A22D-01 INVITED
Stratosphere-Troposphere Analyses of Regional Transport 2008 (START08) Experiment: Scientific Concept and Initial Results
A field campaign focused on transport in the Upper Troposphere and Lower Stratosphere (UTLS) was
conducted during April-June 2008 using the NSF/NCAR Gulfstream V research aircraft. In conjunction with
the HIAPER Pole-to-Pole Observations of Atmospheric Tracers (HIPPO) project, a total of 18 research flights
were conducted from Broomfield, Colorado. The experiment targeted key transport pathways in the
extratropical UTLS and the chemical structure of the tropopause by measuring a suite of chemical tracers
and microphysical parameters. In particular, the flights successfully investigated the intrusion of tropospheric
air into the stratosphere in association with the secondary tropopause. The aircraft observations are
complemented by satellite observations and model studies. One of the main objectives of the experiment is
to develop a better climatology of tracer-tracer correlations in the extratropical UTLS region. This will be
used to test and improve the representation of UTLS transport in coupled chemistry-climate models (CCMs).
The potential applications of these new results to process-oriented diagnoses of CCMs will be discussed.
http://www.acd.ucar.edu/start/
A22D-02 INVITED
Short-lived organic trace gases in the UT/LS: Results from recent field campaigns.
The chemistry of the upper troposphere/lower stratosphere can be impacted by delivery of reactive trace gases that are variable in composition and depend on source emissions and transport pathway and time. Because surface emissions include gases with a range of chemical lifetimes, and because different source emissions (e.g. marine boundary layer, anthropogenic emissions, biomass burning) can have different chemical signatures, the composition of the organic trace gases that are found in the UT/LS region have the potential to provide diagnostic information on air mass sources and transport time scales. Further, the role of short-lived organic halogen gases in the UT/LS has been highlighted as a major uncertainty for defining the reactive halogen budget and the chemical boundary conditions for the stratospheric chemistry that affects ozone depletion rates. Recent campaigns in the tropics (TC-4 and AVE missions) and in the extra-tropics (START08) have included the measurement of trace gases from whole air sampling and analysis on the NASA WB-57 or NSF Gulfstream V aircraft. Measurements of a range of halocarbons, hydrocarbons, organic nitrates, and sulfur species were made to examine the role of short-lived organic gases in the UT/LS. This presentation will highlight different aspects of these measurements that deal with transport pathways, transport rates, and halogen budgets.
A22D-03
Identification of transport pathways using modeled and observed CO-O3 correlation
To better understand and characterize the transport pathways of air masses from the Earth's surface in the extratropical tropopause region the START08 experiment was developed. Here we present a model study based on measurements conducted during two START08 flights. These flights are performed to study a tropospheric intrusion on April 18th, 2008 and a stratospheric intrusion on April 28th, 2008 over Central USA. To analyze the measurements we use the chemistry-transport model CLaMS. CLaMS is based on a unique Lagrangian formulation of the tracer transport. In CLaMS a deformation driven mixing scheme is implemented, which allows to simulated tracer correlations in the vicinity of the tropopause. CLaMS simulations was performed for April and May 2008. In CO-O3 correlations we found in both the measurements and the simulations that different mixing branches occurred depending on the origin of the air masses. We connect these branches to different transport pathways of the air masses across the tropopause depending on their location related to the jet streams.
A22D-04
Laminar Structures in Lower Stratospheric Middle Latitude Ozone as Observed by HIRDLS and Represented in a Chemistry Climate Model
During late winter and spring both vertical transport and quasi-horizontal isentropic transport from the lower tropical stratosphere contribute to ozone variability in the lower middle latitude stratosphere. Since ozone in this region is an important greenhouse gas, it is important that the mean and variability of the ozone distribution are realistically represented in chemistry climate models (CCMs). The High Resolution Dynamic Limb Sounder (HIRDLS), one of the instruments on NASA's Aura satellite, measures profiles of temperature and ozone with about 1 km vertical resolution. Profiles at middle latitudes are separated by less than a degree in latitude. HIRDLS commonly observes layered structures in the lower stratosphere that sometimes persist for a week or more. These layered structures are produced by horizontal transport that is sometimes reversible. The evolution of these layers also gives evidence of mixing. In other regions, HIRDLS profiles show ozone enhancement (i.e., ozone greater than the temporal mean) for a 3-4 km vertical range. Separate approaches are used to quantify the importance of these processes to variability in the lower stratosphere. The structures with broad vertical range are identified using the covariance between levels. The frequency of vertical structures is computed over the winter and spring seasons, and results are compared with a similar analysis applied to output from simulations using the NASA Goddard CCM. The contributions of the layered structures to variability and the importance of mixing are examined by computing the distributions of ozone values on potential temperature surfaces for specified intervals of potential vorticity. Ozone is often correlated with potential vorticity, and the aim of this analysis is to explore the mixing processes that are observed by HIRDLS to understand their importance to the breakdown in the pv-ozone correlation. The behavior of the pv-ozone relationship as observed by HIRDLS can be contrasted with that derived from a parallel analysis of the output of the CCM.
