Modelling the dynamic behavior of Cloud Condensation Nuclei: case study comparing clean (LBA/CLAIRE 2001) and polluted (LBA/SMOCC 2002) conditions in Amazonia
Theotonio
Pauliquevis, Institute of Physics at University of Sao Paulo, Brazil, theo@if.usp.br
(Presenting)
Luciana
Varanda
Rizzo, Institute of Physics at University of Sao Paulo, Brazil, lrizzo@if.usp.br
Paulo
Artaxo, Institute of Physics at University of Sao Paulo, Brazil, artaxo@if.usp.br
Meinrat
O
Andreae, Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany., andreae@mpch-mainz.mpg.de
Göran
Frank, Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany., gfrank@mpch-mainz.mpg.de
Olga
L.
Mayol-Bracero, Institute for Tropical Ecosystem Studies, University of Puerto Rico, Puerto Rico, omayol@sunites.upr.clu.edu
Susimar
Gonzalez, Institute for Tropical Ecosystem Studies, University of Puerto Rico, Puerto Rico, sgonzale@sunites.upr.clu.edu
The dynamic behavior of an aerosol population into an air parcel under a cooling process, regarding the cloud drops activation properties of these aerosols were investigated. We compared chemical composition and size distribution of clean (CLAIRE 2001) and polluted conditions under biomass burning influence (SMOCC 2002). To perform the simulation we used the MAPS model (Model for Aerosol Process Studies), from NCAR. MAPS is a box model that includes aerosol size distribution and chemical composition, (including organics - fixed 35% soluble).
The results show that under a clean (polluted) situation, where aerosol number concentration was setted to 1000(7000) #/cm3 predominating the coarse (fine) mode of aerosols, under a cooling process, maximum supersaturation reached 0.33% (0.19%) and minimum activation diameter was 0.22 um (0.46 um). The liquid water content were the same in both conditions. The results agree with ground experimental data: modeled CCN/CN ratio was 0.28 and experimental was 0.39 ± 0.11 under intermediate smoky conditions.
It shows the higher efficiency in the interaction aerosol – water vapor for the polluted situation, given the lower maximum supersaturation reached. This is also the reason why minimum activation diameter was higher in polluted than in clean situation. Regarding that aerosol number concentration is higher under polluted conditions, smallest droplets formed are less efficient to coalescence and to produce rain in warm clouds. The results corroborate with studies concerning changes in cloud patterns associated to land use change in Amazonia, shifting the rain regime from warm to cold clouds under high aerosol loading situation.