Posts Tagged ‘extremes’

ACORN-SAT 2: Eucla: The Devil in the detail

February 18, 2019

I’m having a break from looking at Acorn 2 data from Queensland.  I’ve been wondering:  what’s going on?  What’s beneath these changes?  In particular, I was struck by statements in the accompanying Research Paper that

In total, there were 966 adjustments applied in version 2 of the ACORN-SAT dataset, 463 for maximum temperature and 503 for minimum temperature.”

The Bureau is referring to breakpoints in the data where adjustments are applied to all previous years.  In the daily data, there are tens of thousands of adjustments at each station.

For example, in Eucla’s Tmax record, there are 34,145 daily datapoints; 34,144 in Acorn 1; and 33,858 in Acorn 2.  There are  10,190 instances where Acorn 1 makes no change to raw data, and 9,312 in Acorn 2.  Most of the instances of no adjustments are since 1995.  Before then almost every day has been adjusted.

And the devil is in the detail.

The following plots show how adjustments are applied to the range of raw maxima.  First Acorn 1.

Figure 1:  Acorn 1 adjustments as applied to raw maxima at Eucla

Ac1 raw adj

Figure 2:  Acorn 2 adjustments as applied to raw maxima

Ac2 raw adj

Acorn 2 removes the large negative adjustments for temperatures in the high 30s, and the spread is wider for very high temperatures.  So far so good.

Figure 3 shows where many of these adjustments are made.

Figure 3:  Acorn 2 and  raw maxima

Eucla 1913-2017

Between 1930 and 1995 many high temperature spikes are reduced by 5 degrees and more.

For example, here is November 1960.

Figure 4:  Raw, Acorn 1, and Acorn 2 in November 1960

Eucla Nov 1960

The Bureau can truthfully claim that there is a balance between positive and negative adjustments.

However, note how all temperatures over 35C have been reduced by five degrees.  This is common across these years.

Perhaps temperatures on very hot days at Eucla in the 1960s were exaggerated?  Perhaps they were not read accurately?

If this pattern of hot day reductions is generally followed at stations across large regions, e.g. southern Australia, the effect will be that climate analysis based on Acorn 2 will show that past extremes were generally not as high as nowadays.

And that can’t be a bad thing for the meme.

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Townsville Rainfall In Context

February 11, 2019

The rain event which caused massive floods in Townsville (and fearful stock losses in the north-west) has now ended.  There have been some who have made further political capital out of this disaster by linking it to climate change.

According to Independent Australia, a “progressive journal”,

The City of Townsville, with some 20% of its suburban zones under water today (6 February 2019), might now be a model for the world — for possible climate change impacts and handling them. 

These days, the very heavy falls have been happening more frequently — for example, in 2007, 2009 and then in 2010.

Time for a reality check.

This has indeed been a record breaking event for Townsville.  A few graphs will illustrate.  Townsville airport has had its wettest 14 day period since 1941, averaging over 100mm per day.

Fig. 1:  14 day rainfall

Tville 14d rainfall

It has also broken the record for rainfall over 31 days:

Fig. 2:  31 day rainfall

Tville 31d rainfall

And with the wet season far from over, it is very likely to break the 121 day rainfall record.

Fig. 3:  121 day rainfall

Tville 121d rainfall

Townsville’s rain is very seasonal.  Annual rainfall averages about 1127mm, and half of that falls in January and February, with another quarter in December and March, so a plot of 121 day rainfall captures the relative strength of wet seasons over the years.  There doesn’t appear to be any recent increase in wet season strength.  What is interesting is there are periods of wetter and drier years, which is more plainly seen in a plot of decadal rainfall.

 Fig. 4:  Decadal rainfall at Townsville

Tville decadal rainfall

Rainfall appears to be in a decreasing trend.

But what about the claim for greater frequency of very heavy rain events?  Heavy rain events are usually short and intense, so three day rainfall will also show relative frequency and intensity.

Fig. 5:  Three day rainfall

Tville 3d rainfall

The “Night of Noah” in 1998 is obvious, and there was another intense event in 1953.  But there is NO trend.  (The calculated trend is zero.)  Intense events are not more frequent.  Similarly, the number of days per year recording 100mm of rain shows zero trend, even though there have been eight already this year.

Fig. 6:  Count of days per year with over 100mm of rain

Tville days over 100mm

There is no climate change signal in Townsville’s rain record.

Now, to show how different locations can lead to completely different interpretations of trends in climate, I turn to two locations in wetter parts of the tropics that I have some knowledge of.  I lived for many years not far from Pleystowe and Sarina Sugar Mills near Mackay, which are about 30 km apart.  Sarina appears to have an increasing trend in rainfall:

Fig. 7:  Decadal rainfall at Sarina

Sarina decadal rainfall

While Pleystowe shows no trend.

Fig. 8:  Decadal rainfall at Pleystowe

Pleystowe decadal rainfall

Notice the similar patterns of wetter and drier periods in Townsville, Pleystowe, and Sarina.

And incidentally, the most intense and highest rainfall events in these locations occurred many years ago, in 1990-91, the 1970s, the 1950s, and 1918.  As with the recent Townsville flood, these occurred when the monsoon trough, with embedded decaying cyclones, lingered overhead for many days or even weeks.

