CAVIAR – Continuum Absorption by Visible and Infrared Radiation and its Atmospheric Relevance

1. CAVIAR – Continuum Absorption by Visible and Infrared Radiation and its Atmospheric Relevance How on schedule are we? Keith Shine Department of Meteorology, University of Reading September 2009

2. Reminder of Overall Schedule • Formal start of CAVIAR: 1 October 2006 • Original end date: 30 September 2010 • New end date: 30 June 2011 • Most CAVIAR PDRA’s and PhD’s will finish in late 2010/early 2011 • Final report due: 29 September 2011 • We are now roughly at month 36 (“frame of reference” depends on when students and PDRAs started)

3. Reminder of structure 1 Rough Guide: Green: On original schedule Amber: Somewhat behind original schedule Red: Limited activity so far possible existing continuum models existing spectral line databases dimer model development Instrument upgrades and calibration line-by-line radiative transfer models targeted lab measurements dimer model refinement field campaigns refinement of line database synthesis new continuum model impact on understanding of atmospheric processes, incl climate and remote sensing preparation of continuum model for community use

4. Reminder of Structure 2

5. Reminder of original schedule We are hear(ish)!

6. Status • Excellent progress so far in all areas • However, we need to be aware that vital parts of the project [synthesis, impacts (i.e. the AR in CAVIAR) and the provision of code for wider use] depend on earlier packages being more or less on time • Following slides show extracts from the original proposal

7. Where we should be – WP1 • Months 23-30: Use statistical mechanics methods to predict temperature dependent dimer concentrations in the atmosphere. • Months 30-40: Generate temperature dependent dimer spectrum throughout infrared. • Months 36-48: Use calculated spectrum to simulate dimer contribution to water continuum for different atmospheric conditions and input to WP4 and WP6.

8. Where we should be – WP2 • WP2.1 (RAL) The measurements will be performed over a two year period in months 4-5, 9-10, 14-15 and 19-20. Each measurement phase will be preceded by detailed planning phases and followed by periods of data reduction, comparison with existing databases and delivery of the data to the Consortium and the NERC British Atmospheric Data Centre Months 10-27: • WP2.2 (Camb/Leic) Months 10-27: The major experimental effort with the spectrometers alternating between the two laboratories. The later months are assigned to synthesis of the results (WP4), writing papers and further short periods of experimentation to investigate issues raised by the other areas of the consortium’s work.

9. Where we should be – WP3 • Months 37-41: Analysis of data from Campaign 2, and continuing analysis from Campaign 1

10. Where we should be – WP4 • Months 34-48: Data comparisons and line-by-line radiative transfer model simulations and will involve all groups. It is likely that part of the synthesis process will lead to suggestions and ideas for the focus of any remaining field, laboratory and theory work.

11. Where we should be – WP5 • Months 25-48: The main phase of this work package will occur during the final two years, as the new continuum begins to be defined. Questions to be addressed will be: • The impact of the new continuum on the climatological mean radiation budget and diabatic heating rates, both globally and as a function of latitude and season. One output of this work will be to update the well-known Kiehl and Trenberth (1997) summary of the global energy budget. • The impact of the new continuum on calculations of the variability of the radiation budget, in response to natural variability in atmospheric water vapour content. • The impact of the new continuum on the strength of the positive water vapour feedbacks, and hence the consequences for climate change. This will be examined in a diagnostic sense, by examining the response to imposed changes in temperature and humidity, and via interaction with the Met Office, its impact on climate and climate change in the Unified Model.

12. Where we should be – WP6 • Months 25-36: Preparatory phase, in which the structure of the web site would be established and documentation on the methods used to derive the new continuum would be collected together. • Months 37-48: Main phase: the exact form of the continuum will be decided as part of the WP4 synthesis. Well-documented FORTRAN codes will be developed at Reading and “beta-tested” by other members of the consortium; test case of the impact of the continuum on optical depths, heating rates and fluxes will be prepared to allow users to ensure correct implementation of the continuum model.

13. Conclusions • CAVIAR is in generally good shape and any delays are with good cause • But we need to ensure that by the time of the December 2009 Annual Meeting we are in a position to spend much of the final year on WP4, WP5 and WP6