Fig. 8.
![Fig. 8.](http://media.springernature.com/full/springer-static/image/art%3A10.5047%2Feps.2011.04.013/MediaObjects/40623_2015_640060493_Fig8.jpg)
Variation of the daily hourly values of Hm in km against time, at Ebro, for the four seasons of the high solar-activity year 2000: (a) winter, (b) spring, (c) summer, (d) fall and for the four seasons of the low solar-activity year 2007: (e) winter, (f) spring, (g) summer, (h) fall. The corresponding monthly median values and upper and lower quartiles are also plotted.