Multi-Mission Validation by Radio Occultation: System Setup and Initial Results on GOMOS and MIPAS Validation
Stefan Koerner(1), Gottfried Kirchengast(1), Johannes Fritzer(1), Christian Retscher(2,3) and Thorsten Fehr(4)
(1) University of Graz, Leechgasse 25, A-8010 Graz, Austria
(2) NASA/GSFC, Code 613.3, Greenbelt, MD 20771, United States
(3) UMBC, 1000 Hilltop Circle, Baltimore, MD 21250, United States
(4) ESA/ESRIN, Via Galileo Galilei, I-00044 Frascati, Italy
In the ESA/ESRIN atmospheric Cal/Val context a project of the Wegener Center prepares and provides long-term radio occultation (RO) reference data, which will be used in the long-loop monitoring of trends related to both spaceborne instrument and climate system variability, routine validation of atmospheric satellite products, validation of geophysical retrieval algorithms, bridging between temporally separated space missions, as well as scientific evaluation of atmospheric processes. The project ensures the provision of correlative RO measurements suitable for in-depth examination of tropospheric and stratospheric fundamental state profiles, such as of temperature and pressure as function of MSL altitude, from (ESA) satellite observations.
This undertaking is highly worthwhile since the unique combination of global coverage, high accuracy, long-term stability, and all-weather capability makes the validation with RO measurements preferable to other methods. The currently available RO receiver constellation provides a combined total of up to about 2500 profiles per day. With the further extension of the Global Navigation Satellite System (GNSS), e.g., by the upcoming Galileo system, this number will further increase.
The correlative RO data are co-located with comparable ESA mission datasets, initially focusing on the Envisat atmospheric instruments MIPAS and GOMOS, as well as ground-based validation sites defined in the Multi-TASTE and VALID projects related to Envisat. The correlative data will be provided to a Cal/Val repository of ESA (currently at NILU, Kjeller, Norway), which will furnish the Cal/Val and science community direct access to these data. Datasets from MIPAS and GOMOS are validated against the correlative RO data in order to derive estimates of the systematic and random errors and their changes with time.
The presentation will introduce the project on multi-mission validation by RO along the lines above and describe the system setup as far as it is developed up to now. It will then focus to discuss initial results for a “testbed month” of validation of temperature, pressure, and density profiles over the upper troposphere and lower stratosphere (UTLS) from Envisat GOMOS and MIPAS against co-located RO data from CHAMP and Formosat-3/COSMIC. Alongside, the general utility of consistent RO long-term databases in long-loop calibration and validation strategies of other atmospheric (physics and chemistry) instruments will be addressed.