New insights on polar mesospheric cloud particle size distributions from a two-satellite common volume study

The particle size distribution of Polar Mesospheric Clouds (PMC) is closely related to the fundamental processes of cloud formation and evolution. Still, despite substantial observational efforts, specific details about the particle size distribution have remained obscure. In this study, we aim at deriving more constraints on PMC size distributions by combining optical measurements from two satellite instruments observing a common PMC volume. We use a special set of 2D tomographic limb observations from the Optical Spectrograph and Infrared Imager System (OSIRIS) on the Odin satellite from 2010 to 2011 in the latitude range 78\ub0 N to 80\ub0 N and compare these to simultaneous PMC observations from the nadir-viewing Cloud Imaging and Particle Size (CIPS) instrument on the AIM satellite. A key goal is to find the assumption on the mathematical shape of the particle size distribution that should be applied to a vertically resolving limb-viewing instrument to reach consistent size results compared to the column-integrated ice distribution as seen by a nadir-viewing instrument. Our results demonstrate that viewing geometry and sampling volume of each instrument must be carefully considered and that the same size distribution assumption cannot simultaneously describe a column-integrated and a local height-resolved size distribution. In particular, applying the standard Gaussian assumption, used by many earlier PMC studies, to both limb and nadir observation leads to an overestimate of particle sizes seen by OSIRIS by about 10 nm as compared to CIPS. We show that the agreement can be improved if a Log-normal assumption with a broad distribution width around σ = 1.42 is adopted for OSIRIS. A reason for this broad distribution best describing the OSIRIS observations we suggest the large retrieval volume of the limb measurement. Gravity waves and other small-scale processes can cause horizontal variations and a co-existence of a wide range of particle populations in the sampling volume. Horizontal integration then leads to apparently much broader size distributions than encountered in a small horizontal sampling volume

Managing Intra-Party Democracy: Comparing the French Socialist and British Labour Party Conferences

The French Socialists and British Labour consider intra-party democracy as a central tenet of their philosophies. It is a core value that orientates their political attitudes and defines their identity. Traditionally, they have privileged a particular type of decision-making, based on the sovereignty of the party conference. However, at the beginning of the 1990s, these meetings projected a damaging image of division and chaos. Confronted with the intense scrutiny of their internal debates by the media, the two parties had to find a better balance between their culture and practices, and the need to promote an image of unity and efficiency. They introduced a number of reforms that, they claim, have expanded the possibilities for individual members to participate while at the same time giving the two leaderships a firmer grip on decision-making. Based on qualitative research conducted over many years, this paper explores the parties' new attitudes to internal democracy and analyses the process of power redistribution within the organizations

Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging

Two important approaches for satellite studies of polar mesospheric clouds (PMCs) are nadir measurements adapting phase function analysis and limb measurements adapting spectroscopic analysis. Combining both approaches enables new studies of cloud structures and microphysical processes but is complicated by differences in scattering conditions, observation geometry and sensitivity. In this study, we compare common volume PMC observations from the nadir-viewing Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite and a special set of tomographic limb observations from the Optical Spectrograph and InfraRed Imager System (OSIRIS) on the Odin satellite performed over 18&thinsp;d for the years 2010 and 2011 and the latitude range 78 to 80∘&thinsp;N. While CIPS provides preeminent horizontal resolution, the OSIRIS tomographic analysis provides combined horizontal and vertical PMC information. This first direct comparison is an important step towards co-analysing CIPS and OSIRIS data, aiming at unprecedented insights into horizontal and vertical cloud processes. Important scientific questions on how the PMC life cycle is affected by changes in humidity and temperature due to atmospheric gravity waves, planetary waves and tides can be addressed by combining PMC observations in multiple dimensions. Two- and three-dimensional cloud structures simultaneously observed by CIPS and tomographic OSIRIS provide a useful tool for studies of cloud growth and sublimation. Moreover, the combined CIPS/tomographic OSIRIS dataset can be used for studies of even more fundamental character, such as the question of the assumption of the PMC particle size distribution. We perform the first thorough error characterization of OSIRIS tomographic cloud brightness and cloud ice water content (IWC). We establish a consistent method for comparing cloud properties from limb tomography and nadir observations, accounting for differences in scattering conditions, resolution and sensitivity. Based on an extensive common volume and a temporal coincidence criterion of only 5&thinsp;min, our method enables a detailed comparison of PMC regions of varying brightness and IWC. However, since the dataset is limited to 18&thinsp;d of observations this study does not include a comparison of cloud frequency. The cloud properties of the OSIRIS tomographic dataset are vertically resolved, while the cloud properties of the CIPS dataset is vertically integrated. To make these different quantities comparable, the OSIRIS tomographic cloud properties cloud scattering coefficient and ice mass density (IMD) have been integrated over the vertical extent of the cloud to form cloud albedo and IWC of the same quantity as CIPS cloud products. We find that the OSIRIS albedo (obtained from the vertical integration of the primary OSIRIS tomography product, cloud scattering coefficient) shows very good agreement with the primary CIPS product, cloud albedo, with a correlation coefficient of 0.96. However, OSIRIS systematically reports brighter clouds than CIPS and the bias between the instruments (OSIRIS &ndash; CIPS) is 3.4&times;10&minus;6 &thinsp;sr&minus;1 (&plusmn;2.9&times;10&minus;6&thinsp;sr&minus;1) on average. The OSIRIS tomography IWC (obtained from the vertical integration of IMD) agrees well with the CIPS IWC, with a correlation coefficient of 0.91. However, the IWC reported by OSIRIS is lower than CIPS, and we quantify the bias to &minus;22&thinsp;g&thinsp;km&minus;2 (&plusmn;14&thinsp;g&thinsp;km&minus;2) on average.</p

