Ground GNSS Atmospheric Sensing - GNSS Remote Sensing: Theory, Methods and Applications - page 48

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0

−90 −60 −30 0 30 60 90

Latitude (deg)

Fig. 3.13 Distribution of annual variation phase with the latitude. The phases are counted as
clockwise from the north

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120

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0

−90 −60 −30 0 30 60 90

Latitude (deg)

Fig. 3.14 Distribution of semiannual variation phase with the latitude. The phase values are
counted as clockwise from the north

3.3.2.3 Diurnal and Semidiurnal ZTD Cycles

The non-seasonal ZTD residuals have significant diurnal and semidiurnal variations.
Figure 3.15 shows a case of the 10-year ZTD time series (upper), power spectrum
(middle) and the mean diurnal ZTD values (bottom) at local times (LT) in two
hour increments (LT D 1, 3, 5, :::, 23) at Wuhan (WUHN), China, where the
mean diurnal ZTD values are calculated from the 2-h ZTD time series over