Introduction

wgrib2 can write grib files by either copying an existing packed grib message (-grib) or by taking floating point values and packing them into a new grib message. (For example, -grib_out, -small_grib, -ij_small_grib, and -wind_speed). For the latter, one has a choice of packing methods. Generally methods that are faster methods create larger files and slower methods make smaller files. For fields with no undefined values, the jpeg2000 produces the smallest files. With bitmaps, one of the complex packings is usually the best (of the supported packing). Complex3 is often the best trade off between speed and compression for smooth fields. For other fields complex1 is often the best trade off between speed and compression. The (-set_grib_type) option controls the packing method.

Usage

-set_grib_type X   X=ieee,simple,complex1,complex2,complex3,jpeg,same

ieee = data is ieee format (4 bytes per data point)
simple = no compression, packed scaled integers
complex1 = complex packing
complex2 = complex packing, pack increments (deltas)
complex3 = complex packing, pack increments after linear extrapolation
jpeg = jpeg2000 compression
same = try to keep same packing type as input
       if input is in an unsupported output packing, complex1 is used

note c1,c2,c3 are the same as complex1,complex2,complex3

Example

$ wgrib2 in.grb -set_grib_type complex3 -grib_out out.grb 

See also: -grib_out,