Acute sleep deprivation increases portion size and affects food choice in young men

SummaryAcute sleep loss increases food intake in adults. However, little is known about the influence of acute sleep loss on portion size choice, and whether this depends on both hunger state and the type of food (snack or meal item) offered to an individual. The aim of the current study was to compare portion size choice after a night of sleep and a period of nocturnal wakefulness (a condition experienced by night-shift workers, e.g. physicians and nurses). Sixteen men (age: 23±0.9 years, BMI: 23.6±0.6kg/m2) participated in a randomized within-subject design with two conditions, 8-h of sleep and total sleep deprivation (TSD). In the morning following sleep interventions, portion size, comprising meal and snack items, was measured using a computer-based task, in both fasted and sated state. In addition, hunger as well as plasma levels of ghrelin were measured. In the morning after TSD, subjects had increased plasma ghrelin levels (13%, p=0.04), and chose larger portions (14%, p=0.02), irrespective of the type of food, as compared to the sleep condition. Self-reported hunger was also enhanced (p<0.01). Following breakfast, sleep-deprived subjects chose larger portions of snacks (16%, p=0.02), whereas the selection of meal items did not differ between the sleep interventions (6%, p=0.13). Our results suggest that overeating in the morning after sleep loss is driven by both homeostatic and hedonic factors. Further, they show that portion size choice after sleep loss depend on both an individual's hunger status, and the type of food offered

The Abisko Polar Prediction School

Polar regions are experiencing rapid climate change, faster than elsewhere on Earth with consequences for the weather and sea ice. This change is opening up new possibilities for businesses such as tourism, shipping, fisheries and oil and gas extraction, but also bringing new risks to delicate polar environments. Effective weather and climate prediction is essential to managing these risks, however our ability to forecast polar environmental conditions over periods from days to decades ahead falls far behind our abilities in the mid-latitudes. In order to meet the growing societal need for young scientists trained in this area, a Polar Prediction School for early career scientists from around the world was held in April 2016

Multi-satellite views on mesospheric microphysics and dynamics

Atmospheric gravity waves of different scales and origins strongly modulate the wind field and temperature structure of the higher parts of the atmosphere. Direct and continuous measurements of these processes are particularly complicated in the mesosphere at about 50 to 100 km height due to the remote location of this region. Polar mesospheric clouds (PMCs) that form in the summertime between 80 and 90 km over the polar regions are highly sensitive to changes in the background atmosphere, and in particular to waves. This makes them an ideal tracer for atmospheric conditions and wave activity. However, in order to use them as a tracer, we need to better understand the influence of waves on the clouds on a local scale. In this thesis, tomographic measurements from the limb viewing OSIRIS spectrograph on the Swedish Odin satellite are used to study 2D structures of PMCs. The aim is to improve our understanding of the clouds’ life cycle and of their interactions with waves and dynamics on different scales.  First, a method is developed that combines the tomographic PMC measurements from the OSIRIS instrument with simultaneous measurements from the downward viewing CIPS instrument on NASA’s AIM satellite. The method allows studies of clouds in a common observational volume with a combined high vertical and horizontal resolution of cloud structures. Measurements of cloud brightness and ice content from the two instruments agree very well, and it is demonstrated that the combined dataset is well suited for studies of cloud structures and cloud microphysics.  The combined dataset is further investigated to study assumptions on the particle size distribution of PMCs. We find that the commonly used Gaussian assumption cannot simultaneously describe the size distribution as seen by a column-integrating instrument (CIPS) and by a limb-integrating instrument (OSIRIS). Instead, we show that the particle population seen by a limb-integrating instrument is better represented by a broad lognormal distribution.  In an atmospheric case study, the combined PMC dataset is used together  with simultaneous temperature and water vapor measurements from the SMR instrument on Odin to study a special event of a mesospheric front structure. We characterize the temporal and structural development of the front as seen by both satellites and discuss possible generating mechanisms. Finally, we extend OSIRIS’ tomographic view to the southern hemisphere. The structure and dynamics of the atmosphere are not symmetric, but hemispheric differences in Earth’s topography cause differences in wind systems at all atmospheric altitudes. We therefore apply the tomographic approach to study differences between the northern and southern hemispheres in PMC morphology and microphysics. 

