Strategic Initiative Description

This schematic highlights the important processes coupling dynamics, chemistry and cloud microphysics in the UTLS region.

The overarching goal of this Initiative is to investigate a set of coupled processes in the UTLS region, all of which are known or suspected to affect atmospheric composition and climate. The Initiative synthesizes multi-scale observations from aircraft and satellites and seeks to improve representations of these in regional and global models.

Background

The interactions of dynamics, chemistry and microphysics in the UTLS region are a continuing international focus of theoretical, numerical, experimental, and observational studies. The upper troposphere and lower stratosphere region is an especially sensitive one in the coupled Earth system. Here water vapor, ozone, cirrus cloud particles and aerosols contribute strongly to the Earth’s radiative forcing. The abundance and variability of these constituents are controlled by both stratospheric circulation and the tropospheric weather systems. Adequate representation of this region in Earth system models requires an understanding of dynamical processes that occur over a wide range of temporal and spatial scales.

Chemical processing may involve multiple phases. Microphysical processing and sensitivity of cloud particle formation to aerosol composition and gaseous environment remain uncertain. Detrainment of anthropogenic gaseous and aerosol pollutants, including emissions from biomass burning, results from convective processes.

Inertia gravity waves may be generated by deep convection, dynamical adjustment processes near jet streams, and flow over complex terrain. The subsequent breaking of gravity waves within the UTLS or at higher altitudes can lead to eddy transport, greatly modulating the dynamical and chemical structure of the middle atmosphere.

Motivated by the significance of coupling in this region and the relative paucity of in situ data, the UTLS Strategic Initiative brings together process-directed observational studies from both airborne and space-based platforms. The understanding gained will enable the improvement of critical process representations in models from the microscale to the global scale.

Questions

START-08 Flight RF04: 28 April 2008 15:20z to 22:17z (Kenneth P. Bowman, Texas A&M University)

• How are the radiatively significant constituents, such as ozone, water vapor, cirrus cloud and aerosols, controlled by multi-scale tropospheric and stratospheric dynamical processes in the UTLS region? How will the distribution of these key constituents change in a changing climate?
• How are the chemical and microphysical processes in this region coupled? To what extent and under what circumstances are deep convective systems coupled to the boundary layer, transporting the products of human activity to the UTLS region?
• What are the required climate system model resolutions necessary to achieve adequate representation of coupled processes in the UTLS region? How do we best exploit the potential of advanced observing systems to produce a set of model diagnostics?

Special Role of the NCAR-NSF Gulfstream V, with Satellites and Models

Essential components for success include coordinated use of the NCAR-NSF Gulfstream V aircraft (GV) together with an advanced constellation of research and operational satellites. Measurements from these platforms, together with a suite of NCAR models from cloud-resolving to global scales, present the opportunity for this powerful arsenal to tackle frontier issues in the UTLS region. The GV is ideally suited for UTLS studies with its long endurance and high altitude capability. Within the time horizon of five years, the UTLS Initiative will have conducted two or more field campaigns involving the GV to identify the key signatures of tropospheric weather through chemical tracers.

Such field studies are directly motivated by and linked to the international community’s need to develop observations -based constraints for chemistry-climate models. The results of such field studies will be used, together with other available measurements, to benchmark the community models. As part of this effort, the Initiative has developed a plan to study the transport and mixing across the tropopause and the impact of mid-latitude deep convection on the UTLS chemical and aerosol composition.

UTLS Science Mission Links

START-05: Stratosphere-Troposphere Analyses of Regional Transport 2005

START-08: Stratosphere-Troposphere Analyses of Regional Transport 2008

T-REX: Terrain-induced Rotor EXperiment

DC3: Deep Convective Clouds & Chemistry experiment

Satellite Analysis

Modeling

Multidisciplinary Collaboration

NCAR’s UTLS Strategic Initiative is a multidisciplinary collaboration housed in TIIMES that includes participants from two NCAR Divisions: ACD - MMM and several organizations.

A few of the organizations involved in the UTLS initiative are: NOAA, Texas A&M, Harvard, University of Miami, Pennsylvania State University, Colorado State University, NASA-Langley, NASA-Goddard, New Mexico Institute of Mining & Technology,

Program Lead - Contact

Dr. Laura Pam
Email: liwen@ucar.edu
Phone: 303.497.1467
Mailing Address: NCAR, P.O. Box 3000, Boulder, CO USA 80307-3000

UTLS Steering Committee Members