Modified day/night number of lightning strokes over the US region.

The monthly number of lightning strokes over the US region between 2006 and 2010. This data is derived from the WWLLN database. The number of lightning strokes in each month is multiplied by a year-dependent factor so that the number of lightning strokes in each year is equal to the number of lightning strokes in 2010. There are two files, one file corresponding to DEMETER daytime data (between 9:30 and 11:30 LT) and the other file corresponding to nighttime data (between 21:30 and 23:30 LT).