1. Horizontal variability of aerosol optical properties observed during the ARCTAS airborne experiment Yohei Shinozuka 1*, Jens Redemann 1, Phil Russell 2, John Livingston 3, Tony Clarke 4, Steve Howell 4 and Jim Podolske 2 1 Bay Area Environmental Research Institute; 2 NASA Ames Research Center; 3 SRI International; 4 School of Ocean and Earth Science and Technology, University of Hawaii * Yohei.Shinozuka@nasa.gov

2. In this talk… Experiment and Objectives Results – Standard deviation of AOD – Autocorrelation of AOD, Angstrom exponent, local extinction coefficient Conclusions

3. C.S. M c Naughton Asian outflow over Alaskaforest fire smoke over Canada (April 2008) Homogeneous (June and July 2008) Heterogeneous ARCTAS

4. C.S. M c Naughton Asian outflow over Alaskaforest fire smoke over Canada (April 2008) Homogeneous (June and July 2008) Heterogeneous Objectives of this study present the statistics of measured variability discuss implications for observations and modeling ARCTAS

5. AATS-14 (sunphotometer) for AOD See Shinozuka et al. (ACPD, 2010) for an ARCTAS AOD overview. NASA P-3 Also used in this study: Nephelometers for scattering (dry and humidified) PSAP for absorption

6. 20 km Relative standard deviation (std rel ) 0.12 (std) / 0.60 (mean) * 100% = 20% (std rel ) Median std rel = 19% UTC AOD 499 Cumulative Probability std rel (%)

7. 19% forest fire smoke over Canada Horizontal variability in AOD 499 Distance (km) Median std rel (%)

8. 2% Asian outflow over Alaskaforest fire smoke over Canada 19% Distance (km) Median std rel (%) HomogeneousHeterogeneous Compare two extreme environments

9. Asian outflow over Alaskaforest fire smoke over Canada 3x3 10x10 Area (km 2 ) 3x3 10x10 Area (km 2 ) 2% 19% Distance (km) Median std rel (%)

10. Geometric Average Distance = 4.5 km

11. Asian outflow over Alaskaforest fire smoke over Canada 2% 19% 3x3 10x10 Area (km 2 ) 3x3 10x10 Area (km 2 ) Distance (km) Median std rel (%) Our statistics help estimate the impact of scale difference on AOD comparison between a grid cell (e.g., MODIS) and point (e.g., AERONET).

12. Asian outflow over Alaskaforest fire smoke over Canada 2% 19% 3x3 10x10 Area (km 2 ) 3x3 10x10 Area (km 2 ) Distance (km) Median std rel (%) 9% 1%

13. Asian outflow over Alaskaforest fire smoke over Canada 2% 19% 9% 3x3 10x10 Distance (km) Median std rel (%) 1% 1 percentage point10 percentage points Our statistics help assess the merit of reducing grid size, in satellite retrieval and transport modeling, for a given environment. Going from 10x10km 2 grid cell to 3x3km 2, variability is reduced by… Area (km 2 )

14. Autocorrelation (r) 20 km AOD 499 UTC AOD 499, start AOD 499, end start end

15. 0.37 forest fire smoke over Canada r of AOD 499 Distance (km) r

16. 0.37 0.95 Asian outflow over Alaskaforest fire smoke over Canada r of AOD 499 Distance (km) rr

17. Asian outflow over Alaskaforest fire smoke over Canada r of Angstrom Exponent Distance (km) rr

18. Asian outflow over Alaskaforest fire smoke over Canada r of Local Extinction Distance (km) rr Our statistics help optimize the locations of monitoring/validation stations.

19. Conclusions 499 nm AOD likely varies by 2% in an extremely homogeneous environment like the Alaska phase of ARCTAS, but 19% in an extremely heterogeneous environment like the Canada phase, both over a 20 km line. Also over a 10x10 km 2 square. Autocorrelation is 0.95 in the Alaska phase, 0.37 in the Canada phase. Statistics are provided for Angstrom exponent and local extinction coefficient (SSA and CO to be included). The statistics help interpretation and design of suborbital measurements, satellite remote sensing and transport modeling.

20. END OF PRESENTATION, BEGINNING OF BACKUP SLIDES

21. Asian outflow over Alaskaforest fire smoke over Canada r of Local Extinction and CO 3x3 10x10 Area (km 2 ) 3x3 10x10 Area (km 2 ) Distance (km) rr