Status of LPJ estimates of biosphere fluxes: isoprene emissions, H 2 uptake Colin Prentice Pru Foster Leilei Dong Renato Spahni Rita Wania

Biogenic flux fields Methane √ Peatland emissions - Rita √ Wet land & soil emissions & uptake - Renato Hydrogen √ NPP, DEC uptake diffusion model - Pru Nitrogen * N 2 O correlation - Rita DEC NO and NH 3 Canopy √ LAI, stomatal conductance, DEC roughness length Isoprene * versus HCHO - Pru Fire DEC CO, N 2 O, NO x, CH 4, H 2 - Lei Lei √ delivered in June, * preliminary results to be discussed today DEC to be provide in December

Isoprene emission formulation GPP / 12 7 I =  LAI  emission factor at STP PFT relative values taken from Guenther 2006, with reduction to broadleaves (Millet et al 2008 JGR) global value tunable (currently 1)  deviation from STP = (c i,370 / c i ) exp 0.1 ( T leaf - 30 o C) GPP - gross primary productivity / 12 to convert gC / m2 /sec to moles CO 2 /m2 / sec / 7 to convert moles CO 2 to moles of isoprene Based on Arneth et al 2007 & Niinemets 1999

T leaf T leaf = T day R net, sw = net shortwave downward radiation = daily SW / day length * (1 - albedo)  E = latent heat energy loss through evapotranspiration  c p = volumetric heat capacity of air (1200 J / m 3 / o C) r bh = boundary layer resistance to heat (s / m) = 5 s/m conifers; 40 s/m grasslands ; (Kelliher 1993 Oecologia) R net, sw -  E 4  T day 3 +  c p / r bh Goudriaan & van Laar 1994

Palmer US GOME HCHO HCHO observations from GOME satellite (Palmer et al JGR 2006) Isoprene is the dominant source of HCHO - although smears ~ 50 km Isoprene drives the variability in HCHO columns

SEASONALITY OF GOME HCHO COLUMNS (9/96-8/97) JUN MAY GOME GEOS-CHEM (GEIA) LPJ surface flux Detection limit AUG JUL SEP 1997 monthly emissions Seasonal cycle ok but pattern is poor. Palmer et al 2006

GOME GEOS-CHEM LPJ What’s wrong with the LPJ isoprene emission pattern? Temperate needleleaf emission factor too low? JULY 1997

GOME GEOS-CHEM LPJ What’s wrong with the LPJ isoprene emission pattern? II. GPP is not driving Texas hot spot July 1997 LPJ GPP To explore: LAI T leaf calculation Needleleaf emission factor

US HCHO vs LPJ isoprene LPJ monthly isoprene emission over U.S. GOME HCHO observations over U.S. (Palmer) Seasonality OK, but interannual variability is low, see August

Global emissions LPJ 2002 Isoprene GOME 2002 HCHO

Globally, as in North America Pattern isn’t quite what is expected LPJ doesn’t capture inter annual variability > But seasonality looks ok (not shown) Annual total HCHO GOME & SCIAMACHY de Smedt 2008 LPJ isoprene annual total emission

Hydrogen uptake strategy As in the methane uptake model used by Renato (Curry 2007 GBC) Surface flux = (D soil k ) 1/2 C 0 D soil - diffusion coefficient in soil (cm 2 / sec) k - oxidation rate, i.e. uptake, constant (s -1 ) C 0 - H 2 concentration at the surface (cm -3 )

Diffusion coefficient D soil D soil = D g  2  air  ) 2.9 F cp D g - diffusivity of hydrogen in air, T dependent (Hirschfelder et al 1954)  - total porosity of soil (Reynolds et al 1999)  air - air filled porosity of soil (=  - water filled porosity - from LPJ soil moisture) F cp - fraction of soil particles larger than 2  m (Reynolds et al 1999) From Smith-Downey’s thesis, very similar to Curry

k, uptake rate of H 2 within soil k = k max f(T) f(O) f(M) k max = sec -1 f(T) = 1 / [1 + exp( T ) ] f(O) = O , O - Soil organic carbon content (Reynolds 1999) 0. M < 8% f(M) = M % < M < 15% 1. M > 15% M, saturation = water filled pore space  / total pore space,  Again, following Smith-Downey’s thesis