Localized precipitation and runoff on Mars

We use the Mars Regional Atmospheric Modeling System (MRAMS) to simulate lake storms on Mars, finding that intense localized precipitation will occur for lake size >=10^3 km^2. Mars has a low-density atmosphere, so deep convection can be triggered by small amounts of latent heat release. In our reference simulation, the buoyant plume lifts vapor above condensation level, forming a 20km-high optically-thick cloud. Ice grains grow to 200 microns radius and fall near (or in) the lake at mean rates up to 1.5 mm/hr water equivalent (maximum rates up to 6 mm/hr water equivalent). Because atmospheric temperatures outside the surface layer are always well below 273K, supersaturation and condensation begin at low altitudes above lakes on Mars. In contrast to Earth lake-effect storms, lake storms on Mars involve continuous precipitation, and their vertical velocities and plume heights exceed those of tropical thunderstorms on Earth. Convection does not reach above the planetary boundary layer for lakes O(10^2) mbar. Instead, vapor is advected downwind with little cloud formation. Precipitation occurs as snow, and the daytime radiative forcing at the land surface due to plume vapor and storm clouds is too small to melt snow directly (<+10 W/m^2). However, if orbital conditions are favorable, then the snow may be seasonally unstable to melting and produce runoff to form channels. We calculate the probability of melting by running thermal models over all possible orbital conditions and weighting their outcomes by probabilities given by Laskar et al., 2004. We determine that for an equatorial vapor source, sunlight 15% fainter than at present, and snowpack with albedo 0.28 (0.35), melting may occur with 4%(0.1%) probability. This rises to 56%(12%) if the ancient greenhouse effect was modestly (6K) greater than today.Comment: Submitted to JGR Planet

African Linguistics in Central and Eastern Europe, and in the Nordic Countries

Non peer reviewe

Language endangerment and language documentation in Africa

Non peer reviewe

Laboratory simulation of the release of subsurface water and brine on to the surface of Mars and icy satellites.

For most extraterrestrial studies of volcanic and aqueous activity, the processes involved can be studied only by theoretical modelling, simula-tion in analogue experiments, or examination of the geomorphological and geological record. The last of these approaches is limited by the spatial resolution and coverage of satellite data, or to the very limited localities where rovers or landers have been deployed (e.g., Viking, Mars Exploration Rovers). There have been no observed releases of water on to the surface of Mars. Therefore, a series of experiments should add insight to our understanding of this phenomenon. The experiments are intended to be primarily a study of the temperature-pressure relationships and how they affect phase changes in both pure wat

Formation of Mangala Valles outflow channel, Mars: morphological development and water discharge and duration estimates.

The morphology of features on the floor of the Mangala Valles suggests that the channel system was not bank‐full for most of the duration of its formation by water being released from its source, the Mangala Fossa graben. For an estimated typical 50 m water depth, local slopes of sin α = ∼0.002 imply a discharge of ∼1 × 107 m3 s−1, a water flow speed of ∼9 m s−1, and a subcritical Froude number of ∼0.7–0.8. For a range of published estimates of the volume of material eroded from the channel system this implies a duration of ∼17 days if the sediment carrying capacity of the ∼15,000 km3 of water involved had been 40% by volume. If the sediment load had been 20% by volume, the duration would have been ∼46 days and the water volume required would have been ∼40,000 km3. Implied bed erosion rates lie in the range ∼1 to ∼12 m/day. If the system had been bank‐full during the early stages of channel development the discharge could have been up to ∼108 m3 s−1, with flow speeds of ∼15 m s−1 and a subcritical Froude number of ∼0.4–0.5

War, peace and free trade: the political economy of war and the US-Colombia Free Trade Agreement

A dissertation submitted in part-fulfilment of the requirements of the degree of M.Sc. in Globalisation and Latin-American Development, 2008-9

Volcanism on Venus

International audienc

Venus surface as revealed by VIRTIS data

International audienc

Venus surface as revealed by VIRTIS data

International audienc