Meta tags:
description=Formerly the most awesome blog on wordpress!;

Headings (most frequently used words):

station, data, methods, the, part, method, forest, and, to, combine, combining, inhomogeneous, of, trees, for, has, burned, down, almost, back, not, blogging, lately, better, late, than, never, theme, change, other, things, second, thoughts, on, north, american, snow, cover, ii, an, overview, evaluation, with, perfect, results, first, difference, fdm, climate, anomaly, cam, bias, reference, rsm, references, blogroll, archives,

Text of the page (most frequently used words):
the (621), and (154), data (114), that (89), for (88), this (67), #station (64), with (55), are (55), figure (54), series (48), rsm (42), temperature (38), from (38), methods (38), all (37), results (35), fdm (34), stations (33), year (32), model (31), a1b (31), 20c3m (31), method (30), average (30), area (30), one (30), period (28), over (28), same (27), more (27), grid (27), have (25), first (25), was (25), when (25), runs (25), trends (24), there (24), mean (24), cam (24), step (23), time (23), sam (23), 2010 (22), error (22), shows (22), but (22), trend (22), land (22), posted (21), not (21), see (21), each (21), four (21), some (21), true (20), using (19), because (19), about (19), than (19), comparison (19), space (18), may (17), were (17), used (17), table (17), will (17), warming (17), snow (17), surface (16), giss (16), how (16), simple (16), anomalies (16), missing (16), show (16), other (15), change (15), anomaly (15), bias (15), periods (15), into (15), now (14), difference (14), which (14), averaging (14), much (14), then (14), can (14), averages (14), extent (14), climate (13), very (13), their (13), post (13), values (13), has (13), you (13), spatial (13), comments (12), found (12), different (12), last (12), out (12), been (12), january (11), global (11), blank (11), they (11), calculate (11), standard (11), box (11), spurious (11), errors (11), combine (11), between (11), calculated (11), urban (11), after (11), century (11), posts (10), multiple (10), what (10), combined (10), changes (10), since (10), figures (10), treesfortheforestblog (10), regression (10), north (10), ensemble (10), forest (9), 2009 (9), only (9), given (9), annual (9), similar (9), here (9), should (9), reference (9), non (9), done (9), mask (9), running (9), most (9), models (9), too (9), gridded (9), get (8), record (8), jones (8), 1999 (8), weighting (8), combining (8), correct (8), next (8), generated (8), well (8), zero (8), significant (8), three (8), think (8), applied (8), below (8), large (8), two (8), combination (8), years (8), base (8), coverage (8), make (8), 011 (8), 1967 (8), fraction (8), february (7), would (7), began (7), inhomogeneities (7), these (7), its (7), present (7), variability (7), look (7), point (7), also (7), new (7), within (7), least (7), down (7), created (7), issue (7), 000 (7), need (7), miroc (7), less (7), five (7), half (7), compared (7), way (7), frei (7), lot (7), sce (7), agreement (7), wordpress (6), trees (6), blog (6), free (6), air (6), differences (6), didn (6), distance (6), records (6), order (6), issues (6), relative (6), climatology (6), deviations (6), while (6), resulting (6), weights (6), such (6), larger (6), use (6), many (6), another (6), value (6), original (6), differenced (6), 125 (6), correlation (6), hires (6), scale (6), spread (6), still (6), whose (6), before (6), ocean (6), cover (6), program (6), total (6), latitude (6), ncar (6), take (6), like (5), things (5), run (5), comparisons (5), variations (5), temperatures (5), hansen (5), analysis (5), 1987 (5), numbers (5), above (5), etc (5), produce (5), know (5), previous (5), better (5), produces (5), normalized (5), others (5), second (5), offset (5), weighted (5), process (5), enough (5), introduced (5), month (5), number (5), statistically (5), good (5), 004 (5), decade (5), contains (5), shown (5), let (5), had (5), gong (5), american (5), something (5), means (5), greenland (5), fortran (5), sum (5), uncategorized (5), tropics (5), writing (5), com (4), sign (4), create (4), march (4), peterson (4), geophys (4), res (4), wigley (4), 1982 (4), part (4), any (4), corresponding (4), appears (4), expected (4), don (4), weight (4), compare (4), shouldn (4), gets (4), overall (4), deviation (4), perfect (4), 200 (4), could (4), monthly (4), example (4), correlations (4), corrected (4), 956 (4), 932 (4), 249 (4), plotted (4), resolution (4), recent (4), work (4), old (4), got (4), affects (4), together (4), negative (4), showing (4), small (4), however (4), times (4), 032 (4), ar1 (4), 001 (4), related (4), does (4), lag (4), 015 (4), linear (4), realistic (4), terms (4), certainly (4), santer (4), concern (4), covered (4), wrong (4), fact (4), significance (4), america (4), longitude (4), represent (4), udunits (4), why (4), code (4), finer (4), working (4), site (3), required (3), september (3), roman (3), hemisphere (3), 1986a (3), doi (3), made (3), location (3), adding (3), synthetic (3), implemented (3), completely (3), hopefully (3), update (3), cycle (3), 20th (3), gaps (3), available (3), incorporated (3), 007557642 (3), further (3), both (3), procedure (3), result (3), included (3), later (3), brought (3), beginning (3), evaluate (3), variable (3), pre (3), industrial (3), control (3), generate (3), tamino (3), yet (3), never (3), ways (3), them (3), 545 (3), did (3), segment (3), ran (3), calculations (3), 500 (3), although (3), insignificant (3), seriously (3), 055 (3), 246 (3), 022 (3), 025 (3), covering (3), respectively (3), added (3), entire (3), doesn (3), variance (3), smoothed (3), 2005 (3), thanks (3), declining (3), few (3), rutgers (3), checked (3), netcdf (3), sure (3), haven (3), someone (3), products (3), begins (3), programs (3), off (3), lagged (3), divergence (3), getting (3), file (3), looking (3), cmip3 (3), took (3), unfortunately (3), defined (3), fractional (3), reading (3), thought (3), topic (3), theme (3), blogging (3), busy (3), properly (3), load (3), soon (3), ubuntu (3), website (2), write (2), comment (2), content (2), log (2), subscribed (2), subscribe (2), already (2), july (2), 2011 (2), science (2), lucia (2), jeff (2), older (2), karl (2), 1998 (2), long (2), term (2), raper (2), 1986b (2), 1851 (2), 1984 (2), appl (2), meteor (2), northern (2), 1881 (2), 1029 (2), lanzante (2), inhomogeneity (2), references (2), uses (2), factor (2), fine (2), correctly (2), thus (2), far (2), despite (2), follow (2), altitude (2), largest (2), early (2), near (2), increase (2), among (2), considering (2), skikda (2), aren (2), determining (2), additional (2), surprising (2), answer (2), problems (2), poorest (2), performing (2), incurred (2), mentioned (2), gridbox (2), graph (2), described (2), length (2), adjust (2), until (2), downside (2), exist (2), during (2), accurately (2), must (2), biased (2), possible (2), instead (2), except (2), initial (2), regional (2), containing (2), give (2), calendar (2), coincide (2), shape (2), form (2), nearby (2), 997 (2), 374 (2), 995 (2), against (2), able (2), deal (2), bound (2), his (2), points (2), quite (2), discuss (2), interesting (2), lost (2), concerned (2), find (2), produced (2), magnitude (2), strong (2), artificial (2), occurs (2), distribution (2), noticed (2), higher (2), turned (2), affected (2), somewhat (2), bounds (2), eye (2), chose (2), uncertainty (2), estimates (2), positive (2), succumbed (2), squares (2), line (2), closely (2), lower (2), based (2), uncorrupted (2), plus (2), selected (2), goes (2), atmospheric (2), level (2), closest (2), types (2), respect (2), taken (2), inhomogeneous (2), begin (2), dominate (2), explanation (2), future (2), separate (2), common (2), adjusted (2), steps (2), 347 (2), through (2), close (2), 192 (2), 006 (2), itself (2), 012 (2), note (2), saw (2), performed (2), mears (2), 2008 (2), consistency (2), observed (2), tests (2), observations (2), observation (2), simulations (2), almost (2), whole (2), either (2), indicates (2), test (2), drop (2), end (2), cgcm (2), unrealistic (2), improperly (2), looks (2), problem (2), back (2), comparable (2), remote (2), sensing (2), systems (2), turns (2), told (2), improves (2), lagging (2), convert (2), wrote (2), tells (2), immediately (2), software (2), big (2), going (2), package (2), ccsm (2), trained (2), unit (2), medres (2), low (2), inm (2), iap (2), fgoals (2), makes (2), check (2), csv (2), 1880 (2), discussed (2), bit (2), noise (2), divergance (2), obvious (2), faster (2), isn (2), aom (2), multiplied (2), mri (2), earth (2), zeke (2), pretty (2), break (2), goddard (2), paper (2), published (2), came (2), gotten (2), thinking (2), lately (2), doing (2), serious (2), inspiration (2), plots (2), 1701 (2), regions (2), biases (2), practical (2), practically (2), reduced (2), allow (2), everyone (2), who (2), product (2), ghcn (2), represented (2), valid (2), determine (2), minimum (2), consolidate (2), computing (2), memory (2), projects (2), late (2), read (2), hearted (2), linux (2), say (2), card (2), focus (2), computer (2), left (2), fast (2), forced (2), currently (2), interface (2), downloading (2), fresh (2), msu (2), day (2), start (2), burned (2), else (2), maybe (2), formerly (2), awesome (2), started, design, name, email, loading, collapse, bar, manage, subscriptions, view, reader, report, privacy, account, august, october, november, december, archives, search, doom, international, journal, inactivism, blackboard, vent, statistics, skeptical, real, rabett, open, mind, gold, greenfyre, climatewtf, feedback, audit, chris, colose, blogroll, precision, jamason, knight, easterling, maximizing, density, calculation, 103, d20, 967, 974, southern, 1213, 1230, bradley, diaz, kellyo, 161, 179, kelly, 1980, 110, mon, wea, rev, ruedy, glascoe, mki, sato, 30997, 31022, 1999jd900835, 104, lebedeff, measured, 13345, 13372, angell, durre, seidel, 2004, reduce, radiosonde, datasets, 4171, 4179, mistake, implementing, experimenting, reason, believe, qualitatively, sensitive, tomorrow, corrupt, simulate, micro, deals, agree, gradually, declines, mid, 1990s, spike, afterwards, disagreement, 611289, 023912322, 607422, 359519, 085986, 371832, terribly, performs, couldn, insufficient, duplicates, loss, algeria, minute, unique, 05148679, 0507627, 05001916, 04925646, 04847489, accounts, homogeneous, discontinuities, equivalent, quote, stated, encounters, jumps, 41x, incorporating, information, shot, excluding, twice, outlined, expressed, 3126117, located, evaluation, elaborated, overlapping, twenty, continues, merge, requires, estimate, incomplete, conceivable, leave, investigation, differing, altitudes, aspects, interpolate, raw, necessary, popularized, motivation, phil, put, encounter, conventional, shifted, alternatively, set, equal, final, cannot, reconstructed, unless, first, cluster, discussion, dealing, involves, subtracting, subtract, 1986, months, undo, differencing, cumulative, sums, climatologically, meaningless, renormalized, appropriate, our, overview, layman, lurker, unsurprisingly, strongly, correlated, quantified, pearson, coefficient, inside, parenthesis, kilometers, pairs, approximate, reality, homogeneity, decided, apply, approximately, extracted, match, choice, giving, random, uniquely, exciting, motivated, revive, project, portions, become, probably, fail, unphysical, causes, even, skew, stay, tuned, resisting, ten, counterparts, signs, stress, worry, modify, robust, 355, 226, 041, resisted, throughout, resist, altering, third, artificially, warmed, dominates, terminated, faired, won, bother, rms, experiment, matter, showed, programming, bug, wondering, assimilation, randomly, shuffling, unsettling, considerable, mention, smoothing, exaggerate, easily, distinguishable, disturbing, range, coefficients, across, resilient, 024, 244, grey, marks, coincides, stands, serial, graphically, ability, directly, portion, remaining, contribution, concatenating, pressure, 1000, hpa, corresponds, 300, respective, corrupted, inhomogeneitites, equivalence, add, recap, simulated, centered, gone, satellite, where, became, word, try, competing, effects, systematic, feature, succumb, exhibits, previously, moving, dividing, 800, 748, 456, 146, 524, 447, 551, 323, 449, 722, 388, switch, quantifies, best, perform, strangely, evolution, behavior, underlying, signal, noisy, 503, 084, 270, 528, 314, 749, 818, 002, 013, flips, help, visual, refers, residuals, 925, 030, 903, 940, 898, 606, 483, 367, 082, 242, 386, 231, 268, 236, 010, 021, estimated, detail, reporting, visualize, count, dealt, evaluating, similarly, short, comings, revealed, evaluated, thorne, haimberger, taylor, solomon, gleckler, klein, nychka, schmidt, sherwood, wentz, modelled, tropical, troposphere, intl, climatol, 1703, 1722, 1002, joc, 1756, decadal, coupled, atmosphere, general, circulation, lett, l18502, 2005gl023394, hypothesis, familiar, involve, reasonable, having, host, physical, processes, little, albedo, paragraph, bothered, pasting, draft, carrot, eater, decline, applying, statistical, proportion, rejecting, multi, rejected, 014, failed, reject, 889, inter, towards, zeros, adds, plausibility, cccma, t63, csiro, fare, eliminate, ipsl, normalize, double, copied, scaled, deficient, safer, just, exclude, emailed, inquiry, modelling, group, heard, chosen, extents, 196, contacted, lab, weekend, jumped, gun, processed, roughly, degees, recalculated, differed, significantly, starting, explains, days, 