Northern Hemisphere Winter Season Research Articles

Information on operational sea ice products and current and future activities of the German ice service

The ice service at the German Federal Maritime and Hydrographic Agency and its predecessors has been committed to the safety and easiness of ship navigation for more than 100 years. Within this paper, an overview of the operational products issued by the German ice service on a daily to weekly basis throughout the northern hemisphere winter season is given. These comprise written reports, ice charts, NAVTEX messages, and messages via the Global Telecommunication System to inform about the sea ice situation in German coastal waters, the Baltic Sea, and worldwide. Furthermore, the ice service has systematically collected ice observation data along the German North Sea and Baltic Sea coast since the winter of 1896/1897. The history of the German ice service is presented to put the sea ice data into context of the observation technologies used in the course of the existence of the ice service. These long-term observations enable climatological analyses of the sea ice cover in German coastal waters necessary for the safe operation of offshore infrastructure. An evaluation of the data shows a recent decline in sea ice occurrence in the Baltic Sea and German Bight. Current work is ongoing to preserve more of the historic data in digital form and also to transform the products to conform to modern standards in digital technologies and interactive solutions for the customers.

Determination of the chemical equator from GEOS-Chem model simulation: a focus on the tropical western Pacific region

Abstract. The tropical western Pacific (TWP) plays an important role in global stratosphere–troposphere exchange and is an active region of the interhemispheric transport (IHT). Common indicators for transport between the hemispheres like the tropical rain belt are too broad or lack precision in the TWP. In this paper, we provide a method to determine the atmospheric chemical equator (CE), which is a boundary for air mass transport between the two hemispheres in the tropics. This method used the model output from an artificial passive tracer simulated by the chemical transport model GEOS-Chem in the troposphere. We investigated the movement of the CE in the tropics, which indicates the migration of atmospheric circulation systems and air mass origins. Our results show the CE on different timescales, suggesting that the different features of the IHT in different regions are highly related to the variation in the circulation systems. We compared the CE with the tropical wind fields, indicating that the region of IHT does not coincide with the convergence of the 10 m wind fields in the tropical land sectors and the TWP region. We compared the CE with the atmospheric composition such as satellite data of CH4 and model simulation of sulfur hexafluoride (SF6). The results show that the CE and north–south gradient of CH4 in the Indian Ocean in January are well consistent with each other, which indicates the CE has good potential to estimate the IHT inferred by observations. We discussed the vertical extent and the meridional extent of the IHT. We find that the vertical structure above 2 km has a slight northern tilt in the Northern Hemisphere (NH) winter season and a southern tilt in the NH summer, meaning the seasonality of the migration of the CE at the lower altitude is larger than that at the higher altitude. The meridional extent of the CE indicates a narrow transition zone where IHT happens throughout the year. We find that the meridional extent above South America is larger compared to other regions. The distribution of the land–sea contrast plays an important role in the meridional extent of IHT. We focus on the TWP region and further compared the tropical rain belt with the CE. There is a broad region of high precipitation occurring in the TWP region, and it is difficult to determine the IHT by the rain belt. In the NH winter, the CE is not consistent with the tropical rain belt in the TWP but is confined to the southern branch of the peak of the rain belt. For the other seasons, both indicators of IHT agree.

Surveillance of Severe Acute Respiratory Infection and Influenza Vaccine Effectiveness among Hospitalized Italian Adults, 2021/22 Season

