This is Pjie2's Typepad Profile.
Join Typepad and start following Pjie2's activity
Join Now!
Already a member? Sign In
Recent Activity
Is it possible to convey both by using hue for the proportion and intensity for the population? So you end up with an intense yellow dot for London, a pale blue for most of rural England and Wales, and s very pale yellow for Scotland with more intense cities?
Actually, I was wrong, the final/locked version of the graph appears to be mislabelled. Specifically, on the latest version, there is no dark green line for 2014. Instead the pale purple line (labelled 2015 in the key) follows the trace that was labelled as 2014 in the bugged version.
Toggle Commented Feb 24, 2016 on Grasping at uncorrected straws at Arctic Sea Ice
They didn't just remove the 30% graph, they corrected it. Look here: The latest line (pale purple) goes all the way to the end of 2015. If you compare it to the previous version on the broken graph (black line), you can see they start to diverge around the 1st of November. Looks like they've sorted out the bug, corrected the data up to the end of 2015, and then officially retired the graph. Anyone wanting to witter on about 30% versus 15% or any other such horseshit needs to account for why the final validated version of the 30% graph now shows 2015 as being no different from the rest of the pack right up until the end of December.
Toggle Commented Feb 23, 2016 on Grasping at uncorrected straws at Arctic Sea Ice
Also - what would the assassins hope to achieve? If Wadhams is correct, then at the very most killing people off would delay discovery of the putative Arctic collapse by... a year or so? Did any of the three people look likely to convince the world of an imminent Arctic catastrophe in the next few months?
The physical meaning is that it lets you ask the question "Do all years obey the same rules governing melt?" As I understand it, the plan is to run the "tweaking the variables" process multiple times, each time leaving out a single year from the training set, and then seeing how well the excluded year is forecast by the (tweaked) variables. That gives you two bits of information. 1) Are all years forecast equally well, or are there individual 'outlier' years that are poorly forecast? A reason for this could be (e.g.) an unusual wind setup that only brought winds into the Arctic through the Bering Strait, over sea rather than over land. This would mean that for that specific year, land snow cover would have less effect than in other years. 2) When you compare the different runs, so you always end up with the same parameters, or is it wildly variable between runs? If you get a different set of parameters for each different training set, it becomes much harder to believe that the overall process is reliable.
I know that ice is thicker in the central Arctic, I'm not an idiot. Can you point to _ANY_ feature that might affect ice melt or ocean salinity (e.g. wind patterns, ocean depth, ocean currents, insolation, snow depth...) that aligns neatly and precisely with the 80 degree parallel, producing a sharp discontinuity? The Navy models are currently producing profoundly unphysical results.
Toggle Commented Jul 15, 2015 on PIOMAS July 2015 at Arctic Sea Ice
"The Navy sea ice model shows that there is a large area of close to zero model thickness that's going to melt out by the end of the month. " Both versions of the Navy model show an abrupt change in sea surface salinity, that is almost perfectly circular, and precisely aligned with the 80 degree North line of latitude. I can think of no conceivable physical process which could generate this. In the absence of this, I think we have to treat both Navy models with extreme cautions, as there is likely some kind of bug in the code as it stands.
Toggle Commented Jul 15, 2015 on PIOMAS July 2015 at Arctic Sea Ice
Heya - is that your own graph for 2014F? The one on the web has no bottom pinger, and moreover the record stops in mid March.
Toggle Commented Jul 8, 2015 on ASI 2015 update 4: massive heat at Arctic Sea Ice
Without seeing more traces from between 24th/30th I don't think we can say. All we know is that currently there appears to be a lens of fresh (or very nearly fresh) water under 2014A. We don't know where it came from or how deep it goes. It could be localised melt pond drainage - probably not directly down the thermistor string though as otherwise you'd see the temperature rise all the way along the string. Could also be river outflow pooling under the ice. If the thermistor string was long enough we could distinguish the two, since I imagine localised drainage would form a pool a few tens of cm deep at most, whereas river outflow might form a thicker layer.
Uh, are you missing the trace from 30th May that shows the water under the ice as hovering about -0.2 degrees?