0000, analysing, cilmate, conversion, ported, answers, 1871, newer, version, 1870, arises, assumes, follows, words, interpreted, whoever, weary, mindful, explain, due, six, seven, eyeball, impressive, median, apparent, cm3, superb, scenario, greatly, improved, actually, starts, aside, scenarios, problematic, 2000, 2099, expect, creating, dissimilar, appeared, behind, comfort, folder, marked, run4, empty, page, indication, withdrew, improve, concatenated, errata, underestimate, shortly, flucuations, reasons, differ, calcluate, interpolating, subset, masked, represents, including, loaded, zeroed, upon, processing, divided, units, emulated, consulted, hausfather, obtained, nine, continental, mass, legend, gridcell, carl, rss, current, research, hereafter, ar4, simulation, authors, bounded, 190, 340, definition, exact, steve, snowjob, several, conclusions, founded, inadvertently, essentially, locations, might, interpolated, single, suspect, wouldn, come, bad, interpolation, straight, forward, unbiased, pros, cons, ideas, welcome, thoughts, changed, boring, resize, images, crunching, radiosondes, sound, uploaded, per, carrick, request, cells, 1850, 1950, http, treesfortheforest, anyone, griding, intended, extreme, occurring, happens, course, negligible, fairly, incur, physically, bloggers, combing, fractions, haphazard, strongest, 150, rest, likely, sampling, accounted, boxes, amount, greater, occupied, according, reconstruction, consistent, gives, confidence, botch, normally, impose, constraint, needs, worried, neglected, include, hold, summed, varies, compares, nick, stokes, residual, remove, 1961, 1990, require, climatological, methodology, initially, duplicate, entries, applicable, squared, offsets, align, averaged, inventory, inv, notice, absence, sometime, week, though, anyhow, briefly, gridding, analyzing, quiet, lack, interest, topics, homogenization, past, weeks, migration, machine, easier, winxp, mingw, specifically, likes, crash, video, apparently, supported, crashes, learned, screen, suddenly, black, speaking, hit, publish, cra, download, system, amd, athlon, 635, processor, graphics, lucid, lynx, major, slug, paced, piece, garbage, pass, webpages, lightning, compiles, libraries, build, lapack, trying, udunits2, spending, learning, constructions, head, fool, errand, compiled, numerically, intensive, tasks, keeping, external, drive, warm, pcmdi, hope, fit, everything, room, spare, reprocess, determined, brightness, static, function, emulating, explore, arise, around, save, diagnose, effect, unforced, perturbed, aid, extracting, hopeful, disk, saved, netcdf4, format, hdf5, compression, sometimes, high, disconnecting, reconnecting, closer, dips, shooting, today, plan, someday, provided, useful, critical, inspiring, along, chance, again, officially, numerous, threats, comeback, thing, worthy, myself, motivate, worked, dozen, spent, radiative, transfer, derived, those, interested, organize, functions, light, home, skip,

Text of the page (random words):
orest formerly the most awesome blog on wordpress trees for the forest formerly the most awesome blog on wordpress skip to content home older posts the forest has burned down posted on february 26 2011 by treesfortheforestblog my numerous threats to make a comeback saw no follow through i have done a lot of work since late last year but i haven t been able to focus on one thing long enough to create something worthy of a post i found myself reading someone else s blog which would motivate me to start working on something new until i read someone else s blog considering all the things i ve worked on i should have at least a dozen interesting posts i spent a lot of time writing fortran r code for a radiative transfer model to take a new look at the model derived msu data i found some issues that those concerned with the model data comparisons would be very interested in i m currently working on an r package to organize my climate data related functions maybe it will see the light of day maybe not my plan is to make a fresh start someday soon thanks to everyone who provided useful critical and inspiring comments to further along my analysis you ll have a chance to do that again soon but for now the forest has officially burned down posted in uncategorized 3 comments almost back posted on september 14 2010 by treesfortheforestblog i m keeping my old external drive warm downloading fresh data from pcmdi i hope i can fit everything i need into 500 gb with room to spare i m going to reprocess the atmospheric temperature and surface temperature data into a more accurately determined synthetic brightness temperature using the global mean static weighting function was fine for emulating santer et al but i d like to explore what differences arise from using other methods this time around i ll save the synthetic msu gridded data into a netcdf file instead of immediately computing spatial averages i m also downloading data for the pre industrial control runs this will allow me to diagnose the effect of unforced model variability on the perturbed simulations 20c3m a1b etc to aid in extracting the true forced temperature change i m hopeful i ll have enough disk space left because any gridded products i create will be saved in netcdf4 format which uses hdf5 compression for most of the day i can get about 200 kb s but sometimes i get as high as 2 mb s i ve been disconnecting reconnecting to get it closer to 1 2 mb s when it dips too low i m shooting for the end of today i m writing this post from my new system it s got an amd athlon ii x4 635 processor with 6 gb of memory and a fast graphics card running ubuntu lucid lynx it s a major step from the 5 year old slug paced piece of garbage i was forced to pass off as a computer webpages load lightning fast software compiles much faster i ve gotten all of my libraries build lapack netcdf etc i m currently trying to interface fortran with udunits2 i ll be spending much time learning c because there are a lot of data types and constructions that go way over my head if this interface turns out to be a fool s errand i may break down and write most of my programs in r and load compiled fortran code to take down the more numerically intensive tasks only 20 gb of data left to download posted in uncategorized 8 comments not blogging lately part 2 posted on july 26 2010 by treesfortheforestblog the forest has been quiet for quite some time now i ve been very busy working on multiple climate related projects you ll read about one pretty soon my lack of blogging is also because i ve lost some interest and inspiration for topics to cover i ve done a lot of reading on data homogenization so my next few posts will hopefully be on that topic much of the work that i ve done in the past few weeks is thanks to my half hearted migration to ubuntu linux i have to say that writing code on a linux machine has been a lot easier in many ways for me than doing it on winxp using mingw i say half hearted because ubuntu specifically x likes to crash because my video card apparently isn t entire supported although in between crashes i ve learned to focus and get as much done before the screen suddenly goes black speaking of which i better hit publish now before the computer cra posted in uncategorized 9 comments better late than never posted on may 19 2010 by treesfortheforestblog i m sure many of you have taken notice of my absence i ve been very busy working on other projects whose results you may see published sometime in the hopefully near future for the last week or so i ve been writing programs to process the ghcn station data into a gridded product though this has already been done by many i ll show you my results anyhow i ll briefly go over the procedure and then discuss some gridding issues that came up while analyzing the data _ data and methods load the station inventory v2 temperature inv and data v2 mean into memory consolidate each station s duplicate entries if applicable by computing a monthly offset for each station such that the sum of the squared differences between each station after the offset is applied is at a minimum see tamino and roman the offsets align the series which are then averaged together determine which stations are in each gridbox i initially used a 5 x 5 grid consolidate all the stations in each grid box using the same methodology as in step 2 calculate the climatology at each grid point and remove it to get temperature anomalies the base period is 1961 1990 and i require a minimum of 20 years of non missing data to calculate a valid climatological mean calculate spatial averages for the global nh sh and the tropics results normally i would impose a constraint on how much area needs to be represented by non missing values to calculate a valid spatial average unfortunately when i was writing my program i was more worried about getting it work properly and neglected to include a land mask to determine how much land is present in