Abstract: We present data of nine Automatic Weather Stations (AWS), which are located in Dronning Maud Land (DML), East Antarctica, since the austral summer of 1997. Potential temperature and wind speed are maximum at the sites with the steepest surface slope, i.e., at the edge of the Antarctic plateau. Specific humidity and accumulation decrease with elevation and distance from the coast. The annual average energy gain at the surface from the downward sensible heat flux varies between ?3 W m?2 and ?25 W m?2, with the highest values at the sites with the largest surface inclination and wind speeds. The net radiative flux is negative and largely balances this sensible heat flux and ranges from ??2 W m?2 to ??28 W m?2; maximum values can be linked to maxima in surface slope and wind speed, and suggest a strong connection between the heat budget and the katabatic flow in DML. The average latent heat flux is generally small and negative (??1 W m?2) indicating a slight net mass loss through sublimation.

Abstract: We present an event of simultaneous observations of the northern and southern middle-altitude polar cusps by the Polar spacecraft and Cluster fleet that occurred on 23 September 2004. We examine the possible asymmetries in the fields and plasma parameters, although the proximity of the equinox should limit these asymmetries. Ion sensors reveal two dispersions in both cusps, and data analysis leads to the conclusion that those dispersions are due to pulsed reconnection at a single X-line, which runs along the subsolar magnetopause. While the electromagnetic and particle energy fluxes injected in both cusp are globally very similar, we report significant differences in ion dispersions, width of the low-latitude boundary layer, and peak convection velocities. We ascribe these differences to the dipole tilt that introduces an asymmetry in the magnetosheath flow at the exterior cusps.

Abstract: We present an assimilation system for atmospheric carbon dioxide (CO2) using a Global Eulerian–Lagrangian Coupled Atmospheric model (GELCA), and demonstrate its capability to capture the observed atmospheric CO2 mixing ratios and to estimate CO2 fluxes. With the efficient data handling scheme in GELCA, our system assimilates non-smoothed CO2 data from observational data products such as the Observation Package (ObsPack) data products as constraints on surface fluxes. We conducted sensitivity tests to examine the impact of the site selections and the prior uncertainty settings of observation on the inversion results. For these sensitivity tests, we made five different site/data selections from the ObsPack product. In all cases, the time series of the global net CO2 flux to the atmosphere stayed close to values calculated from the growth rate of the observed global mean atmospheric CO2 mixing ratio. At regional scales, estimated seasonal CO2 fluxes were altered, depending on the CO2 data selected for assimilation. Uncertainty reductions were determined at the regional scale and compared among cases. As measures of the model–data mismatch, we used the model–data bias, root-mean-square error, and the linear correlation. For most observation sites, the model–data mismatch was reasonably small. Regarding regional flux estimates, tropical Asia was one of the regions that showed a significant impact from the observation network settings. We found that the surface fluxes in tropical Asia were the most sensitive to the use of aircraft measurements over the Pacific, and the seasonal cycle agreed better with the results of bottom-up studies when the aircraft measurements were assimilated. These results confirm the importance of these aircraft observations, especially for constraining surface fluxes in the tropics.

Abstract: We present a technique to measure the magnetic field-aligned vorticity of mesoscale plasma flows in the F region ionosphere using line-of-sight velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Vorticity is often used as a proxy for magnetic field-aligned current (FAC) intensity in the ionosphere but also provides information about turbulent processes in the ionosphere and magnetosphere. Using 6 years (2000–2005 inclusive) of vorticity measurements made by six SuperDARN radars in the Northern Hemisphere, we have compiled, for the first time, maps of average vorticity across the northern polar ionosphere. These maps have been subdivided according to different seasonal and interplanetary magnetic field (IMF) conditions. The variations in the morphology of the vorticity maps with IMF direction match very closely those seen in maps of average FAC intensity (determined using different methods and instrumentation), suggesting that vorticity is a good proxy for FAC in an averaged sense. The variations in the morphology of the vorticity maps with season show differences from those seen in the FAC maps, illustrating that ionospheric conductance plays a major role in determining the differences between measurements of vorticity and FAC.

Abstract: We present a statistical analysis of ULF (1-100 mHz) geomagnetic measurements conducted during years 2003-2006 at the Italian/French base of Concordia at Dome C, close to the geomagnetic pole, and at the Italian base «Mario Zucchelli» at Terra Nova Bay, also located in the polar cap, but at lower latitude. Our analysis shows that high latitude ULF pulsation power is largely controlled by the solar wind speed. At Terra Nova Bay the power shows a maximum at local noon, clearly related to cusp and closed field lines phenomena. At few mHz, the polarization pattern indicates field line resonances driven, just equatorward with respect to the station, by waves propagating tailward; the polarization of higher frequency pulsations, mostly originated from interplanetary upstream waves, suggests waves propagating sunward from the night sector. At Dome C the wave power shows a small enhancement in the local morning, more pronounced for mid-frequency pulsations; the polarization pattern, at all frequencies, appears to indicate waves propagating sunward from the night sector, suggesting a propagation channel to the ground via the magnetotail lobes.