Paul H. Domm

Date of Award


Document Type


Degree Name

Master of Science


Department of Engineering Physics

First Advisor

Robb M Randall, PhD.


GAIM-GM is an operational Kalman filter data assimilation model of the ionosphere that can assimilate data from GPS total electron content (TEC), ionosonde electron density profiles, and satellite based in situ electron densities. The Air Force Weather Agency (AFWA) uses GAIM-GM to specify and forecast the ionosphere. An in depth investigation into the accuracy of these forecasts has not been completed. GAIM-GM output obtained from four cases run from combinations of geomagnetic and solar activity was used to determine GAIM-GM forecast accuracy. Forecast accuracy was determined through the use of a skill score as well as other statistical tools to include root mean square error (RMSE) and percent differences between the forecasts and the observations. It is determined that overall, GAIM-GM forecast output is more representative than the climatological reference 90% of the time indicating that GAIM-GM can therefore forecast short term fluctuations in the ionosphere. The RMSE increases during daytime, geomagnetic storming and during solar maximum. Skill scores decrease at night and GAIM-GM shows an overall diurnal bias to under forecast at night and over forecast during the day.

AFIT Designator


DTIC Accession Number