Release notes for GRACE L-2 calibration products - version JPL RL04 -------------------------------------------------------------------------- Note date 2007-02-20 1) The following 46 monthly GRACE gravity fields are available: GSM-2_2003001-2003031_0027_JPLEM_0000_0004 2003 JAN GSM-2_2003032-2003059_0022_JPLEM_0000_0004 2003 FEB GSM-2_2003060-2003090_0026_JPLEM_0000_0004 2003 MAR GSM-2_2003091-2003120_0028_JPLEM_0000_0004 2003 APR GSM-2_2003121-2003141_0021_JPLEM_0000_0004 2003 MAY GSM-2_2003182-2003212_0030_JPLEM_0000_0004 2003 JUL GSM-2_2003213-2003243_0027_JPLEM_0000_0004 2003 AUG GSM-2_2003244-2003273_0029_JPLEM_0000_0004 2003 SEP GSM-2_2003274-2003304_0029_JPLEM_0000_0004 2003 OCT GSM-2_2003305-2003334_0027_JPLEM_0000_0004 2003 NOV GSM-2_2003335-2003365_0030_JPLEM_0000_0004 2003 DEC GSM-2_2004001-2004013_0013_JPLEM_0000_0004 2004 JAN GSM-2_2004035-2004060_0026_JPLEM_0000_0004 2004 FEB GSM-2_2004061-2004091_0030_JPLEM_0000_0004 2004 MAR GSM-2_2004092-2004121_0027_JPLEM_0000_0004 2004 APR GSM-2_2004122-2004152_0030_JPLEM_0000_0004 2004 MAY GSM-2_2004153-2004182_0030_JPLEM_0000_0004 2004 JUN GSM-2_2004183-2004213_0031_JPLEM_0000_0004 2004 JUL (see 1.f) GSM-2_2004214-2004244_0030_JPLEM_0000_0004 2004 AUG (see 1.f) GSM-2_2004245-2004274_0030_JPLEM_0000_0004 2004 SEP (see 1.f) GSM-2_2004275-2004305_0031_JPLEM_0000_0004 2004 OCT (see 1.f) GSM-2_2004306-2004335_0030_JPLEM_0000_0004 2004 NOV GSM-2_2004336-2004366_0028_JPLEM_0000_0004 2004 DEC GSM-2_2005001-2005031_0031_JPLEM_0000_0004 2005 JAN GSM-2_2005032-2005059_0027_JPLEM_0000_0004 2005 FEB GSM-2_2005060-2005090_0027_JPLEM_0000_0004 2005 MAR GSM-2_2005091-2005120_0030_JPLEM_0000_0004 2005 APR GSM-2_2005121-2005151_0031_JPLEM_0000_0004 2005 MAY GSM-2_2005152-2005181_0029_JPLEM_0000_0004 2005 JUN GSM-2_2005182-2005212_0031_JPLEM_0000_0004 2005 JUL GSM-2_2005213-2005243_0031_JPLEM_0000_0004 2005 AUG GSM-2_2005244-2005273_0030_JPLEM_0000_0004 2005 SEP GSM-2_2005274-2005304_0031_JPLEM_0000_0004 2005 OCT GSM-2_2005305-2005334_0030_JPLEM_0000_0004 2005 NOV GSM-2_2005335-2005365_0027_JPLEM_0000_0004 2005 DEC GSM-2_2006001-2006031_0031_JPLEM_0000_0004 2006 JAN GSM-2_2006032-2006059_0027_JPLEM_0000_0004 2006 FEB GSM-2_2006060-2006090_0030_JPLEM_0000_0004 2006 MAR GSM-2_2006091-2006120_0030_JPLEM_0000_0004 2006 APR GSM-2_2006121-2006151_0031_JPLEM_0000_0004 2006 MAY GSM-2_2006152-2006181_0027_JPLEM_0000_0004 2006 JUN GSM-2_2006182-2006212_0031_JPLEM_0000_0004 2006 JUL GSM-2_2006213-2006243_0031_JPLEM_0000_0004 2006 AUG GSM-2_2006244-2006273_0030_JPLEM_0000_0004 2006 SEP GSM-2_2006274-2006304_0031_JPLEM_0000_0004 2006 OCT GSM-2_2006305-2006334_0030_JPLEM_0000_0004 2006 NOV REMARKS: 1.a - Every month, an unconstrained 120x120 field is provided. 1.b - The standard deviations of the harmonics included in the GSM-2* products represent ONLY formal (NOT calibrated) errors of the estimate. 1.c - These filenames end with the string "_0000_0004", denoting the Release 04 Level-2 products. 1.d - Due to the increasing errors in the monthly fields at higher degrees, users are cautioned against using spherical harmonic coefficients past approximately degree 100 in the monthly fields. 1.e - The principal difference of these products relative to the Release-01 is a significant upgrade to the background gravity models. These models upgrades are described in the JPL Level-2 Processing Standards Document - version 4.0. Changes to the parametrization are also described in that document. 1.f - A solution for June 2003 is missing due to the absence of GRACE-2 accelerometer data. Solutions for July 2004 through October 2004 are missing as unconstrained solutions are very unstable during the 61/4 repeat passage of the GRACE ground tracks. 1.g - The reference epoch of the rate of low degree and order coefficients for a secular trend in the processing of the GRACE data (i.e. C20, C30, C40, and C21/S21) is J2000.0. The details of background models for GRACE data processing can be found in the "JPL L2 Processing Standards Document for Level-2 Product Release 04". 2) For each month six product files are available. For example, the available products for January 2005 are: GSM-2_2005001-2005031_0031_JPLEM_0000_0004 GSM-2_2005001-2005031_0031_JPLEM_0000_0004.README GAA-2_2005001-2005031_0031_JPLEM_0000_0004 GAB-2_2005001-2005031_0031_JPLEM_0000_0004 GAC-2_2005001-2005031_0031_JPLEM_0000_0004 GAD-2_2005001-2005031_0031_JPLEM_0000_0004 REMARKS: 2.a - The monthly GAA, GAB, GAC, and GAD files are the monthly averaged harmonics from AOD (RL04). 2.b - The zero-th and first degree terms in GAA, GAB, GAC, and GAD products have not been applied in the level-2 gravity recovery process. 2.c - The averaging of GAA, GAB, GAC, and GAD are carried out over a whole number of days, regardless of whether full or partial day's data were used in creating the GRACE monthly solution. 2.d - The header information in these files contain slightly different values of GM (Earth gravitational parameter) and Ae (Earth equatorial radius) - when compared to the values in the headers of the geopotential product files GSM*. All analysis has been done with the values using the GM and AE values in the headers of the GSM* files.