summary - clette & lockwood triad · 2018. 2. 2. · issi team meeting #1 issi, berne, 22-26...

ISSITeamMeeting#1ISSI,Berne,22-26Jan.2018 GregKopp- p.1Clette &Lefévre andLockwoodetal.Triad

Lockwood/Kopp/Clette Triad• TriadMembers:FrédéricClette,EdCliver,GregKopp,LaureLefèvre,MikeLockwood,MattOwens• Meetings– 7-8Feb.2017atUniv.ofReading– 12-15June2017atRoyalObservatoryofBelgium


TemporalRegionsandCorrectionsConsidered• WaldmeierCorrection– Clette’s non-linearanalysisgives17%– Lockwood’scomparisonstoothersolar-activityindicatorsgive12%– Svalgaard’s backbonegives20%

• Wolf-SchwabeTransition– Opposing14%jumpsarelargeandaffectpreceding150yearsofSNrecord– Howuniquearethesejumpsinoveralltimeseriesofratios?

• Wolf-Wolfer Transition– Progressivetransition,butlarge(~0.6)


WaldmeierCorrection• WaldmeierprogressivelyaddedweightedcountstoSSN,leadingtohighercountsthanWolfseries– Weightedspotsfrom1-5basedonsize,penumbralarea,clusters,location– Onsetnotwelldocumented

• Effectestimatedbasedonindependentindicators– SunspotareasfromRGO,SNfromotherobservers,geomagneticfield– Lockwoodetal.:RGOspotarea,ionosphericsounders• RGOunderestimatedareaupto40%overmuchoftimefrom1882to1915used• Soundersstartedonlyin1932


WaldmeierCorrection – Clette &Lefèvre2636 F. Clette, L. Lefèvre

Figure 2 Comparison of the original sunspot-number [SN] and group-number [GN] series and of the cor-rected sunspot- and group-number series. All four series are plotted in the upper panel, showing the overallevolution of the solar cycle. To better illustrate the differences between the two pairs of series, the lower paneldisplays the SN/GN-ratios for the original series (Ri/RG, red line) and for the corrected series (green line).In the latter case, the new SN is identical to the original series Ri , except for the correction of the Locarnodrift after 1981, while the new GN is the “backbone” group number GN from Svalgaard and Schatten (2016).The two series agree closely during the shaded time interval, but diverge significantly before and after it asa result of the known inhomogeneities in the original series (see main text). The vertical-dashed line marksthe Waldmeier jump, while the horizontal red- and green-dashed lines show the average ratios for the originaland new series, respectively, during the 1872 – 1946 and 1947 – 1995 intervals.

transition, but replaced the original group number by the reconstructed “backbone” groupnumber [GN] from Svalgaard and Schatten (2016), normalized to the original RG-series overthe interval 1874 – 1947. This recent “backbone” group number does not use the Greenwichphotographic data as reference and therefore does not suffer from the above-mentioned driftbefore 1915. For the original group number, we use the RG-series by Hoyt and Schatten(1998a,b), which is directly based on the Greenwich catalog. Likewise, we replaced theoriginal Ri by this same series corrected only for the 1981 – 2015 Locarno drift (correctionnormalized to the whole 1945 – 2015 interval as described above in Section 3). The compar-ison between the two pairs of series and the two corresponding ratios is shown in Figure 2.

The large upward deviation before 1915 is shown as a shaded area. Thereafter, the orig-inal and new series match closely until 1981, when a smaller discrepancy appears, cor-responding to the Locarno drifts affecting the Ri-series. We then determined the averageratios between each pair of series before and after 1947 using six different methods ascross-validation, in the same manner as for our earlier 1981 – 2015 sunspot-number recon-structions (Article 2). We find that the original average before 1947 is 5 % higher than whenusing corrected series. After 1947, the original average ratio is only slightly higher than withthe corrected sunspot-number series, by barely 1 %, confirming that for this time period, theupward and downward drifts mostly compensate for each other in the global average. Takingthe ratio between these two averages to determine the jump amplitude, we thus find that thelow ratio of 1.126 derived by LOB2014 was underestimated by 4 %, due entirely to over-looked inhomogeneities in the base data series. A similar result, but with larger uncertainties,is obtained by using the original series, but restricting the analysis to the homogeneous in-terval 1915 – 1980 (shaded interval in Figure 2). With cleaned series, we thus find a newhigher ratio of 1.17 ± 0.01 that agrees much better with the other determinations.

