Phase Shift Between Age-Specific COVID-19 Incidence Curves Points to a Potential Epidemic Driver Function of Kids and Juveniles in Germany

Mutual phase shifts between three German COVID-19 incidence curves corresponding to the age classes of children, juveniles and adults, respectively, are calculated by means of delay-cross-correlations. At the country level, a phase shift of -5 weeks during the first half of the epidemic between the incidence curves corresponding to the juvenile age class and the curve corresponding to the adult class is observed. The children's incidence curve is shifted by -3 weeks with respect to the adults' curve. On the regional level of the 411 German districts (Landkreise) the distributions of observed time lags are inclined towards negative values. Regarding the incidence time series of the juvenile sub-population, 20% of the German districts exhibit negative phase shifts and only 3% show positive shifts versus the incidence curves of the adult sub-population. Similarly for the children with 6% positive shifts. Thus, children's and juveniles' epidemic activity is ahead of the adults' activity. The correlation coefficients of shifted curves are large (> 0.9 for juveniles versus adults on the country level) which indicates that aside from the phase shift the sub-populations follow a similar epidemic dynamics. Negative phase shifts of the children's incidence curves during the first and second epidemic waves are predictors for high incidences during the current fourth wave with respect to the corresponding districts.

Influence of the Madden–Julian Oscillation on the Arctic Oscillation Prediction in S2S Operational Models

The connections between the Madden–Julian Oscillation (MJO) and the Arctic Oscillation (AO) are examined in both observations and model forecasts. In the observations, the time-lag composites are carried out for AO indices and anomalies of 1,000-hPa geopotential height after an active or inactive initial MJO. The results show that when the AO is in its positive (negative) phase at the initial time, the AO activity is generally enhanced (weakened) after an active MJO. Reforecast data of the 11 operational global circulation models from the Sub-seasonal to Seasonal (S2S) Prediction Project are further used to examine the relationship between MJO activity and AO prediction. When the AO is in its positive phase on the initial day of the S2S prediction, an initial active MJO can generally improve the AO prediction skill in most of the models. This is consistent with results found in the observations that a leading MJO can enhance the AO activity. However, when the AO is in its negative phase, the relationship between the MJO and AO prediction is not consistent among the 11 models. Only a few S2S models provide results that agree with the observations. Furthermore, the S2S prediction skill of the AO is examined in different MJO phases. There is a significantly positive relationship between the MJO-related AO activity and the AO prediction skill. When the AO activity is strong (weak) in an MJO phase, including the inactive MJO, the models tend to have a high (low) AO prediction skill. For example, no matter what phase the initial AO is in, the AO prediction skill is generally high in MJO phase 7, in which the AO activity is generally strong. Thus, the MJO is an important predictability source for the AO forecast in the S2S models.

Noninvasive Optical Measurements of Dynamic Cerebral Autoregulation by Inducing Oscillatory Cerebral Hemodynamics

Objective: Cerebral autoregulation limits the variability of cerebral blood flow (CBF) in the presence of systemic arterial blood pressure (ABP) changes. Monitoring cerebral autoregulation is important in the Neurocritical Care Unit (NCCU) to assess cerebral health. Here, our goal is to identify optimal frequency-domain near-infrared spectroscopy (FD-NIRS) parameters and apply a hemodynamic model of coherent hemodynamics spectroscopy (CHS) to assess cerebral autoregulation in healthy adult subjects and NCCU patients.Methods: In five healthy subjects and three NCCU patients, ABP oscillations at a frequency around 0.065 Hz were induced by cyclic inflation-deflation of pneumatic thigh cuffs. Transfer function analysis based on wavelet transform was performed to measure dynamic relationships between ABP and oscillations in oxy- (O), deoxy- (D), and total- (T) hemoglobin concentrations measured with different FD-NIRS methods. In healthy subjects, we also obtained the dynamic CBF-ABP relationship by using FD-NIRS measurements and the CHS model. In healthy subjects, an interval of hypercapnia was performed to induce cerebral autoregulation impairment. In NCCU patients, the optical measurements of autoregulation were linked to individual clinical diagnoses.Results: In healthy subjects, hypercapnia leads to a more negative phase difference of both O and D oscillations vs. ABP oscillations, which are consistent across different FD-NIRS methods and are highly correlated with a more negative phase difference CBF vs. ABP. In the NCCU, a less negative phase difference of D vs. ABP was observed in one patient as compared to two others, indicating a better autoregulation in that patient.Conclusions: Non-invasive optical measurements of induced phase difference between D and ABP show the strongest sensitivity to cerebral autoregulation. The results from healthy subjects also show that the CHS model, in combination with FD-NIRS, can be applied to measure the CBF-ABP dynamics for a better direct measurement of cerebral autoregulation.

