LETTER • OPEN ACCESS
Do clima e eleconnec ions modula e wild i e-p one condi ions o e he
Ibe ian Peninsula?
To ci e his a icle: Ma cos Rod igues e al 2021 En i on. Res. Le . 16 044050
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LETTER
Do clima e eleconnec ions modula e wild i e-p one condi ions
o e he Ibe ian Peninsula?
Ma cos Rod igues1,2,8,∗, Dhais Peña-Angulo3, Ana Russo4, Ma ía Z´
uñiga-An ón5
and Ad i´
an Ca dil2,6,7
1Depa men o Ag icul u al and Fo es enginee ing, Uni e si y o Lleida, Lleida, Spain
2Join Resea ch Uni CTFC—AGROTECNIO—CERCA, Solsona, Spain
3Ins i u o Pi enaico de Ecología, Consejo Supe io de In es igaciones Cien í icas (IPE–CSIC), Za agoza, Spain
4Ins i u o Dom Luiz (IDL), Faculdade de Ciˆ
encias, Uni e sidade de Lisboa, Campo G ande, 1749–016 Lisboa, Po ugal
5GEOT G oup, IUCA, Depa men o Geog aphy and Te i o ial Planning, Uni e si y o Za agoza, Za agoza, Spain
6Depa men o C op and Fo es Sciences, Uni e si y o Lleida, Lleida, Spain
7Technosyl a Inc, La Jolla, CA, Uni ed S a es o Ame ica
8GEOFOREST G oup, IUCA, Depa men o Geog aphy and Te i o ial Planning, Uni e si y o Za agoza, Za agoza, Spain
∗
Au ho o whom any co espondence should be add essed.
E-mail: ma cos. od [email p o ec ed]
Keywo ds: wild i es, clima e eleconnec ions, i e dange , bu ned a ea, Ibe ian Peninsula
Supplemen a y ma e ial o his a icle is a ailable online
Abs ac
Clima e eleconnec ions (CT) synch onize and in luence wea he ea u es such as empe a u e,
p ecipi a ion and, subsequen ly, d ough and uel mois u e in many egions ac oss he globe.
CTs hus may be ela ed o cycles in wild i e ac i i y, and he eby help i e manage s o an icipa e
i e-p one wea he condi ions as well as en isaging hei u u e e olu ion. A wide numbe o CTs
modula e wea he in he Ibe ian Peninsula (IP), exe ing di e en le els o in luence a di e en
spa ial and seasonal scales on a wide ange o wea he ac o s. In his wo k, we in es iga ed he link
be ween he mos ele an CT pa e ns in he IP and i e ac i i y and dange , explo ing di e en
spa ial and empo al scales o agg ega ion. We analyzed a pe iod o 36 yea s (1980–2015) using
his o ical eco ds o i e e en s (>100 ha bu ned) and he Canadian Fi e Wea he Index (FWI).
C oss-co ela ion analysis was pe o med on mon hly ime se ies o CTs and i e da a. Resul s
poin ed owa ds he No h A lan ic Oscilla ion (in he wes e n hal o he IP) and Medi e anean
Oscilla ion Index (along he Medi e anean coas ) as he key CTs boos ing bu ned a ea (BA) and
i e wea he dange in he IP. Bo h CTs ela e o he ela i e posi ion o he Azo ean an iclone,
os e ing haza dous i e wea he condi ions du ing hei posi i e phases, i.e. low ain all and wa m
empe a u e leading o low uel mois u e con en . The Scandina ian pa e n index also played an
impo an ole in he wes e n hal o he Peninsula, linked o a dec ease in ain all du ing i s
nega i e phases. None heless, he associa ion be ween he CTs and BA (up o 0.5 Pea son’s R
p< 0.05) was weake han he obse ed be ween CTs and FWI (up o 0.75 Pea son’s R p < 0.05).
1. In oduc ion
Modes o sea su ace empe a u e (SST) and associ-
a ed clima e eleconnec ions (CT) a e known o in lu-
ence and synch onize wea he om sub-con inen al
o local scales [1], including empe a u e, p ecipi a-
ion and, subsequen ly, d ough [2–4]. These wea he
ea u es ha e a s ong impac on he occu ence and
beha io o wild i es, by al e ing uel mois u e and
igni ion p obabili y o igge ing ligh ning i e e en s
[5–9]. The ole o clima e- ela ed ac o s is expec ed
o s eng hen in he u u e, se ing a con ex in which
CTs a e expec ed o ampli y hei e ec s [10–12].
