I have looked in detail at aircraft landing data for the North Runway on July 1st to try to answer the following question. Was the heat pulse that produced the record breaking July temperature at Heathrow due to an aircraft, or was it due to a break in the clouds? The balance of evidence is that it was likely caused by the hot exhausts from an arriving China Southern B787 Dreamliner taxiing past the Met station on its way to terminal 4, then exacerbated by a 10 knot SE wind.
Shown below is the landing data (thanks to Dave Ward). All times are now in GMT in agreement with the Met data. The flight data in the previous post was wrong – it was in CET!
The graph below shows the landing data on the North Runway compared to the recorded temperatures. Smaller jets exit early to reach terminals 1,2,3,5. Larger jets travel further down the runway but still exit lower down in order to also reach terminals 1,2,3 & 5. Only CZ303 will have exited late to reach terminal 4. The 787 also has two of the world’s most powerful Jet engines.
The alternative explanation for the heat pulse is that it was due to a break in clouds increasing solar radiation. This is shown below.
There was indeed an increase in solar radiation at Heathrow coincident with the temperature peak, but if this was the cause then why did a similar increase 30 minutes later produced no response at all. The Kew station shows a much slower response to changing solar radiation. Stephensen screens are also supposed to shield thermometers from the sun and allow air mixing. Therefore the solar radiation explanation is in my opinion inconsistent.
I think it is more likely that CZ303 was the real cause.