| 1. |
- Broman, Lina, 1981-, et al.
(författare)
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Case study of a large mesospheric front in polar mesospheric clouds
- 2022
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Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 74:1, s. 85-105
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Tidskriftsartikel (refereegranskat)abstract
- A large mesospheric front structure was observed on 16 July 2010 in Polar Mesospheric Clouds using common volume observations performed by the Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument and the Odin Optical Spectrograph and Infrared Imager System (OSIRIS) at ∼ 75◦ N, 144◦ E. During the 4.5 hours long observation time, the front structure manifested in the PMC layer as an ice free elongated structure with sharp edges to the surrounding cloud field. A propagation direction from Southeast to Northwest and simultaneous clockwise rotation of 12 deg/hour is observed and the horizontal extent of the structure is found to be about 1800 km long and 190 km wide. Common volume observations of the mesospheric environment in terms of temperatures and water vapor provided by the Odin Sub-Millimetre Radiometer (SMR) indicate an extensive elevated warm air mass during the occurrence of the front structure and colder temperatures at the sharp front edge. The presence of a wave structure with λz ∼ 6 km at an altitude of 70-90 km coincides with a sharpening of the front edge. We compare the general characteristics of the current mesospheric front to earlier reports on mesospheric fronts based on ground-based and space-borne airglow and PMC observations.
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| 2. |
- Broman, Lina, et al.
(författare)
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Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging
- 2019
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:19, s. 12455-12475
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Tidskriftsartikel (refereegranskat)abstract
- 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 d for the years 2010 and 2011 and the latitude range 78 to 80 degrees 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 min, our method enables a detailed comparison of PMC regions of varying brightness and IWC. However, since the dataset is limited to 18 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 -CIPS) is 3.4 x 10(-6) sr(-1) (+/- 2.9x 10(-6) sr(-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 -22 g km(-2) (+/- 14 g km(-2)) on average.
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| 3. |
- Broman, Lina, 1981-, et al.
(författare)
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Hemispheric comparison of polar mesospheric cloud structures and microphysics using the Odin satellite tomographic dataset
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Satellite-based tomography provides a new approach to studying Polar Mesospheric Clouds (PMCs). In this paper, we explore the tomographic dataset from the Odin satellite to study structures and microphysics of PMCs. The dataset is based on special limb scans over limited altitude ranges during 256 orbits in the years 2010-2014. The focus of the analysis is on latitudinal and hemispheric variation. The basic results are in line with earlier studies by lidars and conventional satellite limb measurements. We find a decrease with decreasing latitude of PMC occurrence frequency, brightness, ice water content and particle size. As for hemispheric differences, we find that occurrence frequency, brightness, ice water content and particle size are generally less in the Southern Hemisphere than in the Northern Hemisphere. Our limited Southern Hemisphere dataset does not show the general finding of lidar studies that PMCs in the South occur at higher altitudes than in the North. All data products show substantial diurnal variations, likely connected to tidal activity. As a basic microphysical parameter, the altitude gradient of the PMC particle size does not show any significant latitudinal or hemispheric dependence. This suggests a PMC growth/sedimentation process that is largely the same everywhere. The data presented here demonstrate the value of satellite-based tomography as a complement to lidars and conventional satellite measurements by providing global coverage in combination with both vertical and horizontal resolution.
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| 4. |
- Broman, Lina, 1981-
(författare)
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Multi-satellite views on mesospheric microphysics and dynamics
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Broman, Lina, 1981-, et al.
(författare)
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New insights on polar mesospheric cloud particle size distributions from a two-satellite common volume study
- 2021
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 219
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Tidskriftsartikel (refereegranskat)abstract
- 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◦ N to 80◦ 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.
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| 6. |
- Ge, ShuCan, et al.
(författare)
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Characteristic analysis of layered PMSEs measured with different elevation angles at VHF based on an experimental case
- 2021
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Ingår i: Earth and Planetary Physics. - : Earth and Planetary Physics. - 2096-3955. ; 5:1, s. 42-51
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Tidskriftsartikel (refereegranskat)abstract
- Polar Mesosphere Summer Echoes (PMSEs) are very strong radar echoes observed at altitudes near the polar summer mesopause. One of the essential properties of these radar echoes is that they can give useful diagnostic information about the physics of the scattering process. In this paper, the related characteristics of PMSEs measured with the European Incoherent SCATter Very High Frequency (EISCAT VHF) 224 MHz radar on 13-15 July 2010 are studied at different elevation angles from 78 degrees to 90 degrees. It is found that the PMSEs peak power and strongest PMSEs average power occur at the same elevation angles. Also interesting is that the strongest PMSEs occur at off-vertical angles when a PMSEs has a layered (multilayer) structure. And reflection may have more significant effects on PMSEs when there are double or multilayer PMSEs. Possible explanations regarding these observations are discussed.
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| 7. |
- Hogenkamp, Pleunie S, et al.
(författare)
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Acute sleep deprivation increases portion size and affects food choice in young men.
- 2013
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Ingår i: Psychoneuroendocrinology. - : Elsevier BV. - 1873-3360 .- 0306-4530. ; 38:9, s. 1668-1674
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Tidskriftsartikel (refereegranskat)abstract
- Acute 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/m(2)) 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.
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| 8. |
- Stigsdotter-Broman, Lina, et al.
(författare)
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Long-term follow-up after callosotomy : A prospective, population based, observational study
- 2014
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Ingår i: Epilepsia. - : Wiley. - 0013-9580 .- 1528-1167. ; 55:2, s. 316-321
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveAnalyze the long-term outcome of callosotomies with regard to seizure types and frequencies and antiepileptic drug treatment.MethodsThis 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.ResultsThe 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 >75%. At long-term follow-up, four were off medication. Only one of the 31 patients had no neurologic impairment.SignificanceThe 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.
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