Extension and combination of existing remote-sensing instruments [Elektronische Ressource] : an investigation of remote-sensing VMR-profiles from the ground to the mesopause / vorgelegt von Mathias Palm

Informations

• Publié par: universitat_bremen
• Publié le: 01 janvier 2006
• Nombre de lectures: 9
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Extension and combination of
existing remote sensing
instruments.
An investigation of remote sensing VMR profiles
from the ground to the mesopause.
Dissertation
zur Erlangung des Grades
Dr. rer. nat.
der Universität Bremen
vorgelegt von
Mathias Palm
März 2006Contents
Abstract 7
Introduction 9
1 Structure, dynamics and chemistry of the atmosphere 13
1.1 Vertical structure of the atmosphere 13
1.2 Dynamic transport in the 14
1.2.1 Common definitions and approximation 16
1.2.2 Dynamic transport in the stratosphere and mesosphere 17
1.2.3 The polar vortex 18
1.2.4 Dynamic transport in the troposphere 18
1.2.5 Stratosphere troposphere exchange 19
1.3 Chemistry in the mesosphere and stratosphere 20
1.3.1 The ionosphere 21
1.3.2 Oxygen chemistry 21
1.3.3 Hydrogen 23
1.3.4 Nitrogen chemistry 24
1.4 Destruction of O in the stratosphere and mesosphere 263
1.4.1 Catalytic destruction of O 263
1.4.2 Non catalytic destruction ofO 283
1.5 O chemistry of the troposphere 293
1.6 Summary of chapter 1 30
2 Theoretical background of MW- and IR spectroscopy 33
2.1 The radiative transfer 34
2.1.1 The absorption coefficient 35
2.2 The microwave spectrometer (RAM) 39
2.2.1 Overview 39
2.2.2 Calibration of the measured spectra 41
34 CONTENTS
2.2.3 The radiometer equation and the sensitivity of the RAM 43
2.3 The Fourier transform spectrometer (FTIR) 43
2.3.1 Description of the instrument 44
2.3.2 The radiative transfer specialised to FTIR spectroscopy 45
2.4 The inversion 45
2.4.1 Statement of the problem 45
2.4.2 Characterisation of the forward model 46
2.4.3 Optimal estimation (OE) 47
2.4.4 Interpretation of the a priori 48
2.4.5 Quantities characterising the inversion process 48
2.4.6 Error analysis 54
2.5 Summary of chapter 2 55
3 Intercomparison of profiles 57
3.1 Intercomparison of indirect measurements 58
3.1.1 Direct comparison 59
3.1.2 Simulating one retrieval with another 59
3.2 The SCIAMACHY instrument on ENVISAT 60
3.3 Collocation of OZORAM and SCIAMACHY O profiles 613
3.4 Comparison of OZORAM profiles with SCIAMACHY profiles 62
3.4.1 Properties of the RAM profiles used in the comparison 62
3.4.2 Comparison with SCIAMACHY stratosphere profiles 63
3.4.3 withCHY mesosphere 67
3.5 Summary of chapter 3 72
4 Extension of existing RAM instruments 73
4.1 Combining the RAM and the FTIR spectrometer 73
4.1.1 Theoretical studies 74
4.1.2 Results 75
4.2 Sensing the mesosphere using microwave spectroscopy 80
4.2.1 The set up of the microwave radiometers in Ny Ålesund 84
4.2.2 Description of the fine spectrometer (FS) 85
4.2.3 Theoretical studies of the perfomance of the FS at the
142 GHz O line 863
4.2.4 Results and interpretion of the modelled runs 91
4.2.5 The solar proton event October/November 2003 97
4.2.6 RAM measurements of the SPE 2003 97CONTENTS 5
4.2.7 SCIAMACHY measurements of the SPE 2003 103
4.2.8 Theoretical studies of the performance of the FS at the
22 GHz H O line 1032
4.2.9 Summary of chapter 4 106
5 Summary 109
Appendix 111
A Mathematical details 113
A.1 The Singular Value Decomposition (SVD) 113
A.1.1 The definition of the SVD 113
A.1.2 The Moore Penrose pseudo inverse 113
A.1.3 The interpretation of the SVD 114
A.2 Representing error covariances 115
A.3 Selected properties of the mean and the variance 116
Acknowledgements 117
B Bibliography 119Abstract
This dissertation explores possible ways to extend the remote sensing capa
bilities of existing instruments.
In the theoretical part, the O chemistry up to the mesosphere will be3
reviewed with emphasis on O changes due to precipitation of solar particles3
into the atmosphere. The theoretical background of remote sensing in the
microwave and far infrared region will be sketched. Finally the retrieval
theory based on Optimal estimation (Rodgers, 2000) will be reviewed.
