Biogeophysical impacts of peatland forestation on regional climate changes in Finland
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Biogeosciences, 11, 7251–7267, 2014
www.biogeosciences.ne /11/7251/2014/
doi:10.5194/bg-11-7251-2014
© Au ho (s) 2014. CC A ibu ion 3.0 License.
Biogeophysical impac s o pea land o es a ion on egional
clima e changes in Finland
Y. Gao1,2, T. Ma kkanen1, L. Backman1, H. M. Hen onen3, J.-P. Pie ikäinen1, H. M. Mäkelä1, and A. Laaksonen1,4
1Finnish Me eo ological Ins i u e, P.O. Box 503, 00101 Helsinki, Finland
2Uni e si y o Helsinki, Depa men o Physics, P.O. Box 64, 00014 Helsinki, Finland
3Finnish Fo es Resea ch Ins i u e, P.O. Box 18, 01301 Van aa, Finland
4Uni e si y o Eas e n Finland, Depa men o Applied Physics, P.O. Box 1627, 70211 Kuopio, Finland
Co espondence o: Y. Gao ([email p o ec ed])
Recei ed: 11 June 2014 – Published in Biogeosciences Discuss.: 22 July 2014
Re ised: 10 No embe 2014 – Accep ed: 12 No embe 2014 – Published: 17 Decembe 2014
Abs ac . Land co e changes can impac he clima e by in-
luencing he su ace ene gy and wa e balance. Na u ally
eeless o spa sely eed pea lands we e ex ensi ely d ained
o s imula e o es g ow h in Finland o e he second hal o
20 h cen u y. The aim o his s udy is o in es iga e he bio-
geophysical e ec s o pea land o es a ion on egional cli-
ma e in Finland. Two se s o 18-yea clima e simula ions
we e done wi h he egional clima e model REMO by us-
ing land co e da a based on p e-d ainage (1920s) and pos -
d ainage (2000s) Finnish na ional o es in en o ies. In he
mos in ensi e pea land o es a ion a ea, loca ed in he mid-
dle wes o Finland, he esul s show a wa ming in Ap il o
up o 0.43K in mon hly-a e aged daily mean 2m ai em-
pe a u e, whe eas a sligh cooling om May o Oc obe o
less han 0.1K in gene al is ound. Consequen ly, snow clea -
ance days o e ha a ea a e ad anced up o 5 days in he
mean o 15yea s. No clea signal is ound o p ecipi a-
ion. Th ough analysing he simula ed empe a u e and en-
e gy balance e ms, as well as snow dep h o e i e selec ed
sub egions, a posi i e eedback induced by pea land o es a-
ion is ound be ween dec eased su ace albedo and inc eased
su aceai empe a u ein he snow-mel ing pe iod. Ou mod-
elled esul s show good quali a i e ag eemen s wi h he ob-
se a ional da a. In gene al, dec eased su ace albedo in he
snow-mel ing pe iod and inc eased e apo anspi a ion in he
g owing pe iod a e he mos impo an biogeophysical as-
pec s induced by pea land o es a ion ha cause changes in
clima e. The esul s om his s udy can be u he in eg ally
analysed wi h biogeochemical e ec s o pea land o es a ion
o p o ide backg ound in o ma ion o adap ing u u e o es
managemen o mi iga e clima e wa ming e ec s. Mo eo e ,
hey p o ide insigh s abou he impac s o p ojec ed o es a-
ion o und a a high la i udes due o clima e change.
1 In oduc ion
Clima e esponse o an h opogenic land co e change hap-
pens mo e locally and occu s on a much sho e ime scale
compa ed o global wa ming due o inc eased g eenhouse
gases (GHG) (IPCC, 2013). The in luences on he cli-
ma e om he biogeophysical e ec s caused by land co e
changes can enhance o educe he p ojec ed clima e change
(Ba hiany e al., 2010; Bonan, 2008; Feddema e al., 2005;
Gálos e al., 2011; Gö el e al., 2008; Ge and Zou, 2013;
Pielke e al., 2011, 1998; Pi man, 2003). Especially o
he clima e impac s o pas la ge-scale a o es a ion, s udies
show ha he mos ob ious e ec s o he inc ease o o es s
in bo eal a eas a e wa ming du ing snow-co e pe iods due
o dec eased su ace albedo and cooling in summe ime om
inc eased e apo anspi a ion (ET) in opical a eas wi h su i-
cien soil mois u e (Bala e al., 2007; Be s, 2000; Be s e al.,
2007).
Vas a eas o na u ally eeless o spa sely eed pea -
lands ha e been d ained o g ow o es s o imbe p o-
duc ion in no he n Eu opean coun ies (Päi änen and
Hånell, 2012). In Finland, i is he dominan land co e
change o e he las hal cen u y due o he high ac-
ion o p is ine pea land and he need o imbe p oduc-
ion. The o al pea land a ea o Finland was es ima ed o
Published by Cope nicus Publica ions on behal o he Eu opean Geosciences Union.
7252 Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland
be 9.7millionha in he 1950s (Il essalo, 1956). In he be-
ginning o he 2000s, he a ea o d ained pea land o
o es y was es ima ed o be 5.7millionha by Minkkinen
e al. (2002) and 5.5millionha by Tomppo e al. (2011).
The a ea o d ained pea lands is unlikely o inc ease u -
he because no mo e public subsidisa ion is gi en o
he i s - ime d ainage o pea lands and he inc eased
awa eness o na u al conse a ion (Me sä alouden kehi -
ämiskeskus Tapio, 1997). The a ea o es o ed mi es was
15000ha be ween 1990 and 2008 (h p://www.biodi e si y.
i/en/indica o s/mi es/mi17-mi e- es o a ion) (Kaakinen and
Salminen, 2006). Howe e , land co e change is no only
a esul o human land-use ac i i ies bu can also be a con-
sequence o clima e change. Global wa ming in he u u e
is also conside ed o be a ac o ha a ec s bo eal pea land
h ough wa e -le el d awdown due o inc eased ET (Laiho
e al., 2003; Laine e al., 1995).
