The Community Climate System Model version 3 (CCSM3) has recently been developed and released to the climate community. CCSM3 is a coupled climate model with components representing the atmosphere, ocean, sea ice, and land surface connected by a flux coupler. CCSM3 is designed to produce realistic simulations over a wide range of spatial resolutions, enabling inexpensive simulations lasting several millennia or detailed studies of continental-scale dynamics, variability, and climate change. This paper will show results from the configuration used for climate-change simulations with a T85 grid for the atmosphere and land and a grid with approximately 1°resolution for the ocean and sea ice. The new system incorporates several significant improvements in the physical parameterizations. The enhancements in the model physics are designed to reduce or eliminate several systematic biases in the mean climate produced by previous editions of CCSM. These include new treatments of cloud processes, aerosol radiative forcing, landatmosphere fluxes, ocean mixed layer processes, and sea ice dynamics. There are significant improvements in the sea ice thickness, polar radiation budgets, tropical sea surface temperatures, and cloud radiative effects. CCSM3 can produce stable climate simulations of millennial duration without ad hoc adjustments to the fluxes exchanged among the component models. Nonetheless, there are still systematic biases in the ocean-atmosphere fluxes in coastal regions west of continents, the spectrum of ENSO variability, the spatial distribution of precipitation in the tropical oceans, and continental precipitation and surface air temperatures. Work is under way to extend CCSM to a more accurate and comprehensive model of the earth's climate system.

[1] Recent satellite observations and dynamical studies have demonstrated the existence of filamentary structures in chemical tracer fields in the stratosphere. It is also evident that such features are often below the spatial resolution of the highest-resolution Eulerian models that have been used up to the present time. These observations have motivated the development of a novel Chemical Lagranigan Model of the Stratosphere (CLaMS) that is based on a Lagrangian transport of tracers. The description of CLaMS is divided into two parts: Part 1 (this paper) concentrates on the Lagrangian dynamics, i.e., on the calculation of trajectories and on a completely new mixing algorithm based on a dynamically adaptive grid, while part 2 describes the chemical integration and initialization procedure. The mixing of different air masses in CLaMS is driven by the large-scale horizontal flow deformation and takes into account the mass exchange between the nearest neighbors determined by Delaunay triangulation. Here we formulate an isentropic, i.e., two-dimensional version of the model and verify the mixing algorithm using tracer distributions measured during the space shuttle CRISTA-1 experiment where highly resolved stratospheric structures were observed in early November 1994. A comparison of the measured Southern Hemispheric N 2 O distribution with CLaMS results allows the intensity of simulated mixing to be optimized. The long-term robustness of the transport scheme is investigated in a case study of the 1996-1997 Northern Hemisphere polar vortex. This study further provides a dynamical framework for investigations of chemical arctic ozone destruction discussed in part 2.

Abstract. During the second part of the TROCCINOX campaign that took place in Brazil in early 2005, chemical species were measured on-board the high-altitude research aircraft Geophysica (ozone, water vapor, NO, NO y , CH 4 and CO) in the altitude range up to 20 km (or up to 450 K potential temperature), i.e. spanning the entire TTL region roughly extending between 350 and 420 K.Here, analysis of transport across the TTL is performed using a new version of the Chemical Lagrangian Model of the Stratosphere (CLaMS). In this new version, the stratospheric model has been extended to the earth surface. Above the tropopause, the isentropic and cross-isentropic advection in CLaMS is driven by meteorological analysis winds and heating/cooling rates derived from a radiation calculation. Below the tropopause, the model smoothly transforms from the isentropic to the hybrid-pressure coordinate and, in this way, takes into account the effect of large-scale convective transport as implemented in the vertical wind of the meteorological analysis. As in previous CLaMS simulations, the irreversible transport, i.e. mixing, is controlled by the local horizontal strain and vertical shear rates.Stratospheric and tropospheric signatures in the TTL can be seen both in the observations and in the model. The composition of air above ≈350 K is mainly controlled by mixing on a time scale of weeks or even months. Based on CLaMS transport studies where mixing can be completely switched off, we deduce that vertical mixing, mainly driven by the vertical shear in the tropical flanks of the subtropical jets and, Correspondence to: P. Konopka (p.konopka@fz-juelich.de) to some extent, in the the outflow regions of the large-scale convection, offers an explanation for the upward transport of trace species from the main convective outflow at around 350 K up to the tropical tropopause around 380 K.

[1] The first simulations of stratospheric chemistry using the Chemical Lagrangian Model of the Stratosphere (CLaMS) are reported. A comprehensive chemical assimulation procedure is described that combines satellite, airborne, and balloon-borne tracer observations with results from a two-dimensional photochemical model simulation. This procedure uses tracer-tracer and tracer-potential vorticity mapping techniques. It correctly reproduces all basic features of the observed tracer distribution. This methodology is used to generate the initial composition fields that will be used for subsequent chemical simulations. Results from a 6-day simulation starting on 20 February 1997 show that the simulated HNO 3 distribution displays the correct morphology, although the extremes of the observed HNO 3 distribution are underestimated. The simulated ClO distribution exhibits a similar morphology to the observed Microwave Limb Sounder ClO distribution. Because of unseasonally low temperatures in the arctic lower stratosphere during spring 1997, high levels of chlorine activation are maintained in the simulation, resulting in up to 1.8 ppmv of chemical ozone loss over a 5-week period. Furthermore, simulations show strong spatially inhomogeneous chemical ozone depletion within the polar vortex and show that greatest ozone loss is confined to the vortex core. These results are confirmed by several Halogen Occultation Experiment and ozone sonde profiles, although the minimum ozone concentrations are overestimated. These studies demonstrate that CLaMS is capable of simulating vortex isolation, an essential feature of the polar vortex.

Abstract. A new set of hygrometers based on the Lyman ct photofragment fluorescence technique has been developed for operation on aircraft and balloons in the stratosphere and upper troposphere. They combine technical details from existing fluorescence hygrometers with several improvements in order to achieve the highest data quality and to minimize maintenance and operational procedures. With these instruments, stratospheric H20 measurements can be accomplished with a precision of < 0.2 ppmv at 1 s integration time, as has been demonstrated both in the laboratory and under field deployment. The design enables a rapid exchange of the air sample of the order of 1 s for fast measurements of small-scale variations of the H20 mixing ratio in the atmosphere. The hygrometer is calibrated using a laboratory calibration bench with approximately 4% accuracy. Measurements made by the hygrometer are compared with a frost point hygrometer during an aircraft mission at H20 mixing ratios from 280 to 8 ppmv, yielding an agreement between both techniques within the instrumental errors.