These images compare the scale growth of a dynamic scalar (top, potential temperature) with a passive top-down scalar (bottom) in classical, horizontally homogeneous, dry convection after more than 50 large eddy turnover times, in a large eddy simulation in a domain whose size is comparable to that of a field campaign. While it is clear that the dominant horizontal scale for the passive tracer is about four times larger than for its dynamic counterpart, this rather surprising result is not well understood. These results highlight the importance of turbulence in the atmospheric and oceanic boundary layers, and they hint at the critical role these regions play in earth's weather and climate. (Images courtesy of Peter Sullivan, MMM.)

Geophysical Turbulence Program

The Geophysical Turbulence Program (GTP) has been in existence since almost the beginning of NCAR. It is by construction an interdisciplinary group that spans many divisions and laboratories at NCAR, with a few external affiliates. It encompasses research at NCAR on multi-scale nonlinear processes, with an array of applications in broad areas; it is also the outreach arm of this research. It supports NCAR's strategic priority of "Conducting research in computer science, applied mathematics, statistics, and numerical methods," "Creating a conceptual framework for integrating research across time and space scales to aid decision makers and enrich understanding of processes across scales," and "Engaging a broader and more diverse community."

In FY 2006, GTP has held 11 seminars and has hosted 7 long-term visitors (with an average stay of 4 weeks each). The topics covered in collaboration with NCAR staff range from wind-wave interactions, intermittency and modeling of turbulent flows, fast dynamos, convection, and entrainment in the Planetary Boundary Layer using Large Eddy Simulations, to the effect of air turbulence on rain development in warm clouds. Details are provided on the GTP web site.

Three workshops were held by GTP in FY 2006. One was in conjunction with the IMAGe's 2006 Theme-of-the-Year. The other two dealt with modeling turbulent flows. The first one had 36 participants investigating flows in the presence of magnetic fields and applications to the geo-dynamo. The second GTP workshop had 61 participants and dealt with turbulence and scalar transport in roughness sublayers e.g., near air-land and air-water interfaces. Represented at these two workshops were 34 universities, 9 national laboratories, and 38 countries.

In FY 2007, more visitors will be hosted, and more workshops will be held. The agenda will be decided at the GTP annual meeting in mid-October 2006.

GTP research is sponsored by the NSF cooperative agreement through UCAR, and partially by a variety of grants.