Simulation of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) using GLOMAP
The study focuses on validating models by comparing them with CALIOP data, aiming to improve predictions on aerosol properties and radiative effects. The research involves investigating aerosol production modules and radiation impacts, utilizing CALIOP's extensive aerosol dataset. Alternative approaches for model validation are discussed, emphasizing the comparison of modeled and retrieved extinction profiles. The goal is to enhance the performance of the model in predicting aerosol characteristics and their effects accurately.
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SIMULATION OF CLOUD-AEROSOL LIDAR WITH ORTHOGONAL POLARIZATION (CALIOP) ATTENUATED BACKSCATTER PROFILES USING THE GLOBAL MODEL OF AEROSOL PROCESSES (GLOMAP) Stuart Young1*, Martin Cope1, Sunhee Lee1, Kathryn Emmerson1, Matthew Woodhouse1, Nicolas Bellouin2 * stuart.young@csiro.au 1CSIRO OCEANS & ATMOSPHERE FLAGSHIP , ASPENDALE, AUSTRALIA , 2 DEPT OF METEOROLOGY, UNI. OF READING, UK 27th International Laser Radar Conference, New York, 6 July 2015
Aims CSIRO CTM used for forecasting air quality, and radiative effects of dust storms and (n & a) biomass burning, as well as the health impacts of these emissions. AOD often underestimated c.f. AERONET (seasonal dependence, unknown causes) Soil moisture, aerosol optical properties, presence of advected Free Tropos. aerosols etc? Our aim, therefore, is to develop means for testing the both the aerosol production modules and the radiation module of our CTM. Unravelling the contributions of FT and BL aerosols, and correctly assessing the radiative effects of aerosol layers, requires that the model correctly predict their location, their loading and their optical properties. We need, therefore, to be able to test the performance of the model by comparing with real data at each height in the model s grid. As CALIOP / CALIPSO has produced an excellent global, height-resolved data set on aerosols over last 9 years, we aim to compare our model with CALIOP. 2 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods Alternative Approaches # 1 1. Comparison of Modelled and Retrieved Extinction Profiles. For retrievals unconstrained by estimates of layer AOD, as in most surface-attached layers considered in the model, accurate extinction retrieval from CALIPSO Level-1 data requires accurate calibration of the attenuated backscatter profiles, reliable detection of features , and of their full vertical and horizontal extents, reliable discrimination between cloud and aerosol features, reliable determination of aerosol type for selection of SA, often under conditions of low SNR, that the modelled SA for aerosol type accurately represent the actual SA in the feature being studied (but natural variation exists for any aerosol type). These factors can sometimes lead to large uncertainties in the unconstr. CALIOP extinction products. Also effectively comparing one model (CTM radn.) with another model (CALIOP aerosol). Disparities between modelled and retrieved extinction profiles could result from problems on either side of the comparison Could -> adjustment of perfectly good model result to agree with an inaccurate retrieval. 3 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods Alternative Approaches # 2 2. Comparison of Modelled and Measured Attenuated Backscatter (ABS) Profiles. Attenuated Backscatter is simply the raw, calibrated lidar profile * R2 Therefore, errors in the measured profiles are minimal. Our model (CTM + GLOMAP + RADAER) has all the information (molecular density, RH, O3; aerosol types and loading, hydration and optical properties) needed to simulate an Attenuated Backscatter profile. This approach has several advantages keeps all of the uncertainties on model side of comparison (-> red. ambiguity), allows adjustment of aspects of model to test their sensitivities and determine what are the causes of any disparity, allows us to test ability of model to simulate the right amount of right type of aerosol with the right optical properties in the right place at the right time. 4 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods The Models insoluble soluble coarse coarse A continental- scale, coupled, atmos. transport system CCAM insoluble soluble accum accum vertical levels (0.02 8 km) z = 0.02 2 km insoluble Aitken soluble Aitken Secondary Organic Aerosols ISORROPIA II VBS (ACCESS-UKCA-mode) = 0.5 degrees VBS sulfate, sea salt, organic carbon, elemental carbon, dust Nucl Number & Mass Concentrations + Optical properties (bsc, ext, abs) from RADAER 5 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods The CALIOP Signal Simulator 1. Aerosol (only) and meteorological profile data extracted from model outputs at each grid point intersected by CALIPSO track. CALIOP profiles simulated from satellite altitude, ZS, to surface: Attenuated (Total) Backscatter: ?? 2. ? = ?? ? + ?? ? ?? 2 ??,? ?? 2 ??,? , ? ? whereand ?? 2 ??,? = exp 2[?? 2 ??,? = exp 2 ?? ? + ??3 ? ]?? ? ?? ?? ?? ?? This is divided by Attenuated Molecular Backscatter to give the Attenuated Scattering Ratio ? = ?? ? ?? 2 ??,? , ?? 2 ??,? . ? ? =1 + ?? ? / ?? ? ?? 