The Townsville flood was not due to climate change, but to a frequent North Queensland phenomenon- an intense monsoon trough stuck in one place for too long.  This was an unusually intense and long lasting example, but such events are not more frequent or more intense.

How Reliable is the Bureau’s Heatwave Service?

January 24, 2019

The Bureau of Meteorology presents heatwave assessments and forecasts in the interest of public health and safety.  Their heatwave definition is not based on any arbitrary absolute temperature, but uses a straightforward algorithm to calculate “excess heat factors”.  From their FAQs:

“Heatwaves are calculated using the forecast maximum and minimum temperatures over the next three days, comparing this to actual temperatures over the previous thirty days, and then comparing these same three days to the ‘normal’ temperatures expected for that particular location. Using this calculation takes into account people’s ability to adapt to the heat. For example, the same high temperature will be felt differently by residents in Perth compared to those in Hobart, who are not used to the higher range of temperatures experienced in Perth.

This means that in any one location, temperatures that meet the criteria for a heatwave at the end of summer will generally be hotter, than the temperatures that meet the criteria for a heatwave at the beginning of summer.

……

The bulk of heatwaves at each location are of low intensity, with most people expected to have adequate capacity to cope with this level of heat.”

Back in 2015 I showed how this algorithm works perfectly for Melbourne, but fails to detect heatwaves in Marble Bar and instead finds heatwaves at Mawson in the Antarctic.  In light of the long period of very hot weather across most of western Queensland, what does the Heatwave Service show?

Here is their assessment of conditions in Queensland over the last three days….

Fig. 1: Heatwave assessment for 21-23 January 2019

heatwave assessment

Most of inland Queensland has been in a “Low-Intensity Heatwave”, with a couple of small areas near the southern border of “Severe Heatwave”.

And here is their forecast for the next three days..

Fig. 2:  Heatwave forecast for 24-26 January 2019

heatwave forecast

Much the same, with a bit more Severe Heatwave coming.

So what were temperatures really like in the previous three days? Here’s the map for the middle of that period, Tuesday 22nd:

Fig. 3:  Maximum temperatures for 22 January

max 22 jan 1 day

About half the state was above 39 degrees C, a large area was above 42C, and there were smaller areas of above 45C.

And in the past week:

Fig. 4:  Maximum temperatures for 7 days to 23 January

max 22 jan 1 week

Average maxima for roughly the same areas were the same, except there was a larger area averaging over 45C!

This follows December when a large slab of the state averaged from 39C to 42C for the month.

Fig. 5:  Maximum temperatures for December 2018

max 22 jan 1 month

I’m focusing on Birdsville, circled on the map below (and indicated on the maps above.)

Fig. 6:  Queensland forecast towns- Birdsville indicated

qld map

Here are the maxima for Birdsville for January:

Fig. 7:  Birdsville Maxima for January

birdsville jan max

And here’s the forecast for the next 7 days:

Fig. 7:  Birdsville 7 Day Forecast

birdsville forecast

Apart from the 6th, when it was a cool 38.8C, since Christmas Eve the temperature has been above 40C every day, and is forecast to stay above 40C until next Tuesday (and above 45C until Sunday).  Minima have been above 25C on all but three days since Christmas.

And that’s a “Low Intensity” heatwave, with “most people expected to have adequate capacity to cope with this level of heat.”

The Bureau’s unspoken message?  It might be a bit hot, but you’re supposed to be used to it.  Harden up!

Western Queensland residents are pretty tough, but surely a month of such heat deserves a higher level of description than “Low Intensity”- especially for the vulnerable like babies, old people, and visitors.

This is worse than laughable.  The Bureau’s heatwave service is a crock.  As I said in my 2015 post, a methodology that fails to detect heatwaves at Marble Bar (or Birdsville!), and creates them in Antarctica, is worse than useless- it is dangerous.

Drought and Climate Change Part 2: Rainfall deficiency

September 7, 2018

In my last post, I looked at long term rainfall trends across Southern, South Eastern, and South Western Australia, and found no cause for alarm at recent rainfall decline.  Droughts can occur at any time and cause much hardship across wide parts of the country.  Global Warming Enthusiasts are gnashing their teeth, believing man-made climate change is making droughts worse.  Greg Jericho in the Guardian wrote last Thursday 30th August, “If you are a prime minister going out to the rural areas and you’re not talking about climate change, and you’re not suggesting that droughts are more likely to occur and thus farmers need to take greater responsibility, then you are failing in your job.”

Are droughts really “more likely to occur” with climate change, and is there any evidence they are becoming more frequent, more intense, and more widespread with global warming?

The Bureau of Meteorology says:

Drought in general means acute water shortage.

The Bureau’s drought maps highlight areas considered to be suffering from a serious or severe rainfall deficiency…. for three months or more….

……

  • Serious rainfall deficiency: rainfall lies above the lowest five per cent of recorded rainfall but below the lowest ten per cent (decile range 1) for the period in question,
  • Severe rainfall deficiency: rainfall is among the lowest five per cent for the period in question.”

This map of meteorological drought (areas in the lowest ten and five percent of 12 months rainfall to 31 August) shows the extent across Australia:

Fig. 1:  Recent 12 month Rainfall Deficiency Australia

12m drought map

Parts of central and southern inland Queensland, parts of eastern South Australia, many parts of New South Wales, and small areas of Victoria are in drought.  Notice that the droughted areas are separated by areas that are not in drought.