A en ion has been paid o he clima e e ec s o pea land
o es a ion. A dec ease in he local nigh - ime minimum em-
pe a u e du ing he g owing season was obse ed oughly o
he i s 15yea s a e d ainage (Solan ie, 1994). The eason
o his noc u nal cooling phenomenon is he insula ion o
lowe soil laye s om he a mosphe e by d y pea . The e-
o e, he hea lux om d ained pea soil can no compensa e
o he adia i e cooling a he su ace, which leads o a d op
in daily minimum empe a u e (Venäläinen e al., 1999). On
alonge ime scale, heg owing o es on o me lyopen pea -
lands leads o a dec ease in su ace albedo. The easons o
his a e he da ke ee co e in compa ison o he ligh e
moss/g ass co e in he snow- ee pe iod and he pa ial snow
co e in o es a eas compa ed o he ull snow co e in open
a eas in he snow-co e pe iod. This inc eases he daily max-
imum empe a u e due o an inc ease in he abso p ion o
sho -wa e adia ion (Solan ie, 1994). Consis en esul s on
he seasonal cycles o su ace albedo and ne su ace so-
la adia ion due o pea land o es a ion we e ound by Lo-
hila e al. (2010), based on measu emen da a a wo pai s
o d ained and und ained pea land si es loca ed in he sou h
and no h o Finland. The esul s showed a no ably dec eased
su ace albedo and co esponding inc eased ne su ace sola
adia ion in sp ing ime. Fu he mo e, Lohila e al. (2010) in-
dica ed he local clima e impac s o pea land o es a ion by
in es iga ing long- e m (1961–2008) sp ing su ace empe -
a u e ends o e sou he n (<65◦N) and no he n (>65◦N)
Finland. The la ges posi i e day ime maximum empe a u e
end o 0.64Kdecade−1happened in Ap il in sou he n Fin-
land, whe e a o al o 2.7millionha o pea lands we e d ained
(Hökkä e al., 2002). The nigh - ime minimum empe a u e
end h ough he same pe iod was 0.37Kdecade−1. Lohila
e al. (2010) a ibu ed he subs an ially la ge inc ease in he
day ime maximum empe a u e han in he nigh - ime mini-
mum empe a u e o he change in su ace adia i e p ope -
ies a e d ainage.
Howe e , hese s udies abou he e ec s o pea land
o es a ion on clima e a e based on si e-le el da a o
obse a ion-based egional da a, which can no a ibu e he
clima e impac s o di e en in luencing ac o s. Speci ically,
hey can no dis inguish he local biogeophysical e ec s om
he global clima e change due o he inc ease in GHG con-
cen a ions. The clima e e ec s o pea land o es a ion ha e
no been quan i ied on a egional scale/coun y le el o in-
es iga e he biogeophysical e ec s in pa icula . Also, he
magni ude and pa e n o land-use change e ec s on clima e
depend on egional condi ions such as soil p ope y, opog-
aphy, e c. In o ma ion om egional s udies is essen ial o
he de elopmen o u u e s a egies o clima e mi iga ion o
o es managemen . Thus, i is necessa y o in es iga e he
e ec s egionally and sys ema ically.
In ecen yea s, egional clima e models ha e become sui -
able o simula ing egional clima e in a ine esolu ion o
esol e small-scale a mosphe ic ci cula ion (Déqué e al.,
2005; Jacob e al., 2001, 2007; McG ego , 1997). Fo his,
a egional clima e model wi h a ealis ic land scheme o in-
e p e mo e de ailed land su ace in o ma ion needs o be
applied.
In his s udy, he long- e m clima e e ec s caused by pea -
land o es a ion a e assessed om wo se s o 15-yea simu-
la ion esul s wi h he egional clima e model REMO, by us-
ing he his o ical (1920s) and p esen -day (2000s) land co e
condi ions. The in en ion o his s udy is o unde s and how
pea land o es a ion in Finland in luences egional clima e
condi ions h ough biogeophysical p ocesses.
2 Model desc ip ion and me hodology
2.1 REMO clima e model
The egional clima e model REMO is a h ee-dimensional
hyd os a ic a mosphe ic ci cula ion model de eloped a he
Max Planck Ins i u e o Me eo ology in Ge many (Jacob
e al., 2001, 2007; Jacob and Podzun, 1997). I s dynamical
co e is based on he “Eu opa-Modell”, he o me nume i-
cal wea he p edic ion model o he Ge man Wea he Se -
ice (Majewski, 1991). The land su ace scheme (LSS) o
REMO mainly ollows ha o he global a mosphe e ci cu-
la ion model ECHAM4 (Roeckne e al., 1996) wi h se -
e al physical package upda es (de ails a e shown below).
The p ognos ic a iables a e p essu e, empe a u e, ho izon-
al wind componen s, speci ic humidi y, cloud liquid wa e
and ice. REMO is d i en by la ge-scale o cing da a acco d-
ing o he elaxa ion scheme (Da ies, 1976). The eigh ou e -
mos g id boxes a each la e al bounda y a e he sponge zone.
