Abstract: We present a new procedure to describe the one-dimensional thermodynamical state and mineralogy of any Earth-like planetary mantle, with Mars as an example. The model parameters are directly related to expected results from a geophysical network mission, in this case electromagnetic, geodetic, and seismological processed observations supplemented with laboratory measurements. We describe the internal structure of the planet in terms of a one-dimensional model depending on a set of eight parameters: for the crust, the thickness and the mean density, for the mantle, the bulk volume fraction of iron, the olivine volume fraction, the pressure gradient, and the temperature profile, and for the core, its mass and radius. Currently, available geophysical and geochemical knowledge constrains the range of the parameter values. In the present paper, we develop the forward problem and present the governing equations from which synthetic data are computed using a set of parameter values. Among all Martian models fitting the currently available knowledge, we select eight candidate models for which we compute synthetic network science data sets. The synergy between the three geophysical experiments of electromagnetic sounding, geodesy, and seismology is emphasized. The stochastic inversion of the synthetic data sets will be presented in a companion paper.

Abstract: The Italian “Mario Zucchelli” Station (-74° 41? 55??.6997 N, 164° 06? 10??. 5887 E), situated at Terra Nova Bay, Northern Victoria Land, is equipped with a permanent Global Positioning System receiver (TNB1), continuously observing since 1998. “Mario Zucchelli” is an Antarctic experimental facility where a large number of scientific observations are carried out, either permanently or seasonally. In particular, an observatory devoted to atmospheric physics is located at Campo Icaro, 2.5 km from the base: it is a Clean Air Facility where several atmospheric measurements are carried out. Since 2000, long-wave radiation measurements are performed routinely using a Kipp&Zonen CNR-1 net radiometer. The GPS data set acquired over a six-year period spanning 2000–2005 by the permanent GPS station TNB1 is here analyzed, with the aim of retrieving the Precipitable Water (PW) content. Water vapour radiative effects on the thermal radiation balance of the atmosphere are of basic importance for the energy budget of the surface-atmosphere system in Antarctica, even though Precipitable Water assumes in general appreciably lower values than in other areas of our planet. Therefore, precise calculations and measurements of the mean long-wave radiation flux density reaching the surface at Terra Nova Bay are presented as a function of Precipitable Water, to give evidence of the relationship existing between this radiative balance term and the total atmospheric content of water vapour. The GPS-derived PW values are compared with radiosonde-derived PW values measured at Terra Nova Bay. The radiosounding data were analyzed by correcting the temperature data for the errors due to radiation and heat exchange processes and lag effects; the air relative humidity data were corrected for the errors and various dry bias following an accurate procedure recently developed by Tomasi et al. (2006) to reduce the errors and bias affecting the moisture measurements. The analysis strategies that have been applied to GPS and radiosonde data sets for computing PW are presented, including (i) the relation between the measured radiant-flux density and the GPS-derived PW, and (ii) the comparison with the predicted radiant-flux density derived by a model with five different profiles of temperature and humidity, computed from the set of radiosoundings performed at Terra Nova Bay. GPS- and radiosonde-derived water vapour contents at Terra Nova Bay show a good agreement over the whole sample period, with small discrepancies that will be opportunely discussed.

Abstract: Year-round composition of bulk and size-segregated aerosol was examined at a coastal Antarctic site (Dumont d'Urville). Sea-salt particles display a summer depletion of chloride relative to sodium, which reaches ?10%. The mass chloride loss is maximum on 1- to 3-?m-diameter particles, nitrate being often the anion causing the chloride loss. The summer SO42?/Na+ ratio exceeds the seawater value on submicron particles due to biogenic sulfate and on coarse particles due to ornithogenic (guano-enriched soils) sulfate and to heterogeneous uptake of SO2 (or H2SO4). HCl levels range from 47 ± 28 ng m?3 in the winter to 130 ± 110 ng m?3 in the summer, being close to the mass chloride loss of sea-salt aerosols. In the winter, sea-salt particles exhibit Cl?/Na+ and SO42?/Na+ mass ratios of 1.9 ± 0.1 and 0.13 ± 0.04, respectively. Resulting from precipitation of mirabilite during freezing of seawater, this sulfate-depletion-relative sodium takes place from May to October. From March to April, warmer temperatures and/or smaller sea ice extent offshore the site limit the phenomenon. A range of 14–50 ng m?3 of submicron sulfate is found, confirming the existence of nssSO42? in the winter at a coastal Antarctic site, highest values being found in the winters of 1992–1994 due to the Pinatubo volcanic input. Apart from these three winters, nssSO42? levels range between 15 and 30 ng m?3, but its origin is still unclear (quasi-continuous SO2 emissions from the Mount Erebus volcano or local wintertime dimethyl sulfide [DMS] oxidation, in addition to long-range transported by-product of DMS oxidation).

