Fig. 7
From: PCA and vTEC climatology at midnight over mid-latitude regions
V HWM07 over the North American region: a amplitude of the temporal variation, a 1 (the y-axis has to be multiplied by a factor of 10−2), b eigenvector or spatial variation, e 1, c synthesized data for mode 1 (a 1·e T1 ) for red (east) and blue (west) rectangles, d difference between red and blue curves of c, e the amplitude of the temporal variation, a 2 (the y-axis has to be multiplied by a factor of 10−2), f eigenvector or spatial variation, e 2, g synthesized data for mode 2 (a 2·e T2 ) for red (east) and blue (west) rectangles, h difference between red and blue curves of g. Finally, the time-averaged \(\bar{V}_{{{\text{HWM07}} }} \left( x \right)\) (i), the synthesized data, j \(\bar{V}_{\text{HWM07}}^{*} \left( t \right)\), for red (east) and blue (west) rectangles, and the difference (\(\overline{{{\text{d}}V}}_{\text{HWM07}}^{*} (t)\)) between red and blue curves of j (k)