Following an extremely low incidence of influenza during the first waves of the ongoing COVID-19 pandemic, the 2021/22 Northern Hemisphere winter season saw a resurgence of influenza virus circulation. The aim of this study was to describe epidemiology of severe acute respiratory infections (SARIs) among Italian adults and estimate the 2021/22 season influenza vaccine effectiveness. For this purpose, a test-negative case-control study was conducted in a geographically representative sample of Italian hospitals. Of 753 SARI patients analyzed, 2.5% (N = 19) tested positive for influenza, most of which belonged to the A(H3N2) subtype. Phylogenetic analysis showed that these belonged to the subclade 3C.2a1b.2a.2, which was antigenically different from the 2021/22 A(H3N2) vaccine component. Most (89.5%) cases were registered among non-vaccinated individuals, suggesting a protective effect of influenza vaccination. Due to a limited number of cases, vaccine effectiveness estimated through the Firth's penalized logistic regression was highly imprecise, being 83.4% (95% CI: 25.8-97.4%) and 83.1% (95% CI: 22.2-97.3%) against any influenza type A and A(H3N2), respectively. Exclusion of SARS-CoV-2-positive controls from the model did not significantly change the base-case estimates. Within the study limitations, influenza vaccination appeared to be effective against laboratory-confirmed SARI.

1331. Pneumococcal Colonization Among Children 5 years of Age and Younger During SARS-CoV-2 Pandemic

Abstract Background Children ≤5 years of age have the highest rates of pneumococcal colonization and play an important role in the spread of pneumococcus. Our objective was to determine whether the public health measures (physical distancing, masking, and shelter-in-place orders) implemented to slow the spread of SARS-CoV-2 pandemic had an impact on pneumococcal colonization rates among children aged ≤5 years with and without respiratory symptoms during the first year of SARS-CoV-2 pandemic (4/1/20 to 3/31/21). Methods This is a single center retrospective cohort study. The study period was divided in 3 four-month periods to represent the initial period of strict adherence to public health measures (period 1: Apr-Jul), relaxation of some of these measures (period 2: Aug-Nov) and Northern hemisphere winter season (period 3: Dec-Mar). We used salvaged mid-turbinate samples obtained as part of routine care from patients without respiratory symptoms but screened for SARS-CoV-2 prior to surgery or aerosol generating procedures (asymptomatic) or from patients with respiratory symptoms tested for SARS-CoV-2 and/or other respiratory viruses (symptomatic). Samples were evaluated for pneumococcal colonization by real-time PCR using CDC lytA primers. Sample size was calculated based on the assumption of lower colonization rates in period 1 and gradual increase (10-15%) in the following study periods. Results A total of 311 patients were included (185 asymptomatic and 126 symptomatic). Demographics, SARS-CoV-2 PCR and pneumococcal colonization results are shown in Table 1. Pneumococcal colonization rates for asymptomatic and symptomatic children were 14% and 22% (p=0.06), respectively. The odds of colonization of asymptomatic children were similar during period 2 (OR 0.96 [95%CI 0.34-2.67]) and period 3 (OR 0.53 [95%CI 0.17-1.62]), using period 1 as reference and after adjusting for age, sex, and SARS-COV-2 results. The odds of colonization of symptomatic children were also similar across the 3 study periods (period 2 OR 1.28 [95%CI 0.41-4.01] and period 3 OR 0.73 [95% CI 0.24-2.18]). Table 1.Characteristics of asymptomatic and symptomatic groups Conclusion Pneumococcal colonization rates were not significantly impacted by public health measures implemented during the first year of the SARS-CoV-2 pandemic and did not correlate with SARS-CoV-2 positivity. Disclosures Liset Olarte, MD, MSc, GSK: Grant/Research Support|Merck: Grant/Research Support|Pfizer: Grant/Research Support|Sanofi: Grant/Research Support Douglas S. Swanson, MD, Merck: Grant/Research Support|Pfizer: Grant/Research Support|Sanofi: Grant/Research Support Brian R. Lee, PhD, MPH, CDC: Grant/Research Support|Merck: Grant/Research Support Christopher J. Harrison, MD, Astellas: Grant/Research Support|GSK: Grant/Research Support|Merck: Grant/Research Support|Pediatric News: Honoraria|Pfizer: Grant/Research Support Rangaraj Selvarangan, BVSc, PhD, D(ABMM), FIDSA, F(AAM), BioFire: Grant/Research Support|Luminex: Grant/Research Support.

Global assessment of spatiotemporal variability of wet, normal and dry conditions using multiscale entropy-based approach

In recent decades, human-induced climate change has caused a worldwide increase in the frequency/intensity/duration of extreme events, resulting in enormous disruptions to life and property. Hence, a comprehensive understanding of global-scale spatiotemporal trends and variability of extreme events at different intensity levels (e.g., moderate/severe/extreme) and durations (e.g., short-term/long-term) of normal, dry and wet conditions is essential in predicting/forecasting/mitigating future extreme events. This article analyses these aspects using estimates of a non-stationary standardized precipitation evapotranspiration index corresponding to different accumulation periods for 0.5° resolution CRU grids at globe-scale. Results are analyzed with respect to changes in land-use/landcover and geographic/location indicators (latitude, longitude, elevation) at different time scales (decadal/annual/seasonal/monthly) for each continent. The analysis showed an (i) increasing trend in the frequency/count of both dry and wet conditions and variability of dry conditions, and (ii) contrasting (decreasing) trend in the variability of wet conditions, possibly due to climate change-induced variations in atmospheric circulations. Globally, the highest variability in the wet and dry conditions is found during the Northern hemisphere's winter season. The decadal-scale analysis showed that change in variability in dry and wet conditions has been predominant since the 1930s and 1950s, respectively and is found to be increasing in recent decades.

North Atlantic Oscillation response in GeoMIP experiments G6solar and G6sulfur: why detailed modelling is needed for understanding regional implications of solar radiation management

Abstract. The realization of the difficulty of limiting global-mean temperatures to within 1.5 or 2.0 ∘C above pre-industrial levels stipulated by the 21st Conference of Parties in Paris has led to increased interest in solar radiation management (SRM) techniques. Proposed SRM schemes aim to increase planetary albedo to reflect more sunlight back to space and induce a cooling that acts to partially offset global warming. Under the auspices of the Geoengineering Model Intercomparison Project, we have performed model experiments whereby global temperature under the high-forcing SSP5-8.5 scenario is reduced to follow that of the medium-forcing SSP2-4.5 scenario. Two different mechanisms to achieve this are employed: the first via a reduction in the solar constant (experiment G6solar) and the second via modelling injections of sulfur dioxide (experiment G6sulfur) which forms sulfate aerosol in the stratosphere. Results from two state-of-the-art coupled Earth system models (UKESM1 and CESM2-WACCM6) both show an impact on the North Atlantic Oscillation (NAO) in G6sulfur but not in G6solar. Both models show a persistent positive anomaly in the NAO during the Northern Hemisphere winter season in G6sulfur, suggesting an increase in zonal flow and an increase in North Atlantic storm track activity impacting the Eurasian continent and leading to high-latitude warming over Europe and Asia. These results are broadly consistent with previous findings which show similar impacts from stratospheric volcanic aerosol on the NAO and emphasize that detailed modelling of geoengineering processes is required if accurate impacts of SRM effects are to be simulated. Differences remain between the two models in predicting regional changes over the continental USA and Africa, suggesting that more models need to perform such simulations before attempting to draw any conclusions regarding potential continental-scale climate change under SRM.

A Study of False Alarms of a Major Sudden Stratospheric Warming by Real-Time Subseasonal-to-Seasonal Forecasts for the 2017/2018 Northern Winter

This study investigates false alarms of a major sudden stratospheric warming (MSSW) by real-time subseasonal-to-seasonal forecast data of the European Centre for Medium-Range Weather Forecasts system for the 2017/2018 Northern Hemisphere winter season. The analysis reveals two false alarm cases in the season, one in early December and the other in early February. Each case is characterized by ensembles of which a considerable part of the members (MSSW members) show an MSSW, that is, reversal of the zonal mean zonal wind in the extratropical stratosphere on similar calendar dates. Ensemble forecasts that are initialized earlier or later basically lack an MSSW, demonstrating clear intraseasonal variability in the frequency of forecasted MSSWs. For each false alarm case, the MSSW member mean field shows equatorward displacement of the polar vortex around the onset date. For both cases, the MSSW members accompany stronger wave activity in the lower stratosphere than other non-MSSW members and reanalysis data. They are further associated with higher geopotential height than the non-MSSW members, in the upper troposphere over northeastern Canada and Greenland before the first case, and lower height over northeastern Eurasia before the second case. These are located over the ridge and trough, respectively, of the climatological planetary wave of zonal wave number one, and are consistent with the increased wave activity.

