J07

Ha, yes that is what you were implying. I see your point now, sorry!

Personally I think the models are wonderful things, and they don't seem to get a lot of respect. I think they do a good job for what they are. But of course they will never be perfect. I'm not sure people realise the extreme non-linearity of the atmosphere! Open any textbook specific to meteorology and what do you see? Non-linear, non-linear, non-linear equation after equation after equation! And even these can just be approximations. There are many "fudges" going on when constructing a mathematical model of the atmosphere, some work pretty well but others can get quite strained. But if you don't use the "fudge" you may end up with something that is entirely unsolvable by analytic means. That's where, thank God, we have computers. I wish I knew the ins-and-outs of the models and the actual mathematical differences between them, but I don't. However, you can get your bottom dollar that they do a heck of a lot of solving of highly, highly non-linear differential equations, and they do it numerically. These two things combined are never going to give you perfect results! Some simple looking equations are unsolvable analytically- consider the integral of exp(-x^2) dx. Simple looking, but cannot be solved without using erf(x), which I think (correct me if I'm wrong) is only defined numerically, not analytically. To be honest, I dread to think the absolute horrors that those poor computers are solving, second by second, minute by minute. And the thing is, because they do this, they take heaps of calculation off the hands of people, allowing people to get on with what they are good at - THINKING*! ...hence pushing the science to higher and higher levels, which in turn goes on to improve the models, which in turn goes on to give us better results! In other words, I think these computer models are great. People are learning all the time- this will improve the computers. For a good example of non-linearity, the pendulum is easy enough. It's non-linear, but can be "fudged" to become linear. However, as this is an approximation, it's going to go wrong at some point. I don't know the details of that system in particular, but it's certain that at some finite (and possibly very large) time t, the fudged solution will diverge significantly from the actual behaviour. Now consider the atmosphere, how much more complex it is. Computer models aren't going to improve exponentially, they can only do it gradually, bar an absolutely mind-blowingly enormous breakthrough in analytic analysis of non-linear equations (not to mention chaos....partial differential equations....and so on). * I should also mention moaning.

Extend summer? Nah. Summer is often going to be limited by aspects such as sunshine hours, strength of the sun (it's far, far too weak in September for that to be a summer month, IMO) as opposed to just temperature. Last autumn was odd, quite dry and mild for a long period, but I don't believe it really "extended" summer at all. There are natural limits that we can't overcome by increasing temperatures. I know in an exceptional year we may get 21C in October, that also I think doesn't extend summer- it's just an autumn bonus. I've personally always considered mid/late May to be summer simply because of very mild/warm temperatures, extremely long days and decent sunshine hours with sun that actually has some kick to it (unlike September). This makes not much sense to me. The cause of global warming is increased energy being trapped in the atmosphere, this leads to increased air temperatures. But I would expect that oceans would be the *last* to respond due to their high specific heat- in other words they can absorb a lot of this extra heat without increasing much in temperature. I would have expected land masses to be more susceptible to change.

This is an exciting one. Thanks for the updates.

Saw some pictures the other day of a DOC "office" on Raoul, the roof had taken a real battering and not much was left- but structurally it seemed to stand up fairly well. I don't know what the sustained winds speeds/gusts were there though.

Drought worsens, despite a bit of rain earlier in the week. I swear I saw some new blades of grass the other day. http://www.stuff.co.nz/waikatotimes/4391588a6004.html Check this out: Wow! Top picture is last August, second picture is 6 months on, February. Location is Scotsman Valley in central Waikato. Forecast is for sunny weather and highs of 26-28C until Sunday/Monday when humid northerlies are hitting and will bring either rain or drizzle along with uncomfortable nights.

Going to miss NZ but I think the wind over the upper North Island is going to be increased as she tracks by. I wouldn't fancy being on Raoul Island at the moment though!

Looks like Gene might head towards NZ, but there will be high pressure over the country by then. What's the chances of ex-TC Gene bringing rain to the North Island?