But, but… all of NSW is in drought, isn’t it?

100% of NSW has been drought declared, and 54.7% of Queensland, and indeed some parts are in a very bad way.   But “drought declaration” is the term the media, politicians, and general public don’t understand.  They assume that because 100% of NSW is drought declared, this means all of NSW is in drought.  Not so.  Drought declaration is a political or at best administrative instrument for giving drought assistance to farmers and communities.  Some areas of Queensland that have not yet been drought declared really are in the grip of drought; some “drought declared” areas of NSW are not in drought, as this map of NSW (6 months March to August) shows:

Fig. 2: 6 month Rainfall deficiency NSW

NSW map 6m

Of course the blank areas have had below average rainfall, which may turn into full blown drought, so the NSW government is being proactive.  However, they are not at this time in meteorological drought with serious or severe rainfall deficiency.

Trends in Drought Incidence

In the bigger picture, how widespread, how intense, how long lasting, and how frequent are droughts becoming in Australia?  For this analysis I use monthly rainfall data from 1900 to July 2018 from the Bureau of Meteorology at their Climate Change page, and calculate the number of months where the rainfall total of the previous 12, 18, 24, or 36 months shows severe deficiency (in the lowest 5 percent of all months since 1900) or serious deficiency (in the lowest 10 percent).  (I am looking at droughts that last at least 12 months, not just short dry spells, and 12 months total rainfall includes rain in all seasons.)

I do this for various regions, as shown on the map below.

Fig. 3:  Australian Regions

Climate regions

I have plotted the number of consecutive months where the 12, 18, 24, and 36 month totals are in the lowest 5% and 10% of their respective values since 1900, and calculated the trend in months per century of increase or decrease. There are 96 plots, so I will only show a couple of examples, and summarise the results in Table 1 below.

Table 1:  Trends in Drought Incidence (Months per 100 Years) for various Australian Regions

Trend table

A negative trend indicates decreasing drought incidence, shaded green; a positive trend indicates increasing incidence, shaded pink.

Australia wide, and in the regions of Northern and Southern Australia and the Murray Darling Basin, and South Australia as a whole, since 1900 droughts of all lengths have become less frequent, and because these are broad regions, less widespread.  There is no evidence that climate change is making droughts more likely to occur, except for smaller areas (Victoria, Tasmania, and SW Australia) which have an increasing frequency of droughts of all lengths.

36 month dry periods are more frequent in SW Australia, SE Australia, Eastern Australia, Tasmania, Victoria, (and interestingly Queensland, but only for <10% deficiency).

Some examples will illustrate the complexity of the picture.

Fig. 4:  Number of consecutive months per calendar year of 12 months severe rain deficiency: Australia

12m 5% Aust

Fig. 5:  Periods of 36 months serious rain deficiency: Australia

36m 10% Aust

In the past droughts of all lengths and severity were more widespread across Australia.

Fig. 6:  Periods of 36 months severe rain deficiency: Southern Australia

36m 5% Sthn Aust

Similarly, multi-year periods of severe rain deficiency were much more frequent and widespread across Southern Australia before 1950.  In the last 50 years there has been only one month where the 36 month total was in the lowest 5th percentile.

Fig. 7:  Periods of 12 months severe rain deficiency: New South Wales

12m 5% NSW

Fig. 8:  Periods of 36 months severe rain deficiency: New South Wales

36m 5% NSW

Fig. 9:  Periods of 12 months serious rain deficiency: New South Wales

12m 10% MDB

Fig. 10:  Periods of 36 months serious rain deficiency: New South Wales

36m 10% NSW

Across NSW, 4 months of 2018 had 12 month totals in the serious deficiency range, but none in the severe range.  Droughts of all severity and duration have become less frequent and widespread.  The Millennium Drought lasted longer but was less severe than the Federation Drought.

The Murray-Darling Basin lies across four states including most of NSW, and is Australia’s premier food and fibre producing region.  The current drought is affecting many areas in this region.

Fig. 10:  Periods of 12 months severe rain deficiency: Murray-Darling Basin

12m 5% MDB

Fig. 11:  Periods of 12 months serious rain deficiency: Murray-Darling Basin

12m 10% MDB

Fig. 12:  Periods of 36 months serious rain deficiency: Murray-Darling Basin

36m 10% MDB

We can conclude from these plots of the Murray-Darling Basin that this drought is patchy, and while nasty, is not the most intense or long lasting even in living memory, let alone on record, and that droughts are becoming less frequent and less widespread.

Fig. 13:  Periods of 36 months severe rain deficiency: Queensland

36m 5% Qld

Fig. 14:  Periods of 36 months serious rain deficiency: Queensland

36m 10% Qld

Queensland has little trend in frequency of drought with severe deficiency over three years but less severe droughts have been more frequent- due to the droughts of the 1990s and the Millennium drought.

Fig. 15:  Periods of 36 months serious rain deficiency: Victoria

36m 10% Vic

The Millennium Drought stands out as the longest period of widespread serious rain deficiency.

Fig. 16:  Periods of 36 months serious rain deficiency: South-West Australia

36m 10% SW Oz

Here we see that all but one month of all the 36 month periods of serious rain deficiency have occurred since 1970, reflecting the marked drying trend.  This really is an example of climate changing.