I think "pulverised" is too strong a word. Remember the resolution of the techniques you're using. Even a single pixel on (say) MODIS/TERRA imaging from Worldview is 250m across - which means that the floes you're looking at are generally a minimum of 1km across, which classes as big or vast floes. The off-shore breakup in the Beaufort is possibly a bit ahead of schedule, but that's all we can reasonably say fo far this year.
Toggle Commented Apr 24, 2015 on CryoSat-2 sea ice thickness maps at Arctic Sea Ice
Re: "thinner ice allows better precision of measurement" I took this as being awkward shorthand for one or other of the following: (a) Thicker ice has characteristics (more rugged surface) that make it harder to measure, or even define "thickness, so it is easier to get good measurements from thin ice. (b) Many measuring implements have percentage errors rather than absolute errors. If your measurement has error bars of +/- 5%, then your measurement of 1m ice is correct to within 5cm, while your measurement of 10m ice is only correct to the nearest 50cm. Both of these are fairly obviously true, and both are in my view encompassed by saying "thinner ice allows more precise measurement", allowing for everyday use of vocabulary. "Precision" isn't a precise term, and in the absence of obvious trolling intent we should construe all posts as generously as possible.
Toggle Commented Apr 13, 2015 on PIOMAS April 2015 at Arctic Sea Ice
I like this buoy as an example of the sort of useful measurements you do get: First, it's not moved much, so you can rule out gross changes in latitude/insolation as a reason for differences between 2013/14 and 2014/15. Next, there's temperature data - looks to me as though this winter was slightly milder than the previous one in terms of total freezing degree days, but I'd have to download the file to be sure. Finally, you can see it's thickened substantially more this year. This is almost certainly due to the insulating effects of snow last year meaning that the ice thickening was restricted. Later on this year, we will get to see the impact of the reduced snow cover on the onset of melt. Last year's melt didn't get going until mid June, possibly because of the high albedo of snow. We'll see if it starts earlier this year (and how that relates to air temperatures). Other things you can point out are the fact that there was a very warm episode in mid Feb of 2014, but this had very little effect on the rate of re-freeze - again possibly due to the snow insulating the ice from transient effects of air temperature.
Toggle Commented Apr 11, 2015 on PIOMAS April 2015 at Arctic Sea Ice
Neven: We've been over this discussion about buoys before. No, they don't give a good measure of the average thickness - because they can only be placed in flat ice. If you look back through the record, they've been placed sometimes in 1st year ice and sometimes in multi-year ice. Many of the ones that were initially in 1st year ice have graduated to multi-year ice by surviving more than one season. Others were placed in 1st year ice near the end of summer, which technically immediately became multi-year ice a couple of weeks later when the re-freeze started. However, the specifics of age are irrelevant given the context: that the buoys have to be placed in flat ice that is thin enough to drill through in order to place the buoy in the first place! The distribution of Arctic ice thicknesses is highly non-uniform - you have sheets of comparatively thin flat ice (of whatever age), and thick pressure ridges at the boundaries between floes. The ridges contain something like half the total ice volume, and so measuring the flat/unridged ice gives a poor indication of average ice thickness. The point of the buoys is not to tell us average thickness, but to inform us about the processes of thickening and melting. How quickly does ice thicken under given conditions of temperature / insolation / humidity? How much melting is driven by insolation, and how much by warm water from underneath? How does snowfall at various points in the season affect these factors? How accurate are our models of Arctic surface air temperatures relative to actual on-the-ground measurements? So yes, they buoys are "useless" at measuring average sea thickness across a wide area. They are also useless at making espresso, or appreciating a Mahler symphony. Don't expect instruments to do something they were never designed to do! Think of the Arctic ice like a patchwork of fields in the countryside. There are flat grassy areas (undeformed ice), hedges (pressure ridges), shrubby patches (heavily ridged ice fields) and trees (icebergs). The buoys are designed to measure how fast the grass grows, and can only (in this analogy) measure up to the length of a blade of grass. You can't use them to tell you anything about the hedges or the trees, and consequently you can't say "what is the average height of the vegetation" (average thickness), or "what is the total biomass" (volume). Accept them for what they are, and move on. Re: the DMI model. I don't know why we are bothering to discuss a model which is almost certainly badly wrong, since it disagrees with all the other models and with the Cryosat measurements (which unlike the buoys is actually designed to measure aggregate thickness across an area). Re: precision - this is a very tedious semantic argument. Cincinnatus is absolutely right in saying that buoys are only installed in thinner, flatter patches of ice (even the one in the 3m floe is way thinner than a pressure ridge). He is also right in saying that the reason for this is that the buoys cannot accurately measure ridged ice. Whether you call that "precision" is up for grabs, since precision is an imprecise term - but it communicates the problem well enough. In fact, it is IMPOSSIBLE to measure the average thickness of a ridged ice field with a point measurement like a buoy.