Analysis of 24 years of mesopause region OH rotational temperature observations at Davis, Antarctica – Part 1: long-term trends

Abstract. The long-term trend, solar cycle response, and residual variability in 24 years of hydroxyl nightglow rotational temperatures above Davis research station, Antarctica (68∘ S, 78∘ E) are reported. Hydroxyl rotational temperatures are a layer-weighted proxy for kinetic temperatures near 87 km altitude and have been used for many decades to monitor trends in the mesopause region in response to increasing greenhouse gas emissions. Routine observations of the OH(6-2) band P-branch emission lines using a scanning spectrometer at Davis station have been made continuously over each winter season since 1995. Significant outcomes of this most recent analysis update are the following: (a) a record-low winter-average temperature of 198.3 K is obtained for 2018 (1.7 K below previous low in 2009); (b) a long-term cooling trend of -1.2±0.51 K per decade persists, coupled with a solar cycle response of 4.3±1.02 K per 100 solar flux units; and (c) we find evidence in the residual winter mean temperatures of an oscillation on a quasi-quadrennial (QQO) timescale which is investigated in detail in Part 2 of this work. Our observations and trend analyses are compared with satellite measurements from Aura/MLS version v4.2 level-2 data over the last 14 years, and we find close agreement (a best fit to temperature anomalies) with the 0.00464 hPa pressure level values. The solar cycle response (3.4±2.3 K per 100 sfu), long-term trend (-1.3±1.2 K per decade), and underlying QQO residuals in Aura/MLS are consistent with the Davis observations. Consequently, we extend the Aura/MLS trend analysis to provide a global view of solar response and long-term trend for Southern and Northern Hemisphere winter seasons at the 0.00464 hPa pressure level to compare with other observers and models.

Anomalous wind circulation over Taipei, Taiwan during the northern winter seasons of 2004 and 2005- A case study

This research reports, for the first time, an anomalous wind circulation over Taipei (Latitude 25.030N, Longitude 121.510E), Taiwan during the northern hemisphere winter season (December, January, and February) of years 2004 and 2005. The anomalous wind circulation of meridional winds, which showed southward directions during the winter seasons of 2004 and 2005 instead of northward winds, is noticed from one kilometer altitude range (lower troposphere) and that trend continued till around 20 km altitude range (lower stratosphere). To ascertain whether such a disturbed nature of wind pattern existed over nearby locations to Taipei, we have analyzed radiosonde-measured meridional and zonal winds over four nearby stations station to Taipei including, Roig, Xiamen, Minami and Fuzhou. Surprisingly, no anomalous wind behavior is seen except over Taipei during the northern winter seasons of 2004 and 2005. On the other hand, the European Centre for Medium-Range Weather Forecasts (ECMWF) model-predicted winds do not show any anomalous wind patterns over Taipei and other nearby stations, possibly due to the large averaging of internal variabilities of reanalysis databases. The plausible physical mechanisms of these disturbed meridional wind patterns are not understood at this juncture, but it is believed that local winds and atmospheric pollutants might have created an amicable environment as to provide such a disturbed meridional wind pattern over Taipei, Taiwan in the winter season of 2004 and 2005.

Psychometric evaluation of a caregiver diary for the assessment of symptoms of respiratory syncytial virus

BackgroundThere are no clinical outcome assessment (COA) tools developed in accordance with Food and Drug Administration (FDA) guidance suitable for the evaluation of symptoms associated with respiratory syncytial virus (RSV) infection among infants. The Gilead RSV Caregiver Diary (GRCD) is being developed to fulfill this need; the present research evaluates the GRCD and documents its reliability, validity, and responsiveness among children < 24 months of age with acute RSV infection.MethodsA prospective, observational study was conducted in the United States during the 2014–2015 northern hemisphere winter season. Subjects were < 24-month, full-term, previously healthy infants with confirmed RSV infection and ≤5 days of symptoms. The GRCD was completed twice daily for 14 days by caregivers. Additional data were collected during the initial visit, subsequent visits, and end-of-study interview. Test-retest reliability (kappa and intraclass correlation coefficients [ICCs]), construct validity (correlations and factor analyses), discriminating ability (analyses of variance and chi-square), and responsiveness (effect sizes and standardized response means) were evaluated.ResultsA total of 103 subjects were enrolled (mean age 7.4 ± 5.3 months). GRCD items were grouped into different subscales according to question content, which, with the exception of the behavior impact domain (ICC = 0.43), demonstrated internal consistency (alphas = 0.78–0.94) and test-retest reliability (ICCs = 0.77–0.94). Hypothesized correlations with parent global ratings of RSV severity ranged from 0.45 to 0.70 and provided support for construct validity. Support for discriminating ability was limited. Effect sizes ranged from − 1.48 to − 4.40, indicating the GRCD was responsive to change.ConclusionsThese psychometric analyses support the validity, reliability, and responsiveness of the GRCD for assessing RSV symptoms in children < 24 months of age.

Review and assessment of latent and sensible heat flux accuracy over the global oceans

For over a decade, several research groups have been developing air-sea heat flux information over the global ocean, including latent (LHF) and sensible (SHF) heat fluxes over the global ocean. This paper aims to provide new insight into the quality and error characteristics of turbulent heat flux estimates at various spatial and temporal scales (from daily upwards). The study is performed within the European Space Agency (ESA) Ocean Heat Flux (OHF) project. One of the main objectives of the OHF project is to meet the recommendations and requirements expressed by various international programs such as the World Research Climate Program (WCRP) and Climate and Ocean Variability, Predictability, and Change (CLIVAR), recognizing the need for better characterization of existing flux errors with respect to the input bulk variables (e.g. surface wind, air and sea surface temperatures, air and surface specific humidities), and to the atmospheric and oceanic conditions (e.g. wind conditions and sea state). The analysis is based on the use of daily averaged LHF and SHF and the associated bulk variables derived from major satellite-based and atmospheric reanalysis products. Inter-comparisons of heat flux products indicate that all of them exhibit similar space and time patterns. However, they also reveal significant differences in magnitude in some specific regions such as the western ocean boundaries during the Northern Hemisphere winter season, and the high southern latitudes. The differences tend to be closely related to large differences in surface wind speed and/or specific air humidity (for LHF) and to air and sea temperature differences (for SHF). Further quality investigations are performed through comprehensive comparisons with daily-averaged LHF and SHF estimated from moorings. The resulting statistics are used to assess the error of each OHF product. Consideration of error correlation between products and observations (e.g., by their assimilation) is also given. This reveals generally high noise variance in all products and a weak signal in common with in situ observations, with some products only slightly better than others. The OHF LHF and SHF products, and their associated error characteristics, are used to compute daily OHF multiproduct-ensemble (OHF/MPE) estimates of LHF and SHF over the ice-free global ocean on a 0.25°×0.25° grid. The accuracy of this heat multiproduct, determined from comparisons with mooring data, is greater than for any individual product. It is used as a reference for the anomaly characterization of each individual OHF product.

