Arctic Sea Ice : Forum

Cryosphere => Arctic sea ice => Topic started by: JimboOmega on July 11, 2016, 09:16:57 PM

Title: HYCOM vs ASMR2 Imagery
Post by: JimboOmega on July 11, 2016, 09:16:57 PM
So looking at HYCOM (which I know some have questioned) and the DMI's ASMR2 imagery... there's a big difference.

HYCOM's nowcast shows a large area of  green-to-yellow concentration (40-60%) stretching from the ESS almost to the north pole, with it being thinnest closer to the pole.  ASMR2 shows nothing of the sort - purples (and thus 90%+) almost the whole way.

Why would the "nowcast" of HYCOM show that? I get why the model could have errors in forecasting - but "now"?  Is it simply crazy? Or is there a weakness in the ASMR2 imagery?

Title: Re: HYCOM vs ASMR2 Imagery
Post by: Neven on July 11, 2016, 09:56:49 PM
The likelihood that a model used by one organisation is flawed is higher than that of a satellite passive microwave product that is used by multiple organisations. The model has been wrong before (last year was crazy) and there is absolutely nothing wrt weather conditions that could explain what the model is showing. And if SSTs were running that super hot, my guess someone would have noticed by now too. We know volume can't be that low that ice simply melts in the middle of the pack because CryoSat-2 reported initial ice conditions.

So, I think that ice pack diverging weather is exaggerated by the model.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Michael Hauber on July 11, 2016, 11:21:46 PM
I say there is no way that the ice concentration is higher in the Beaufort (https://worldview.earthdata.nasa.gov/?p=arctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2016-07-10&v=-1989237.0607318901,107080.27861561405,-1289845.0607318901,423496.27861561405) region than in the central Arctic just to the Alaskan side of the NP (https://worldview.earthdata.nasa.gov/?p=arctic&l=VIIRS_SNPP_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,Reference_Labels(hidden),Reference_Features(hidden),Coastlines&t=2016-07-10&v=-717772.7225537151,-243568.19483383105,-18380.72255371511,72847.80516616895) as Hycom is showing
Title: Re: HYCOM vs ASMR2 Imagery
Post by: JimboOmega on July 11, 2016, 11:54:36 PM
The likelihood that a model used by one organisation is flawed is higher than that of a satellite passive microwave product that is used by multiple organisations. The model has been wrong before (last year was crazy) and there is absolutely nothing wrt weather conditions that could explain what the model is showing. And if SSTs were running that super hot, my guess someone would have noticed by now too. We know volume can't be that low that ice simply melts in the middle of the pack because CryoSat-2 reported initial ice conditions.

So, I think that ice pack diverging weather is exaggerated by the model.

Well, where does HYCOM come from? I assume that they feed it in baseline information from.... something? 
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 12, 2016, 12:02:08 AM
AMSR was missing two days of data (the 8th and 9th), so it is not quite obvious but many of those purples are masking deficits (and on the other side, I believe some of the greens closer to the CAA are melt ponds/rain).

With clouds masking the melt over the area in discussion I would wait another day or two for legitimate obs and then compare.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Richard Rathbone on July 12, 2016, 12:19:07 AM
That's not the nowcast, thats a forecast for a week's time.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Metamemesis on July 12, 2016, 12:25:28 AM
So looking at HYCOM (which I know some have questioned) and the DMI's ASMR2 imagery... there's a big difference.

HYCOM's nowcast shows a large area of  green-to-yellow concentration (40-60%) stretching from the ESS almost to the north pole...

The date for HYCOM's model is for this time next week, so it's at least 8 days ahead of the ASMR2 map from yesterday. I've been taking a look at the wind forecasts (from multiple models) and they seem to show sustained wind across huge swathes of the CAB which I think will do some very interesting things to some of the concentration maps and area/extent numbers. This is particularly so where it looks like the wind will be shunting a lot of the floes/ice into the warm water around the Beaufort.

That's not to say I think HYCOM will prove accurate, but there does seem to be a lot of mobility in the ice pack atm, due to it's (relatively) fragmented nature and (relatively) high levels of dispersion. Let's see where we are next week...

DMI is showing those very high SSTs as well as the NCEP SST maps.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: seaicesailor on July 12, 2016, 12:31:38 AM
http://hycom.org (http://hycom.org)
It is a data assimilation and simulation tool for oceans. Can be used by many and tailored to different problems.
The problem is when you put an ice model on top and couple it with the ocean model. The NAVY models are very attractive because it is the only product out there that tries to predict the ice evolution in one week, with partial success I would say.

