud cluster increases the chances that the cluster will develop into a TC by invigorating its convection. This study centers on 63 clusters that developed into TCs (developers) and 98 clusters that dissipated before becoming a TC (nondevelopers). Using observations from a satellite associated with the “A-train” group of satellites, it was established that the average aerosol content surrounding developers was significantly higher than that surrounding nondevelopers. Furthermore, A-train measurements were used to establish that each of the five steps associated with invigoration of convection by aerosols were more prominent in the developers than in the nondevelopers. Altogether, the data suggests convective cloud clusters embedded in regions with elevated aerosols may have a greater likelihood of developing into a TC because the aerosols may invigorate their convection.

A-train satellite data are also used to investigate ozone levels in the eyes of mature TCs. Several previous studies have found evidence of high ozone levels inside TC eyes. Explanations for the elevated ozone involve intrusion of ozone-rich stratospheric air downward into the eye or a lower tropopause over the eye. Other studies have found no evidence of elevated ozone in TC eyes. However, ozone measurements from both types of studies (evidence and no evidence of elevated ozone) were less than optimal. This study analyses seven mature TCs with satellite overpasses directly over the eye – an optimal situation for ozone measurement. The results indicate TCs can have very high ozone concentrations in the eyewall. This suggests eyewall lighting produces the ozone. The data also suggest the elevated ozone content in the eyewall is often transported into the eye. Thus TC eyes can contain elevated ozone levels, but the source appears to be the eyewall, not the stratosphere.