This version of the map includes the global lightning probability (the light blue glow overlaying the global map) which varies with season. The Earth's surface also illustrates some seasonal variations. We see that TGFs are roughly correlated with lightning probability, and the lightning probability correlated with seaons. There is more lightning in the summer season.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 22.214.171.124.0