Studier av turbulenta rörelser i städmoln medhjälp av numeriska simuleringar av tropisk konvektion

Identifying the dynamical processes that are active in tropical cirrus clouds is important for understanding the role of cirrus in the tropical atmosphere. This study focuses on analyzing turbulent motions inside tropical anvil cirrus with the use of a Cloud Resolving Model. Convection in the transition from shallow to deep convection has been simulated with Colorado State University Large Eddy Simulator/Cloud Resolving Model System for Atmospheric Model (SAM 6.3) in a high resolution three-dimensional simulation and anvil cirrus formed in the end of this simulation has been analyzed. For model set up, data gathered during the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM LBA) field experiment in Amazonas, Brazil have been used as large scale forcing. 31 anvil clouds have been localized from a single time step of the simulation, “a snapshot”, of the entire simulated cloud field consisting of convective clouds of different scales and subsequently divided into three categories that represent different stages of the anvil lifetime; growing, mature and dissipating anvil stages. The classification is based on in-cloud properties such as cloud condensate content and vertical velocities. The simulated anvils have been analyzed both individually and as groups to examine the transition from isotropic three-dimensional turbulence in the convective core of the thunderstorm to stratified two-dimensional turbulence in the anvil outflow. A dimensionless number F is derived and used as a measure of the “isotropic” behavior of the turbulence inside the cloud. F is expressed as the ratio between the horizontal part of TKE and the total (horizontal + vertical) Experiments show that SAM 6.3 clearly can resolve turbulent structures and that the transition from isotropic three-dimensional turbulence to stratified two-dimensional turbulence occurs in the middle layers of the mature and dissipating anvil stages.Sammanfattning av ”Studier av turbulenta rörelser i städmoln med hjälp av numeriska simuleringar av tropisk konvektion”  Städmoln i tropikerna har stor inverkan på strålningsballansen på grund av de är så vanligt förekommande och att de ligger på hög höjd i atmosfären. Att förstå de drivande krafterna som är aktiva i skapandet och underhållandet av städmoln är viktiga för att få en bra bild av rollen städmoln spelar i den tropiska atmosfären. Den här uppsatsen fokuserar på att studera turbulenta rörelser inuti tropiska städmoln med hjälp av en molnmodell. Tropisk konvektion har simulerats med Colorado State University’s molnmodell SAM 6.3 i en högupplöst tredimensionell simulering. Data från en ”ögonblicksbild” av det simulerade molnfältet har analyserats och 31 städmoln har valts ut och studerats vidare. De simulerade städmolnen indelades i tre olika kategorier baserat på utvecklingsstadier; växande städmoln, moget städmoln och skingrade städmoln. Stadieklassificeringen bestämdes beroende på isvatteninnehåll och vertikalhastigheter i molnet. Städmolnen har därefter analyserats både individuellt och som grupper för att lokalisera och analysera övergången från tredimensionell isotropisk turbulens i kärnan av Cb-molnet till tvådimensionell stratifierad turbulens i städmolnet. För att initiera simuleringen användes mätdata insamlade under fältexperimentet TRMM LBA (Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere) i Amazonas, Brasilien. För att beskriva turbulenta rörelser i molnen togs det dimensionslösa talet fram som ett mått på isotropin. uttrycks som kvoten mellan den horisontella delen av TKE och den totala (horisontell och vertikal). Den här studien visar att den undersökta molnmodellen SAM 6.3 klart kan simulera turbulenta i rörelser i övergången mellan isotropisk till horisontell turbulens i olika stadier av städmolnens livscykel. Mina analyser visar att övergången sker främst i de mellersta skikten av de mogna och skingrade stadierna av städmolnets utveckling

Long-term follow-up after callosotomy : A prospective, population based, observational study

Objective Analyze the long-term outcome of callosotomies with regard to seizure types and frequencies and antiepileptic drug treatment. Methods This longitudinal observational study is based on data from the prospective Swedish National Epilepsy Surgery Register. Thirty-one patients had undergone callosotomy in Sweden 1995-2007 and had been followed for 2 and 5 or 10years after surgery. Data on their seizure types and frequencies, associated impairments, and use of antiepileptic drugs have been analyzed. Results The median total number of seizures per patient and month was reduced from 195 before surgery to 110 twoyears after surgery and 90 at the long-term follow-up (5 or 10years). The corresponding figures for drop attacks (tonic or atonic) were 190 before surgery, 100 2years after surgery, and 20 at the long-term follow-up. Ten (56%) of the 18 patients with drop attacks were free from drop attacks at long-term follow-up. Three of the remaining eight patients had a reduction of &gt;75%. At long-term follow-up, four were off medication. Only one of the 31 patients had no neurologic impairment. Significance The present population-based, prospective observational study shows that the corpus callosotomy reduces seizure frequency effectively and sustainably over the years. Most improvement was seen in drop attacks. The improvement in seizure frequency over time shown in this study suggests that callosotomy should be considered at an early age in children with intractable epilepsy and traumatizing drop attacks