<p>Atmospheric particles are ubiquitous in the Earth’s atmosphere and have potential to influence atmospheric chemistry, visibility, global climate and human health, particularly downwind from major pollution sources. The main objective of this thesis was to investigate questions pertaining to the microphysical, chemical and optical properties of aerosol particles by using in situ data collected during four experiments carried out in different regions of the Northern Hemisphere.</p><p>The first two papers of this thesis reports on airborne measurements of the aerosol optical properties performed over the North Atlantic and the Los Angeles basin. Airmasses from Europe and North Africa are usually advected in over the North Atlantic, alternating with the background marine conditions. The results showed that the aerosols are not uniformly distributed in the area and variability in the aerosol fields occurs at sub-synoptic scales. It was also observed that the single scattering coefficient varied as the polluted plumes aged, suggesting a relationship between this quantity and transport time. The measurements performed around the Los Angeles basin showed that the area’s complex topography and local meteorological circulations exert a strong control on the distribution of the aerosol in the basin. Large spatio-temporal gradients in the aerosol optical properties were observed along a transect flown from the shore towards the mountains. Profiles flown over sites located on the mountains displayed a stratified configuration with elevated aerosol layers.</p><p>Airborne data of residual particles collected in orographic wave clouds over Scandinavia were analyzed using a single particle analysis technique. Mineral dust, organic aerosols and sea salt were the main group of particles identified. Residuals composed predominantly of mineral dust were found in glaciated clouds while organic residuals were found in liquid clouds. The results suggest that organic material may inhibit freezing and have considerable influence on supercooled clouds that form through heterogeneous pathways.</p><p>The partitioning of the aerosol particles between cloud droplets and interstitial air has been addressed in terms of their microphysical properties using data obtained at a mountain-top site in Sweden during a stratocumulus event. The results showed that the scavenging efficiency varied during the cloud event, and Aitken-mode particles were also efficiently scavenged in addition to accumulation-mode particles. It is hypothesized that alterations of the aerosol chemical composition occurred during the measurement period, modifying the hygroscopic nature of the particles and decreasing their activation diameter.</p>

<p>This thesis concerns the fate of the meteoric smoke in the Middle Atmosphere, and its effect on ice phenomena such as noctilucent clouds (NLC) and polar stratospheric clouds (PSC). </p><p>The potential role of NLC as tracer for mesospheric processes and variability, and as a tool for monitoring this remote and inaccessible region, has generated substantial interest within the scientific community. The nucleation of ice in such a dry environment is not trivial. Supersaturation is considered too low for homogeneous nucleation. Hence, pre-existing condensation nuclei are deemed necessary, with smoke particles having long been considered the most likely candidate. Here we show that the atmospheric circulation transports meteoric smoke particles away from the polar region before they coagulate large enough to efficiently act as ice condensation nuclei. We also show that the charging of meteoric smoke, in combination with deviations from the mean thermal state, may solve this dilemma by significantly altering the ice nucleation properties of smoke. Thus, while it is highly questionable whether neutral smoke can provide sufficient amounts of condensation nuclei for ice formation at the polar summer mesopause, charged meteoric smoke proves to be a promising candidate to explain mesospheric ice phenomena as we observe them.</p><p> We further show that the bulk of the meteoric material is transported to the Arctic winter stratosphere, yielding significantly higher concentrations of meteoric smoke in the region of PSC nucleation than has previously been believed. Our new predictions of meteoric smoke in this region may thus shed new light on open questions relating to PSC nucleation.</p>

