EIS/Hinode observations of Doppler flow seen through the 40 arcsec wide slit

The Extreme ultraviolet Imaging Spectrometer (EIS) on board Hinode is the first solar telescope to obtain wide slit spectral images that can be used for detecting Doppler flows in transition region and coronal lines on the Sun and to relate them to their surrounding small scale dynamics. We select EIS lines covering the temperature range 6x10^4 K to 2x10^6 K that give spectrally pure images of the Sun with the 40 arcsec slit. In these images Doppler shifts are seen as horizontal brightenings. Inside the image it is difficult to distinguish shifts from horizontal structures but emission beyond the image edge can be unambiguously identified as a line shift in several lines separated from others on their blue or red side by more than the width of the spectrometer slit (40 pixels). In the blue wing of He II, we find a large number of events with properties (size and lifetime) similar to the well-studied explosive events seen in the ultraviolet spectral range. Comparison with X-Ray Telescope (XRT) images shows many Doppler shift events at the footpoints of small X-ray loops. The most spectacular event observed showed a strong blue shift in transition region and lower corona lines from a small X-ray spot that lasted less than 7 min. The emission appears to be near a cool coronal loop connecting an X-ray bright point to an adjacent region of quiet Sun. The width of the emission implies a line-of-sight velocity of 220 km/s. In addition, we show an example of an Fe XV shift with a velocity about 120 km/s, coming from what looks like a narrow loop leg connecting a small X-ray brightening to a larger region of X-ray emission.Comment: 12 pages, 8 figures, to be published in Solar Physic

A geostationary thermal infrared sensor to monitor the lowermost troposphere: O₃ and CO retrieval studies

This paper describes the capabilities of a nadir thermal infrared (TIR) sensor proposed for deployment onboard a geostationary platform to monitor ozone (O3) and carbon monoxide (CO) for air quality (AQ) purposes. To assess the capabilities of this sensor we perform idealized retrieval studies considering typical atmospheric profiles of O3 and CO over Europe with different instrument configuration (signal to noise ratio, SNR, and spectral sampling interval, SSI) using the KOPRA forward model and the KOPRA-fit retrieval scheme. We then select a configuration, referred to as GEO-TIR, optimized for providing information in the lowermost troposphere (LmT; 0–3 km in height). For the GEO-TIR configuration we obtain ~1.5 degrees of freedom for O3 and ~2 for CO at altitudes between 0 and 15 km. The error budget of GEO-TIR, calculated using the principal contributions to the error (namely, temperature, measurement error, smoothing error) shows that information in the LmT can be achieved by GEO-TIR. We also retrieve analogous profiles from another geostationary infrared instrument with SNR and SSI similar to the Meteosat Third Generation Infrared Sounder (MTG-IRS) which is dedicated to numerical weather prediction, referred to as GEO-TIR2. We quantify the added value of GEO-TIR over GEO-TIR2 for a realistic atmosphere, simulated using the chemistry transport model MOCAGE (MOd`ele de Chimie Atmospherique `a Grande Echelle). Results show that GEO-TIR is able to capture well the spatial and temporal variability in the LmT for both O3 and CO. These results also provide evidence of the significant added value in the LmT of GEO-TIR compared to GEO-TIR2 by showing GEO-TIR is closer to MOCAGE than GEO-TIR2 for various statistical parameters (correlation, bias, standard deviation)

Turbulent Transport at the Thermal Internal Boundary Layer Top: Wavelet Analysis of Aircraft Measurements.

Abstract not availableJRC.(EI)-Environment Institut

Interactions surface continentale/atmosphère : l'expérience HAPEX-Sahel

La variabilité spatiale du flux net et des flux de surface, de chaleur sensible et chaleur latente, obtenus par avion et calculés par la méthode des corrélations est présentée pour deux journées caractéristiques de l'expérience Hapex Sahel : l'une en saison des pluies, l'autre en début de période sèche. L'étude des échelles d'intégration des flux calculés montre que la précision est très fortement dégradée en saison sèche et que le flux d'évaporation se comporte de manière tout à fait marginale par rapport au flux de chaleur sensible ou à celui de la chaleur latente en conditions humides. Cette caractéristique se traduit par une très forte hétérogénéité spatiale à l'échelle d'un champ de 90 km x 75 km. Parallèlement à celle des flux, la variabilité spatiale de certains paramètres, accessibles par l'avion et susceptibles de contrôler les transferts, est commentée. (Résumé d'auteur

Measuring atmospheric composition change

Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions. © 2009 Elsevier Ltd. All rights reserved.SCOPUS: re.jinfo:eu-repo/semantics/publishe