Digital Signal Processing Reference
In-Depth Information
January
April
50
60
GPS
IRI−2001
GPS
IRI−2001
40
50
30
40
20
30
10
20
0
10
0
5
10
15
20
25
0
5
10
15
20
25
Local time (hour)
Local time (hour)
July
October
35
50
GPS
IRI−2001
GPS
IRI−2001
40
30
30
25
20
20
10
15
0
0
5
10
15
20
25
0
5
10
15
20
25
Local time (hour)
Local time (hour)
Fig. 4.13
Comparison of TEC at grid point (37.5N, 127.0E) between GPS reconstruction and
IRI-2001
from around 10:00 to 12:00 LT, namely so-called winter anomaly. However, the
nighttime behavior shows that TEC values are higher in summer than in winter,
which indicates that this phenomenon vanishes at night near the maximum of the
solar cycle in 2003.
Similar with the NmF2 deviation percentage as Eq. (
4.31
), the monthly averaged
diurnal variation percentages of the GPS reconstruction TEC with respect to the IRI-
2001 model are obtained (Fig.
4.14
). It has been seen that the IRI-2001 significantly
overestimates the TEC in daytime in winter and almost underestimates the TEC in
other time by about 30 %.
4.4.4
Ionospheric Slab Thickness
The ionospheric slab thickness is defined as the ratio of the total electron content
(TEC) to the maximum electron density of the F-region (
Nm
F2, proportional to the
square of the F2-layer critical frequency foF2). It represents the equivalent slab
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