HR: 11:35h
AN: A32B-06    [Abstracts]
TI: A theoretical study of the impact of anthropogenic CCN on deep convective clouds in the EPIC region
AU: * Pozo, D
EM: dianarpl@yahoo.com
AF: Centro de Ciencias de la Atmosfera, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
AU: Raga, G B
EM: raga@servidor.unam.mx
AF: Centro de Ciencias de la Atmosfera, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
AU: Baumgardner, D
EM: darrel@servidor.unam.mx
AF: Centro de Ciencias de la Atmosfera, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
AB: Several studies have explored the effect of anthropogenic emissions on the evolution and precipitation development of different types of clouds. However, there is still no consensus on the effect, particularly for the case of deep, mixed-phase clouds. In this study we have introduced changes in the parameterization of the autoconversion and accretion processes in the Advanced Regional Prediction System (ARPS). The cloud condensation nuclei (CCN) used in the model were obtained from in situ observations by the instrumented C-130 aircraft, during the East Pacific Investigations of Climate (EPIC) about 600- 800 km offshore in the Intertropical Convergence Zone. Two cases were selected, one of which showed evidence that the CCN were modified by anthropogenic emissions. The results indicate that precipitation development in the deep, mixed phase clouds simulated is sensitive to the input of large concentrations of anthropogenic CCN. Precipitation development is delayed and its amount is reduced in the simulations when more CCN are included. This results from the modified autoconversion scheme that in turn causes a delay in the formation of hail and modifies its spatial distribution. Melting of hail is the most important contributor towards precipitation and a reduction in the amount of hail falling below the Freezing Level produces an appreciable decrease in the precipitation at the surface in the polluted case. Changes in the initial concentration of CCN do not appear to influence the storm strength in terms of updrafts and cloudtop height, suggesting little sensitivity to cloud dynamics.
DE: 0320 Cloud physics and chemistry
DE: 3311 Clouds and aerosols
DE: 3314 Convective processes
DE: 3354 Precipitation (1854)
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly