This could be an inquiry more suitable for the "stupid questions" thread, but maybe somebody more familiar with "weather" and atmospheric modeling could address it here any way :
I understand why the Arctic has "lows" in summer. After all, it is the coldest spot around, and cold means air contracts and thus forms a low. But then why is it that the "highs" over lower latitude in summer seem to dominate over the oceans ?
Note the highs over the Atlantic and (the ridiculously-resilient-ridge) over the Pacific.
In summer the oceans are relatively cool and land is relatively warm, so why are these highs over the oceans rather than over land and not the other way around ?
Neven, feel free to move this if it's a clog.
Subtropical ridging is driven largely by the Sun warning the equatorial regions, creating an area of rising air, the intertropical convergence often called the ITCZ. The rising air then moves poleward, and descends at around 30° north and south. Descending air creates these high pressure systems, and they move north and south with the seasons. The Hadley cell basically.
Since the oceans lack topography and don't really have diurnal warming and cooling, the weather patterns are relatively stable, and are modified by larger oscillations such as ENSO, AMO, NAO, PDO to name a few. So these high pressures, or ridges you are noticing, are semi permanent features, but fluctuate due to the factors I mentioned above.
Low pressure outside of the tropics, is largely driven by baroclinic processes, basically clashes of warm and cold air, and are associated with rising air, where high pressure has sinking air. There are also fronts, which divide warm and cold air, as mid latitude cyclone almost always have a warm and a cold side. Persistent cyclones like we have been seeing, can have very complex fronts, and "occlusions" (areas where cold fronts catch warm fronts).
As air rises, it cools, and warms as it sinks. The "dry" adiabatic rate is 9.8°C/km, and the "wet" adiabatic rate is 5.5°C/km. A rising parcel of air, that has less than 100% relative humidity will cool at the dry rate, once the temperature cools to the dew point, it begins to condensate and form clouds, and now cools at the wet rate.
Sinking air tends to"dry" out the clouds. So when looking at 850mb temps (roughly 1500m high), if this air is able to mix down to the surface, it can theoretically warm as much as 15°C, under ideal circumstances.
I track a great deal of winter storms, as I generally receive over 2 meters of snow in the winter. So I'm just following the arctic because I don't have snowstorms to track.
and because it's important to weather and climate.
