View
26
Download
0
Category
Tags:
Preview:
DESCRIPTION
5th ADIENT Meeting 2 nd 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). Motivation. - PowerPoint PPT Presentation
Citation preview
Rutherford Appleton Laboratory
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)
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
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
AATSR
ECMWF
Cloud Clearing
Average
Minimum
Winds/brdfMODIS
Profiles
Rad
iativ
e T
rans
fer
Mod
el(R
AL-
FM
2D)
Statistical Comparisons &Time-series analysis
Cox and Munk
GLOMAP/UKCA
Mie model
CP2OPAC/Globaer other
Speciated size distributions
Spectral ref indices
Phase function
Extinction coef
SSA
Observed radiance
Simulated radiance
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
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)
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.
ATSR and Simulated GLOMAP radiances
ATSR-GLOMAP October 2004
postive-red negative-blue
ATSR-GLOMAP May 2004
2004 monthly average comparison
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.
Recommended