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G. I. Barenblatt and G. S. Golitsyn

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G. I. Barenblatt and G. S. Golitsyn

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An attempt is made to describe the local structure of a dust storm during its mature stage, when the storm can be considered as steady. Vertical profiles of wind, dust concentration and temperature are obtained by using boundary layer equations for a fluid carrying heavy particles and taking into account the thermal stratification. The nondimensional parameters which determine the structure of the flow are the Richardson and the Kolmogorov flux numbers, the latter describing the part of turbulent energy spent on suspension of the dust particles. The work done by the flow for suspension is always positive, which results in a decrease of the turbulent energy and an increase in the stability of the flow. As a result, other conditions being equal, the flow is accelerated. Observational data are presented which confirm this effect.

A self-similar singular solution describes the saturated flow which carries the largest possible amount of dust. Other solutions approach this limiting one with increasing attitude. It is shown that the finer the dust, the slower is its concentration decrease with height. The importance of the thermal stratification in determining the flow structure increases with height. Under thermally stable conditions the dust concentration decreases exponentially with height, while for convective conditions it approaches a constant value. The latter helps to explain why Martian global dust storms always begin near the time of perihelion when the insolation is maximal and the atmosphere most unstable.

Results of the theory are applied to dust storm conditions for Mars and Earth. Estimates show that for the mature stage of the Martian global storms the dynamical effect of the dust can be substantial, especially for early stages of the storms. For the Earth this effect can be quite pronounced, and perhaps explains the extremely strong winds reported for many extensive dust storms.

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G. S. Golitsyn and A. S. Gurvich

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Jean-Daniel Paris, Philippe Ciais, Philippe Nédélec, Andreas Stohl, Boris D. Belan, Mikhail Yu. Arshinov, Claire Carouge, Georgii S. Golitsyn, and Igor G. Granberg

There are very few large-scale observations of the chemical composition of the Siberian airshed. The Airborne Extensive Regional Observations in Siberia (YAKAEROSIB) French–Russian research program aims to fill this gap by collecting repeated aircraft high-precision measurements of the vertical distribution of CO2, CO, O3, and aerosol size distribution in the Siberian troposphere on a transect of 4,000 km during campaigns lasting approximately one week. This manuscript gives an overview of the results from five campaigns executed in April 2006, September 2006, August 2007, and early and late July 2008. The dense set of CO2 vertical profiles, consisting of some 50 profiles in each campaign, is shown to constrain large-scale models of CO2 synoptic transport, in particular frontal transport processes. The observed seasonal cycle of CO2 in altitude reduces uncertainty on the seasonal covariance between vegetation fluxes and vertical mixing, known as the “seasonal rectifier effect.” Regarding carbon dioxide, we illustrate the potential of the YAKAEROSIB data to cross-validate a global CO2 transport model. When compared to the CO2 data, the model is likely to be biased toward too-weak mixing in winter, as it overestimates the CO2 vertical gradient compared to the observation. Regarding pollutants, we illustrate through case studies the occurence of CO enhancements of 30–50 ppb above background values, coincident with high O3. These high CO values correspond to large-scale transport of anthropogenic emissions from Europe, and to wildfires in the Caspian Sea area, over much cleaner Arctic air (September 2006). An occurence of extremely high CO values above 5,000 km in eastern Siberia is found to be related to the very fast transport and uplift of Chinese anthropogenic emissions caused by a cold front (April 2006).

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