Late-Holocene Climate Variability in Southern New Zealand: A reconstruction of regional climate from an annually laminated sediment sequence from Lake Ohau

<p>This research aims to improve understanding of synoptic climate systems influencing southern New Zealand and document changes in the intensity and frequency of these systems beyond the historical record by analyzing a 1,350-year annually laminated sediment sequence recovered from Lake Ohau, South Island, New Zealand (44.234°S, 169.854°E). Climatological patterns originating in both the tropics (El-Niño-Southern Oscillation (ENSO), Interdecadal Pacific Oscillation (IPO)) and in the Antarctic (Southern Annular Mode (SAM)) influence year-to-year variability in New Zealand’s climate (e.g. temperature and precipitation). However, the range of natural variability of these systems in the southwest Pacific over time is poorly known because the instrumental record is short (~100 years). The high-resolution record from Lake Ohau offers a unique opportunity to investigate changes in regional hydrology and climate, and to also explore connections to large-scale climate patterns over the last millennium. Hydrodynamic and hydroclimatic processes that influence and control the production, transport, and deposition of sediment within the Lake Ohau catchment are examined and constrained in order to develop a robust climate record. A key aim is to determine the role that meteorology and climate play in controlling sediment flux. The physical properties and facies of a 5.5-meter-long Lake Ohau sediment core are analyzed using thin-sections, high-resolution X-radiographs scans, and particle-size analyses. Time-series analysis is used to establish links between varve facies, hydroclimate variability and regional synoptic climate types over the instrumental record. Utilizing this climate-proxy relationship, inflow conditions are reconstructed over the last 1,350 years and compared with regional temperature reconstructions to generate a Western South Island paleo-atmospheric circulation index. Relationship between this paleocirculation index and other proxy reconstructions show significant variability in the relative forcing of tropical (ENSO) and Southern Hemisphere highlatitude (SAM) synoptic climate drivers on New Zealand and southwest Pacific climate. Overall, this work demonstrates that: a) the laminated sediments from Lake Ohau are varves and the formation of the annual stratigraphy is strongly controlled by lake hydrodynamics, in particular, thermal lake stratification; b) sediment stratigraphy reflects changes in austral warm period (December-May) inflow, enabling a highresolution reconstruction of hydroclimate over the last 1,350 years and; c) the generation of a paleocirculation index for the Western South Island points to significant changes between northerly or southerly dominated atmospheric conditions in southern New Zealand, particularly over the ‘Little Ice Age’ (1385-1710 AD). During this time, the strength of tropical teleconnections weakened and a strong negative phase SAM persisted. Comparison with high-resolution regional proxy records from Antarctica and the Central Pacific point to significant regional coherence with a strong negative phase SAM acting as a primary driver of the onset of Little Ice Age conditions across the South Pacific.</p>

Late-Holocene Climate Variability in Southern New Zealand: A reconstruction of regional climate from an annually laminated sediment sequence from Lake Ohau