Because land co e is cen al o his s udy, a b ie in oduc-
ion o he LSS in REMO is gi en below. In REMO LSS, he
o al a ea o each model g id box is composed o ac ions
o land ( ege a ion co e and ba e soil), wa e (ocean su -
ace and inland lake) and sea ice (Semmle e al., 2004). The
biogeophysical cha ac e is ics o majo land co e classes
(Olson, 1994a, b) a e desc ibed by he ollowing su ace
Biogeosciences, 11, 7251–7267, 2014 www.biogeosciences.ne /11/7251/2014/
Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland 7253
pa ame e s: backg ound su ace albedo (albedo o e snow-
ee land a eas), oughness leng h, ac ional g een ege a-
ion co e , lea a ea index (LAI; one-sided g een lea a ea
pe uni g ound a ea), o es a io ( ; ac ional co e age o
ees ega dless o hei pho osyn he ic ac i i y), soil wa e -
holding capaci y (maximum amoun o wa e ha plan s may
ex ac om he soil be o e wil ing begins) and olume ic
wil ing poin (pe cen age o mois u e in a soil column be-
low which plan s s a o wil ) (Hagemann, 2002; Hagemann
e al., 1999). The land su ace pa ame e s a e a e aged lin-
ea ly acco ding o ac ional co e age o land co e ypes
wi hin a model g id box, excep o he oughness leng h ha
isa e agedloga i hmically (Claussene al., 1994; Hagemann
e al., 1999). As LAI, ac ional g een ege a ion co e and
backg ound su ace albedo s ongly depend on he ege a-
ion phenology, hey a e p esc ibed wi h in a-annual cycles
by using a mon hly a ying g ow h ac o ha de e mines he
seasonal g ow h cha ac e is ics o he ege a ion (Hagemann,
2002; Rechid and Jacob, 2006). The g ow h ac o o la i-
udes highe han 40◦no h o sou h is de i ed om a 2m
empe a u e clima ology (Lega es and Willmo , 1990); in
o he la i udes, he ac ion o pho osyn he ically ac i e a-
dia ion is used.
The simple bucke scheme (Manabe, 1969) is used o
soil hyd ology whe e he pa i ioning o su ace uno and
in il a ion ollows he A no scheme (Dümenil and Todini,
1992). The soil empe a u e p o ile om he g ound su ace
o a ound 10m deep is desc ibed by i e soil laye s wi h in-
c easing hickness. The hea conduc i i y and hea capaci y,
equi ed in he hea conduc ion equa ion o calcula ing he
soil empe a u e, depend on he soil ypes (Ko la ski, 2007).
The dis ibu ion o soil ypes is om he FAO/UNESCO soil
map o he wo ld (FAO/UNESCO, 1971–1981; Ko la ski,
2007).
The A no scheme used o he soil hyd ology was u -
he imp o ed by conside ing he high esolu ion subg id-
scale he e ogenei y o he ield capaci ies wi hin a clima e
model g id box (Hagemann and Ga es, 2003). The esolu ion
o subg id-scale he e ogenei y is se o be 10 imes highe
han he model esolu ion when using he de aul REMO
land co e map-Global Land Co e Cha ac e is ics Da abase
(GLCCD) (Lo eland e al., 2000; US Geological Su ey,
2001). The h ee pa ame e s in he imp o ed A no scheme
accoun o he shape o he subg id dis ibu ion o soil wa e
capaci ies (Be a), subg id minimum (Wmin)and maximum
(Wmax)soil wa e capaci ies. Also, he o iginal annual back-
g ound albedo cycle was modi ied by using MODIS sa elli e
da a be ween 2001 and 2004 in o de o de i e mo e eal-
is ic global dis ibu ions o pu e soil albedo and pu e eg-
e a ion albedo, which a e hen used o compu e he annual
backg ound albedo cycle wi h mon hly a ying LAI (Rechid,
2008; Rechid e al., 2009).
Figu e 1. O og aphy o he model domain and he i e selec ed sub-
egions (sub egion1 – blue; sub egion2 – ed; sub egion3 – pu ple;
sub egion4 – g een; sub egion5 – o ange). The inne black ame
shows he ex en o he elaxa ion zone om he ou e bounda y,
i.e. he eigh ou e -mos g id boxes in each di ec ion o he model
domain.
2.2 The model domain and land co e da a se s
Ou model domain co e s Fennoscandia, a pa o Russia
and he no he n pa o cen al Eu ope, and i is cen ed on
Finland (Fig. 1). Typical ea u es in luencing he clima e o
his domain include he No h A lan ic Ocean and he Bal ic
Sea ha su ound he Fennoscandian coun ies, many inland
lakes loca ed in Sweden and Finland and he ela i ely high
Scandina ian moun ain ange; he es o he a ea has a o-
pog aphy lowe han 300m abo e sea le el.
The de aul land co e map in REMO is he GLCCD.
Howe e , i s desc ip ion o he land co e in Finland is un-
ealis ic. Fo ins ance, he e is no pea land in Finland in he
GLCCD, whe eas 7.4% (22377km2) o he land is co e ed
by na u ally eeless o spa sely eed pea lands acco ding o
he 10 h Finnish na ional o es in en o y (FNFI10) (Ko ho-
nen e al., 2013). The GLCCD was he e o e subs i u ed by
he mo e ealis ic and up- o-da e CORINE land co e map
(CLC; 2006) o he same model domain in Gao e al. (2014),
excep o he Russian pa whe e he CLC (2006) is no
a ailable. Un o una ely, land co e maps desc ibing he land
co e condi ions o Finland be o e he mos in ensi e pe iod
www.biogeosciences.ne /11/7251/2014/ Biogeosciences, 11, 7251–7267, 2014
7254 Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland
Figu e 2. Changes o ac ional co e age o he 10 land co e classes in Finland om he 1920s o he 2000s (FNFI10–FNFI1).
o pea land d ainage in he 1960s a e qui e limi ed. Ne e he-
less, he da a collec ed in he 1s Finnish na ional o es in-
en o y (FNFI1) p o ide he possibili y o acing back he
land co e condi ion o Finland in he 1920s (Il essalo, 1927;
Tomppo e al., 2010). Also, he FNFI10, a he han he CLC
(2006),is adop ed odesc ibe he landco e condi ion o Fin-
land in he 2000s, wi h he aim o a oid he unce ain ies in
compa ing land co e maps wi h di e en land co e classi-
ica ion me hods and di e en spa ial esolu ions. The FNFI1
and FNFI10 land co e maps a e pos -p oduc s ha we e spe-
cially p epa ed o his s udy om he espec i e FNFI ield
measu emen da a. The de ailed desc ip iono he p ocedu es
o de i ing he FNFI1 and FNFI10 land co e maps is shown
in Appendix A. The wo FNFI land co e maps a e in 3km
esolu ion and include 10 land co e classes ollowing CLC
nomencla u e.