Atmospheric particles are ubiquitous in the Earth’s atmosphere and have potential to influence atmospheric chemistry, visibility, global climate and human health, particularly downwind from major pollution sources. The main objective of this thesis was to investigate questions pertaining to the microphysical, chemical and optical properties of aerosol particles by using in situ data collected during four experiments carried out in different regions of the Northern Hemisphere. The first two papers of this thesis reports on airborne measurements of the aerosol optical properties performed over the North Atlantic and the Los Angeles basin. Airmasses from Europe and North Africa are usually advected in over the North Atlantic, alternating with the background marine conditions. The results showed that the aerosols are not uniformly distributed in the area and variability in the aerosol fields occurs at sub-synoptic scales. It was also observed that the single scattering coefficient varied as the polluted plumes aged, suggesting a relationship between this quantity and transport time. The measurements performed around the Los Angeles basin showed that the area’s complex topography and local meteorological circulations exert a strong control on the distribution of the aerosol in the basin. Large spatio-temporal gradients in the aerosol optical properties were observed along a transect flown from the shore towards the mountains. Profiles flown over sites located on the mountains displayed a stratified configuration with elevated aerosol layers. Airborne data of residual particles collected in orographic wave clouds over Scandinavia were analyzed using a single particle analysis technique. Mineral dust, organic aerosols and sea salt were the main group of particles identified. Residuals composed predominantly of mineral dust were found in glaciated clouds while organic residuals were found in liquid clouds. The results suggest that organic material may inhibit freezing and have considerable influence on supercooled clouds that form through heterogeneous pathways. The partitioning of the aerosol particles between cloud droplets and interstitial air has been addressed in terms of their microphysical properties using data obtained at a mountain-top site in Sweden during a stratocumulus event. The results showed that the scavenging efficiency varied during the cloud event, and Aitken-mode particles were also efficiently scavenged in addition to accumulation-mode particles. It is hypothesized that alterations of the aerosol chemical composition occurred during the measurement period, modifying the hygroscopic nature of the particles and decreasing their activation diameter.

This thesis concerns the fate of the meteoric smoke in the Middle Atmosphere, and its effect on ice phenomena such as noctilucent clouds (NLC) and polar stratospheric clouds (PSC). The potential role of NLC as tracer for mesospheric processes and variability, and as a tool for monitoring this remote and inaccessible region, has generated substantial interest within the scientific community. The nucleation of ice in such a dry environment is not trivial. Supersaturation is considered too low for homogeneous nucleation. Hence, pre-existing condensation nuclei are deemed necessary, with smoke particles having long been considered the most likely candidate. Here we show that the atmospheric circulation transports meteoric smoke particles away from the polar region before they coagulate large enough to efficiently act as ice condensation nuclei. We also show that the charging of meteoric smoke, in combination with deviations from the mean thermal state, may solve this dilemma by significantly altering the ice nucleation properties of smoke. Thus, while it is highly questionable whether neutral smoke can provide sufficient amounts of condensation nuclei for ice formation at the polar summer mesopause, charged meteoric smoke proves to be a promising candidate to explain mesospheric ice phenomena as we observe them. We further show that the bulk of the meteoric material is transported to the Arctic winter stratosphere, yielding significantly higher concentrations of meteoric smoke in the region of PSC nucleation than has previously been believed. Our new predictions of meteoric smoke in this region may thus shed new light on open questions relating to PSC nucleation.

The Lagrangian trajectory code TRACMASS is extended to the atmosphere to examine the tropi- cal Hadley Cells using fields from the ERA-Interim reanalysis dataset. The analysis is made using both pressure, temperature and specific humidity as vertical coordinates. By letting a trajectory represent a mass transport and tracing millions of trajectories in a domain between the latitudes 15°N and 15°S, the mass stream function based on trajectories is obtained (Lagrangian stream function). By separating the trajectories into classes depending on their starting point and des- tination (“North-to-North”, “North-to-South”, “South-to-North” and “South-to-South”), the mass stream function is decomposed into four paths. This can not be done if the stream function is cal- culated directly from the velocity fields (Eulerian stream function). Using this technique, the mass transports recirculating within the cells are compared to the mass transports between the cells, giving further insight to the structure of the Hadley Circulations. The magnitudes of the mass stream functions are presented by converting the volume flux unit Sverdrup into a mass flux unit. It is found that the recirculating transports of the northern and southern cells are 473 Sv and 508 Sv respectively. The inter-hemispheric mass transports are 126 Sv northward and 125 Sv southward. It is also found that far from all trajectories follow paths sim- ilar to the stream lines, since the stream lines are zonal and temporal means and the particle trajectories chaotic.