Want Switzerland? - See Queenstown. Want New Zealand? - See Westport. (Westport's fairly recent campaign to attract tourists ) I'd say the mountain range has everything to do with it- down in Hokitika, there's a catchment in the gorge that might record 12m of rain in a fairly wet year, a few dozen miles to the east, in Canterbury, they'd probably be looking at maybe 0.7m in the Mckenzie. Think Wesport hit 25C today - and probably will be one of the better places to be in NZ right now as it's sheltered from the southerly. As for your story about shoes sticking to the tar in Auckland- maybe that is why everyone wanders around the city barefoot now :unsure:

This season started off with a horrendous October- wet, cold and with many many high winds. Unseasonal late frost caused vineyard damage. Then suddenly November's second half made that month one of the warmest and driest in a long time. Not a good start to summer, unless you're a holiday maker (and plenty of those about!). This transitioned into January which has ended so dry that I feel it may be worth a thread in extreme weather- since it may develop into something worthy of that description. February has begun with hot, dry Nor'Westers starting fires in the south, followed by a cool southerly change bringing rain. Christchurch was up to 34C today, and in one hour dropped from 32C to 18C as the S pushed through. There are some almost unbelievable stats coming out from Jan, which you can access here: http://www.niwascience.co.nz/__data/assets...990/0801sum.pdf A basic summary in my words: Rainfall This is the big one. Basically, for almost the entire population of New Zealand, rainfall has been below 50%. For perhaps 50% of NZ, rainfall has been below 25%. The worst hit area is the Waikato (this is an area south of Auckland, centred on the city of Hamilton). Anyone seen Lord of the Rings? Matamata, the green and pleasant vale where they filmed Hobbiton has only got 4% of its January rainfall. Various areas in the Waikato and east/central South Island have also got <10% of average rain. Considering the cumulative effect of the dry November, this has obviously created major issues. When you see pictures on the news, you have skinny sheep running across land that looks hot, barren, dusty and entirely infertile. Totally unsuitable for sheep farming. In other words- looks like Australia. But it shouldn't be like that at all. All the grass has died, all that remains is scrub. NIWA are saying that even with normal rainfall, it won't be enough. Media report: http://tvnz.co.nz/view/page/1318360/1567903 As you can see from this, it's not just a dry January that is ruining things, it's that the dry weather is looking to run all the way from November until April (at this point), adding up to some major problems that many parts of NZ do not see as often as other countries. Temperatures Highest temperature is 35C. Not unusual, and not all that special at all. What has caused problems is the 3 weeks period where the South Island was hitting at least 30C every day (other than 2 or 3 days I think). Alexandra in Central Otago has had an average January maximum of 28.2C. That is 4.5C above normal! Pretty extreme stuff. Will be interesting to see how this impacts on vines and fruit they grow up there. Alexandra is the driest town in New Zealand, getting similar rainfall to Alice Springs. In fact, many areas of NZ in general have been getting average maxima more akin to that of the Mediterranean (normally, NZ summers are cooler that there). An interesting one is Chateau Ruapehu, averaging 20.2C, 2.5C above normally. That is on the central plateau, I would guess at something like 1200m ASL. Sunshine Sunniest January ever for Southland and Otago. Above average everywhere else, except Northland (rubbish weather in January - wet, cool and cloudy). Some areas have been averaging 10 hours of bright sunshine per day. Wind Highest gust was 98 mph, due to ex-TC Funa. ------------- Further media reports: http://www.stuff.co.nz/waikatotimes/4373371a6004.html Please let it rain http://tvnz.co.nz/view/page/423466/1563992 Drought hurting farmers http://tvnz.co.nz/view/page/423466/1568337 Canty fires Wonder what February will bring? We are entering into the warmest 3 weeks of the year, and this is also the driest month. So it doesn't bode well at all, but who knows for sure? The other problem is that March is generally considered to be a "summer" month, as it is warmer than December in a large number of regions. It also tends to have more settled weather.

Beeb have done windchill for as long as I can remember:

Great links, thanks. The HPA site was good for a look, the sun really is extremely weak in the UK isn't it. That reading of 25! :lol: Wow....I can't imagine what that feels like. And, as you say, a decently populated area. Yikes. On the subject, here is an interesting development: Real-time UV Index display First prototype at NIWA Lauder before installation at Alexandra swimming pool Second prototype in use at the Goldrush Multisport Event in Central Otago NIWA has developed a real time UV display in consultation with the Cancer Society and Sunsmart. The first prototype is currently installed at the new Molyneux Aquatic centre in Alexandra. Current UV intensities are sensed by a detector designed to measure the sun burning UV from the sun and sky that is incident on a horizontal surface. The signal is amplified and then displayed by means of servo technology that is used in model aircraft. A large pointer displays the current intensity of UV, in terms of the internationally agreed UV Index scale. The scale is subdivided into 5 different regions corresponding to 5 different behavioural responses. For UVI values less than 3, the risk is “low” and the colour code is green. UVI values exceeding 10 are designated as “extreme” and colour-coded purple. The display is solar powered, making it useful for outdoor sporting events (e.g., tennis, cricket, athletics, etc). We are seeking sponsors to cover the costs of calibrations. The UVI scale was originally used in Canada, where its maximum value was designed to reach 10. In New Zealand, the peak UVI can exceed 13 near midday in summer. Basic units like the one shown here would cost about $3000. We are currently investigating other options including larger versions and double sided versions, and solar powered versions. All units would be offered with the option of an additional maintenance contract, which would include calibration of the display. All units would include the NIWA and Sunsmart logos, but there are spaces for two other advertisers (to effectively pay for the maintenance fee). For more information please contact Dr Richard McKenzie at r.mckenzie@niwa.co.nz with a subject line containing the text “UVI Display”. http://www.niwa.cri.nz/services/free/uvozone/uvi_display Seems like a good idea to me. Who really checks the UV forecast before heading to the beach? To have something there it might perk people's attention to the danger....of course the onus would still be on them to act.

I see "Bandwidth Exceeded - Upgrade to Pro"

Hi all, Today I was looking at the UV index, and apart from thinking "gosh that's high" and I started musing over records, and the effect of altitude. If you look at the first photo, there's a cluster of three mountains at the bottom. The UV index for the nearest town is 13. UVI in NZ tends to be 40% greater than corresponding latitudes in the USA or Europe. This is for clear sky of course. I've also attached a "cloudy sky" UV forecast. I got these from www.sunsmart.org.nz and www.niwa.cri.nz/services/free/uvozone (both free for all). For most areas cloud has not been having much effect. Anyway, one of those cartoony mountains gets up to 2800m* , and at this time of the year, going up there is quite popular for serious climbers. There's also the most popular one-day walk in NZ which gets up to 2000m**, and in mid summer I expect it's like Oxford Street. You can bet your bottom dollar a number of people who go up there are not prepared for any mountain hazards, including high UV...as it is sold as an "easy" walk for everyone to do. So, my question is, what sort of UV are these people exposing themselves to? Is there a simple way of calculating how it changes as you move upwards? Or even just an average approximation would be helpful. eg we can estimate lapse rate in the atmosphere under "normal" conditions to be between 0.6C and 1C....does something similar exist for UV? This comes onto, what is the record UV index ever recorded? Wikipedia claims 17 for Carnarvon, Western Australia. I assume this is a sea level record. For an extreme example, surely if you go up the mountains in the northern Andes, you are going to be hit seriously hard.....even harder than 17 I would guess. Or is there some kind of limiting factor on our planet which prevents the UV increasing without bound? I suppose if we were looking for the place with the highest UV, it would be in the Southern Hemisphere, and at altitude. I would guess at the mountains of New Guinea. Any input appreciated. cheers * Rumour has it that some people still think in "old money". I have looked this up and it is 9200 ft. ** Likewise about 6000 ft

Honestly, I'm not sure those articles were all that technical. The weather forecast itself, yes. But the reports, not really. Yes, they go into more detail than we would expect now on the likes of time and quantity of snowfall, but there's nothing too brain taxing in there. Weather still commands a lot of space in papers now. Frequently a double page spread. We still get detail on temperatures and rainfall, but not in for so many localities. The reports tend to nowadays look at how it has affected people. Sadly, this does mean that space is given to nonsense that some may spout, often along the lines of "we've never had it like this before", without any evidence, other than anecdotal, to back up the claim.

weather.com reports Wellington at 28C, Dewpoint 18C and gusty northerlies. Such temperatures are rare around Wellington harbour, especially at 11AM! Watching Sir Edmund Hillary's funeral, no sign of rain in Auckland yet, though the North of the SI is having heavy rain right now. However, a southerly change is working its way up, only 10C in Stewart Island.

I thought people might take an interest in a general, irregular report on the weather in New Zealand. Obviously, it is summer at the moment, with January being the equivalent of July in the Northern Hemisphere. I often find that in the UK, the perception of NZ's climate can vary quite a bit. Some talk of it as though it's as hot as Australia (that's why they don't serve beer in pints, right?), whilst others are convinced it is more like Scotland- wet, windy, cold. Obviously, both are quite wrong as generalisations. I usually sum it up by saying it's similar to the UK only sunnier, with more reliable summers and milder winters. This is probably true for about 90% of both populations. The recent weather has been mostly fine, with an exceptionally warm and dry November beginning the all too common summer drought for Hawkes Bay farmers. Several areas recorded record November temperatures, along with sunny conditions and very little rain. This was after a generally cold and extremely windy October. December was a fairly average month, and January so far has been mostly anticyclonic. It's a contrast to last year which had a wet and cool November/December (2006) and a slow start to January, all of which ultimately led into a good autumn and a classic Indian summer with May being the warmest ever. If I recall correctly, wellington only reached 14C on New Years Eve 2006, making it one of the coldest in history. The current highest temperature of the summer so far is approximately 35C in Timaru. This is roughly 2/3 of the way down the South Island on the east coast, lying at about latitude 44S. The warmest part of the year is often the first two weeks of February. Climate: I personally find the climate of New Zealand very interesting. I may have been a little belligerent in the past when arguing this, I apologise for my tone in those cases. Without a nearby continent, initially it doesn't seem like there can be much interesting going on. But the topology of the country itself creates its own fun. Extensive mountainous areas, mixed with a maritime climate makes things very exciting at times. Lots of "highland" areas contribute to all-but guaranteed snow in winter for certain localities- something in the region of 70% of New Zealand is between 200m and 700m ASL. The rain shadow effect can be very strong indeed. All who are fascinated by the Pennine Rain Shadow would enjoy the much greater contrast you can find here. New Zealand is fortunate in being able to grow anything that grows in the UK, but also crops that would not really be commercially viable on a large scale in the British Isles, such as olives, grapes, tamarillos, kiwifruit, feijoas and citrus. The capital city, Wellington, has an extremely temperate climate. In an average year, the summer highs will be about 21C and winter highs around 12C. For this latitude, the summers are very cool. Wellington itself is known for the wind. Most often it is from the North, being relatively warm and humid but never uncomfortable. Southerlies are most common in winter and tend to bring rain or squally showers followed by cool, sunny weather. Unfortunately, southerly changes also occur in summer, although they lack any real bite and rarely persist. They tend to lead to highs of 16C-19C. Temperatures rarely exceed 26C under any conditions. The city is clustered around the harbour on a narrow peninsular in close proximity to the extremely windy Cook Strait. Suburbs to the North of the city have a different climate, being in valleys the summer temperature will quite often get over 28C. Recently, whilst the temperature in Wellington city was at a maximum of 23C, just up the valley in the suburb of Upper Hutt it was 32C. The "dividing range", the Tararuas, rise to about 1800m and are known for their appalling weather, with something like 80 fine days per year and frequently getting hit with high winds. To the east, is the Wairarapa, one of the most "marginal" wine growing regions of New Zealand, which is quite a marginal country in itself. The area is quite windswept, and vineyards make great use of all sorts of technology to protect against the wind and dangerous late Spring frosts. Both cold southerlies and hot, dry north westerlies can hit here. For a city that is roughly the antipode of Salamanca in Spain, people may be disappointed by wellington's climate, however it's not all bad. Firstly, there is the beautiful harbour and mountainous backdrop. But, as they say, if you want the views and the sun you must accept the wind. Wellington is New Zealand's sunniest "major" city. In 2007, it hit 2230 hours, which isn't bad considering so many people complain about the weather here. Auckland is New Zealand's largest city and is warmer, more humid and wetter than Wellington. Summer highs are 24C. Winter lows about 14C. It rains a lot in winter, and a fair bit in summer also. January and February tend to be quite muggy, and warm temperatures tend to persist until the end of April. It is rare to see temperatures over 30C, due to the geography of the city. Summer sea breezes often converge from the SW and NE and produce a fair bit of cloud and sun showers. Winter is short and barely warrants the description, unless you live in a typically uninsulated kiwi house. So that'll be one million cold