Improvements in processing and products

As a first processing step, individual marine reports for Release 1a were translated into an expanded version of the variable-length binary format for Long Marine Reports (LMRs) used for Release 1 (1854-1979). In contrast to 1980-91 interim processing, an expansion of the duplicate elimination algorithm for Release 1 was used to eliminate duplicate LMRs, including improved identification of exact matches of duplicate reports in time/space location and ID (e.g., ship call sign or buoy number). The resulting Release 1a output totals about 41 million LMRs for 1980-92 (3.8 gigabytes), of which hourly NDBC data make up 19%.

For Release 1a, a fixed-length version of the LMR format is also available, which contains all regularly observed weather elements and ID information, and has a flag set whenever feasible to indicate platform type (ship, drifting buoy, moored buoy, etc.). This represents an improvement over the Compressed Marine Report (CMR) format used for the interim products, which lacked some basic meteorological elements (e.g., wave fields) and ID information, and contained much less information regarding platform type.

The requirements of many COADS users are better met by 2-degree monthly summary products rather than individual observations. For Release 1, 14 statistics, such as the mean and the median of data falling within a given year-month- 2-degree box, were computed for each of 19 observed and derived variables, such as SST and heat-transport parameters. In contrast, although the interim products included all 19 variables, only the mean and the number of observations were recorded for each variable. For Release 1a, we have extended the full matrix of 19 variables x 14 statistics used for Release 1 through 1992. However, because the full matrix is voluminous even for the 13-year update period (~0.5 gigabyte), selected statistics are most commonly distributed in the form of "group" files (~50 megabytes/group) (Table 1).

Two separate sets of 2-degree monthly summaries were calculated for Release 1a: The "standard" set provides closest compatibility with Release 1, by retaining the original (1950-79) 3.5 sigma limits, and by restriction to ship data as nearly as practical. In contrast, the alternative set of "enhanced" statistics includes ships plus other in situ platforms, and employs wider 4.5 sigma limits to accommodate more extreme climate events. However, all NDBC C-MAN (near shore) data and non-3-hourly (i.e., not 0000, 0300, ..., 2100 UTC) moored buoy data, plus selected variables from other platform types, such as experimental wind observations from drifting buoys, were omitted from the enhanced statistics because of concerns about systematic data differences and over-sampling. Table 2 gives a summary of the composition of the resulting standard and enhanced statistics, as compared with that of the interim statistics.

Introduction | Data sources and corrections | Improvements in processing and products | Discussion | Future plans | Acknowledgements | References

U.S. National Oceanic and Atmospheric Administration hosts the icoads website privacy disclaimer
 Document maintained by icoads@noaa.gov
Updated: Nov 8, 2005 23:56:57 UTC
http://icoads.noaa.gov/coads1a_impr.html