Polar Mesosphere Summer Echoes (PMSE) are strong radar echoes observed from altitudes of 80-90 km in polar regions, during summer time. PMSE are closely related to the fascinating atmospheric phenomenon known as noctilucent clouds (NLC). Since it has been suspected that NLC could respond to climate change in the mesosphere, they have attracted considerable interest in the scientific community during recent years. However, continuous visual or photographic NLC observations suffer from weather restrictions and the human factor. In contrast, PMSE radar measurements can easily be made over a long interval and are very attractive for long-term studies of the atmospheric parameters at the polar mesopause. This thesis uses the world’s longest data set of PMSE observations made by the same radar at the same place. Since 1997 these measurements have been carried out with the 52 MHz ESRAD MST radar located near Kiruna in Northern Sweden. The data set for 1997-2008 has been used for studies of diurnal, day-to-day and year-to-year variations of PMSE. We showed that PMSE occurrence rate and volume reflectivity on a daily scale show predominantly semidiurnal variations with the shape of the diurnal curves remaining consistent from year to year. We found that day-to-day and inter-annual variations of PMSE correlate with geomagnetic activity while they do not correlate with mesopause temperature or solar activity. We did not find any statistically significant trends in PMSE occurrence rate and length of PMSE season over 1997-2008. The thesis also presents also a new, independent calibration method, which can be used to estimate changes in transmitter output and antenna feed losses from year to year (for example due to changes of antenna configuration) and allows making accurate calculations of PMSE strength. This method is based on radar-radiosonde comparisons in the upper troposphere/lower stratosphere region simultaneously with PMSE observations. Using this calibration we calculated the distribution of PMSE strength over magnitudes; it varies from year to year with the peak of the distribution varying from 2×10−15 to 3×10−14 m−1. We found that inter-annual variations of PMSE volume reflectivity strongly correlate with the local geomagnetic k-index and anticorrelate with solar 10.7 cm flux. We did not identify any significant trend in PMSE volume reflectivity over 1997–2009. Finally, using 11 years of measurements, we calculated in-beam the PMSE aspect sensitivities using the FCA technique. We showed that half of PMSE detected each year cannot be explained by isotropic turbulence since they are highly aspect sensitive echoes. The distribution of these echoes remains consistent from year to year with median values of aspect sensitivity from 2.9 to 3.7°. The remaining half of the PMSE have aspect sensitivity parameters larger than 9-11°. We found that PMSE aspect sensitivity has altitude dependence: the scatter becomes more isotropic with increasing height. We did not identify any dependence of PMSE aspect sensitivity on backscattered power for any year. We analysed limitations of the in-beam and off-zenith beam methods and concluded that the former is suitable for highly aspect sensitive echoes while the latter is needed for more isotropic scatterers. / <p>Godkänd; 2011; 20110926 (marsmi); DISPUTATION Ämnesområde: Rymdteknik/Space Technology Opponent: Professor Patrick Joseph Espy, Dep of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway, Ordförande: Docent Evgenia Belova, Swedish Institute of Spaces Physics, Kiruna Tid: Måndag den 31 oktober 2011, kl 10.00 Plats: Aulan, Swedish Institute of Spaces Physics, Kiruna</p>