Winter rainfall

Fig. 17:  Winter Rainfall Deciles across Australia, 2018

winter rain 2018

According to the Climate Council, “Climate change has contributed to a southward shift in weather systems that typically bring cool season rainfall to southern Australia.”  However the usual areas affected by this southwards shift, Tasmania, south-west Victoria, southern South Australia, and most of the south-west of Western Australia, have had an average to above average winter.  Droughted areas are to the north.   The southwards shift of weather systems caused by Climate Change cannot be claimed to have any part in this drought.

Drought is a dreadful calamity wherever and whenever it occurs.  And on top of other difficulties in Queensland is the bureaucratic approval process under Vegetation Management regulations before graziers can push mulga to feed starving stock.

This drought may get worse if a full El Nino develops.  It is unlikely to break before six months or even 18 months.  By then it will be much more severe and widespread.  However, climate change has not caused this drought.  While there is evidence for increasing drought frequency and thus likelihood of more drought in the future in Tasmania, southern Victoria, southern South Australia, and the south-west of Western Australia, across the rest of Australia there is strong evidence that droughts have become less frequent, less severe, less widespread, and shorter.  If climate change is claimed as the cause of increasing droughts in the far southern regions, then climate change must also be causing less frequent droughts across the vast bulk of Australia, where droughts are always “likely to occur”, but not “more likely”.

Replicating Lewis et. al. (2017): Another Junk Paper

October 9, 2017

The recently released scarey predictions about “50 degree temperatures for Sydney and Melbourne” touted by Sophie Lewis are hardly worth wasting time on.  The paper is

Australia’s unprecedented future temperature extremes under Paris limits to warming, Sophie C. Lewis , Andrew D. King  and Daniel M. Mitchel, (no publication details available).

The paper is junk.  It has some very sciencey sounding words but is at heart pure speculation.  Like most “projections” by Global Warming Enthusiasts, the predictions are untestable.  Scarey temperatures are possible IF (and only if) IPCC scenarios are valid and we get either 1.5C or 2C warming by the last decade of the century.  That’s what the paper rests on.

The paper looks at Australian summer means, Coral Sea autumn means, and New South Wales and Victorian daily January maxima.  AWAP data are used for Australia and NSW and Victoria, and HadCruT4 for the Coral Sea region (which includes most of Queensland).

I have just looked at Australian Summer Means, and that was enough for me.  Lewis et.al. say that the decadal mean from 2091-2100 may have Australia wide summer means of 2 to 2.4 degrees above the mean of 2012-13, or 30.1 to 30.5C, with resultant very high daily maxima in southern cities.

I could have saved them the trouble, and at considerably less cost.

All I needed was the AWAP data for summer means (I purchased monthly AWAP data up to 2013 a couple of years ago), and plotted it with a 2nd order polynomial (quadratic) trend line:

lewis predictions summers1

And also showing decadal means (although the first and last decades have several missing summers):

lewis predictions summers2

There: the trend line goes smack through the higher (+2 degrees) projection, so it must be right!

Only trouble is, extrapolating with a quadratic trend is not a good idea. Lots can go wrong in the meantime.

So my plot is about as useful as the Lewis et.al. paper, and that’s not much.

Watch an AWS Fail

August 30, 2017

(With thanks to Lance, Phill, and others)

A week ago, a colleague alerted me to strange behaviour at an Automatic Weather System at Borrona Downs in NSW.  This is a brand new weather station, with its first observation on 21 July.

Phill writes in an email:  Do you ever wonder why you get a shiver down your spine?  Pity the poor folks in the NSW far west.  

 From this mornings (20th  August) NSW observation list: The minimum temperature at Borrona Downs AWS was -62.5C at 9:59pm last night.  Probably some clowns with a bucket of dry ice or liquid nitrogen.  Perhaps Odin’s host crossed the night sky or maybe death just walked on by…  The individual reads don’t show anything lower than -37.5C also at 9:59 so the cold spike was quite sudden.  It went from -62.5C sometime between 21:58:00 and 21:59:00 to -37.5C at exactly 21:59:00 to -4.4C at 22:00:00.

I was too busy and preoccupied until now to follow this up, but I have a few days now.

Borrona Downs Station is in sandhill and claypan country in the far northwest of NSW:

Borrona Dns map

Borrona Dns aerial

Here is the Climate Data Online minima record (note minima indicated on two days):

Borrona Dns cdo

The following plots show the deterioration in the performance of the AWS.  Firstly, the comparison with Tibooburra, 110km away, showing a sudden change at 29 July:  Subtracting Borrona Downs data from Tibooburra shows that Borrona Downs Tmin is too high from this date.  The whole (brief) record should be scrapped.

Borrona Dns Tibooburra comp

But the devil, as Phill found, is in the detail.  Here is part of the record for the 19th:  Note the Low Temp at 9.59 pm, and I have indicated the official minimum for the day which would have occurred early that morning.

Borrona Dns 19 Aug

The Bureau has the minimum at 4.6C, but how was this value obtained?  The erroneous values, (including that of liquid nitrogen), are flagged, then manually removed, and the previous lowest temperature is retrieved from the one minute data for the day.  This also happened on the 26th:

Borrona Dns 26 Aug

Things got much worse on August 27th:

Borrona Dns 27 Aug

Why could no minimum be found?  Did the BOM realise that none of the data were reliable, and were essentially random errors?  Remember that the AWS records values every second, and the highest, lowest, and final second values for each minute are stored.  My guess is that many of these values were unreliable as well, even though many of the final second half hour values seem reasonable- for example 4.4C at 5.30 am.

