Looking at your chart, I think it probably only updates the OAT every 30 minutes, and overall it seems to show a steady rise, apart from 0900, when it falls, and that does coincide with a heat pump start up. The OAT on my charts is potted at one minute intervals, and looks something like this:

In this chart most of the OAT variations are one degree, but sometimes it is two degrees. Interestingly, the big spike in LWT at 1300 (DHW heating) has no more effect on the OAT than the other cycles.

1.  The heat pump is in a bit of a cold well so its action cools the air around it when its on

2.  The air intake sensor is warmed, when the heat pump is off, by the waste energy from the heat pump itself

1. I don't think my heat pump is in a true cold well, I have certainly seen far worse. The back of the heat pump is in front of a wall (as most are) and that will mean it sucks in air from the sides, and the air from the sides might well be replaced by cooler air from the front. But that's about the extent of it. There is vegetation to one side and in front of the heat pump, but it is not that close (2 metres or so) and it is rather porous vegetation, not a dense hedge. The heat pump is very slightly raised on the actual ground it sits on.

2. Possible, but I think unlikely, the heat pump is after all off, and I think I am right in saying there is a bit of over-run on the fan when it starts up and shots off. I might be able to confirm this from the minute data. 

As an aside, I think Homely has to please different nomenclatures for, as you will see, when I ask for compressor on/off, I only see a straight line. I see another straight line if I select HP Outdoor temperature; this suggests to me that the names apply to different makes - or maybe there is more information but Daikin don’t provide it!

Regards, Toodles.

There is clearly a difference is air intake sensor reading between when the heat pump is on and when its off, with the value being typically 2C higher when its off.  Following @toodles comment it occurs to me that there are (at least) two possible interpretations

1.  The heat pump is in a bit of a cold well so its action cools the air around it when its on

2.  The air intake sensor is warmed, when the heat pump is off, by the waste energy from the heat pump itself

Un until now we have been implicitly assuming (1), but (2) may be more likely (although if it is (2) then the effect would 'wear off' during a prolonged off period eg a setback, which Im not sure we are seeing.

As @cathoderay says there are some anomalies and, rather than speculate further, @cathoderay and I are waiting for the data from the independent OAT sensor.

I do now have the separate RC-4 temp data logger in a well ventilated coal bunker and in a few days time we will have a better idea of the hourly true OAT, and can then compare that to the Midea reported OAT.  

I can understand why it would if the outside sensor is within the pump case, but that’s not best practice and ours is many feet away on a north facing wall.

In this case it's in the case.  There is also conclusive evidence that it reacts to what the heat pump is doing.

I can understand why it would if the outside sensor is within the pump case, but that’s not best practice and ours is many feet away on a north facing wall.