Presentation on theme: "Products from the OMPS Limb Profiler (LP) instrument on the Suomi NPP Satellite Pawan K. Bhartia Earth Sciences Division- Atmospheres NASA Goddard Space."— Presentation transcript:
Products from the OMPS Limb Profiler (LP) instrument on the Suomi NPP Satellite Pawan K. Bhartia Earth Sciences Division- Atmospheres NASA Goddard Space Flight Center Greenbelt, Maryland, USA
Limb Scattering Technique Line of sight Tangent point Tangent height Diffuse upwelling radiation Solar Radiation
OMPS LP Standard Products Products from V2 O 3 Algorithm – Density vs alt profiles from cloud-top to 60 km – Converted into MR profiles using T/P profiles from GMAO at NASA/GSFC. – Also provides Aerosol Scattering Index (ASI) @ 673 nm to map aerosols, PMC, PSC and cirrus clouds. Aerosol extinction profiles are no longer produced by the O 3 algorithm. – 2 years of data planned to be released by the end of this month. Aerosols Products- produced separately – Currently under evaluation. Data should be released in 2-3 months.
Aerosol Scattering Index (ASI) ASI= ln(I m /I c ) Where I m is the measured radiance, and I c is calculated radiance assuming no aerosols scattering, both normalized at 45 km to unity to remove calibration and DUR effects, i.e., ASI is forced to be zero at 45 km. Note: This concept is conceptually similar to TOMS UVAI, except that UVAI is based on radiance ratios at two wavelengths, and UVAI is normalized to zero using a different method.
ASI at 673 nm Using SAGE aerosol climatologyFrom OMPS LP data ASI is produced by two effects: aerosol scattering & Rayleigh attenuation Rayleigh attenuation becomes important below 20 km It will be difficult to retrieve aerosol profiles from LP in the SH
Cause of Hemispherical Asymmetry in ASI Aerosol/Rayleigh scattering phase function ratio changes by a factor of 40 between 25S and 80N
Key Features of V2 O 3 algorithm Profiles between 28 and 60 km are derived using 40 wavelengths in the 290-325 nm range. – Radiances are normalized to unity at 65 km to remove (alt- ind) calibration and DUR effects. – Each wavelength is paired with 353 nm to remove errors in P/T profiles and to reduce aerosol effects. Profiles below 27 km are derived using 19 wavelengths in the 549-633 nm range. – Radiances are normalized at 45 km. – Each wavelength is combined with 510 and 637 nm into a triplet to remove linearly varying aerosol effects.
LP/MLS Comparison Summary Average of 1 day/month “golden” days on which SNPP and Aura orbits overlap
Aerosol Error in V2 O 3 Data Estimated using SAGE climatology- so it may be somewhat of an overestimate Error is caused by attenuation of Rayleigh by aerosols, not by aerosol scattering 1e-4 /km aerosol vertical extinction produces ~1% ozone error
Altitude Registration Rayleigh Scattering Attitude Sensing (RSAS) – Proposed by Bhartia in 1992, tested on Space Shuttle – Uses 350 nm radiance at 20 km normalized at 35 km, which varies by ~14%/km. – Not affected by calibration error, but affected by cloud inhomogeneity and aerosols. Currently limited to Antarctica. – Detected 1.8 km error in mounting the instrument on S/C. 290 nm/55 km method – Radiance varies by ~14%/km. – Not affected by O 3, aerosols (except PMC) or DUR but requires absolute radiometric calibration. – Requires accurate pressure profiles in the 55- 65 km range. – Results show variation of TH error along the orbit is <300 m, but further analysis is req’d.
Synergy with other sensors Limb and nadir data can be combined to produce trop O 3 column, as was done for MLS & OMI. Assimilation of limb and nadir data may provide vertically resolved trop O 3 information. – Besides OMPS, nadir sensors include CrIS, IASI, GOME-2, TropOMI, and later TEMPO, GEMS and Sentinel 4. Combination with SAGE III data (to be launched on ISS next year) should provide information about aerosol size distribution. SAGE III may help improve/validate LP altitude registration scheme.
Summary & Plans V2 O 3 profiles are of high quality but they are affected by aerosols (<10% error) in the UTLS and by PMCs in the mesosphere (in polar summer only) – V3 is planned to be released by 1/1/17, though some improvements to V2 may be released sooner. Alt registration is accurate to ~300 m – Further improvements are possible Aerosol products need improvement – Aerosol extinction profiles is best derived at ~750 nm to minimize Rayleigh effects. – Angstrom exponent information is likely to be limited to northern hemisphere only.