The ac ional co e age o he 10 land co e classes
o e he land a ea o Finland in he 1920s and he changes
om he 1920s o he 2000s based on he wo FNFI land
co e maps a e as ollows ( ac ional co e age in he 1920s;
changes om he 1920s o he 2000s): coni e ous o -
es (33.0%; 5.2%); mixed o es (13.5%; −5.7%); b oad-
lea ed o es (4.7%; −0.8%); a i icial a eas (0.7%; 4.1%);
na u al g asslands (3.4%; −3.4%); pea bogs (14.3%;
−5.2%); open spaces (1.5%; −0.1%); ansi ional wood-
land/sh ub (18.9%; 4.3%); moo s and hea hland (2.1%;
0.7%); and ag icul u al a eas (8.0%; 0.9%). Regional di -
e ences o hose land co e classes can be seen in Fig. 2.
In he FNFI maps, he land co e class ”pea bogs” is de-
ined as na u ally eeless pea land and pine mi es whe e he
s ocking le el is low o he mean heigh o ees is below 5m
a ma u i y. The e o e, he shi ing om pea bogs o o es s
ep esen s a majo land co e change due o pea land o es a-
ion.
In addi ion o egional inspec ions, i e sub egions we e
selec ed o ep esen di e en land co e change condi ions
be ween FNFI1 and FNFI10 (Fig. 1), and he changes o ac-
ional co e age o he 10 land co e classes in hose i e
sub egions a e gi en in Table 1. This was done o speci i-
cally assess he local clima e e ec s o di e en in ensi ies
o pea land o es a ion. F om sub egion1 o sub egion4 he e
is a dec ease in he educ ion o pea bogs. Sub egion1 and
sub egion2 a e wo pea land o es a ion a eas loca ed in he
middle and sou h o Finland espec i ely. In sub egion1 and
sub egion2 he e we e dec eases in he ac ional co e age o
pea bogs o mo e han 20%, and he dec eases we e mainly
compensa ed by coni e ous o es . The dec ease in he ac-
ional co e age o pea bogs was 2% less in sub egion2 han
ha in sub egion1, bu he inc ease in he ac ional co e age
o coni e ous o es was 5% highe in sub egion2 han ha
in sub egion1. The o al inc ease in he ac ional co e age
o o es ypes was abou 16% in bo h sub egion1 and sub e-
gion2. Sub egion3 is loca ed in he eas o sub egion1. The e
was a 12% dec ease in he ac ional co e age o pea bogs,
bu ins ead o an inc ease o o es s, he ac ional co e -
age o ansi ional woodland/sh ub inc eased by 14.3%. Sub-
Biogeosciences, 11, 7251–7267, 2014 www.biogeosciences.ne /11/7251/2014/
Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland 7255
Table 1. Changes o ac ional co e age (%) o he 10 land co e classes om he 1920s o he 2000s (FNFI10–FNFI1) in he i e sub egions.
Class Legend Sub egion1 Sub egion2 Sub egion3 Sub egion4 Sub egion5
1 coni e ous o es 13.40 18.03 −2.24 −11.74 −10.13
2 mixed o es 1.23 −3.46 −2.30 −1.86 −2.10
3 b oad-lea ed o es 1.24 0.98 1.68 −0.52 −4.11
4 a i icial a eas 4.44 4.95 2.44 5.69 2.52
5 na u al g asslands −4.41 −2.10 −1.71 −2.82 −1.60
6 pea bogs −22.92 −20.82 −12.60 −3.80 8.64
7 open spaces 0.06 −0.12 −0.11 −0.31 −1.14
8 ansi ional woodland/sh ub 3.64 −0.72 14.26 4.84 9.12
9 moo s and hea hland 0.00 0.00 0.00 0.00 −1.37
10 ag icul u al a eas 3.31 3.26 0.57 10.52 0.17
egion4 is an a ea whe e he mos in ensi e an h opogenic
ac i i ies ha e occu ed in he i e sub egions. The e was
a 14% dec ease in he ac ional co e age o o es ypes and
a 3.8% dec ease in ha o pea bogs, wi h a 5.7% inc ease
in he ac ional co e age o a i icial a eas and a 10.5% in-
c ease in ha o ag icul u e a eas. Sub egion5 is an a ea wi h
an 8.64% inc ease in he ac ional co e age o pea bogs
and a 16.3% dec ease in he ac ional co e age o o es
ypes. He ein one should no ice ha some unce ain ies may
a ise om sampling in he FNFI1 and FNFI10 da a. This ap-
plies especially o FNFI1, whe e he dis ance be ween in en-
o y lines was as high as 26km. The e o e, sub egions ha
a e smalle han 100km×100km may no be su icien o
ep esen he ac ual land co e changes spa ially. Howe e ,
he dynamics o he local e ec s o land co e changes on
clima e can no be de ec ed when a e aging clima e signals
o e la ge a eas wi h di e se land co e changes. The e o e
small sub egions, which co e a ange o land co e change
in ensi ies, a e chosen o e lec local clima e impac s due o
di e en land co e changes.
Mo eo e , he FNFI da a only co e he land su ace
in Finland wi hou conside ing inland lakes. The e o e, he
land–sea mask in he model domain is adop ed om he CLC
(2006). In addi ion, he land co e condi ions o he a ea
ou side Finland in he model domain a e he same as hose
in Gao e al. (2014), i.e. based on he CLC (2006) and he
GLCCD, and hus iden ical in bo h simula ions.
In o de o make he land su ace pa ame e s mo e sui -
able o his s udy, se e al modi ica ions in REMO LSS we e
done. De ails o hose modi ica ions a e documen ed in Ap-
pendix B.