This continued on August 28th   with an all time low of -69.5C:Borrona Dns 28 Aug

And the BOM ceased reporting values at 3:30 pm.

This description of events was confirmed by the Bureau’s response to a query:

“Do you know what is causing the very low temperature recordings?

There is a hardware fault within the AWS which is generating spurious values. The Bureau’s technicians are investigating but a site visit will be required.

Why was the August 19 low temperature recording not left blank?

Manual quality checking confirmed that the spiking on 19 August did not occur near the minimum  temperature for that day, as a result, the minimum temperature was recorded.”

This begs the question: is this what happened at Goulburn Airport on 2 July ? The initially reported figure of -10.4C was flagged as suspicious, so the previous low temperature of -10C was then reported, then this was removed , then the initial -10.4C was reinstated.  Perhaps.

-10.4C certainly should not have been flagged as too low for that location, as many other  values below 10C have been observed, including the record -10.9C recorded on 17 August 1994.  However, perhaps it was flagged as suspicious by comparison with the series of values before and after: too large a change in temperature from second to second.  But if so, why didn’t the BOM CEO just say so, instead of getting tangled in a web of conflicting explanations?

The AWS at Borrona Downs has failed.  So has the Bureau of Meteorology.

 

Garbage In, Garbage Out

August 7, 2017

(By Ken Stewart, assisted by Bill Johnston and Phill Goode; and cross-posted with Jo Nova)

Early ABC Radio news bulletins last Wednesday morning were led by this item, which you can read in full at ABC Online.

More climate scientists needed to avoid expensive mistakes, review urges

Apparently we urgently need 77 climate scientists to predict the future of areas like the Murray-Darling Basin with climate modelling.

Interestingly, Professor McDougall of the Australian Academy of Science points out that one of those “expensive mistakes” was the $2 billion desalination plant built in Queensland as a response to the millennium drought, “which really wasn’t an indication of climate change at all”.   Why didn’t the good professor raise his voice before the money was wasted?

But I digress.

Reliable modelling and projections for the future are surely desirable.

But such modelling must be based on reliable data, and the reliability of temperature data in Australia is demonstrably poor.

Example 1:  As has been widely reported in The Australian, and by Jennifer Marohasy and Jo Nova, cold temperatures at two separate sites (and possibly many others) were altered to appear warmer, then changed back, then deleted.  The BOM gave two conflicting explanations, both of which cast grave doubt on the reliability of “raw” temperature data from an unknown number of stations.

Example 2:  After enquiring why there are frequently two different temperature readings for exactly the same minute at various weather stations, a Bureau spokesperson told me that:

Firstly, we receive AWS data every minute. There are 3 temperature values:
1. Most recent one second measurement
2. Highest one second measurement (for the previous 60 secs)
3. Lowest one second measurement (for the previous 60 secs)

(See here and here.)

In other words, Australian maximum and minimum temperatures are taken from ONE SECOND readings from Automatic Weather Stations.  Spikes due to localised gusts of hot air, or instrument error, become the maximum for the day.  (This rarely has a large effect on minima, as night time temperatures are fairly smooth, whereas during the day temperature bounces rapidly up and down.  This is shown in this plot of temperatures at Thangool Airport in Queensland on Australia Day this year.)

Thangool 26 Jan 17 1 min

And this is for the same day between 3.00pm and 4.00pm.

Thangool 26 Jan 17 3 to 4pm

As you can see the temperature spikes up and down in the heat of the day by up to one degree between one minute and the next.  But these are the temperatures at the final second of each minute: during the intervening 59 seconds the temperature is spiking up and down as well, which we know because occasionally the highest or lowest temperature for the day occurs in the same minute as a final second recording on the BOM database (usually on the hour or half hour).  This can be up or down by two or three degrees in less than 60 seconds.

This is in contrast to the rest of the world.  The WMO recommends 1 minute (60 second) averages of temperature to be recorded to combat this very problem of noisy data, and this is followed in the UK.  In the USA 5 minute (300 second) averages are calculated.

From THE WEATHER OBSERVER’S HANDBOOK by Stephen Burt (Cambridge University Press, 2012):

Observers handbook

Even without software or human interference as in Example 1, this means Australian temperature data, in particular maxima, are not reliable.

Example 3:  Historically, temperatures were observed from Liquid In Glass (LIG) thermometers.  From the 1990s, Automatic Weather Stations (AWS) were installed using Platinum Resistance Thermometers (PRT) and are now the source for daily data.  AWS thermometers are very precise, but as I showed in Example 2, their data is used idiosyncratically to record 1 second spikes, frequently resulting in higher maxima and less often slightly lower minima than a 1 or 5 minute average.

One would think that with such a major change in technology there would be comparative studies reported in the BOM’s meteorological journal or other “peer reviewed” literature.  Apparently not.

