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Overview |
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The NRL CHEM2D Ozone Photochemistry Parameterization (or CHEM2D-OPP) offers fast, reliable computation of the net ozone photochemical tendency for use in high-altitude numerical weather prediction (NWP) and climate models. It is based on output from the fully interactive zonally averaged NRL CHEM2D photochemical-dynamical model of the middle atmosphere. |
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CHEM2D-OPP consists of a set of photochemical coefficients stored as functions of pressure , latitude, and month derived from a linearized expansion of the ozone photochemical tendency equation, based on the approach of Cariolle and Deque [1986]. |
Development of CHEM2D-OPP is supported in part by the NOAA/NASA/DoD Joint Center for Satellite Data Assimilation. See the results of a preliminary test of CHEM2D-OPP in the NCEP Global Forecasting System (GFS), presented in the June 2006 JCSDA Quarterly Newsletter. CHEM2D-OPP was incorporated into the operational GFS on 22 August, 2006. |
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Usage and Access |
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Use of the CHEM2D-OPP for research purposes is welcome and encouraged. If you are interested in obtaining the latest version of CHEM2D-OPP, please contact john.mccormack@nrl.navy.mil. |
Users Group: For access to the data files, code, documentation, and important updates please sign up to join the users group. |
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Version History, Bug Reports, & General Feedback |
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Watch this space for updated information on CHEM2D-OPP. |
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5 September 2005: CHEM2D-OPP Version 2.1 now available. This is the complete 4-term set of gas-phase ozone photochemical parameters. This replaces the 2-term preliminary (Version 0) CHEM2D scheme and the 3-term (Version1.x) CHEM2D scheme. |
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10 October 2005: CHEM2D-OPP Version 2.3 now available. Changes include: (1) second term now corresponds to ozone relaxation time, not odd-oxygen relaxation time as in V2.1, main difference is in values of term 2 in mesosphere; (2) column sensitivity term (i.e., term 4) is now scaled appropriately so that it describes the ozone tendency, not odd-oxygen tendency. Result is that values of term 4 peak in upper stratosphere/lower mesosphere and decrease at higher altitudes, thus being more computationally stable than in V2.1. |
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3 March 2006: CHEM2D-OPP Version 2.4 now available. Changes include: (1) increased number of latitudes in tabulated values [35 latitudes, 85oS-85oN in 5o steps]; (2) coefficients are smoothed in latitude, mainly to reduce sharp gradients in relaxation term at high latitudes in winter; (3) vertical interpolation bug fixed so that surface values do not contain discontinuities (e.g., positive values of ozone relaxation time at surface). Testing CHEM2D-OPP V2.4 in NOGAPS-ALPHA forecast model and UKMO data assimilation system shows that systematic biases in temperature perturbation term (T-To) exist when using CIRA86 data set to specify background temperatures, particularly at high latitudes in winter. Use of updated temperature climatology is recommended, since CIRA86 has been shown to have 5-10 K warm bias compared to other middle atmosphere temperature climatologies (Randel et al., J. Climate, 17, 2004). Many models exhibit a cold bias at high latitudes in winter that may adversely impact parameterized photochemistry through the temperature term. This effect can be reduced in the current CHEM2D-OPP scheme by turning off temperature term during polar night. |
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17 July 2006: CHEM2D-OPP Version 2.5 now available. Changes include: improved vertical interpolation of temperature coefficients, eliminating spuriously large values of d(P-L)/dT between 10-20 hPa pressure levels. To reduce the effect of systematic bias between model temperatures and CIRA86 temperatures at high latitudes, the more recent SPARC temperature climatology has been tested with CHEM2D-OPP in NOGAPS-ALPHA. Preliminary results of a 1-year integration with this updated climatology yield improved CHEM2D-OPP performance at high southern latitudes in winter. |
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References |
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Cariolle, D., and M. Déqué, Southern hemisphere medium-scale waves and total ozone disturbances in a spectral general circulation model, J. Geophys. Res., 91, 10,825-10,846, 1986. |
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McCormack, J.P., et al., NOGAPS-ALPHA model simulations of stratospheric ozone and dynamics during the SOLVE2 campaign, Atmos. Chem. Phys., 2401-2423, 2004. |
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McCormack, J.P., S.D., Eckermann, D.E. Siskind, T. McGee, CHEM2D-OPP: A new linearized gas-phase ozone photochemistry parameterization for high-altitude NWP and climate models, Atmos. Chem. Phys., (6), 4943-4972, 2006. |
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Related Links |
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Updated 30 October, 2006. Questions or comments can be sent here.