5th ADIENT Meeting 2 nd April 2009, Manchester University

1. 5th ADIENT Meeting 2nd April 2009, Manchester University WP4.3.1 Comparisons of model simulations with global radiance measurements C. Poulsen ,R. Siddans With contributions from Dave smith(RAL), Maria Frontoso(Leeds) and Gareth Thomas(Oxford)

2. Motivation • Oxford-RAL Aerosol and Cloud (ORAC) scheme retrieves AOD, effective radius and some indication of aerosol type. • These results to be compared directly to models in ADIENT (WP4.2) • However it is important to complement this activity with radiance comparisons to test consistency between model & measurements: • Retrievals make assumptions about aerosol optical properties (and surface) which will often be inconsistent with model • “Measured” SW flux makes assumptions about angular distribution of radiation (phase fn + BRDF). • Radiance is directly measured and can be directly computed from model fields • A stringent test of understanding of the direct effect: • Aerosol distribution + Aerosol & surface optical properties + RT modelling

3. ATSR-2 & AATSR • ATSR-2 (ERS-2 1995-) and AATSR (Envisat 2002-) have produced a time-series of global data with unique characteristics to test the representation of shortwave (SW) radiation in climate models. • Dual-view observations at 0.55, 0.67, 0.87 and 1.6, 11 & 12μm are sensitive to the amount, type and size distribution of aerosol • Reflectances accurate to1% following ESA inter-calibration study

4. Phase function Extinction coef Mie model SSA Average Cloud Clearing AATSR Minimum Winds/brdf MODIS Cox and Munk ECMWF Observed radiance Profiles Radiative Transfer Model (RAL-FM2D) Statistical Comparisons & Time-series analysis Simulated radiance GLOMAP/UKCA Speciated size distributions CP2 OPAC/Globaer other Spectral ref indices

5. GLOMAP wish list • AOD at 0.55 µm (0.87 and 0.67 if at all possible) • Aerosol type • Aerosol size (either size distributions or effective radius) • Surface reflectance/BRDF, if it exists! • The height distribution of the aerosol • Single scattering albedo • Phase function • Extinction coefficient

6. GLOMAP wish list • AOD at 0.55 µm (0.87 and 0.67 if at all possible) • Aerosol type • Aerosol size (either size distributions or effective radius) • Surface reflectance/BRDF (only if it exists!) • The height distribution • Single scattering albedo (profile) of the aerosol • Phase function – only asymmetry available ? • Extinction coefficient (profile)

7. Comparison so far • GLOMAP and ATSR cloud cleared radiances regridded to 5 degree over Europe • Only coincident radiances compared • GLOMAP information on radius(profile) number concentration and aerosol optical depth used to simulate ATSR radiances. • GLOBAER optical properties-Maritime Clean used • ATSR and GLOMAP compared-currently only over sea.

8. ATSR and Simulated GLOMAP radiances

9. ATSR-GLOMAP October 2004 postive-red negative-blue

10. ATSR-GLOMAP May 2004

11. 2004 monthly average comparison

12. Conclusions & Next steps • Initial analysis indicates AATSR radiances underestimated by GLOMAP + RT model • However this based on simplified use of GLOMAP AOD + size. • Next, obtain global data and perform runs • With GLOMAP optical properties • With CP2 (ideally) or GlobAerosol optical properties • Perform analysis for ATSR forward and nadir view • Analyse results as function of region.