DOI 10.1007/s00704-013-0861-9 O R I G I N A L P A P E R
Variability of air mass occurrence in southern Poland (1951-2010)
Paweł Kotas • Robert Twardosz • Zenon Nieckarz
Received: 3 February 2012 /Accepted: 18 February 2013 /Published online: 12 March 2013
© The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract T h e p a p e r d is c u s s e s th e fre q u e n c y , p e rs is te n c e a n d s u c c e s sio n se q u e n c e o f six ty p e s o f a ir m a s s d u rin g th e p e rio d 1 9 5 1 -2 0 1 0 . T h e study, w h ic h re lie d o n a c a le n d a r o f a i r m a s s e s i n s o u t h e r n P o l a n d p u b l i s h e d b y T.
N ie d ź w ie d ź , c o n c lu d e s th a t th e re is n o sim p le re la tio n sh ip b e tw e e n th e p e rs iste n c e a n d th e fre q u e n c y o f sp ecific air m a s se s in th e re g io n . T h e stu d y fo u n d th a t th e re w a s a g re a t v a rie ty in th e p e rs iste n c e o f sp e c ific ty p e s o f a ir m a s s a n d th a t p e rs iste n c e d e p e n d e d m o re o n th e d ire c tio n o f a ir m a s s a d v e c tio n th a n o n th e ir fre q u e n c y o f o c c u rre n c e . T h e stu d y also fa ile d to id e n tify a n y stric t o v e ra ll ru le o f su c c e ssio n , as a n y a ir m a s s c o u ld fo llo w a fte r a n y o th er, b u t c e rta in fin er- g ra in e d p a tte rn s e m erg ed . In w in te r a n d su m m er, a rc tic air (A ) n e v e r fo llo w e d d ire c tly a fte r tro p ic a l a ir (T ) o r v ic e v ersa. A lso , th e m o s t fre q u e n t s u c c e s sio n s e q u e n c e id e n ti
fied w a s fro m P o la r m a ritim e fre sh a ir (m P f) to P o la r m a r
it im e o ld a n d i t a c c o u n t e d f o r t h e v a s t m a j o r i t y o f su c c e s sio n s fro m m P f in to a n y o th e r a ir m a s s (6 3 % a n n u ally a n d 7 6 % in su m m er).
1 Introduction
T h e ty p e s o f a ir m a s s p re s e n t o v e r a n a re a sig n ific a n tly in flu e n c e th e lo c a l w e a th e r. T h is in flu e n c e g o e s b e y o n d
P Kotas • R. Twardosz ( * )
Department of Climatology, Jagiellonian University, ul. Gronostajowa 7,
30-387 Kraków, Poland e-mail: r.twardosz@uj.edu.pl P. Kotas
e-mail: pawel.kotas@uj.edu.pl Z. Nieckarz
Experimental Computer Physics Department, Institute of Physics, Jagiellonian University, ul. Reymonta 4,
30-059 Kraków, Poland e-mail: zenon.nieckarz@uj.edu.pl
sp ecific v a lu e s o f w e a th e r ele m e n ts a n d also c o v e rs th e ir tim in g (N ie d ź w ie d ź 1 9 8 1 ; T w ard o sz 2 0 0 5 ; T w ard o sz e t al.
2 0 1 1 a , b ), e sp ecially in th e case o f d a n g e ro u s atm o sp h eric p h e n o m e n a (T w ardosz 2 0 1 0 ). T h e stu d y o f air m a s s v a ria b il
ity h a s th e po ten tial, th erefo re, to co n trib u te to b o th ap p lied m e te o ro lo g y a n d to a b e tte r u n d e rs ta n d in g o f th e c a u se s b e h in d c o n te m p o ra ry c lim a te v a ria tio n , e sp e c ia lly th e o b s e rv e d g ro w th in a ir te m p e ra tu re (K a lk s te in e t al. 1 9 9 8 ; T w ard o sz a n d K o s so w sk a -C e z a k 2 0 1 2 ). N e v e rth e le ss, c lim a to lo g ists ra re ly ta k e u p th is to p ic be c a u se , as w a s a p tly p o in te d o u t b y U strn u l (2 0 0 7 ), th ere is a sev ere sh o rtag e o f cale n d ars o f a ir m a s s types.
W h a t re s e a rc h is a v a ila b le is m a in ly a b o u t th e fre q u e n c y o f o c c u rre n c e o f a ir m a s se s. R e le v a n t stu d ie s p e rta in in g to th e te rrito ry o f P o la n d in c lu d e th o s e b y R a fa ło w sk i e t al.
( 19 5 5 ), B o ła s z e w s k a a n d R e u tt ( 1 9 6 2 ), W a ra k o m sk i ( 19 6 9 ), a n d W ię c ła w (2 0 0 4 ), w h ile w o rk s p u b lis h e d b y B u c h e rt (2 0 0 6 ) a n d N ie d ź w ie d ź (2 0 0 0 , 2 0 0 3 ) w e n t d o w n to th e scale o f a re g io n . A n o ta b le stu d y b y K a sz e w s k i ( 1 9 7 7 ) id en tifies a re la tio n sh ip b e tw e e n arc tic a n d tro p ic a l a ir a d v e c tio n , o n th e o n e h a n d , a n d s y n o p tic s itu a tio n s in c e n tr a l- e a s te r n P o la n d o n th e other. T h e s e a s o n a lity o f a ir m a s s fre q u e n c y w a s a ls o s tu d ie d in o th e r a re a s , e s p e c ia lly in th e U S A (S c h w a rtz 1 9 9 5 ; K a lk s te in e t al. 1 9 9 6 , 19 9 8 ). T h e se stu d ies also d e ta il m e th o d s fo r th e id e n tific a tio n o f a ir m a s s types.