3 Expe imen design
Two simula ions we e conduc ed wi h he FNFI1 and
FNFI10 land co e maps, ep esen ing he land co e con-
di ions be o e and a e pea land o es a ion ac i i ies in Fin-
land espec i ely. The simula ions we e d i en wi h 6-hou ly
la e al bounda y condi ions om ECWMF ERA-In e im e-
analysis da a (Simmons e al., 2007) om 1 Janua y 1979
o 31 Decembe 1996. The 18-yea o wa d uns we e p e-
ceded by 10-yea (1 Augus 1979–1 Janua y 1990) sim-
ula ions in o de o s abilise he deep soil empe a u es
and soil mois u es. The las 15 yea s (1 Decembe 1981–
30 No embe 1996) ou o he 18-yea o wa d simula ions
we e adop ed o u he analysis. The analysed pe iod s a s
om 1 Decembe in o de o keep all 3 win e mon hs con-
inuous. The simula ed i s 1.5 yea s we e excluded in o de
o minimise he in luences o he ini ial bounda y condi ions
on simula ed clima e condi ions, which ha e a much quicke
adap a ion speed han deep soil empe a u e. The model g id
is in an 18km esolu ion ho izon ally and ex ends o e 27
e ical le els (up o 25km). The model ime s ep was se o
90s and he ime s eps o ou pu a iables a e 6-hou ly o 3-
D a iables and hou ly o 2-D a iables. Daily da a co e ing
24h a e p ocessed om 18:00UTC on he p e ious day o
17:00UTC on he cu en day. Fo 6-hou ly da a, 18:00UTC
on he p e ious day and 00:00UTC, 06:00 and 12:00UTC
on he cu en day we e used o daily alues. Fo his s udy
domain, he g owing season and he do mancy season co e
he pe iod om May o Oc obe and om No embe o Ap il
espec i ely.
4 Resul s
The land co e change e ec s on egional clima e condi ions
in Finland a e analysed based on he di e ences in clima e
a iables be ween he pos -d ainage and p e-d ainage sim-
ula ions (FNFI10–FNFI1). This “del a change app oach” is
adop ed o elimina e he unce ain ies ela ed o model bias
(Gálos e al., 2011; Jacob e al., 2008).
4.1 E ec s on clima e o e Finland
The di e ences in mon hly-a e aged daily mean 2m ai em-
pe a u e (T2m) a e qui e he e ogeneous empo ally and spa-
ially. T2m di e ences a e mos p ominen in sp ing ime and
summe ime (Fig. 3). The mos no iceable di e ence in T2m,
up o 0.43K, akes place in he mos in ensi e pea land
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7256 Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland
Figu e 3. The 15-yea a e aged di e ences (FNFI10–FNFI1) in
mon hly-a e aged daily mean 2m ai empe a u e in sp ing and
summe mon hs.
o es a ion a ea in he middle wes o Finland in Ap il. The
wa ming is also e iden in Feb ua y and Ma ch, wi h di -
e ences o 0.2K in his a ea. Howe e , T2m u ns o show
a sligh cooling, gene ally less han 0.1K, in a ew pa s o
his a ea om May o Oc obe . The e a e also wo egions
in no he n Finland ha show opposi e changes compa ed
o he pea land o es a ion a ea in he middle wes o Fin-
land wi h cooling in he sp ing and wa ming in he g ow-
ing season. This is because o dec eased o es co e and in-
c eased ac ion o pea bogs in hose wo a eas om FNFI1-
o FNFI10-based land co e maps. An inc ease o less han
0.2K is seen in T2m in he sou heas o Finland in July and
Augus as well as in he e y sou h o Finland h oughou
he g owing season, which is mainly due o he change om
mixed o es o coni e ous o es and he inc eased a i icial
a eas espec i ely. The 15-yea a e aged mon hly p ecipi a-
ion shows only small di e ences, less han 10mmmon h−1,
in a ied pa e ns in he model domain om Ap il o Augus
(no shown).
The snow clea ance day is also an impo an indica o
o sp ing ime clima e change a high la i udes (Peng e al.,
2013). The e o e, he snow clea ance day o each g id box
in Finland is de e mined o he 15yea s. The snow clea ance
day is de ined he e as he i s day a e which he o al num-
be o snow-co e ed days does no exceed he o al numbe
Figu e 4. The 15-yea a e aged di e ences (FNFI10–FNFI1) in he
snow clea ance days o e model g id boxes in Finland.
o snow- ee days, and he selec ion o his day ends be o e
midsumme in a yea . The di e ences be ween he 15-yea
a e aged snow clea ance days o he wo simula ions (Fig. 4)
show almos he same pa e n as he di e ences in T2m in
Ap il (Fig. 3). In he pea land o es a ion a ea in he mid-
dle wes o Finland, he snow clea ance days a e mos ly ad-
anced by 0.5 o 3 days and, in a ew g id boxes, ad anced by
up o 5 days in he 15-yea mean. The wo small a eas in he
no h o Finland wi h e e se land co e changes in compa -
ison o pea land o es a ion show up o 2-day delays in gen-
e al. In he e y sou h o Finland, he snow clea ance days
a e also gene ally ad anced in acco dance wi h he wa m-
ing seen in T2m, bu delayed in se e al sca e ed g id boxes
due o inc eased ac ion o a i icial a eas a he expense o
o es s.
4.2 E ec s on clima e o e i e sub egions
T2m, p ecipi a ion and se e al closely ela ed clima e a i-
ables (su ace albedo, ne su ace sola adia ion, snow dep h,
ET) o he i e sub egions we e p ocessed in o 11-day un-
ning means o educe he in luence o day- o-day a ia ions.
The di e ences be ween he simula ions in each o he e-
gionally a e aged clima e a iables we e u he a e aged
o e he 15yea s (Fig. 5). The da e in o ma ion he ein (day
o yea , DOY) ep esen s he middle con ibu ing day o he
11-day a e aging pe iod.
