download pdf - Institut für Umweltphysik - Ruprecht-Karls-Universität ...

30 CHAPTER 2. ATMOSPHERE AND REMOTE SENSING
2.1.12 Long Term Observations of Urban Atmospheric Radical Chemistry
(TURBAN)
Participating scientists Jutta Zingler, Christoph Kern, Daniel Pedersen, Valeri Matveev, Mordechai
Peleg, Ulrich Platt, Menachem Luria
Abstract Using Long Path DOAS and MiniDOAS, seasonal and spatial patterns in the chemistry
of NO3 in an arid urban location are investigated. Its contribution to the transformation and removal
of atmospheric compounds is evaluated. Long term measurements are validated and complemented
by a short term intensive measurement period.
Figure 2.12: Vertical NO3 profiles: Measurement geometry for the MiniDOAS part of this study.
Background The nitrate radical (NO3) is a
key component of nighttime chemistry in the
troposphere and is responsible for the nonphotochemical
production of peroxy radicals and
the transformation of important species such as
nitrogen oxides, VOCs, and ozone. It can be comparable
to the OH radical as a sink for nitrogen
oxides and VOCs. Up to this project, the only
two studies to provide long term nighttime measurements
of NO3 in the boundary layer were conducted
in Germany at a rural coastal site [Heintz
et al. , 1996] and at a rural suburban site [Geyer
et al. , 2001]. One short-term study reported daytime
measurements of NO3 [Geyer et al. , 2003].
Funding German Israeli Foundation for Scientific
Research and Development (G.I.F.)
Methods and results A long term monitoring
station has been established by the Hebrew
University of Jerusalem in the urban center of
Jerusalem, including a Long Path DOAS system
and several monitors for a variety of atmospheric
trace gases and parameters. During an intensive
one month joint field work campaign, IUP Heidelberg
has set up a high end Long Path DOAS
system aiming for quality control, high time resolution
and enhancement of species investigated.
A red LED as alternative light source and new
technology was applied successfully during some
days.
Vertical profiles of NO3 have been measured
using an advanced MiniDOAS system equipped
with a VIS mini-spectrograph (MiniTURBAN).
Stray light spectra acquired during sunrise give
an idea on the concentration profiles in higher atmospheric
layers.
Information on photolytic rates is retrieved
from solar radiation measurements with a spectral
radiometer.
Our long path measurements yielded positive
results for NO3 during almost every night, with
mixing ratios up to 300 ppt. NO3 was found during
a period of very high humidity. Good agreement
could be found comparing NO2 Long Path
DOAS data with in situ monitor results.
Outlook/Future work Evaluation improvement,
intercomparison/correlation of data, quality
control for long term data, profile modelling,
investigation of photolysis parameters.
Main publication in preparation