An exceptionally strong stationary planetary wave with Zonal Wavenumber 1 led to a sudden stratospheric warming (SSW) in the Southern Hemisphere in September 2019. Ionospheric data from European ...Space Agency's Swarm satellite constellation mission show prominent 6‐day variations in the dayside low‐latitude region at this time, which can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi‐6‐day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard National Aeronautics and Space Administration's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere during the SSW, which is one of the strongest in the record. The Q6DW is apparently generated in the polar stratosphere at 30–40 km, where the atmosphere is unstable due to strong vertical wind shear connected with planetary wave breaking. These results suggest that an Antarctic SSW can lead to ionospheric variability through wave forcing from the middle atmosphere.
Plain Language Summary
A sudden stratospheric warming (SSW) is an extreme wintertime polar meteorological phenomenon occurring mostly over the Arctic region. Studies have shown that Arctic SSW can influence the entire atmosphere. In September 2019, a rare SSW event occurred in the Antarctic region, providing an opportunity to investigate its broader impact on the whole atmosphere. We present observations from the middle atmosphere and ionosphere during this event, noting unusually strong wave activity throughout this region. Our results suggest that an Antarctic SSW can have a significant impact on the whole atmosphere system similar to those due to Arctic events.
Key Points
An Antarctic sudden stratospheric warming (SSW) occurred in September 2019
Swarm observations reveal prominent 6‐day variations in the dayside low‐latitude ionosphere
A burst of quasi‐6‐day wave activity is observed in the middle atmosphere during the SSW
The Brewer-Dobson circulation (mainly meridional circulation) is very important for stratospheric ozone dynamics and thus for the overall state of the stratosphere. There are some indications that ...the meridional circulation in the stratosphere could be longitudinally dependent, which would have an impact on the ozone distribution. Therefore, we analyse here the meridional component of the stratospheric wind at northern middle latitudes to study its longitudinal dependence. The analysis is based on the NCEP/NCAR-1 (National Centers for Environmental Prediction and the National Center for Atmospheric Research), MERRA (Modern Era-Retrospective Analysis) and ERA-Interim (European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis Interim) reanalysis data. The well-developed two-core structure of strong but opposite meridional winds, one in each hemisphere at 10 hPa at higher northern middle latitudes, and a less pronounced five-core structure at 100 hPa are identified. In the central areas of the two-core structure the meridional and zonal wind magnitudes are comparable. The two-core structure at 10 hPa is almost identical for all three different reanalysis data sets in spite of the different time periods covered. The two-core structure is not associated with tides. However, the two-core structure at the 10 hPa level is related to the Aleutian pressure high at 10 hPa. Zonal wind, temperature and the ozone mixing ratio at 10 hPa also exhibit the effect of the Aleutian high, which thus affects all parameters of the Northern Hemisphere middle stratosphere. Long-term trends in the meridional wind in the "core" areas are significant at the 99% level. Trends of meridional winds are negative during the period of ozone depletion development (1970-1995), while they are positive after the ozone trend turnaround (1996-2012). Meridional wind trends are independent of the sudden stratospheric warming (SSW) occurrence and the quasi-biennial oscillation (QBO) phase. The influence of the 11-year solar cycle on stratospheric winds has been identified only during the west phase of QBO. The well-developed two-core structure in the meridional wind illustrates the limitations of application of the zonal mean concept in studying stratospheric circulation.
Novel temperature sensors with unique optical properties, based on 4-alkylbenzoic acid developers (CnBA, where
n
is the number of carbon atoms in the alkyl chain ranging from 4 to 6), which exhibit a ...liquid crystalline phase, and 6′-(diethylamino)-1′,2′-benzofluoran (BF) leuco dye are reported. The main aim of this work is to investigate how the molecular packing of CnBA in different phases affects the development of BF. Various techniques were used to study the prepared temperature sensors' phase transitions and thermal stability. The spectroscopic properties of BF : CnBA (1 : 3) were investigated, using temperature-dependent UV-Vis absorption and emission spectroscopy, and the results show that the sensors demonstrate reversible color-changing properties. When the CnBA developers are at room temperature, the materials are pink and emit orange light, while at approximately 105 °C they turn white and emit yellow light. Above that temperature, the sensors return to a pink and orange light emission. Therefore the prepared materials can serve as indicators that inform about not only exceeding a certain temperature threshold but also reaching temperature ranges.