By the way, the glb version has definitely lost it. 10 50 cm in the nicely closed Laptev and 2 m in Beaufort.
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html (https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: seaicesailor on July 12, 2016, 12:38:00 AM
So looking at HYCOM (which I know some have questioned) and the DMI's ASMR2 imagery... there's a big difference. ...
ASMR2 shows nothing of the sort - purples (and thus 90%+) almost the whole way.
...
What AMSR2 shows is a big front from Siberia that, if forecasts realize, will further advance.
The ACNFS is not picking what observations make evident
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 12, 2016, 01:27:47 AM
So looking at HYCOM (which I know some have questioned) and the DMI's ASMR2 imagery... there's a big difference.

At the risk of repeating myself (http://forum.arctic-sea-ice.net/index.php/topic,1493.msg83076.html#msg83076), have you ever considered eyeballing MODIS? There's a big difference!
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Nick_Naylor on July 12, 2016, 01:29:03 AM
Here's the actual nowcast. It still has some 'splainin' to do.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 12, 2016, 03:06:58 AM
This looks pretty accurate, IMO.

https://twitter.com/ZLabe/status/752603452505624576

Title: Re: HYCOM vs ASMR2 Imagery
Post by: Richard Rathbone on July 12, 2016, 12:45:14 PM
Here's the actual nowcast. It still has some 'splainin' to do.

I'm amazed they can have the concentration so low in that central region in the nowcast. Their data assimilation should be stamping on that even if the model has a tendency to hollow itself out. 50% concentrations where the minimum they can assimilate is 70%. They have to be virtually ignoring the data.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 12, 2016, 12:56:47 PM
This looks pretty accurate, IMO.

What's your (humble?) opinion about the prettiness and accuracy of this?

http://youtu.be/nF2DQv7qCXY (http://youtu.be/nF2DQv7qCXY)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: plinius on July 12, 2016, 04:02:25 PM
I'm amazed they can have the concentration so low in that central region in the nowcast. Their data assimilation should be stamping on that even if the model has a tendency to hollow itself out. 50% concentrations where the minimum they can assimilate is 70%. They have to be virtually ignoring the data.

Not the first little issue with that model, but just assume that they are assimilating melt ponds as low concentration. Just like NSIDC underestimates the real sea ice area.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Richard Rathbone on July 12, 2016, 04:28:36 PM
I'm amazed they can have the concentration so low in that central region in the nowcast. Their data assimilation should be stamping on that even if the model has a tendency to hollow itself out. 50% concentrations where the minimum they can assimilate is 70%. They have to be virtually ignoring the data.

Not the first little issue with that model, but just assume that they are assimilating melt ponds as low concentration. Just like NSIDC underestimates the real sea ice area.

They could underestimate 90% ice as 75% due to melt ponding, but not 45%. The minimum non-zero concentration assimilated is 70%.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: JimboOmega on July 12, 2016, 04:44:42 PM
Here's the actual nowcast. It still has some 'splainin' to do.

I'm amazed they can have the concentration so low in that central region in the nowcast. Their data assimilation should be stamping on that even if the model has a tendency to hollow itself out. 50% concentrations where the minimum they can assimilate is 70%. They have to be virtually ignoring the data.

Exactly what I started this thread to ask! :)

Where does their data come from? Do they use some weird (non-microwave?) input?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: plinius on July 12, 2016, 06:06:44 PM
They could underestimate 90% ice as 75% due to melt ponding, but not 45%. The minimum non-zero concentration assimilated is 70%.

I can neither see any backing for your first sentence (I have seen lower than 75% conc. estimates on perfectly solid, 100% coverage coastal fast ice; nor do I understand your second sentence.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Richard Rathbone on July 12, 2016, 07:49:14 PM
Here's the actual nowcast. It still has some 'splainin' to do.

I'm amazed they can have the concentration so low in that central region in the nowcast. Their data assimilation should be stamping on that even if the model has a tendency to hollow itself out. 50% concentrations where the minimum they can assimilate is 70%. They have to be virtually ignoring the data.

Exactly what I started this thread to ask! :)

Where does their data come from? Do they use some weird (non-microwave?) input?

They have a product customised for them. There was some discussion of it on the forum earlier this season when NSIDC made it publically available. One part of it is people looking at pictures (which they use to judge if there is actually ice there or not) and one part of it is microwave (which they use to set a concentration if there is ice, but the lowest value they set is 70%). NSIDC is out of action for a server upgrade right now, but the description of it is on their site and should be back in a day or two.

Title: Re: HYCOM vs ASMR2 Imagery
Post by: Nick_Naylor on July 13, 2016, 01:31:02 AM
Here's the actual nowcast. It still has some 'splainin' to do.

Actually, I may have been too hard on HYCOM. Here's a comparison of the nowcast vs. worldview. Yellows are about 60% concentration. Not so far off at all really.
[edit: image needs a click]
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 13, 2016, 01:44:06 AM
Here's the actual nowcast. It still has some 'splainin' to do.

Actually, I may have been too hard on HYCOM. Here's a comparison of the nowcast vs. worldview. Yellows are about 60% concentration. Not so far off at all really.
[edit: image needs a click]

Clouds have been in the way but if HYCOM is actually right it would be disturbing. But I don't think it is far off, and when we do get glimpses underneath, the leads are always getting larger.

This also explains why June's melt pond fraction was off (as discussed in the other thread). The areas where it has 'decreased' vs 2012 are those that have since been completely fractured. The entire picture has changed since that season and while I have taken lots of flack I will stand by my prediction that we are heading for sub-1M KM2 come September (or early October).
Title: Re: HYCOM vs ASMR2 Imagery
Post by: philiponfire on July 13, 2016, 07:51:44 AM
I find that the U Hamburg graphical presentation of the data is the most easily reconcilable with Eodis. It is like Eodis without the clouds.
I look at U Hamburg and then go for verification of what is peeping through the clouds.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 13, 2016, 10:25:34 AM
I look at U Hamburg and then go for verification of what is peeping through the clouds.

As you may have gathered, so do I.

Quote
It is like Eodis without the clouds.

I don't think it's quite that simple. University of Hamburg AMSR2 still suffers from "weather" and "melt pond" artifacts. I start to get interested if a "low concentration" area hangs around for a few days. A lot of first year ice is starting to look decidely ropey, but what about the multi-year ice? I have yet to see any evidence from MODIS (http://greatwhitecon.info/resources/arctic-sea-ice-images/summer-2016-images/#CAB) to suggest that the bright yellow areas on Bremen AMSR2 imagery are anything more significant than melt ponds.

Am I missing something?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 13, 2016, 10:29:48 AM
I will stand by my prediction that we are heading for sub-1M KM2 come September (or early October).

Do you still stand by your assertion (http://greatwhitecon.info/2016/07/has-the-ice-clearly-broken-completely-in-two-now/) that "The ice has clearly broken completely in two now"?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: plinius on July 13, 2016, 11:58:20 AM
I have yet to see any evidence from MODIS[/url] to suggest that the bright yellow areas on Bremen AMSR2 imagery are anything more significant than melt ponds.
Am I missing something?

Well, after trying to cross-identify some of those, I think at least some of the lower concentration areas in the CAB are not melt ponds, but dispersed ice. I would fully agree, though, with your assertion that they are not more significant than melt ponds. It's just local divergence that happens every year (and probably less impactful than melt ponds/even helping to cool the air a bit).
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 13, 2016, 02:42:35 PM
I will stand by my prediction that we are heading for sub-1M KM2 come September (or early October).

Do you still stand by your assertion (http://greatwhitecon.info/2016/07/has-the-ice-clearly-broken-completely-in-two-now/) that "The ice has clearly broken completely in two now"?
No, structurally it has actually now broken into three pieces, one is attached to the islands N of Siberia/NE of Svalbard, one is near Wrangel/ESS, and the "bulk" is pushed against the CAA/Greenland.

The lower concentrations in CAB are clearly open water and not melt ponds...
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 13, 2016, 03:13:54 PM
The "bulk" is pushed against the CAA/Greenland.

So the "gaping fissures that span from Siberia to Canada" have miraculously vanished?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 13, 2016, 06:12:57 PM
The "bulk" is pushed against the CAA/Greenland.

So the "gaping fissures that span from Siberia to Canada" have miraculously vanished?
They are under clouds right now, I've screen grabbed many times and you keep ignoring me. Go look at HYCOM etc.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: philiponfire on July 13, 2016, 06:44:25 PM
I came across the U Hamburg plots back in 2013 and very quickly abandoned the U Bremen plots as being far less useful to the point of being irrelevant. the colour changes just don't make sense (they are not sensitive enough) whereas after 4 years of studying them I am happy with what the different shades and textures of blue mean on the U Hamburg plots. Continuous fast ice that is going to break up shortly is a different blue to CAB dispersed ice (which will probably disappear or migrate as the dispersal gets moved by the wind) which is different to polynyas and so on. the colours represent different kinds of ice rather than purely representing concentration changes.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: magnamentis on July 13, 2016, 06:53:14 PM
The "bulk" is pushed against the CAA/Greenland.