<p>The results presented in this PhD thesis are mainly based on measurements collected by the advanced sub-mm radiometer (SMR) aboard the Odin satellite in 2002-2007. The primary data are series of temperature and ozone profiles in the middle atmosphere up to 68 km. These data are used to estimate global properties of planetary wave propagation in both horizontal and vertical directions. As good-quality retrievals from Odin are not available above 68 km, additional data sources have been considered in order to extend coverage of planetary wave properties to higher levels. These sources are temperature observations at 85-90 km obtained by the ground-based meteor radars located in the polar region in the Northern Hemisphere in Scandinavia at Esrange and at Andenes, and in Canada at Resolute Bay and at Yellowknife. Also, the series of ozone profiles from the ground-based Kiruna mm-wave radiometer, KIMRA, are used in order to compare the wave properties in ozone fields measured globally by Odin and locally by KIMRA.</p><p>The main task of this PhD thesis is to study the 5-day planetary wave characteristics in the Earth’s atmosphere. The influence of waves on the atmospheric circulation causes, for example, substantial local departures from radiative equilibrium, observed in the winter stratosphere and close to the summer mesopause. Seasonal variations of the 5-day planetary wave properties and physical phenomena related to these variations are also studied in this thesis.</p><p>During winter, planetary waves propagate freely in the vertical direction, and maximal wave amplitudes are found in the extratropical stratosphere. The Northern Hemisphere (NH) winter periods of 2002-2003 and 2005 have been examined and a comparison has been carried out between the planetary wave properties in temperature and ozone variations. In general, the results show an expected in-phase behavior between the temperature and ozone fields in the lower stratosphere (due to dynamic effects) and an out-of-phase pattern in the upper stratosphere (which is expected as a result of photochemical effects).</p><p>Earlier theoretical and experimental studies have shown that, despite unfavourable summertime wind conditions, 5-day planetary waves can be registered not only in the stratosphere but also at higher altitudes in the mesosphere. The NH summers of 2003-2005 and 2007 have been considered and results have confirmed the existence of 5-day planetary waves up to the mesopause level (85-90 km). The results demonstrate that, for different periods, the possible source of the observed waves could be located at lower altitudes in both hemispheres with successive propagation into the summer mesosphere, or the waves could be generated in-situ as a result of the baroclinic instability of summer easterly jet.</p>

The results presented in this PhD thesis are mainly based on measurements collected by the advanced sub-mm radiometer (SMR) aboard the Odin satellite in 2002-2007. The primary data are series of temperature and ozone profiles in the middle atmosphere up to 68 km. These data are used to estimate global properties of planetary wave propagation in both horizontal and vertical directions. As good-quality retrievals from Odin are not available above 68 km, additional data sources have been considered in order to extend coverage of planetary wave properties to higher levels. These sources are temperature observations at 85-90 km obtained by the ground-based meteor radars located in the polar region in the Northern Hemisphere in Scandinavia at Esrange and at Andenes, and in Canada at Resolute Bay and at Yellowknife. Also, the series of ozone profiles from the ground-based Kiruna mm-wave radiometer, KIMRA, are used in order to compare the wave properties in ozone fields measured globally by Odin and locally by KIMRA. The main task of this PhD thesis is to study the 5-day planetary wave characteristics in the Earth’s atmosphere. The influence of waves on the atmospheric circulation causes, for example, substantial local departures from radiative equilibrium, observed in the winter stratosphere and close to the summer mesopause. Seasonal variations of the 5-day planetary wave properties and physical phenomena related to these variations are also studied in this thesis. During winter, planetary waves propagate freely in the vertical direction, and maximal wave amplitudes are found in the extratropical stratosphere. The Northern Hemisphere (NH) winter periods of 2002-2003 and 2005 have been examined and a comparison has been carried out between the planetary wave properties in temperature and ozone variations. In general, the results show an expected in-phase behavior between the temperature and ozone fields in the lower stratosphere (due to dynamic effects) and an out-of-phase pattern in the upper stratosphere (which is expected as a result of photochemical effects). Earlier theoretical and experimental studies have shown that, despite unfavourable summertime wind conditions, 5-day planetary waves can be registered not only in the stratosphere but also at higher altitudes in the mesosphere. The NH summers of 2003-2005 and 2007 have been considered and results have confirmed the existence of 5-day planetary waves up to the mesopause level (85-90 km). The results demonstrate that, for different periods, the possible source of the observed waves could be located at lower altitudes in both hemispheres with successive propagation into the summer mesosphere, or the waves could be generated in-situ as a result of the baroclinic instability of summer easterly jet.

