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Messages - Wipneus

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2
Wouldn't 20.74 put it below 2018?

Indeed, I took it from the wrong (sorted) table, 20.74 is for 2017 (lowest value). The corrected value (22.46) is in the post now.

3
The daily volume and volume-anomaly graphs.

4
Fram volume export appears to have been very low in the first half of the month.

5
PIOMAS has updated the gridded thickness data up the 15th of April. My calculated volume for that day is 20.74 22.46 [1000km3]. This is third lowest day-value behind 2017 and 2018.

Here is the animation for April sofar.

FIXED: correct volume

6
Antarctica / Re: PIG has calved
« on: April 17, 2019, 11:47:44 AM »

In my opinion the SW crack (the low left one in Sentinel, the right one in Wipneus' post) has grown, widened and lengthened since then.

PS. these Sentinel Images are from identical orbital positions.


Mostly yes. Here is an animation of a month of Sentinel 1 A/B images showing changes in the other crack as well, less pronounced perhaps.

As a result from the 10m/pix resolution, you must click the image for the better view.

7
Antarctica / Re: PIG has calved
« on: April 14, 2019, 06:36:31 PM »
Very late in the season for an optical image but here it is. With a solar elevation of just 1.45 degrees (IIRC that is just three solar disks), the shadowed cracks are shown in exquisite detail.

Notice that the pair of major cracks are getting accompanied by a couple more to the right. This is a new feature, these new ones are not visible on a similar image 9 days older.

Uploaded in the native 15m/pix resolution, you must click the image for the better view.

9
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 03, 2019, 10:26:57 AM »
Fram volume(!) export was about normal for the month of March. The normals are indicated by the grey line in the background and are harder to see when exports are higher.

10
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 03, 2019, 09:58:01 AM »
Here is the thickness of 31st March, with comparisons with previous years and their differences.

11
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 03, 2019, 09:54:56 AM »
Thanks, Wip. As for the volume graph, I find it hard to discern the 2019 trend line, because of the 2016 trend line (colours are too similar). But could be my eyes or monitor.

Ack. That needs a fix.

13
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 03, 2019, 08:47:09 AM »
Volume and volume-anomaly graphs.

14
Arctic sea ice / Re: Latest PIOMAS update (April 2019)
« on: April 03, 2019, 08:46:07 AM »
PIOMAS  has updated, both the volume as the gridded thickness data.
Volume on 2019-03-31 was 22.218 [1000km3], fourth lowest for the day.

Here is the animation for March 2019.

15
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 26, 2019, 11:56:22 AM »
The Fram export graph shows near normal export figures in Jan and Feb.
Is it possible for you to verify whether Fram export is thinner than previous years according to piomas?

Hi Uniquorn,

I have given this some thought and I'm wondering what it is you really want.

If volume export is less that can be because (not exclusive):

1. Ice thickness is less;
2. Ice thickness unchanged but concentration less.

Would calculating ice area export ( km2/month) answer your question?

16
Arctic sea ice / Re: Latest PIOMAS update (March mid-monthly update)
« on: March 19, 2019, 12:02:38 PM »
The regional daily volume data updated:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

No gridded ice velocity data updated, so no new Fram export data  :'(

17
Arctic sea ice / Re: Latest PIOMAS update (March mid-monthly update)
« on: March 19, 2019, 11:42:32 AM »
Volume and volume-anomaly graphs.

18
Arctic sea ice / Re: Latest PIOMAS update (March mid-monthly update)
« on: March 19, 2019, 11:37:50 AM »
PIOMAS has updated gridded thickness data. Volume calculated from this was 21.95 [1000km3] on the 15th of March. That would be the 7th lowest for the day.

Here is the animation of March until sofar.

20
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 05, 2019, 06:50:14 PM »
The Fram export graph shows near normal export figures in Jan and Feb.

21
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 05, 2019, 06:25:12 PM »
Thickness maps, compared with previous years and differences with those.

22
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 05, 2019, 06:04:49 PM »
Since there was none last month, hre is the animation of Jan-Feb 2019.

23
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 05, 2019, 12:52:46 PM »
Unfortunately the ftp server with the detailed thickness data has not been serving me for some time now. I will look into that..

That's a crying shame :(

Do you have any idea what the problem might be as yet?

Yes, they have moved to https :

old  ->  new
ftp://pscftp.apl.washington.edu/zhang/PIOMAS/data   ->
https://pscfiles.apl.uw.edu/zhang/PIOMAS/data


ftp is of course designed for automated computer data transfer, while https was designed for interactive browsing (with some incidentally downloading).

Looking at the required (wget) trickery to have the same level of automatisation as before.