P e rs iste n c e is a c h a ra c te ristic o f a ir m a s s v a ria b ility th a t is b o th im p o rta n t, e sp e c ia lly fo r fo re c a stin g (O su c h o w sk a - K le in 1 9 7 5 ), a n d ra re ly re se a rc h e d . S tu d ies in to th is c h a r
a c te ris tic w e re p u b lis h e d , a m o n g o th e rs, b y W a ra k o m sk i ( 1 9 6 9 ), W ię c ła w (2 0 0 4 ), a n d r e c e n tly b y K o ta s (2 0 1 1 ).
S tu d ies o n p e rs iste n c e are, h o w e v e r, a v a ila b le fo r c irc u la tio n ty p e s (e.g. K y s e ly a n d D o m o n k o s 2 0 0 6 )
In th is study, th e a u th o rs fo c u s e d o n th e s e a s o n a l a n d a n n u a l v a ria b ility o f six a ir m a s s ty p e s in so u th e rn P o la n d d u rin g th e 60 y e a rs sp a n n in g 1 9 5 1 -2 0 1 0 . T h re e c h a ra c te r
istics w e re ta k e n in to a c c o u n t: freq u en cy , p e rs iste n c e a n d s u c c e s sio n seq u en ce.
2 Data and methods
The study relies on a calendar o f air masses of southern P oland during the period 1951-2010 publish ed by Niedźwiedź (2011). Air masses identified by Niedźwiedź are based on a classification widely adopted in meteorolog
ical services (American Meteorological Society 2000) which involves source regions (known as a “geographical classification”) and therm al and m oisture properties (c—continental, m—maritime, w—warm) based on a clas
sification by Bergeron (1928). Niedźwiedź identified six air masses:
• Arctic—A
• Polar maritime (fresh)—mPf
• Polar maritime old (transformed)—mPo
• Polar maritime warm—mPw
• Polar continental—cP
• Tropical—T
Niedźwiedź classified days with more than one air mass as days with various air masses (vAm). His study area was defined as: 49-51°N and 18-24°E (Fig. 1).
Using his calendar, the authors identified the average frequency and persistence of air masses in separate seasons and in the whole year and their confidence intervals. Strings of days with a given air mass interrupted by a single day
with a different air mass were still counted as one. Strings that straddled across a seasonal divide were included in the season where a larger portion o f the days fell or, where these numbers were equal, the string was included in the earlier season. The study also investigated the variability of fre
quency and of persistence through the period.
For each air mass type, the study identified the numbers of strings of different persistence, their frequencies and the proportion of the total days in strings of a given length in the overall total number o f days with that air mass in the period.
The frequency of succession sequences was also identi
fied, i.e. the occurrence after a given air mass of another air mass. The research topic of succession deals with qualitative data, such as air masses. In this study, succession was approached in two ways: (1) by investigating the frequency of the total variability (all instances of succession from one air mass to another representing 100 %) and (2) by investi
gating the frequency o f succession from a given air mass to another given air mass (where the frequency o f all instances of succession from the former air mass represent 100 %).
3 Frequency
Air masses in southern Poland feature a whole range of thermal and humidity characteristics. During the 60-year
Fig. 1 Location o f study area
Table 1 Frequency (in percent) of air masses over southern Poland and its 95 % confidence interval (1951-2010)
Air masses Spring Summer Autumn Winter Year
Arctic-A 11.6± 1.8 3.1±1.0 8.6±1.4 8.9±1.6 8.0±0.8
Polar maritime (fresh)—mPf 13.6±1.6 25.6±2.2 16.6±1.8 14.0±1.6 17.5±1.2
Polar maritime old (transformed)—mPo 31.1 ±3.0 35.4±2.4 31.4±2.4 32.9±2.4 32.7±1.8
Polar maritime warm—mPw 6.6±1.2 3.7±1.0 10.2±1.6 9.3±1.6 7.4±0.8
Polar continental— cP 23.5±2.6 18.6±2.6 20.1±2.8 23.6±3.4 21.4±1.6
Tropical—T 3.7±1.0 4.3±1.2 3.3±1.0 1.0±0.6 3.1±0.6
Various air masses—vAm 10.0±2.0 9.3±1.8 9.8±1.8 10.5±2.0 9.8±1.8
stu d y p e rio d , th e m o s t fr e q u e n t a ir m a s s w a s th e P o la r m a ritim e o ld (tra n sfo rm e d ) a ir w h ic h a c c o u n te d fo r a p p ro x im a te ly o n e th ird o f a ll d a y s, in c lu d in g 35 % in s u m m e r a n d 3 1 % in sp rin g a n d a u tu m n (T able 1 ). T h is is c o m p a tib le w ith a n e a rlie r s tu d y b y B o ła s z e w s k a a n d R e u tt ( 1 9 6 2 ), w h o c o n c lu d e d th a t th is a ir m a s s ty p e w a s th e m o s t fre q u e n t a c ro ss P o la n d . P o la r c o n tin e n ta l a ir w a s th e se c o n d m o s t fre q u e n t a t 24 % in w in te r a n d sp rin g a n d 19 % in sum m er.
