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HCFC‐22 is an ozone‐depleting substance with a greenhouse effect. The atmospheric mole fractions of HCFC‐22 have been increasing since the 1950s. Within the NDACC‐IRWG network, HCFC‐22 mol fractions can be retrieved from solar absorption spectra measured by ground‐based FTIR. However, only a few sites have provided HCFC‐22 data sets. Here, we demonstrate a harmonized FTIR HCFC‐22 retrieval strategy and generate a new global NDACC‐IRWG HCFC‐22 data set at 16 FTIR sites. The systematic and random uncertainties are 5.3%–8.7% and 3.2%–8.0%, respectively. A maximum HCFC‐22 column annual growth rate was observed in 2009 with a mean of 7.65 ± 1.39 ppt/year, and the HCFC‐22 annual growth rate decreased to 3.57 ± 1.39 ppt/year (2016–2020) and 2.15 ± 2.09 ppt/year (2021–2023). The annual growth rates derived from the FTIR measurements are compared to the ones derived from NOAA surface flask samplings and ACE‐FTS satellite measurements, and the three independent data sets show a good agreement. Plain Language Summary: Monitoring the atmospheric HCFC‐22 mol fraction and its long‐term trend is important to the stratospheric ozone layer and climate change. Ground‐based FTIR measurements within the NDACC‐IWRG community provide a powerful technique for observing atmospheric trace gases. However, due to different retrieval software and procedures among the sites, the record was too heterogeneous for monitoring the global evolution of HCFC‐22 over time. In this study, we propose a harmonized FTIR HCFC‐22 retrieval strategy and generate a global NDACC‐IRWG HCFC‐22 data set at 16 FTIR sites. The retrieval uncertainty of the FTIR HCFC‐22 is well presented and discussed. Based on the new FTIR HCFC‐22 measurements, the HCFC‐22 annual growth rates between 1990 and 2023 are evaluated. The results are compared with two independent data sets: NOAA flask samplings and ACE‐FTS satellite measurements. Good agreement among the three data sets is found, with a clear decrease in the growth rate of atmospheric HCFC‐22 in recent years. According to the latest Montreal Protocol, HCFC‐22 should be phased out within the next 5–6 years. The global FTIR observations will assure continuity into the next years and decades when HCFC‐22 mol fractions should start decreasing after the official phase‐out. Key Points: Implemented a harmonized NDACC‐IRWG FTIR HCFC‐22 retrieval strategy and provided a new global long‐term HCFC‐22 data setA decrease in the growth rate of the atmospheric HCFC‐22 column has been observed by FTIR measurements since 2009The FTIR, NOAA flask samplings, and ACE‐FTS satellite observations show a good agreement in the HCFC‐22 trend [ABSTRACT FROM AUTHOR]

