ERA-40 Surface Analysis and Forecast Fields on T106 Gaussian Grid

DS127.0 contains 46 surface and single-level analysis variables and 27 forecast variables from the ERA-40 reanalysis, transformed to a 320 by 160 regular Gaussian grid. NCAR's Data Support Section implemented this dataset in late 2004 and early 2005 to archive selected segments of ERA-40 on standard grids. The data consists of 6-hourly fields, with forecast variables valid 6 hours after initialization.

Use Cases

• Analyze 10-meter wind fields treated as scalars for surface wind pattern studies.
• Examine sea surface temperature and sea ice fields, which contain missing values over land masks.
• Study accumulated forecast variables like evaporation, dividing values by 21600 seconds to obtain instantaneous rates.
• Compare vegetation indices and cloud cover fields, which appear as integers plus a fractional part due to interpolation from the original T106 version.
• Investigate three pairs of stress variables treated as scalars due to a lack of spectral precursors in the transformation process.

Strengths

• Includes 73 distinct 6-hourly variables (46 analysis, 27 forecast) for atmospheric analysis.
• Data is transformed to a standardized 320 by 160 regular Gaussian grid (T106 resolution) for consistency.
• Transformation employs established routines from the ECMWF EMOS library.

Limitations

• The dataset is temporally stale, with a last update recorded in 2002, preceding its implementation period.
• Spatial coverage may be biased by the Gaussian grid transformation and the masking of land points in ocean fields.
• The ERA-40 reanalysis has been superseded by higher-resolution products like ERA-Interim, which starts in 1989.

Provenance

Source

European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-40 reanalysis, processed by NCAR Data Support Section.

Collection Method

Variables transformed from a reduced N80 Gaussian grid to a 320x160 regular Gaussian grid using ECMWF EMOS library routines.

Time Range

Covers the period of the ERA-40 reanalysis (1957-2002), with dataset implementation in 2004-2005.

Freshness

Last updated 2002-08-31; static historical archive.

Geography

Global coverage on a Gaussian grid.