24
Arctic sea ice / Re: Latest PIOMAS update (March)
« on: March 05, 2019, 08:49:10 AM »
PIOMAS has updated the official volume data. Unfortunately the ftp server with the detailed thickness data has not been serving me for some time now. I will look into that.

Here are the volume and volume-anomaly graphs.

25
Antarctica / Re: Latest GIOMAS/PIOMAS volume data for Antarctica
« on: February 12, 2019, 07:31:27 PM »
Animated GIOMAS Antarctic sea ice thickness, the first forty years...

26
Arctic sea ice / Re: Global sea ice area and extent data
« on: February 11, 2019, 04:16:37 PM »
Following the GIOMAS update here are the update volume and volume-anomaly graphs.

27
Antarctica / Re: Latest GIOMAS/PIOMAS volume data for Antarctica
« on: February 11, 2019, 04:12:44 PM »
GIOMAS data has been updated to 2018-12-31.

I have updated most of the graphs, let me know if there is one that I overlooked.

Even better is that daily data is now available. All the graphs are will have to be modified. It is a huge improvement but will take some time as the amount of data is causing performance problems.

The place for these graphs are (arctic and antarctic):
https://sites.google.com/site/arctischepinguin/home/giomas

A few global (NH+SH) are on the global sea ice page:
https://sites.google.com/site/arctischepinguin/home/global-sea-ice

Attached are Antarctic volume and volume-anomaly graphs




28
Arctic sea ice / Re: Latest PIOMAS update (February)
« on: February 11, 2019, 02:56:03 PM »
PIOMAS has released the official volume data up to the end of January. Unfortunately not the daily gridded data that I use for the animation and some other graphs.

Attached are the volume and volume-anomaly graphs. I tried to do something quick about the "reds problem", still not ideal but looks to me a little better.  If someone knows a source with optimum distinguishing colors for a line-style graphic with 20 or so lines...


29
Developers Corner / Re: Test space
« on: February 06, 2019, 09:49:15 AM »
does not work in ipad (latest ios) either chrome or safari. Sorry

Not happy to hear that Sterks. Unfortunately I cannot test that device myself. What I can do is to find another file that works and compare with mine that does not. 

Are you able to see the mp4's that A-team posted, like in this post (and many others) :
https://forum.arctic-sea-ice.net/index.php/topic,1259.msg138898.html#msg138898

30
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 05, 2019, 06:44:45 PM »
Thanks to all that have tried and responded.

The positive feedbacks gives me confidence that I have nailed a big source of the incompatibility. In short: do not create mp4 files with an odd number of rows.

Cropping the image height from 695 to 694 gives the attached "big" animation:

31
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 05, 2019, 04:25:12 PM »
Lots of people can see the animation within the forum, some have to download first and some have failed altogether.

On my Linux computer Chrome works fine but Firefox does not recognise the movie. I have uploaded a smaller animation that works fine here with both browsers.

Can people that had difficulties give it a try and report?

The post is here:
https://forum.arctic-sea-ice.net/index.php/topic,2558.msg188194.html#msg188194

32
Developers Corner / Test space
« on: February 05, 2019, 04:17:09 PM »
Thread used for testing images/animations. In my case an mp4 animation created with ffmpeg.

This image uses a -pix_fmt yuv420p option.

33
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 05, 2019, 09:32:16 AM »
While waiting for the lastest January data, here is an animation of the full range 1979-2018. Made possible by a recent inclusion of 1979-1999 daily thickness data.

Displayed are thickness data every 5th day to keep the file size relatively limited.

It is coded as an mp4 file, experimental for me, over 13meg in size, see it works for you.


34
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 01, 2019, 08:43:41 AM »
Attached the Fram volume export graph. December export below average.

Also updated regional data files:

https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional-monthly.txt.gz
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

I expect a new PIOMAS update is very near, so I postpone the latest thickness-difference maps.

35
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 01, 2019, 08:20:19 AM »
Here are the volume and volume-anomaly graphs updated to 2018.

36
Arctic sea ice / Re: Latest PIOMAS update (January)
« on: February 01, 2019, 08:18:45 AM »
PIOMAS has updated to 31st December. Both the volume as the gridded thickness data are available. Volume on 31 december was 15.02 [1000km3], 6th lowest for the day (but nearly as low as  2011: 15.01 [1000km3]).

Here is the animation for December last year:

37
Arctic sea ice / Re: Latest PIOMAS update (mid December update)
« on: December 19, 2018, 09:43:01 AM »
The volume and volume-anomaly graphs are updated (and uploaded). Attached.

No ice velocity data, so no updated Fram export graph.