S u m m e r w a s a lso th e se a s o n w h e n m P f in c re a se d in fre q u e n c y to 26 % . O th e r a ir m a s se s w e re less fre q u e n t, e sp e c ia lly th e o n e s o rig in a tin g o u ts id e th e m o d e ra te la titu d e s, an d fo llo w se a s o n a l p a tte rn s. P o la r m a ritim e w a rm a ir is n e a rly 2 .5 tim e s m o re fre q u e n t in a u tu m n (1 0 % ) th a n in s u m m e r (4 % ); A rc tic a ir p e a k s in fr e q u e n c y in sp rin g (12 % ) a n d re a c h e s its lo w in s u m m e r (3 % ); tro p ic a l a ir is a t its m o s t f r e q u e n t in s u m m e r (4 % ) a n d a t th e le a s t fre q u e n t in w in te r (1 % ). F in ally , th e re are a b o u t 10 % o f d a y s w ith a ir m a s s c h a n g e in a ll seasons.
N o sta tistic a lly s ig n ific a n t se a s o n a l v a ria b ility w a s fo u n d in th e m o s t fre q u e n t a ir m a s se s, i.e. m P o a n d cP, as th e y are ty p ic a l o f th e c lim a te z o n e o f th e s tu d y a re a w ith its c o n s is te n t p re v a le n c e o f zo n a l circu latio n . T h e re m a in in g fo u r air m a s se s d is p la y c le a r se a so n a litie s. T h e re is also a g re a t d e a l o f y e a r-to -y e a r v a ria b ility o f th e sam e a ir m a sse s. F o r e x am p le, a rctic a ir m a y n o t o c c u r in th e sp rin g o f 1 y e a r b u t m a y p e rs is t fo r 30 % o f d a y s in th e sam e se a s o n o f th e fo llo w in g y e a r (T able 2 ).
4 Persistence
4.1 A v e ra g e p e rs iste n c e
I n s o u th e rn P o la n d a ir m a s s e s p e r s is t in s trin g s o f 2 .2 c o n se c u tiv e d a y s o n av e ra g e . T h e re is a g o o d d e a l o f d iffe r
en ce b e tw e e n e a c h ty p e , h o w e v e r, s u c h as 1.6 d a y s fo r m P w in s u m m e r a n d 4.3 d a y s fo r cP in w in te r (T able 3). T h e m o s t fre q u e n t a ir m a s s o f all, m P o , m a in ta in e d a c o n s is te n t a v e r
ag e p e rs iste n c e in a ll se a s o n s a t 2 .6 d ays. A m u c h sh o rter a v e ra g e p e rs iste n c e w a s c a lc u la te d fo r m P f a n d m P w a ir a t a p p ro x im a te ly 1 d a y each. In su m m er, th e tw o ty p e s d iffe re d sig n ific a n tly a t 2 .2 ± 0 .1 d a y fo r m P f a n d 1 .6 ± 0 .2 d a y for m P w . In th e re m a in in g se a so n s, a n y d iffe re n c e s b e tw e e n th e s e ty p e s w a s in s ig n ific a n t a t a = 0 .0 5 . T h e re la tiv e ly sh o rt p e rs iste n c e o f m P f a n d m P w a ir m a s s e s w a s a re s u lt o f th e ra p id m o v e m e n t o f d e p re s s io n s a c ro ss P o la n d a c c o m p a n ie d b y e x te n s iv e sy s te m s o f fro n ts a n d a su b s e q u e n t tra n s fo r
m a tio n o f th e s e m a s se s in to m P o . T h is ty p e o f tra n s fo rm a ti o n is th e q u ic k e s t in w in te r a n d in s p r in g , w h e n th e te m p e ra tu re d if fe re n tia l b e tw e e n th e A tla n tic O c e a n a n d la n d in E u ro p e is a t its g reatest. A t th a t tim e , its av e ra g e p e rs iste n c e sta n d s a t 1.7 d ay s. In su m m er, th is tra n s fo rm a tio n p ro c e s s is m u c h s lo w e r a n d th e p e rs is te n c e e x te n d s to 2 .2 d a y s o n av erag e.
A m o n g th e six ty p e s o f a ir m a s s, cP a ir sta n d s o u t w ith its lo n g e s t a v e ra g e p e rs is te n c e o v e r th e w h o le y e a r a n d n o
Table 2 Range o f frequency variability (a) minimum and (b) maximum (in percent) o f air masses in southern Poland (1951-2010) (number of extreme occurrences in brackets)
Air masses Spring Summer Autumn Winter Year
a b a b a b a b a b
A 0.0 (1) 30.4 (1) 0.0 (20) 14.1 (1) 0.0 (1) 24.2 (1) 0.0 (2) 22.0 (1) 2.5 (1) 17.0 (1)
mPf 3.3 (1) 32.6 (1) 8.7 (1) 55.4 (1) 4.4 (1) 33.0 (2) 1.1 (1) 26.7 (1) 10.7 (3) 29.0 (1)
mPo 13.0 (1) 70.7 (1) 20.7 (1) 63.0 (1) 13.2 (1) 53.8 (2) 14.4 (1) 51.1 (1) 19.7 (1) 53.7 (1)
mPw 0.0 (2) 20.7 (1) 0.0 (11) 16.3 (1) 1.1 (1) 30.8 (1) 0.0 (3) 26.7 (1) 0.8 (1) 14.8 (1)
cP 2.2 (1) 46.7 (1) 0.0 (1) 44.6 (1) 2.2 (2) 48.4 (1) 1.1 (1) 57.8 (1) 8.8 (1) 38.9 (1)
T 0.0 (20) 15.2 (2) 0.0 (17) 19.6 (1) 0.0 (17) 17.6 (1) 0.0 (42) 11.1 (1) 0.0 (2) 10.1 (1)
vAm 0.0 (6) 26.1 (1) 0.0 (6) 22.8 (1) 0.0 (8) 25.3 (3) 0.0 (6) 31.1 (1) 0.0 (3) 24.4 (1)
Air masses Spring Summer Autumn Winter Year Table 3 The average persis
tence of air masses (in days) and their 95 % confidence intervals
(1951-2010) A 2.50±0.22
m Pf 1.73±0.10
mPo 2.52±0.16
mPw 1.66±0.14
cP 3.83±0.36
T 2.00±0.30
vAm 1.29±0.06
Avg. 2.30±0.08
1.94±0.26 2.29±0.20
2.17±0.14 1.91±0.14
2.51±0.16 2.63±0.18
1.56±0.18 2.01±0.20
3.32±0.32 3.95±0.46
1.86±0.20 1.90±0.26
1.26±0.06 1.22±0.06
2.20±0.08 2.30±0.08
2.12±0.20 2.27±0.12
1.67±0.10 1.90±0.06
2.64±0.18 2.57±0.08
1.93±0.16 1.83±0.08
4.25±0.44 3.83±0.20
1.56±0.30 1.88±0.14
1.33±0.06 1.27±0.04
2.30±0.08 2.27±0.04
s ig n ific a n t s e a s o n a lity ( a = 0 .0 5 ). W a ra k o m sk i ( 19 6 9 ) a n d W ię c ła w (2 0 0 4 ) fo u n d cP to b e th e m o s t p e rs is te n t in th e w h o le o f P o la n d , w h ic h m u s t b e a ttrib u te d to th e v e ry g re a t sta b ility o f th e e a ste rn c irc u la tio n fro m w h e re th is ty p e o f air m a s s c o m e s (O su c h o w sk a -K le in 19 7 5 ).
