Regolith-atmosphere exchange of water in Mars' recent past

We investigate the exchange of water vapour between the regolith and atmosphere of Mars, and how it varies with different orbital parameters, atmospheric dust contents and surface water ice reservoirs. This is achieved through the coupling of a global circulation model (GCM) and a regolith diffusion model. GCM simulations are performed for hundreds of Mars years, with additional one-dimensional simulations performed for 50 kyr. At obliquities ε = 15° and 30°, the thermal inertia and albedo of the regolith have more control on the subsurface water distribution than changes to the eccentricity or solar longitude of perihelion. At ε = 45°, atmospheric water vapour abundances become much larger, allowing stable subsurface ice to form in the tropics and mid-latitudes. The circulation of the atmosphere is important in producing the subsurface water distribution, with increased water content in various locations due to vapour transport by topographically-steered flows and stationary waves. As these circulation patterns are due to topographic features, it is likely the same regions will also experience locally large amounts of subsurface water at different epochs. The dustiness of the atmosphere plays an important role in the distribution of subsurface water, with a dusty atmosphere resulting in a wetter water cycle and increased stability of subsurface ice deposits

Agricultural taxation and intersectoral resource transfers

The paper is a survey of recent developments on this topic. It uses a two-sector (modern and traditional) model as the "basic framework for analysis. Agriculture's role in development is reviewed briefly, as are the methods of transferring resources from agriculture: transfers on private account, government tax and expenditure policies, and policies aimed at changing the terms of trade of the agricultural sector. The bulk of the paper reviews the recent experience of developing countries and the literature related to this topic. It is organized around three basic themes. First is a review of the policies including tariff protection that have influenced the domestic terms of trade between agriculture and industry and the effects of those policies on the agricultural sector (which has usually been left to pay the bill for protected industrialization). Second is a discussion of the implications of productivity growth (or the lack of it) in both the agricultural sector and in protected import substituting industries for the questions of resource transfers and of general economic growth in both sectors. Third, the growing concern with unemployment and income distribution is reviewed in connection with the choice of policies to tax agriculture and transfer resources to industry. The paper suggests a number of elements of an improved system of taxing the agricultural sector to transfer resources both to government and to the non-agricultural sectors while simultaneously reducing the burden on agriculture from misallocation effects of the policies. Attention is also given to policies that would improve the growth rate of employment and the distribution of income. Particular attention in the paper is given to the effects of foreign trade policies on income transfers

Martian mesoscale and microscale wind variability of relevance for dust lifting

Background: Mars si both a windy and dusty environment. Ariborne dust is a crucial climate component on Mars. It impacts atmospheric circulations at large-, meso- and micro-scales, which in turn control dust lifting from the surface and transport in the atmosphere. Dust lifting processes and feedbacks on atmospheric circulations are currently not well understood. Method: Our purpose is to show how mesoscale models and large-eddy simulations help to explore small-scale circulation patterns which are potentially important for lifting dust into the atmosphere but which are unresolved by global climate models. We focus on variations of friction velocity, u*, relevant for dust lifting, in particular investigating maximum values and the spatial and temporal variability of u*. Conclusion: Meteorological scales between 100 km and 10 km can be studied by high-resolution global circulation and limited-area mesoscale models, which both show strong topographic control of the daytime and nighttime near-surface winds. Scales below 10 km and 1 km are dominated by turbulent gusts and dust devils, two distinct convective boundary layer processes likely to lift dust from the surface. In low-latitude regions, boundary layer depth and friction velocity u* are correlated with surface altimetry. Further studies will be carried out to parameterize lifting by boundary layer processes and dust radiative effects once transported in the atmosphere

Transient teleconnection event at the onset of a planet-encircling dust storm on Mars