The Brewer‐Dobson Circulation (BDC) determines the distribution of long‐lived tracers in the stratosphere; therefore, their changes can be used to diagnose changes in the BDC. We evaluate decadal (2005–2018) trends of nitrous oxide (N2O) in two versions of the Whole Atmosphere Chemistry‐Climate Model (WACCM) by comparing them with measurements from four Fourier transform infrared (FTIR) ground‐based instruments, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS), and with a chemistry‐transport model (CTM) driven by four different reanalyses. The limited sensitivity of the FTIR instruments can hide negative N2O trends in the mid‐stratosphere because of the large increase in the lowermost stratosphere. When applying ACE‐FTS measurement sampling on model datasets, the reanalyses from the European Center for Medium Range Weather Forecast (ECMWF) compare best with ACE‐FTS, but the N2O trends are consistently exaggerated. The N2O trends obtained with WACCM disagree with those obtained from ACE‐FTS, but the new WACCM version performs better than the previous above the Southern Hemisphere in the stratosphere. Model sensitivity tests show that the decadal N2O trends reflect changes in the stratospheric transport. We further investigate the N2O Transformed Eulerian Mean (TEM) budget in WACCM and in the CTM simulation driven by the latest ECMWF reanalysis. The TEM analysis shows that enhanced advection affects the stratospheric N2O trends in the Tropics. While no ideal observational dataset currently exists, this model study of N2O trends still provides new insights about the BDC and its changes because of the contribution from relevant sensitivity tests and the TEM analysis. Plain Language Summary: The circulation in the stratosphere is characterized by upward motion above the Tropics, followed by poleward and downward motions above the high latitudes. Changes in the pattern of this stratospheric circulation are currently a challenging topic of research. We investigate the decennial changes of this stratospheric circulation using observations and numerical simulations of the long‐lived tracer nitrous oxide. Observations are obtained from ground‐based and satellite instruments. Numerical simulations include complex atmospheric models that reproduce the chemistry and dynamics of the stratosphere. Both observations and models show differences between the hemispheres in the nitrous oxide decennial changes. Unfortunately, the current observations of nitrous oxide are not perfect. The ground‐based instruments cannot correctly measure the changes of nitrous oxide in the northern hemisphere. The satellite does not measure at all times, and it spatially covers more the high latitudes, which negatively affects the measurements of nitrous oxide. On the other hand, model simulations can provide valuable insights into the changes in the stratospheric circulation. They show that changes in the stratospheric circulation cause the differences between hemispheres in the nitrous oxide trends and show that the circulation changes can be associated with different physical processes. Key Points: Sparse sampling of Atmospheric Chemistry Experiment Fourier Transform Spectrometer exaggerates the stratospheric nitrous oxide trendsTransformed Eulerian Mean analysis shows that the residual mean advection contributes to the positive nitrous oxide trend in the TropicsThe Whole Atmosphere Community‐Climate Model simulates weaker hemispheric asymmetries of the nitrous oxide trends compared to reanalyses [ABSTRACT FROM AUTHOR]

Using multidecadal time series of ground‐based and satellite Fourier transform infrared measurements of inorganic fluorine (i.e., total fluorine resident in stratospheric fluorine reservoirs), we investigate stratospheric circulation changes over the past 20 years. The representation of these changes in five modern reanalyses is further analyzed through chemical‐transport model (CTM) simulations. From the observations but also from all reanalyses, we show that the inorganic fluorine is accumulating less rapidly in the Southern Hemisphere than in the Northern Hemisphere during the 21st century. Comparisons with a study evaluating the age‐of‐air of these reanalyses using the same CTM allow us to link this hemispheric asymmetry to changes in the Brewer‐Dobson circulation (BDC), with the age‐of‐air of the Southern Hemisphere getting younger relative to that of the Northern Hemisphere. Large differences in simulated total columns and absolute trend values are, nevertheless, depicted between our simulations driven by the five reanalyses. Superimposed on this multidecadal change, we, furthermore, confirm a 5–7‐year variability of the BDC that was first described in a recent study analyzing long‐term time series of hydrogen chloride (HCl) and nitric acid (HNO3). It is important to stress that our results, based on observations and meteorological reanalyses, are in contrast with the projections of chemistry‐climate models in response to the coupled increase of greenhouse gases and decrease of ozone‐depleting substances, calling for further investigations and the continuation of long‐term observations. Plain Language Summary: The overturning circulation of the stratosphere is projected to change in response to increases in greenhouse gases and decreases in ozone‐depleting substances, with the Southern Hemisphere branch expected to get weaker relative to the Northern Hemisphere. Here, we use 30‐year time series of observations and simulations of a long‐lived tracer to investigate stratospheric circulation changes. The observations analyzed are from ground‐based and satellite instruments. We compare them with simulations that use a chemical‐transport model driven by winds from meteorological reanalyses of 1990–2019. A reanalysis assimilates meteorological measurements into a forecast model to simulate the best possible representation of the atmospheric state. All five simulations, which use different reanalyses, agree with the observational analysis showing that the analyzed tracer is accumulating less rapidly in the Southern Hemisphere than in the Northern Hemisphere through 2019. This hemispheric asymmetry is attributed to changes in the stratospheric transport circulation, with the Southern Hemisphere branch getting stronger relative to the Northern Hemisphere. Our results support the conclusions of a recent observational study but do not support circulation changes projected by chemistry‐climate models. This study highlights the crucial importance of long‐term observation time series. Key Points: Fluorine in the stratosphere is accumulating less rapidly in the Southern Hemisphere than in the Northern HemisphereThe observed fluorine trend asymmetry, attributed to transport circulation changes, opposes trends predicted by chemistry‐climate modelsObservations and five modern reanalyses are qualitatively in agreement with these changes, calling for maintaining long‐term observations [ABSTRACT FROM AUTHOR]

