NZ/Aust Weather Comparisons

RWood · Unread post by **RWood** » Fri 04/08/2006 08:49

Andy wrote:Yea great reading. Cheers for the info and stats - KEEP IT Coming !

When I first joined the forum and quoted a couple of numbers someone made a sarcastic comment about "facts and figures" - it's good to know some people appreciate them!

- the more so since I don't do observations and so can't contribute in that way.

Weathermad · Unread post by **Weathermad** » Fri 04/08/2006 14:14

Thanks for that!

I didnt realise that its approxiamately 150mm of rain differential between the 2 centres and that sunshine totals are/were relatively even
When I was in Gore, the DSIR had all the statistics for the township but I left about 20 years ago, so that may have changed!

Is it the case RWood that Wellington and Christchurch have become increasingly sunny in recent years?...I have one stat here that says Chch has annual sunshine figures of 1950 hours (taken between 1941-70) whereas now 2100 hours seems to be more the norm

Sorry to ask all these questions!!...I was living near Abbotsford in Dunedin in August 1979 before the landslide of the suburb...Were the winter months of that year extraordinarily wet to cause such destruction?

I'll be quiet now!

RWood · Unread post by **RWood** » Fri 04/08/2006 16:50

Weathermad wrote:Thanks for that!

I didnt realise that its approxiamately 150mm of rain differential between the 2 centres and that sunshine totals are/were relatively even
When I was in Gore, the DSIR had all the statistics for the township but I left about 20 years ago, so that may have changed!

Is it the case RWood that Wellington and Christchurch have become increasingly sunny in recent years?...I have one stat here that says Chch has annual sunshine figures of 1950 hours (taken between 1941-70) whereas now 2100 hours seems to be more the norm

Sorry to ask all these questions!!...I was living near Abbotsford in Dunedin in August 1979 before the landslide of the suburb...Were the winter months of that year extraordinarily wet to cause such destruction?

I'll be quiet now!

No problem, and you've made some very good points. Gore DSIR stopped the sun records a few years back now. Its site I think had some obstructions. My notes are mainly based on the old East Gore obs. that were used up to 1971. I don't think much has changed sunwise - the rainfall comment is fully current.

Some years ago I pointed out to NIWA about the Ch'ch increase but no particular explanation has been suggested. Up to about 1975 the means at both the old City site and newer Airport site were about 1980-1990 hrs. There has been a significant increase since then, particularly in the 1980s. The 1971-2000 30-year mean is 2100: the mean 1975-2004 about 2120. There are some signs it may be flattening off, maybe even a small decrease will occur - unclear.

Wellington's sunshine averaged about 2045 up to 1950 (several sites though). The 1951-1980 average was only 2007. 1984 onwards has seen a big increase with 1992 the only year since then with a substantial deficit (it was a record low). The 30-year mean 1971-2000 is 2065: the latest 30 years 1976-2005 gives 2082.

I have also observed the trend in "maximum gust" speeds on a pole above the Met. building at Kelburn. I have all the monthly averages back to 1972, and the mean "daily gust max" has dropped about 12% over the period on a line of best fit (if you take the overall average, hardly any year since 1983 has reached it). Not a big decrease, but still significant in my view.

Was the Abbotsford landslide in 1979 or 1976? From recall only the period April-August 1979 in Dunedin was quite wet. I'd have to check.

TonyT · Unread post by **TonyT** » Fri 04/08/2006 17:10

I think the airport sunshine recorder was moved to the top of the terminal building in the late 70s, and so can see a significantly wider horizon than previously. I think the difference is more to do with the siting of the instrument than a genuine trend in sunshine hours. Having said that, the 70s were a very cloudy decade in Canterbury, with plenty of easerly anomalies, while the 80s had more westerly, so should have been sunnier.

RWood · Unread post by **RWood** » Fri 04/08/2006 17:29

Very interesting. Even so (for example), 1979, 1980 and some of the months in the 1980s put up totals that seemed to be fairly high for the prevailing weather (e.g. Oct 1986). Presumably also the older "horizon" at the airport was little or no better than at the city gardens site used from 1930 to 1953 - decadal means at either site were much of a muchness until the mid-70s, though for the period of overlap the Airport site had slightly higher readings than the city one.

Of course a big problem in assessing this sort of thing is that of finding a reasonably valid "comparison" site that has had stable conditions during the period of interest.

TonyT · Unread post by **TonyT** » Fri 04/08/2006 17:40

I seem to recall a phD study of the Lincoln data which showed steadily decreasing wind speeds there (not sure if they measured sunshine hours) which were clearly correlated to the growth of trees around the observation site, even to the point of showing increases in wind speeds in the years after the trees were topped!

RWood · Unread post by **RWood** » Fri 04/08/2006 18:20

Yes, and in that vein the Lincoln sunshine data suffered after 1970, and particularly after 1975 - its relationship to other Cant'y plains sites showed that quite clearly. Tree growth would be a prosaic reason.

It was noted years ago that Kelburn's windrun data from the old enclosure near the Carter observatory fluctuated with vegetation heights, and showed several significant jumps in value that matched abrupt reductions in the vegetation height. But my comments on the "pole" at Kelburn where gust data has been collected since about 1967 are of interest I believe, because to the best of my knowledge nothing like that has happened in the vicinity - and the pole is very tall.

Weathermad · Unread post by **Weathermad** » Fri 04/08/2006 21:22

The Abbotsford landslide I believe took place over the months of July and August during 1979 and you mentioned it was quite wet, so thanks for clarifying that

Interesting comments Tony about the differences in the 1970s and 80s regarding the easterlies and westerlies across Canterbury...I wasn't here at the time and pleased I wasn't in the 70's by the sound of things!

I got the warning from you this morning too...much appreciated

tich · Unread post by **tich** » Fri 04/08/2006 21:33

I believe the major Abbotsford landslide occurred in August 1979, very soon after (or maybe still during) a very cold southerly outbreak with snow to low levels.
I don't think it was very wet, but I remember being in Dunedin in May 1979 and it certainly was cold, with snow on the hills.

RWood · Unread post by **RWood** » Fri 04/08/2006 23:40

Checked - May and August were a bit wet, nothing special. June and July quite dry. Can't really blame the weather, methinks.

RWood · Unread post by **RWood** » Fri 04/08/2006 23:45

Weathermad wrote:The Abbotsford landslide I believe took place over the months of July and August during 1979 and you mentioned it was quite wet, so thanks for clarifying that

Interesting comments Tony about the differences in the 1970s and 80s regarding the easterlies and westerlies across Canterbury...I wasn't here at the time and pleased I wasn't in the 70's by the sound of things!

I got the warning from you this morning too...much appreciated

To go back to the Ch'ch sunshine - I think the comment about the site alteration and the values on this graph still leave some explaining to be done. Maybe the change in PDO phase in the mid-70s contributed, so compounding the effect of the site alteration?

Weathermad · Unread post by **Weathermad** » Sat 05/08/2006 08:14

Tend to agree with you on this one too....quite a variation!

One thing that Ive noticed here in Christchurch, particularly in the summer, is that there doesnt appear to be as much morning low cloud with the nor'easters as I recall and therefore the sunshine figures may have increased as a consequence?

I have no figures to back this up but I also wonder about the absence of nor'west winds with the high cloud cover often associated with it.It seems that during some earlier decades the canterbury nor'wester was more prevalent...

Again these are just observations through living here for sometime and as we know over time, the memory(well mine) can play a few tricks!

Looking back over time regarding sunshine hours,rainfall,temperatures etc across NZ, are there any patterns emerging? would more data be useful? or is it all so variable?

RWood · Unread post by **RWood** » Sat 05/08/2006 08:40

I've included the monthly figures for Ch'ch - the most dramatic increase has been in the months of longer daylight, so maybe your observation is at least partly correct. But human memory is not renowned for its objectivity. I have a brother who has lived there since 1971 and he would probably agree with you. Again as I said, a lack of satisfactory comparison sites is a problem. In the case of Wellington I think the sun increase is genuine (but may not be "permanent"!) - along with a modest decrease in windiness.

I'm sure there are many experts who can comment on temperature and rainfall trends - NIWA has general predictions about rainfall trends in the coming decades, relating to warming scenarios with increased midlatitude westerlies (but meanwhile the phase of the PDO we appear to be in now may contradict that for a while). The sun records of quite a number of places in NZ show variations which may have nothing to do with the climate.

TonyT · Unread post by **TonyT** » Sat 05/08/2006 08:59

One of the problems with measuring bright sunshine, is how do you define bright sunshine? With the Campbell Stokes recorder we had the rather unsatisfactory situation where the instrument used to measure defined the parameter it was measuring - ie bright sunshine was defined as when the card in the Campbell Stokes was burnt! This obviously left a lot of room for interpretation, and I believe that it used to tbe case that only one person in the country had responsibility for assessing every sunshine recorder card to ensure consistency of interpretation.

