A New Multilocus Sequence Typing Scheme and Its Application for the Characterization of Photobacterium damselae subsp. damselae Associated with Mortality in Cetaceans

Photobacterium damselae subsp. damselae (PDD) is a known pathogen of fish, humans and marine mammals. In this study, a Multilocus Sequence Typing (MLST) scheme based on six housekeeping genes (glp, gyrB, metG, pnt, pyrC and toxR) was developed to better understand the PDD population structure and used to type 73 PDD isolates from cetaceans, mainly striped dolphins (Stenella coeruleoalba) involved in mortality episodes, and from a few marine chelonians. Five reference ATCC strains were also included in the study. Typing allowed the discrimination of groups of PDD strains isolated from different host species, at different times and from different geographic areas, suggesting that a clonal PDD group may have spread in the Tyrrhenian sea at the time of an Unusual Mortality Event (UME) among cetaceans, mainly striped dolphins, occurred in early 2013 along the Italian western coasts

Why the South Pacific Convergence Zone is diagonal

During austral summer, the majority of precipitation over the Pacific Ocean is concentrated in the South Pacific Convergence Zone (SPCZ). The surface boundary conditions required to support the diagonally (northwest-southeast) oriented SPCZ are determined through a series of experiments with an atmospheric general circulation model. Continental configuration and orography do not have a significant influence on SPCZ orientation and strength. The key necessary boundary condition is the zonally asymmetric component of the sea surface temperature (SST) distribution. This leads to a strong subtropical anticyclone over the southeast Pacific that, on its western flank, transports warm moist air from the equator into the SPCZ region. This moisture then intensifies (diagonal) bands of convection that are initiated by regions of ascent and reduced static stability ahead of the cyclonic vorticity in Rossby waves that are refracted toward the westerly duct over the equatorial Pacific. The climatological SPCZ is comprised of the superposition of these diagonal bands of convection. When the zonally asymmetric SST component is reduced or removed, the subtropical anticyclone and its associated moisture source is weakened. Despite the presence of Rossby waves, significant moist convection is no longer triggered; the SPCZ disappears. The diagonal SPCZ is robust to large changes (up to +/-6 degC) in absolute SST (i.e. where the SST asymmetry is preserved). Extreme cooling (change less than -6 degC) results in a weaker and more zonal SPCZ, due to decreasing atmospheric temperature, moisture content and convective available potential energy

A dynamical framework for the origin of the diagonal South Pacific and South Atlantic convergence zones

The South Pacific Convergence Zone (SPCZ) and South Atlantic Convergence Zone (SACZ) are diagonal bands of precipitation that extend from the equator southeastward into the Southern Hemisphere over the western Pacific and Atlantic Oceans, respectively. With mean precipitation rates over 5 mm day−1, they are a major component of the tropical and global climate in austral summer. However, their basic formation mechanism is not fully understood. Here, a conceptual framework for the diagonal convergence zones is developed, based on calculations of the vorticity budget from reanalysis and Rossby wave theory. Wave trains propagate eastward along the Southern Hemisphere subtropical jet, with initially quasi-circular vorticity centres. In the zonally sheared environment on the equatorward flank of the jet, these vorticity centres become elongated and develop a northwest-southeast tilt. Ray tracing diagnostics in a non-divergent, barotropic Rossby wave framework then explain the observed equatorward propagation of these diagonal vorticity structures toward the westerly ducts over the equatorial Pacific and Atlantic. The baroclinic component of these circulations leads to destabilisation and ascent ahead of the cyclonic vorticity anomaly in the wave, triggering deep convection because of the high sea surface temperatures in this region. Latent heat release then forces additional ascent and strong upper-tropospheric divergence, with an associated anticyclonic vorticity tendency. A vorticity budget shows that this cancels out the advective cyclonic vorticity tendency in the wave train over the SPCZ, and dissipates the wave within a day. The mean SPCZ is consequently comprised of the sum of these pulses of diagonal bands of precipitation. Similar mechanisms also operate in the SACZ. However, the vorticity anomalies in the wave trains are stronger, and the precipitation and negative feedback from the divergence and anticyclonic vorticity tendency are weaker, resulting in continued propagation of the wave and a more diffuse diagonal convergence zone