Regional temperature change potentials for short-lived climate forcers based on radiative forcing from multiple models

Abstract. We calculate the absolute regional temperature change potential (ARTP) of various short-lived climate forcers (SLCFs) based on detailed radiative forcing (RF) calculations from four different models. The temperature response has been estimated for four latitude bands (90–28° S, 28° S–28° N, 28–60° N, and 60–90° N). The regional pattern in climate response not only depends on the relationship between RF and surface temperature, but also on where and when emissions occurred and atmospheric transport, chemistry, interaction with clouds, and deposition. We present four emissions cases covering Europe, East Asia, the global shipping sector, and the entire globe. Our study is the first to estimate ARTP values for emissions during Northern Hemisphere summer (May–October) and winter season (November–April). The species studied are aerosols and aerosol precursors (black carbon, organic carbon, SO2, NH3), ozone precursors (NOx, CO, volatile organic compound), and methane (CH4). For the response to BC in the Arctic, we take into account the vertical structure of the RF in the atmosphere, and an enhanced climate efficacy for BC deposition on snow. Of all SLCFs, BC is the most sensitive to where and when the emissions occur, as well as giving the largest difference in response between the latitude bands. The temperature response in the Arctic per unit BC emission is almost four times larger and more than two times larger than the global average for Northern Hemisphere winter emissions for Europe and East Asia, respectively. The latitudinal breakdown likely gives a better estimate of the global temperature response as it accounts for varying efficacies with latitude. An annual pulse of non-methane SLCF emissions globally (representative of 2008) lead to a global cooling. In contrast, winter emissions in Europe and East Asia give a net warming in the Arctic due to significant warming from BC deposition on snow.

WRF prediction of two winter season Saharan dust events using PM10 concentrations: Boundary versus initial conditions

During the northern hemisphere winter and spring seasons Saharan dust events overspreading West Africa are frequent and linked to mid-latitude interactions. The dust events have the ability to produce low visibilities, poor air quality and can promote respiratory disease. While a number of case studies have been undertaken, the ability to forecast Saharan dust events is largely unknown. To investigate this matter, we have performed hindcasts using the weather research and forecasting (WRF) model with the Goddard Chemistry Aerosols Radiation Transport (GOCART) module, with 6-h boundary conditions from the NOAA ' National Center for Environmental Prediction (NCEP) final analysis (FNL). We use observed and forecasted PM10 concentrations to evaluate the hindcasts. The hindcasts begin with different conditions 3–8 days before two Saharan dust events where the maximum Particulate matter at 10 microns (PM10) concentrations are observed on 20 January and 7 February 2012 in Dakar, Senegal. The results show that all hindcasts are able to capture the timing of the peak on 20 January but the maximum peak during the second dust event occurs one day prior to the observed peak on 7 February with similar pattern from satellite based aerosol optical depth (AOD) estimates. The hindcasts have positive biases in PM10 concentrations relative to the observations in Dakar Senegal. The hindcasts suggest that WRF model has the potential to effectively forecasts Saharan dust events in real-time forecasts, however, they must be evaluated against additional surface PM10 observations at varying locations, which are currently sparse over West Africa.

Exceptionally strong summer-like zonal wind reversal in the upper mesosphere during winter 2015/16

Abstract. The 2015/16 Northern Hemisphere winter season was marked by peculiarities in the circulation pattern in the high-latitude mesopause region. Wind measurements from the Andenes (69° N, 13° E) meteor radar show westward winds below 84 km and eastward winds above. This wind pattern in the zonal wind was observable between the end of December 2015 and the end of January 2016, i.e., conditions that are typical for the summer were found during winter. Additional meteor radar measurements at midlatitude stations did not show such a zonal wind reversal but indicate, together with the polar latitude stations, a reversal of the horizontal temperature gradient. This is confirmed by global satellite measurements. Therefore, it is plausible that the polar latitude summer-like zonal wind reversal in December–January is in accordance with the reversed horizontal temperature gradient assuming a thermal wind balance between mid- and polar latitudes. The reversed horizontal temperature gradient itself is induced by stationary planetary waves at lower and midlatitudes in the mesosphere, leading to a weakening of the residual circulation above the European sector.

Cruise shipping in Brazil: An emergent or established market?