Dr Bill Johnston has investigated this and says:

Parallel data were collected all over Australia for over a decade, some until last year when thermometers were removed, at manned sites, mainly major airports (Ceduna, Sydney, Hobart, Perth, Darwin, Alice Springs, Albany, Norfolk Island, Wagga to name a few) and also met-offices such as Cobar and Giles. However, comparisons between screens were done at one site only (Broadmeadows, Melbourne, which is not even an official weather station) using PRT only and reported as a “preliminary report”, which is available (https://www.wmo.int/pages/prog/www/IMOP/WebPortal-AWS/Tests/ITR649.pdf) however, after AWS became primary instruments, as I’ve reported before, the Bureau had an internal policy that parallel liquid-in-glass thermometer data were not databased. Furthermore, they had another policy that paper-data was destroyed after 2-years. So there is nothing that is easily available…. there is also no multi-site replicated study involving screen types and thermometers vs. PRT probes ….

Deliberate destruction of data is scandalous; the only way now to compare Automatic Weather Stations (AWS) and Liquid in Glass, is to hunt for sites where there is overlap between two stations; where the AWS is given a new number. This is possible BUT the problem is that the change-over is invariably confounded with either a site move or the change to a small screen.

Therefore we suspect that the introduction and reliance on AWS has led to artificially higher maxima (and thus record temperatures) than in the past, but we have no way of knowing for sure or how much.

So we now have (1) temperatures that are altered before they even become ‘raw’ data; (2) use of one second spikes for recording daily maximum and minimum temperatures, very probably resulting in artificially high maxima and slightly lower minima; and (3) no way of telling how the resulting data compare with those from historical liquid-in-glass thermometers.

How can the CSIRO hope to produce reliable climate modelling with any number of climate scientists when the BOM cannot produce reliable temperature data?  Garbage in, garbage out.

How Temperature Is “Measured” in Australia: Part 1

March 1, 2017

By Ken Stewart, ably assisted by Chris Gillham, Phillip Goode, Ian Hill, Lance Pidgeon, Bill Johnston, Geoff Sherrington, Bob Fernley-Jones, and Anthony Cox.

The Bureau of Meteorology maintains the Southern Oscillation Index (SOI), one of the most useful climate and weather records in the world.  In About SOI,  the Bureau says:

 Daily or weekly values of the SOI do not convey much in the way of useful information about the current state of the climate, and accordingly the Bureau of Meteorology does not issue them. Daily values in particular can fluctuate markedly because of daily weather patterns, and should not be used for climate purposes.

It is a pity that the BOM doesn’t follow this approach with temperature, and in fact goes to the opposite extreme.

Record temperatures, maximum and minimum temperatures, and monthly, seasonal, and annual analyses are based not on daily values but on ONE SECOND VALUES.

The Bureau reports daily maximum and minimum temperatures at Climate Data Online,   but also gives a daily summary for each site in more detail on the State summary observations page , and a continuous 72 hour record of 30 minute observations (examples below), issued every 30 minutes, with the page automatically refreshed every 10 minutes, also handily graphed .  These last two pages have the previous 72 hours of readings, after which they disappear for good.  However, the State summary page, also refreshed every 10 minutes, is for the current calendar day only.

This screenshot shows part of the Queensland observations page for February 26, showing the stations in the North Tropical Coast and Tablelands district.

Fig. 1:  District summary page

mareeba-example

Note especially the High Temp of 30.5C at 01:26pm.  Clicking on the station name at the left takes us to the Latest Weather Observations for Mareeba page:

Fig. 2:  Latest Observations for Mareeba

mareeba detail example.jpg

Notice that temperature recordings are shown every 30 minutes, on the hour and half hour.

In Figure 1 I have circled the Low Temp and High Temp for Mareeba.  Except in unusual circumstances, High Temp and Low Temp values become the maximum and minimum temperatures and are listed on the Climate Data Online page, and for stations that are part of the ACORN network, become part of the official climate record.  It is most important that these High Temp and Low Temp values, the highest and lowest recorded temperatures of each day, should be accurate and trustworthy.

But frequently they are higher or lower than the half hourly observations, as in the Mareeba example (0.6C higher), and I wanted to know why.  In this post I show some recent examples, with the explanation from the Bureau.

Perhaps the difference between the Latest Weather Observations and maximum temperature reported at Climate Data Online is due to brief spikes in temperature in between the reported temperatures of the latest observations, such as in this example from Amberley RAAF on February 12.

Fig. 3:  Amberley RAAF temperatures, 12 February 2017

amberley-12-feb

A probable cause would be that the Automatic Weather Station probe is extremely sensitive to sudden changes in temperature as breezes blow warmer or cooler air around or a cloud passes over the sun.

However, this may not be the whole story.

Occasionally the report time for the High Temp or Low Temp is exactly on the hour or half hour, and therefore can be directly compared with the temperature shown for that time at the station’s page.

These progressive Low and/or High Temps on the half hour or hour occur and can be observed throughout the day at various times, as well as at the end of the reporting period.

For example, here is a mid-afternoon screenshot of the Queensland- Wide Bay and Burnett district summary for Wednesday 15th February.  I have highlighted the High Temp value for Maryborough at 1:00pm.

Fig. 4:  District summary at 2:00pm for Maryborough 15 February 2017

obs-mboro-15th

In the Latest Observations for Maryborough, I have highlighted the 1:00pm reading.

Fig. 5: Latest Observations at Maryborough at 01:00pm on 15 February

obs-mboro-15th-detail

The difference is +1.5 degrees.  Here I have graphed the results.