However, other factors come into play, such as the manufacture of the cards - I believe the supplier changed at one point and the new type of cards burnt somewhat more easily than the old ones, so more sunshine started being recorded. This is more of a problem in a place like Canterbury where there are many days with high cloud, and the burning of the card is marginal or incomplete due to the sunshine being less bright. So, a small variation in the ease with which the card burns can be much more significant in Canty than say in Auckland.

RWood · Unread post by **RWood** » Sat 05/08/2006 09:36

I understand NIWA is trying to address this by steadily introducing an instrument at the new EWSs: they told me this some while back:

>>>The Kipp and Zonen CSD1 bright sunshine detectors are at the
>>>following
>>>stations:
>>>
>>>Mt Cook March 2000
>>>Rangiora May 1998
>>>Paraparaumu Nov 1999
>>>Kaitaia Oct 2000
>>>Invercargill Jun 2000
>>>Martinborough April 2001
>>>Appleby April 2001
>>>Middlemarch Sept 2001
>>>Palm Nth March 2001
>>>Blenheim May 2002
>>>Musselburgh April 2002
>>>Mangere Oct 2002
>>>Takaka April 2003
>>>Stratford Jun 2002
>>>Turangi Mar 2003
>>>Wallaceville April 2004
>>>Lake Tekapo June 2003
>>>Franz Josef May 2003
>>>Dargaville July 2003

They point out that in some cases, eg Invercargill, the old Campbell-Stokes readings are still being taken. So perhaps we'll know and understand more in a few years.

All I know about the instrument is that it assesses some sort of "directional differential" in radaiation to assess the sun brightess, or something like that...

ricky · Unread post by **ricky** » Sat 05/08/2006 09:50

Thanks RWood, that is really interesting to see how those new detectors work too..

janewaystv · Unread post by **janewaystv** » Sat 05/08/2006 10:34

Are frosts ever recorded in Sydney?...and if so, whereabouts exactly....Is it more likely in the western suburbs of Sydney?[/quote]

Sydney City has never recorded frosts, the lowest min temp for the city was 2.1 deg C on 22nd June 1932, out in the west-they have frosts, the record (from memory) was -4 or -5 at Richmond and Penrith. I stayed at a mates place in June last year and woke up to a frosty -2 deg C morning.

Have had a couple of very cold mornings this winter for the city-more than usual

but no frosts.

Auckland is the same-hasnt recorded a frost (lowest min they had was 1 or 2 deg C ???

janewaystv · Unread post by **janewaystv** » Sat 05/08/2006 10:41

The longest day at Gore was on 15th December 1974 (from memory-read it in a book somewhere) 15 hours of sun, we should be so lucky here in Syd!

RWood · Unread post by **RWood** » Sat 05/08/2006 12:24

I think it may have happened in both 1954 and 1974. I can definitely recall the 1954 event as I was by then an avid reader of newspapers, and especially of the weather content of any kind.

RWood · Unread post by **RWood** » Sat 05/08/2006 12:36

TonyT wrote:One of the problems with measuring bright sunshine, is how do you define bright sunshine? With the Campbell Stokes recorder we had the rather unsatisfactory situation where the instrument used to measure defined the parameter it was measuring - ie bright sunshine was defined as when the card in the Campbell Stokes was burnt! This obviously left a lot of room for interpretation, and I believe that it used to tbe case that only one person in the country had responsibility for assessing every sunshine recorder card to ensure consistency of interpretation.

However, other factors come into play, such as the manufacture of the cards - I believe the supplier changed at one point and the new type of cards burnt somewhat more easily than the old ones, so more sunshine started being recorded. This is more of a problem in a place like Canterbury where there are many days with high cloud, and the burning of the card is marginal or incomplete due to the sunshine being less bright. So, a small variation in the ease with which the card burns can be much more significant in Canty than say in Auckland.

And even in situations where nothing seems to have changed there can be puzzles thrown up by the data: Coulter's "Sunshine Normals 1941-1970", (published in 1978 and available from Met. for $1.00 at the time!) pointed out contradictory trends for Waimate and Timaru over the 3 decades - nothing about the sites or instrumentation, etc. could be found to explain it .

RWood · Unread post by **RWood** » Wed 09/08/2006 18:36

janewaystv wrote: Thanks Rwood for the Ivc ones-quite a sudden decline in sunshine hours from Feb-Jul and a rapid increase from Aug-Jan especially in some years. Sunshine doesnt increase by seasons/warmer months, its just happens, which i find a bit odd, as in Sydney, mainly sunshine increases toward the warmer months and decreases towards the colder months. Interesting.

The sunshine hours seem similar to that of the UK.

