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A parameterization scheme for the dry deposition of aerosol particles for use in tracer transport models is presented. Expressions of the particle deposition velocities relative to the bottom transport model level are derived for smooth surfaces, surfaces with bluff roughness elements, ocean surfaces, and vegetative canopies. The scheme is applied to a general circulation model to calculate the deposition velocities of ambient tropospheric aerosols. The calculated deposition velocities show a strong dependence upon the wind field in the bottom model level, the particle size distribution, and the surface type.
Photochemical models of tropospheric trace species typically simulate the effects of wet removal of soluble species from the atmosphere through a first-order rainout parameterization, which is independent of the species solubility and constant in time. In this work a modified first-order rainout parameterization is proposed that is a function of the species' solubility and takes into account the intermittent nature of atmospheric wet removal. In the case of a highly soluble species, such as HNO3, the inclusion of the effects of intermittent rainout in the parameterization leads to averaged rainout lifetimes considerably higher than ones used in most photochemical models. For illustrative purposes this parameterization is applied to a one-dimensional steady state model with parameterized eddy diffusion, although in principle it can be u...
In this work, we have studied the temporal evolution of some properties of a sample of superactive regions with the aim to single out the most significant for flare activity forecasting. We have investigated properties of 14 superactive regions, observed between January 1st 2000 and December 31st 2006 with MDI/SOHO instrument and characterized by a particularly intense flare activity during their passage on the solar disk. We have analyzed the temporal evolution of fractal and multifractal properties of photospheric magnetic fields, namely the generalized fractal dimension and the cntribution and dimensionality diversities, as well as the potential unstable volumes of magnetic discontinuities above the studied ARs. Correlations of these quantities with the flare index, which provides information about the flare activity of a region, ...
Comment: In Proceedings of the 25th NSO Workshop: Chromospheric Structure and Dynamics
We have investigated properties of photospheric Bright Points (BPs) observed in an Active Region during its decay phase and in a quiet Sun region. We have analyzed two sets of photospheric observations taken with IBIS (Interferometric Bidimensioal Spectrometer) at the NSO Dunn Solar Telescope. The first set consists of spectral data acquired in the Fe I 709.0 nm and Ca I 854.2 nm lines and simultaneous broad-band and of G-band observations. The second set consists of spectro-polarimetric observations in the Fe I 630.15 nm - 630.25 nm doublet and simultaneous white light and G-band observations. The relation between BP filling factor and RMS image contrast indicates that, on average, BPs cover up to 3% of the solar surface outside Active Regions. The relation between area and intensity values of the features identified on both data se...
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