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Science Briefing

-----The University NAVSTAR Consortium (UNAVCO) will be working with the Geodetic Survey Institute of Japan (GSI) on analysis of GPS data for earthquake studies. GSI was operating a network of 200 continuous, high-accuracy Global Positioning Satellite (GPS) stations, distributed across Japan, at the time of the catastrophic Kobe earthquake on 16 January. Five stations receiving signals were operating within 100 kilometers of the Kobe epicenter. GSI's preliminary estimates for displacements of these stations at the time of the earthquake are as large as 8 centimeters, with uncertainties of several centimeters.

UNAVCO's Chris Rocken and James Johnson are soon to begin collaboration with Japanese colleagues at the GSI, analyzing data from a dense GPS network designed for earthquake studies in the Tokyo metropolitan area. GPS deformation results from the Kobe area will be inverted by Japanese geophysicists to define the size and orientation of the slip patch (the earthquake's below-ground source region). The goal of the GSI network in Japan and other GPS networks is to provide precise sensing of crustal deformation for earthquake studies today that may lead to forecasting and hazard reduction in the future. Improvements planned for the coming year in the Japanese network include a new operations center with flat-panel displays of all station positions and automated warnings generated by any station movements.

High-accuracy orbits calculated by the International GPS Service (IGS), using the IGS network of more than 50 worldwide GPS tracking stations, should reduce the uncertainty of displacement estimates to the millimeter level. Reliable forecasts have not yet been demonstrated, but if achieved, they would allow warnings to be issued and trains, gas, water, and power to be shut down. Similar GPS networks are being put in place along the San Andreas Fault in California and in other earthquake zones.

-----Can global climate models depict the initiation of ice sheets realistically? CGD's Starley Thompson is evaluating that question with the help of NCAR's GENESIS model (Global Environmental and Ecological Simulation of Interactive Systems). The results were presented last month in Dallas, Texas, at the American Meteorological Society's annual meeting. According to Starley, much of the paleoclimatic modeling of ice sheets to date has focused on the Laurentide sheet, which spread across much of northern North America during the last glacial period, peaking at 21,000 years ago. The biggest problem in modeling ice sheet creation is spatial resolution: the sheets form through the interaction of relatively small snowfield and topographic variations.

Using version 2.0 of GENESIS, Starley ran simulations representative of the end of the last interglacial at a horizontal resolution of 3.8 by 3.8 degrees with 18 vertical levels. The land surface was resolved on a tighter 2 by 2-degree grid to allow for important finer-scale features such as highlands on Baffin Island to be included. Preliminary results show that the model forms large permanent snowfields on Baffin Island when forced with solar radiation comparable to that of 116,000 years ago, when the Laurentide ice sheet started to form.

Along with ice sheet initiation, Starley evaluated the surface mass balance of the large Laurentide ice sheet as well as the present-day ice caps of Greenland and Antarctica. While the model did a good job for Antarctica and even produced a reasonable result for the smaller Greenland ice cap, the Laurentide results are problematic. GENESIS shows substantial wasting away of the large ice sheet, which is inconsistent with the assumption that the Laurentide ice sheet was in equilibrium at its maximum size. Either the reconstructed ice sheet size, the climate model simulation, or the assumption of equilibrium is incorrect. The results of these simulations have pointed to areas of needed model improvements, particularly for simulating the ice sheet margins where steep ice height gradients make it difficult to model the transition from accumulation to ablation.

-----Two NCAR senior scientists, Peggy LeMone (MMM) and Kevin Trenberth (CGD), became Fellows of the American Association for the Advancement of Science (AAAS) at the group's annual meeting in Atlanta this month. Individuals are elevated to the rank of AAAS Fellow "because of their efforts toward advancing science or fostering applications that are deemed scientifically or socially distinguished." AAAS named 297 Fellows this year. Founded in 1848, AAAS represents the world's largest federation of scientists and has more than 140,000 individual members. The first AAAS Fellows were named in 1874.

Photo of Peggy LeMone Peggy LeMone. (Photo by Bob Bumpas.)

Peggy specializes in studies of the atmospheric boundary layer, clouds, mesoscale convective systems, and the interactions among them. She has flown through or directed research aircraft through or around squall lines and hurricanes in and near the United States. Other observational flights focused on clouds ranging from fair weather cumulus to mesoscale convective systems in field programs west of Africa, around Taiwan, and north of Australia and New Zealand. Peggy also has championed the roles of women and minorities in the atmospheric sciences, co-organizing two national surveys to document their accomplishments. During her 23 years at NCAR, Peggy has revised the weather portions of earth-science texts for the publisher D. C. Heath and authored or revised several articles in the World Book Encyclopedia.

Photo of Kevin Trenberth Kevin Trenberth. (Photo by Bob Bumpas.)

Trenberth, a native of New Zealand, is deputy director of CGD and heads its Climate Analysis Section. Since joining NCAR in 1984, he has focused on meteorological phenomena influencing global weather and climate, particularly global climate change and interactions between the atmosphere and ocean, as in El Nio. Trenberth has edited the journal Monthly Weather Review and a 788-page book, Climate System Modeling (Cambridge University Press, 1992). Currently on the Council of the AAAS, Kevin is a lead author of the 1995 Scientific Assessment for the Intergovernmental Panel on Climate Change and serves on many other national and international committees. Recognizing the importance of explaining how short-term severe weather anomalies may be the product of long-term climate fluctuations, Kevin has interpreted current weather extremes for broader audiences through plenary sessions at the AAAS, interviews for National Public Radio, and national and local newscasts.

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Edited by Bob Henson, bhenson@ucar.edu
Last revised: Wed Mar 29 12:41:55 MST 2000