CnBA liquid crystals (
n
= 4, 5, 6) were utilized as color developers of BF leuco dye in novel thermochromic sensors, which exhibit a reversible, temperature-dependent shift in both observed and emission colors.
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•Pure phase Nd3+-LuPO4 nanoscale optical materials were fabricated using two different protocols of synthesis: hydrothermal and microwave.•The novelty of the synthesis concerned using ...choline+H2PO4− ionic liquid as morphology controlling agent.•The structural and spectroscopic properties of the obtained materials differing in morphology and grain size were investigated and the possible application of this material as an optical thermometer was studied.•Due to the close relation between the spectroscopic properties and the local structure and the bonding at the ion site, the Nd3+ ion was used as a probe for local ordering.
LuPO4 in the form of nano-powders can find potential application in bio-imaging and luminescence thermometry. To enable development of functional materials there is a need to acquire basic information about the effect of morphology and grain size on spectroscopic properties. So, we investigated a series of Nd3+-doped LuPO4 nanoparticles prepared with task-specific ionic liquid as the reactant and in-situ stabilizer. Thus, fast and facile preparation of the desired well-crystallized single-phase phosphate nanomaterials was possible. The XRD patterns and TEM analysis revealed the influence of the synthesis conditions on the morphology and nanoparticles size, which is reflected in their spectroscopic properties. Low-temperature high-resolution techniques i.e. absorption spectroscopy at 4.2 K and laser site-selective spectroscopy at 77 K with Nd3+ ion as structural probe were used. Micro-powdered Nd3+-doped LuPO4 obtained by a solid-state reaction was applied as a reference. The possible application of this material as an optical thermometer was considered.
Reanalysis data are very useful for studying the stratosphere. They can be used for analysis of long-term trends (temperature, wind speed, humidity, etc.) or analysis of global atmospheric dynamics, ...etc. There are various reanalysis projects that provide outputs which are not identical. In this paper, we mutually compare three of them, ERA-40, ERA-Interim and NCEP/NCAR, and compare them with balloon radiosonde observations from Prague, Port Hardy and Valentia stations. This comparison is done for wind speed and direction at pressure levels 100 and 10 hPa and for various periods between 1957 and 2009. The results show that the differences between reanalysis vary. Wind speed data from all three analyses reasonably agree except for the 10 hPa historical data before 1966 and particularly ERA-40 data at the end of the data series (1998–2001). The quality of the ERA-40 10 hPa stratospheric wind data has been proven to be substantially worse over the last four ERA-40 years of 1998–2001 (2002) compared to previous years, both in wind speed and wind direction. The reanalysis data results are compared with radiosonde observations from Prague, Port Hardy and Valentia stations at 10 hPa for the months of February between 1989 and 2009. The results show that there are sometimes surprisingly large differences, more for ERA-Interim versus Prague measurements. Differences in wind direction greater than 45° (outliers) between the reanalysis data and Prague observations in wind direction occur in Februaries predominantly when winds in Prague are in "minor" sectors, such as north, northeast and east (easterlies), whereas "major" sectors, particularly the dominant W (westerlies) wind sector, exhibit almost no outliers.
Summary
This article presents a method that allows for reliable automated image acquisition of specimens with high information content in light microscopy with emphasis on fluorescence microscopy ...applications. Automated microscopy typically relies on autofocusing used for the analysis of information content behaviour along the z‐axis within each field of view. However, in the case of a field of view containing more objects that do not lie precisely in one z‐plane, traditional autofocusing methods fail due to their principle of operation. We avoid this issue by reducing the original problem to a set of simple and performable tasks: we divide the field of view into a small number of tiles and process each of them individually. The obtained results enable discovering z‐planes with rich information content that remain hidden during global analysis of the whole field of view. Our approach therefore outperforms other acquisition methods including the manual one. A large part of the contribution is oriented towards practical application.
