Scientific Theme: Advanced Modeling and Observing Systems

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Complementary Research: Faculty Fellows Research The Dynamics of the Residual Layer Determined from High-Resolution In Situ Observations during CASES-99 Ben Balsley We are currently examining a number of new results derived from high-resolution in situ studies of the residual layer (RL) obtained during the CASES lower atmospheric campaign in eastern Kansas in October, 1999. These studies typically used data gathered by the CIRES-developed Tethered Lifting System, which consists of a state-of-the-art kite or an aerodynamic balloon that has high-resolution instruments suspended well below from the tether. The RL lies between the stable boundary layer (the lowest region of the nighttime atmosphere that is tightly coupled to the Earth‘s surface) and the steep temperature gradient that defines the bottom of the free atmosphere. Although the RL is a poorly studied region owing to its inaccessibility, it is important for studying the turbulent transport into the free atmosphere of pollutants generated at ground levels. Our results show that the RL is not—as has been generally portrayed in the literature—a passive, quiescent remnant of the previous afternoon‘s convective boundary layer. Rather it is a complex, rapidly changing, and dynamic arena harboring regions of intense turbulent variations with extremely sharp gradients. Our current studies show that RL turbulence: (1) is always present, (2) can exceed stable boundary turbulence levels by an order of magnitude, (3) can range in intensity over more than three orders of magnitude, (4) is generated locally on scales of a few tens of meters or less by velocity shears, and (5) can be entrained into the underlying stable boundary layer, particularly when the RL turbulence is intense and the stratification between the RL and stable boundary layer is relatively weak. The figure at right shows a set of eight ascents and descents, plus a curve of the median value of all eight flights, which portrays the percentage of RL heights having critical Richardson number values (Ri ≤ 0.25) as a function of the analyzed vertical-scale size. Both axes are plotted using logarithmic scales in order to show details over a wide range of scale sizes and percentages. The fundamental conclusion that can be drawn from this result is that, while there are reasonable variations in the flight-to-flight results as shown by the various curves, the RL is clearly dynamically unstable only on scales smaller than a few tens of meters. The significance of this result is that the current computer models employed to examine turbulence generation and the concomitant dynamics in the stable boundary layer do not have sufficient resolution to examine such small-scale instabilities. The causal mechanisms for the generation of these small-scale instabilities is currently under study. A list of likely mechanisms could reasonably include turbulence generation by atmospheric gravity waves, frontal passages, and a variety of local orographic features. 104
Complementary Research: Faculty Fellows Research Twentieth Century Sea Ice in the Eurasian Arctic from Russian Data Sources Roger G. Barry Funding: NASA: Cryospheric Sciences The primary objective of this work is to fill gaps in the Arctic sea ice data record by extending the record back and forward in time. A secondary objective is to provide summary statistics, and to assess the evidence for climate change in the Russian Arctic over the period 1930s-2005. The 1930-40s saw significant high latitude warming and therefore it is important to document accompanying changes in ice conditions for comparison with those of summers since 1990. Two significant sources of historical sea ice charting data in digital form are the WMO Global Digital Sea Ice Data Bank and the Environmental Working Group Sea Ice Atlas. The sea ice atlas includes Arctic-wide U.S. National Ice Center seven-day sea ice charts, 1972-1994, and Russian Arctic ten-day sea ice charts, 1950-1992. Sea ice charts for 1933–49 based on aerial reconnaissance, and recent data for 1993-2005, have been digitized at the Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia, and can be viewed using an interactive browser at http://www.aari.nw.ru/gdsidb/sea_ice/real_sigrid/view.html We have acquired digitized historical ice charts of the Eurasian Arctic from the AARI for the periods 1933-1992 and 1997-2006. We also have ice index data for the periods 1924-1933 and 1993-1996, creating an observational ice record that spans over 80 years. From ice chart data, we have located the ice edge where possible in every chart and calculated seasonal ice extent anomalies for the marginal seas of the eastern Arctic. These results (Figure, left) indicate that although there was also a retreat in autumn (annual minimum) sea ice extent in the early part of the 20 th century, there was no apparent retreat in springtime (annual maximum). In recent years however, there has been a year-round retreat of eastern Arctic sea ice extent. 105 We are currently examining historical meteorological station data and atmospheric indices (such as the AO) to seek correlations between Arctic climate and the observed variability in sea ice. We are also comparing the AARI ice chart dataset with other digital sea ice data with the aim of producing an optimized dataset of Arctic sea ice.
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COOPERATIVE INSTITUTE FOR RESEARCH
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Table of Contents Letter from the D
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Executive Summary and Research High
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Chemical Sciences Division (CSD) CI
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CIRES in 2006-2007: Administration
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CIRES in 2006-2007: Creating a Dyna
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GSD01: Numerical Weather Prediction
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Complementary Research: CIRES Fello
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CIRES’ Leadership Konrad Steffen:
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Appendices: Governance and Manageme
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Appendices: Publications Beaver, M.
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Appendices: Publications Maus, S.,
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Appendices: Publications Miller, J.
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Appendices: Honors and Awards Honor
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Scientific Theme: Advanced Modeling and Observing Systems

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