Parameterizing Venus' aerosol particle size distribution
Abstract
Recent studies of Venus Express VMC data have shown definitive links between changes in Venus' zonal wind speed, topography and the observed 365 nm cloud top albedo brightness level (Bertaux et al. 2016). HST observations obtained during the Venus Express era (Jessup et al. 2015) provided a spatially resolved record of Venus' 245 nm cloud top brightness levels from dawn to noon in the 45S to 30N latitude region at longitudes between 355E to 0-45E (downwind of Aphrodite) and at 85-140E longitudes (which extends over the Aphrodite mountain range). These observations indicate that Venus' 245 nm brightness level darkened towards the equator, following the expected latitudinal gradient. In addition to that, in the longitude range between 350E and 0E, after 10 a.m. the cloud top albedo darkened with local time towards local noon. Among the two longitude regions observed by HST, this is the only longitude range where there was any evidence that local time had an impact on the relative cloud top brightness—and it is also a region where a consistent increase in the equatorial wind speed with longitude was observed by VMC. As alluded to above, brightening and darkening patterns in the 365 nm cloud top albedo are best explained by atmospheric upwelling and downwelling resulting from atmospheric stretching and compression which occurs as the zonal wind increases and decreases with longitude. We plan to use a microphysical model to complete a series of sensitivity tests to determine the impact of vertical mixing rates (and T) on aerosol particle size, abundance and scale height and the resulting 245 nm cloud top opacity. These results can provide a basis for tracking and predicting changes in the cloud top opacity as a function of local time and windspeed on a global basis. This information may have a significant impact on our understanding of the global distribution of Venus' atmospheric radiant energy budget, as well as shed some light on the origin of the NUV absorption in Venus atmosphere.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.P43E2930J
- Keywords:
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- 5210 Planetary atmospheres;
- clouds;
- and hazes;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5215 Origin of life;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5225 Early environment of Earth;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 6207 Comparative planetology;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS