HYCOM vs ASMR2 Imagery

[JimboOmega]

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?

[Neven]

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.

[Michael Hauber]

I say there is no way that the ice concentration is higher in the Beaufort region than in the central Arctic just to the Alaskan side of the NP as Hycom is showing

[JimboOmega]

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? 

[bbr2314]

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.

[Richard Rathbone]

That's not the nowcast, thats a forecast for a week's time.

[Metamemesis]

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.

[seaicesailor]

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

[seaicesailor]

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

[Jim Hunt]

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, have you ever considered eyeballing MODIS? There's a big difference!

[Nick_Naylor]

Here's the actual nowcast. It still has some 'splainin' to do.

[bbr2314]

This looks pretty accurate, IMO.

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

[Richard Rathbone]

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.

[Jim Hunt]

This looks pretty accurate, IMO.

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

[plinius]

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.

[Richard Rathbone]

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%.

[JimboOmega]

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?

[plinius]

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.

[Richard Rathbone]

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.

[Nick_Naylor]

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]

[bbr2314]

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).

[philiponfire]

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.

[Jim Hunt]

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.

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 to suggest that the bright yellow areas on Bremen AMSR2 imagery are anything more significant than melt ponds.

Am I missing something?

[Jim Hunt]

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 that "The ice has clearly broken completely in two now"?

[plinius]

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).

[bbr2314]

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 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...

[Jim Hunt]

The "bulk" is pushed against the CAA/Greenland.

So the "gaping fissures that span from Siberia to Canada" have miraculously vanished?

[bbr2314]

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.

[philiponfire]

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.

[magnamentis]

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 :-)

[Jim Hunt]

You keep ignoring me.

Oh no I don't!

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?

[bbr2314]

You keep ignoring me.

Oh no I don't!

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')

[Darvince]

Could you maybe chill?

[bbr2314]

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?

[Tigertown]

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.

[Tigertown]

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

[Lawrence Martin]

@bbr2314   @Tigertown

Could you please tone down the trolling a bit?

[JimboOmega]

You keep ignoring me.

Oh no I don't!

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.

[Tigertown]

@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.

[Jim Hunt]

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?

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 of the area:



and here's the NSIDC's view of those "gaping fissures" of yours:

[Neven]

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. 

[Jim Hunt]

Guys, why don't you make notes of what the other is saying

I've already done that Neven.

Do you recall Snow White's "little black book"?

[Jim Hunt]

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"

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 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

Here's another relevant paper in the current context:

"Influence of melt ponds on microwave sensors' sea ice concentration retrieval algorithms"

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%.

[bbr2314]

<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.>

[Jim Hunt]

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.

[Jim Hunt]

ktonine enquires elsewhere re ACNFS:

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:

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.

[Jim Hunt]

Here is the ACNFS 1 day concentration forecast for yesterday:



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

[FishOutofWater]

HYCOM is good for entertainment but the nowcast and forecast parts are alternate realities. Folks shouldn't take this stuff seeriously.

[Jim Hunt]

HYCOM is good for entertainment but the nowcast and forecast parts are alternate realities.

I enquired about the issue on the Hycom forum, and according to Alan Wallcraft:

We now use the National Ice Center's IMS sea ice extent product in our assimiltion, see 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.

[Neven]

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.