ABSTRACT In Brazil, the cruise shipping industry has showing remarkable growth by expanding and diversifying routes, and incorporating bigger, more luxurious ships, thereby establishing cruising as the equivalent of more conventional destination based tourism. Initially the cruise shipping companies started activities in the Brazilian market to optimise fleet utilisation during the Northern Hemisphere winter season. However, while for more than a decade the Brazilian market achieved double-digit annual growth, after 2011 the numbers of passengers, ports visited and ships used have declined. This paper contends that Brazil is a mature cruise market in its own right and examines the industry in terms of both itineraries being offered and the role of Brazilian cruising in fleet deployment.

Linkages between observed, modeled Saharan dust loading and meningitis in Senegal during 2012 and 2013.

The Sahara desert transports large quantities of dust over the Sahelian region during the Northern Hemisphere winter and spring seasons (December-April). In episodic events, high dust concentrations are found at the surface, negatively impacting respiratory health. Bacterial meningitis in particular is known to affect populations that live in the Sahelian zones, which is otherwise known as the meningitis belt. During the winter and spring of 2012, suspected meningitis cases (SMCs) were with three times higher than in 2013. We show higher surface particular matter concentrations at Dakar, Senegal and elevated atmospheric dust loading in Senegal for the period of 1 January-31 May during 2012 relative to 2013. We analyze simulated particulate matter over Senegal from the Weather Research and Forecasting (WRF) model during 2012 and 2013. The results show higher simulated dust concentrations during the winter season of 2012 for Senegal. The WRF model correctly captures the large dust events from 1 January-31 March but has shown less skill during April and May for simulated dust concentrations. The results also show that the boundary conditions are the key feature for correctly simulating large dust events and initial conditions are less important.

A chemistry‐climate model study of past changes in the Brewer‐Dobson circulation

AbstractModel simulations indicate an acceleration of the Brewer‐Dobson circulation (BDC) in the past with a direct impact on the exchange of air masses between the troposphere and the stratosphere. However, most observational data sets do not confirm the model results. Bönisch et al. (2011) and Ray et al. (2010) indicate a strengthening of the BDC in its shallow branch and a weakening in its deep branch. In contrast, balloon‐borne measurements and Michelson Interferometer for Passive Atmospheric Sounding satellite observations show no significant acceleration of the BDC at Northern Hemisphere (NH) midlatitudes. In our study, the change of the BDC in the recent past is analyzed from simulations with the chemistry‐climate model ECHAM/MESSy Atmospheric Chemistry. As the sign of change considerably depends on the underlying forcings, namely, changes in concentrations of greenhouse gases (GHGs) and ozone‐depleting substances (ODSs), as well as their interactions, we separate their contributions by using sensitivity simulations. The changes in tropical upward mass flux indicate a strengthening of the BDC between 1960 and 2000 in NH winter season in the lower and a weakening in the upper stratosphere with a change in sign at 10 hPa. While the lower stratospheric increase of about 2%/decade is caused by equal contributions from rising GHGs and ODSs, rising ODS concentrations counteract the GHG effect in the middle and upper stratosphere with a total decrease of about 0.5%/decade. Changes in mean age of air show a decrease of about 0.13 yr/decade in the lower and middle stratosphere and a slight increase in the Arctic upper stratosphere and lower mesosphere, which is induced by interactions between the forcings.

A Comparison of the Impacts of Radiosonde and AMSU Radiance Observations in GSI Based 3DEnsVar and 3DVar Data Assimilation Systems for NCEP GFS

The impact of observations can be dependent on many factors in a data assimilation (DA) system including data quality control, preprocessing, skill of the model, and the DA algorithm. The present study focuses on comparing the impacts of observations assimilated by two different DA algorithms. A three-dimensional ensemble-variational (3DEnsVar) hybrid data assimilation system was recently developed based on the Gridpoint Statistical Interpolation (GSI) data assimilation system and was implemented operationally for the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS). One question to address is, how the impacts of observations on GFS forecasts differ when assimilated by the traditional GSI-three dimensional variational (3DVar) and the new 3DEnsVar. Experiments were conducted over a 6-week period during Northern Hemisphere winter season at a reduced resolution. For both the control and data denial experiments, the forecasts produced by 3DEnsVar were more accurate than GSI3DVar experiments. The results suggested that the observations were better and more effectively exploited to increment the background forecast in 3DEnsVar. On the other hand, in GSI3DVar, where the observation will be making mostly local, isotropic increments without proper flow dependent extrapolation is more sensitive to the number and types observations assimilated.