Characterization of the Vertical Structure of Latent Heating in the East Pacific ITCZ Using the TRMM PR and CLOUDSAT CPR

In the East Pacific intertropical convergence zone (ITCZ), Tropical Rainfall Measuring Mission (TRMM) radar-based latent heating retrievals suggest a top-heavy structure; however, the TRMM precipitation radar (PR) underestimates light precipitation (< 0.4 mm h?1) from shallow convection and the low-level latent heating associated with this precipitation. Thus, this study uses observations of stratiform and deep convective precipitation from the TRMM PR and shallow precipitation from the more sensitive CloudSat cloud profiling radar (CPR) to assess the seasonal vertical structure of latent heating in the East Pacific ITCZ for 1998-2015. This study is complemented with three reanalysis datasets (MERRA2, ERA-Interim, and NCEP NCAR) to analyze the meridional circulation changes linked to variations in the ITCZ heating profiles. There is a distinct seasonal cycle in the TRMM/CloudSat latent heating profiles in the East Pacific ITCZ. During DJF, latent heating peaks around 850 hPa because of the predominance of rain from shallow convection. The heating peak rises to 700 hPa during MAM as the contribution from deep convective rain increases along with the presence of a mid-level inflow south the ITCZ. During JJA and SON, stratiform precipitation increases significantly and heating is more equally distributed throughout the troposphere with double peaks at 700 and 400 hPa; the lower peak is related to the strong shallow overturning circulation. In addition, the East Pacific has a meridional slope in latent heating throughout the year as a result of the prevalence of shallow convection in the southern part of the ITCZ and deep convection in the northern part of the ITCZ. This slope is weakest during MAM when a double ITCZ structure exists. Reanalyses only capture certain aspects of this seasonal cycle in the East Pacific ITCZ. While the reanalyses agree that the most bottomheavy heating occurs in DJF and the most top-heavy heating occurs in JJA, they greatly underestimate the amount of heating aloft compared to the satellite retrievals throughout the year. This disagreement has serious implications for how the meridional circulation is captured in this region with reanalyses showing varying ability in representing the shallow meridional circulation and deeper Hadley cell overturning in the East Pacific

Ocean Rossby waves as a triggering mechanism for primary Madden-Julian events

The Madden–Julian Oscillation (MJO) is sporadic, with episodes of cyclical activity interspersed with inactive periods. However, it remains unclear what may trigger a Madden–Julian (MJ) event which is not immediately preceded by any MJO activity: a ‘primary’ MJ event. A combination of case-studies and composite analysis is used to examine the extent to which the triggering of primary MJ events might occur in response to ocean dynamics. The case-studies show that such events can be triggered by the arrival of a downwelling oceanic equatorial Rossby wave, which is shown to be associated with a deepening of the mixed layer and positive sea-surface temperature (SST) anomalies of the order of 0.5–1 °C. These SST anomalies are not attributable to forcing by surface fluxes which are weak for the case-studies analysed. Furthermore, composite analysis suggests that such forcing is consistently important for triggering primary events. The relationship is much weaker for successive events, due to the many other triggering mechanisms which operate during periods of cyclical MJO activity. This oceanic feedback mechanism is a viable explanation for the sporadic and broadband nature of the MJO. Additionally, it provides hope for forecasting MJ events during periods of inactivity, when MJO forecasts generally exhibit low skill

