Context

When the whole world wonders about the consequences of increased greenhouse gas emissions on climate, it becomes increasingly necessary to distinguish human-induced changes of the natural variability of atmosphere and ocean. The quality of forecasts of future climate change depends on it.

Among the natural causes that may have an effect on climate, solar variability is probably one of the most important. The Sun-Climate Observation Virtual Earth-Atmosphere (OV-SCAT) allow us to develop the study of relationships involved in bringing together communities working on these issues using the standards of the Virtual Observation

The influence of the sun on the atmosphere and the climate can be manifested in different ways:

• Variations in irradiance changes the total solar energy absorbed by the atmosphere and earth's surface and can influence the average temperature on the ground. The variation of the solar constant is limited to 0.1% on a 11-year solar cycle and thus the expected effect on climate is probably low. However, there are large uncertainties on the variation of the solar constant over longer periods and on the variability of the maxima.
• Variability of the solar flux over a 11-year cycle is manifested mainly in the ultraviolet (UV) spectrum and mainly at wavelengths below 250 nm where it may exceed 3%, and 20% to 50 % in the far UV. This spectrum does not reach the surface because it has entirely absorbed by the stratospheric ozone or oxygen. The solar UV radiation plays an important role against the stratosphere where it modifies the fields of temperature, pressure and wind and thus the propagation conditions of atmospheric sensors that couple the lower and upper layers of the atmosphere.
• Precipitation of solar particles in the polar regions are changing the chemical composition of the stratosphere, producing among other nitrogen oxides which partially destroy the ozone layer and thus alter its radiative balance.
• Galactic cosmic rays ionize the atmosphere and thus play a role in the global electrical circuit. They can promote the formation of condensation nuclei and thus affect the formation and lifetime of clouds. The cosmic ray flux is modulated by the solar wind varies with solar activity for 11 years.
• The geomagnetic activity, closely related to solar activity modulates the flux of energetic particles entering the upper atmosphere. Interaction with the lower atmosphere could go through different processes involving UV radiation, atmospheric chemistry and atmospheric electrical circuit.

Mechanisms may be involved in solar-climate are complex and advance their understanding is necessary both to document the parameters characterizing the solar activity, to understand the origin, and secondly to properly represent these mechanisms in climate models.

Objectives

Le VO-SCAT 's mission :

• to participate in the animation of the scientific community around the theme "sun-atmosphere relationship"
• to develop its own Virtual Observatory and thus its own tools as part of European and international collaboration: through a local database and links to the archive centers and existing tools (Virtual Observatory Astonomique, International Planetary Data Alliance Europlanet-Integrated and Distributed Information Services, Spase-Virtual Observatory for space plasmas, Hellios-Virtual Observatory Solar VAMDX, etc ...) on the principle of interoperability of databases

VO-SCATOV-SCAT falls, therefore, in a thematic combinations of existing measurement systems for the most part and with existing protocols and defined as part of their own "SOERE" (Systmes Observation and Experimentation , in the long term, for Environmental Research) or their associated SOERE. This is a multi-site SOERE whose coherence and complementarity is entered in the title and the scientific objective.

Its operation is based mainly on existing research activities and is now a priority in the interpretation of our data. Our main objective will be to give a concrete evaluation, comprehensive and conclusive in terms of what SOERE, so in 10 years, by the establishment of a Virtual Observatory around this theme. By definition, a Virtual Observatory should be open and interoperable, which is the second objective that we set ourselves. The filing does not bear but to that of the partners or SOERE which they belong.

Apart PICARD PICARD and ground, the other components of this SOERE are existing and functioning. However, the interaction between these databases or services is currently not possible to completely and it will be one of the roles of the service implementation using modeling (LMDz, models and LSCE / IPSL or, etc. ..) which will be an important part of this SOERE because it remains the most effective tool for the exploitation of our data in our multi-disciplinary fields

Moreover OV-SCAT will use data and tools available on the solar and geomagnetic activity on the Virtual Observatory and atomic physics applied to molecular atmospheres through existing services Observations, particularly in the Astronomy-Astrophysics field.

VO-SCAT is a service of the OVSQ. The charge for this service: Alain M Sarkisian's mission is to set up a scientific council to pilot this service. Members (10 people) of the council appointed on the nomination of the partner laboratories and the USO, will meet once or twice a year to the priorities and service objectives.