The role of aerosols and clouds is one of the largest sources of uncertainty in understanding climate change. The primary scientific goal of this thesis is to improve the understanding of cloud-aerosol interactions by applying inverse modeling using Markov Chain Monte Carlo (MCMC) simulation. Through a set of synthetic tests using a pseudo-adiabatic cloud parcel model, it is shown that a self adaptive MCMC algorithm can efficiently find the correct optimal values of meteorological and aerosol physiochemical parameters for a specified droplet size distribution and determine the global sensitivity of these parameters. For an updraft velocity of 0.3 m s-1, a shift towards an increase in the relative importance of chemistry compared to the accumulation mode number concentration is shown to exist somewhere between marine (~75 cm-3) and rural continental (~450 cm-3) aerosol regimes. Examination of in-situ measurements from the Marine Stratus/Stratocumulus Experiment (MASE II) shows that for air masses with higher number concentrations of accumulation mode (Dp = 60-120 nm) particles (~450 cm-3), an accurate simulation of the measured droplet size distribution requires an accurate representation of the particle chemistry. The chemistry is relatively more important than the accumulation mode particle number concentration, and similar in importance to the particle mean radius. This result is somewhat at odds with current theory that suggests chemistry can be ignored in all except for the most polluted environments. Under anthropogenic influence, we must consider particle chemistry also in marine environments that may be deemed relatively clean. The MCMC algorithm can successfully reproduce the observed marine stratocumulus droplet size distributions. However, optimising towards the broadness of the measured droplet size distribution resulted in a discrepancy between the updraft velocity, and mean radius/geometric standard deviation of the accumulation mode. This suggests that we are missing a dynamical process in the pseudo-adiabatic cloud parcel model. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.

The basic issue of this thesis concerns one of the fundamental problems of the future of our society: How to meet the energy requirements for a large and growing world population while preserving our environment? This question is important for the world and the answers are complex and interwoven.Conventional energy sources, fossil and fissile, are polluting in the present and in the future: they erode the environment and their resources are limited. Renewable energy (hydro, wind, solar, geothermal) constitutes a minimum of pollution in the different energy systems. The technologies for using renewable energy are well known though further development and progress are made. This development also requires behavioural change, adaptation, and above all political will. The transition from an economy based on fossil energy to an economy based on renewable energy appears necessary for the protection of the environment. The cost of renewable energy is often represented as an obstacle but remains competitive in the long run.The development and availability of renewable energy, which varies because of its spatial and temporal distribution, require an adaptation of lifestyle, habits, habitat design (passive bioclimatic houses), urban planning and transportation.The focus of this thesis was to apply renewable energy in an area with hot summers and cold winter, a climate like that in the northwest of Algeria. In order to provide improved comfort in the buildings and also economic development in this area, the energy demand for heating and cooling was analyzed in the ancient city of Tlemcen. To supply domestic hot water and space heating, water must be simultaneously available at two different temperature levels. Cold water temperature, close to that of the atmosphere, and hot water between 50 and 60°C. An interesting feature of the preparation of hot water is the small variation of requirements during the year, unlike that to heating. The preparation of hot water is one of the preferred applications of solar energy in the building for several reasons. For this reason an experimental study of the thermal behaviour of a domestic hot water storage tank was undertaken. The phenomena that affect the thermal behaviour of tank especially the coupling between the solar collector and storage tank was studied. This study included concentrating solar collector in which optical fibers were used to transport the energy to the storage tank. Another technology was introduced and developed for the heating and cooling of buildings in the desert involving an existing ancient irrigation system called Fouggara. The novel idea is to use the Fouggara as an air conditioner by pumping ambient air through this underground system. Then air at a temperature of about 21°C would be supplied to the building for heating in the winter and cooling in the summer. This study shows the feasibility of using this ancient irrigation system of Fouggara and contributes to reducing and eliminating the energy demand for heating and cooling buildings in the Sahara desert. / <p>Godkänd; 2011; 20110920 (sofama)</p>