Outline: 1. Atmospheric Regimes: Scientific Questions & Observational Needs

1. FacilityStrategic Plan: Chemistry Perspective Outline: 1. Atmospheric Regimes: Scientific Questions & Observational Needs UT/LS (HOx, water ) Middle & Lower Troposphere (clouds, aerosols, NOx, regional vs global) Surface (land, ocean) 2. ATD contributions

2. Scientific Questions & Observational Needs Upper Troposphere/Lower Stratosphere (few km above & below local tropopause, ~ 7 – 18 km)

3. Radical Chemistry in the Upper Troposphere/Lower Stratosphere: A Summary of Current Scientific Issues and a Proposed Observational Study Alan Fried, Chris Cantrell, John Orlando, Brian Ridley, Mary Barth, and Ian Faloona Science Documents http://www.acd.ucar.edu/UTLS/index.htm

4. NCAR UTLS White Paper Integrated Study of Dynamics, Chemistry, Clouds and Radiation of the Upper Troposphere and Lower Stratosphere Laura Pan, Brian Ridley, Bill Randel, Andrew Gettelman, Andy Heymsfield, Mary Barth, Alan Fried, Chris Cantrell, Todd Lane, Don Lenschow, Steve Massie, Owen Cooper, Alyn Lambert, Mike Coffey, Sue Schauffler, Paul Wennberg, Guy Brasseur Science Documents http://www.acd.ucar.edu/UTLS/index.htm

5. Upper Troposphere/Lower Stratosphere • Important to identify & understand: the various UT/LS processes that control water vapor, ozone, radicals, aerosols, and clouds. This is critical for predictions of climate change & trends in global air quality. (strat. water, ozone, and carbon dioxide exert major influence on radiative forcing). • The UT/LS is an under-sampled region: The altitude range is often below the detection range of the spaceborne instruments and there are only a few high altitude airborne observing platforms.Ideal for HIAPER

6. O3 Chemistry in the UT/LS Production (O3) – Loss (O3) Term 1 Term2 Term3 Term4 k1[NO][HO2] – {k4[O(1D)][H2O] + k6[HO2][O3]+ k5[OH][O3] } • Term1 accounts for ~ 80% of O3 Production • Net O3 depends upon HOx (OH + HO2) • Net O3 depends upon NOx (NO + NO2) • Net O3 depends upon O3 photolysis which produces O(1D) • Net O3 depends upon H2O (i.e., H2O is a reactant and not just a climatic gas) • Net O3 depends upon peroxides, and OVOC which produce HOx when photolyzed • In UT get O3 production with increasing HOx (Term 1) • In LS get O3 destruction with increasing HOx (Terms 3 & 4) • In UT/LS get admixture (3 regimes provides good testing of models)

7. Measurement-Model HOx Comparisons • Growing body of evidence of persistent missing HOx sources in the UT/LS • Photolysis of additional HOx precursors such as CH2O, H2O2, and CH3OOH, transported from lower altitudes and/or produced in situ from ???? are important in the UT/LS

8. Additional Sources of HOx in the UT/LS From Wennberg et al., Science, Vol. 279, 49-53, 1998.

9. Major Questions • What are the key radical production and destruction rates and their contrast in the UT and LS? • Can we reconcile HOx meas-model discrepancies simply with discrepancies in HOx precursors? • Are there temporal and geographic dependencies to these discrepancies?

10. Major Questions (Cont.) • Can we reconcile HOx & precursor meas-model discrepancies in air masses affected by: • Convection • Cirrus clouds • At high solar zenith angles • At high NOx levels • What are the concentrations of NOx and reservoir species in the above affected air masses?

11. Major Questions (Cont.) • How is the budget of O3 in the UT impacted by chemical processes? • What are the regional and global effects of these chemical processes on tropospheric ozone?

12. Major Questions Regarding UT/LS H2O • Stratospheric H2O increasing ~ 1%/year over past 45 years; ~ 50% of increase due to increases in strat. CH4 while other 50% highly uncertain. • While general overall agreement amongst various water-vapor measurements, there are still unexplained differences.

13. Observational Needs Need a dedicated radical study on HIAPER Need instruments to measure (significant instr. dev for autonomous operation) • OH, HO2, RO2 (ACD or PSU) • NO, NO2, NOy, O3 (ACD/ATD) • H2O, cloud water content, aerosol surface area density (ATD) • CO & NMHCs (ATD/ACD)

14. Observational Needs (Cont.) • J-values (ACD) • CH2O (ATD/ACD) • MHP, H2O2 (????) • Acetone, Ethanol, Methanol, C2 – C5 Carbonyls (ACD)

15. Observational Needs H2O • Need systematic, sustained, well designed long- term effort to compare instruments in both the laboratory and the field • Need systematic, sustained effort to ensure continuity of measurements and their validity over time for long-term measurements. • Need simultaneous measurements of CH4 and other precursors of H2O (OVOCs) in strat.

16. Potential Avenues for ATDInvolvement • ATD/ACD led HOx studies in partnership with university and gov. colleagues. • Partnership with ACD and/or universities in selective inst. dev. (our involvement UC/SB for meas. of HCl one example). • HIAPER technology transfer of new instr. to and from ATD (ex., sustained operations of research instruments from MRE proposals)

17. Potential Avenues for ATDInvolvement • ATD design, engineering, electronic, and data acquisition/processing support of HIAPER instruments (both “research” and “routine”) • ATD should play a larger role in H2O UT/LS vapor measurements, and perhaps establish its role as a “standard” for H2O measurements.

18. Middle & Lower TroposphereScientific Questions & Observational Needs • Large uncertainties in exchange of chemicals (O3, HCs, NOx, HOx) and aerosols between continents and the global troposphere. Need more observations on a variety of platforms. • How much of the carbon from natural carbon emissions (isoprene and terpenes) can we account for in the observations? Need a carbon cycle budget experiment. • Large uncertainties still for the total production of reactive nitrogen by lightning and its distribution with altitude. Need more observations.

19. Middle & Lower Troposphere Scientific Questions & Observational Needs (Cont.) • In the remote troposphere, partitioning between NOx and its principal reservoir (HNO3) is poorly understood (model NOx/HNO3 << meas., suggesting unknown reactions that convert HNO3 back to NOx. Need more observations with complete suite of measurements. • Large uncertainties in processing of soluble gases in clouds and on marine aerosol haze. Need more observations of soluble gases (fast meas sec.) with comprehensive aerosol meas.

20. Middle & Lower Troposphere Scientific Questions & Observational Needs (Cont.) • Large uncertainties in separating out the uptake component from elevated levels from the vertical transport of pollution in and around clouds. Need more observations vs altitude. • Need to develop robust chemical signatures to identify the effects of past clouds.Could explain unusual “clear-air” observations.

21. Surface (Land & Oceans) Scientific Questions & Observational Needs • Large uncertainties for the flux of many species on land and particularly over the oceans. Need to continue with or develop new partnerships with groups that have flux facilities (Niwot Ridge, Woods Hole Air Sea Interaction Tower). • Need new tools based on CO2 isotopes to better distinguish between photosynthetic and respiratory fluxes.

22. Potential Avenues for ATDInvolvement in Middle & Lower Trop. & Surface Meas. • Continued dev. of CO2 isotopic ratio instr. & partnerships with CU, Rice Univ., etc. • Continued development efforts to measure soluble gases. • In partnership with M3, ACD, & Universities, continued effort to develop and prove capabilities to identify the effects of past clouds.