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Global Modelling of the Atmospheric Hydrogen Budget. Nicola Warwick Centre for Atmospheric Science University of Cambridge 2 nd HyCARE Symposium, Laxenburg 19-21 Dec 2005. Outline. Model study of the present day hydrogen budget: initial results.

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global modelling of the atmospheric hydrogen budget

Global Modelling of the Atmospheric Hydrogen Budget

Nicola Warwick

Centre for Atmospheric Science

University of Cambridge

2nd HyCARE Symposium, Laxenburg 19-21 Dec 2005

outline
Outline
  • Model study of the present day hydrogen budget: initial results.
  • Incorporating H2 in p-TOMCAT (sources, sinks)
  • Model analysis: comparison with observations
  • Conclusions and future work
p tomcat h 2 model
p-TOMCAT H2 Model
  • Resolution: ~2.8° in horizontal, 31 vertical levels to 10 hPa
  • Simple chemistry:

- 5 H2 tracers, coloured by source

Sinks:

- OH fields: prescribed, taken from full chemistry model

- H2 dry deposition velocities, dependent on soil moisture (ECMWF)

Sources:

- surface H2 emissions: prescribed (present-day IPCC scenarios)

- photochemical production H2 calculated from prescribed HCHO fields taken from full chemistry model

  • ECMWF wind analyses for 1998.
h 2 sources surface emissions
H2 Sources: Surface Emissions

Surface H2 emissions / kg km2 month-1

*Emissions taken from latest IPCC scenarios, described in Dentener et al., 2004. Scaled to CO emissions.

h 2 sources photochemical production
H2 Sources: Photochemical Production
  • H2 produced from photolysis of HCHO in model.
  • Model HCHO fields compared to:
    • Satellite data:
    • Surface observations:
h 2 sources photochemical production6
H2 Sources: Photochemical Production
  • H2 produced from photolysis of HCHO in model.
  • Model HCHO fields compared to:
    • Satellite data:
    • Surface observations

GOME HCHO – April 1998

p-TOMCAT HCHO - April 1998

h 2 sources photochemical production7
H2 Sources: Photochemical Production
  • H2 produced from photolysis of HCHO in model.
  • Model HCHO fields compared to:
    • HCHO Satellite data
    • HCHO Surface observations:

Birkenes

(58°N,8°E)

Waldhof

(52°N,10°E)

Donon

(48°N,7°E)

Mauna Loa (19°N,155°W)

h 2 sinks reaction with oh
H2 Sinks: reaction with OH

250 hPa

  • CH4 lifetime due to reaction with OH = 9.6 yrs

500 hPa

700 hPa

Surface

90°S

30°S

30°N

90°N

Top: range of OH estimates in Lawrence et al. 2001,

Bottom: OH in p-TOMCAT

h 2 sinks dry deposition
H2 Sinks: Dry Deposition
  • H2 dry deposited to 5 landtypes (as Sanderson et al., 2003):
    • Savannah, forest, agriculture, grasslands: seasonal variation with ECWMF soil moisture.
    • A single wetlands/peat/tundra category: no seasonal variation

H2 dry deposition velocity (102cm/s) - January

H2 dry deposition velocity (102cm/s) - July

global surface h 2
Global Surface H2

Annual mean surface H2/ppbv

Surface H2/ppbv January to December

global distribution h 2 tracers
Global distribution H2 tracers

% of total H2 from biomass burning

(left = surface, right = 200hPa)

% of total H2 from industry

(left = surface, right = 200hPa)

% of total H2 from photochemistry

(left = surface, right = 200hPa)

latitudinal distribution total h 2
Latitudinal Distribution: Total H2

Model lat. max.

Model lat. min.

Model zonal mean

X – coastal/oceanic observations

X – land observations

latitudinal distribution h 2 budget terms
Latitudinal Distribution: H2 budget terms

Dry deposition

Photochemical Production

OH Destruction

Biomass burning

Industrial

Ocean

Nitrogen Fixation

Photochemistry

Latitudinal distribution of coloured hydrogen tracers

Latitudinal distribution of hydrogen production and loss

h 2 seasonal cycles barrow 71 n 157 w
H2 Seasonal Cycles: Barrow (71°N,157°W)

Biomass burning

Photochemistry

Nitrogen Fixation

Industrial

Ocean

h 2 seasonal cycles seychelles 55 e 5 s
H2 Seasonal Cycles: Seychelles (55°E, 5°S)

Biomass burning

Photochemistry

Nitrogen Fixation

Industrial

Ocean

h 2 seasonal cycles cape grim 145 e 41 s
H2 Seasonal Cycles: Cape Grim (145°E, 41°S)

Biomass burning

Photochemistry

Nitrogen Fixation

Industrial

Ocean

conclusions and future work
Conclusions and Future Work
  • Modelled H2 mixing ratios within 10% observations
    • Overestimate in SH, underestimate in NH (inaccuracies in sources and/or sinks)
    • H2 seasonal cycles small in both model and observations (phase differences in NH and SH)
  • Run multiannual/decadal simulations – trends / interannual variability in H2
  • Incorporate hydrogen isotopes
  • Chemistry-climate simulations using results from present-day study and H2 economy emission scenarios.