<p>This research aims to improve understanding of synoptic climate systems influencing southern New Zealand and document changes in the intensity and frequency of these systems beyond the historical record by analyzing a 1,350-year annually laminated sediment sequence recovered from Lake Ohau, South Island, New Zealand (44.234°S, 169.854°E). Climatological patterns originating in both the tropics (El-Niño-Southern Oscillation (ENSO), Interdecadal Pacific Oscillation (IPO)) and in the Antarctic (Southern Annular Mode (SAM)) influence year-to-year variability in New Zealand’s climate (e.g. temperature and precipitation). However, the range of natural variability of these systems in the southwest Pacific over time is poorly known because the instrumental record is short (~100 years). The high-resolution record from Lake Ohau offers a unique opportunity to investigate changes in regional hydrology and climate, and to also explore connections to large-scale climate patterns over the last millennium. Hydrodynamic and hydroclimatic processes that influence and control the production, transport, and deposition of sediment within the Lake Ohau catchment are examined and constrained in order to develop a robust climate record. A key aim is to determine the role that meteorology and climate play in controlling sediment flux. The physical properties and facies of a 5.5-meter-long Lake Ohau sediment core are analyzed using thin-sections, high-resolution X-radiographs scans, and particle-size analyses. Time-series analysis is used to establish links between varve facies, hydroclimate variability and regional synoptic climate types over the instrumental record. Utilizing this climate-proxy relationship, inflow conditions are reconstructed over the last 1,350 years and compared with regional temperature reconstructions to generate a Western South Island paleo-atmospheric circulation index. Relationship between this paleocirculation index and other proxy reconstructions show significant variability in the relative forcing of tropical (ENSO) and Southern Hemisphere highlatitude (SAM) synoptic climate drivers on New Zealand and southwest Pacific climate. Overall, this work demonstrates that: a) the laminated sediments from Lake Ohau are varves and the formation of the annual stratigraphy is strongly controlled by lake hydrodynamics, in particular, thermal lake stratification; b) sediment stratigraphy reflects changes in austral warm period (December-May) inflow, enabling a highresolution reconstruction of hydroclimate over the last 1,350 years and; c) the generation of a paleocirculation index for the Western South Island points to significant changes between northerly or southerly dominated atmospheric conditions in southern New Zealand, particularly over the ‘Little Ice Age’ (1385-1710 AD). During this time, the strength of tropical teleconnections weakened and a strong negative phase SAM persisted. Comparison with high-resolution regional proxy records from Antarctica and the Central Pacific point to significant regional coherence with a strong negative phase SAM acting as a primary driver of the onset of Little Ice Age conditions across the South Pacific.</p>

Approaching of May maximum surface air temperature to characteristic summer season for Baghdad city

Seasonal variability is the complex non-linear response of the physical climate system. There are two types of natural variability: those external and internal to the climate system. In any given season, natural variability may cause the climate to be different than its long-term average. This study examines with the seasonal variation of the maximum temperatures during the summer season. In addition, the maximum temperatures in May become close to the characteristics of the summer season. The monthly data for maximum temperature of May, June and July were used from Iraqi Meteorological Organization and Seismology (IMOS) for 47 years from 1970 to 2017 for Baghdad city. This period was long enough to estimate the range of approaching maximum temperature (Tmax) May to summer. Results revealed a significant Tmax for Baghdad during the second period (1992–2017) and ‎shown similar behavior of Tmax in May to June and July; on the contrary that first period (1970–1991). In second period, two phases have been found out, positive phase and negative phase. The positive phase were happened in 1995, 1999, and 2006, and the negative phase was four cases (1992, 2004, 2013, and 2016), while a few cases recorded in first period. The amplitudes of monthly variability had same distance of leaner correlation especially in 1999 and 2013 that represent coherent wave with summer seasons. The variance difference for Tmax between May and June approximately was 2°C for second study’s period, while exceed this range in first period. This variance change to 7.5°C when found difference between July and May.

