12 45 50
02 50 51
04 50 52
06 50 53
08 55 54
10 55 55
12 50 56
14 50 57
16 55 58
18 55 59
20 60 60
22 60 45

So both days are a mean of 57.5

But what does that really tell you?

If I’m not very mistaken, there exist hourly or even by-the-minute temperature data for certain places and periods. Take one month or so of these and hack it into 24-hour slices – first at 0:00, then (with the same source data) at 1:00, 2:00, and so on. To shorten the procedure, start by cutting your 24-hour periods at the two times of day noted as “most critical” above, namely 5PM and 7AM. For each set of 24-hour data slices, find Tmin and Tmax and calculate Tmean. Compare the two sets of Tmax/Tmean/Tmin etc. found. I have a strong feeling the two sets at worst have an offset by a day against each other, but certainly NOT by so-and-so-many degrees Celsius (as the one-day offset can obviously give both positive and negative temp differences depending on the slope of the curve at any point, but they will be negligible when looking at whole months, years, or even decades).

Back to lurk mode (unless someone point me to the kind of data I am talking about so that I may make the experiment myself…)

Even if NWS went to a computer-age technology, we would still be stuck with over a century of historical data to compare the present to. In the TOBS thread, I argued that the best time to measure, in terms of avoiding the double counting bias and wild card, would be around 9AM or 9PM. The most popular times have been 5PM or 7AM, but 7AM is too close to the overnight min, and 5PM too close to the daily high. Switching from 5PM to 7AM is going to generate a big drop in mean tmeperature, that requires an offsetting upward adjustment. Eyeballing Karl’s Figure 8, it looks like about +.9 dC would be justified.

Satellites measure lights as Mosh and others described above. However, the probability that a light detector at whatever frequency precisely captures a town’s lights, completely from N to S and E to W as it sweeps along is just an accident of geometry on a given pass. If the PM tube sees just the edge of town it will report a small lights. If it traverses the centre, it will report larger. If it makes a number of passes and these are combined, then you have to know the maths of how they are combined and the associated errors. In particular, the positional errors are so large that a combination of say 10 images is unlikely to aggregate to more than a blob which has little to do with the true shape of the town – or the location of the climate station.

How this blob relates to Google maps etc is a further source of error, large enough to cause me severe disinterest in the topic.

If you too had spent years trying to find radiometric and magnetic anomalies from an aircraft, then going bush to find them on the ground, you’d have a better appreciation of what I mean. And the aircraft typically flew 80-100 meters above terrain, not several hundred km like a satellite does.

I’d really be giving the whole concept of lights a big miss. It’s got classic signs of being promotional with spin, not hard science.

It’s 1.25 am in California now and that makes for easy typing in Australia since most of USA is asleep. And it’s a cool evening as the last day of Feb 2008 ends. The Bureau of Meteorology reported that -

Victoria has experienced a relatively cool summer with maximum and minimum temperatures typically 1 to 3 degrees below average across the State, the coolest since 1995 in some areas.

That was a historical snippet for year 2002, just to get you going.

For year 2008, Feb Tmax averaged 25.8 and Tmin averaged 14.5. The long-term Feb averages, years 1855-2007 are Tmax 25.1 and Tmin 15.9. Look at the difference in Tmin for this month!!

One swallow does not a summer make, but we are taught that CO2 causes global wrming everywhere, relentlessly, increasingly, with settled science…..

Back to Time of Observation Bias as adjusted for thermometers which record a daily Tmax and a daily Tmin. The TOBS adjustment became an issue because you could do simple sums that showed that if you read the instruments at different times of day, you could get yesterday’s max or min instead of today’s. So I’ve just re-read Karl for the nth time.

The problem seems to be that the accepted methodolgy is to adjust the temperature axis, usually graphed as Y. The mistake occurs in time, on the X-axis. So why not adjust time instead of temperature?

Here is a quick, imperfect attempt at a flowsheet to correct for time.

Read time of observation. Select the preceding 24 hours. If Tmax and Tmin are both present, (and we assume this for this simple model) one is right. Review the past month. Calculate the time of day when the maximum is most often reached – say 2 pm. If the time of observation is before this, use the immediately prior Tmin as correct and go back to the high before it and record that as the Tmax for the day. (If the time of observation is after the monthly Tmax average time, reverse the labelling and accept the prior Tmax on the day as correct and search for the Tmin in the day preceding it, then accept it as the correct Tmin for that day.)

The main objection occurs when a station reading has been historically taken close to the daily max or min. This can be the case where (say) 7 am readings are taken and the daily Tmin has or has not been registered. Historically, it is less common to take readings when close to monthly Tmax, say sometime between noon and 4 pm.

Of course, written station records override these assumptions when available.

If this method is used, in the majority of cases by far, either Tmax or Tmin will be correct and should not need adjustment. If one of them relates to the previous day, it could be higher or lower, but will usually be much the same if there has not been an extreme change in the critical part of the day.

Tmean (which I dislike) can then be taken arithmetically for each day (including an occasional wrong value up or down) and can then be averaged to get monthly obs.

The advantages of this approach are that few temperature changes will be needed and when adjustments are made, they will be close to the preceding day and usually rare, and usually cancelling pos with neg over the long term.

Now shoot me down please.

Yes but the amount of energy generated (i.e., heat) is much less per person. I’d have to believe that in equivalently populated cities the UHIE for N. Korea is much less that in S. Korea.

The second and third world is a lot less electrified than the US. The ratio of lights to people is a lot lower. As an extreme example, have you seen the nightlights picture of the Korean pennisula? It’s real easy to tell where S. Korea ends and N. Korea starts.