Se e al au ho s ha e conduc ed esea ch in o
CT pa e ns and hei ela ion wi h clima ic a i-
ables a di e en empo al and spa ial scales wo ld-
wide [13–16] and, speci ically, in he Ibe ian Pen-
insula (IP [17–21]); one o he mos i e-a ec ed
egions in Medi e anean Eu ope [22]. A wide ange
o CTs in luence wea he ac o s in he Wes e n
© 2021 The Au ho (s). Published by IOP Publishing L d
En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
Medi e anean basin [23], namely he No h A lan ic
Oscilla ion (NAO), he A lan ic Mul idecadal Oscil-
la ion (AMO), he Eas A lan ic (EA) eleconnec-
ion pa e n index, he ‘Niño’ 3.4 SST index (ENSO),
he Medi e anean Oscilla ion (MOI), he Paci ic
Decadal Oscilla ion (PDO), he Scandina ian pa -
e n (SCAND) and he Wes e n Medi e anean oscil-
la ion (WeMOi). Fo ins ance, he annual amoun
o ain all was signi ican ly linked o he WeMOi,
EA, NAO, ENSO, whe eas blocking episodes in he
IP we e linked o SCAND pa e ns [24]. The sea-
sonal and spa ial a iabili y in mean empe a u e was
also associa ed o he di e en phases o CTs. The
NAO and EA pa e ns we e posi i ely co ela ed wi h
annual mean empe a u e in he IP. In u n, he co -
ela ion be ween WeMOi and empe a u e depic s a
g adien , being nega i e in he no h bu posi i e o e
he Medi e anean coas [18]. Mo eo e , he AMO
has been epo ed o con ol he a iabili y in sum-
me leng h o e Eu ope, pa icula ly a e 1979 [25].
Ex ensi e esea ch has been de o ed o un a el-
ling he link be ween CTs and i e ac i i y, showing
how changes in wea he media ed by CTs can di ec ly
impac bu ned a ea (BA) in many egions ac oss he
wo ld [23,26–34]. The analysis o he e ec s o CTs
on wea he , i e dange and ac i i y is no s aigh o -
wa d [35] as hey a e non-s a iona y and associa ions
may a y o e space a sub-con inen al scales. Like-
wise, me hodological app oaches a y depending on
he pu sued goals. Co ela ion and eg ession analysis
using ime se ies [23,33–35] and - es [36] we e e-
quen ly applied when dealing wi h ‘local’ spa ial pa -
e ns, while mo e sophis ica ed echniques (wa ele
cohe ence o supe posed epoch analysis) ha e been
used o p o ide in-dep h insigh s a sub-con inen al
scales [32,37–39]. Some s udies op ed by analyzing
he in luence o clima e on i es based on ci cula ion-
wea he pa e ns [5,6,40] o local-scale wea he
o cing condi ions [41]. Recen ad ances in Global
Clima e Models (GCMs) o e an al e na i e o s a -
is ical app oaches [42] hough uncommon in he li -
e a u e [38,39]. Howe e , aw GCM’s ou pu s canno
be di ec ly used o quan i a i e wild i e e alua ions.
Sys ema ic biases o he models om o he obse ed
clima e leads o signi ican de iancies o i s s a is ical
p ope ies [43]. Fu he mo e, hei coa se spa ial es-
olu ion is usually no sui able o add essing he local
i e-wea he condi ions [42].
Howe e , s udies add essing CTs and wild i es in
he Medi e anean Eu ope a e sca ce, e en hough
he unde s anding o he clima e- i e dependen ela-
ionships would allow an icipa ing i e dange , hus
imp o ing p e en ion and p epa edness (e.g. s a-
egically a ange supp ession esou ces o educe uel
loads).
Mul iple ac o s may exe an in luence in i e
ac i i y and i e wea he . As a consequence, he IP
is qui e di e se in e ms o i e egimes and i s
unde lying d i e s, which a y ac oss ime and space
[44–46]. A ecen wo k by [23] epo ed no iceable
co ela ion be ween SCAND, NAO and MOI/WeMOI
in Spain and Po ugal, hough hei CT- ela ed ana-
lyses we e conduc ed a he na ional (coun ywide)
and yea ly scales in di e en ime ames (s a -
ing in he 70s un il 2017). None heless, he e is
e idence o CT in e ac ions modula ing and exace -
ba ing wea he a iabili y [32,36,37], subsequen ly
in luencing i e ac i i y [47]. Howe e , he e is no a
clea pic u e o he e ec s o CT on i e ac i i y in he
IP, and speci ically on he coupled e ec s o CTs, on
i e ac i i y a mul iple empo al scales o agg ega ion.
The e o e, wi h his pape we in end o ill he
e e ed lacunae, aiming a iden i ying he in luence
o he mos signi ican SST modes and CTs, indi idu-
ally o coupled, a ec ing i e dange and ac i i y in
he IP. We de eloped a no el amewo k o un a el
he spa ial pa e ns o he mos in luen ial CTs while
iden i ying syne gies and empo al scales modula -
ing hei signal. We u he ex end o e o me ana-
lyses by digging in o he spa ial dis ibu ion o he
links be ween wild i es and CTs, p o iding a ans-
bounda y assessmen using homogeneous i e egime
zones, deepe insigh s in o mon hly and seasonal
associa ions, and inco po a ing wild i e dange a ing
indices in o he assessmen . Speci ically, we add ess
he ollowing esea ch ques ions: (a) how do CTs
ela e o me eo ological i e-wea he a ing indices
and i e ac i i y? (b) do CT-wild i e ela ionships a y
o e space? (c) a e he e coupled e ec s among CTs
leaning owa ds a empo al window wi h highe i e
dange and/o ac i i y? (d) is he e ec o CTs indices
on i e dange and i e ac i i y lagged in anyway?
2. Ma e ials and me hods
2.1. Da a
2.1.1. Fi e da a
His o ical i e da a was e ie ed om he Spanish
EGIF (‘Es adís ica Gene al de Incendios Fo es ales’)
[48] and Po uguese DECIF (‘Disposi i o Especial
de Comba e a Incˆ
endios Flo es ais’) [49] o icial i e
da abases. We compiled a ha monized da ase ga h-
e ing i e eco ds om bo h da abases. Acco ding o
Pe ei a e al [49], i es below he 100 ha h eshold
we e no compiled consis en ly du ing he 80s. To
ensu e he homogenei y (missing eco ds, lack o
in o ma ion, e c) in he inal i e da ase , we selec-
ed only hose i e e en s la ge han 100 ha in he
pe iod 1980–2015. Addi ional in o ma ion including
he s a ing loca ion (a NUTS3 le el) and he da e
o igni ion was also e ie ed om i e da abases o
enable u he analyses.
Fi es we e o ganized acco ding o hei py o e-
gion o o igin (see igu e 1) as ou lined by T igo e al
[44], who de ined ou mac o egions wi h homo-
geneous i e egimes (N: No h, NW: No hwes , SW:
Sou hwes and E: Eas ). Then, i e e en s we e agg eg-
a ed on a mon hly basis in e ms o BA.
2
En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
Figu e 1. Desc ip ion o he s udy egion. (A) Spa ial dis ibu ion o numbe o i e e en s and no malized bu ned a ea (bu ned
a ea di ided by egion size) a NUTS3 le el, 1980–2015; (B) physical map o he Ibe ian Peninsula.
2.1.2. Fi e wea he dange
We used he Canadian Fi e Wea he Index (FWI)
as an indica o o i e-conduci e wea he condi-
ions. The FWI [50] is a nume ical a ing sys em
ha summa izes he chances o a i e o igni e
and p opaga e, widely used o moni o and o esee
haza dous condi ions (e.g. he Eu opean Fo es Fi e
In o ma ion Sys em). I is based on a combina ion o
componen s buil -up om aw wea he in o ma ion
such as ela i e humidi y, accumula ed ain all in he
las 24 h, empe a u e and wind speed. The FWI da a
we e gene a ed by he Eu opean Cen e o Medium-
Range Wea he Fo ecas s om he ERA5 eanalysis
da ase [51]. Daily g ids o FWI a 0.25◦ esolu ion
we e e ie ed om he Cope nicus Clima e Sys em
(C3S), la e agg ega ed in o mon hly ime se ies as he
mean FWI pe mon h and g id cell. No e ha he g id
cell se ed as spa ial uni o analysis in FWI analyses
whe eas BA was add essed a egion le el.
2.1.3. Clima e eleconnec ions
We chose he mos impo an CT pa e ns (a
mon hly le el) in he Wes e n Medi e anean Basin
based on p e ious s udies ([2,24,44,49,50];
able S1 (a ailable online a s acks.iop.o g/ERL/16/
044050/mmedia)): NAO, AMO, EA, ENSO (El Niño),
MOI, PDO, SCAND, and WeMOi.
The NAO pa e n has been quan i ied by means
o he dipole-like s anda dized su ace p essu e
di e ence be ween he No h A lan ic Sub opical
High (whose da a can be aken om Pon a Delgada-
Azo es, Lisbon o Gib al a ) and a second s a ion
close o he Icelandic Low (Reykja ik) [52]. The pos-
i i e phase in ol es a subs an ial de elopmen o a
low p essu e cen e in Iceland and a high p essu e
cen e o e he Azo es, which is associa ed o below-
no mal ain all o e sou he n Eu ope. The oppos-
i e pa e n is ound du ing nega i e phases, when
he Icelandic Low and he Azo es High a e weake
han usual. The EA is s uc u ally simila o NAO.
I consis s o a no h–sou h dipole o anomaly cen-
e s spanning he No h A lan ic om eas o wes
[53]. The posi i e phase o EA is associa ed wi h
a wa m condi ions in Wes e n Eu ope and below-
a e age p ecipi a ion ac oss sou he n Eu ope. The
AMO pa e n is de ined as a de ended a e age o
3
En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
SST anomalies in he No h A lan ic [54]. The pos-
i i e phase o he AMO is associa ed wi h inc eased
mean su ace ai empe a u e, especially p onounced
o e No h Ame ica and Eu ope du ing summe [55].
The SCAND consis s o a p ima y ci cula ion cen e
o e Scandina ia, wi h weake cen e s o opposi e
sign o e wes e n Eu ope and eas e n Russia/wes e n
Mongolia [54]. The posi i e phase o SCAND is
associa ed wi h abo e-a e age p ecipi a ion ac oss
cen al and sou he n Eu ope. The MOI was de ined
in o de o explain opposing a mosphe ic dynam-
ics be ween he wes e n and eas e n sec o s o he
Medi e anean basin. The MOI is ma ked as he no -
malized p essu e di e ence be ween Algie s and El
Cai o [53]. A second e sion o his index can be
calcula ed as he di e ence o s anda dized p essu e
anomalies a Gib al a and he Is aeli me eo ological
s a ion o Lod. The WeMOi pa e n is calcula ed as
a s anda dized p essu e di e ence be ween no he n
I aly (Padua) and sou he n Spain (San Fe nando).
The posi i e phase is cha ac e ized by he an icyc-
lone o e he Azo es and a low-p essu e cen e o e
he Gul o Genoa; he nega i e phase comp ises he
Cen al Eu opean an icyclone loca ed in he no h
o I aly, and low-p essu es in he Gul o Cadiz [24].
The ENSO/‘Niño’ 3.4 SST index was calcula ed om
he HadISST1 as he a e age o SST anomalies o e
he egion om 5◦S–5◦N o 170–120◦W [56]. The
PDO is mos equen ly e e ed o as a long-li ed
El-Niño like pa e n o he Paci ic clima e a iabili y.
The PDO pa e n is de i ed as he leading p incipal
componen (PC) o mon hly SST anomalies in he
No h Paci ic Ocean, polewa d o 20◦N [57].
2.2. S a is ical analyses
2.2.1. PC analysis
PC analysis (PCA) o mon hly ime se ies o CTs
was applied o add ess po en ial synch onic e ec s
o in e ac ions be ween hem, and o build a smal-
le subse o CT indices. PC we e selec ed acco ding
o he Kaise c i e ion, i.e. e aining hose PCs wi h
s anda d de ia ion highe han 1 [56]. The con ibu-
ion o each CT o each PC was add essed ia a -
imax o a ion [58]. PCA loadings and sco es we e
subsequen ly compa ed o mon hly ime se ies o BA,
analyzing each egion sepa a ely.
2.2.2. C oss-co ela ion ime se ies analysis
The co e o ou s a is ical analysis is based on he
calcula ion o Pea son’s c oss-co ela ion R coe i-
cien s a mul iple empo al and spa ial scales. Pai ed
mon hly ime se ies o BA, CTs and FWI we e
explo ed o in es iga e he lagged associa ion o BA
and CTs, and FWI and CTs, espec i ely. Fou di -
e en iming windows o FWI and BA we e in es ig-
a ed (Ap il–June, AMJ; May–July, MJJ; June–Augus ,
JJA; and July–Sep embe , JAS) o accoun o po en-
ial di e ences be ween ea ly o la e summe condi-
ions ( igu e 2). Se e al lag in e als (i.e. synch ony,
Figu e 2. Illus a ion o empo al scales o agg ega ion.
O ange indica es he empo al window o FWI o BA (JJA
in he example). (A) 3 mon h agg ega ion (scale) o CTs,
wi h lag 0 (synch onic o FWI/BA); (B) 4 mon h scale,
lag 0; (C) 5 mon hs scale, lag −1; (D) 6 mon h scale, lag −2.
om 0 o 6 mon hs be o e) and scales o agg ega ion
( om 3 o 6 a e aged mon hs) o CTs wi h BA and
CTs we e analyzed (see igu e 2).
S a iona i y in he ime se ies was es ed be o e
he co ela ion analysis was pe o med using he Aug-
men ed Dickey–Fulle es [57]. Those se ies ound
non-s a iona y we e de ended by sub ac ing he
end componen a e applying a Seasonal-T end
decomposi ion [59]. Co ela ions be ween BA and
coupled CTs we e add essed a egional le el, calcu-
la ing he co ela ion be ween 3 mon h a e aged BA
( o accoun o a season-like ime span) and PCA’s
sco es. BA assessmen s we e conduc ed in he ou
i e egions ( igu e 1) sepa a ely. Co ela ion ou pu s
o BA we e o ganized based on he combina ion o
egion and ime window, epo ing he mos co -
ela ed lag and scale ( able 2). Co ela ions be ween
FWI and indi idual CTs we e calcula ed a FWI pixel
le el (0.25◦). Co ela ions we e summa ized as a se o
maps epo ing he mos and second mos co ela ed
CT pe pixel ( igu e 4) and i s co esponding ime
window, lag and scale o agg ega ion ( igu e 5).
3. Resul s
3.1. Associa ion be ween CT pa e ns and BA
We e ained ou PCs (labeled om PC1 o PC4)
acco ding o he Kaise c i e ion, explaining 72% o
he o iginal a iance. Each PC depic ed a speci ic
pa e n o associa ion wi h CT eleconnec ion pa -
e ns ( igu e 3; see h ps://c s-ba-ip.ne li y.app [60]
o addi ional ou pu s) ha was cha ac e ized acco d-
ing o he loading con ibu ion o each indi idual
CT p ojec ed o each componen ( able 1). Below we
desc ibe he ou main componen s a ending o he
mos ele an CTs:
•PC1: synch onic MOI, NAO (bo h show a close
loading alue and sign, −0.54) and WeMOi
(−0.38) opposed o he AMO phase (0.30). The
highes he PC’s sco e he lowe he associa ion
wi h MOI/NAO/WeMOi. Likewise, high sco es
poin owa ds a low AMO index.
4

En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
Figu e 3. In e ac ion be ween CTs (PC1 and PC2) and seasonal dis ibu ion o bu ned a ea in he Ibe ian Peninsula (1980–2015).
Colo indica es season whe eas size ela e o bu ned a ea. Each do ep esen s he BA in an indi idual mon h.
Table 1. Summa y o p incipal componen analysis. Sd, s anda d de ia ion; Exp. Va , explained a iance; Cum. Va , accumula ed
a iance. Bold ace indica es signi ican loadings in Va imax o a ion. Loadings highe han 0.4 we e highligh ed in g ay.
Summa y Loadings
Sd Exp. a Cum. a AMO EA MOI NAO ENSO PDO SCAND WeMOi
PC1 1.36 0.23 0.23 0.30 −0.23 −0.54 −0.54 −0.20 −0.23 0.20 −0.38
PC2 1.30 0.21 0.44 −0.47 −0.31 −0.22 −0.25 0.42 0.61 0.15 −0.02
PC3 1.06 0.14 0.58 0.36 0.56 −0.07 0.04 0.58 0.15 −0.06 −0.44
PC4 1.05 0.14 0.72 −0.16 −0.30 −0.04 0.15 −0.08 0.01 −0.79 −0.47
•PC2: his PC summa izes he in luence o PDO
and ENSO (loadings 0.61 and 0.42, espec i ely)
opposed o AMO (−0.47). The highes he sco e
he highes he PDO/ENSO. High sco es ela e o
−AMO phase.
•PC3 ep esen s synch onic (simila loading alue)
ENSO/EA/AMO opposed o WeMOi. High sco es
o he PC indica e high ENSO/EA indices; low
sco es depic ed low WEMOI. High alues ela e o
+AMO phase
•PC4: conjunc ion o SCAND (−0.79) and WeMOi
(−0.47) phases. The highes he PC’s sco e he low-
es SCAND/WeMOi index alue.
PCA e ealed in e es ing pa e ns o associa ion
be ween CTs and he seasonal dis ibu ion o BA
size ( igu e 3; see igu e S1 in supplemen a y ma e i-
als o addi ional biplo combina ions). MOI, NAO,
WeMOi and, o a lesse ex en EA, we e posi i ely
linked o summe BA (mainly in PC1), i.e. he
main i e season in he IP. Likewise, AMO showed
an in e se associa ion, hough sligh ly linked o BA
du ing all.
None heless, spa ial and empo al di e ences
we e obse ed a egion le el since p essu e cen e s
a ec di e en ly he di e en a eas o he IP in e ms
o p ecipi a ion and he e o e ha is e lec ed in e ms
o d ough and ege a ion de elopmen ( able 2). PC1
(MOI/NAO/WeMOi) showed signi ican associa ions
wi h BA in all egions, excep in he SW a ea. Posi -
i e phases o ei he NAO o MOI os e ed inc eased
BA. This associa ion was obse ed consis en ly a
mul iple empo al scales hough i was mo e in ense
a 4–6 mon hs (lag) be o e June. The conjunc ion
o posi i e ENSO and PDO (PC2) was ela ed o an
inc eased BA in ea ly and la e summe in he N (MJJ
and JAS) and, wi h he main i e season in he SW
(JJA). An immedia e associa ion (lag 0) was epo -
ed in he N whe eas he signal was sligh ly delayed in
he SE (3 mon hs lag). Synch onic (lag 0) low WeMOi
index unde posi i e phases o EA and ENSO (PC3)
was associa ed wi h a la ge BA in he E egion. The
wes e n hal o he peninsula (NW and SW) showed
con as ing associa ions be ween ea ly and la e sum-
me . BA in he MJJ pe iod beha ed like he E egion
while he s onges associa ion in JJA and JAS depic-
ed in e se co ela ions in he NW, hus BA co el-
a ion was nega i e ENSO and EA phases and posi -
i e wi h WEMOI. Finally, PC4 (SCAND +WEMOI)
showed nega i e sho - e m (lag 0 and scale 3) co el-
a ions wi h BA in la e summe in all egions excep in
he SW a ea. Con e sely, high WEMOI and SCAND
du ing he win e p io summe was associa ed wi h
an inc eased BA in AMJ.
3.2. The in luence o CTs on i e wea he dange
In o de o comple e he analysis o his o ical i e
incidence we in es iga ed he po en ial associa ion
be ween CTs and FWI ( igu e 4; see h ps://c s- wi-
ip.ne li y.app [61] o see he indi idual maps o CTs’
co ela ion pa e ns). The mos in luen ial CTs we e
MOI, SCAND, NAO, PDO and AMO. MOI, NAO
5
En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
Table 2. Co ela ion coe icien s pe egion, ime window, lag and scale be ween bu ned a ea and CTs. Columns heade s deno e he empo al window o bu ned a ea agg ega ion: AMJ, Ap il–June; MJJ, May–July; JJA, June–Augus ;
JAS, June–Sep embe . E, Eas egion; N, no h egion; NW, no hwes egion; SW, sou hwes egion. Bold alues indica e signi ican co ela ions (p< 0.05). N indica es he numbe o i es analyzed.
AMJ MJJ JJA JAS
Region RLag Scale N R Lag Scale N R Lag Scale N R Lag Scale N
PC1 E0.49 3 5 213 −0.41 4 3 640 −0.45 5 3 1092 −0.48 6 3 1118
N−0.56 6 3 312 −0.42 6 4 258 −0.37 1 5 752 −0.34 3 3 1384
NW −0.50 3 5 247 −0.28 4 3 896 −0.33 3 3 2956 0.42 6 5 3917
MOI/WeMOi
and NAO SW 0.20 6 4 422 0.28 5 5 1745 −0.26 4 5 3665 −0.21 5 3 4231
PC2 E−0.34 6 5 213 0.24 6 5 640 −0.28 5 3 1092 0.32 0 5 1118
N0.38 0 3 312 0.43 1 3 258 −0.31 5 4 752 0.43 0 3 1384
NW −0.26 6 3 247 −0.19 4 4 896 0.33 2 4 2956 0.23 6 5 3917
PDO and
ENSO SW −0.31 1 3 422 −0.22 4 3 1745 0.37 3 3 3665 0.32 4 3 4231
PC3 E0.39 6 5 213 0.19 0 4 640 0.36 0 3 1092 0.40 1 3 1118
N 0.32 5 4 312 −0.28 5 3 258 0.31 2 3 752 −0.20 4 3 1384
NW 0.30 4 5 247 0.47 0 5 896 −0.41 0 3 2956 −0.42 1 3 3917
ENSO.
EA and
AMO SW −0.23 1 4 422 0.38 1 3 1745 −0.27 6 3 3665 0.23 4 4 4231
PC4 E 0.26 6 5 213 −0.34 6 4 640 −0.24 0 3 1092 −0.39 0 3 1118
N0.41 5 3 312 0.40 6 5 258 −0.24 1 3 752 −0.45 0 4 1384
NW 0.32 2 4 247 0.28 4 3 896 −0.29 2 5 2956 −0.38 6 3 3917
SCAND
and
WeMOi SW 0.59 5 5 422 −0.27 0 4 1745 −0.41 6 5 3665 −0.31 5 5 4231
6
En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
Figu e 4. Spa ial dis ibu ion o mos in luencing CTs on FWI. Top mos (A) and second mos (B) co ela ed eleconnec ion.
Bo om, Pea son’s R co ela ion coe icien o mos (C) and second mos (D) co ela ed CT. All co ela ion alues we e
signi ican a p< 0.05.
and AMO displayed a posi i e ela ionship, i.e. he
highe he index he highe he i e wea he dange .
These CTs ela e o sus ained an icyclone condi ions
du ing hei posi i e phases. Con e sely, SCAND and
PDO showed an in e se associa ion pa e n, possibly
linked o he lack o p ecipi a ion du ing hei neg-
a i e phases. The spa ial dis ibu ion o he mos co -
ela ed CTs e ealed a dissimila pa e n ac oss he IP.
The MOI domina es he Medi e anean coas (E) and
he eas e n hal o he SW egion (R> 0.6, p< 0.05),
in e mingling wi h smalle encla es o AMO in he
sou h and SCAND in he no heas . The seasonal
e olu ion o hese CTs, app aised in he supplemen -
a y ma e ials, e eals a s ong and pe sis en in lu-
ence o AMO om June o Sep embe , wi h SCAND
being s onge du ing he cen al summe mon hs
(JJA). In he wes e n hal o he Peninsula (SW and
NW), NAO (R> 0.5, p< 0.05), PDO and SCAND
(R<−0.6, p< 0.05) modes we e he mos co ela ed.
The i s was main ope a ing in ea ly summe (MJJ
a scale 3) whe eas he la e exe ed inc easing in lu-
ence om ea ly o la e summe , especially he PDO,
which a ec s JJA and JAS he mos (see h ps://c s-
wi-ip.ne li y.app).
7
En i on. Res. Le . 16 (2021) 044050 M Rod igues e al
Figu e 5. Spa ial dis ibu ion o empo al pa ame e s o mos in luencing CTs on FWI. Top pe iod wi h highes co ela ion o he
mos (A) and second mos (B) co ela ed eleconnec ion. Mid, scale (numbe o a e aged mon hs) wi h highes co ela ion o
he mos (C) and second mos (D) co ela ed CT. Bo om, lag (mon hs delay) wi h highes co ela ion o hemos (E) and second
mos (F) co ela ed CT. All co ela ion alues we e signi ican a p< 0.05.
8