1. Constraining the N 2 O budget using isotopologues and isotopomers Y. L. Yung, S. P. Kim, M. C. Liang and R. L. Shia Divisions of Geological and Planetary Sciecnes California Institute of Technology B41G-02 AGU - Dec 13, 2007 (Thur) B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

2. Method 14 N 14 N 16 O (446) 14 N 15 N 16 O (456) 15 N 14 N 16 O (546) 14 N 14 N 18 O (448) B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

3. Known Sources B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

4.  Goal: Calculate the gradient of a cost function with respect to initial control variables. The Adjoint Method Steps: 1. Linearize the model 2. Transpose the linear model B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

5. Tangent linear and Adjoint Model Compiler (TAMC)  Examples MIT ocean model Hamburg Ocean Primitive Equation Model (HOPE) Tracer Model (TM2)  Created for Fortran 77 with some extensions for 90/95  Automatic generation of adjoint code  Takes top-level routine and creates adjoint routines  Follows all guidelines in Giering (1998) B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

6. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

7. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

8. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

9. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

10. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

11. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

12. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

13. What is the uncertainty of this budget projection? B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers

14. Conclusions  The IPCC 2007 N 2 O budget appears to be consistent with the isotopic data  Isotopic analysis narrows uncertainty range of the model budget  Extend the model to the pre-industrial revolution  Site preference data for 15 N provides the most sensitive discrimination between natural and anthropogenic sources of N 2 O. B41G-02 (AGU 2007) Yung et al., Constraining the N2O budget using isotopologues and isotopomers