CALIPSO Finds Smoke at High Altitudes Down Under

Determining where smoke layers are found and their location is important to better understand how tiny ash particles can possibly effect climate. "If smoke particles reach the upper troposphere or lower stratosphere, they can persist for weeks and travel long distances," explains Chip Trepte, the project scientist for CALIPSO. And at these altitudes they can also influence the formation and lifetime of clouds as well as their brightness. All of these effects can alter the way sunlight is reflected and absorbed in the atmosphere.

Because so many different aspects of the atmosphere are affected by the smoke particles, it is important to understand what caused their abnormal presence in the stratosphere. Fromm explains that as the heat from the fire rises, a convective weather system is created. Within this, a severe thunderstorm, known as the pyrocumulonimbus (pyroCb), develops. As the fire increases in strength, it acts like a chimney as it sucks the smoke from the flames up into the convective column. The smoke is then injected into the atmosphere at abnormally high altitudes – a side effect similar to volcanic eruptions. The abundant smoke fuels the storm's updrafts by serving as the nuclei for cloud particles, seeding so many that little-to-no precipitation forms, and taking away a storm-killing drag force.

While the elements of the fires in Australia are becoming clearer, there is still quite a bit of uncertainty surrounding the pyro-convection process. Satellite missions like CALIPSO have been supporting field campaigns to get a better handle on the meteorological, chemical, physical anomalies that forest fires create. This support in turn helps scientists learn more about other pyroCbs that have occurred.

"PyroCbs, such as the ones in Victoria, are historically rare," explains Fromm, who has been studying pyroconvection for over a decade. "Preliminary data from CALIPSO show that the smoke from these storms has gotten to altitudes never observed before."