T w o a ir m a s s e s th a t a rr iv e in s o u th e r n P o la n d fro m o u ts id e m o d e ra te la titu d e s, i.e. T a n d A , sta n d o u t w ith th e ir
lo n g e s t sp rin g tim e p e rs iste n c e a t 2 a n d 2.5 d ay s, re s p e c tiv e ly. It is th e ir e ffe c t th a t is b e h in d th e ty p ic a lly h ig h w e a th e r v a ria b ility in sp rin g tim e , w h ic h ra n g e s fro m fro sty sp e lls to h e a t w a v e s, as m e rid io n a l c irc u la tio n in c re a se s its sh are a t th e c o s t o f lo n g itu d in a l c irc u la tio n (N ie d ź w ie d ź e t al. 2 0 0 9 ).
A -ty p e a ir m a s se s a rriv e in P o la n d in c o n n e c tio n w ith h ig h p re s su re sy ste m s, w h ic h te n d to b e m o re stab le. F in ally , air
Table 4 Number of strings o f days with individual air masses (NS), frequency (in percent) o f strings (FS), and the proportion (in percent) o f each string length in the total number o f days with that air mass type (FD) (1951-2010)
Air Strings o f days
masses
1 2 3 4 5 6 7 8 9 10 11-15 16-20 21-30 2
A NS 301 233 118 63 32 15 10 4 2 1 2 - - 781
FS 38.5 29.8 15.1 8.1 4.1 1.9 1.3 0.5 0.3 0.1 0.3 - - 100
FD 17.0 26.3 19.9 14.2 9.0 5.1 3.9 1.8 1.0 0.6 1.2 - - 100
mPf NS 1,118 496 233 101 61 20 15 3 4 4 6 - - 2,061
FS 54.2 24.1 11.3 4.9 3.0 1.0 0.7 0.1 0.2 0.2 0.3 - - 100
FD 28.5 25.3 17.8 10.3 7.8 3.1 2.7 0.6 0.9 1.0 1.9 - - 100
mPo NS 1,230 605 360 232 131 104 63 40 18 11 34 8 - 2,836
FS 43.4 21.3 12.7 8.2 4.6 3.7 2.2 1.4 0.6 0.4 1.2 0.3 - 100
FD 16.9 16.6 14.8 12.7 9.0 8.6 6.0 4.4 2.2 1.5 5.5 1.8 - 100
mPw NS 510 217 101 33 19 16 4 2 2 2 1 - - 907
FS 56.2 23.9 11.1 3.6 2.1 1.8 0.4 0.2 0.2 0.2 0.1 - - 100
FD 30.7 26.1 18.2 7.9 5.7 5.8 1.7 1.0 1.1 1.2 0.7 - - 100
cP NS 301 271 195 103 113 58 31 45 31 24 38 15 5 1,230
FS 24.5 22.0 15.9 8.4 9.2 4.7 2.5 3.7 2.5 2.0 3.1 1.2 0.4 100
FD 6.4 11.5 12.4 8.7 12.0 7.4 4.6 7.6 5.9 5.1 10.1 5.6 2.6 100
T NS 188 95 46 24 5 2 2 - - 1 1 - - 364
FS 51.6 26.1 12.6 6.6 1.4 0.5 0.5 0.0 0.0 0.3 0.3 - - 100
FD 27.5 27.8 20.2 14.0 3.7 1.8 2.0 - - 1.5 1.6 - - 100
vAM NS 1,157 244 50 16 3 - - - 1,470
FS 78.7 16.6 3.4 1.1 0.2 - - - 100
FD 61.7 26.0 8.0 3.4 0.8 - - - 100
Total NS 4,805 2,161 1,103 572 364 215 125 94 57 43 82 23 5 9,649
FS 49.8 22.4 11.4 5.9 3.8 2.2 1.3 1.0 0.6 0.4 0.8 0.2 0.1 100.0
FD 21.9 19.7 15.1 10.4 8.3 5.9 4.0 3.4 2.3 2.0 4.5 1.8 0.6 100.0
The largest values given in italics
m a s s c h a n g e is fo u n d to b e la rg e ly lim ite d to sin g le d a y s a n d av e ra g e s 1.3 days.