So the "gaping fissures that span from Siberia to Canada" have miraculously vanished?
They are under clouds right now, I've screen grabbed many times and you keep ignoring me. Go look at HYCOM etc.

not really, its' once more all about terms like each time before, basically, and you know share your generel views, you pay not the price for the wording which we were talking about earlier. for example:

possibility a) gaping fissures, cleavage, disconnected

possibility b) (area) band of very vulnarable ice, band (area) of thinner ice, band (area) of increasingly fragmented ice

i really like your way of looking at the big picture but then with extreme terms one will always polarize
the reminder of the readers and at the end the discussion is over terms and get's heated while, once
talking the real thing and brought to therms that most users can agree upon, there would be (is) widely spread
agreement.

like you i'm a straight forward talker and often prefer heavy words instead of lengthy explanations which is
why i on one hand understand you well and know exactly how this happens.

finally after recent happenings (exchange of not so nice words) one has to give waves time to dissipate and
just stay put till all is calm. i hope this comes across the postive way it' is meant.

BTW, who is handing out hast to be ready to take some bashing, payback time so to say :-)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 13, 2016, 06:59:36 PM
You keep ignoring me.

Oh no I don't!

Quote
Go look at HYCOM etc.

I've seen HYCOM. It's just above.

a) I don't trust it

b) Even if I did I still don't comprehend what you're talking about

c) I trust Hamburg AMSR2 rather more, as explained just above. It sees through clouds, after a fashion, so perhaps you could  show me the  "gaping fissures" of which you speak on there?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 13, 2016, 07:45:14 PM
You keep ignoring me.

Oh no I don't!

Quote
Go look at HYCOM etc.

I've seen HYCOM. It's just above.

a) I don't trust it

b) Even if I did I still don't comprehend what you're talking about

c) I trust Hamburg AMSR2 rather more, as explained just above. It sees through clouds, after a fashion, so perhaps you could  show me the  "gaping fissures" of which you speak on there?

illustrated... if you did not know, Canada owns the islands NE of AK (known as 'Nunavut')

Title: Re: HYCOM vs ASMR2 Imagery
Post by: Darvince on July 13, 2016, 08:01:42 PM
Could you maybe chill?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 13, 2016, 08:05:30 PM
Could you maybe chill?
I have left Jim Hunt alone yet he keeps following me through threads and asking the same question over and over to which I provide an answer (with visual evidence) every time. Was there any anger in my reply?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Tigertown on July 13, 2016, 08:10:07 PM
All the SST maps are showing warm waters coming in the Bering Strait and the shore at the Mackenzie Delta and open waters there within the general area. If some many models are showing lower concentrations in the Gyre area, why is it so hard to believe warm water is getting into the Gyre and circulating around.Again, its not going to show up on anything because the energy is going into melting ice. And that being regardless of whatever further insolation is taking place. It is not cloudy everywhere all the time.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Tigertown on July 13, 2016, 08:11:53 PM
Could you maybe chill?
I have left Jim Hunt alone yet he keeps following me through threads and asking the same question over and over to which I provide an answer (with visual evidence) every time. Was there any anger in my reply?
No, you did great
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Lawrence Martin on July 13, 2016, 09:05:05 PM
@bbr2314   @Tigertown

Could you please tone down the trolling a bit?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: JimboOmega on July 13, 2016, 09:19:28 PM
You keep ignoring me.

Oh no I don't!

Quote
Go look at HYCOM etc.

I've seen HYCOM. It's just above.

a) I don't trust it

b) Even if I did I still don't comprehend what you're talking about

c) I trust Hamburg AMSR2 rather more, as explained just above. It sees through clouds, after a fashion, so perhaps you could  show me the  "gaping fissures" of which you speak on there?

illustrated... if you did not know, Canada owns the islands NE of AK (known as 'Nunavut')

So the uni-bremen ASMR2 and the one posted... uni-hamburg ASMR2? Are two different visual representations from two german universities of the same data?

Outside the lines you added, especially on the Pacific side of the pole, there is a big area of weakness that just doesn't consistently show up on Uni-Bremen ASMR2.

It greatly complicates matters (to me) if it's not just Hycom and its complicated data assimilation.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Tigertown on July 13, 2016, 10:25:11 PM
@bbr2314   @Tigertown

Could you please tone down the trolling a bit?
More name calling. bbr complied by not doing that anymore, why is it ok for other people. If you have an idea or something feel free to express it. No one is trying to suppress your views. Please reciprocate.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 13, 2016, 10:56:18 PM
illustrated...

Thanks for that information. I think I've got it now. Rather than the "industry standard" cut off of 15% sea ice concentration for "gaping fissures" for reasons known only to yourself you prefer to use 95% instead?

