1. Preliminary Documentation for: Earth Surface and Atmospheric Reflectivity ESDR Since 1979 from Multiple Satellites (TOMS, SBUV, SBUV-2, OMI, SeaWiFS, NPP, and NPOESS) Note: The reflectivity data shown in the files now have the correction for time of day. However, the reflectivity data still need additional correction for radiometric calibration. As such, they must not be used for publication, but are for review comment only. Jay.R.Herman@nasa.gov

2. Earth Surface and Atmospheric Reflectivity ESDR Since 1979 from Multiple Satellites (TOMS, SBUV, SBUV-2, OMI, SeaWiFS, NPP, and NPOESS) Jose Rodriguez Jay Herman Jianping Mao Liang-Kang Huang Steven Lloyd Wenhan Qin Gordon Labow David Larko Matthew DeLand Purpose: The production of a continuous ultraviolet reflectivity data record for the surface of the Earth and its atmosphere using multiple satellite data records since 1979.

3. UV reflectivity derived from TOMS measured radiances. The background color map is from MODIS visible wavelengths. In the UV, the background would be dark with reflectivity from 4 to 10 RU (1 RU = 1%). A Sample of UV Reflectivity Derived From TOMS The UV reflectivity resembles cloud images, but is also a measure of the energy reflected back to space

4. Zonal Average Reflectivity Values Reflectivity vs Latitude

5. Why are We Interested in a UV Climate Quality Reflectivity Data Set? UV takes advantage of the fact that the earth is dark compared to visible wavelengths, so that clouds and aerosols stand out. Determine the local and global amounts of solar radiation reaching the Earth’s surface for clear and cloudy conditions. Estimate the long-term changes in radiation reaching the ground and the fraction reflected back to space The long-term changes are used for climate studies in estimating changes in the energy balance in the atmosphere Radiation affecting plant productivity, Incidence of skin cancer and eye cataracts Health changes due to vitamin-D production Materials damage

6. What is Lambert Equivalent Reflectivity? The Lambert Equivalent Reflectivity is the reflectivity derived to match a measured outgoing radiance at an angle q above the reflecting surface assumed to be a Lambert Reflector. A Lambert Reflector is one where the reflection as a function of angle follows a cosine law. That is, the amount of radiance leaving the reflector is proportional to the cosine( q ), so that it looks equally bright from all directions q For an atmosphere above a reflecting surface, the amount of radiance reaching a satellite above the atmosphere is given by a formal solution to the radiative transfer equation where R is the Lambert Equivalent Reflectivity (LER) of the entire scene in the Field of View.

7. What is Lambert Equivalent Reflectivity? Ω = ozone amount from shorter wavelengths (e.g., 317 nm) Θ = viewing geometry (solar zenith angle, satellite look angle, azimuth angle) R = LER at P O P O = reflecting surface pressure S b = fraction scattered back to P O from the atmosphere I d = sum of direct and diffuse irradiance reaching P O f = fraction of radiation reflected from P O reaching the satellite I dO = radiance scattered back from the atmosphere for R=0 and P=P O The Lambert Equivalent Reflectivity (LER) is calculated by requiring that the measured radiance I SM match the calculated radiance I S at the observing position of the satellite by solving for the free parameter R

8. 1979 - 1992Nimbus- 7/TOMS 340 nm daily reflectivity is produced using in-flight calibration. Full global coverage every day. Only a few missing days in 14 years. 1985-presentSBUV-2 Series340 nm daily reflectivity is produced using in-flight calibration. 14 nadir viewing orbits per day. Full global coverage once per week. Only a few missing days. However, orbit drift can impact coverage and data quality. 1996 - 2006Earth- Probe/TOMS NOT USED 331 nm daily reflectivity is produced as part of standard processing using in-flight calibration. 340 nm is not available. Full global coverage every day. Only a few missing days in 9 years. The calibration lost precision after 2001. 1997 - present SeaWiFS412 nm reflectivity has been produced using the TOMS production algorithm and in-flight SeaWiFS calibration. The precision is very high. The 412 nm reflectivity must be converted to 340 nm reflectivity using the high spectral resolution information from OMI (270 – 500 nm). 2004 - present OMI 340 nm daily reflectivity is produced using in-flight calibration. Full global coverage every day. Reflectivity values are available from 330 nm to 500 nm. We will use 340 nm to match SBUV-2 This data can be used to relate SeaWiFS at 412 nm to TOMS, OMI, and SBUV-2 at 340 nm. Currently Available Reflectivity Data Sets

9. Is there a continuous data record available? Not Used

10. Satellites Used for Combined Reflectivity Data Set 1 TOMS/SBUV 1979 – 1992 Two Instruments 340nm 2 SBUV-2 Series (see Chart) Six Instruments 340 nm 3 SeaWifs 1997 to Present One Instrument 412 nm 4 OMI 2004 to presentOne Instrument 270 – 500 nm Problems:  We need a common calibration as a function of latitude and time of day  SeaWiFs measures at 412±10 nm instead of 340±1.1 nm  OMI is a spectrometer 270 – 500 nm, which can be used to relate 340 nm reflectivity to 412 nm reflectivity. Can we Find a Common Calibration?