G e n e ra lly , th e re is n o sim p le re la tio n sh ip b e tw e e n th e p e rs iste n c e o f in d iv id u a l ty p e s o f a ir m a s s a n d th e ir fre q u e n cy. It is th e d ire c tio n o f a d v e c tio n w h ic h p la y s a sig n ific a n t ro le h e re a n d e a ste rn c irc u la tio n te n d s to su p p ly a ir m a s se s th a t p e rs is t fo r a lo n g e r tim e. T h is is p a rtic u la rly tru e o f th e c P m a s s , th e m o s t f r e q u e n t a ir m a s s a rr iv in g w ith th is c irc u la tio n (N ie d ź w ie d ź 19 8 1 ). N o rth e r n c irc u la tio n fa v o u rs A -ty p e m a s se s a n d th e ir h ig h e s t fre q u e n c y is in sp rin g tim e.
4 .2 S trin g s o f d a y s w ith a ir m a s se s
T h e sim ila rity o f th e a v e ra g e se a s o n a l p e rs iste n c e b e tw e e n v a rio u s a ir m a s s ty p e s m e a n t th a t in th e se a rc h fo r d iffe r
e n ces th e s tu d y h a d to tu r n to a n n u a l p a tte rn s (T able 4 ).
S e a s o n a l v a lu e s w e re o n ly c o m p a re d in te rm s o f m a x im u m p e rs iste n c e s (T able 5 ).
T h e p e r s is te n c e s r a n g e d fro m s in g le d a y s to 3 0 -d a y strin g s (T ab le s 4 a n d 5 ). S in g le -d a y p e rs is te n c e s w e re a cle a r m a jo rity , e s p e c ia lly in th e “ v a r io u s a ir m a s s ” c a te g o ry (79 % ) a n d th e tro p ic a l a ir (5 2 % ). S in g le d a y s w e re th e m o s t fre q u e n t in a ll ty p e s o f a ir m a s s a n d re p re se n te d th e la rg e st p ro p o rtio n o f d a y s w ith a g iv e n a ir m a s s w ith th e
e x c e p tio n o f cP air. H e re to o , P o la r c o n tin e n ta l a ir o c c u rre d m o s t fre q u e n tly o n sin g le d a y s, b u t th e to ta l n u m b e rs o f d a y s w ith th a t a ir m a s s in o th e r strin g p e rs is te n c e s (2, 3, 5 a n d 1 1 -1 5 d a y strin g s) w e re g re a te r th a n th a t in sin g le d a y o c c u rre n c e s.
O v e ra ll, th e g re a te s t n u m b e r o f strin g s w ith a sin g le air m a s s ty p e ra n g e d fro m 1 to 3 d a y s lo n g , w h ic h w a s ty p ic a l o f th e ir v a ria b ility in b o th so u th e rn P o la n d a n d in th e w h o le c o u n try (W a ra k o m sk i 19 6 9 ). A t th e o th e r e n d o f th e sp e c tru m , th e re w e re lo n g sp e lls th a t so m e tim e s e v e n in v o lv e d a ir m a s se s o rig in a tin g fro m o u ts id e m o d e ra te latitu d es. F o r e x a m p le , th e re w e re tw o lo n g sp ells o f A la s tin g fo r 11 c o n s e c u tiv e d a y s ( 1 0 - 2 0 A p ril 19 7 7 a n d 2 - 1 1 F e b ru a ry 2 0 0 4 ) (T able 5). A lso , T te n d e d to p e rs is t fo r lo n g e r p e rio d s a n d p e a k e d a t 11 d a y s o n e a u tu m n (T able 5).
P o la r c o n tin e n ta l a ir h a s th e w id e s t ra n g e o f p e rs iste n c e s w ith th e lo n g e s t strin g la s tin g fo r 30 d a y s (3 O c to b e r-1 N o v e m b e r 1951) (T able 5 ). A s a r e s u lt o f th a t p a rtic u la r sp e ll o f P o la r c o n tin e n ta l a d v e c tio n , th is p a r t o f E u ro p e su ffe re d a n a c u te p re c ip ita tio n d eficit, in c lu d in g a c o m p le te la c k o f p re c ip ita tio n a t m a n y w e a th e r sta tio n s (C e b u ls k a an d T w a rd o sz 2 0 1 0 ).
