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Messages - greatdying2

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1
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: September 04, 2017, 06:08:57 AM »
The extent increases were not due to refreeze. Both large areas are covered in low-concentration foam ice. For the Beaufort-side area, this was the first cloud-free day in several weeks -- probably the clouds interfered with the measurement somewhat. On the Atlantic side, that area only recently dropped below the 15% threshold, and again it may just be clouds messing with at least a few percentage points of concentration. Expect both these areas to drop back off the extent map before true refreeze takes hold.

2
Arctic sea ice / Re: The 2017 melting season
« on: September 02, 2017, 05:48:56 AM »
The first two animations below ...

Terrific, thanks A-Team!

Interesting idea to use the geometric mean for filtering. Seems to work quite well.

3

Man-Made Global Warming:
Based on the long-term average convection/precipitation enhancement from above average temperatures of SST, this probably has made somewhere between a 7% difference and a 10% difference in rainfall totals. However, the previous record would have been smashed even without man-made Global Warming. There is the matter than the mathematics of Hurricanes can sometimes be "chaotic" in which case approximations of the effects of a SST change may not translate 1 to 1 with reality. This will require probably several years of super-computer analysis to figure out exactly what the real "Global Warming Enhancement" percentage really is...

That's not how it works. Means and extremes are completely different things -- that's a critical lesson to learn about climate change. (After all, if everywhere just warmed up 2 C, who would really care...) And computers just crunch numbers, they don't magically learn unknown physics. There is currently no way to know how much AGW contributed to any particular storm because we don't understand the climate system well enough. However, models have long predicted a trend of large increases in maximum storm intensity, which is just what is now coming to pass.

It is quite possible that Harvey would never have even occurred if not for AGW, or if it did, may have had no noticeable impact on the US.

Expect more and worse. I wonder how many "1000-year" events it will take before certain people start to pull their heads out of their ... sand boxes.

The hurricane churned up water 100 or even 200 meters below the surface, said Trenberth, but this water was still warm—meaning that the storm could keep growing and strengthening. “Harvey was not in a good position to intensify the way it did, because it was so close to land. It’s amazing it was able to do that.”

The human contribution can be up to 30 percent or so of the total rainfall coming out of the storm

-- Kevin Trenberth, Senior Scientist at the U.S. National Center for Atmospheric Research
https://www.theatlantic.com/science/archive/2017/08/did-climate-change-intensify-hurricane-harvey/538158/

4
Arctic sea ice / Re: The 2017 melting season
« on: August 30, 2017, 08:10:10 PM »
But weather-forecast.com has a significant system coming into the Arctic from the North Atlantic over the coming days.

Yes, both ECMWF and GFS (both attached at day +4) forecast an Atlantic-side low starting in a few days and persisting for several days. If it comes to pass, this system may clear out the fairly large area of foam (see WorldView), maybe more than just the foam. Also, there is a small low forecast on the Russian side, which may give the Laptev bite (etc.) a little push.

Check out windy.com -- excellent, easy to interpret animations of both these models, updated several times a day. (To view the Arctic, switch to 3D view under Menu | Tools, which is that "3-bars" icon at the top-left of screen.)

@Andir, glad to hear it :)

5
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 30, 2017, 07:42:10 PM »
These data, lets call it "raw" data, show two obvious defects.

Terrific information, thanks!

6
Arctic sea ice / Re: The 2017 melting season
« on: August 30, 2017, 07:26:53 PM »
At this time, The Arctic Sea Ice has a very small volume, but in relation big extent/area . Is my feeling right, that with this constellation the  minimum for extent will be more late this season.

Hi Andir. I think A-Team's response was not directed so much at you but in general -- many people seem to be jumping the gun somewhat in suggesting an end to the melting season. Yes, questions are very welcome. :)

In answer to your question, I think it does seem like a reasonable possibility.

(P.S. In answer to your other question, people often crop posts they are quoting when they only want to respond to one part of it.)

7
Arctic sea ice / Re: The 2017 melting season
« on: August 28, 2017, 07:02:48 PM »
(Sorry for continuing OT...) Anyone who doubts anthropogenically driven climate change at this point doesn't care about even basic data, let alone nuances. Sooner or later (sooner, at the rate things are going), these people will be convinced not by data but by their own direct experience of the weather, and there's nothing the idiot politicians can do to hide that. "Fake weather?"  :o ;D 

8
Arctic sea ice / Re: The 2017 melting season
« on: August 28, 2017, 09:00:11 AM »
Model correction .... or the slippery slope?
The former I think.
Why would you assume anyone at NSIDC would correct any model?

