Thursday, June 14, 2007

The Sun is all that seems to matter

Initial results by combining a couple of stations in south east queensland were looking a little bizarre, so I decided to view both Amberley and Cape Morton separately. Firstly Amberley:

We have limited data at Midnight, but everything else goes back to the 50's with maximum and minimums going back 10 years more.

We find significant decreases in temperature both at 3am and 6am, and then as soon as the sun rises, a significant increase in temperature. Quite strange really, that such a sudden change can occur. Noon and 3pm both record significant increases as well, however temperatures at 6pm showed no difference, but a significant decrease in temperature at 9pm was found.

In other words, Amberley is getting colder over time at night, and warmer during the day. This might be good reason why maximum temperatures showed a significant increase, however minimum temperatures showed a significant decrease. This being probably the first time in our analysis that significant decreases in temperature have occurred over night.

No surprisingly then, we find that the rate of change of temperature at 9am was significantly higher than at 6am, and 6pm temperature anomalies were significantly lower than that at 3am. Seems like the only thing that is heating up Amberley is something that tends to be heating it up during the day - maybe the sun? And the influence of this has increased over the past 50 years.

Cape Moreton paints a different picture. Unfortunately only a handful of years of temperature data is recorded outside the times 9am and 3pm. 9am shows a significant increase in temperature since 1957 whilst 3pm does not. However, quite clearly from looking at the graph, from 1960 onwards an upward trend as occurred especially in the last 6 years.

The graph of maximum temperatures is extreme. No real changes in maximum temperature in the past 90 years and then a sudden 1 degree increase on average per day in the last 6 years. Incredible. Minimum temperatures also show a massive increase of late, but not as sudden despite being well defined.

As previously said, we only have good data for Capre moreton when the sun is out (max/min/9am/3pm), as all other times only go back to 1988. However, by analysing differences in anomalies between certain times we can get a lot of information out of the limited data.

Differences in temperature between 3am,6am and the minimum temperature is shown here. The difference is obvious and startling. The minimum temperature is on average 0.63 degrees higher than the overnight temperatures and this amount seems to be increasing over time (the increase is significant). Hence the minimum temperature is exaggerating the overnight temperature by as much as 1 degree per day (that is if one uses the minimum temperature as a good gage for overnight temperatures!)

This sudden change is highlighted when looking at time temperature anomolie differences. When looking at the difference in temperatures from 9am and 6am, we see a highly significant increase of up of 0.7 degrees per day. Hence for some reason (sun perhaps?) temperature anomolies at 9am are significantly higher than at 6am. No surprises that when the sun was not playing an effect (temp diffs between 6am and 3am) - there was no differences in the rate of change of temperature anomalies.

However when looking at temperature differences from 6pm and 3pm, we find a significant decrease in temperature. The trend in the graph is obvious. And when the sun loses it's effect (9pm vs 6pm) - no differences at all.

The proof is strong, the results significant, and the conclusion obvious.

In south east queensland - just like almost all other places that we have studied - we have seen no significant increase in temperature overnight. And the rate of change of temperature anomalies increases when the sun rises and decreases when the sun sets. There can only be one explanation for this, that the sun is playing a major influence over the temperatures in this and other areas in Australia.

Can it be more obvious?


Alan Atchison said...

Wouldn't all of the taxiways and runways at Amberley act as a heat sink on sunny days and also lessen the temperature drop at night?

Jonathan Lowe said...

quite possibly. It's hard to say what effect this would have, and I'm not entirely sure how big the airport is.