the four regions that i the calculated averages for when i calculated the spatial averages i also made sure to hold on to the summed area represented by the non missing data to see how it varies with the overall average first let s see how my global average compares to the results of jeff id roman m nick stokes zeke and residual analysis my reconstruction is consistent with the others so that gives me confidence that i didn t seriously botch the calculations let s look at the global average over the entire time period 1701 2010 the first 150 years of the series shows much larger variability than the rest of the series most likely this is because the sampling was small enough to allow regional or small scale variability to dominate the global average the area fraction data was of some concern this is the sum of surface area accounted for by grid boxes with non missing data normalized to the total amount of global land area why is it greater one i think this is a non obvious error that everyone who has created a gridded product of ghcn has made if a grid box contains one or more stations and it is completely occupied by land then weighting it according to the surface area of that grid box is correct when there is some ocean present then the weight that is applied is too much let s see how this issue affects the other spatial averages the haphazard weighting affects all the spatial averages but is the strongest in the tropics i re ran the spatial averages using a land mask to properly adjust the area weights and compared the normalized area fraction both ways now the area fraction doesn t take on physically unrealistic values given that many bloggers are now combing the land and ocean data this issue shouldn t be as serious but we still need to know how much land ocean is in a grid box to properly combine land ocean anomalies corresponding to the same grid box this area fraction bias would certainly be reduced by using a finer grid to test this i re ran my program with 2 5 x 2 5 resolution and compared the area fractions as expected using a finer grid reduced the area bias and brought it more in line with the correct figures what difference does this bias incur in the spatial averages and their trends over the course of the 20th century up to the present the bias in the global nh sh averages is statistically significant thought practically negligible in the tropics however the bias is fairly large here s the same data and trends over the most recent 30 year period over the recent period the biases are statistically and practically significant with the most extreme bias occurring in the tropics the trends are positive and this means that the improperly weighted procedure produces anomalies over this period whose trends are too small now see what happens when the spatial averages are calculated on a finer grid over the 20th century up to the present the bias is still of no practical significance over the more recent period the biases are still of some practical significance but not as large here are the spatial averages with the correct weighting and their trends update may 23 2010 the trends below are wrong the uncertainty is one standard error not two as i intended here s the same graph but from the 2 5 x 2 5 data in all regions except the tropics the finer griding brought down the trends why that ll have to be the topic of another post p s does anyone like the new theme _ update may 19 2010 i ve uploaded the annual averages and the fortran code http drop io treesfortheforest as per carrick s request i ve created plots of the weighted mean latitude of all non missing grid cells below are three plots covering three different periods 1701 2010 1850 2010 and 1950 2010 posted in gridded data station data surface temperature record 71 comments theme change and other things posted on march 28 2010 by treesfortheforestblog i ve changed the theme because the old one was getting a bit boring unfortunately this means that i need to resize all of my images because as you can see below they are too big i haven t been blogging lately because i ve been busy doing some serious santer related number crunching still looking for inspiration for my next post radiosondes sound good posted in uncategorized 3 comments second thoughts on methods to combine station data posted on march 6 2010 by treesfortheforestblog in my last three posts on station data here here and here i compared several methods for combining station data i came to some conclusions