T2m o sub egion1 shows a wa ming o 0.1 o 0.2K om
Feb ua y un il he end o Ma ch and an e iden peak o
inc ease om ea ly Ap il o ea ly May ( om DOY 95 o
DOY 125) ha eaches a maximum o 0.5K in la e Ap il.
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Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland 7257
Discussion Pape | Discussion Pape | Discussion Pape | Discussion Pape |
0 60 120 180 240 300 360
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
(e)
DOY
ET (mm)
0 60 120 180 240 300 360
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
(a)
DOY
T2m (K)
0 60 120 180 240 300 360
-0.02
-0.02
-0.01
-0.01
0
0.01
0.01
0.02
(b)
DOY
snow dep h (m)
Sub egion1 Sub egion2 Sub egion3 Sub egion4 Sub egion5
0 60 120 180 240 300 360
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
(c)
DOY
albedo
0 60 120 180 240 300 360
-6
-4
-2
0
2
4
6
8
(d)
DOY
ne su ace sola adia ion(W/m2)
0 60 120 180 240 300 360
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
( )
DOY
p ecipi a ion (mm)
Figu e 5. The 15- yea a e aged egional mean di e ences (FNFI10 – FNFI1) in 11 day unning
mean o daily mean (a) wo-me e ai empe a u e, (b) snow dep h (p esen ed as equi alen wa e ),
(c) su ace albedo, (d) ne su ace sola adia ion, (e) ET and ( ) p ecipi a ion o he i e sub egions.
42
Figu e 5. The 15-yea a e aged egional mean di e ences (FNFI10
– FNFI1) in 11-day unning mean o daily mean (a) 2m ai empe -
a u e, (b) snow dep h (p esen ed as equi alen wa e ), (c) su ace
albedo, (d) ne su ace sola adia ion, (e) ET and ( ) p ecipi a ion
o he i e sub egions.
T2m o sub egion2 has he same de elopmen as sub egion1
h oughou he whole yea , bu he wa ming is much smalle
and he bigges di e ence, only 0.12K, occu s in he begin-
ning o Ap il. This is consis en wi h he di e ences in snow
dep h. The snow-co e pe iod in sub egion2 is sho e along
wi h an ea lie maximum di e ence in snow dep h. Mo e-
o e , hose cha ac e is ics o he di e ences in snow dep hs
a e in quali a i e ag eemen wi h he di e ences in su ace
albedo because snow is he key ac o ha con ols he su -
ace albedo in he snow-co e pe iod. F om he beginning o
May o he beginning o Oc obe , T2m shows a cooling o less
han 0.1K in sub egion1 and sub egion2 because he cooling
caused by ET exceeds he wa ming caused by he sligh ly
lowe albedo. The a iabili y o he di e ences in ne su ace
sola adia ion in he g owing season is induced by he a i-
abili y o cloud co e a he han su ace albedo. In No em-
be , Decembe and Janua y, he di e ences in T2m a y in
bo h di ec ions. A high la i udes, incoming sola adia ion is
qui e small and cloud co e ac ion is high in la e au umn
and win e . The e o e, he di e ences in su ace albedo a e
no able o induce di e ences in ne su ace sola adia ion
in his pe iod. Ins ead, he su ace ai empe a u e is sensi-
i e o changes in he long-wa e adia ion balance ha may
lead o a mosphe ic ai empe a u e in e sion unde a clea
sky, mani es ing i sel as ex eme cold su ace ai empe a-
u e. Thus, he a iabili y o he di e ences in cloud co e
caused by sho - e m a ia ions in he clima e con ibu es o
he a ied di e ences in T2m in his pe iod.
The di e ences in T2m o sub egion3 show a wa ming o
less han 0.1K om DOY 91 o DOY 120 bu also a wa ming
in an e en smalle magni ude h oughou he g owing season.
The di e ence in su ace albedo in sub egion3 is close o 0,
al hough he di e ence in snow dep h is simila o ha o
sub egion2 bu wi h a ime lag o a ound 15 days in he mos
in ensi e poin . In sub egion4, he snow dep h shows a qui e
small inc ease om he beginning o Janua y un il he end
o Ma ch, which is consis en wi h he inc ease in su ace
albedo and explains he sligh dec ease o up o 0.1K in T2m
om he middle o Feb ua y un il he end o Ma ch. Sub e-
gion5 displays he opposi e cha ac e is ics compa ed o sub-
egion1 and sub egion2 o all he in es iga ed a iables. The
absolu e di e ences in snow dep h o sub egion5 a e smalle
han hose o sub egion1 bu la ge han hose o sub egion2.
Because sub egion5 is loca ed in he no h o Finland, he
bigges di e ence in snow dep h occu s la e han ha o sub-
egion1. The magni ude o he maximum di e ences in T2m
in he snow-co e pe iod o sub egion5 also lies be ween ha
o sub egion1 and sub egion2 and happens la e han ha o
sub egion1.
The di e ences in T2m in he g owing season depend on
he su plus o ene gy balance e ms whe e ET mani es s i -
sel as la en hea lux. In gene al, he inc ease o ET in sub-
egion2 is sligh ly highe han ha in sub egion1. As a con-
sequence, he dec ease o T2m in sub egion2 is sligh ly la ge
han ha in sub egion1 du ing he g owing season when he
albedo di e ence is qui e small. The dec eased ET and he
sligh ly dec eased su ace albedo oge he esul in a sligh
wa ming du ing he g owing season in he o he sub egions.
The ex en s o wa ming in he o he sub egions ollow he
magni udes o he dec eased ET because he di e ences in
su ace albedo a e almos he same in he g owing season.
P ecipi a ion has highe a iabili y han ET h oughou he
yea in he i e sub egions. In gene al, he di e ences in p e-
cipi a ion a e much la ge in he g owing season han in he
do mancy season, when hey a e close o 0mmday−1. In he
g owing season, he inc ease in p ecipi a ion o sub egion1
occu s du ing a longe pe iod and has a la ge magni ude han
ha o sub egion2. The e a e sligh inc eases in he p ecipi a-
ion in sub egion3 and sub egion4, whe eas he p ecipi a ion
o sub egion5 shows a dec easing endency in he g owing
season, wi h he bigges di e ences less han 0.2mmday−1.
