Applications and Data Assimilation 2

Tropospheric ozone has the third highest radiative forcing (RF) for anthropogenic greenhouse gases since pre-industrial times, but high uncertainties and a large spread in model values remain in the IPCC AR5. These uncertainties, along with  recent studies comparing climate models and satellite observations of tropospheric ozone provide motivation to benchmark the model-to-satellite differences in TOA ozone band flux and flux sensitivity. The TOA flux for the 9.6 micron ozone band is a fundamental quantity which is predicted by IPCC chemistry-climate models but has never been tested directly against satellite measurements. We also compute the sensitivity of TOA (top of atmosphere) flux to the vertical distribution of ozone, or Instantaneous Radiative Kernel (IRK), for both the Aura-TES and MetOP-IASI instrument. The IRK explicitly accounts for more dominant radiative processes such as clouds and water vapor due to the spectrally resolved absorption features and allows attribution of changes in ozone RF to vertical changes in ozone and ozone precursor emissions. The continuation of the TES record of infrared ozone spectra, TOA flux and IRKs with long-term IASI data will allow accurate predictions of future ozone forcing and an assessment of the feedback from changes in the hydrological cycle on ozone RF. Here we present initial comparisons of satellite observed TOA ozone band fluxes and IRKs with RRTMG (Rapid Radiative Transfer Model-GCM applications) in the NCAR CAM-chem chemistry/climate model and with the GISS radiative transfer model.

For the past thirteen years the Canadian built OSIRIS instrument onboard the Swedish led Odin satellite has been collecting measurements of spectrally dispersed limb scattered sunlight and using these to retrieve information on the composition of the Earth’s atmosphere in the altitude range from 7 km to 60 km. In particular OSIRIS measurements have been used to retrieve vertical profiles of the ozone and nitrogen dioxide number density and vertical profiles of the stratospheric aerosol extinction. Also, over the past decade OSIRIS measurements have been extremely useful in identifying the impact of volcanic eruptions on not only the stratosphere but on the atmosphere near the surface of the earth.

Recently Canada has begun studying the concept of a follow-on mission to the highly successful OSIRIS. This new mission, microCATS, will involve a modified versions of OSIRIS alone on a dedicated Canadian built micro-satellite platform. The modified OSIRIS has been named the Canadian Atmospheric Tomography System (CATS) and will make similar measurements to OSIRIS but with greater precision and higher spatial resolution, especially within the UTLS region.

This presentation will: describe the Odin instrumentation; discuss recent work on the OSIRIS data records that indicate both the nitrogen dioxide and ozone measured from Odin can be used for air quality analysis; introduce the CATS instrument; and discuss the potential of the microCATS measurements for air quality analysis and forecasting should these measurements be made available in near real time. 

During the discussion, seed questions proposed by the chairs will be discussed with the audience.