Cloud parameter retrieval from MIPAS data
European Space Agency, (Special Publication) ESA SP (2007)
Abstract:
Clouds are a source of major uncertainty in climate models - it is thus important to accurately model clouds in order to determine their properties. In this work, three cloud parameters (cloud top height, cloud top temperature and cloud extinction coefficient) are used to model the radiance measured in the MIPAS field-of-view as they represent the most obvious physical, thermodynamic and optical properties, respectively, of a cloud. Finally, this model is implemented in an optimal estimations-type retrieval of cloud top height, temperature and extinction co-efficient from real MIPAS spectra.Combined ozone retrieval using the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Tropospheric Emission Spectrometer (TES)
European Space Agency, (Special Publication) ESA SP (2007)
Abstract:
The main advantage in combining limb and nadir geometries is that it allows the stratospheric and tropospheric ozone concentrations to be separated which makes it possible to improve the tropospheric ozone retrieval. This paper presents the retrieval method which will be used to combine TES nadir measurements with MIPAS limb measurements and shows some preliminary results. The Tropospheric Emission Spectrometer (TES) is a high-spectral-resolution infrared imaging Fourier transform spectrometer operated by NASA's Jet Propulsion Laboratory(JPL). It has a spectral range from 3.2/μm to 15.4/μm and at present is mostly operating in the nadir mode. TES routinely measures temperature and concentrations of O3,H2O, CH4, CO, HNO3, and N2O. A local optimal estimation retrieval code (the MIPAS Orbital Retrieval using Sequential Estimation (MORSE)) was used to retrieve Volume Mixing Ratios (VMR's) from the low resolution ESA level IB MIPAS data and level IB TES data. A joint retrieval was achieved by using the MIPAS retrieved VMR profiles as the a priori for the TES retrieval. A similar method could be used in the future to combine MIPAS and IASI.Global observations of ozone isotopic ratios from MIPAS limb emission spectra
European Space Agency, (Special Publication) ESA SP (2007)
Abstract:
Ozone isotope data for 50O3 and 49O 3 are retrieved from MIPAS limb emission spectra. Enrichments for 50O3 range 7 to 12% in the middle stratosphere. For 49O3 most enrichments are between 7 and 10%. In stratosphere (25-40 km) these measurements are in agreement with previous measurements (e.g. FIRS) and with expectations based on laboratory measurements. Above 40 km and below 25 km, the enrichments of both 50O3 and 49O3 get larger, from 30 to 50%. MIPAS enrichments show latitude and altitude structure.Joint retrieval of CO and vibrational temperature from MIPAS-envisat
European Space Agency, (Special Publication) ESA SP (2007)
Abstract:
MIPAS is a limb viewing fourier transform spectrometer operating in the infra-red. It scans the tangent altitude range 6-68 km at a vertical resolution of approximately 3km. CO has various natural and anthropogenic sources including forest fires and industry. In the troposphere, CO is the main sink of the principal oxidising agent - the hydroxyl radical - and so reduces its capacity for the removal of other atmospheric pollutants. In the stratosphere, its intermediate lifetime makes it useful as a tracer for stratospheric motions and processes of tropospheric-stratospheric exchange. However, the retrieval of CO from a limb sounding IR instrument is complicated because of non-LTE (non-local thermodynamic equilibrium) effects. Ordinarily, the internal vibrational energy level populations are controlled by collisions between molecules and follow the translational (kinetic) energy distribution of the ambient gas (LTE). However, if collisions are infrequent, radiative processes can lead to a non-Boltzmann distribution of the internal energy level populations (non-LTE). CO is strongly affected by non-LTE in the IR down to around 40km and modelling these processes is difficult. These effects are especially problematic in the limb viewing geometry due to the long path length viewed through the upper atmosphere. However, using a joint CO, vibrational temperature (Tv) retrieval it is possible to estimate the non-LTE effects without modelling the energy level populations. Instead, we retrieve a parameterisation of the non-LTE effects, Tv, directly from the emission spectra.MIPAS observations of stratospheric trends
European Space Agency, (Special Publication) ESA SP (2007)