Fu he mo e, he maximum and minimum di e ences o
g id poin wise and egionally a e aged 11-day unning mean
o T2m o e 15yea s o sub egion1 we e in es iga ed as
complemen s o he egionally a e aged 15-yea mean di -
e ences (Fig. 6). T2m shows a maximum di e ence in g id
poin wise o nea ly 2K in he snow-mel ing pe iod o e he
15yea s, which is 1K highe han he maximum di e ence
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7258 Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland
Discussion Pape | Discussion Pape | Discussion Pape | Discussion Pape |
0 60 120 180 240 300 360
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
DOY
T2m (K)
Mean Min_G id Max_ G id Max_Sub egion Min _Sub egion
∇
Figu e 6. Maximum, minimum and mean di e ences o g idpoin -wise and egionally a e aged
11 day unning mean o daily mean wo-me e ai empe a u e o e 15 yea s in sub egion1.
43
Figu e 6. Maximum, minimum and mean di e ences o g id poin -
wise and egionally a e aged 11-day unning mean o daily mean
2m ai empe a u e o e 15yea s in sub egion1.
in egionally a e aged T2m o e he 15yea s and 4 imes ha
o he 15-yea mean o egionally a e aged T2m. The imings
o he h ee kinds o maximum di e ences in sp ing de ia e
om each o he by 3 o 10 days. The minimum di e ences
show only a small de ia ion be ween he g id poin wise and
egional mean alues o e he 15yea s. Du ing he snow-
mel ing pe iod, he minimum di e ences o egionally a e -
aged T2m is abo e 0, bu no ha o he g id poin wise T2m.
The sp ing ime di e ences be ween egional mean and g id
poin wise ex emes elucida e ha , e en wi hin one sub egion
wi h homogenous cha ac e is ics ela ed o pea land o es a-
ion, he sp ing wa ming o T2m is empo ally and spa ially
he e ogeneous. This implies ha local e ec s a e mo e p o-
nounced han he egional and empo al s a is ics can e eal.
Fo he es o he yea , he di e ences be ween he maxi-
mum (minimum) o he g id poin wise and egionally a e -
aged T2m a e small and o a mo e egional na u e. In he pe-
iod be ween No embe and Janua y, he la ge a ia ions o
maximum (minimum) T2m a e con ibu ed by he in e sion
e ec s due o sho - e m a ia ions in he clima e.
Addi ionally, o a mo e ho ough unde s anding o he e-
la ionships be ween sp ing wa ming and albedo changes in
he snow-co e pe iod due o pea land o es a ion, wo co -
ela ion ela ionships we e in es iga ed o e he 15yea s o
sub egion1 (Fig. 7). One is be ween he maximum empe a-
u e di e ence day (DOY) and he maximum su ace albedo
di e ence day (DOY). The o he is be ween he in lec ion
day o o al albedo ( he day when su ace albedo jus in-
ishes a as dec ease om i s win e ime le el; DOY) and he
snow clea ance day (DOY). The maximum empe a u e di -
e ence days ma ch o maximum albedo di e ence days in
6yea s, and he es o he yea s gene ally show a delayed
maximum empe a u e di e ence day compa ed o he max-
imum albedo di e ence day, wi h a maximum de ia ion o
14 days. In gene al, he snow clea ance day co ela es well
Discussion Pape | Discussion Pape | Discussion Pape | Discussion Pape |
100 110 120 130 140 150
100
110
120
130
140
150
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
(b)
In lec ion poin o o al albedo (DOY)
Selec ed snow clea ance day (DOY)
70 80 90 100 110 120 130
70
80
90
100
110
120
130
1982
1983
1984
1985
1986
1987
1988
1989
1990 1991
1992
1993
1994
19951996
(a)
Maximum empe a u e change (DOY)
Maximum o al albedo change (DOY)
Figu e 7. (a) Co ela ion be ween maximum empe a u e change day (DOY) and maximum o al
albedo change day (DOY); (b) co ela ion be ween in lec ion day o o al albedo ( he day when
su ace albedo jus inishes a as dec ease om i s win e ime le el; DOY) and he snow clea ance
day (DOY). The plo s show egional means o e sub egion1 o all 15 yea s.
44
Figu e 7. (a) Co ela ion be ween maximum empe a u e change
day (DOY) and maximum o al albedo change day (DOY); (b) co -
ela ion be ween in lec ion day o o al albedo ( he day when su ace
albedo jus inishes a as dec ease om i s win e ime le el; DOY)
and he snow clea ance day (DOY). The plo s show egional means
o e sub egion1 o all 15yea s.
wi h he in lec ion poin o su ace albedo. Fo mos yea s,
he di e ences a e less han 6 days, bu 3 yea s show di e -
ences up o a ound 20 days. In hose yea s, spo adic snow all
wi h a small accumula ed snow dep h canno eally in oduce
di e ences in o al su ace albedo o e he sub egion bu in-
luences he de e mina ion o he snow clea ance day.