Quote
if you did not know, Canada owns the islands NE of AK (known as 'Nunavut')

In case you did not know, Canada also "owns" Nunatsiaq. Here's the latest Canadian Ice Service map (http://iceweb1.cis.ec.gc.ca/Prod/page3.xhtml) of the area:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fice-glaces.ec.gc.ca%2Fprods%2FWIS56SD%2F20160711180000_WIS56SD_0008957663.gif&hash=caeedb47ca44d1ad7c4c30644b55e330)

and here's the NSIDC's view (https://nsidc.org/data/seaice_index/) of those "gaping fissures" of yours:
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Neven on July 13, 2016, 11:50:02 PM
Guys, why don't you make notes of what the other is saying, leave this be for a few weeks, and then we'll see how things look. It's the slowest horse race in the world, so we have to exercise patience.

But HYCOM isn't accurate.  ;) ;D
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 14, 2016, 12:02:30 AM
Guys, why don't you make notes of what the other is saying

I've already done that (http://greatwhitecon.info/2016/07/has-the-ice-clearly-broken-completely-in-two-now/) Neven.

Do you recall Snow White's "little black book"?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 14, 2016, 01:22:44 PM
So the uni-bremen ASMR2 and the one posted... uni-hamburg ASMR2? Are two different visual representations from two german universities of the same data?

In brief, yes.

At greater length, here's a recent academic paper on the trials and tribulations of using passive microwaves to work out sea ice concentration:

"Inter-comparison and evaluation of sea ice algorithms: towards further identification of challenges and optimal approach using passive microwave observations (http://www.the-cryosphere.net/9/1797/2015/tc-9-1797-2015.pdf)"

Quote
Sea  ice  concentration  has  been  retrieved  in  polar  regions  with  satellite  microwave  radiometers  for  over 30  years.  However,  the  question  remains  as  to  what  is  an optimal  sea  ice  concentration  retrieval  method  for  climate monitoring. This paper presents some of the key results of an extensive algorithm inter-comparison and evaluation experiment. The skills of 30 sea ice algorithms were evaluated systematically over low and high sea ice concentrations.

The Bremen & Hamburg visualisations are both derived from AMSR2 data (https://climatedataguide.ucar.edu/climate-data/sea-ice-concentration-data-amsr-e-amsr2-ssmis-u-bremen-and-u-hamburg-asi-algorithm) using the Arctic Radiation and Turbulence Interaction Study (ARTIST) algorithm. However the Hamburg version interpolates brightness temperatures on a 3.125 km grid (ASI-3k) instead of Bremen's 6.25 km grid (ASI-6k). See:

ftp://ftp-projects.zmaw.de/seaice/AMSR2/README.txt (http://ftp://ftp-projects.zmaw.de/seaice/AMSR2/README.txt)

Here's another relevant paper in the current context:

"Influence of melt ponds on microwave sensors' sea ice concentration retrieval algorithms (http://www.seaice.de/Roesel_IEEE_2012.pdf)"

Quote
MODIS melt pond fractions can be used to estimate the influence of melt ponds on the sea ice concentration determination from microwave sensors like AMSR-E. In this example, all AMSR-E algorithms are clearly underestimating MODIS sea ice concentration by around 20-30%.

Title: Re: HYCOM vs ASMR2 Imagery
Post by: bbr2314 on July 14, 2016, 04:53:55 PM
<snip Neven: I'm fed up with the personal insults because a model that has a history of errors is showing something spectacular that no other data source does.  Come back in a month if you still feel like it.>
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 14, 2016, 08:20:37 PM
I think there is something seriously wrong with you,

What's wrong with me is that I don't much care for the way in which the signal to noise ratio in several of the threads here on the ASIF is tending asymptotically towards zero.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 15, 2016, 12:50:06 AM
ktonine enquires elsewhere (http://forum.arctic-sea-ice.net/index.php/topic,230.msg83635.html#msg83635) re ACNFS:

Quote
Has anyone actually posted any evidence that it's an apples to oranges comparison?  Is it apples to oranges?  Is it apples to apples? Is it oranges to apples? I.e., does this version yield a warmer, cooler, or equal temperature arctic?

I see an assumption based -- apparently -- on different version numbers, but no qualification, much less quantification of any real differences.