Two-day wave observations over the middle and high latitudes in the NH and SH using COSMIC GPSRO measurements

The characteristics of the quasi-2-day wave (QTDW) in the upper stratosphere and lower mesospheric (USLM) altitudes over the northern hemisphere (NH) and southern hemisphere (SH) have been studied by using Global Positioning Radio Occultation (GPSRO) Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) temperature data from November 2006 to December 2010. We studied the seasonal, latitudinal, and interannual variability of the westward-propagating 2-day wave coincident with zonal wave number 3 in both hemispheres in the altitude range of 20–60km. The Lomb–Scargle periodogram (LSP) analysis indicates the dominance of the QTDW in the USLM in both the hemispheres. The observed amplitude of the wave is maximum during the winter season in middle and higher latitudes, with monthly mean amplitudes being as high as ∼8K. These amplitudes are found frequently during the late fall and peak to a maximum in the NH winter season. In the SH, QTDW amplitudes are found in the early winter season and appear till the early fall months. The QTDW varies from 49±3 to 48±1h in the NH and SH, respectively, with westward-propagating wave number 3. The amplitudes of the wave are large during winter in both the hemispheres, and, comparatively, the NH amplitudes are larger than those of the SH in higher latitudes.

Clinical Trial to Evaluate the Safety and Immunogenicity of a Trivalent Surface Antigen Seasonal Influenza Vaccine Produced in Mammalian Cell Culture and Administered to Young and Elderly Adults with and without A(H1N1) Pre-Vaccination

Vaccination against influenza is an important means of reducing morbidity and mortality in subjects at risk. The prevalent viral strains responsible for seasonal epidemics usually change annually, but the WHO recommendations for the 2011/2012-season in the Northern hemisphere included the same antigens as for the previous season.We conducted a single-center, single-arm study involving 62 younger (18–60 years) and 64 older (>60 years) adults to test the immunogenicity, safety and tolerability of a trivalent surface antigen, inactivated influenza vaccine produced in mammalian cell-culture. The vaccine contained 15 µg hemagglutinin of each of the virus strains recommended for the 2011–2012 Northern hemisphere winter season (A/California/7/09 (H1N1)-; A/Perth/16/09 (H3N2)-; B/Brisbane/60/08-like strain) in a non-adjuvanted preservative-free formulation. Antibody response was measured by hemagglutination inhibition 21 days after immunization. Adverse events and safety were assessed using subject diary cards and telephone interviews.Seroconversion or a 4-fold antibody increase in antibody titers was detectable against A(H1N1) in 68% of both younger and older adults, against A(H3N2) in 53% and 27%, and against the B influenza strain in 35% and 17%. Antibody titers of 40 or more were observed against A(H1N1) in 87% and 90% of younger and older adults, against A(H3N2) in 98% and 98%, and against the B influenza strain in 93% and 90%. Pre-vaccination antibody titers were protective against A(H1N1), A(H3N2) and B in 38%, 58% and 58%, respectively, of younger and in 43%, 88% and 70% of older adults. Among subjects with previous A(H1N1) vaccination only 48% of younger and 47% of older adults had protective A(H1N1) antibodies at inclusion. Adverse reactions were generally mild. The most frequently reported reactions were pain at the injection site, myalgia and fatigue.The vaccine generated protective antibodies against all three viral strains and had an acceptable safety profile in both younger and older adults.Trial Registration ClinicalTrials.gov NCT01422512