We have used the TOPEX satellite data set to compare climatologies of total
electron content (TEC) measurements from the dual-frequency altimeter with
the Doppler orbitography and radiopositioning integrated by satellite (DOR
IS) TEC results and with the international reference ionosphere (IRI) and B
ent model predictions corresponding to the satellite measurements. We have
used the TOPEX measurements from launch in 1992 through 1997 to build a dat
abase that includes time, geographic and geomagnetic coordinates of the mea
surement, geomagnetic indices (Kp, previous Kp, hemispheric power, and inte
gral of hemispheric power over the previous 36 hours), solar index (F10.7),
TOPEX and DORIS TEC measurements, and empirical model (IRI and Bent) resul
ts corresponding to the TOPEX measurements. We have binned the measurements
in a magnetic local time, magnetic latitude coordinate system to produce g
lobal maps of TEC. We present climatological differences between TOPEX TEC
and DORIS measurements as well as between TOPEX and the two empirical model
s. The maps were constructed using all appropriate TOPEX TEC data, DORIS TE
C measurements, and the corresponding Bent and IRI model results for solar
minimum conditions.