It's already past my bedtime, so for now I'll just plagiarise sedziobs (http://forum.arctic-sea-ice.net/index.php/topic,1493.msg83578.html#msg83578):
Quote
HYCOM nowcast and one-day forecast.  Notice how the Laptev opens up and Baffin crashes in just one day, and the Kara and Atlantic front is covered with thin ice.  Clearly there are some issues.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww7320.nrlssc.navy.mil%2FhycomARC%2Fnavo%2Farcticictn%2Fnowcast%2Fictn2016071318_2016071300_042_arcticictn.001.gif&hash=0f1b9f697965768f395bddde8c27ddd4)

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww7320.nrlssc.navy.mil%2FhycomARC%2Fnavo%2Farcticictn%2Fnowcast%2Fictn2016071318_2016071400_042_arcticictn.001.gif&hash=f23aff070c90e0a2f0694c209e16b195)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 15, 2016, 01:00:58 PM
Here is the ACNFS 1 day concentration forecast for yesterday:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww7320.nrlssc.navy.mil%2FhycomARC%2Fnavo%2Farcticicen%2Fnowcast%2Ficen2016071318_2016071400_042_arcticicen.001.gif&hash=17e9b957028e295b654bc15647230a5c)

However for some strange reason the Kara Sea didn't suddenly become covered in sea ice yesterday:

http://GreatWhiteCon.info/2016/07/has-the-ice-clearly-broken-completely-in-two-now/#Jul-15 (http://GreatWhiteCon.info/2016/07/has-the-ice-clearly-broken-completely-in-two-now/#Jul-15)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: FishOutofWater on July 15, 2016, 05:51:42 PM
HYCOM is good for entertainment but the nowcast and forecast parts are alternate realities. Folks shouldn't take this stuff seeriously.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 15, 2016, 10:06:39 PM
HYCOM is good for entertainment but the nowcast and forecast parts are alternate realities.

I enquired about the issue (https://groups.google.com/a/hycom.org/forum/#!topic/forum/fpNk_nwoeJw) on the Hycom forum, and according to Alan Wallcraft:

Quote
We now use the National Ice Center's IMS sea ice extent product in our assimiltion, see http://www.natice.noaa.gov/ims/. (http://www.natice.noaa.gov/ims/.)  This is manually produced every day, and generally avoids the artifacts and deficiencies of satellite sea ice concentrations.  However yesterdays IMS fields were not good, and that is where the spurious sea ice came from.  Today's IMS field is good, and we may rerun the 2016/07/13-18Z nowcast/forecast to clear this up.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Neven on July 15, 2016, 10:47:15 PM
Thanks for asking, Jim. I didn't even know there was a Google Group for Hycom. I suppose they can't make pronouncements on the cleavage, etc.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 15, 2016, 10:59:10 PM
I suppose they can't make pronouncements on the cleavage, etc.

I've asked a supplementary question, but I didn't phrase it quite like that!
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Neven on July 15, 2016, 11:41:16 PM
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fvignette3.wikia.nocookie.net%2Fdisney%2Fimages%2Fd%2Fdb%2FBashful_Blushing.jpg%2Frevision%2Flatest%3Fcb%3D20141217042642&hash=efbbeac323ae2971d0a10927e1ae099e)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on July 19, 2016, 11:25:37 PM
My supplementary question (https://groups.google.com/a/hycom.org/d/msg/forum/fpNk_nwoeJw/66CoyaR0CwAJ) on the HYCOM forum has received the following answer:

Quote
I attach the ACNFS plot you referenced and the corresponding plot from our next global real-time system (GOFS 3.1), which will likely replace our current global analysis (and ACNFS) once NAVGEM 1.4 is operational (it is running here with NAVGEM 1.3, like ACNFS).  They assimilate the same observations, but ACNFS only does so near the ice edge while GOFS 3.1 assimilates sea ice concentration everywhere (but with higher error bounds in the ice interior).  The reason for ACNFS only assimilating near the edge is in part due to that being the most important area for navigation but also because SSMI satelite ice concentrations tend to "over saturate" in the summer.  We switched GOFS 3.1 to "believe" the observations because they are generally better in recent years.

The two are quite different in the interior of the sea ice and GOFS 3.1 is certainly better there.  We did not see the low concentrations near the North Pole in ACNFS this time last year, so something has happened to make the free running model produce low concentrations this summer.  We are looking into it.

Title: Re: HYCOM vs ASMR2 Imagery
Post by: Neven on July 20, 2016, 12:31:06 AM
Thanks for spending time to confirm something we already suspected, Jim. I hope that puts an end to the usage of ACNFS maps that are out there somewhere on their own.

For this year.  ::)
Title: Re: HYCOM vs ASMR2 Imagery
Post by: seaicesailor on July 20, 2016, 01:30:08 AM
Thanks for spending time to confirm something we already suspected, Jim. I hope that puts an end to the usage of ACNFS maps that are out there somewhere on their own.