We present a new algorithm to analyse information content in images acquired using automated fluorescence microscopy. The algorithm belongs to the group of autofocusing methods, but differs from its ...predecessors in that it can handle thick specimens and operate also in confocal mode. It measures the information content in images using a 'content function', which is essentially the same concept as a focus function. Unlike previously presented algorithms, this algorithm tries to find all significant axial positions in cases where the content function applied to real data is not unimodal, which is often the case. This requirement precludes using algorithms that rely on unimodality. Moreover, choosing a content function requires careful consideration, because some functions suppress local maxima. First, we test 19 content functions and evaluate their ability to show local maxima clearly. The results show that only six content functions succeed. To save time, the acquisition procedure needs to vary the step size adaptively, because a wide range of possible axial positions has to be passed so as not to miss a local maximum. The algorithm therefore has to assess the steepness of the content function online so that it can decide to use a bigger or smaller step size to acquire the next image. Therefore, the algorithm needs to know about typical behaviour of content functions. We show that for normalized variance, one of the most promising content functions, this knowledge can be obtained after normalizing with respect to the theoretical maximum of this function, and using hierarchical clustering. The resulting algorithm is more reliable and efficient than a simple procedure with constant steps.
Even the best optical microscopes available on the market exhibit chromatic aberrations to some extent. In some types of study, chromatic aberrations of current optics cannot be neglected and a ...software correction is highly desirable. This paper describes a novel method of chromatic aberration measurement and software correction using sub‐resolution bead imaging and computer image analysis. The method is quick, precise and enables the determination of both longitudinal and lateral chromatic aberrations. Correction function can be computed in about half an hour, including image acquisition. Using this approach, chromatic aberrations can be reduced to 10–20 nm laterally and 10–60 nm axially depending on the type of optical set‐up. The method is especially suitable for fluorescence microscopy, where a limited number of wavelengths are observed.
Using dual-color fluorescence in situ hybridization (FISH) combined with two-dimensional (2D) image analysis, the locations of ABL and BCR genes in cell nuclei were studied. The center of ...nucleus-to-gene and mutual distances of ABL and BCR genes in interphase nuclei of nonstimulated and stimulated lymphocytes as well as in lymphocytes stimulated after irradiation were determined. We found that, after stimulation, the ABL and BCR genes move towards the membrane, their mutual distances increase, and the shortest distance between heterologous ABLand BCRgenes increases. The distribution of the shortest distances between ABL and BCRgenes in the G0 phase of lymphocytes corresponds to the theoretical distribution calculated by the Monte-Carlo simulation. Interestingly, the shortest ABL-BCR distances in G1 and S(G2 ) nuclei are greater in experiment as compared with theory. This result suggests the existence of a certain regularity in the gene arrangement in the G1 and S(G2 ) nuclei that keeps ABL and BCR genes at longer than random distances. On the other hand, in about 2% to 8% of lymphocytes, the ABL and BCR genes are very close to each other (the distance is less than ∼0.2 to 0.3 μm). For comparison, we studied another pair of genes, c-MYC and IgH, that are critical for the induction of t(8; 14) translocation that occurs in the Burkitt's lymphoma. We found that in about 8% of lymphocytes, c-MYC and IgH are very close to each other. Similar results were obtained for human fibroblasts. γ-Radiation leads to substantial changes in the chromatin structure of stimulated lymphocytes: ABL and BCR genes are shifted to the nuclear center, and mutual ABL-BCR distances become much shorter in the G1 and S(G2 ) nuclei. Therefore, we hypothesize that the changes of chromatin structure in the irradiated lymphocytes might increase the probability of a translocation during G1 and S(G2 ) stages of the cell cycle. The fact that the genes involved in the t(8; 14) translocation are also located close together in a certain fraction of cells substantiates the hypothesis that physical distance plays an important role in the processes leading to the translocations that are responsible for oncogenic transformation of cells.
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