First observations of atmospheric Hydrogen Peroxide (H 2. ) and Methylhydroperoxide (CH 3

Size: px

Start display at page:

Download "First observations of atmospheric Hydrogen Peroxide (H 2. ) and Methylhydroperoxide (CH 3"

Agatha Smith
5 years ago
Views:

First observations of atmospheric Hydrogen Peroxide (H 2 ) and Methylhydroperoxide (CH 3 OOH) in West Antarctica: comparison of experiment and model results Markus M. Frey a, Richard W.

1 First observations of atmospheric Hydrogen Peroxide (H 2 ) and Methylhydroperoxide (CH 3 OOH) in West Antarctica: comparison of experiment and model results Markus M. Frey a, Richard W. Stewart b, Joseph R. McConnell c, Roger C. Bales d a Department of Hydrology and Water Resources, University of Arizona, 1133 E.North Campus Drive, Tucson AZ 85721, USA. b Atmospheric Chemistry and Dynamics Branch, National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), Greenbelt, Maryland, USA. c Desert Research Institute, Divison of Hydrologic Sciences, 2215 Raggio Parkway, Reno, NV 89512, USA. d University of California, Merced, 4225 N. Hospital Road, Bldg 1200, Atwater, CA 95301, USA. Department of Hydrology & Water Resources University of Arizona U.S. International Transantarctic Scientific Expedition

Results from the Atmospheric Chemistry Program on U.S. ITASE 2000-2003 0. Context 1. Methods 2. Experimental Results 3. Photochemical Model Runs 4.

2 Results from the Atmospheric Chemistry Program on U.S. ITASE Context 1. Methods 2. Experimental Results 3. Photochemical Model Runs 4. Summary/Conclusions Research Questions Peroxides (H 2 /ROOH): a diagnostic tool of the oxidative state of the polar atmosphere? Spatial variability of peroxides? Importance of organic peroxides in the polar troposphere? The upper snowpack: sink or source?

3 Polar Tropospheric Chemistry of Peroxides Photochemistry hν,o 3, NO x, HO x CO, CH 4, HCHO, ROOH, NMHC H 2,HCHO NO/HNO 3, HCl... Snow Pack Atmosphere-Snow Interactions with implications for Atmospheric Chemistry and Ice Core Interpretation Ice Core Record

4 International Trans Antarctic Scientific Expedition The Region: Latitude 76 to 90 S Elevation 1232 to 2810 m Temperature -24 to 49 C Accumulation/yr 8 to 44 cm-swe

5 U.S. ITASE: an over-land traverse

6 U.S. ITASE Atmospheric Chemistry Program 3-5 days per site Peroxides, HCHO Ozone, Meteorology

7 2-Channel Detector of Atmospheric Peroxides CH1: total peroxides CH2: HPLC based on Sigg (1990) and Kok (1995) transfer from gas into aqueous phase in glas coil scrubber (T,p) separation of peroxides on HPLC column enzyme catalyzed reaction with p-ethylphenol flurescence detection (LOD < 50 pptv)

8 Atmospheric mixing ratios of H 2 and CH 3 OOH

9 Latitudinal Gradient of H 2 and CH 3 OOH

10 Firn Air Experiments Diffusion Flux F [molec m -2 s -1 ] fct( c/ z,t,p,ρ) Summer Snowpack S: a net source of H 2 a physical MHP snow pack source not important

11 Photochemical Model Runs at Byrd (80 S) and South Pole (90 S) How does the model match the experiment? Input Output Observations T air, p (AWS) CO, CH 4, surface-o 3 (CMDL) O 3 burden (TOMS) NASA-GSFC Photochemical Box Model (e.g. Stewart, 2004) Model Parameters dry deposition rate (Hauglustaine, 1994) reaction rates Heterogeneous source flux of H 2 and HCHO NO source H 2, CH 3 OOH, HCHO, NO, OH Observation Mean summer mixing ratios H 2, CH 3 OOH, HCHO

12 Model Output: Byrd Surface Camp (80 S, 1537 m a.m.s.l.) MHP observed is higher than best model fit: OH 1.6x10 6 cm -3 F NO 7x108 cm -3 s -1 NO ~20 pptv Black - model output Color - observations

13 Model Output: South Pole (90 S, 2810 m a.m.s.l.) HCHO observed is higher than best model fit: OH 3x10 6 cm -3 F Nx109 cm -3 s -1 NO ~30-40 pptv Black - model output Color - observations

14 Model Results Par Byrd South Pole F H2O2 [cm -3 s -1 ] x10 5 F HCHO [cm -3 s -1 ] x10 4 OH [10 6 cm -3 ] F NO [cm 3 s -1 ] 7x10 8 2x10 9 NO [pptv] ~20 ~30-40 No x Sensitivity Analysis shows: F NO increase leads to HCHO production at the expense of MHP NO source and background level constrained by H 2, MHP and HCHO

15 Summary H pptv (25-80% of levels at Summit/Greenland); decrease between Byrd and South Pole by 60% CH 3 OOH (MHP), only important organic peroxide pptv (comparable to coast); levels drop between Byrd and South Pole by 80% MHP: H 2 ratio range between Conclusions evidence that summer snowpack is a net source of H 2 (a physical snow pack source of MHP is not likely) Photochemical Box Model runs at Byrd and South Pole show: - match with observations only with heterogeneous source for H 2 and HCHO - modeled OH compares to previous observations - model does not allow for high NO (e.g. >100 pptv) The anti-correlation between MHP and HCHO allows for optimization of F NO : source term and background of NO can be constrained with observations of H 2, MHP and HCHO

Frey, et al. Climate sensitivity of the H 2 O 2 ice core record 1

Frey, et al. Climate sensitivity of the H 2 O 2 ice core record 1 Climate sensitivity of the century-scale hydrogen peroxide (H 2 O 2 ) record preserved in 23 ice cores from West Antarctica Markus M. Frey