Choosing meteorological input for the global modeling initiative assessment of high‐speed aircraft

Abstract

Abstract. The global modeling initiative (GMI) science team is developing a three-dimensional chemistry and transport model (CTM) for use in assessment of the atmospheric effects of aviation. This model must be documented, be validated against observations, use a realistic atmospheric circulation, and contain numerical transport and photochemical modules representing atmospheric processes. The model must retain computational eificiency for multiple scenarios and sensitivity studies. To meet these requirements, a facility model concept was developed in which the different components of the CTM are evaluated separately. The assessment of the impact on the stratosphere of the exhaust of supersonic aircraft will depend strongly on the meteorological fields used by the CTM. Three data sets for the stratosphere were considered: the National Center for Atmospheric Research Community Climate Model (CCM2), the Goddard Earth ObservingSystem data assimilation system, and the Goddard Institute for Space Studies general circulation model. Objective criteria were developed to identify the data set that provides the best representation of the stratosphere. Simulations of gases with simple chemical control were chosen to test various aspects of model transport. The data sets were evaluated and graded on their performance on these tests. The CCM2 meteorological data set has the highest score and was selected for GMI. This objective model evaluation establishes a physical basis for interpretation of differences between models and observations. Further, the method provides a quantitative basis for defining model errors, for discriminating between different models, and for ready reevaluation of improved models. This will lead to higher confidence in assessment calculations.

Evaluation of transport in the lower tropical stratosphere in a global chemistry and transport model

“…by Hall et al [1999], the mean age at a location in the stratosphere for a constituent such as SF6 with a steady tropospheric trend is the difference between the time of a measurement and the time in the tropospheric time series when the measured value matches the troposphere value. The age of air is determined using CTMwc, cM and…”

“…The mean age, the mass weighted average of the transit times from the tropical tropopause to any given location, is a sensitive diagnostic of model transport [Hall and Plumb, 1994;Hall et al, 1999]. Model calculations of mean age were compared with the age determined from observations of SF 6 and CO2 as part of Models and Measurements Intercomparison II [Park et al, 1999].…”

Simulations of column-averaged CO<sub>2</sub> and CH<sub>4</sub> using the NIES TM with a hybrid sigma-isentropic (σ-θ) vertical coordinate

“…The use of different meteorological fields in driving chemical transport models can lead to diverging distributions of chemical species in the upper troposphere/lower stratosphere (UTLS) region (Douglass et al, 1999). Several studies based on multi-year CTM simulations have shown that vertical winds directly supplied from analyses can result in an overprediction of the strength of the stratospheric circulation and an under-prediction of the age of air (Chipperfield, 2006;Monge-Sanz et al, 2007).…”

Quantifying errors in trace species transport modeling

“…The numerical experiment is straightforward. With a specified pattern of constant surface emissions, we follow the buildup and dispersion of fossil-fuel CO 2 (21) as a conserved tracer throughout the atmosphere for 10 years by cycling 1 year of archived meteorological fields from the Goddard Institute for Space Studies middle atmosphere model (14,22). Two scientific applications are addressed.…”