Global Change Abstracts The Swiss Contribution - SCNAT

Global Change Abstracts – The Swiss Contribution | Atmosphere 55
08.1-49
Aerosol scattering as a function of altitude in
a coastal environment
Marshall J, Lohmann U, Leaitch W R, Lehr P,
Hayden K
Canada, Switzerland
Meteorology & Atmospheric Sciences
(1) An optical closure study was carried out on
the basis of measurements taken during five research
flights in October 2003 over the waters surrounding
Nova Scotia. Measurements of aerosol
size spectra were made using a variety of instruments,
and the size- segregated chemical signature
was determined with an Aerodyne Aerosol
Mass Spectrometer. The aerosol scattering and
backscattering coefficients were determined
with an integrating nephelometer at three visible
wavelengths. At a wavelength of 550 nm and
at altitudes less than 1000 m, the mean total scattering
coefficient of the dry in-cabin aerosol is 26
Mm(-1), with a standard deviation of 10 Mm(-1) ,
while the mean backscattering coefficient is 1.7
Mm(-1) with a standard deviation of 0.8 Mm(-1).
On the basis of data from instruments within
the cabin, closure between the directly measured
and calculated total scattering coefficients is attained
for more than 70% of cases, but is not attained
for the backscattering coefficients. Coarse
particles are found to account for roughly half
of the total scattering and 70% of the backscattering
for altitudes up to similar to 1000 m. The
scattering contribution from coarse particles is
found to account for approximately 65% of the
total scattering and 88% of the backscattering
when calculated on the basis of measurements
taken outside of the aircraft, which are not subject
to inlet losses for larger particles.
Journal of Geophysical Research Atmospheres,
2007, V112, ND14, JUL 21 ARTN: D14203.
08.1-50
Breaking waves at the tropopause in the wintertime
Northern Hemisphere: Climatological
analyses of the orientation and the theoretical
LC1/2 classification
Martius O, Schwierz C, Davies H C
Switzerland
Meteorology & Atmospheric Sciences
Breaking waves on the tropopause are viewed as
potential vorticity (PV) streamers on middle-world
isentropic levels. A Northern Hemisphere winter
climatology of the streamers’ spatial distribution
and meridional orientation is derived from
the 40-yr ECMWF Re- Analysis (ERA-40) dataset,
and used to assess the nature and frequency of
occurrence of breaking synoptic-scale waves. The
streamers are grouped into two classes related to
the so-called cyclonic (LC2) and anticyclonic (LC1)
patterns, and the ambient wind strength and wind
shear is also noted. It is shown that the occurrence
of cyclonic and anticyclonic PV streamers exhibits
a distinct spatial variability in the horizontal and
the vertical. The majority of cyclonic PV streamers
are found on lower isentropic levels that intersect
the tropopause at more poleward latitudes,
whereas anticyclonic streamers predominate at
higher elevations in the subtropics. An analysis of
the streamer patterns for the two phases of the
North Atlantic Oscillation (NAO) reveals significant
differences in the location and frequency of
both cyclonic and anticyclonic streamers in the
Euro-Atlantic region on the 310-K isentropic level.
Likewise, for the two phases of the ENSO and the
Pacific-North American (PNA) pattern, there are
marked differences in the frequency pattern of
cyclonic streamers. An examination of the tropopause-level
hemispheric flow pattern at the time
of and prior to a streamer’s formation indicates
a linkage to the presence or absence of double jet
structures.
Journal of the Atmospheric Sciences, 2007, V64,
N7, JUL, pp 2576-2592.
08.1-51
Comparison between backscatter lidar and
radiosonde measurements of the diurnal and
nocturnal stratification in the lower troposphere
Martucci G, Matthey R, Mitev V, Richner H
Switzerland
Meteorology & Atmospheric Sciences , Instruments
& Instrumentation
A collection of boundary layer heights has been
derived from measurements performed by a
ground-based backscatter lidar in Neuch tel, Switzerland
(47.000 N, 6.967 E, 485 m ASL). A dataset
of 98 cases have been collected during 2 yr. From
these data, 61 are noon and 37 are midnight cases.
The following two different schemes were used to
retrieve the mixed layer depth and the height of
the residual layer from the measurements: the
gradient and variance methods. The obtained values
were compared with those derived from the
potential temperature profiles as computed from
radiosonde data. For nocturnal cases, the height
of the first aerosol layer above the residual layer
was also compared to the corresponding potential
temperature value. Correlation coefficients
between lidar and radiosonde in both convective
and stable conditions are between 0.88 and 0.97.
Journal of Atmospheric and Oceanic Technology,
2007, V24, N7, JUL, pp 1231-1244.