Databases developed and maintained at LMD
Radiative transfer modelling research and application has led the ARA team to produce several data bases, in particular to answer the requirements raised by new generation space-borne instruments. These databases are made available to the research community and are regularly maintained and updated by the team.
The GEISA data bank on molecular spectroscopy
Atmospheric radiation analysis requires accurate description of spectral properties of atmospheric gases and particles. The spectroscopic data bank GEISA was initiated in 1975.
In its 2011 version, are described the spectral properties of about 3,794,426 lines corresponding to 50 molecules and 111 isotopic species covering the range 10-6 to 35877 cm-1 (10-11 to 0.28 µm). Also archived are measurements of presently known aerosol complex refractive indices (GEISA-aerosols), as well as spectral data (cross-sections) for 50 complex molecules as freons (GEISA-CFC), in the Infrared and UV-Visible as well. GEISA is presently the largest spectral bank in the world. It is used on-line by more than 300 laboratories working in the domains of atmospheric physics, astronomy and astrophysics, and planetology. GEISA has recently been declared the reference basis by the international working group in charge of the instrument IASI.
GEISA is freely accessible from the CNRS/CNES/IPSL expertise center website (http://ether.ipsl.jussieu.fr/).
The Thermodynamic Initial Guess Retrieval (TIGR) data bank
Inversion algorithms developed in the ARA team rely on a priori information an important part of which has been summarized within a representative ensemble of meteorological situations, the so-called "Thermodynamic Initial Guess Retrieval ( TIGR)" climatological data base. At present, TIGR includes 2311 atmospheric situations (extracted from tens of thousands of radiosoundings and satellite soundings) described by their vertical profiles of temperature, water vapour, and ozone. For each situation are computed, using the 4A model, the transmittances and radiances for all the channels of the space instrument considered and this for all the conditions of observation (viewing angle, surface pressure, type of the surface, etc.). There exist TIGR data bases for numerous sounders: TOVS (improved in 2002), AIRS/AMSU/Aqua (2002), IIR/Calipso-Cena (2004), Seviri/Meteosat (2004) and IASI/AMSU/MetopA (2007).
For application of 2nd generation instruments, a new version of TIGR has recently been developed offering more situations (up to 11,000 extracted from ECMWF reanalysis) and a better pressure discretization (60 levels instead of 40).
The Analyzed RadioSoundings Archive (ARSA) database
Meteorological and climate applications of satellite observations require that biases resulting from physics or model limitations, slow instrumental drifts, have been quantified and eliminated. These biases are determined from comparisons between observations for large sets of well described atmospheric situations and forward model simulations. A way of getting this atmospheric description is to use in-situ measurements starting, for example, from observations by worldwide distributed radiosonde stations. Radiosoundings are first extracted, quality controlled, combined to auxiliary information in order to make them relevant for further use in radiative transfer applications and archived. The resulting database is ARSA: it now covers the period 1989- to now and is regularly extended to new arriving data. ARSA is distributed via the IPSL Climserv server (France).
The TOVS/Path-B climatological database of atmospheric and surface variables obtained from satellite observations (NOAA/NASA Pathfinder project)
Analysing long time series of satellite vertical sounder observations is one of the keys to the study of the variability and evolution of numerous climate variables: temperature, water vapour, cloud characteristics (cloud cover and distribution, microphysical properties), surface characteristics (emissivity, temperature), concentration and distribution of major greenhouse gases. Selected by NOAA/NASA for participating in the reanalysis Pathfinder project, in the early 1990s, in charge of reanalysing TOVS observations, the ARA team benefits from an open access to more than 20 years of observations (and more owing to the presence of HIRS on board the Metop platform). Today, the satellites NOAA-8, 10, 11, and 12 have been processed and NOAA-7, 8 and 15 are on the way. Results have been made available to DAC/GSFC (USA) and archived on Gaya/IDRIS-France) and soon on Climserv/IPSL (France).