Jay - these plots are intriguing  -perhaps Im reading the graphs wrong and should turn the pages upside down :-)  I got to say I never see WWVB signals at the levels indicated for Anchorage but of course I have to deal with JJY too co-channel which do reaches these levels -hmm...  and if I compare signal to noise wise for the average Joe not a lot of people buy WWVB locked devices as they just dont work up here. See http://www.nist.gov/pml/div688/grp40/vb-coverage.cfm  we never go Red, and notice the affect of the Rockies etc
 
What with VLF phase changes of Polar ice caps and perma frost causing higher loss modal paths, reflections from Mountain ranges causing standing waves, Moon/Sun tidal losses, effects from Red Sprites, Solar Proton events, Man kind globally causing VLF background noise increase and more so during the work week,  high modal losses East West Im surprised I see anything here...(grin)
 
There are a lot of papers out there on VLF profiling over various grounds, some interesting facts on reflection coefficients' on vertical incidents of VLF waves into glaciated areas etc.....and a lot more.
 
I think someone mentioned Siple2 and its VLF dipole - Siple was about 3400ft ASL but I cant recall if the actual continental land mass is pushed lower cos of the weight of the ice = in any case most of what I can recall was my breakfast cutlery and the kitchen utensils humming musically whilst Jupiter was running - I was surprised it didnt drive the guys mad who were stationed there all the time...
 
No sign of /1 yesterday, well not a clear one - I did get a straight line of a few pixels just pre sun down here but thats all.
 
Laurence KL7 L et al