Wind-SST Dipole Mode in the Caribbean and Gulf of Mexico: Large-Scale Features and Drivers

The Dipole Mode (DM) is the leading pattern of springtime wind-SST coupled interannual variability in the Intra-Americas Seas, characterized by SST anomalies of opposite sign between the Caribbean Sea and the Gulf of Mexico. Using the standard deviation (STD) of the wind in a Maximum Correlation Analysis (MCA), this study aims to provide a more dynamic view of the role of the atmosphere in its coupling with the SST. The MCA reveals that the positive phase of the DM is associated with an increase in atmospheric instability, while the negative phase emerges under more stable atmospheric conditions. The DM is preceded by changes in the subtropical high-pressure belt during the previous winter, particularly in the North Atlantic Subtropical High (NASH), and reflects shifts in the latitudinal position of the subtropical jet stream. The DM positive phase tends to occur after an El Niño winter, under negative North Atlantic Oscillation (NAO) conditions. El Niño modulates the DM through a weakening in the meridional pressure gradient and a southward shift of the jet stream. A negative NAO implies a weaker NASH and, therefore, a more irregular circulation over the region. Both El Niño and negative NAO conditions favor the increase in wind STD during the DM positive phase, consistent with an increment in atmospheric disturbances. The DM negative phase responds more to a positive NAO in the previous winter, revealing a stronger NASH acting as an atmospheric block, which justifies the decrease in STD and a more stable circulation.

Influence of the North Atlantic Oscillation on the Winter Season in Cuba

There have been several advances in understanding the North Atlantic Oscillation (NAO), but there are still uncertainties regarding its level of influence on the tropical climate. That is why this work determines the influence of the NAO on the main hydrometeorological events that affected Cuba in the 1999–2016 period. To comply with this, a regression analysis is carried out in the CurveExpert software where the combined influence of the NAO and El Niño-Southern Oscillation on hydrometeorological events is also examined. It was found that the NAO exerts a greater influence on Cuba when it is in its negative phase during the winter season.

P322 Hepatitis B reactivation under biologic therapy in patients with HBsAg negative phase of chronic HBV infection

Background Biologic agents are widely used in immune mediated inflammatory diseases (IMID). The risk and consequences of hepatitis B reactivation in hepatitis B surface antigen (HBsAg) negative phase of hepatitis B virus (HBV) exposed patients is not clear. We aim to investigate the reactivation rate in biologic exposed patients within surface antigen negative phase of HBV infection. Methods We identified patients followed up at gastroenterology, rheumatology and dermatology out-patient clinics with a diagnosis of IMID from clinical charts. Patients exposed to biologic agents with a negative HBsAg and positive Anti-HBc IgG were included. Primary outcome was HBV reactivation, which was defined as reverse seroconversion of HBsAg. Results We screened 8266 IMID patients and 2484 of them were exposed to biologic agents. A total of 221 patients were included in the study. The mean age was 54.08 ± 11.69 years and 115 (52.0%) patients were female. The median number of different biologic subtype use was 1 (range: 1 – 6). The mean biologic agent exposure time was 55 (range: 2 – 179) months. One hundred and fifty-two (68.8%) patients were using concomitant immunomodulatory agents and 84 (38.0%) patients were exposed to corticosteroids during biologic use. No hepatitis B reactivation with a reverse seroconversion of HBsAg positivity was observed in the whole cohort. Antiviral prophylaxis for hepatitis B was given to 48 (21.7%) patients with entecavir, tenofovir or lamivudine. HBV-DNA was screened in 56 (25.3%) patients prior to the biologic exposure. Two patients had HBV-DNA reactivation with a negative HBsAg during exposure to the biologic agent. Conclusion Though only 21.7% of our patients used prophylaxis, we found only two reactivations (1%) and no HBsAg seroconversion in our cohort. Our results suggest a re-assessment of antiviral prophylaxis for anti-HBc Ag (+) patients exposed to biologic agents. Current guidelines would be updated in the light of future studies.