In the practical part, extensions to existing instruments will be introduced.
First a combination of a microwave spectrometer with a Fourier transform
spectrometer is theoretically investigated and applied to artificially created
O and H O spectra. O profiles can be retrieved from ground level to the3 2 3
mesosphere using the combination of the two sensors. In the region from
15 km to 35 km, where both instruments are able to ‘see’ O , the results3
are improved compared to the results obtained by either instrument alone.
H O spectra are also combined and retrieved. While it is shown to be pos 2
sible to retrieve combined spectra, there is a pronounced information gap
between the tropopause and the middle stratosphere which makes it difficult
to retrieve information of the H O content in the tropopause region.2
In a second part, an add on spectrometer to the existing microwave ra
◦diometers, OZORAM and H2ORAM, in Ny Ålesund, Spitsbergen (79 N),
is devised and explored. The new spectrometer enables a resolution as fine
as 100 kHz which makes it possible to retrieve O , from the 142 GHz line,3
and H O profiles, from the 22.2 GHz line, up to 75 km. Investigations have2
been undertaken in order to define the properties of an instrument which is
able to refine the H O spectra at 22.2 GHz even further. Due to the weak2
emission this is more difficult than for the prominent O line at 142 GHz.3
The spectra taken during the October/November 2003 Solar Proton
Event (SPE) by the OZORAM at Ny Ålesund have been reanalysed using
78
an optimised retrieval set up based on Qpack/arts to investigate the SPE and
to compare the measured O VMR (volume mixing ratio) to the evolution3
of the O VMR predicted by a 2 dimensional model.3
Additionally, a method of comparing profiles obtained from different re
mote sensors is reviewed and demonstrated. The results are used to back up
the results based on the existing spectra for the SPE 2003.Introduction
The atmosphere is in many respects crucial for the earth as we know it,
particularly for life. It not only serves as an important reservoir of oxygen
which is the basis of the metabolism of most fauna, including humanity; it
also provides a shield from dangerous energetic rays from the sun such as
UV radiation. The atmosphere is important in maintaining a relatively con
stant temperature. Compared to the moon, for example, where temperature
◦differences on the surface range from 150 C (during the night) to 100
◦C (during the day), the climate on earth is moderate (diurnal extremes are
about 40 K in some places but usually not more than about 20 K). Not only
does the atmosphere moderate the diurnal differences in energy input from
outer space, it also keeps the temperature within a range which is suitable to
life on earth. This is achieved by a complex combination of storing energy
(greenhouse effect), transforming it (e.g. short wave radiation is absorbed
and long wave radiation is emitted) and radiating parts of it back into outer
space.
The study of the atmosphere began in the early 20th century (e.g. ozone
research by Dobson et al., 1925). The discovery of the O hole over the3
Antarctic in 1985 (Farman et al., 1985) and its relation to the release of
1CFC’s in the atmosphere sparked a great interest in the physics and chem
istry of the atmosphere. It quickly became clear that O is a major player3
in the temperature and radiation budget of the atmosphere, even though
2it is only found in traces. The O layer shields the earth’s surface from3
dangerous UV radiation and is an important greenhouse gas (Brasseur and
1 Chloro fluorocarbons - non toxic substances which are chemically inert in the troposphere.
They are used for many applications in refrigeration, etc. The CFC’s are photo dissociated
in the upper stratosphere and the halogens thus released may function as a catalyst in O -3
destroying reactions.
2 Most of the O is found in the stratosphere between 15 and 50 km altitude.3
910
Solomon, 1986). The research about the O chemistry in the atmosphere led3
quickly to political action, the so called ‘Montreal protocol’ (UNEP, 2000),
which brought about a worldwide ban of CFC’s. This was possible in part
because the destruction of the O layer could be traced back with certainty3
to the influence of mankind.
The chemistry of the stratosphere has been well researched the last dec
ades. Recently the focus has shifted both downwards and upwards. A part of
the thesis presented here deals with measurement techniques for the lower-
most stratosphere and the mesosphere. The influence of the sun on the chem
istry of the earth becomes more pronounced the higher one gets. Particle
events such as the ejection of mass by the sun influence the chemistry in the
mesosphere and even, due to downward transport, in the stratosphere. Re
cently published studies establish a disturbance of the O chemistry for as3
long as 6 months after the occurrence of such an event (Randall et al., 2005).
Measurements are also necessary to establish the performance of chemical
models. Attempts to model the impact of an Solar Proton Events (SPE) have
been made by Jackman and Fleming (2000) and Sinnhuber et al. (2004),
among others, and compared to measurements by Jackman et al. (2001) and
Rohen et al. (2005b). Earlier attempts can be found in Solomon et al. (1981),