people then. One of the best features of the city are the beaches. Straddling a thin isthmus of land, residents have access to both East and West coast beaches. So, a choice of golden sands and crystal waters or volanic black sand and wild, surf beaches. The water here is quite warm and good for swimming for much of the year. The peninsula to the North is called...Northland and is similar to Auckland only warmer and more humid. This is where the smallest difference occurs between summer and winter temperatures. Warm weather persists until June. Certain regions grow pineapples and bananas. Whangarei (the only city) was the warmest location in New Zealand in 2007, with an average temperature of 16C. People say Northland has only two seasons - dust and mud. Christchurch is the South Island's only major city. It exhibits a stronger seasonal change. Winter highs are about 10C, with cold nights, and summer highs about 22C. Frequently, it will be the warmest of the major cities, due to the foehn wind. The prevailing wind in summer is the NE sea breeze. However, all too often they suffer from the Nor'wester foehn. Anyone who has experienced a wind like this in the world does not need it described, however, the majority of people don't like it! I think it's OK in small doses, for the novelty! The geography of Canterbury (the province of Christchurch) stretches from the sea to the Southern Alps. These stretch to a height of 3800m ASL. On the eastern side lies the MacKenzie country; a dry, relatively flat basin about 700m ASL. It is ringed by mountains on all sides, as further east you come to the Foothills of the Southern Alps, beyond which lie the Canterbury plains. Christchurch lies on the far eastern side of the plains, perfectly in the path of accelerating foehn winds. The mountains are "conveniently" oriented roughly North East-South West, meaning they form a natural barrier to the prevailing westerlies (NZ lies in the Roaring Forties). On the Western side, the Alps, in only 20 miles can fall all the way from 3800m right down to the sea. This gives perfect conditions for tropical-like downpours on the West Coast, which is wetter than most places outside of the tropics, with similar rainfall to Vancouver Island in Canada. Due to this, rainfall can vary by a factor of 20 or more over less than 80 miles. Christchurch is able to get snowfall in some winters, although usually this is reserved for more inland or highland areas. The record high temperature for Christchurch is 42C, and the record low is -7C. The other two "major centres" are Dunedin and Hamilton. Dunedin has a cooler climate again, whereas Hamilton is similar to Auckland but being inland has warmer summers and colder winters. It has recently had quite a warm period, hitting at least 28C for several days in a row. Despite this, most amusingly, Dunedin recorded the highest temperature of anywhere during the winter months (22.4C), which would probably come as a surprise to most New Zealanders! The average summer high in Dunedin is 19C. --- At the moment, high pressure is in charge still, with the orientation giving south easterly winds to many areas. Certain locations get hit relatively hard by this, with Napier only reaching 19C under such conditions, more like a late Spring temperature. Cyclone Funa may have an impact sometime in the week. Daily highs across the country have been varying from 33C in the Bay of Plenty (North facing bay in the NI) to the likes of 14C in Southland. I'm pretty sure there's the odd Kiwi on this forum, hopefully they could add to this and correct my mistakes. The attached image (from www.metservice.com) I found interesting just for the obvious foehn wind effect. 21% humidity, 33C at 4PM with wind from the North west. This is followed by a southerly change. In winter the respective temperatures would be more in the region of 20C-22C in the NW followed by high single-digits in the S. There is a range to the west of Blenheim (Richmond Ranges) which is causing this. It's not very big, gets to about 1800m, and is "the only bit of the North Island on the South Island". I've also pointed out two lesser-known places on the rain radar map. The red blob on the SI is Blenheim, on the NI it is Napier. (Not isolated heavy showers ) The only interest Blenheim holds to British people is that it's the centre of the Marlborough wine industry. So if you've ever had Marlborough Sauvignon Blanc, there you go. Napier is the centre of the Hawkes Bay wine industry, probably not so well known in the UK, unless you're into your Gimblett Gravels. ================================================================================ =============== Jan 21st: Ex bad-girl Funa has made the weather interesting of late. Attached are the 10PM temperatures across NZ. High humidity, high temperatures by day and pretty warm nights, but with very welcome rainfall for certain areas, which have been deprived recently. http://www.metservice.com/default/index.php?alias=warnings Currently, at midnight it is 22C, with a 17km/h North-west wind. On the "media sensationalism" side, we have: Best summer in 10 years? (It's barely started!) Almost continuous 3 week stretch of 30C temps for the South Island....grass no longer growing....sounds lovely. http://www.stuff.co.nz/4365419a11.html