One more request janewaystv - easier than the last one - you could perhaps dig out for me sometime the In'gill sunshine values for each of months of 1927 and 1931 (no record for the intervening years as far as I could find, and they switched to the airport from 1932 on. The old site was considered dodgy, but it would be interesting to see those numbers again (I had them once in the days when much of my data was handwritten-copied), along with perhaps the rainfalls for those months...I know 1931 was a cold windy year and from memory each of those years totalled about 1445 hrs, with the last 7 values of 1931 being (perhaps) 52, 69, 66, 189, 164, 144 and 170.

iT would be much appreciated if you could oblige...

janewaystv · Unread post by **janewaystv** » Wed 09/08/2006 22:20

Rwood, looking at the book, Only have yearly figures of sunshine for Ivc City (1900-1952) for 1927 (1444 hrs) and 1931 (1445 hrs). No monthly data in the book.

Only have month by month totals for rainfall and mean temps for Ivc City from 1900-1952 (some months are missing data)

Have noted for 1928 that Gore had 1998 hrs, that seems a bit too high for Southland dont u think? I remember talking to a bloke at the weather office and he said sunshine pre 1931 is not reliable due to different equipment being used, can you confirm this for me?

From the book only have full sunshine, rainfall and temps data for Ivc Airport from 1932 onwards.

RWood · Unread post by **RWood** » Wed 09/08/2006 22:43

janewaystv wrote:Rwood, looking at the book, Only have yearly figures of sunshine for Ivc City (1900-1952) for 1927 (1444 hrs) and 1931 (1445 hrs). No monthly data in the book.

Only have month by month totals for rainfall and mean temps for Ivc City from 1900-1952 (some months are missing data)

Have noted for 1928 that Gore had 1998 hrs, that seems a bit too high for Southland dont u think? I remember talking to a bloke at the weather office and he said sunshine pre 1931 is not reliable due to different equipment being used, can you confirm this for me?

From the book only have full sunshine, rainfall and temps data for Ivc Airport from 1932 onwards.

Thanks for checking, never mind. I'd be interested though to know the annual Ivc. rainfall total for 1931. W & S of the SI were cold and wet that year I know (but Nelson had the NZ record 2711 hrs, and W'gton 2205, etc.). [If I can find a library that has kept its older copies of "Meteorological Observations", I can get back some of the old data without paying anything...].

Yes, most measurement sites before 1930, and some for a few years later, did not have standard Campbell-Stokes recorders that were fully in use by 1935 I think - and also, centralised checking of records and interpretation of cards was done from then on for many years. But as TonyT has remarked in some earlier posts, there have been some vexed issues around sunshine recording in subsequent years anyway. {See those posts for more detail}.

Values at Napier before about 1925 were far too high to be credible, as an example of older data that one can't trust at all.

In the case of Gore, some of its totals were believeable from start year (around 1915?) for a while but were generally not so from about mid-1920s until 1942 inclusive . Its values in 1938 and 1940 of over 2100 hrs really stretched credibility - not sure how the post-1935 records got through. Even though Q'town and Alexandra had unusually high totals for those 2 years, the In'gill correlations with Gore make the Gore data look silly.

janewaystv · Unread post by **janewaystv** » Wed 09/08/2006 23:04

Rainfall for Ivc City 1931 (Jan to Dec with Annual at bottom)

128.0
133.1
41.7
47.5
71.6
106.7
160.5
90.7
80.3
56.9
93.5
65.8

1076.3

211 raindays.

This may interest you, i have a table that shows sunshine data for some locations ie Akl, Gisborne, Napier, Wgt, Lincoln and Hokitika for the years 1907-1914, shows Napier having 2807 hrs in 1908 and 2277 hrs for Wgt in 1911, the table is very old and no more sunshine readings were put in the book until after 1926.

Heres another one for Gore in 1927 had 2022 hrs.

janewaystv · Unread post by **janewaystv** » Wed 09/08/2006 23:18

The book was given to me by my grand-father (deceased), i dont know where he got the papers from, they are mainly (big!) tables with many NZ locations with a very detailed month by month and yearly summary from 1911 onwards, they come in hand-typed form. I asked my grandmother and she thinks he got them from the papers or posted to him from the weather office (not sure) and pasted them in the book.

1927 map of NZ has shaded areas and non shaded areas. Shaded areas means above avge and non below avge. Its a very old map and its in black and white.

I found this note in the 1919 chapter

A special article on the Climate of NZ was prepared by the Chief Meteorologist by Lieut-Colonel D.C Bates have been printed in pamphlet forms, however they are limited number of copies, would u know anything of this??