Some airports in some locations are just prone to having a more unique local weather pattern than others in more "normal" locations. A good example is an airport in a valley which gets narrower near the airport would be prone to lower pressure due to the venturi effect of the wind moving down the valley and speeding up (lowering the pressure) at the constriction where the airport is (and the obvious higher wind speeds parallel to the valley direction). Other airports have completely other random local weather patterns too. Sometimes these local-scale weather patterns / events tend to overcome the larger scale weather patterns so sometimes, you really just never know. This is why I think meteorology is really interesting, because not only do you need to understand each scale and their associated parameters, but you also need to identify which pattern will dominate the overall conditions (like whether a high pressure system moving into this valley airport's area will overcome the local scale wind venturi enough to register a higher than normal pressure reading).

As for the high at the equator, while the LARGE (Global) scale weather pattern depicts an average lower pressure at the surface (due to the ITCZ), the equator still gets highs and lows, warm and cold fronts, and other synoptic and local scale weather events so high pressure areas can occur at the equator however the most prominent pressure system at the equator is a low pressure due to heating, convergence, and the resultant lifting action. Earth's rotation and the thickness of the atmosphere at the equator do not really contribute to the equatorial low pressure (THAT MUCH!! They do contribute to global scale weather patterns considerably, but not for this specific topic)