Wellington city, Temperature: 22C Humidity: 86% Wind: N 6kmh^-1 11:20PM Yuck.

NZ going to have strong NW winds and heavy rain tomorrow due to ex-Funa. High humidity and warm temperatures making it fairly uncomfortable. Reports of air temps hitting 30C and dewpoints of 20C in places, with higher dewpoints (up to 23C) and lower temperatures further north. The sooner this thing moves on its merry way and brings back some fresher winds the better!

The view from New Zealand: Metservice say: Situation for all New Zealand issued at 07:42am Saturday 19-Jan-2008 A ridge of high pressure lies over the South Island, and a tropical cyclone Funa just southwest of Fiji moves southwards, giving strong easterly winds over the North Island today and tomorrow. The newspaper forecast today mentioned "some uncertainty" in the track, but likely to move southwards and to the West of New Zealand, and weaken. Then to weaken further as it crosses the central North Island on Tuesday/Wednesday. AFAIK, the SSTs around NZ right now are at a maximum of about 21-22C. Lots of people hoping for rain from this, hopefully it won't be too destructive though.

Have you tasted the water in Bristol? :huh:

I don't know the specifics from a meteorological point of view, but the atmosphere is a highly non-linear system. In fact, pretty much everything in the world is non-linear, but sometimes we can approximate them as being linear. For example, a simple pendulum swinging is non-linear, but due to a fortunate "trick" it can be approximated as a linear system and that model works pretty well. When it comes to the atmosphere, everything is interdependent, basically meaning it's a highly non-linear dynamical system. And it gets even worse. It can't be approximated linearly (please someone correct me if I'm wrong). And also it exhibits a phenomenon known as "chaos". Along with a few other tedious mathematical requirements, this means that a small change in initial conditions can lead to large, and unpredictable results. I wish I could draw a picture to demonstrate this, but essentially, if you imagine a graph which is a straight, diagonal line, that is linear. Now, on the far left side of the graph, imagine that it starts just a little bit higher up. In a truly linear system, you will end up with an identical, parallel line which is just a small bit above the original one. However, for a non-linear case, this very small initial perturbation will not produce a predictable result. It can set the resulting curve plunging low, oscillating down there is seemingly random fashion, then bursting up above the original line, oscillating for a bit more maybe, then going down some more, getting stuck in another pattern, then bursting out of that one. And so on. The other problem is that non-linear systems can very rarely be solved analytically; this means that numerical methods are used. Essentially, this means that the "solution" to the initial problem is still just an approximation in itself, based upon some numerical iteration worked out by a computer.

NZ is moving North along with Australia. I think there's a fair number of fair people (with "English skin" as they put it) over there, but you're right about those who do tan. The tan can persist throughout winter, and by the end of September/ start of October the UV is already hitting about 5 or 6 again. So it makes sense that they can retain darker skin tone. I think about 95% of Maori live on the North Island anyway. UV there is above 10 from November until February, roughly. Though I believe there are few "true" Maori around now, just like most races there has been interbreeding. Interesting one.... I guess we'll never find out! On the note of air quality, some cities issue air pollution warnings in winter and track the air pollution on a daily basis. This is just because of their prevailing local weather conditions and also because open fires are still so common! I've managed to find a weather forecast showing this (attached). You can see the air pollution readings they take at Christchurch. Conveniently, this forecast is for the last day of winter- and it states a total of 13 high air pollution nights for that winter in total. You can also see the effect the main divide of the southern alps has on the weather there. Another danger with the sun in NZ is the relatively low air temperatures. As an example, yesterday Wellington only got to 15C, pretty poor for the time of the year, meaning people may not adequately prepare themselves for sun exposure. (The UV index was 11). I'm not sure I subscribe fully to this argument, as to me it's abundantly clear when my head is getting caved in by the sun, even if it may be cool standing in the shade. But if you are born and raised in such an environment, it's likely that you won't notice how strong the sun actually is. Having a look at this http://www.sunsmart.org.nz/uv-radiation--i...ndex-(uvi).aspx , the sun is currently ranging from 10 in the South to 12 in the North. It's nothing compared to Australia though: http://www.bom.gov.au/weather/national/charts/UV.shtml 16 in Melbourne!

