Water tracers and isotopic fractionation in CAM (challenges and opportunities ) David Noone Program in Atmospheric and Oceanic Sciences, and Cooperative Center for Research in Environmental Sciences University of Colorado, Boulder, CO, USA Also, B. Riley, C. Still, S. Wong N. Mahowald, A. Gettelman, A. Dessler, J. Randerson, P. Rasch, P. Thornton, K Oleson, G.Bonan …

Overview Nature of the problem Applications to science, physics and code What can we learn with isotopes? Current development status of isoCAM and isoCLM Implementation features/facilities Few “heads up” conclusions

Isotopic fractionation The substituted molecule is slightly heavier, allowing a different partitioning of energy between translational, vibration and rotational states. Isotopic fractionation is a quantum mechanical effect. Liquids (and solids) have additional vibration states due to intermolecular forces. So, for the same energy more of the light isotopes can be liberated from a liquid surface. (as 25°C, 1 percent more). The liquid is enriched, the vapor is depleted.

Hydrologic cycle with isotopic exchange International Atomic Energy Agency “Delta values”    = (R/R standard -1)x1000 R = moles of H 2 18 O/moles of H 2 16 O

Fate of water from South America DJFJJA 18 O content of rain with South American source (permil) MUGCM (Noone 2001)

Science targets - isotope model requirements 1. Paleoclimate applications - polar, alpine, surface ocean (deep ocean?) 2. Atmospheric hydrology and cloud processes - improving cloud parameterizations, boundary layer interactions, microphysics - stratosphere troposphere exchange - water in the general circulation 3. Terrestrial hydrology - energy budgets, water budgets/resources - biogeochemistry Also, sources and sinks of water - variability and changes in water budgets Ability to completely check on model hydrology 2 and 3 are hardest problems from a numerical/physics standpoint Very successful NCAR Isotope Meeting – all groups represented

CCM3 prototype

GNIP Obs. CAM2 Reasonable first simulation of water isotopes in precipitation in CAM2. Jung-Eun Lee and Inez Fung CAM2 - Precipitation Weighted Annual Mean  18 O in Precipitation

Mean Annual  D in vapor CAM2 Observed Nebraska, USA (Ehhalt, 1974) Heidelberg, Germany (Taylor, 1972: only up to 5 km) Stratosphere (Pollock, 1980) From Araguas-Araguas et al., 2000 CAM 2 captures general feature of the vertical profile of water isotopes in vapor. But minimum value too low--first guess: need more condensate in CAM2 upper tropopause, oxidation of methane (?) Jung-Eun Lee and Inez Fung

Isotopic depletion in the region of the tropopause Fig. 2. Observations in the TTL compared with model calculations that used dDice= –565. The dashed box represents ATMOS data of Kuang et al. Mean tropopause level is 14.4 ± 0.5 km. Webster and Heymsfield, Science, 2003

Analytic Model of Isotopes v. Alt Rayleigh Curve (Gettelman, in preparation, 2004)

CCM3 - Annual zonal mean  18 O CONTROL NO DEEP PLUMES

Messages from CRYSTAL Lots more ice than we might expect from model Stark difference between conditions in plumes versus large scale. Model probably OK on an “area average”, but smaller scale variability is very large (e.g. data 100x10 -6 of ice, while models have 20x10 -6 of water) While BULK is correct, processes not necessarily well enough represented (processes governing isotopes same as those of cirrus - thus insight to cloud forcing, etc)

Land model – H , HDO (and CO 18 O) LSMv1 migrating to CLM3 Performs extraordinarily well when forced with observed meteorology

Land surface exchange model (LSM) (Noone, Riley, et al., in preparation, 2004)

Implementation in CAM/CLM Water (and isotope) tracking in atmosphere (CAM3) Water (and isotope) tracking in land model (CLM3) Provides generic framework for any “water/aqueous” species i.e. explicit form of wet deposition, dissolved species Water isotopes: H2O, HDO, H 2 18 O (also HTO, H 2 17 O) Isotope physics done at smallest scale possible while sticking to “bulk” assumptions Track (exactly!) every bit of water in CAM, so can use isotopes to deduce problems in, e.g., microphysics, convective fluxes, … What about ocean tracers? Presently “working” code now, target for science start mid-2004 CAM3 isotopes will contribute to new isotopic intercomparison project (also GISS, MU, ECHAM, Hadley Center, Frontier…)

CAM synergistic developments WACCM include stratospheric chemistry, O3 exchange New “Data” dynamic core and data assimilation Facilitate tracer assimilation, transport computations “isotopic reanalysis” is of great value for proxy interpretation Mesoscale modeling - MM5 nearly has isotopes with ISOLSM (LBL for ARM) - WRF code structure in place to more easily facilitate isotopes, isotopic development at planning stage - Also, WRF at cloud resolving scales can match LES isotope simulations at CU..

Isotopes add rigor for new parameterization development Adds additional requirements of systems (especially mass conservation/consistency issues) Exercise of adding water tracers useful as it finds inconsistencies in mass budgets New parameterization schemes will need to be used for various tracer studies Being mindful of applications when physics is build is a must..