Total columns of the trace gases nitric acid (HNO3) and hydrogen chloride (HCl) are sensitive to variations in the lower stratospheric age of air, a quantity that describes transport time scales in the stratosphere. Analyses of HNO3 and HCl columns from the Network for the Detection of Atmospheric Composition Change panning 77°S to 79°N have detected changes in the extratropical stratospheric transport circulation from 1994 to 2018. The HNO3 and HCl analyses combined with the age of air from a simulation using the MERRA2 reanalysis show that the Southern Hemisphere lower stratosphere has become 1 month/decade younger relative to the Northern Hemisphere, largely driven by the Southern Hemisphere transport circulation. The analyses reveal multiyear anomalies with a 5‐ to 7‐year period driven by interactions between the circulation and the quasi‐biennial oscillation in tropical winds. This hitherto unrecognized variability is large relative to hemispheric transport trends and may bias ozone trend regressions. Plain Language Summary: Our analyses of the 25‐year Network for the Detection of Atmospheric Composition Change column HNO3 and HCl data records from nine stations provide observational evidence that air in the Southern Hemisphere lower stratosphere has been getting younger relative to the Northern Hemisphere at a rate of 1 month/decade since 1994. This stands in contrast to several model studies that predict that Antarctic ozone hole recovery in this century will increase the Southern Hemisphere age of air relative to the Northern Hemisphere. The analyses also reveal extratropical variability with a 5‐ to 7‐year period driven by interactions between the circulation and tropical winds. This previously unrecognized, low‐frequency variability is much larger than hemispheric transport trends and is likely to cause bias in trends calculated using data records shorter than about two decades. Understanding and quantifying changes in the transport circulation matters to our ability to model how our protective O3 layer will evolve in the future. Key Points: Trace gas data show southern stratospheric air is getting younger relative to the Northern Hemisphere, in contrast to model predictionsBoth extratropical hemispheres have dynamically driven 5‐ to 7‐year periodicity with large amplitude relative to the age trendMultidecadal data sets are required to quantify transport trends that are not confounded by large extratropical variability [ABSTRACT FROM AUTHOR]

Knowledge of how the optimum temperature for growth (T°opt) varies during ontogeny, and how close it is to the temperatures that induce phenotypic masculinization is fundamental to the understanding of the evolution of thermolabile sex determinism (TSD) in fishes. In blue tilapia Oreochromis aureus,T °opt is 32·6° C at the start of exogenous feeding (10 mg fish) and it decreases by c. 1° C each time that the fish body mass increases by an order of magnitude. Temperatures <35° C are not sufficient to induce complete phenotypic masculinization. Based on a multiple-regression model (r2=0·938) plotting growth against body mass and water temperature, genotypically female tilapia living at high temperatures during the thermosensitive period (21–28 days) and being reversed into phenotypic males would incur an initial growth disadvantage over fish living at T°opt, but not over those living at slightly colder temperatures (27–29° C). This initial disadvantage would be later compensated for by faster growth because of between-sex growth dimorphism to the detriment of phenotypic females. These arguments suggest that there is no definite pressure against the selection of TSD in blue tilapia and probably other Oreochromis spp. Copyright 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

The article focuses on a study related to lymphangiogenesis in melanoma during pregnancy in correlation with the prolactin signalling pathway. The study states that the computer-assisted morphometric analysis showed increase in the lymphatic vessels of pregnant women. The study concludes that the lymphatic vessel relative surface area at the periphery of the tumor is high in pregnant patients with melanoma compared to non-pregnant women.