[1] The NASA Langley Research Center and University of Wisconsin Regional Air Quality Modeling System (RAQMS) is used to estimate the tropospheric ozone budget over east Asia during the NASA Global Tropospheric Experiment (GTE) Transport and Chemical Evolution over the Pacific (TRACE-P) mission. The computed ozone budget explicitly accounts for stratosphere/troposphere exchange (STE) and in situ ozone production using on-line chemical calculations. The east Asian O 3 budget is computed during the period from 7 March to 12 April 2001. Gross formation dominates STE by a ratio of 7 to 1 in east Asia during TRACE-P. However, this ratio is strongly influenced by altitude of the tropopause. Approximately 30% of the ozone that is advected across the tropopause over east Asia is subsequently advected out over the western Pacific within the upper 4 km of the troposphere by the Japan jet. The average net photochemical production (gross formation-gross destruction) within the regional domain is 0.37 Tg d À1or 7% of the average flux at the eastern boundary of the domain during the TRACE-P time period. The budget analysis shows a very close balance between sources and sinks within the RAQMS regional domain during the TRACE-P time period. This balance results in very small average accumulation ($1 Tg) of O 3 in the east Asian region and very little net export averaged over the period (0.03 Tg d À1 ). The low ozone export from east Asia predicted by RAQMS during TRACE-P is a consequence of relatively high dry deposition rates, which are 37% of the gross ozone formation (1.469 Tg d À1 ) within the TRACE-P regional domain.

[1] During December 1999, polar stratospheric clouds (PSCs) were observed in the absence of conditions conducive to generation by topographic gravity waves. The possibility is explored that PSCs can be generated by inertia gravity waves (IGW) radiating from breaking synoptic-scale Rossby waves on the polar front jet. The aerosol features on 7 and 12 December are selected for comparison with theory and with simulations using the University of Wisconsin Nonhydrostatic Modeling System (UWNMS). Consistent with Rossby adjustment theory, a common feature in the UWNMS simulations is radiation of IGW from the tropopause polar front jet, especially from sectors which are evolving rapidly in the Rossby wave breaking process. Packets of gravity wave energy radiate upward and poleward into the cold pool, while individual wave crests propagate poleward and downward, causing mesoscale variations in vertical motion and temperature. On 12 December the eastbound DC-8 lidar observations exhibited a fairly uniform field of six waves in aerosol enhancement in the 14-20 km layer, consistent with vertical displacement by a field of IGW propagating antiparallel to the flow, with characteristic horizontal and vertical wavelengths of $300 and $10 km. UWNMS simulations show emanation of a field of IGW upward and southwestward from a northward incursion of the polar front jet. The orientation and evolution of the aerosol features on 7 December are consistent with a single PSC induced by an IGW packet propagating from a breaking Rossby wave over western Russia toward the northeast into the coldest part of the base of the polar vortex, with characteristic period $9 hours, vertical wavelength $12 km, and horizontal wavelength $1000 km. Linear theory shows that for both of these cases, IGW energy propagates upward at $1 km/hour and horizontally at $100 km/hour, with characteristic trace speed $30 m/s. The spatial orientation of the PSC along IGW phase lines is contrasted with the nearly horizontal filamentary structures in the PSC, which are indicative of flow streamlines. It is suggested that vertical displacement is a crucial factor in determining whether a PSC will form and that most PSCs are relatable to specific synoptic and mesoscale motions.

[1] During March-April 2001 the University of Wisconsin Nonhydrostatic Modeling System (UWNMS) was used to provide flight planning and estimation of ozone flux into the troposphere over East Asia in support of the Transport and Chemical Evolution over the Pacific (TRACE-P) mission. On 24 March a convective complex developed in eastern China and propagated eastward over the Pacific south of Japan. Aircraft and satellite observations, together with the UWNMS simulations, captured this convective event, which first entrained urban boundary layer air over Asia and then marine boundary layer air over the Pacific. The convective updraft split the subtropical westerly jet, deformed the tropopause upward, radiated gravity waves into the stratosphere, and induced a ring of stratospheric ozone to descend around its periphery into the middle troposphere. The DC-8 observations and UWNMS show a vault of moderate ozone ($65 ppbv) in the 8-12 km layer within the convection, with high stratospheric values ($100 ppbv) subsiding around the periphery into the troposphere near 6.5 km. A new two-scale method for diagnosing cross-tropopause ozone flux is compared with an annular volume estimate. During this 24 hour convective event, $0.8 Tg ozone entered the troposphere from the stratosphere, comparable in magnitude to ozone fluxes in midlatitude cyclones.

[1] Detailed analysis of mesoscale transport of ozone across the tropopause over east Asia during the spring of 2001 is conducted using regional simulations with the University of Wisconsin Nonhydrostatic Modeling System (UWNMS), in situ flight data, and a new two-scale approach to diagnosing this ozone flux. From late February to early April, synoptic activity regularly deformed the tropopause, leading to observations of ozone-rich (concentration exceeding 80 ppbv) stratospheric intrusions and filaments at tropospheric altitudes. Since model resolution is generally not sufficient to capture detailed small-scale mixing processes, an upper bound on the flux is proposed by assuming that there exists a dynamical division by spatial scale, above which the wind conservatively advects large-scale structures, while below it the wind leads to irreversible transport through nonconservative random strain. A formulation for this diagnosis is given and applied to ozone flux across the dynamical tropopause. Simulations were chosen to correspond with DC-8 flight 15 on 26-27 March over east Asia during the Transport and Chemical Evolution Over the Pacific (TRACE-P) campaign. Local and domain-averaged flux values using this method agree with other numerical and observational studies in similar synoptic environments. Sensitivity to numerical resolution, prescribed divisional spatial scale, and potential vorticity (PV) level is investigated. Divergent residual flow in regions of high ozone, and PV gradients tended to maximize flux magnitudes. We estimated the domain-integrated flow of ozone out of the lowermost stratosphere to be about 0.127 Tg/day. Spectral analysis of the wind field lends support for utilization of this dynamical division in this methodology.

[1] This observational and modeling study explores how the Southeast Asian summer monsoon outflow into the Southern Indian Ocean influences the life cycle of local anticyclones and leads to changes in the distribution of column ozone in the Southern Hemisphere (SH). A case study of the evolution of synoptic fields during August 1998 was performed to characterize the circulation leading to the average column ozone distribution known as the "ozone croissant," with a characteristic ozone maximum south of Australia and a minimum near South America. During this month, five phases of SH circulation were found to lead to distinctive ozone patterns, explaining the monthly location and extent of the SH column ozone maximum. An isentropic trajectory model was used to show the cross-equatorial flow from the Tibetan High into the SH at the near-tropopause level of 360 K. Outflow pulses are shown to be responsible for the amplification of observed anticyclones over the SH Indian Ocean and intensification of troughs south of Australia. This couplet establishes an ozone transport pathway from tropical lower stratospheric regions around the edges of anticyclones into the ozone maximum in the amplified troughs. An idealized modeling experiment using the University of Wisconsin-Madison Nonhydrostatic Modeling System was performed to model strong outflow pulse from tropical convection. Together with model trajectory computations, the modeling study showed a strong anticyclonic response over the Indian Ocean and increased ozone transport into the amplified troughs in a perturbed wave pattern.