L o n g p e rs is te n c e o f a g iv e n cP a ir m a s s is lin k e d w ith a s ta g n a tio n o f h ig h p re s su re sy s te m s o v e r s o u th e rn P o lan d ,
Table 5 The maximum duration o f air masses (1951-2010)
Air masses Spring Summer Autumn Winter
Duration Data o f the beginning and end
Duration Data of the beginning and end
Duration Data o f the beginning and end
Duration Data of the beginning and end
A 11 10-20 April
1977
8 1-8 June 1962 9 13-21 September
1977, 21-29 October 1997
11 9-19 February
2004
mPf 8 21 -28 May
1960, 27 February-6 March 1990
13 13-25 August
1961, 2-14 July 2003, 2-14 August 2006
11 24 September-4
October 1997, 26 October-5 November 1998
6 23-28 December
1954, 14 -19 January 1984
mPo 16 23 March-7
April 1951, 18 April-3 May 2006
16 10-25 June 1989 16 1 -1 6 November
1959, 10-25 October 1980
19 20 December 1960
7 January 1961
mPw 11 26 February-
8 March 1959
7 25 June-1
July 2009
10 7-16 October
1976, 18-27 October 1989
9 30 November-
8 December 2000
cP 22 11 March-1
April 1956
19 23 May-10
June 1963
30 3 October-1
November 1951
21 12 December 1969
1 January 1970
T 11 27 April-7
May 1969
7 7-13 July
2006, 21-27 July 2006
10 4-13 October
1966
4 15-18 December
1964, 19-22 February 1966
vAm 5 21 -25 March
1970, 23-27 March 1992
5 7-11 June 2009 4 8-11 November
1979, 20-23 October 1986
4 6-9 February 1981,
1-4 February 1983, 23-26 December 1983, 20-23 February 1995
Table 6 Frequency (in percent) of overnight change o f air masses during the year
The largest values given in italics
Air mass Air mass on given day
A mPf mPo mPw cP T vPm
Air mass on following day A 56.0 4.4 3.1 2.5 1.2 1.2 14.7
mPf 4.0 47.4 11.0 18.8 2.8 17.4 33.2
mPo 18.8 33.4 61.1 13.4 12.1 13.2 16.8
mPw 2.8 5.4 5.4 45.5 1.7 3.1 7.8
cP 14.2 2.5 10.3 2.1 73.9 3.7 3.7
T 0.2 1.4 1.8 3.8 1.5 46.8 2.2
vAm 4.1 5.6 7.2 13.8 6.8 14.8 21.6
e sp e c ia lly in a u tu m n , w h e n th e y are p re s e n t fo r u p to 60 % o f th e tim e o n a v e ra g e (T w a rd o sz e t al. 2 0 1 1 a , b ). U s in g th e c irc u la tio n c a le n d a r b y N ie d ź w ie d ź ( 1 9 8 1 , 2 0 1 1 ), it w a s e sta b lish e d th a t in O c to b e r 1951 th e d o m in a n t c irc u la tio n w a s a n ticy clo n ic w ith a ir ad v e c tio n fro m th e e a st o r southeast, w h ic h b ro u g h t in th e cP m asses.
5 Succession
S u c c e s s io n is a v e ry im p o rta n t c h a ra c te ristic o f a ir m a sse s, e sp e c ia lly fro m th e p e rs p e c tiv e o f a p p lie d m e te o ro lo g y . A ir m a s se s c a n su c c e e d o n e a n o th e r b y re p la c e m e n t (as a re s u lt o f th e p a s s a g e o f a fro n t) o r th r o u g h tra n sfo rm a tio n , b u t th is d iv isio n is b e y o n d th e sc o p e o f th is study.
In a n a v e ra g e y e a r o f th e stu d y p e rio d , 1 9 5 1 -2 0 1 0 , air m a s se s w e re re p la c e d o r tra n s fo rm e d o n 161 d ay s, o r e v e ry
2.3 d ay s. D iffe re n c e s in fre q u e n c y b e tw e e n w in te r (3 9 d ay s) a n d s u m m e r (41 d a y s) are n o t d u e to d iffe re n t p e rs iste n c e s o f th e a ir m a s se s (o n av erag e approx. 2.3 d ay s, T able 3), b u t to th e d iffe re n t p e rsiste n c e s o f th e seasons. A n a n aly sis o f su c c e ssio n starts w ith sh o w in g o v e rn ig h t c h a n g e s in a ir m asses.
E a c h o f th e six air m a sse s u n d e r co n sid e ra tio n h a s sh o w n its e lf to b e m o re lik e ly to re m a in th e sam e o n th e fo llo w in g d a y th a n to b e su c c e e d e d b y a n o th e r a ir m a s s (T able 6). F o r ex am p le, in 74 % o f all d a y s w ith cP, th is air m a s s c o n tin u e d to a t le a s t th e fo llo w in g d a y a n d o n ly in 2 6 % c a se s w a s it replaced. O n ly th e c a te g o ry o f a “d a y w ith v a rio u s a ir m a s se s”
(v A m ) sh o w e d a re v e rse d p a tte rn w ith th ere b e in g ju s t a 2 2 % ch an ce o f re m a in in g th e sam e o n th e fo llo w in g d a y (it w a s also th e m o s t lik e ly to b e re p la c e d b y m P f air).