I don't think that's what he meant. I think he was wondering whether the wiggle in the line was just noise cancelling out, or if it reflected a real change in the rate of extent loss.

9
Arctic sea ice / Re: The 2017 melting season
« on: August 28, 2017, 05:26:35 AM »
Welcome TT :)

Nice view of the Atlantic side today. Lots of foam...

10
Arctic sea ice / Re: 2017 sea ice area and extent data
« on: August 27, 2017, 10:04:45 PM »
I think this question has been asked before, but I can't remember the answer-

Obviously there is no ice being gained or lost in the great lakes. So how do they know that the ice is really being gained/lost in more uncertain areas and not just a product of a flawed model?

You don't. However, such noise does not persist, which is why it's best to not look at day-to-day values for this product, but several-day averages (where such noise cancels itself out).

11
Arctic sea ice / Re: The 2017 melting season
« on: August 27, 2017, 02:50:48 AM »
Nice, thanks for those A-Team.

I haven't posted any Bremen maps lately (slow ice and I've been busy), so here's an update: the last 30 days using the 5-day median filter, and the last 10 days using the last-under-90 filter.

As mentioned previously, several areas still look vulnerable in the few weeks remaining (before surface refreeze starts to dominate satellite imagery), including the remaining Beaufort tongue, the Laptev bite, and the area NE of Svalbard. Stay tuned...

12
Arctic sea ice / Re: The 2017 melting season
« on: August 26, 2017, 09:44:08 PM »
I think the earlier speedup and the slowdown were simply caused by weather, stormy on the Pacific side, but more recently, great weather for ice preservation. I guess ice is slow to melt when it just sits in its own meltwater -- needs a bit of stirring.

Now, the weather is starting to moving again. I expect the speedup to continue for a few days at least, somewhat on the Russian side and especially on the Atlantic side, where low concentration ice is about to meet some wind and waves.

A speed-up, at least for today. Ice retreating along the ice edge facing ESS,  in the CAA and near Svalbard.


13
Arctic sea ice / Re: The 2017 melting season
« on: August 24, 2017, 08:43:38 PM »
In addition, these winds will kick the "Garlic Press" into high gear.

Yep. Wipneus has just posted a nice animation on his home brew thread showing how the CAA is now smashed and ready...

Also definitely worth keeping an eye on that big low in the long-term forecast on the Atlantic side. Things may get interesting again soon.

14
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 24, 2017, 08:38:21 PM »
Animation of the Canadian Archipelago.

The garlic is smashed and ready to be pressed, which is forecast to start slowly in about a day and intensify over several days.

15
Arctic sea ice / Re: 2017 sea ice area and extent data
« on: August 24, 2017, 08:25:34 PM »
In addition, a Near-Real-Time NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration (NRT CDR) has been released. The NRT CDR fills the temporal gap between updates of the final CDR, occurring annually, and provides the most recent available data.

"NOAA/NSIDC Sea Ice Concentration CDR" is supposed to be a much improved product over NSIDC's standard sea ice concentration that is used to calculate NSIDC sea ice extent. Unfortunately it was never available near real time, which takes away much of the fun of following the day-to-day fate of the sea ice.

Great! It will be nice to have another (hopefully) stable day-to-day data source next melt season. :)

16
Arctic sea ice / Re: The 2017 melting season
« on: August 24, 2017, 07:12:30 AM »
Meanwhile I received an update today on the wonderful new ESRL forecast page from Dr. Janet M Intrieri, deputy branch chief scientist at NOAA.

Fantastic

17
Arctic sea ice / Re: The 2017 freezing season
« on: August 22, 2017, 10:04:20 PM »
Although the melt has slowed down, particularly surface melt and storm-associated melt due to nice weather, this thread is too soon. OTOH, I'm not sure it even makes sense to have separate melt and freeze threads...

18
Arctic sea ice / Re: The 2017 melting season
« on: August 22, 2017, 09:42:59 PM »
Someone should drop a buoy (or 10) in that polynya to help figure out what's going on.

19
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 22, 2017, 09:27:56 PM »
Quite an amazing stall in both weather (storms) and declines (extent & area). Do the large area fluctuations lately suggest the beginning of refreeze near the pole on some days?

To me, it looks to like various higher concentration arms are still in decline, and my guess is that the Beaufort arm will still melt out completely or nearly so. Also the CAA garlic press may rev up a bit soon. But with continuing nice weather in the forecast I doubt there will be much drama. Although boring, this is a good thing.

One interesting area is south of the Laptev polynya: will a channel form, all the way to open ocean?