Fig. 6:  Maryborough 15 February

mboro-15th-graph

That’s a 1.5 degree difference at the exact same minute.

Here is a screenshot of Latest Observations values at Hervey Bay Airport on Wednesday 22 February.  Low Temp for the morning of 23.2C was reached at 6.00 a.m.

Fig. 7:  Hervey Bay, 06:00am  22 February 2017

hervey-bay-22nd

Note that at 6.00am, just after sunrise, the Latest Observations page shows that the temperature was 25.3 degrees.  The daily Low Temp was reported as 23.2 degrees at 6.00am – 2.1 degrees cooler.  This graph will show the discrepancy more plainly.

Fig. 8:  Hervey Bay temperatures 22 February

hervey-bay-22nd-graph

What possible influence would cause a dawn temperature to drop 2.1 degrees?

I sent a query to the Bureau about Hervey Bay, and the explanation from the Bureau’s officer was enlightening:

Firstly, we receive AWS data every minute. There are 3 temperature values:
1. Most recent one second measurement
2. Highest one second measurement (for the previous 60 secs)
3. Lowest one second measurement (for the previous 60 secs)

Relating this to the 30 minute observations page: For an observation taken at 0600, the values are for the one minute 0559-0600.

I’ve looked at the data for Hervey Bay at 0600 on the 22nd February.
25.3, 25.4, 23.2 .

The temperature reported each half hour on the station Latest Observations page is the instantaneous temperature at that exact second, in this case 06:00:00, and the High Temp or Low Temp for the day is the highest or lowest one second temperature out of every minute for the whole day so far.  There is no filtering or averaging.

The explanation for the large discrepancy was that “Sometimes the initial heating from the sun causes cooler air closer to the ground to mix up to the temperature probe (1.2m above ground).”

However, in Figure 7 above it can be seen that the wind was south east at 17 km/hr, gusting to 26 km/hr, and had been like that all night, over flat ground at the airport, so an unmixed cooler surface layer mixing up to the probe seems very unlikely.

You will also note that the temperatures in the final second of every half hour period from 12.30 to 6.30 ranged from 25C to 25.5C, yet in some second in the final minute before 6.00 a.m. it was at 23.2C.  I have shown these values in the graph below.

Fig. 9:  Hervey Bay 05:59 to 06:00am

hervey-bay-22nd-at-6am

The orange row shows the highest temperature for this last minute at 25.4C at some unknown second, the blue row the lowest temperature for this minute (and for the morning) at 23.2C at some unknown second, and the spot temperature of 25.3C at exactly 06:00:00am.  The black lines show the upper and lower values of half hourly readings between 12:30 and 06:30: the high temp and 06:00am readings are within this range.

23.2C looks a lot like instrument error, and not subject to any filtering.

Further, there are only two possibilities:  either from a low of 23.2C, the temperature rose 2.2 degrees to 25.4C, then down to 25.3C; or else from a high of 25.4C it fell 2.2 degrees to 23.2C, then rose 2.1 degrees to 25.3C, all in the 60 seconds or less prior to 06:00:00 a.m.

How often does random instrument error affect the High and Low Temps reported at the other 526 stations?  Like Thargomindah, where on February 12 the High Temp was 2.3 degrees to 2.5 degrees higher than the temperatures 15 minutes before and after?

Fig. 10:  Thargomindah temperatures 12 February 2017

thargomindah-12-feb

Or was this due to a sudden rise and fall caused by a puff of wind, even a whirl-wind?

Who knows?  The Bureau certainly doesn’t.

 

In Part 2, I will look at patterns arising from analysis of 200 High and Low Temps occurring in the same minute as the half hourly values, and implications this has for our climate record.

Another ABC Fail

February 5, 2017

Viewers of ABC-TV news, and followers of ABC News Online, were treated to a story on Friday night about “Turtle hatchlings dying in extreme heat at Mon Repos”, as it was headlined at ABC News Online:

Piles of dead turtle hatchlings are lining Queensland’s famous Mon Repos beach amid a heatwave which has pushed the sand’s temperature to a record 75 degrees Celsius.

While the majority of hatchlings break free from their nests at night when the sand is cooler, those escaping in the day face overheating.

“They can’t sweat, they can’t pant, so they’ve got no mechanism for cooling,” Department of Environment and Heritage Protection chief scientist Dr Col Limpus said.

….

The extreme heat is also conducted down to the turtle’s nest, pushing the temperature to about 34C, which is approaching the lethal level for incubation.

That is the hottest temperature recorded in a nest in more than a decade.

A record 75 degrees sand temperature? Hottest nest temperature in more than a decade?

Time for a reality check.

I have no data on temperatures inside turtle nests, but I do have data on temperature at nearby Bundaberg Aero (Hinkler Airport), which is an ACORN site.

Using monthly Acorn data, here is a plot of all January maxima at Bundy.

bundy-jan-max

January’s mean maximum of 31.6 degrees C was equalled or exceeded in 1924, 1931, 1969, 1998, 2002, 2006, 2013, and 2014.  While monthly mean doesn’t tell us about individual days, it does give us a clue about daily temperatures in hot years.  For that I also use ACORN daily data- adjusted, homogenised, and world’s best practice apparently.