6 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods CALIOP Data and Processing 1. We use CALIPSO / CALIOP Level-1, version 3, data files for the Attenuated Backscatter comparisons with the simulations. Meteorological data (from GEOS-5) in Level-1 files are used to create the measured Attenuated Scattering Ratio profiles. Individual single-shot profiles are filtered to remove cloud-affected regions below the tops of clouds identified in the CALIPSO Level-2 version 3 VFMs. The filtered ABS profiles are averaged along-track to give similar horizontal resolution (0.5 degrees) to that of model. As vertical resolution of model varies significantly with height, CALIPSO profiles are not smoothed vertically but left at native resolution. (dZ =30 m over the vertical extent of the model (surface to 8 km).) 2. 3. 4. 5. 7 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Results Example of ABS Comparisons -16.4 degrees -20.2 degrees -10.6 degrees 9 9 9 (a) 8 8 8 7 7 7 6 6 Altitude (km) 6 Altitude (km) Altitude (km) Left (a) CALIOP (b) Simulation (c) CALIOP VFM 5 5 5 4 4 4 3 3 3 2 2 2 1 1 1 (b) 0 1.0E-02 0 1.0E-02 0 1.0E-02 -25.2 degrees -29.8 degrees -37.2 degrees 1.0E-04 1.0E-03 1.0E-04 1.0E-03 1.0E-04 1.0E-03 Atten. Backscatter (/km/sr) Atten. Backscatter (/km/sr) Atten. Backscatter (/km/sr) 9 9 9 Right ABS profiles red = CALIOP blue = model 8 8 8 7 7 7 6 6 6 Altitude (km) Altitude (km) Altitude (km) 5 5 5 4 4 4 (c) 3 3 3 2 2 2 1 1 1 0 1.0E-02 0 1.0E-02 0 1.0E-02 1.0E-04 1.0E-03 1.0E-04 1.0E-03 1.0E-04 1.0E-03 Atten. Backscatter (/km/sr) Atten. Backscatter (/km/sr) Atten. Backscatter (/km/sr) 8 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Results Additional Variables 55 sr 20 sr 20 sr 40 sr Relative Humidity (%) 532-nm Lidar Ratio (sr) 1064/532 Atten. Colour Ratio 9 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Results Possible Explanations for Errors 1. Errors in Emissions Modelled soil moisture may be inaccurate -> incorrect dust generation Smoke emission inventories (based on fire scars and IR hotspots ) may be inaccurate -> incorrect smoke generation Errors in environmental distributions affecting aerosols and their optics. Cloud fields, incorrect modelled RH profiles -> different particle size, RI, p and p Errors in Aerosol Properties Aerosol growth factors may be incorrect Mie theory may not describe dust scattering accurately enough Errors in Aerosol Lifetimes Horiz. (Boundary condns, ext. advection) and Vert. Transport (e.g. sinks & precip.) 2. 3. 4. 10 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Conclusions and Next Steps 1. 2. GLOMAP RADAER successfully integrated into CTM. Comparison of simulated ABS profiles with CALIOP data while varying model parameters is a very powerful tool for identifying model deficiencies. advantage of having all significant uncertainties on the side of the model. Initial model results are encouraging but some consistent differences exist. Next Steps 1. Compare ABS profiles computed using Mie LUT with full Mie code and size distributions. 2. Compare ABS profiles computed using Mie LUT with more sophisticated scattering models (e.g. T-Matrix code and different particle shapes). Further Questions: stuart.young@csiro.au, martin.cope@csiro.au 3. 11 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Thank you Earth Systems Assessment Program Air Quality Team Stuart Young Principal Research Scientist t +61 3 9239 4589 e stuart.young@csiro.au w www.ciro.au/en/Research/OandA OCEANS AND ATMOSPHERE FLAGSHIP
Mie Look-up Table Details One LUT for each Mode Type: 1. Aitken 2. Accumulation 3. Coarse Each LUT (51,51,51) contains 1. UKCA_ABSORPTION(X,Re,Im) 2. UKCA_SCATTERING(X,Re,Im) 3. UKCA_ASYMMETRY(X,Re,Im) 4. UKCA_BACKSCATTER(X,Re,Im) 5. VOLUME_FRACTION(X) 13 | Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods The Models # 1 Our model is a continental-scale, coupled, atmospheric transport system comprising: 1. The CSIRO Conformal-Cubic Atmospheric Model (CCAM) for simulating weather. 2. a population-based anthropogenic emission inventory with natural primary emission sources (e.g. sea salt, wind-blown dust, plus biogenic and fire emissions) and 3. a Chemical Transport Model (CTM) for simulating the atmospheric chemical transport and subsequent fate, via wet and dry deposition, of gaseous and particulate species. It has a comprehensive chemistry incorporating the Carbon Bond 5 mechanism [Sarwar, G., et al., 2008], the Volatility Basis Set approach [Donahue, N., et al., 2006] for secondary organic aerosols, the ISORROPIA-II model [Fountoukis, C., and A. Nenes, 2007] for secondary inorganic aerosol modelling. 14 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
Methods The Models # 2 The Chemical Transport Model (CTM): 1. is coupled with the GLObal Model of Aerosol Processes (GLOMAP- Mann, G. et al., 2010) a comprehensive, size-resolving global aerosol model Uses 7 modes (nu,sA,sa,sc,iA,ia,ic) and 5 components (SO4,BC,OC,NaCl,Du) 2. Boundary and initial conditions obtained from ACCESS1-UKCA2-mode (a global chemistry and aerosol model with GLOMAP). 3. CTM-GLOMAP domain for Australian continent has 0.5 resolution. 4. 19 levels (0.02 km 8 km) (dz = 0.02 km near surface to 2 km at top). 5. Aerosol Optical properties (e.g. backscatter & extinction) calculated at each model grid by RADAER module (Bellouin, 2011) via Mie look-up table for particle size and refractive index. 1ACCESS =Australian Climate Community Earth System Simulator, 2UKCA = UK Chemistry and Aerosol Model 15 Simulation of CALIOP Attenuated Backscatter Profiles using GLOMAP S A Young et al. 27th International Laser Radar Conference , New York 6 July 2015
