Description of Level 3 Product v1.2 

November 4, 2013

Monthly gridded data product for the upper troposphere and lower stratosphere (UTLS) is posted 
on JPL-based GENESIS Web-site http://genesis.jpl.nasa.gov. It includes geopotential height and 
temperature at 17 pressure levels from 10 to 275 hPa  (data up to 1000 hPa pressure level are 
available but not routinely delivered): 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 
225, 250, 275 hPa.  At each pressure level data are binned and interpolated on 5 x 5 degree grid 
with the maximum spherical harmonics number of 14.  The fitted spherical harmonic coefficients 
are available upon request.

The Level 3 product covers a decade of uniformly processed RO data, from April 2001 through 
July 2008 using CHAMP ROs, and from June 2006 through December 2011 using COSMIC 
ROs. The use of Bayesian interpolation techniques and global averaging minimized 
sampling/mapping errors in the dataset [Leroy et al., 2012].  The gridded data can be utilized 
effectively for study of climate variabilities and trends in the UTLS. 

Gridded data are posted as monthly NetCDF3.0 files named as 
spacecraft_yyyy_mm_2Dmean.nc    and spacecraft_yyyy_mm_zonalmean.nc for global and 
zonal means, correspondingly. Here, “yyyy” stands for year and “mm” for month. 
The files contain:  
•	Latitude range
•	Longitude range
•	Pressure levels 
•	monthly 2D mean temperature map (in K, an array of latitude, longitude, pressure 
level)  
•	monthly 2D mean temperature interpolation error map (in K, an array of latitude, 
longitude, pressure level)  
•	monthly zonal mean temperature (in K, an array of latitude and pressure level)  
•	monthly zonal mean temperature interpolation error (in K, an array of latitude and 
pressure level)  
•	monthly 2D mean geopotential height map (in km, an array of latitude, longitude, 
pressure level)
•	monthly 2D mean geopotential height interpolation error map (in km, an array of 
latitude, longitude, pressure level) 
•	monthly zonal mean geopotential height (in km, an array of latitude and pressure 
level)
•	monthly zonal mean geopotential height interpolation error  (in km, an array of 
latitude and pressure level) 
•	 number of data points at each pressure level (RO statistics) 

Additionally, files cosmic_yyyy_mm_geostrophic_wind_mean.nc contain monthly mean 
geostrophic winds estimated from geopotential height based on COSMIC ROs: 
•	Latitude range
•	Longitude range
•	Pressure levels 
•	Eastward component of geostrophic wind, monthly means (in m/sec, an array of 
latitude, longitude, pressure level)  
•	Northward component of geostrophic wind, monthly means (in m/sec, an array of 
latitude, longitude, pressure level)  

References: 
    Leroy, S., C. Ao, O.P. Verkhoglyadova (2012), Mapping GPS Radio Occultation Data by 
Bayesian Interpolation, J. Atmosph. Oceanic Technology, 29, 1062, doi: 10.1175/JTECH-D-11-
00179.1. 

Contact: Chi Ao (Chi.O.Ao@jpl.nasa.gov) and Olga Verkhoglyadova (Olga.Verkhoglyadova@jpl.nasa.gov)