How do temperatures at this time of year compare with those of previous years?  The next figures show data for the first 45 days of every year, that is from January 1 to February 14.

bundy-jan-max-daily-45

The past three weeks at Bundaberg have been at the high end of the range, but no records have been broken, and no days have been even close to 35C.  What about previous years?  The next plot shows the number of consecutive days above 35 degrees: very likely to raise sand temperature above what it has been this year.

bundy-jan-max-daily-45-over-35

No days this year above 35C, but at least 27 occasions in previous years of single days reaching 35C, at least 6 of 2 days in a row, and one of 3 days in a row above 35C.

A 7 day running mean will show whether temperatures have been consistently high.

bundy-jan-max-7d-av-45

As you can see 2017 is high but not extreme.  2002 had a 7 day average just under 35C.

This graph plots temperatures of the first 45 days of years with similarly hot January temperatures.  2017 is the thick black line.

bundy-jan-max-daily-45-hot-yrs

On one day- January 20- 2017 was hotter than the other years.  Note how in several years the temperature drops to the mid 20s when heavy rain falls.  Note also the temperature reached the high 30s in February 2002.

The final graph shows the 7 day average of the same period of similarly hot years.

bundy-jan-max-7d-av-45-hot-yrs

Several previous periods were hotter than so far this year.

Once again we see misleading claims being made and reported by the ABC as gospel, without any attempt at fact checking.  A simple check shows that, while it may be true that the reported temperatures are the hottest recorded by these researchers, it is extremely unlikely that these were as high as they were in past years.  On every count- daily, monthly mean, 7 day mean, consecutive hot days- it can be shown that this year, while hot, is not as hot as many previously, and it follows that sand temperatures would similarly have been hotter in the past.

And that’s without considering the Holocene Optimum and the Eemian.

Another ABC fail.

Unprecedented South Australian Weather!

January 22, 2017

(and it has been like that for 178 years!)

There were more blackouts in South Australia a couple of days ago following a wild storm.  In a report in the Adelaide Advertiser, SA Power Networks spokesperson Paul Roberts is quoted:

“This is just another example of the unprecedented weather in the last six months,” Mr Roberts said, referring to bouts of wild weather that have hit power supplies hard this summer and the preceding spring.

21mm of rain was measured at the Kent Town gauge.

Just how “unprecedented” is Adelaide’s weather over the past few months?  I couldn’t find any records for the number of severe storms, so for a proxy I have made do with rainfall data from West Terrace and Kent Town in Adelaide.  The overlap period has very similar rainfall recordings so I joined the two series to give a record starting on 1 January 1839.  That’s 178 years of data.

When thinking about “unprecedented”, we need to check amount, intensity, and frequency.

Firstly, a few plots to give some context.  How unprecedented was Thursday’s storm?

Fig. 1: Rainfall for the first 21 days of January compared with Days 1 – 21 of every year

adelaide-rain-21-jan

Note Thursday’s rainfall had less rain than four previous occasions on this day alone, and 20 or so in previous Januarys.

Fig. 2: Rainfall for each day of 2016 compared with each day of every year:

adelaide-rain-2016

Note the December storm had extreme rain (for Adelaide) but not a record.

Amount and intensity has been higher in many previous years.  141.5mm was recorded on 7 February 1925.

Fig. 3: 7 day average rainfall over the years:

adelaide-rain-2016-7d-avg

The topmost dot shows the maximum 7 day average for each year.  2016 got to 13.4mm on 4 October- multiply by 7 to get the weekly total rain.  Note there were many wet and dry periods all through the record.

21mm of rain fell in a severe storm on Thursday, so I arbitrarily chose 20mm as my criterion for heavy rainfall in one day as a probable indicator of stormy weather.  I am the first to admit that 20mm might fall steadily all day and not be at all associated with wild winds, and wild winds can occur without any rain, but bear with me.

Fig. 4: Rain over 20mm throughout the year:

adelaide-rain-2016-above-20

There seems to be no increase in amount or intensity of rain at any time of the year.

Fig. 5: Frequency:

adelaide-rain-2016-cnt-above-20

Note 2016 had 7 days with above 20mm in 24 hours.  That’s the most since… 2000, when there were 8 days- and many previous years had 7 or 8 days, and 1889 had 9.  So no increase in frequency.

However, Mr Roberts was referring to the last six months, spring and summer.  So let’s look at rain events over 20mm from July to December, firstly amounts recorded:

Fig. 6: July to December Rain over 20mm:

adelaide-rain-above-20-last-6m

Nothing unusual about 2016.

Fig. 7:  Frequency of heavy rain July – December:

adelaide-rain-2016-cnt-above-20-last-6m

1973, 1978, and 1992 had the same or more days with over 20mm.

I now restrict the count to spring and summer only:

Fig. 8:  Spring and Summer frequency:

adelaide-rain-2016-cnt-above-20-last-4m

Not unprecedented: 1992 had one more.  Add in last Thursday’s event to make them equal.

Conclusion

Adelaide has a long climate record, showing daily rainfall has varied greatly over the years.  There is no recent increase in amount, intensity, or frequency for the whole year, or for the last six months or four months.  Spring and summer rainfall in 2016 was not unprecedented, and to the extent that spring and summer falls over 20mm are a proxy for storms, there is no evidence for an increase in wild weather.  This is normal.  Get used to it, Mr Roberts, and make sure the electricity network can cope.