20
Arctic sea ice / Re: Latest PIOMAS update (August mid monthly update)
« on: August 19, 2017, 02:29:24 AM »
Thanks Wipneus. A very useful update, as always.

It's worth keeping these in mind. I note that PIOMAS has not corrected the large anomaly near Svalbard -- will this now be perpetuated into the freezing season? I wonder if they are considering updating PIOMAS to assimilate CryoSat data...

21
Arctic sea ice / Re: Stupid Questions :o
« on: August 17, 2017, 09:45:33 AM »
Thanks Oren and Neven.

22
Arctic sea ice / Re: Stupid Questions :o
« on: August 17, 2017, 07:46:48 AM »
Already looked there. Can't find a thread with a posting this year that seems appropriate. And I don't like starting threads just to ask a question.

23
Arctic sea ice / Re: Stupid Questions :o
« on: August 17, 2017, 07:28:58 AM »
Question #1: Is there a way to block comments from specific users, and if so how?

Question #2: What thread do stupid questions like #1 belong in?

Thanks.

24
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 16, 2017, 06:45:04 PM »
It looks to me like the area fluctuations at least in the Laptev bite are due to cloud. The extent drops that Wipneus started to detect there, inside the ice perimeter, should continue and accelerate -- there's a large area of low concentration ice...

25
Arctic sea ice / Re: The 2017 melting season
« on: August 16, 2017, 07:10:52 AM »
Big drops in extent on the Pacific side again. Some also Atlantic and Russian sides, and a big area drop on the Russian side. The frequency and amplitude of area drop episodes on the Russian side are increasing and my guess is that it will start melting out within a week.

Attached Bremen 1 week 5-day 90 filter. See here for explanation and caveats:
http://forum.arctic-sea-ice.net/index.php/topic,2131.0.html .

26
Arctic sea ice / Re: The 2017 melting season
« on: August 14, 2017, 08:01:53 AM »
Pearscot, my take is that the ice is weak, but not so weak yet that breaking records doesn't depend on the weather. Also, the ice may not have been as thin as some models (esp. PIOMAS) predicted, due to the unprecedented weather last winter pushing the model in untested ways. Nevertheless, despite the slow start this season due to deep snow, and despite fairly nice ice-preserving weather, we may be heading for 2nd or even 1st (worst) place in different metrics.

Speaking of which, today's Bremen map (attached, last-under-90 filter) shows that: extent near the Beaufort has not stopped dropping, area in the central pack has recovered a bit after yesterdays big drop (probably noise in both directions), and the ice near Svalbard is starting to get into some serious trouble.

Edit: And the CAA is in trouble too.

27
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 14, 2017, 02:25:40 AM »
To quantify the amount of "artifacts" as you define them in the original image, you need to count the number of pixels your algorithm actually replaced. Those that were replaced by a lower value shall be known as "high concentration artifacts" while those that were bumped up shall be known as "low concentration artifacts".

That would certainly be easy and worthwhile to do. Not sure how it would help in choosing the "best" threshold, but it would be interesting to see the numbers. Note that the last-under-90 filter does not replace any low concentration pixels (but the quartile-based ones do).

28
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 14, 2017, 02:19:51 AM »
For a more realistic estimate, I wonder if it's possible to look at previous years and work out the probability that a pixel with 10%/20%/30%/40%/50%/(etc.) concentration will melt out by the time of the summer minimum, and then apply those probabilities to the current map.

Good idea. I have an idea along those lines too -- using classifiers (machine learning) to categorize pixels as melt / not based on the date, using previous years to train. Probably would use the original data instead of the concentration buckets used for the images. Would expect the classification to become more accurate as the melting season progressed. But no time now, so it's going to have to wait -- unless someone else wants to take a stab at it?

Also, A-team makes a very good point about the limitations of this approach on a pixel basis (as opposed to ice floes), and other problems. Not sure...

29
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 13, 2017, 09:11:53 PM »
Last bit of fun for now -- using the last-under-90 5-day filter, here is all the ice over 90 coloured white and under 90 coloured blue.

(NB: I don't think we will get anywhere close to this unless perhaps there is a late-season GAC, which looks unlikely based on current forecasts. But it's interesting to look at.)

30
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 13, 2017, 08:55:00 PM »
Hmm... it's a good idea to try to quantify that. So far it has just been from eyeballing it -- although backed up by the results, compare for example Q1 vs. Wipneus animation and Q3 vs. the same animation.

To quantify it, we would have to define mathematically what is meant by an artifact, which could be tricky. I suppose I could try to apply some kind of extreme value test... but that would assume that the artifacts only occur infrequently, which may not be true in this case.