T h e issu e o f su c c e ssio n w a s c o n sid e re d b o th in th e w h o le y e a r a n d seasonally. F o r th e w h o le y e a r th e to ta l su ccessio n freq u en cy w a s u s e d (all cases o f su c c e ssio n a c c o u n t fo r 100 %
Table 7 Frequency (in percent) of air mass succession during a year: (A) total frequency and (B) frequency of succession from a given air mass to another
Air mass Air mass on given day
A mPf mPo mPw cP T vAm
A
Air mass on following day A - 1.8 2.3 0.4 0.6 0.1 2.9
mPf 0.7 - 8.3 3.2 1.4 1.2 6.5
mPo 3.5 13.5 - 2.3 5.9 0.9 3.3
mPw 0.5 2.2 4.1 - 0.8 0.2 1.5
cP 2.6 1.0 7.8 0.4 - 0.3 0.7
T 0.0 0.6 1.4 0.7 0.7 - 0.4
vAm 0.7 2.3 5.5 2.4 3.3 1.0 -
B
Air mass on following day A - 8.4 7.9 4.6 4.6 2.2 18.8
mPf 9.1 - 28.3 34.5 10.7 32.7 42.4
mPo 42.6 63.4 - 24.6 46.2 24.7 21.4
mPw 6.4 10.2 14.0 - 6.7 5.8 9.9
cP 32.3 4.7 26.5 3.9 - 6.9 4.7
T 0.4 2.6 4.7 7.1 5.7 - 2.8
vAm 9.2 10.6 18.6 25.4 26.1 27.7 -
Table 8 Frequency (in percent) o f air mass succession during the seasons
A ir mass A ir mass on given day A ir mass A ir mass on given day
A m P f mPo m Pw cP T vArn A m P f mPo m Pw cP T vArn
Spring Autumn
A ir mass on A
-
12.6 10.6 7.5 8.1 5.1 20.8 A ir m ass on A-
8.8 8.6 4.9 2.1 3.1 23.6follow ing day m P f 5.4
-
24.5 30.7 7.2 25.2 40.0 following day m P f 9.7-
26.2 33.5 10.9 31.3 34.8mPo 45.5 59.6
-
22.4 45.3 29.3 19.5 mPo 39.1 58.8-
23.9 44.0 22.9 23.4m Pw 5.8 10.36 14.4
-
4.8 6.1 10.5 mPw 8.2 12.9 17.3-
14.4 12.5 12.0cP 33.5 4.5 26.6 4.8
-
11.1 6.6 cP 36.2 4.1 24.4 2.8-
6.3 2.4T 1.2 2.7 5.7 8.3 5.4
-
2.6 T-
3.1 4.4 9.9 3.9-
3.8vArn 8.6 10.3 18.3 26.3 29.1 23.2
-
vArn 6.8 12.3 19.2 25.0 24.6 24.0-
Summer Winter
A ir mass on A
-
3.9 3.8-
2.8-
6.0 A ir m ass on A-
10.6 9.3 4.2 5.1-
23.8follow ing day m P f 18.4
-
35.2 40.2 15.2 42.9 60.1 following day m P f 9.1-
26.2 36.1 9.8 19.4 35.8mPo 52.9 76.1
-
18.9 38.0 19.5 22.7 mPo 38.7 53.6-
30.0 57.9 36.1 20.3m Pw 1.1 5.3 8.5
-
4.1 0.8 3.7 m Pw 7.4 14.5 16.8-
4.0 5.6 13.1cP 17.2 5.6 29.9 4.5
-
2.3 4.0 cP 33.0 4.3 24.6 3.8-
13.9 5.6T
-
3.6 5.9 8.3 11.7-
3.4 T-
0.7 2.5 2.3 1.3-
1.3vArn 10.3 5.6 16.7 28.0 28.2 34.6
-
vArn 11.7 16.3 20.6 23.6 21.9 25.0 -The largest values given in italics
ariabilityof airmass occurrence in southern Poland(1951-2010)
Table 7a) as w e ll as th e b re a k d o w n o f su c c e ssio n o f a g iv e n air m a s s (100 % ) b y o th e r air m a s se s (T able 7 b ). T h e seaso n al an aly sis c o n sid e re d o n ly th e latter b re a k d o w n (T able 8).
A su m m a ry o f th e a n n u a l su c c e ssio n fre q u e n c y (T able 6 a ) sh o w s th a t e a c h a ir m a s s ca n b e su c c e e d e d b y a n y other. T he m o s t fre q u e n t su c c e ssio n is fro m m P f to m P o a t 13.5 % o f all su ccessio n s (1 ,3 0 7 su c c e ssio n days). I t c a n b e a ttrib u te d to a n a tu ra l re s u lt o f th e circu latio n p ro c e sse s p re s e n t in th e stu d y area, in v o lv in g a tra n sfo rm a tio n o f a fresh air m a s s as it arrives fro m th e A tlan tic O c e a n a n d v e n tu re s d e e p e r o v e r th e c o n ti
nent. O th e r fre q u e n t su ccessio n s in clu d e fro m m P o to m P f (8.3 % su ccessio n s in a y ear), m P o to cP (7.8 % ) a n d cP to m P o (5.9 % ). O verall, th ere is a greater lik e lih o o d o f w a rm air b e in g re p la c e d b y c o o l a ir th a n v ic e versa. T h e le a st freq u en t are m u tu a l s u c c e s s io n s o f tw o a ir m a s s e s o rig in a tin g o u ts id e m o d e r a te la titu d e s : A to T (0.1 % , th re e case s) a n d T to A (0 .2 % , e ig h t c a se s ), w h ic h is d u e to th e lo w fre q u e n c y o f th e a ir m a s s e s th e m s e lv e s , e s p e c ia lly o f T. D ir e c t s u c c e s s io n s b e tw e e n th e s e tw o ty p e s o f a ir c a n a lso h a v e b io m e te o r o lo g ic a lly a d v e rs e e ffe c ts, d u e to th e ir e x tr e m e ly d if fe re n t p h y s ic a l p ro p e rtie s .
F ro m th e p e rs p e c tiv e o f w e a th e r fo re c a stin g , it is th e fre q u e n c y o f s u c c e s sio n s b e tw e e n c e rta in a ir m a s s e s th a t is m o re im p o rta n t. A s c o u ld h a v e b e e n e x p e c te d , th e re is a v e ry h ig h lik e lih o o d th a t a d a y w ith m P f w ill b e fo llo w e d b y a d a y w ith m P o , w h ic h a c c o u n te d fo r 63 % o f m P f su c c e s
sio n s b y a n y o th e r a ir (T able 7 b ). T h is is c a u s e d b y th e c irc u la tio n e ffe c t m e n tio n e d earlier. N o o th e r a ir m a s s h a s a c o m p a ra b le lik e lih o o d o f su c c e s s io n b y a n o th e r sp e c ific air m a s s (m o re th a n 50 % ). m P o is a ls o th e m o s t fre q u e n t s u c c e s s o r to A a n d cP, b u t w ith le s s th a n 5 0 % lik e li
h o o d . D a y s w ith m P o , m P w , T, o r v A m a re m o s t lik e ly to b e f o l lo w e d b y m P f ( a t 2 8 , 3 5 , 33 a n d 4 2 % , re s p e c tiv e ly ).