4.3 Rela ionships be ween he changes in
biogeophysical aspec s and he impac s on clima e
To assess he gene ali y o he causal ela ionships be ween
land co e changes and clima e a iables, he spa ial co -
ela ions be ween changes in he wo su ace ene gy bal-
ance ele an a iables, su ace albedo and ET, and T2m
a e in es iga ed. Consequen ly, he spa ial co ela ions be-
ween changes in su ace albedo and ET and changes in
he su ace pa ame e alues a e also explo ed. The co e-
la ions wi h ac ional g een ege a ion co e is no shown
Biogeosciences, 11, 7251–7267, 2014 www.biogeosciences.ne /11/7251/2014/
Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland 7259
in Fig. 8 because LAI and g een ege a ion a io a e bo h
modula ed wi h he mon hly a ying g ow h ac o by he
same scheme, and hey a e highly co ela ed (Pea son co -
ela ion coe icien , 2=0.984 o Ma ch, 2=0.674 o
June). Mon hly means o 15-yea a e aged changes in Ma ch
and June a e selec ed o ep esen sp ing ime and summe -
ime espec i ely. The changes in T2m a e in acco dance wi h
he changes in su ace albedo in Ma ch (Fig. 8a), which is al-
mos linea ly co ela ed wi h he changes in LAI (Fig. 8c)
and o es a io (Fig. 8e). The changes in T2m a e linea ly
co ela ed wi h he changes in ET o e mos o he a ea in
June (Fig. 8b). In gene al, he changes in ET a e also co -
ela ed wi h he changes in LAI (Fig. 8d), oughness leng h
(Fig. 8 ) and o es a io (yea ly cons an , no shown), despi e
hein luences om d ough s ha may happen inla e summe .
O e all, he changes in su ace albedo and ET a e closely de-
penden on he changes in land su ace pa ame e s, which a e
induced by he changes in ac ional co e ages o land co e
ypes in he i e sub egions (Table 1). The changes in T2m a e
mainly modula ed by he changes in su ace albedo and ET in
sp ing and summe espec i ely. Some g id boxes loca ed in
he sou heas o Finland, whe e mixed o es was subs i u ed
by mainly coni e ous o es , show de ia ions in he co ela-
ions wi h LAI (ma ked by yellow ci cles in Fig. 8b, c, d). In
his a ea, LAI inc eased wi h almos no change in o es a io,
which led o a ela i ely smalle dec ease in su ace albedo
compa ed o o he a eas wi h he same magni ude o changes
in LAI in Ma ch; he ET-induced cooling is ou weighed by
he albedo-induced wa ming, which causes a sligh wa ming
in June. In he ollowing summe mon hs, July and Augus ,
he ET-induced cooling ypically ge s smalle because o su -
ace wa e limi a ion and consequen wa ming.
5 Discussion
5.1 Biogeophysical impac s o pea land o es a ion on
egional clima e
Su ace albedo shows a no able dec ease in pea land o es a-
ion a eas du ing he snow-co e pe iod and a sligh dec ease
in he g owing season, whe eas LAI, oughness leng h,
ac ional g een ege a ion co e and o es a io inc ease
h oughou he yea a e pea land o es a ion. Those changes
lead o an inc ease in sp ing ime T2m, which occu s locally in
acco dance wi h he dec ease in su ace albedo. In he g ow-
ing season, an inc ease in ET ela ed o he inc eased LAI
and ac ional g een ege a ion co e leads o mo e ene gy
consumed by la en hea lux han gained by sligh ly lowe
albedo. Addi ionally, highe oughness leng h can play a ole
by inc easing u bulen mixing and consequen ly he mag-
ni udes o u bulen luxes. Thus, he sca e ed di e ences
in p ecipi a ion in summe a e con ibu ed o mo e con ec-
i e s uc u es, while o he es o he yea he p ecipi a ion
is basically con olled by la ge-scale me eo ology. F om he
Figu e 8. Spa ial co ela ions be ween (a) changes in mon hly-
a e aged daily mean 2m ai empe a u e (T2m) and changes in
albedo o Ma ch, (b) changes in T2m and changes in ET o June
and ela ionships be ween changes in land su ace pa ame e s in
REMO LSS ollowing land co e changes and changes in albedo (c,
e) (changes in ET, d, ) in he co esponding mon h. The changes in
he g id boxes in selec ed sub egions a e shown wi h colou ed do s
(sub egion1 – blue; sub egion2 – ed; sub egion3 – pu ple; sub e-
gion4 – g een; sub egion5 – o ange). The g id boxes in yellow ci -
cles show he changes in he sou heas a ea o Finland.
analysis o he esul s in he i e sub egions, he di e ences
in he clima e a iables show ha hei magni udes depend
on he ex en o land co e changes, while he imings o he
ex emesmos ly depend ongeog aphical loca ions (la i udes)
ha de ine he adia ion balance h ough he seasonal cycle.
Resul s also illus a e a posi i e eedback induced by pea -
land o es a ion be ween lowe su ace albedo and wa me
T2m in he snow-mel ing pe iod. The wa ming caused by
lowe su ace albedo in he snow-co e pe iod due o mo e
o es leads o a quicke and ea lie snow mel ing; mean-
while, he su ace albedo is educed and consequen ly he
su ace ai empe a u e is inc eased. Addi ionally, he maxi-
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7266 Y. Gao e al.: Biogeophysical impac s o pea land o es a ion on egional clima e changes in Finland
o es s o Finland. Resul s o he gene al su ey o he o es s o
he coun y ca ied ou du ing he yea s 1921–1924), Commu-
nica iones ex Ins i u o Quaes ionum Fo es alium Finlandiae 11,
Val ioneu os on ki japaino, 1927.
Il essalo, Y.: Suomen me sä uosina 1921–24 uosiin 1951–53:
kolmeen al akunnan me sien in en oin iin pe us u a u kimus
( he o es s o Finland om 1921–24 o 1951–53. A su ey based
on h ee na ional o es in en o ies), Communica iones Ins i u i
Fo es alis Fenniae, Finnish Fo es Resea ch Ins i u e, Helsinki,
Finland, 47, 277 pp., 1956.
IPCC: Clima e Change 2013: The Physical Science Basis. Wo king
G oup 1 Con ibu ion o he Fi h Assessmen Repo o he In-
e go e nmen al Panel on Clima e Change, Camb idge, UK and
New Yo k, NY, USA, 1535 pp., 2013.
Jacob, D. and Podzun, R.: Sensi i i y s udies wi h he egional cli-
ma e model REMO, Me eo ol. A mos. Phys., 63, 119–129, 1997.
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