that on second thought may not be completely founded the products of each method were compared to the true temperature series the way i calculated the true temperature series may have inadvertently biased the results i calculated an area weighted average which is essentially a simple un weighted average given that the locations of the station data were so close together within a 5 x 5 grid box it shouldn t be surprising then that when sam fdm and cam were applied to perfect data all three methods performed very well i might have gotten very different results if i had interpolated the miroc hires grid into a 5 x 5 grid and used that single grid point as a reference i suspect that if i had done that then the rsm wouldn t have come out looking so bad since it itself is a form of interpolation this got me thinking that there may not be a straight forward unbiased way of determining the pros cons of these methods i need to do a lot more thinking about this ideas are welcome posted in uncategorized 12 comments north american snow cover posted on march 4 2010 by treesfortheforestblog after reading about steve goddard s snowjob i thought i d take a much need break from my current research topic time of observation bias to take a look at north american snow cover extent na sce one of goddard s posts discussed results from frei and gong 2005 fg hereafter this paper compared observed na sce to ar4 climate model simulation results because different models have different spatial resolution the total north american land area km 2 would be different from model to model so the authors normalized the snow cover relative to the total land area of north america na sce were only available for 11 models when this paper was published i checked cmip3 and there are now 16 models with 59 runs fg defined na sce as the fraction of land area bounded by 190 340 e and 20 90 n covered with snow by this definition greenland is included figure 1 shows the exact spatial extent figure 1 north american continental land mass plus greenland the legend is the fraction of the gridcell that contains land the figure is based on a land mask created by carl mears at remote sensing systems rss to process the original gridded data the first step is to calcluate the normalized area weights for a given model s grid these weights are then multiplied by the model s land mask to zero out the grid points in the ocean unfortunately mri cgcm 2 3 2a didn t have a land mask available i created one by interpolating the same land mask shown in figure 1 into mri s spatial resolution the next step is to take the subset of the masked area weights on the defined latitude longitude bounds and sum up all the values this represents the total land area of north america including greenland as a fraction of the earth s surface area to calculate the fractional na sce for each time step i loaded the gridded data one time step at a time zeroed out the missing values multiplied by the land mask and the area weights i took the sum upon the defined latitude longitude extent the resulting sum represent the fraction of the earth s surface covered in snow after processing all the time steps i divided the resulting time series by the total fractional land area to convert the units into fractional land area coverage of north america greenland to check to see how well i emulated the process i consulted a csv file posted by zeke hausfather he obtained from frei containing january na sce for nine models running 20c3m a1b i took the difference between my and frei s series and found pretty good agreement to an extent figure 2 shows a comparison with giss aom figure 2 comparison of giss aom over the 20c3m and a1b periods my numbers underestimate the snow extent relative to frei gong s numbers by about 4 shortly into the a1b period there is significant divergance the year to year flucuations in january snow extent are similar i don t see any obvious reasons why both calculations would show similar variability yet differ in trend during the a1b period the fact that the divergance segment is declining means that my series is declining faster than frei gong s which makes me think that their post 20c3m series isn t running a1b the next model is giss eh figure 3 figure 3 comparison of giss eh over the 20c3m and a1b periods the year to year variations are somewhat similar but too different for comfort looking at fg 2005 i see that they used 5 20c3m runs and 4 a1b runs the data i got from cmip3 indicates that there re o...