Let me think about it and get back to you in a day or two. I don't have a lot of time today to play -- need to study for a job interview tomorrow  ;D .

If you (or anyone) have any suggestions about how to quantify it, I'm all ears.

31
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 13, 2017, 08:47:02 PM »
Looks like serious melting between Franz Josef and Svalbard.

Very much so. And it going to be hit by a storm over the next 2-3 days. I will be surprised if the whole Atlantic side isn't torn to pieces much like the Pacific side has been recently.

32
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 13, 2017, 08:34:34 PM »
Actually, I like Q1. It is basically a not-quite-minimum filter. Does a little smoothing, in regions of active melt is only 1 day "behind", filters out low concentration 1-day artifacts, and filters out high concentration artifacts even if they persist for 3 of 5 days.

Attached is Q1 for the last 2 weeks.

33
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 13, 2017, 08:22:36 PM »
For fun, here are the first (Q1) and third quartiles (Q3). Compare to the median above.

The period is 5 days, so Q1 is the second lowest value and Q3 the second highest. (Median is the third lowest / third highest.)

34
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 13, 2017, 07:12:38 PM »
Wipneus just posted a very useful animation of the basin ice:
http://forum.arctic-sea-ice.net/index.php/topic,382.msg125109.html#msg125109

For me, this re-confirms the usefulness of the last-under-90 filter. Take a good look at the details, all across the basin. The filtered image looks like reality.

The median filter does quite well too, but it is a bit blurry, a bit behind, and I think overestimates the concentrations a bit (because high concentration artifacts are far more frequent than low concentration ones -- I wonder if maybe a quartile filter might work... hmmm).

Attached are the latest full-sized last-under-90 and median filter images (5-day). (I'll leave it to you to guess which is which.)

35
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 13, 2017, 06:59:30 PM »
Arctic Basin animation.

Extremely interesting and useful animation -- thanks Wipneus.

36
Arctic sea ice / Re: What the Buoys are telling
« on: August 13, 2017, 11:06:16 AM »
Sure, of course it doesn't take a straight line. There are changes in wind direction, etc. But I thought you were talking about temperature and salinity trends that seem to be over at least the last 20 to 30 days? Maybe I misunderstood what trends you are talking about.

37
Arctic sea ice / Re: What the Buoys are telling
« on: August 13, 2017, 07:30:18 AM »
I was looking at ITP95.  It appears to me that the buoy is heading north from looking at the drift track. 

Isn't it drifting south (and into shallower waters)?

Latest location (triangle)

38
Arctic sea ice / Re: The 2017 melting season
« on: August 13, 2017, 06:24:19 AM »
Yes Sebastian, it's odd, isn't it? Also, a polynya appeared in the same location in 2012 and 2013. Must be a current.

Attached is the 1-day change (90% filter). Additional serious losses (perhaps area more than extent?) in and north of the Beaufort. Also looks like the Laptev bite may be preparing to recede.

39
Arctic sea ice / Re: The 2017 melting season
« on: August 13, 2017, 01:48:53 AM »
greatdying2: call me crazy, but is there a cloud artifact in your animation or is there actually a chunk of ice migrating in a couple days from the central siberian coast to the bering sea?

Yes, there is strong evidence of a new form of ice that has become airborne and sentient, and plans to recolonize the Earth. Just kidding  :o ;D yes it's a set of artifacts -- same on the original and the last-below-90 versions. One advantage of the median filter is that it eliminates artifacts such as these. (The minimum filter also would eliminate this artifact, but I no longer show it because I think the last-under-90 filter does a better job reflecting reality and is more responsive to day-to-day change.)

A-team -- The change is already impressive. The big question is, will it stop or will the next 2 weeks be as impressive... and nice find on that NOAA site!

40
Arctic sea ice / Re: The 2017 melting season
« on: August 12, 2017, 11:00:09 PM »
Bremen maps, 7 days ending Aug. 11. Original, median filter, last-below-90 filter. (Filters are based on 5 days ending on the labelled day. See previous posts for caveats.)

Pacific side continues to erode and looks like more area is thinning inside the new ice edge, preparing to do the same. But the Pacific side storms seem to be abating (for now), so maybe this thin ice can survive?

Atlantic side -- near-term forecasts suggest that maybe it is finally time for that side to get some bad weather. It will be interesting to see if the ice there is as weak as it has proven to be on the Pacific side.

41
Arctic sea ice / Re: The 2017 melting season
« on: August 10, 2017, 08:23:46 AM »
Bremen 1-week animations: unfiltered, last under 90, median (5 day filter).