A22D-05
Quantifying transport into the lowermost stratosphere using simultaneous in-situ measurements of SF6 and CO2
Simultaneous in-situ measurements of CO2 and SF6 have been performed in the extratropical UTLS for the time period 2000 - 2003 during the SPURT (SPURenstofftransport in der Tropopausenregion) project. SPURT delivered for the first time a detailed multi-year UTLS data record of both tracers for every season over a large range of latitudes. The seasonal cycle of CO2 in the troposphere propagates through the tropopause into the extratropical lower stratosphere (LS), while SF6 can be regarded as a seasonally undisturbed reference tracer. These different stratospheric input functions of both tracers allow characterising trace gas transport into the extratropical LS. We will present an approach to calculate a trace gas budget for the extratropical LS based on simultaneous airborne measurements of SF6 and CO2. Our approach is based on the general assumption that transport into the extratropical LS can be described by bimodal age spectra (e.g. Andrews et al., 2001). This strategy offers a unique new aspect opposite to former trace gas budgets, e.g. Ray et al. (1999), Pan et al. (2000) and Hoor et al. (2004). Beside the fractions for the different transport pathways into the extratropical LS, we are able to deduce the associated mean transport time for the tropospheric fraction. The results of this mass balance study will be shown and we will discuss the implications on troposphere-to- stratosphere transport, especially in the light of applying this method for model evaluation.
A22D-06
Observations of Non-Methane Hydrocarbons Over India During the Asian Summer Monsoon Period: Results from CARIBIC
The CARIBIC project (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container, www.caribic-atmospheric.com) involves the monthly deployment of an instrument container equipped to make atmospheric measurements from onboard a long-range commercial airliner. Since December 2004, flights for the second phase of CARIBIC have been aboard a Lufthansa Airbus A340-600 traveling between Frankfurt, Germany and destinations in Asia, North America and South America. The instrument package housed in the container (1.5 ton) is fully automated and during each monthly set of flights carries out a variety of real-time trace gas and aerosol measurements, and also collects 28 air samples, which are analyzed upon return to the laboratory. Routine measurements made from the sampling flasks include non-methane hydrocarbon (NMHC) analysis, and these measurements provide the basis for the data presented here. Between April and September of 2008, the container was deployed monthly on two sequential roundtrip flights between Frankfurt and Chennai, India. To achieve greater resolution, air samples were collected only on the first of the roundtrip flights, with 14 samples collected on the flight to Chennai and 14 collected on the return. These flights provided the opportunity to study the composition of the upper troposphere in this region during the Asian summer monsoon period (typically June-September), which is characterized by anticyclonic circulation in the upper troposphere coupled with deep convection. Samples collected during the monsoon period exhibit elevated levels of NMHCs relative to samples collected outside of the monsoon period, with enhancements in ethyne and benzene being more substantial than enhancements in the alkanes. Enhanced mixing ratios are observed between 15N and 40N, and correspond to enhancements in other trace gases, namely methane and CO. Ethyne in particular is strongly correlated with both methane and CO in this region; while CO and ethyne share a common, combustion, source, methane and ethyne do not, and this relationship indicates convection of a well-mixed air mass that is strongly and recently influenced by both agricultural and anthropogenic/urban sources. Trends in and relationships between NMHCs during the monsoon period will be discussed here, as well as their relationships to other trace gases.
A22D-07
Cross-tropopause transport by deep convective storms : model simulations and satellite/aircraft observations
More and more evidences have shown that deep convective storms play an important role in the transport of water vapor from the troposphere into the stratosphere. Such transport has been observed to occur not only in midlatitudes but in lower latitudes as well. Observational evidences include elongated storm overshooting top cirrus plumes in the presence of strong upper level wind shear and pancake clouds above storm clouds in weak shear environment as observed in satellite visible and infrared images. In addition, jumping cirrus phenomenon observed by aircraft and ground based photography corroborates with satellite observations to further confirm the deep convective transport. Simulations of deep convective storms using a cloud resolving model provide more details on the physics and dynamics of this mechanism and also suggest potential techniques of using satellite data to estimate the deep convective transport. All these will be reviewed and summarized in this paper.
A22D-08
Rapid UTLS Lofting of Forest Fire Smoke by Synoptic Scale Cyclones in Eastern Asia
The boreal fire season started unusually early in 2008. As early as March, fires in eastern Russia were abundant. In mid-March and again in April synoptic scale storms passing through the flaming zone excited burning and lofted emissions to the upper troposphere on the timescale of hours. Subsequently the smoke could be detected in the upper troposphere and even the lowermost stratosphere as it was transported intercontinentally to North American midlatitudes and to the high Arctic. A suite of satellite measurements is employed to characterize the initial lofting, rapid spread in the UTLS, and eventual transport across the tropopause. NASA A-Train instruments are brought together to evaluate the evolving composition of the cloud/aerosol mixture as the emissions are circulated within the synoptic-scale cyclone and exhausted at mid and high tropospheric altitudes. The smoke tracer is used as a diagnostic of storm dynamics and transport efficiency.