A comparison tool has been developed by mapping the global GPS total electron content (TEC) and large coverage of ionospheric scintillations together on the geomagnetic latitude/magnetic local time coordinates. Using this tool, a comparison between large-scale ionospheric irregularities and scintillations is pursued during a geomagnetic storm. Irregularities, such as storm enhanced density, middle-latitude trough, and polar cap patches, are clearly identified from the TEC maps. At the edges of these irregularities, clear scintillations appeared but their behaviors were different. Phase scintillations (σφ) were almost always larger than amplitude scintillations (S4) at the edges of these irregularities, associated with bursty flows or flow reversals with large density gradients. An unexpected scintillation feature appeared inside the modeled auroral oval where S4 were much larger than σφ, most likely caused by particle precipitations around the exiting polar cap patches. ; This work in China is supported by the National Basic Research Program (grant 2012CB825603), the National Natural Science Foundation (grants 41274149, 41274148, and 41574138), the Shandong Provincial Natural Science Foundation (grant JQ201412), and the young top-notch talent of “Ten Thousand Talent Program.” J. Moen is supported by the Research Council of Norway grant 230996. The work at Reading University was supported by STFC consolidated grant ST/M000885/1. SuperDARN is a collection of radars funded by national scientific funding agencies in Australia, Canada, China, France, Japan, South Africa, United Kingdom, and United States of America. M. Lester acknowledges support from STFC grant ST/K001000/1 and NERC grant NE/K011766/1. The GPS TEC acquisition effort is led by A. J. Coster at MIT Haystack Observatory. We thank the MIT Haystack Observatory for generating GPS TEC data and making them available through the Madrigal Database (http://madrigal.haystack.mit.edu/) and the University of New Brunswick for running CHAIN and providing scintillation data through database (http://chain.physics.unb.ca/chain/pages/gps/). We also acknowledge the NASA OMNIWeb for IMF and solar wind data (http://omniweb.gsfc.nasa.gov/html/sc_merge_data1.html), WDC C1, Kyoto for the AE/AL and SYM-H indices (http://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html), and the Johns Hopkins University Applied Physics Laboratory (JHU/APL) for providing online OVATION (http://sd-www.jhuapl.edu/Aurora/ovation/ovation_display.html). ; Peer-reviewed ; Publisher Version