42
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 09, 2017, 07:14:06 PM »
It is instructive to compare these different versions with this animation produced by Wipneus:

http://forum.arctic-sea-ice.net/index.php/topic,382.msg124478.html#msg124478

43
Arctic sea ice / Re: The 2017 melting season
« on: August 09, 2017, 07:37:00 AM »
Not to mention, it's getting pounded as we speak. This will be a telling week...

44
Arctic sea ice / Re: Solar wind storms effect on ICE?
« on: August 09, 2017, 07:30:37 AM »
Stupid question: If I post here, does it mean I'm stupid?  :o 8)

45
Arctic sea ice / Re: The 2017 melting season
« on: August 09, 2017, 07:17:30 AM »
1 day change in Bremen concentration. 3 versions attached: Original, last under 90 filter, median filter (5 day period). Choose your poison.

Pacific continues to erode and contract towards the CAA, with anti-clockwise motion in the direction of storm winds apparent throughout the Arctic, as anticipated by Sterks' post above. Such large scale coordinated motion cannot be good for the halocline.

46
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: August 09, 2017, 12:21:57 AM »
It's not cloud. The ridge can be seen in the ice on this Aug 4th image from WorldView. Could it be bands of thicker ice formed originally by ridging that are now moving? Similar patterns also appear in the areas that are melting out inside the ice perimeter.

47
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 09, 2017, 12:03:09 AM »
I forgot, I was going to post a version to show what happens if you select the most recent over 90% instead of under. Here it is (5 days).

Needless to say, this map is not very useful (except in helping to understand artifacts).

48
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 08, 2017, 09:34:18 PM »
These occur after big storms, which are very real. Typically the ice concentration appears to drop sharply immediately after the storm, then rebound somewhat (and afterwards often continue to fall). I am not certain exactly what physical process is reflected in the rebound, but it is a pattern that can be predicted, not random noise.
Storms also have more atmospheric moisture - both as clouds and also just as more humid air.  So this pattern fits with a false low value (caused by cloud / atmospheric moisture) that then goes away as the clouds move, followed by continued decline - because it's melt season.  Personally I think this is the sort of process that ought to be filtered out if we are interested in real melting.

Yes and no. I think different filters are better for different different things. But you make a good argument, so how about this. In future I will post (at least) 3 versions: unmodified, most recent under 90, and median. Then people can look at their favourite, or even better,  compare them and draw their own conclusions.  :)

49
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 08, 2017, 09:29:27 PM »
Edit:  "Most recent under 90" also clearly has a problem in areas where the true concentration is over 90, such as the area around 135W, 85-90N.  You can clearly see a spiral artifact appear over the course of 1-2 August as the core of the weather system passes overhead.  This then leaves a false "deposit" of low concentration pixels that lasts for several days - because the real concentration is over 95% and thus cannot overwrite the false low values.  The artifact is even larger (and just as false) in the "Most recent under 95" animation.  If you look at the Earthdata images in the right wavelengths, you can clearly see that the ice sheet in this region is unbroken and snow covered, at ~100% concentration.
https://go.nasa.gov/2vM23QD

Yes, I agree that this is an artifact. Furthermore, basically all of the "yellow streaks" in the "large purple area" are artifacts (as I suggested above).

Luckily, these are easy to see and to ignore. And besides, they are not in an area of much interest -- unless someone thinks a polynya might be forming here. The main purpose of these filters is to better watch the evolution of marginal ice zones during the melt season without being distracted by frequent cloud artifacts.

50
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 08, 2017, 09:21:06 PM »
Most recent under 90% (5 days).

Compared to the median version above, this version does a better job at showing daily changes, for example the alternating loss and recovery cycle ("breathing") on the Pacific side

What is your basis for believing this apparent cycle (i.e. where an unusually high/low value goes away the next day) is real, and therefore this filter is better?  There seems to be no plausible physical mechanism that would cause it. On the contrary, this is exactly what you expect from random noise. Large excursions away from the true value will typically revert towards the mean the following day.

These occur after big storms, which are very real. Typically the ice concentration appears to drop sharply immediately after the storm, then rebound somewhat (and afterwards often continue to fall). I am not certain exactly what physical process is reflected in the rebound, but it is a pattern that can be predicted, not random noise. As I said in an earlier post, it's clearly not "real" in the sense that new ice is not forming, but as a guess it may result from ice that has been drenched in waves drying out and thus is useful to detect. If it was just random noise, the timing wouldn't coincide with storms.

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