17%jumpappliedin1947(Clette &Lefèvre,2016)

(Locarnocorrectionsonly)

RGOGNunderestimated


2794 M. Lockwood et al.

Figure 2 Scatter plots of noon foF2 values measured at Washington, DC, USA as a function of sunspotnumber [R], for 1933.5 – 1944 (Cycle17, mauve dots), 1944 – 1954.5 (Cycle 18, black squares), and1954.5 – 1964.5 (Cycle 19, blue triangles). Data are 12-point running means of monthly data. The lines arethird-order-polynomial fits in each case.

i) Comparison with data from Washington for Cycle 19 shows that the drift in the foF2–R relationship continued after the Waldmeier discontinuity (giving the 7.5 % differencebetween Cycles 18 and 19 in Figure 2).

ii) Smith and King (1981) studied the changes in the foF2–R relationship at a number ofstations (at times after the Waldmeier discontinuity). For all of the stations that theystudied, these authors found that foF2 varied with the total area of white-light faculae onthe Sun, as monitored until 1976 by the Royal Greenwich Observatory, as well as withsunspot number. Furthermore, these authors showed that the sensitivity to the faculareffect was a strong function of location and that, of the six stations that they studied, itwas greatest for Washington, DC and that it was lowest for Slough.

The location-dependent behaviour found by Smith and King (1981) is common in theionospheric F-region. Modelling by Millward et al. (1996) and Zou et al. (2000) has shownthat the variation of foF2 over the year at a given station is explained by changes to twokey influences: i) thermospheric composition (which is influenced by a station’s proximityto the geomagnetic pole) and ii) ion-production rate (which is influenced by solar zenithangle and the level of solar activity). The composition changes are related to other location-dependent effects, such as thermospheric winds, which blow F2-layer plasma up or downfield lines where loss rates are lower or higher, and this effect depends on the geomagneticdip. For Slough, the annual variability in composition dominates the zenith-angle effect,resulting in the variation of foF2 being predominantly annual. However, at other locations,at similar geographic latitudes but different longitudes, a strong semi-annual variation isboth observed and modelled, caused by the compositional changes between Equinox andWinter months being relatively small compared with the effect of the change in solar zenith

WaldmeierCorrection – Lockwoodetal.2016• DetermineWaldmeiercorrectionbasedonionosphericF2layercomparedtoSNpriortoandafter1945asfunctionofUT• ComparetoZürichSN,newbackboneGSN,andnewSNproposedbyLockwoodetal.2014• Usestimeperiods1874-1945,1945-1976,and1945-2012• Considersnon-linearcorrelationsandnon-zerolinearscalings

11.6%jumpappliedin1945(Lockwoodetal.,2016)

1933.5–1944(Cycle17,mauvedots)1944–1954.5(Cycle18,blacksquares)

1954.5– 1964.5(Cycle19,blue triangles)


WaldmeierCorrection – MyQuickLook• RatiotoHoyt&Schatten GNis13%higherfrom1947to1980thanfrom1900to1947


WaldmeierCorrection – TriadConclusions• CorrectionusedinV2.0,saturatingatamaximumvalueof1.177athighsolar-activitylevels,isappropriate,consistentwithinuncertaintieswithmostpublishedvalues,andavoidsmakingthesunspot-numberrecorddependentonothersolar-activityproxies2640 F. Clette, L. Lefèvre

Figure 5 Weighting inflationfactor [fW] as a function of R∗

i ,the original sunspot number(including the weighting effect)scaled without the 0.6 Zürichfactor. Daily values wereaveraged over equal binsspanning 10 Ri units. Thestandard error of the means aregiven by the error bars. Thebrown-dashed line on the left is alinear fit to the values belowR∗

i = 50. The green solid line isthe corresponding fit forR∗

i > 50, while the green-dashedline gives the average fW-factorduring that same interval.

for the eyepiece counts, with SW and SU designating the weighted and unweighted sunspotnumber, respectively.

Therefore, we can conclude that the two sets agree within the uncertainties, and no sys-tematic difference can be found between the counts derived from the drawings and the cor-responding eyepiece counts.

Following this verification, we applied our analysis to the larger dataset that is based onrecounted drawings, as it also spans a longer duration, including sections of past solar cyclesthat reached higher values of the sunspot number. However, as earlier cycles reached evenhigher peak values of the sunspot number, in particular Cycles 18 and 19, which immediatelyfollowed the 1947 Waldmeier transition, the relation that we can derive from this morerecent period needs to be extrapolated above the observed range of Ri-values, which requiresparticular care.

