80
W. Alpers
Fig. 4.2 a Wind field
measured by Quikscat
(resolution: 25 km) at 1919
UTC on 9 February 2006 over
the Atlantic Ocean off the
coast of Morocco and Spain.
The inserted thick black line
denotes the approximate
position of the atmospheric
front, where the wind
direction and speed change.
b Location of the SAR swath
(width: 100 Km) of Envisat
ASAR, which imaged this
wind front at 2214 UTC on 9
February 2008. c Section of a
SAR image acquired by
Envisat ASAR showing the
atmospheric front at high
resolution (25 m). © Remote
Sensing Systems, ESA
4.2.2 Wind Front
Wind fronts, defined as fronts where wind direction and speed change, are also
detectable by scatterometers. An example is depicted in Fig. 4.2a, which shows the
near-surface wind field over the Atlantic Ocean off the west coast of Morocco, North
Africa, which was retrieved from Quikscat data acquired at 1919 UTC on 9 February
2006. The poor spatial resolution of 25 km of Quikscat allows only an approximate
determination of the position of the atmospheric front, see the black line inserted
in the wind map (Fig. 4.2a). However, atmospheric fronts and other atmospheric
phenomena in the marine boundary layer are resolved much better by SAR as will be
shown in the Sect. 4.3.1. Here we show for comparison a section SAR image which
was acquired by the SAR onboard the Envisat satellite, called Advanced Synthetic
Aperture Radar (ASAR), 2 h and 55 min later (at 2214 UTC) than the Quikscat data.
The SAR image was acquired in the Image Mode (IM) along the swath depicted in
Fig. 4.2b (swath width: 100 km) during an asceding pass of the satellite. A section
of this SAR is depicted in Fig. 4.2c, which shows the same atmospheric front with a
W. Alpers
Fig. 4.2 a Wind field
measured by Quikscat
(resolution: 25 km) at 1919
UTC on 9 February 2006 over
the Atlantic Ocean off the
coast of Morocco and Spain.
The inserted thick black line
denotes the approximate
position of the atmospheric
front, where the wind
direction and speed change.
b Location of the SAR swath
(width: 100 Km) of Envisat
ASAR, which imaged this
wind front at 2214 UTC on 9
February 2008. c Section of a
SAR image acquired by
Envisat ASAR showing the
atmospheric front at high
resolution (25 m). © Remote
Sensing Systems, ESA
4.2.2 Wind Front
Wind fronts, defined as fronts where wind direction and speed change, are also
detectable by scatterometers. An example is depicted in Fig. 4.2a, which shows the
near-surface wind field over the Atlantic Ocean off the west coast of Morocco, North
Africa, which was retrieved from Quikscat data acquired at 1919 UTC on 9 February
2006. The poor spatial resolution of 25 km of Quikscat allows only an approximate
determination of the position of the atmospheric front, see the black line inserted
in the wind map (Fig. 4.2a). However, atmospheric fronts and other atmospheric
phenomena in the marine boundary layer are resolved much better by SAR as will be
shown in the Sect. 4.3.1. Here we show for comparison a section SAR image which
was acquired by the SAR onboard the Envisat satellite, called Advanced Synthetic
Aperture Radar (ASAR), 2 h and 55 min later (at 2214 UTC) than the Quikscat data.
The SAR image was acquired in the Image Mode (IM) along the swath depicted in
Fig. 4.2b (swath width: 100 km) during an asceding pass of the satellite. A section
of this SAR is depicted in Fig. 4.2c, which shows the same atmospheric front with a