Daily regional volume data uploaded:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz




38
Arctic sea ice / Re: Latest PIOMAS update (mid December update)
« on: December 19, 2018, 08:51:36 AM »
@Wipneus
It seems you gave the new graphs from beginning of November on to Neven, but not on your arctic penguin page, where the last data is from back then.

Thanks, seems I forgot something. Will update it as soon as the new data has been processed.


39
Arctic sea ice / Re: Latest PIOMAS update (mid December update)
« on: December 19, 2018, 08:40:12 AM »
PIOMAS gridded thickness data has been updated, last date 15 December.
Calculated volume at 15 December was 13.07 [1000 km3], which is 6th lowest for the day.
Here is the animation.

40
Arctic sea ice / Re: 2018 sea ice area and extent data
« on: December 18, 2018, 12:12:41 PM »
JAXA ARCTIC EXTENT 11,820,858 km2(December 17, 2018)

Here is the analysis, even though I am still unsure about the 263k gain on 16 December. The 17 December image is complete, and appears to confirm the sudden gain in extent.

Remember that the ADS/NIPR extent figures are two-day averages. The spike occurred on the 16th,  affecting the 15-16 and 16-17 (reported as 16 and 17 th december data) equally. On the 18th the situation will return to normal (hopefully).

My no-average extent calculation from Jaxa SIC jumped a +1010k on the 16th.

41
Antarctica / Re: Sea Ice Extent around Antarctica
« on: December 12, 2018, 12:46:57 PM »
Two simple questions (they could go in the stupid question thread, but are on topic here):

1) Shouldn't there be some minimum % that compaction can reach if it is a ratio of two measurements that are not independent? I'm trying to make sense of how the compaction data over the last two weeks can be so different from previous years. Clearly it has to do with rate of melt; again, you'd think that area can only get so far ahead.

Theoretical minimum is 0.15, for this to be true the maximum concentration in any gridcell is 15%.  Grid cells with concentration less than 15% are neither counted in the area or the extent totals.

Quote
2) Compared to extent, isn't area the better metric for thinking about albedo?

For albedo yes. Here the calculation of area is actually underestimating the true value of melting ice, whetting the surface causing pools, is actually an advantage because those conditions also cause lowering of the albedo.

Quote
Extent seems like it's faster to calculate, but otherwise has no advantages over area.

Extent is much less sensitive to the melting surface. Historic observations where mostly the position of the ice-edge from which only extent can be estimated. Area measurements are only available in the satellite era.


42
Antarctica / Re: PIG has calved
« on: December 09, 2018, 01:08:46 PM »
Detail of some break-up of the latest (September) Calving in this Sentinel 2B shown in native 10m/pix resolution. The preference for square angles is obvious.

43
Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 05, 2018, 03:17:32 PM »
I'm intrigued as well. I guess only Wipneus is qualified enough to explain this discrepancy. As far as I know PIOMAS corrects itself using NSIDC concentration data, and I seem to recall it also cuts off at the 15% threshold, but I could be wrong.

Not much help I am afraid. The assimilation used in PIOMAS is described here:
https://doi.org/10.1175/JTECH1871.1

The assimilation of sea ice concentration (from NSIDC) does not mean it is instantly copied into the model, it is more "nudged" to the measured values. Smaller absolute values of concentration are nudged less than larger values.

The influence on volume, probably the most important output of PIOMAS, is likely small. My favorite glitch is the ice on the SW coast of Greenland, sometimes present when temperatures are well above zero.

And no, there are no 15% cut-offs. Not in my graphs, not in those of the PSC (to the best of my knowledge).

44
Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 04, 2018, 09:28:34 AM »
Thickness map for the 30rd of November, compared with recent years and their diff's.

46
Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 04, 2018, 09:18:18 AM »
The Fram export graph. During the last few days the export has increased noticeable, which I think is visible in the animation above.

47
Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 04, 2018, 09:14:05 AM »
Here is the animation for November.

48
Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 04, 2018, 08:24:05 AM »
PIOMAS data has been updated, both the "official" volume data and graphs as the gridded thickness data.

Volume on 30th November was 11.453 [1000 km3], which is the sixth lowest value for that day.

As I am still downloading the gridded data, we start with the volume and volume-anomaly graphs.

49
Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: November 20, 2018, 09:21:07 AM »
No new Fram export graph, the ice velocity data is missing.

Regional daily volume data updated:
https://sites.google.com/site/arctischepinguin/home/piomas/data/PIOMAS-regional.txt.gz

50
Arctic sea ice / Re: Latest PIOMAS update (December)
« on: November 20, 2018, 09:15:21 AM »
Here are the updated volume and volume-anomaly graphs.

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