Toggle Commented Apr 11, 2015 on PIOMAS April 2015 at Arctic Sea Ice
"in fact it may be cooler than the air" Yes, precisely. So why does the second sentence on your website say that ice cooling faster than air "is impossible with a standard physics interpretation"? It's perfectly ordinary physics.
Toggle Commented Apr 29, 2014 on More on melt ponds at Arctic Sea Ice
Hi Wayne. In the second sentence on your site, you say "...sea ice must warm or cool faster than surface air, this is impossible with a standard physics interpretation." This is wrong, it's perfectly possible for a surface to warm or cool faster than the overlying air, as anyone who's ever stood in the sun or found frost on their car windshield in the morning can tell you! In particular, you can get frost forming on nights where the air temperature never goes below freezing. The thermal capacity of the air is low, as is the efficiency of heat transfer between (solid) surface and (gas) air. Thus the heating or cooling of the surface itself is dominated by the radiative flux rather than by conduction. Since the surfaces are radiating straight up to the night sky and the cosmic microwave background (-270 degrees C), this means they can lose heat rapidly and drop well below the ambient air temperature. You end up with a very steep temperature gradient above the surface, with the surface being below freezing, and the air temperature even a few centimetres higher being above freezing.
Toggle Commented Apr 29, 2014 on More on melt ponds at Arctic Sea Ice
For starters, the Arctic in the early Holocene experienced an order of magnitude higher level of solar irradiance than today's climate I do not think "order of magnitude" means what you think it means. To increase solar irradiance by an order of magnitude, you have to travel to Mercury.
(add the 7-2-1 layer to see it best)
Toggle Commented Aug 31, 2013 on Hole at Arctic Sea Ice
That's thin cloud, not re-freeze. It's clearer on Earthview.,-49024,4544,174720&products=baselayers,MODIS_Terra_CorrectedReflectance_Bands721,!MODIS_Aqua_CorrectedReflectance_TrueColor,MODIS_Terra_CorrectedReflectance_TrueColor~overlays,arctic_coastlines_3413&time=2013-08-31&switch=arctic
Toggle Commented Aug 31, 2013 on Hole at Arctic Sea Ice
IJIS values have been more variable since the AMSR satellite failed and they started using Windsat data instead. Although the image they produce is now from AMSR-2, I believe they still use Windsat for the numerical data. I don't think Cryosphere Today or NSIDC show increased variability in the last couple of years, so I doubt it has anything to do with the melt.
"Only" July? July is the hottest month of the year for every one of those locations.
Why do you find that picture so unlikely? At the point when we have a fully seasonal Arctic ice cover, I fully expect the last bits of ice each year to be somewhere around the entrance of the Fram. This is no more than saying that a nearly-empty sink is likely to have water near the plughole.
Toggle Commented Jul 7, 2013 on So, how slow was this start? at Arctic Sea Ice
Don't think it's draining, just that the visibility changes with the angle of the Sun. If you look at the video you'll see it come and go 2-3 times over the last few days, in a strict daily rhythm.
I wondered whether it might be that 2012J is close to an open lead - but I don't think that's the reason. We know 2012H, OBuoy 8 is practically in a lead (just look at the video!) and at a lower latitude, and there's no sign of bottom melt there yet.
I think the PAC is still cold enough to be dropping more snow rather than rain. There's no evidence of rain there at the moment. The droplets on the North Pole webcam are more likely snow or sleet melted by the camera's own heat. You can see from the marker poles (and the colocated buoy data) that there's been no snow melt there in the last few days.