Since we can't get gridded pressure observations from satellites, what we use are called reanalyses. These are basically a weather forecast model that takes in all of the observations from around the world to make the best possible guess of what the atmosphere currently looks like.
So this paper is an attempt to see which reanalysis is actually the most correct, using satellite data. Because while we don't have global observations of pressure, we do have satellite observations of rainfall and winds. And we know that a "cyclone" should have "cyclonic" winds - which in the southern hemisphere basically means clockwise, spiraling into that central low point. So we took the satellite winds for a database of "known" ECLs to find some parameters that an ECL should have, and then looked at what the satellite winds showed for a whole bunch of reanalyses.
What we found was that there was a really simple metric we could use to check if an identified ECL was a "real" cyclone with cyclonic winds, and using this made the reanalyses a lot more similar. The one reanalysis that had too many ECLs, had a lot of systems which weren't really cyclones, and looked a lot more like a cold front. Conveniently, the "best" reanalysis for ECLs was the European one, which is already the most popular for ECL studies. This helps us get a better handle on which dataset to use for evaluating climate models.