For this year.  ::)

I know it is very much questionable but I find ice drift gives reasonable information, if one reads them with caution, and away from the divergence centres and squall lines where the absurd holes appear.
Note that when the ACNFS predicts a hole, real ice concentration in CAB eventually diminishes in fact, the problem is you don't know where, and never it does to that exaggeration.
So even when I criticize it so much, one can get certain indications from it
The ice edge dispersion or compaction is also predicted. Again, maybe with questionable accuracy, but at least you know when to expect extent stalls or losses.

The validity of the SST and SSS maps out of the ice is still not challenged, nor supported here.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: A-Team on July 20, 2016, 07:47:51 AM
Quote
hope that puts an end to the usage of ACNFS maps
I like Hycom myself. Nobody in their right mind ever single-sources information to begin with. We have a plethora of independent resources at our fingertips to synthesize and check for consistency.

It is a very decent project in some ways. For example, where else do you see a responsive export forum like Hycom (just look at the technical sophistication of some of their answers)? Answer: other sites never get back to you, never fix valid bugs you report, never implement easy suggested improvements, never fix broken files, or have a PR rep pat you on the head and pretend to forward your question on to a specialist whose contact information you are never given.

Where else do you see ongoing product development? The Hycom products are imperfect but they are very active in trying to improve them. I mostly see projects on autopilot, ghost ships that sail the same old seas long after the PI has passed on. Meagre documentation and no one left who could write it.

Mostly though I like the visionary aspects of the animations. They've built a very nice container so it's already in place to hold improved product. Even if the Hycom data is ultimately wrong, their representation of it is still very effective, whereas science communicated poorly is just those trees falling silently in the forest.

Where else is anyone even making a stab at predicting 2D sea ice conditions? Nowhere, they are all looking at today or analyzing the rear view mirror. It's from venturing predictions that you find out where and why your theories go wrong.

Why do we have fix so many maps and make so many animations? Because so many projects are too damn lazy or incompetent to offer and archive them. People just going thru the motions at work: they won't spend ten minutes making a fix if the time can't be billed to a grant.

I was looking around today for some basic July-Sept 2012. Modis has it but never got around to reprocessing it to the consensus projection, meaning there's no land mask or co-registration. AMSR2 3k started up in 2013. But there's Hycom with everything imaginable archived and indexed. And some of it, like the ice edge position and off-ice surface salinity and temperature, is   decent enough.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Neven on July 20, 2016, 09:14:32 AM
I don't have a problem with ACNFS per se (on the contrary),  but with a certain kind of usage of ACNFS. And then the persistence of that usage, and all the misunderstandings and conflicts this then produces. It sucks energy out of the Forum.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: FishOutofWater on August 01, 2016, 12:16:07 AM
HYCOM is teaching us all about the live ongoing development of scientific models. Some people are learning the hard way about how to use a model in the process of being tested and improved but I think it is a great way to learn about science
Title: Re: HYCOM vs ASMR2 Imagery
Post by: Jim Hunt on May 26, 2019, 11:54:07 AM
Bumping this thread to point out that the ACNFS/NOGAPS section of the US Navy's web site seems to have disappeared. However ACNFS/NAVGEM can still be found at:

http://www7320.nrlssc.navy.mil/hycomARC/arctic.html

GOFS 3.0 is at: https://www7320.nrlssc.navy.mil/GLBhycom1-12/POLAR.html

and the current GOFS 3.1 is at: http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/POLAR.html

The GOFS 3.1 reanalysis goes back to 2014.

Comparing MODIS, AMSR2 and GOFS 3.1 for yesterday reveals:

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2591.0;attach=121120;image)


Title: Re: HYCOM vs ASMR2 Imagery
Post by: jdallen on May 26, 2019, 09:48:08 PM
Bumping this thread to point out that the ACNFS/NOGAPS section of the US Navy's web site seems to have disappeared. However ACNFS/NAVGEM can still be found at:

http://www7320.nrlssc.navy.mil/hycomARC/arctic.html

GOFS 3.0 is at: https://www7320.nrlssc.navy.mil/GLBhycom1-12/POLAR.html

and the current GOFS 3.1 is at: http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/POLAR.html

The GOFS 3.1 reanalysis goes back to 2014.