Working on yearly means of the original Ri and of the inflation factor [fW] derivedfrom the double counts, L. Svalgaard had derived a preliminary linear relation published inArticle 1:

fW = 1.123(±0.006) + Ri/1416(±140), (5)

with Ri the original sunspot number that includes the sunspot-weighting effect.This relation confirmed the expected increase of fW with Ri, but it also permitted high

values of fW (>1.25) for the highest cycles, i.e. well above several estimates coming fromcomparison with parallel data series. To better establish the relation between fW and Ri, weconsider here the individual daily pairs of values, without any temporal averaging. Figure 5shows the resulting distribution of fW as a function of R∗

i = Ri/0.6 (the original Ri-seriesdivided here by 0.6 in accordance with the new scaling convention for the entire sunspot-number series, see Section 2). Daily fW-factors show a very large dispersion. However, aswe collected a very large number of values, we binned the values according to the R∗

i -valuein intervals of 10 Ri units for clarity, which led to rather precise mean values. The standarderror is typically between 1 and 2 %, except for the highest R∗

i for which the number ofavailable data drops steeply.

These mean points show an initial steep rise from about 1 to 1.18 for low Ri-values up toR∗

i = 50. The linear fit over that range leads to

fW = 1.07(±0.02) + 0.0021(±0.0006)R∗i . (6)

Basedondoublecounts(Clette &Lefèvre,2016)

Clette 2017


WaldmeierCorrection – TriadConclusions• TriadconfirmsuseofClette&Lefèvre(2016)correction– Correction,appliedin1947,isnon-linear,rangingfrom10%atlowactivitylevelsto17.7%maximumathigh,spanningmostotherpublishedcorrections

– Uncertaintiesare~3.5%,overlappingwithmostotherpublishedcorrections– Correctionkeepssunspot-numberrecordindependentofproxies– ConsistentwithLockwoodetal.resultsbasedonproxycomparisons

• Possiblefutureeffortsthatmaintainemphasisonsunspotnumber– Continueacquiringdirectdoublecounts(standardandweightedcounts)– Re-counttheoriginalZürichdrawings(1930sto1960s)– Buildasunspot-numberseriesusingmultipleparallelsunspotobservers– Gathermorehistoricalevidencefromoriginallogbooks– Considergradualtransitionratherthanstepfunctionin1947


WaldmeierCorrection – Effect


Wolf-SchwabeTransition• SchwabeprovidedSNfrom1826-1867,overlappingwithWolf• GNHS andGNSS aresmoothoverthistimerange

21%jumpin184914%jumpin1863

(Clette &Lefèvre,2016)

Schwabecountedprogressivelymorespotsinearlypartof

observations


Wolf-SchwabeTransition – MyQuickLook• De-weightingsolarminima,ratiotoHoyt&Schatten GNis– 9%higherfrom1826to1849thanfrom1849to1865– 5%higherfrom1865to1885thanfrom1849to1865


Wolf-SchwabeTransition – Effect• These14%jumpsarelargeandaffectpreceding150yrs ofrecord• Needtoquantifybothjumpsstatistically,particularlylatter• Benefitfromdata-recoverywork


Wolf-SchwabeTransition – TriadConclusions• Transitions’timingandmagnitudein1849and1864plausible• Quantitativedeterminationofcorrectionsisuncertain• Theuncertaintiesarenotaccuratelydetermined


Wolf-Wolfer Transition• Large(60%)effect• IdentifiedbyWolfer atthetime Wolfer 1895


Recommendations&Summary• WaldmeierCorrection – UseClette’s 17%Correction– Uncertaintiesduetoobservers’countingmethodsarelargerthandifferences– Clette’s non-linear17%ismid-rangebetweenLockwood’soriginal12%(basedoncomparisonstoothersolar-activityindicators)andSvalgaard’s 20%(usingbackbone)

• Wolf-SchwabeTransition – LaterJumpNotImmediatelyConvincing– Howuniqueisthisjumpinoveralltimeseriesofratios?Doesitstandout?– Evaluatesolar-cycle-weightedtimeseriesbeingblindtochangesinobservers

• Wolf-Wolfer Transition(lateaddition)– Bringintomoderneratomatchcurrentobservations– Butrefinepre-Wolfer correctionvalue,asthisisaprogressiveandlarge (0.6or0.55) transition


RelativeUncertaintiesBetweenTimesNeedtoBeExpressedin2D

summary - clette & lockwood triad · 2018. 2. 2. · issi team meeting #1 issi, berne, 22-26...

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