Circulation Types and Their Influence on the Interannual Variability
225
Each anticyclonic circulation type is defined according to the location of the positive
anomaly centre. Similarly, each cyclonic circulation type is defined according to the
location of the negative anomaly centre. This classitication produces 6 anticyclonic
types (A NW , AND A, Asw, ASE and A E , Fig. 14a) and 8 cyclonic types (C, Cs, Csw, CNW'
C NE . CSE, C N and Cw, Fig. 14b). The characterisation A, ANW or C, Csw refers to the
location of the positive or negative anomaly centre in relation to the Greek area.
4.2 Short Description of the Circulation Types
It is expected that each of the 14 circulation types should have a characteristic
synoptic pattern, which is physically distinct and produces the expected weather type
direction of surface and upper-air flow and associated air-masses. In order to test this,
and to describe the circulation types, composite maps showing the mean anomaly
pattern were constructed from the SOOhPa anomaly data field for each circulation type
and each season. Only maps for winter are shown here (Fig. 15 and 16).
The anticyclonic types are:
ANW The positive anomaly centre is located to the northwest of the Greek area,
usually over western, central or northern Europe (France, Germany, Italy,
Austria or Scandinavia, Fig. 14a). Positive anomalies are always prevalent over
the Greek area (Fig. lSa).
ANE The positive anomaly centre is located to the northeast of the Greek area (Fig.
14a). Positive anomalies are located over the Greek area (Fig. ISb).
A
The positive anomaly centre is located over the Balkans and Greek area (Figs.
14aand lSc).
Asw The positive anomaly centre is located to the west or southwest of Greece,
generally over the central or western Mediterranean, or north Africa (Figs. 14a
and ISd).
ASE The anticyclonic anomaly centre is located to the southeast of Greece (Figs.
14a and lSe).
AE
The anticyclonic anomaly centre is located to the east of the Greek area (Figs.
14a and ISf).
The Cyclonic types are the following:
C
The negative anomaly centre is located over the Greek area (Figs. 14b and
16a).
C s
The centre of the negative anomaly system is located to the south or southeast
of the Greek area (Figs. 14b and 16b).
C sw The centre of the negative anomaly system is located to the west or southwest
of the Greek area (Fig. 16c).
C NW The negative anomaly centre is located to the northwest of the Greek area (Fig.
16d), usually over the Adriatic Sea.
C NE The centre of the negative anomaly system is located to the east or northeast
of the Greek area (Fig. 16e), usually over the Black Sea.
C SE The negative anomaly centre is located to the southeast of the Greek area (Fig.
16f), usually over or near Cyprus.
C N The centre of the negative anomaly system is located to the north of the Greek
area, usually north of 50° N (Fig. J6g).
225
Each anticyclonic circulation type is defined according to the location of the positive
anomaly centre. Similarly, each cyclonic circulation type is defined according to the
location of the negative anomaly centre. This classitication produces 6 anticyclonic
types (A NW , AND A, Asw, ASE and A E , Fig. 14a) and 8 cyclonic types (C, Cs, Csw, CNW'
C NE . CSE, C N and Cw, Fig. 14b). The characterisation A, ANW or C, Csw refers to the
location of the positive or negative anomaly centre in relation to the Greek area.
4.2 Short Description of the Circulation Types
It is expected that each of the 14 circulation types should have a characteristic
synoptic pattern, which is physically distinct and produces the expected weather type
direction of surface and upper-air flow and associated air-masses. In order to test this,
and to describe the circulation types, composite maps showing the mean anomaly
pattern were constructed from the SOOhPa anomaly data field for each circulation type
and each season. Only maps for winter are shown here (Fig. 15 and 16).
The anticyclonic types are:
ANW The positive anomaly centre is located to the northwest of the Greek area,
usually over western, central or northern Europe (France, Germany, Italy,
Austria or Scandinavia, Fig. 14a). Positive anomalies are always prevalent over
the Greek area (Fig. lSa).
ANE The positive anomaly centre is located to the northeast of the Greek area (Fig.
14a). Positive anomalies are located over the Greek area (Fig. ISb).
A
The positive anomaly centre is located over the Balkans and Greek area (Figs.
14aand lSc).
Asw The positive anomaly centre is located to the west or southwest of Greece,
generally over the central or western Mediterranean, or north Africa (Figs. 14a
and ISd).
ASE The anticyclonic anomaly centre is located to the southeast of Greece (Figs.
14a and lSe).
AE
The anticyclonic anomaly centre is located to the east of the Greek area (Figs.
14a and ISf).
The Cyclonic types are the following:
C
The negative anomaly centre is located over the Greek area (Figs. 14b and
16a).
C s
The centre of the negative anomaly system is located to the south or southeast
of the Greek area (Figs. 14b and 16b).
C sw The centre of the negative anomaly system is located to the west or southwest
of the Greek area (Fig. 16c).
C NW The negative anomaly centre is located to the northwest of the Greek area (Fig.
16d), usually over the Adriatic Sea.
C NE The centre of the negative anomaly system is located to the east or northeast
of the Greek area (Fig. 16e), usually over the Black Sea.
C SE The negative anomaly centre is located to the southeast of the Greek area (Fig.
16f), usually over or near Cyprus.
C N The centre of the negative anomaly system is located to the north of the Greek
area, usually north of 50° N (Fig. J6g).