We use proper orthogonal decomposition (POD) to study a transient teleconnection event at the onset of the 2001 planet-encircling dust storm on Mars, in terms of empirical orthogonal functions (EOFs). There are several differences between this and previous studies of atmospheric events using EOFs. First, instead of using a single variable such as surface pressure or geopotential height on a given pressure surface, we use a dataset describing the evolution in time of global and fully three-dimensional atmospheric fields such as horizontal velocity and temperature. These fields are produced by assimilating Thermal Emission Spectrometer observations from NASA's Mars Global Surveyor spacecraft into a Mars general circulation model. We use total atmospheric energy (TE) as a physically meaningful quantity which weights the state variables. Second, instead of adopting the EOFs to define teleconnection patterns as planetary-scale correlations that explain a large portion of long time-scale variability, we use EOFs to understand transient processes due to localised heating perturbations that have implications for the atmospheric circulation over distant regions. The localised perturbation is given by anomalous heating due to the enhanced presence of dust around the northern edge of the Hellas Planitia basin on Mars. We show that the localised disturbance is seemingly restricted to a small number (a few tens) of EOFs. These can be classified as low-order, transitional, or high-order EOFs according to the TE amount they explain throughout the event. Despite the global character of the EOFs, they show the capability of accounting for the localised effects of the perturbation via the presence of specific centres of action. We finally discuss possible applications for the study of terrestrial phenomena with similar characteristics

OpenMARS: A global record of martian weather from 1999 2015

The Open access to Mars Assimilated Remote Soundings (OpenMARS) dataset is a reanalysis product combining past spacecraft observations with a Mars Global Circulation Model (GCM). The OpenMARS product is a global surface/atmosphere reference database of surface and atmospheric properties for almost nine Mars years that can be used by Mars scientists and engineers interested in global surface/atmospheric conditions and the physical, dynamical and chemical behaviour of the atmosphere for the recent past on Mars. In the OpenMARS dataset, spacecraft observations of temperature, dust and water vapour from the Thermal Emission Spectrometer (TES) instrument on the NASA Mars Global Surveyor spacecraft, temperature and dust from the Mars Climate Sounder (MCS) instrument aboard NASA's Mars Reconnaissance Orbiter spacecraft and ozone from the Spectrometer for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument on the European Space Agency (ESA) Mars Express orbiter are combined with a Mars GCM used at the Open University

Data assimilation for the Martian atmosphere using MGS Thermal Emission Spectrometer observations

From the introduction: Given the quantity of data expected from current and forthcoming spacecraft missions to Mars, it is now possible to use data assimilation as a means of atmospheric analysis for the first time for a planet other than the Earth. Several groups have described plans to develop assimilation schemes for Mars [Banfield et al., 1995; Houben, 1999; Lewis and Read, 1995; Lewis et al., 1996, 1997; Zhang et al., 2001]. Data assimilation is a technique for the analysis of atmospheric observations which combines currently valid information with prior knowledge from previous observations and dynamical and physical constraints, via the use of a numerical model. Despite the number of new missions, observations of the atmosphere of Mars in the near future are still likely to be sparse when compared to those of the Earth, perhaps comprising one orbiter and a few surface stations at best at any one time. Data assimilation is useful as a means to extract the maximum information from such observations, both by a form of interpolation in space and time using model constraints and by the combination of information from different observations, e.g. temperature profiles and surface pressure measurements which may be irregularly distributed. The procedure can produce a dynamically consistent set of meteorological fields and can be used directly to test and to refine an atmospheric model against observations

Assimilation of TES data from the Mars Global Surveyor scientifc mapping phase

The Thermal Emission Spectrometer (TES)aboard Mars Global Surveyor has produced data which cover almost two Martian years so far (during its scientific mapping phase). Thermal profiles for the atmosphere below 40 km and total dust opacities can be retrieved from TES nadir spectra and assimilated into a Mars general circulation model (MGCM), by using the assimilation techniques described in detail by Lewis et al. (2002). This paper describes some preliminary results from assimilations of temperature data from the period Ls=141°- 270° corresponding to late northern summer until winter solstice on Mars. Work in progress is devoted to assimilate both temperature and total dust opacity data for the full period for which they are already available