11. Uncorrected for Time of DayCorrected for Time of Day

12. Uncorrected for Time of DayCorrected for Time of Day

13. Future Work: Use Nimbus7-SBUV to Correct the TOMS Calibration Note that N7-SBUV BLUE Agrees with N-9Sa RED Nimbus7-TOMS has a known calibration problem that affects the instrument on a daily basis when it emerges from the cold and darkness over the South Polar region

14. Gordon Labow Time of Day Correction Gordon Labow

15. Terminator Time of Day for Each Satellite

16. Average Correction

17. Average Correction

18. Average Correction vs Latitude and Time of Day

20. Conclusion: Correcting for the time of the day (noon normalization) that the satellites made their observations is essential if a long-term time series of reflectivity is to be used for UV irradiance or climate change studies.

21. SeaWiFs and OMI Reflectivities SeaWiFs is an ideal satellite instrument data set to add to the UV reflectivities formed from the TOMS and SBUV-2 measured 340 nm LER However, there are two problems: 1.SeaWiFs measures at 412 nm instead of at 340 nm 2.The SeaWiFs measurements are from a wide filter 412±10 nm compare to the narrow bandpass 340±1.1 nm However, the OMI spectrometer 280 – 500 nm in steps of 0.4 nm can be used to simulate the SeaWiFs reflectivities and derive the conversion from 412±10 nm to 340±1.1 nm. There is an additional problem in that OMI has two focal planes of interest: 1) Visible (350-500 nm) and 2) UV2 (306 – 380 nm). The focal planes have a small offset from each other.

22. Real SeaWiFS (10nm FWHM) 412nm (SW filter) VIS (350-500nm) UV2 (306-380nm) 352nm 360nm (SBUV filter) 352nm (SBUV filter) 340nm (SUBV filter) Real SBUV (1.1nm FWHM) 0.7RU 1.0RU (.6-1.6) 3.0RU (0.1-3.1) 0.7RU (0.2-0.9) 1.0RU ? ? ? LER Diff [352±1.1nm (UV2) – 412±10nm (VIS)] 1.3RU in equ. to 5.3RU in high lats Current path Alternative path 2006 result Convert SeaWiFs 412±10 nm Reflectivities To SBUV-2 340±1.1 nm Reflectivities Using OMI Data Work in Progress Ongoing and Future Work

23. 0.1-3.1RU, varies with latitude, surface type, and LER itself ~0.7RU, does not change much with latitude (except at 60 O S), surface type, LER & SZA 0.6 - 1.6RU, strong latitude dependence 360±1.1 nm UV2 to 352±1.1 nm UV2 360±1.1 nm VIS To 360±1.1 nm UV2 412±10 nm VIS to 360±1.1 nm VIS

24. Instrument Calibration Issues Nimbus-7 SBUV data have an error (hysteresis) up to 8% (time- dependent, SZA-dependent) in Southern Hemisphere as the satellite emerges from night. Current correction function appears to be insufficient in early years. Nimbus-7 TOMS data do not include the hysteresis correction at this time. This is our next task. NOAA-9 SBUV2 long-term characterization includes large extrapolation for time-dependent solar diffuser changes. We are now reviewing the accuracy of the solar calibration. Revisit SSBUV (Shuttle SBUV) coincidence analysis used for absolute calibration adjustment of NOAA-9, NOAA-11, NOAA-14 SBUV2. NOAA-9 SBUV2 non-linearity correction may have errors at 1-2% level. Implement better correction for NOAA-9 SBUV/2 grating drive errors to improve data quality in 1993-1997.

25. Our plan is to put the resulting reflectivity combined ASCII data sets on the TOMS web site (http://toms.gsfc.nasa.gov) and on the replacement web site for the TOMS web site (http://macuv.gsfc.nasa.gov) in addition to the general GSFC data repository (HDF).http://toms.gsfc.nasa.govhttp://macuv.gsfc.nasa.gov Thirty-one years of 5 O zonal average data (60 O S to 60 O N) are less than 100 MB Weekly average gridded files for 31 years worth of data (3 O X 5 O, 1979 to 2009) would be about 3 gigabytes. Map files tend to be quite small (on the order of 25 kilobytes for a normal-sized PNG image). Thus, one "set" of images would be about 300 megabytes for 31 years of daily images. We would like to release the first version of the reflectivity data set along with this presentation and additional documentation for limited peer review. Initial Data Plan