1 / 18

The 1D model of IPSL : IPSL05

The 1D model of IPSL : IPSL05. Intercomparison of 1D photochemical models of Titan atmosphere. Nathalie Carrasco Workshop ISSI Bern - 17-19th march 2009. Inputs presently implemented. Turbulent transport K(z): Hidayat 1997 Photochemical database ~Hébrard 2006

donkor
Download Presentation

The 1D model of IPSL : IPSL05

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The 1D model of IPSL : IPSL05 Intercomparison of 1D photochemicalmodels of Titan atmosphere Nathalie Carrasco Workshop ISSI Bern - 17-19th march 2009

  2. Inputs presently implemented • Turbulent transport K(z): Hidayat 1997 • Photochemical database ~Hébrard 2006 • Temperature profile T(z): Vervack 2004 • P profiles, based on N2+CH4 density profiles • 0-325 km N2+CH4Yelle • 325 - 1300 km N2Vervack

  3. History of the model • Based on the model of D. Toublanc, developed in Bordeaux, then Toulouse • Toublanc et al. 1995, Icarus 113 • Same root as Dobrijevic’s model • Identical grid (no, rougher : 10 km altitude instead of 5 for MD) • Same solver for the resolution of the continuity equation (LU method) • Noticeable difference : coded in C language instead of fortran

  4. Evolution of the 1D model since SL thesis • UV flux description, dependence in latitude • Lebonnois, 2000, Thesis • Lebonnois and Toublanc, 1999, JGR • Extension to a 2D chemistry-transport model • Lebonnois et al, 2001, Icarus • Parameterization of polymerization • Lebonnois et al, 2002, Icarus • Lebonnois, 2005, PSS • Heterogeneous reactions • Lebonnois et al, 2003, Icarus

  5. UV flux description • Aim : model the UV absorption in the night-side of Titan at higher altitudes for latitudinal and seasonal dependence of the UV fluxes

  6. UV flux description • 3D grid

  7. UV flux description • Axial symmetry along the Sun-Titan axis • Hypothesis : global homogeneous distribution of the absorbing and diffusing species (gazeous+aerosols) • 1D profiles from model, adjusted with observational data • Gazeous compounds : Vervack et al 2004, Icarus ; Coustenis and Bezard, 1995, Icarus (observations) ; Lebonnois et al. 2001 (model) • Aerosols : … (observations) ; Rannou et al, 1995, Icarus ; 2002 Nature (model) • Monte-Carlo computation of the actinic fluxes in each cell

  8. UV flux description • Calculation of the diurnal mean of the actinic flux vertical profile as a function of the wavelength, latitude and season

  9. UV flux description • Within the photochemical model, computation of the photodissociation rates from these profiles

  10. Evolution of the 1D model since SL thesis • UV flux description, dependence in latitude • Lebonnois, 2000, Thesis • Lebonnois and Toublanc, 1999, JGR • Extension to a 2D chemistry-transport model • Lebonnois et al, 2001, Icarus • Parameterization of polymerization • Lebonnois et al, 2002, Icarus • Lebonnois, 2005, PSS • Heterogeneous reactions • Lebonnois et al, 2003, Icarus

  11. Extension to a 2D model • Latitudinal grid : 10° • 17 1D columns (central column at the equator) • Vertical diffusion in each 1D box between 0 and 1300 km • Columns horizontally coupled • Horizontal turbulent diffusion between 0 and 1300 km : Kh adjusted with…? • 2D advection between 0 and 550 km • Analytical description of 2D winds based results from the GCM of IPSL (Hourdin et al, 1995)

  12. Extension to a 2D model

  13. Evolution of the 1D model since SL thesis • UV flux description, dependence in latitude • Lebonnois, 2000, Thesis • Lebonnois and Toublanc, 1999, JGR • Extension to a 2D chemistry-transport model • Lebonnois et al, 2001, Icarus • Parameterization of polymerization • Lebonnois et al, 2002, Icarus • Lebonnois, 2005, PSS • Heterogeneous reactions • Lebonnois et al, 2003, Icarus

  14. Polymerization • 3 polymer growth schemes • Acetylene polymer (linear) • PAH growth (aromatic formation) • HCN and nitrile polymer

  15. Polymerization • Precursor level • Threshold chosen : N1=N2=N3 = 20 gaz molecules incorporated in one polymer macromolecule • Corresponds to a nucleus of ~7-8 Å • Beyond this threshold the growth is no longer chemical, but microphysically modelled

  16. Evolution of the 1D model since SL thesis • UV flux description, dependence in latitude • Lebonnois, 2000, Thesis • Lebonnois and Toublanc, 1999, JGR • Extension to a 2D chemistry-transport model • Lebonnois et al, 2001, Icarus • Parameterization of polymerization • Lebonnois et al, 2002, Icarus • Lebonnois, 2005, PSS • Heterogeneous reactions • Lebonnois et al, 2003, Icarus

  17. Heterogeneous reactions H H H H H H • Hypothesis • Balance of the hydrogen budget : only conversion 2H->H2 • no sink or source through heterogeneous chemistry, neither in the gazeous phase, nor on the aerosol surface • Estimations • N : number of adsorption sites. Taken from the model of Toon et al 1992, and related to an average size of the aerosol rhaze= 0.1µm • H : speed of collision, assimilated to the thermal kinetic speed of atomic hydrogen •  : cross section for H2 desorption : taken from Bakes et al. 2003

  18. Conclusion • For the purpose of the first 1D models intercomparison meeting • Same root as MD • But some significant changes • Programmed in C language • UV flux calculated for a 3D absorbing and diffusing atmosphere, with a 1D description of the gazeous and aerosol profiles

More Related