Wednesday, 22 January 2014 at 12:00 PM:

Where: Phenix 123

Speaker: Nicholas G. Heavens

From: Hampton University Department of Atmospheric and Planetary Sciences

Title: Seasonal and Diurnal Variability of Detached Dust Layers in the Tropical Martian Atmosphere

Widespread non-uniform vertical mixing of dust in Mars’s tropical atmosphere (in the form of features called “detached dust layers” or DDLs) complicates fundamental understanding of dust injection on Mars as well as atmospheric modeling. Using retrievals from observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter (MRO), I characterize the seasonal, diurnal, and geographic variability of DDL activity. I define and use a DDL index to reduce DDL structure in a retrieved profile to a single parameter and isolate spatial variability in DDLs. I also use near-repeat observational coverage at semidiurnal separation by MRO-MCS to estimate diurnal variability in the dust distribution, which is particularly useful when the DDL index cannot be reliably assessed. My analysis suggests that dust injection above the boundary layer, which forms DDLs, is a spatially ubiquitous phenomenon in the tropics during the daytime, even when the zonal average dust distribution appears uniformly mixed, and is more intense in northern spring and summer than in southern spring and summer. Geographic variability in the nightside vertical dust distribution does not always correlate with the observed or inferred dayside vertical dust distribution, implying that there is spatial and seasonal variability in the intensity of dust deposition/removal processes. Dust removal between dayside and nightside observation is especially intense over the Tharsis Montes during northern spring and summer but cannot be entirely explained within the current understanding of dust removal processes.

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