Abstract: The Model of Atmospheric Transport and Chemistry (MATCH) is used to simulate the transport of 222Rn using both European Centre for Medium-Range Weather Forecasts (ECMWF) winds and National Center for Environmental Prediction/National Center for Atmospheric Research (hereafter referred to as NCEP) reanalysis winds. These winds have the advantage of being based on observed winds but have the disadvantage that the subgrid-scale transport processes are not routinely archived. MATCH derives subgrid-scale mixing rates for the boundary layer using a nonlocal scheme and for moist convective mixing using one of two parameterizations (Tiedtke [1989] or Pan and Wu [1997]). This paper describes the ability of the model to recreate mixing rates of 222Rn using the forecast center winds. Radon 222 is a species with a continental crust source and a simple sink involving radioactive decay with an e-folding timescale of 5.5 days. This atmospheric constituent is therefore a good tracer for testing the vertical transport in the chemical transport model, as well as the horizontal transport from continental regions to remote oceanic regions. The various simulations of 222Rn are compared with observations as well as with each other, allowing an estimate of the uncertainty in transport due to uncertainties in the winds and subgrid-scale processes. The calculated vertical profiles over the western United States are somewhat similar to observed, and the upper tropospheric concentrations compare reasonably well in their spatial distribution with data collected during Tropospheric Ozone II (TROPOZ II), although the model values tend to be higher than observed values, especially in the upper troposphere. The model successfully simulates specific observed pollution events at Cape Grim. It has more difficulty at sites farther from continental source regions, although the model captures the seasonal structure of the pollution events at these sites (Macquarie Island, Amsterdam Island, Kerguelen Island, and Crozet Island). Inclusion of a moist convective mixing scheme in MATCH increases 222Rn concentrations in the upper troposphere by 50% compared to not having moist convective mixing, while surface concentrations do not appear to be very sensitive to moist convection. In addition, differences between the upper tropospheric concentrations of radon predicted using the ECMWF and NCEP winds can be 30% for large areas of the globe, due to either differences in the forecast center winds themselves or the moist convective mixing schemes used in conjunction with them. This has implications for model simulations of radiatively and chemically important trace species in the atmosphere.

Abstract: The information contained in polar nitrate has been an unresolved issue for over a decade. Here we demonstrate that atmospheric nitrate's oxygen isotopic composition (?17O-NO3) reflects stratospheric chemistry in winter and tropospheric chemistry in summer. Surface snow isotope mass balance indicates that nitrate oxygen isotopic composition is the result of a mixture of 25% stratospheric and 75% tropospheric origin. Analysis of trends in ?17O-NO3 in a 6 m snow pit that provides a 26-year record reveals a strong 2.70-year cycle that anticorrelates (R = ?0.77) with October–November–December column ozone. The potential mechanisms linking the records are either denitrification or increased boundary layer photochemical ozone production. We suggest that the latter is dominating the observed trend and find that surface ozone and ?17O-NO3 correlate well before 1991 (R = 0.93). After 1991, however, the records show no significant relationship, indicating an altered oxidative environment consistent with current understanding of a highly oxidizing atmosphere at the South Pole. The disappearance of seasonal ?17O-NO3 trends in the surface layer at depth remain unresolved and demand further investigation of how postdepositional processes affect nitrate's oxygen isotope composition. Overall, the findings of this study present a new paleoclimate technique to investigate Antarctic nitrate records that appear to reflect trends in stratospheric ozone depletion by recording tropospheric surface ozone variability.