Just to come back to the "quality of light" you mentioned. What, specifically do you mean by this? Actually, I find this an interesting subject in its own right. We all know about the "softness" of the British light, especially apparent at this time of the year. But if you go to NZ in July, you would not be able to judge the season by the light, as it's still very sharp and the colours well-defined. I presume this is what you meant by quality? But, the UV in an NZ winter is still going to be quite low, and the growth of the Nikau may have already shut down for the winter anyway (I don't know this for sure, not familiar with the seasonal growing habits of temperate palms). But since it's UV that is required for photosynthesis, I don't see how an index of 2 (NZ winter) will make that much difference over a UV index of 1 (UK winter). Of course, it's greater (double, I presume?), but they are still both very low and surely not sufficient for any real kind of growth. However, an argument could be made for improved "quality" of light in NZ in summertime, over ours. Again, it really depends on how we define quality. Looking at the UV, there is a study which showed that the UV at an NZ site is approximately 41% greater than at a site of equivalent latitude in the US. Apparently, this relationship also holds true for Europe. The study also claimed roughly a 2% increase in UV for a 1 degree decrease in latitude. Just for a quick estimation, using these figures for the capitals. Wellington is at about 41S, London 51N. Accounting for the latitude difference and the 41% anomaly we end up with a UV difference of 73%. This sounds astonishingly high to me, I hope I did my sums right. As the UV Index scale is apparently not logarithmic (thank God) this would mean, say, for a UV index in high summer in London of 8 we would have Wellington at 13 or 14- assuming the same day, weather conditions etc etc. If this sort of difference persisted for a few months, then I would hazard a guess that it would have a vast effect on the growth of plants. Roughly speaking, Wellington, with a latitude similar to New York City, would have a UV more akin to the Florida Keys, roughly 2000km further south. But this is based on an extrapolation from data taken from latitudes 40N-47N. I've no idea if the relationship remains linear as we approach the tropics. Just to clarify, what I've stated above is just a rough working out based on thin scatterings of knowledge. I don't know enough about plant biology to be sure about my claims of increased growth due to increased UV. For all I know, beyond a certain level it may become a limiting factor. I also just did the UV calculation based on the index itself, not the actual power per unit of wavelength, the information to which I do not have access of course. So getting back to it; there is then the quality of light issue in summertime. Without a scientific basis, and just on personal experience, I believe that UV and QoL are separate entities. Even with an index of only 1 or 2 in winter, on a cloudy day, I always found that it was not possible to look above the horizon without squinting torturously or putting on sunnies. This became a real pain in the I have a problem to be honest. This was independent of the height of the sun or the direction in which I was looking. Hence I believe this QoL does not rely on UV. I suppose it has something to do with fewer particulates and pollution in the air in general, as opposed to the relative lack of O3 the SH is known for. Still, my presumption is that the QoL difference is greatest in winter (as you originally stated). I am not sure if there is such a big difference in summer, although I believe that one does exist. Well, anyway, hope I'm not miles off the mark with what I've said. It's an interesting discussion for sure. You know a heck of a lot more about meteorology and plants than I do so hopefully you can help fill in the gaps in my knowledge!

Doesn't growth stop in winter though? And also, they can grow in places that get no sun in June/July. No, you might be right about this. I remember reading something about how SSTs around NZ had warmed throughout the 20th century, as expected, but in the last decade they have been cooling slowly. So this could link to declining minima, especially on small islands like the Chathams. Ah, I didn't realise they were that closely related. "Nikau" apparently means "Empty cocount". The first polynesian settlers must have been pretty upset! At the moment, their southern limit is maybe 43S, and the country stretches right up to about 34S. If SSTs did continue falling, I think that the groves on the west coast would be more insulated against this as the Tasman Sea is warmer than the Pacific anyway. Are they really classed as an endagered species?