Abstract View
Characterizing the Vertical Transport of Aerosols During Deep Convective Events
CHANAKYA BAGYA RAMESH, Dié Wang, Scott Giangrande, Jian Wang, Yang Wang, Missouri University of Science and Technology
Abstract Number: 130
Working Group: Aerosols, Clouds and Climate
Abstract
Atmospheric aerosols affect the global energy budget by scattering and absorbing sunlight (direct effects) and by changing the microphysical structure, lifetime, and coverage of clouds (indirect effects). Globally, new particle formation in free troposphere is a major source of nucleation- and Aitken-mode aerosols. Recent studies showed that deep convective systems can transport these aerosols from free troposphere to boundary layer by strong convective downdrafts. These vertically transported aerosols can grow into cloud condensation nuclei (CCN) and significantly influence the subsequent cloud formation. Compared to entrainment and mixing, deep convective downdraft processes may be more rapid and efficient in the vertical transport of aerosols. However, most climate models do not include the downdraft induced aerosol vertical transport as a source of CCN, mainly because the frequency of deep convective events varies significantly with geographic location, and thus their contributions to CCN are unpredictable.
In this study, we analyze vertical transport of aerosols during Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign. This vertical transport mechanism is characterized by an abrupt emergence of nucleation- or Aitken-mode aerosols with sizes below 50 nm, a decrease of equivalent potential temperature, and a change of carbon monoxide concentration measured at the ground site. Using this criterion, we identified eight deep convective transport events with various intensities during the HI-SCALE intense operation periods (51 days). Measurements onboard the G-1 aircraft before the transport events support the finding that aerosols and carbon monoxide were transported from the free troposphere. The size of the transported Aitken-mode aerosols was found to be negatively correlated with the decrease of the equivalent potential temperature, probably resulting from the different altitudes of the source of the downdraft. The relationship between the downdraft intensity and properties of the vertically transported aerosols (size and number concentration) will be further discussed.