tag:blogger.com,1999:blog-5235419263414453422.post3021929673095599477..comments2024-02-23T01:30:06.101-08:00Comments on Early Warning: Extracting Signal From Drought NoiseStuart Stanifordhttp://www.blogger.com/profile/07182839827506265860noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-5235419263414453422.post-80376885064712447162010-11-02T06:20:10.786-07:002010-11-02T06:20:10.786-07:00Gary:
Just to be clear, the PDSI principal compon...Gary:<br /><br />Just to be clear, the PDSI principal component analysis is from the Dai review - I didn't reproduce it myself.Stuart Stanifordhttps://www.blogger.com/profile/07182839827506265860noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-66286342725978765572010-10-30T01:01:54.970-07:002010-10-30T01:01:54.970-07:00Stuart, are you reading Judith Curry's stuff (...Stuart, are you reading Judith Curry's stuff (eg: http://judithcurry.com/2010/10/24/overconfidence-in-ipccs-detection-and-attribution-part-iii/ ) There's some overlap with what you like to explore, and I find her a very lucid and honest thinker - so I think you'd enjoy engaging with her ;)Sam Charles Nortonhttps://www.blogger.com/profile/04088870675715850624noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-17254000616246858602010-10-29T20:13:55.449-07:002010-10-29T20:13:55.449-07:00Stuart,
I've been thinking a bit more about y...Stuart,<br /><br />I've been thinking a bit more about your results. I'm wondering if your methodology allows your to "calibrate" the strength of the principle components against one another. In this case, the warming-drying trend compared to ENSO effects. Qualitatively, many people can relate to the odd weather during El Nino years. Yet here is something that is more significant in terms of the strength of the principle component.<br /> Looking at the first principle component, you see some noisy oscillations until 1960 or so. What happens if you only look at data before that time? Which component is most important on the truncated data set? How about just in data since that time? I guess what I'm asking is how does the magnitude of the principle component change for various long term averages? Clearly, if the trends are largely oscillatory changes like ENSO, the magnitude of the principle component representing that behavior should be roughly the same magnitude as long as you average over several periods. However, with the onset of a unidirectional trend you might expect to see the principle component representing this slowly rise out of the mud. Rather than being just 7% of the signal since 1900, it might represent 20% of the variations today.Garyhttps://www.blogger.com/profile/08580497879135994296noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-54555949482585649522010-10-28T05:52:39.778-07:002010-10-28T05:52:39.778-07:00Ah - looks like that detailed examination of PDSI ...Ah - looks like that detailed examination of PDSI is going to have to wait another day. The algorithm is really surprisingly arcane.Stuart Stanifordhttps://www.blogger.com/profile/07182839827506265860noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-91365808668511157402010-10-27T19:39:44.322-07:002010-10-27T19:39:44.322-07:00Gary:
One could subtract it out (technically proj...Gary:<br /><br />One could subtract it out (technically project it out), but not so easy to do by cut and paste from the existing figures in the paper!<br /><br />Also - I think ENSO simulation is still a very active area of research in climate models and they don't have it down. Eg, <a href="http://wcrp.ipsl.jussieu.fr/Workshops/CLIVAR/index.html" rel="nofollow">here's</a> an upcoming workshop on the subject:<br /><br /><i>El Niño - Southern Oscillation (ENSO) is the dominant mode of interannual climate variability with worldwide weather and societal impacts. Because ENSO involves a complex interplay of numerous ocean and atmospheric processes, accurately modelling this climate phenomenon with coupled General Circulation Models (GCMs) and understanding and anticipating its behaviour on seasonal to decadal and longer time scales still poses a formidable challenge. Over the past few years, new promising methods have emerged which can improve ENSO simulation, for example by combining ENSO theoretical frameworks and GCM modelling or by using initialised hindcasts and by utilising the recent wealth of high-quality observations to understand errors and their growth in forecast systems. By focusing on the very key processes affecting ENSO dynamics, these new approaches have a strong potential to accelerate progress and improve representation of ENSO in complex climate models. Not only can these new methods help address the question of whether ENSO is changing in a changing climate, but potentially they can also improve reliability of centennial-scale climate projections.<br />The World Climate Research Program (WCRP) has long recognised the central importance of an improved understanding and predictability of ENSO by encouraging coordinated research in tropical climate variability via its different expert Panels (Pacific, Indian, Seasonal to Interannual Prediction,...) The next Coordinated Model Intercomparison Project (CMIP5), which will feed into the IPCC 5th Assessment, provides a new opportunity to evaluate current research in the process-based evaluation of ENSO in GCMs.<br />Main goal<br />The workshop aims to present and discuss emerging new methods for the process-based evaluation of ENSO in GCMs, their use in multi-model assessments and identify future directions and associated challenges.<br />Specific goals<br />a) To make an inventory of the existing approaches to evaluate ENSO processes in GCMs; compare, contrast and discuss the relative merits of these approaches as for example applied to CMIP3;<br />b) To review the potential of methods bridging ENSO theoretical frameworks and GCM modelling; and,<br />c) To review the observing system and available data for the evaluation of ENSO in GCMs.</i>Stuart Stanifordhttps://www.blogger.com/profile/07182839827506265860noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-72173881582663937512010-10-27T19:36:57.438-07:002010-10-27T19:36:57.438-07:00Porsena:
I think the implication is that at this ...Porsena:<br /><br />I think the implication is that at this stage, there's still a lot of just random noise (aka weather) going on as well. Presumably, over time, the global warming signal will get stronger and stronger (not that it will be stronger every single year, but over the decades).Stuart Stanifordhttps://www.blogger.com/profile/07182839827506265860noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-84476266123598641822010-10-27T17:14:01.513-07:002010-10-27T17:14:01.513-07:00Beautiful!
Just out of curiosity, can you "...Beautiful! <br /><br />Just out of curiosity, can you "subtract out" the second principal component and plot what is left? I'm wondering if the US starts looking more like the models.<br /><br />Second question - do you know if typical climate models include ENSO effects - and if so how would they get the phasing correct? Is it weather or is it climate!Garyhttps://www.blogger.com/profile/08580497879135994296noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-865018390918987012010-10-27T15:58:55.530-07:002010-10-27T15:58:55.530-07:00Should we attach much importance to the finding th...Should we attach much importance to the finding that the first and second principal components account for only 12% of the variance between them?porsenahttps://www.blogger.com/profile/04362269873149438270noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-48734119270960992302010-10-27T15:13:14.392-07:002010-10-27T15:13:14.392-07:00Greg:
Why thank you! I was trying...
Amusingly,...Greg:<br /><br />Why thank you! I was trying...<br /><br />Amusingly, I have always pretty much not liked to teach, taught only one class in my time at the university, and that was a major factor in my electing to pursue industrial research of various flavors, rather than stay in the university system. The issue being that I get bored very quickly once I understand something, and can't stand regurgitating it again. Blogging is ok, because I can write it up almost as soon as I've figured something out.Stuart Stanifordhttps://www.blogger.com/profile/07182839827506265860noreply@blogger.comtag:blogger.com,1999:blog-5235419263414453422.post-6973257732226184282010-10-27T14:49:35.622-07:002010-10-27T14:49:35.622-07:00Excellent exposition, Stuart. You have talent as a...Excellent exposition, Stuart. You have talent as a teacher!<br /><br />I look forward to tomorrow's tutorial.Greghttps://www.blogger.com/profile/11939046017258198038noreply@blogger.com