In the study region, using our meteorologically designed scale and orientation, we find that transmission affects output by reducing variance, slowing the rate of change, and, during the study period, eliminating hours of zero production. The result is that electric power from wind would become easier to manage, higher in market value, and capable of becoming a higher fraction of electric generation (thus more CO2 displacement).From my non-specialist perspective, the overall result still doesn't look that great, however. If I zero in on the Pgrid, and rearrange the figure a bit:
The problem is that the US east coast is not really big enough to be above synoptic scale: the size of the big cyclones and anti-cyclones that govern weather in temperate latitudes. Another figure in the paper illustrates the kind of thing that can go wrong. Here the colors are wind speed (in m/s) and the lines show pressure isobars:
As you can see, with a big enough high off the coast there can be hardly any wind up or down the whole region.
There are several important points of context to make however. The first good news is that clearly east coast solar would tend to counter swings in east coast wind to a significant degree. Windless days of high pressure in the summer are exactly when you'd expect solar plants to be at close to maximum output - whereas the wind can pick up the slack in the winter (solar panels will not be doing a lot of good on those stormy days in November).
The other thing is, even within the US context, the east coast is not really where the wind is. This map from the National Renewable Energy Laboratory shows the distribution:
A very important point: the power in the wind is proportional to the cube of the wind speed, so those purplish regions in the high plains have about 10 times the potential per unit area of the yellowish-green regions on the coasts. That's where the wind is. And clearly, by feeding wind into the grid across the US, the performance is going to be smoother again, since a single high cannot cover the whole country.
It seems like with renewables, when feeding small amounts into a mainly fossil fuel grid, that's workable as they basically displace fuel use when they are available, but don't displace much capacity so the fossil fuel plants are still there to smooth the renewables out. An all-renewables grid would also be possible, but requires averaging over huge areas (and/or enormous amounts of storage). In between those extremes, things are going to be awkward.