Urgent! CFSR Pressure Data

[冯曦]

Hi, Dear Hycom committee,

I am a user of the dataSets provided by HYCOM.

Recently I am using documented CFSR data from your website. However, I got confused about the surface air pressure data. Basically, they are all positive and ranges with 100 hpa. It is not in the range of the normal air pressure (800-1100). So I am wondering what does this pressure represents? If it is a deviation from a standard, could u please provide us the convert equation?

PS: the link I am refering to is:

https://hycom.org/dataserver/ncep-cfsv2 

Many Thanks and expect your reply.

Xi
College of Harbour, Coastal and Offshore Engineering 

Hohai University

Nanjing, China, 210036

[Michael McDonald]

Do you see the "scale_factor" and "add_offset" in the NetCDF metadata for the "airprs" variable?

e.g., see here,

http://tds.hycom.org/thredds/dodsC/datasets/force/ncep_cfsv2/netcdf/cfsv2-sec_2011_01hr_sfcprs.nc.html

coordinates: Date

time_average_bounds: 0.0, 0.0

long_name:  surface pressure

standard_name: surface_air_pressure

units: hPa

scale_factor: 0.00390625

add_offset: -31.413218

Recently I am using documented CFSR data from your website. However, I got confused about the surface air pressure data. Basically, they are all positive and ranges with 100 hpa. It is not in the range of the normal air pressure (800-1100). So I am wondering what does this pressure represents? If it is a deviation from a standard, could u please provide us the convert equation?

PS: the link I am refering to is:

https://hycom.org/dataserver/ncep-cfsv2 

 

--

Michael McDonald
HYCOM.org Administrator

[alan.wa...@hycom.org]

Add 1000 hPa.

When we use it in HYCOM, we multiply by 100 to get Pa and then add 1.e5 Pa if we need the total (usually we are calculating a gradient).

From blkdat.input:

1.e5      'prsbas' = msl pressure is input field + prsbas (Pa)
   1      'mslprf' = msl pressure forcing flag            (0=F,1=T)


This information should have been in the netCDF file.

Alan.