Comparing MODIS, AMSR2 and GOFS 3.1 for yesterday reveals:

(https://forum.arctic-sea-ice.net/index.php?action=dlattach;topic=2591.0;attach=121120;image)
Thank you, Jim.  I haven't been spending much time in the navy models, recently, but may start again. GOFS seems a significant improvement over the older.  I'm updating my links.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 25, 2020, 09:41:41 PM
Just a comparison for this time of year.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 25, 2020, 09:44:02 PM
and the rest. It should be noted that 2014 image was later in the year than the rest.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 25, 2020, 10:09:32 PM
and January 2019 to June 2020
Title: Re: HYCOM vs ASMR2 Imagery
Post by: OffTheGrid on June 25, 2020, 11:53:50 PM
 :o
Mind reader! Lols
Would you believe I just downloaded those seven years for 25 June and was about to post them? At least one of us must be psychic!
Perhaps certain people repeatedly claiming that this year is not in the running for any records got to you too. ;)
This month animation of Beaufort ice compressive strength is interesting. Seems to be getting very mushy.
Might as well post the latest month animation too, out to July 2.
As might be expected with a week of hot offshore winds, the ocean side of the CAA looks like Its detaching like it did last year.

The most simular year to this one at this point seems like 2017. Not sure if the velocity of export to the Beaufort and Fram were as high as this year has produced. Particularly how the thickest ice has been pouring out of the inner basin down the outer CAA, and keeping the Beaufort and Chukchi full, as fast as they try to melt it.

Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 26, 2020, 12:54:55 AM
I think the hycom model is much better than any of the others yet I don't see it on the forum very often. I am not sure why.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: OffTheGrid on June 26, 2020, 01:24:47 AM
Maybe because Its got "experimental" stated in big friendly letters? Perhaps people think that piomass and the various extent and area metrics are actually  measured, when all of them are just as much "experimental" models, if not more so?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: oren on June 26, 2020, 08:49:01 AM
I don't tend to rely much on Hycom, I doubt its veracity, but that's just my intuition as I've never done a rigorous verification.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: blumenkraft on June 26, 2020, 08:52:43 AM
Here is my problem with HYCOM. One day you have 4m thick ice. Then the ice cracks and HYCOM drops the thickness to 2m immediately. No, it didn't lose half of its thickness in a day.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 26, 2020, 09:42:01 PM
I like the feedback on the hycom model especially from experienced persons. I don't have much experience because until now I couldn't get consistant acess. When I compare daily pictures I don't notice any jumps in thickness from day to day. Especially not from 4 meters to 2 meters. Maybe the 3.1 model fixed that? Right now there is so little above 3 meters it would be hard to spot. I guess what I am asking is if you have based that on the newest model or on an older one? I do like the higher resolution but if the model is junk that is not as important.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: blumenkraft on June 26, 2020, 09:54:49 PM
Especially not from 4 meters to 2 meters.

Well, i exaggerated there a little but that's the gist.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 26, 2020, 09:57:31 PM
Especially not from 4 meters to 2 meters.

Well, i exaggerated there a little but that's the gist.
Who hasn't but the last time you looked was it the older model?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: oren on June 26, 2020, 10:46:25 PM
Wht not compare Hycom to the Cryosat +SMOS thickness map from April 15th? That map should be quite reliable. This way you can see if Hycom is in the right ballpark, at least for that date before melting begins.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: johnm33 on June 27, 2020, 12:43:28 AM
Hycom. Mostly the older model was preferred, when they ran side by side, myself i preferred the current one. Bear in mind that there's some very expensive kit under the ice and whilst whole areas may be designated a particular depth for safety reasons it may be that there's an anticipated max for keels thats indicated rather than actual thickness, thus wave action passing through may cause much of the thicker ridged ice to simply keel over into created 'voids' changing the safety code. Lets say perhaps 15% of 4m ice floes will have a 12m keel depth and as waves [swells] pass the thinnest ice clumps together in the troughs freeing space for the keels to flip, so no real change in volume but huge change in geometry.
Title: Re: HYCOM vs ASMR2 Imagery
Post by: interstitial on June 27, 2020, 02:13:26 AM
Wht not compare Hycom to the Cryosat +SMOS thickness map from April 15th? That map should be quite reliable. This way you can see if Hycom is in the right ballpark, at least for that date before melting begins.
I looked. While their were some differences they looked about the same to me. The piomass with its lower resolutions blurs some features  also the major color changes happen at different thresholds. Those color thresholds made one model look like it was diverging from the other but looking at it I can see that would occur with the same volume estimates. Did you see something different? Did you expect me to see something different?
Title: Re: HYCOM vs ASMR2 Imagery
Post by: oren on June 27, 2020, 08:16:53 AM
I have not looked. I would appreciate a posting of Hycom Apr 15th and Cryosat Apr 15th side by side somewhere, maybe in the new Hycom thread. I would look for differences where the anomalies were supposed to be - near Svalbard, in the Beaufort, and in the ESS.