Orbital Observations of Dust Lofted by Daytime Convective Turbulence

Over the past several decades, orbital observations of lofted dust have revealed the importance of mineral aerosols as a climate forcing mechanism on both Earth and Mars. Increasingly detailed and diverse data sets have provided an ever-improving understanding of dust sources, transport pathways, and sinks on both planets, but the role of dust in modulating atmospheric processes is complex and not always well understood. We present a review of orbital observations of entrained dust on Earth and Mars, particularly that produced by the dust-laden structures produced by daytime convective turbulence called “dust devils”. On Earth, dust devils are thought to contribute only a small fraction of the atmospheric dust budget; accordingly, there are not yet any published accounts of their occurrence from orbit. In contrast, dust devils on Mars are thought to account for several tens of percent of the planet’s atmospheric dust budget; the literature regarding martian dust devils is quite rich. Because terrestrial dust devils may temporarily contribute significantly to local dust loading and lowered air quality, we suggest that martian dust devil studies may inform future studies of convectively-lofted dust on Earth

Simulation of the Madden-Julian oscillation in a coupled general circulation model. Part II: The role of the basic state

In Part I of this study it was shown that air–sea coupling had a positive impact on some aspects of the simulation of the Madden–Julian oscillation (MJO) by a GCM. However, errors in the basic-state climate of that GCM appeared to be preventing the MJO-related convection from propagating into the west Pacific. In this paper, the actual impact of these errors will be addressed. An integration of a flux-adjusted version of the coupled model has been performed, which has reduced basic-state errors in the west Pacific. In this version of the coupled GCM the MJO does propagate into the west Pacific. The simulation of the MJO by a coupled model with the same atmospheric component but a different ocean GCM is also analyzed. This coupled GCM has similar systematic errors in low-level zonal wind and precipitation to the model studied in Part I, but with warmer SSTs. Results from this experiment, together with the other available evidence, suggest that it is the errors in the lowlevel zonal wind component in the west Pacific that prevent the MJO from propagating into this region in the coupled GCM rather than the errors in absolute values of SST