Using the Whole Atmosphere Community Climate Model to Study Processes Linking Solar Variability and Climate Change Byron Boville, Rolando Garcia, Doug Kinnison, Dan Marsh, Ray Roble, Fabrizio Sassi, and Stan Solomon National Center for Atmospheric Research SORCE Science Meeting 6 December 2003 1 Motivation for the WACCM Model • Coupling between atmospheric layers: - Waves transport energy and momentum from the lower atmosphere to drive the QBO, SAO, sudden warmings, mean meridional circulation - Solar and geomagnetic inputs, e.g., auroral production of NO in the mesosphere and downward transport to the stratosphere - Stratosphere-troposphere exchange • Climate Variability and Climate Change: - What is the impact of the stratosphere on tropospheric variability, e.g., the Artic oscillation or “annular mode”? - How important is coupling among radiation, chemistry, and circulation? (e.g., in the response to O3 depletion or CO2 increase) (Roble, Geophysical Monographs, 123, 53, 2000) Jarvis, “Bridging the Atmospheric Divide” Science, 293, 2218, 2001 2 Motivation for the WACCM Model • Response to Solar Variability: - Recent satellite observations have shown that solar cycle variation is: 0.1% for total Solar Irradiance 5-10% at ~200nm - Radiation at wavelengths near 200 nm is absorbed in the stratosphere => Impacts on tropospheric climate may be mediated by stratospheric chemistry and dynamics UARS / SOLSTICE • Satellite observations: - There are several satellite programs that can benefit from a comprehensive model to help interpret observations - e.g., UARS, TIMED, EOS Aura 3 Heritage and Structure of the WACCM Model TIME GCM (ThermosphereIonosphere-Mesosphere Electrodynamics GCM) Mesospheric + Thermospheric Processes MOZART (Model for Ozone and Related Tracers) Chemistry + Dynamics + Physical processes CAM3 (Community Atmosphere Model, version 3) WACCM WACCM1: Non-interactive chemistry Valid to ~100 km WACCM2: Interactive chemistry Valid to ~100 km Current Work: Include ionosphere Extend validity to ~150 km 4 Dynamics Module Additions to the Original CAM3 Code • Fomichev parameterization of non-LTE IR (15 µm band of CO2) merged with CAM IR parameterization at ~65 km • Short wave heating rates due to absorption of radiation shortward of 200 nm and chemical potential heating merged with CAM SW parameterization at ~65 km • Gravity wave spectrum parameterization (Garcia/Lindzen) includes dissipation by molecular viscosity • Diffusion of momentum and heat by molecular viscosity (dominant above 100 km) • Diffusive separation of atmospheric constituents (above about 90 km) • Simple parameterization of ion drag 5 WACCM Heating Rate Approach 1) Heating Rates λ > 200nm (O3 and H2O) are derived in the CAM3 solar heating rate parameterization 2) Heating Rates λ < 200nm are derived using the WACCM2 inline parameterizations. This includes: • Direct Solar (minus bound energy) • Chemical Potential Heating (realized upon recombination) • Airglow loss (loss to space; decreases net heating) 3) Heating rates from CAM3 and WACCM2 parameterizations are merged at ~65km. 6 Middle Atmosphere Chemistry 50 species; 41 photolysis rates, 93 gas phase reactions, 17 heterogeneous reactions Long-lived Species: Misc: CFCs: HCFCs: Chlorocarbons: Bromocarbons: Halons: Constant Species: (17 species, 2 constant) CO2, CO, CH4, H2O, N2O, H2, O2 CCl4, CFC-11, CFC-12, CFC-113 HCFC-22 CH3Cl, CH3CCl3, CH3Br H-1211, H-1301 N2, N(2D) Short-lived Species: OX: NOX: ClOX: BrOX: HOX: HC Species: (31 species) O3, O, O(1D) N, NO, NO2, NO3, N2O5, HNO3, HO2NO2 Cl, ClO, Cl2O2, OClO, HOCl, HCl, ClONO2, Cl2 Br, BrO, HOBr, HBr, BrCl, BrONO2 H, OH, HO2, H2O2 CH2O, CH3O2, CH3OOH Interactive Model: species used in Solar and IR Heating Rate Modules 7 CH4 March Average (ppmv) HALOE Model 8 H2O Using Interactive Chemistry (WACCM2) HALOE/MLS WACCM2 Stratosphere / Mesophere Distribution: September 9 Total Column O3 (DU) EPTOMS 1997 EPTOMS 1998 WACCM2 yr5 WACCM2 yr2 10 Annular Modes in the Stratosphere and Troposphere Observations Model Weak vortex Weak vortex Strong vortex Strong vortex Baldwin and Dunkerton, Science, 2001 WACCM Note similarity to observations (and reversed color contours!) The salient features of the observations can be reproduced by the model. 11 Solar Cycle Studies: Issues to be Addressed • Response of the atmosphere to solar variability over the 11–year cycle – Mesosphere and lower thermosphere – Stratosphere – Troposphere: role of the stratosphere? • With particular attention to – Mechanism of variability in the lower atmosphere – Role of the QBO – Statistical significance – Potential sources of aliasing 12 Solar Cycle Studies: Model Inputs Courtesy of Judith Lean (NRL) and Tom Woods (CU/LASP) 13 Solar Cycle Dependence of Auroral Inputs Dan Marsh (NCAR/ACD) 14 Basic Methodology for Solar Inputs For λ > 200 nm: Heating rates based on CAM3 parameterization Photolysis using lookup table based on TUV model [Madronich & Flocke, 1998] For λ < 200 nm: Schumann-Runge bands parameterization: [Koppers & Murtaugh, 1996; Minschwaner & Siskind, 1993] Schumann-Runge continuum: Direct calculation using ~5-nm bins Lyman-α parameterization: [Chabrillat & Kockarts, 1997] EUV & X-ray parameterization, including photoelectrons: [Solomon & Qian, 2003 AGU, SA41B-0427] 15 Solar UV Energy Deposition in the Upper Atmosphere 16 Plan for Solar Cycle Studies • Use solar and geomagnetic inputs from one “typical” cycle Probably a recent one so that good measurements are available Proxy-based models using TBD inputs (F10.7, MgII c/w, Sn, Kp…) Daily / hourly cadence • Repeat using identical inputs for ~8–10 cycles Necessary to average the natural variability out of the troposphere Considerable computational expense • Compare effects in runs with and without an imposed QBO • For the future: Long-term runs with combined forcing, using historical proxy record Extreme computational expense • Ancillary work: High-spectral-resolution calculation of solar energy deposition Using model solar spectra and cross section band measurements Comparison with and validation of parameterizations 17 What the WACCM Model Doesn’t Do (yet) • Include possible effects of cosmic ray modulation of cloud nucleation • Include other high-energy solar and magnetospheric particles • Generate an internal QBO • Calculate upper ionosphere/thermosphere processes • Interactively couple with ocean and land surface models 18 Discussion What we would like from the solar irradiance measurement community: Spectrally-dependent estimates of: • Solar cycle variability (Especially in the ~250~350 nm range) • Solar rotational variability • Plage enhancements v. Sunspot blocking • Advice Eventually: Daily / hourly spectral measurements (More useful for TIME-GCM event studies than climatology) 19