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GLERL 2001 Milestone Reports
GOAL: IMPLEMENT SEASONAL TO INTERANNUAL CLIMATE FORECASTS
OBJECTIVE 3: Conduct Research for Improved Climate Predictions.
PM: Improve understanding of atmospheric, oceanic, land surface and cryospheric processes that contribute to seasonal-to-interannual climate variability, as measured by peer-reviewed publications form NOAA-supported research.
Milestone: Complete a statistical analysis of Great Lakes ice cover for a 23 winter base period (1973-1995).
Scientist: R. A. Assel
Purpose: The objective of this activity is to update the first computerized statistical analysis of Great Lakes ice cover (Assel et al 1983). The improved statistical climatology is needed for studies of climate variation and change, for marine engineering design, and for improved ice models and operational ice forecasts. The milestone was expanded to cover the period from 1973-2000, a 28 winter period. These data also have applications in lake aquatic system and lake toxic deposition studies and in the development of linked atmospheric, lake hydrodynamic, and lake thermodynamic models.
Efforts: The original data intended for this analysis, as described in FY 2000 milestone were augmented by digital ice chart data for 5 additional winters (1996, 1997, 1998, 1999, 2000) that were obtained from the National Ice Center. These data were converted to GLERL's ice codes and format and quality controlled as described in Norton et al (2000). These data were used to expand the base period of the statistical analysis to 28 winters. The addition of the 1998 winter was particularly significant because that winter was the mildest over the period of record and set new lows for annual maximum ice cover extent (Assel et al, 2000).
Weekly spatial patterns of maximum, 3rd quartile, median, 1st quartile, and minimum ice cover concentration over the 28 winter base period (1973 to 2000) were analyzed and portrayed as ice charts (Figure 1). The spatial pattern of first and last observed ice, and of ice duration for: 1) each winter from 1973 to 2000 and 2) statistics over the 28 winters were also analyzed and portrayed as ice charts (Figure 2). A daily series of total ice concentration grids (2.5 km grid cell resolution) was developed for each winter season by interpolation between dates with observations. These data were used to make computer animations that portray the spatial and temporal characteristics of total ice concentration for each winter (Assel and Norton, 2001). These data were also used to calculate lake averages of total ice concentration for each lake each winter season (Figure 3) and statistics (maximum, 3rd quartile, median, 1st quartile, and minimum) over the 28 winters. This work was accomplished by developing computer programs in Fortran and Interactive Data Language.
Figure 1. Example ice chart for the median ice cover for the years 1973-2000 for the period February 1-7.
Figure 2. Example ice chart for the duration of ice cover for the year 1973.
Figure 3. Average Lake Erie ice cover for the winter of 1973 by month.
Customers: The updated climatology will be made available to the National Ice Center and Canadian Ice Service who have the responsibility of making long-range ice cover outlooks and forecasts for the Great Lakes each winter. Other customers include other government agencies, academia, and private industry with research, educational, operational, and engineering activities in which Great Lakes ice cover is an important consideration.
Significance: Updated statistics on Great Lakes ice cover will provide the National Ice Center and Canadian Ice Service with improved (and computer accessible) climatological information for making operational long-range ice cover outlooks and forecasts. The ice cover statistical analysis is an index of the regional winter climate and climate variation of the Great Lakes during the last quarter of the 20th century. These data will be extremely useful in the analysis of future Great Lakes winter climate and climate change.
Success: Statistical analysis of GLERL's updated 28 winter ice cover data base has been made for selected statistics and summarized in graphical format (ice charts and x-y plots of lake averaged ice concentration vs. date), computer animations, and computer ASCII files. What remains to be done is to assemble the results of the analysis into a coherent document and publish it.
Next Steps: Develop a Graphic User Interface (GUI) to facilitate access and use of these data as an electronic atlas. Develop a second generation GUI for exploring these data at time and spatial scales and for statistics not given in the electronic atlas. Explore development of statistical models of ice cover concentration (possibly by using antecedent ice cover and hydro-meteorological data) and the feasibility of applying such models for development of improved ice forecasts at various time scales.
References
Assel, R.A. and D. C. Norton. 2001. Visualization of Great Lakes ice cycles.
2001. EOS, Transactions, American Geophysical Union, Vol. 82, No. 7 February
13, 2001.
Assel, R.A. et al., 2000. Laurentian Great Lakes ice and weather conditions for the 1998 El Niño winter. Bull. Amer. Meteo. Soc., 81 (4) : 703-717.
Assel, R.A., F.H. Quinn, G.A. Leshkevich, and S.J. Bolsenga, 1983. Great Lakes ice atlas. NOAA Atlas No. 4. Great Lakes Environmental Research Lab., Ann Arbor, MI. The digital data from this atlas as well as the data base upon which is based is available on the internet. (NSIDC web site)
Norton, D.C, et al. 2000. Great Lakes ice cover data rescue project. 2000 NOAA TM ERL-GLERL-117, Great Lakes Environmental Research Laboratory, Ann Arbor, MI.
Last updated: 2004-04-02 mbl