Geoscience Reference
In-Depth Information
1 Surface Pressure Variations and Deformation
of the Solid Earth
Differential heating between low and high latitudes gives rise to atmospheric motions
on a wide range of scales. Prominent features of the so-called atmospheric general
circulation include westerly (west-to-east) mid-latitude tropospheric jet streams and
lower mesospheric jet streams. Superimposed on the jet streams are eastward prop-
agating baroclinic waves that are one of a number of types of weather systems.
Examples of baroclinic waves are cyclones and anticyclones, which are represent-
ing variations of low and high air pressure from mean pressure (Wallace and Hobbs
2006
). Figure
1
shows spatial variations of surface pressure anomaly (the pressure
minus a mean of the pressure field) over the Northern hemisphere (10-90
◦
N) at 00
UTC on January 1, 2010. The highest pressure anomaly (
25hPa) is over the far
northern portions of Siberia and North America extending into the Arctic Ocean.
The lowest pressure anomaly (
≈
35hPa) is over the middle Atlantic Ocean, south
of Iceland. Both cyclones and anti-cyclones typically have spatial extent between
some hundreds (tropical cyclones) and some thousands (continental anti-cyclones)
of kilometers. Their duration is generally of the order of a few days and sometimes
they can remain stable for weeks (Rabbel and Zschau
1985
).
≈−
Fig. 1
Surface pressure
anomaly (the pressure minus
a mean of the pressure field)
over Northern hemisphere
(10-90
◦
N) from data of
the European Centre for
Medium-range Weather Fore-
cast (ECMWF) at 00 UTC on
January 1, 2010
Surface pressure anomaly
°
−180
30
°
6
0
°
−120
°
120
°
90
°
− 60
°
60
°
0
°
−40
−30
−20
−10
0
10
20
30
hPa
