1.  Revised Range Reference Atmosphere (RRA) data -

In 2006, the Air Force Combat Climatology Center (AFCCC) developed a set of revised Range Reference Atmosphere (RRA) data including several new sites.  Earth GRAM-07 has the option of using either the 2006 revised RRA data, or the earlier (1983) RRA data, as a replacement for conventional Earth GRAM climatology.             

2.  Optional auxiliary profile input -

In addition to RRA options, an "auxiliary profile" feature has been implemented.  This allows the user to input a data profile of pressure, density, temperature, and/or winds versus altitude, that GRAM will use in place of conventional climatology values. 

3.  Perturbation model revisions -

Several changes/additions have been made in the perturbation model for Earth GRAM-07.  These include:

a)   A new feature allowing the option to update atmospheric mean values without updating perturbation values.

b)  The ability to simulate wind persistence by generating profiles of correlated perturbations as they progress over time for a few hours to a few days.

c)  A variable amplitude large scale wave model that better simulates the dispersions.

d)  Refinements to the perturbation model that produce more realistic wind shear values.

4.  Updated thermosphere models -

a)  Earth GRAM-07 has several updates to the Marshall Engineering Thermosphere model which include:  corrections for inconsistency between constituent number density and mass density; representation of gravity above an oblate spheroid Earth shape, rather than using a spherical Earth approximation; treatment of day-of-year as a continuous variable in the semi-annual term, rather than as an integer day; treatment of year as either 365 or 366 days in length (as appropriate), rather than all years having length 365.2422 days; allows continuous variation of time input, rather than limiting time increments to integer minutes.

b)  The Naval Research Labs Mass Spectrometer, Incoherent Scatter Radar Extended

Model for the thermosphere (NRL MSIS E-00) and the associated Harmonic Wind Model (HWM-93) are now an optional thermosphere model in Earth GRAM-07.

c)  The Jacchia-Bowman 2006 thermosphere model (JB2006) is another optional thermosphere model available in Earth GRAM-07.

5.  Coordinate system changes and revised Earth reference ellipsoid -

Equatorial and polar Earth radii for the "sea-level" reference ellipsoid have been updated to World Geodetic System (WGS 84) values.  Previous (Earth GRAM-99) radius values were from IAU 76.  WGS 84 values are used by the GPS navigation system.  These are also equivalent (to 10 significant figures) to the Geodetic Reference System (GRS 80) values.  Other recent values that could be used include the International Earth Rotation & Reference System (IERS 1989) values.  Earth radius values are set by parameters values in one of the Earth GRAM-07 subroutines.  Input values of altitude greater than 6000 km are treated as geocentric radius values, rather than heights.  Both radius and height are now given in the output file.  Although all input latitudes are geocentric, Earth GRAM-07 now gives both geocentric and geodetic values on the output file. A new subroutine has also been added which computes horizontal distance from great-circle distance between two input latitude-longitude positions.  This subroutine is used to calculate lat-lon "radius" of current position from Range Reference Atmosphere site locations, and to compute horizontal step size in the perturbation model.