T h e s e a s o n a l su c c e s s io n fre q u e n c y (T ab le 8) d is p la y s sim ila ritie s w ith th e a n n u a l p a tte rn d e s c rib e d ab o v e. T h ere is a h ig h lik e lih o o d o f a d a y w ith m P o a fte r a d a y w ith m P f, ra n g in g fro m 54 % in w in te r to 7 6 % in sum m er. T h e re is a g ro w in g fre q u e n c y o f a d a y w ith m P o a fte r A in s u m m e r a t 53 % a n d a fte r c P in w in te r a t 58 % . A ll c a s e s o f th e su c c e s s io n o f T a fte r A o c c u rre d in sp rin g . N o c a se s o f d ire c t m u tu a l su c c e s s io n b e tw e e n A a n d T, in a n y d ire c tio n , w e re re c o rd e d in w in te r a n d sum m er.
6 Conclusions
T h e stu d y d is c u sse s th e v a ria b ility o f o c c u rre n c e o f six air m a s s ty p e s in so u th e rn P o la n d lo o k in g a t th e ir a n n u a l a n d se a s o n a l fre q u e n c ie s, p e rs iste n c e , a n d su c c e s s io n p a tte rn s d u rin g th e p e rio d 1 9 5 1 -2 0 1 0 .
T h e m o s t fre q u e n t a ir m a s s e s in P o la n d in c lu d e m P o a t ap p ro x 33 % d a y s a n d cP a t a p p ro x 21 % d ay s. T h e se are
ty p ic a l a ir m a s se s o f th e s tu d y a r e a ’s c lim a te zo n e a n d th e y sh o w n o s ig n ific a n t seaso n ality . T h e o th e r fo u r ty p e s o f air m asses, o n th e o th e r h a n d , are clea rly se a so n a l in th e ir fre
q u e n c y v ariab ilities, e sp ecially th e ex o tic o n e s (A a n d T).
D esp ite c o n sid erab le seaso n al d ifferen ces in th e freq u en cy o f o ccu rren ce, th e av erag e p ersisten ce o f a ir m a s se s is sim ilar fo r m o s t o f th e m a t ca. 2 d ay s. S ig n ifican t d ifferen ces are o n ly v isib le in th e m P f, w h ic h ra n g e s fro m 1 .7 ± 0 .1 d a y s in w in te r a n d sp rin g to 2 .2 ± 0 .1 d a y s in sum m er. T h is m e a n s th a t th ere is n o sim p le d e p e n d e n c y b e tw e e n th e p e rs iste n c e o f each p a rtic u la r air m a s s a n d its frequency. T h e re is, h o w ev er, a h ig h d e g re e o f seaso n al d ifferen ce b e tw e e n th e air m a sse s in th e ir av erag e p e rsiste n c e ra n g in g fro m 1.6 d a y s in su m m er (1.6 d a y s o f m P w a n d 3.2 d ay s o f cP ) to 2.9 in w in te r (1.6 o f T a n d 4.3 o f cP). T h e g re a te st v a ria b ility in p ersisten ce is fo u n d in cP air, w h ic h re a c h e s 30 d a y s in autum n.
T h e p e rs iste n c e o f a g iv e n a ir m a s s is lin k e d m o re to th e d ire c tio n o f its a d v e c tio n th a n to th e fre q u e n c y o f o c c u r
ren ce. E a s te rn a n tic y c lo n ic c irc u la tio n , k n o w n fo r its sta b il
ity, is p a rtic u la rly c o n d u c iv e to lo n g e r p e rs iste n c e s a n d th is is w h y cP a ir te n d s to p e rs is t fo r longer. M a ritim e a ir fro m th e w e s t te n d s to b e q u ic k ly tra n s fo rm e d o v e r th e c o n tin e n t a n d d o e s n o t la s t fo r as lo n g . T h is tra n s fo rm a tio n p ro c e s s is a t its q u ic k e s t in w in te r a n d sp rin g a n d a t its slo w e s t in su m m er, a re s u lt o f se a s o n a l v a ria b ility in c y c lo n ic activity.
T h e s tu d y o f s u c c e s sio n b e tw e e n a ir m a s se s h a s s h o w n t h a t e a c h a ir m a s s c a n b e r e p la c e d b y a n y o th e r ty p e , a lth o u g h th e re w e re n o re c o r d e d c a s e s o f d ir e c t m u tu a l s u c c e s sio n o f A a n d T a ir m a s se s in w in te r a n d sum m er.
T h ere is also a v e ry h ig h lik e lih o o d th a t a d a y w ith m P f air w ill b e fo llo w e d b y a d a y w ith m P o air. In d eed , th is p a tte rn a cco u n ts fo r 63 % o f su ccessio n s o f th e fo rm er b y a n y o th er air a n d in su m m e r th e p ro p o rtio n is 76 % . T h is p a tte rn is a n a tu ra l re s u lt o f circ u la tio n pro c e sse s in th e tem p erate clim ate z o n e in v o lv in g a tra n sfo rm a tio n o f m aritim e a ir m a s se s o v e r th e c o n tin e n t. N o o th e r a ir m a s s is s u c c e e d e d w ith s u c h fre q u e n c y b y a n y o th e r sp ecific a ir m a s s ty p e (m o re th a n 50 % ). F inally, th e stu d y h a s c o n firm e d a n e x p e c ta tio n th a t th e m o s t fre q u e n t su ccessio n s w o u ld in v o lv e th e a ir m a sse s w ith th e m o s t fre q u e n t occurrence.
Acknowledgments I thank Mr. Paweł Pilch and Dr. Martin Cahn for reviewing the English language.
Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
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