A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation

We present a new discrete chemo-dynamical axisymmetric modeling technique, which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement over previous Jeans models is that realistic chemical distributions are included directly in the dynamical modelling of the discrete data. This avoids loss of information due to spatial binning and eliminates the need for hard cuts to remove contaminants and to separate stars based on their chemical properties. Using a combined likelihood in position, metallicity and kinematics, we find that our models naturally separate Sculptor stars into a metal-rich and a metal-poor population. Allowing for non-spherical symmetry, our approach provides a central slope of the dark matter density of $\gamma = 0.5 \pm 0.3$. The metal-rich population is nearly isotropic (with $\beta_r^{red} = 0.0\pm0.1$) while the metal-poor population is tangentially anisotropic (with $\beta_r^{blue} = -0.2\pm0.1$) around the half light radius of $0.26$ kpc. A weak internal rotation of the metal-rich population is revealed with $v_{max}/\sigma_0 = 0.15 \pm 0.15$. We run tests using mock data to show that a discrete dataset with $\sim 6000$ stars is required to distinguish between a core ($\gamma = 0$) and cusp ($\gamma = 1$), and to constrain the possible internal rotation to better than $1\,\sigma$ confidence with our model. We conclude that our discrete chemo-dynamical modelling technique provides a flexible and powerful tool to robustly constrain the internal dynamics of multiple populations, and the total mass distribution in a stellar system.Comment: Accepted by MNRA

Seasonal modulation of the Asian summer monsoon between the Medieval Warm Period and Little Ice Age: a multi model study

Instrumental and proxy records indicate remarkable global climate variability over the last millennium, influenced by solar irradiance, Earth’s orbital parameters, volcanic eruptions and human activities. Numerical model simulations and proxy data suggest an enhanced Asian summer monsoon during the Medieval Warm Period (MWP) compared to the Little Ice Age (LIA). Using multiple climate model simulations, we show that anomalous seasonal insolation over the Northern Hemisphere due to a long cycle of orbital parameters results in a modulation of the Asian summer monsoon transition between the MWP and LIA. Ten climate model simulations prescribing historical radiative forcing that includes orbital parameters consistently reproduce an enhanced MWP Asian monsoon in late summer and a weakened monsoon in early summer. Weakened, then enhanced Northern Hemisphere insolation before and after June leads to a seasonally asymmetric temperature response over the Eurasian continent, resulting in a seasonal reversal of the signs of MWP–LIA anomalies in land–sea thermal contrast, atmospheric circulation, and rainfall from early to late summer. This seasonal asymmetry in monsoon response is consistently found among the different climate models and is reproduced by an idealized model simulation forced solely by orbital parameters. The results of this study indicate that slow variation in the Earth’s orbital parameters contributes to centennial variability in the Asian monsoon transition

Evaluation and modeling of synergy to pheromone and plant kairomone in American palm weevil

Background: Many behavioral responses to odors are synergistic, particularly in insects. In beetles, synergy often involves a pheromone and a plant odor, and pest management relies on them for the use of combined lures. To investigate olfactory synergy mechanisms, we need to distinguish synergistic effects from additive ones, when all components of the mixture are active. Results: As versatile tools and procedures were not available, we developed a bioassay, and a mathematical model to evaluate synergy between aggregation pheromone (P) and host plant odors (kairomone: K) in the American palm weevil, a pest insect showing enhanced responses to P+K mixtures. Responses to synthetic P and natural K were obtained using a 4-arm olfactometer coupled to a controlled volatile delivery system. We showed that: (1) Response thresholds were ca. 10 and 100 pg/s respectively for P and K. (2) Both stimuli induced similar maximum response. (3) Increasing the dose decreased the response for P to the point of repellence and maintained a maximum response for K. (4) P and K were synergistic over a 100-fold range of doses with experimental responses to P+K mixtures greater than the ones predicted assuming additive effects. Responses close to maximum were associated with the mixture amounts below the response threshold for both P and K. Conclusion: These results confirm the role of olfactory synergy in optimizing active host-plant localization by phytophagous insects. Our evaluation procedure can be generalized to test synergistic or inhibitory integrated responses of various odor mixtures for various insects

Northern hemisphere stationary waves in a changing climate

AbstractPurpose of ReviewStationary waves are planetary-scale longitudinal variations in the time-averaged atmospheric circulation.Here, we consider the projected response of Northern Hemisphere stationary waves to climate change in winter and summer. Wediscuss how the response varies across different metrics, identify robust responses, and review proposed mechanisms.Recent FindingsClimate models project shifts in the prevailing wind patterns, with corresponding impacts on regional precip-itation, temperature, and extreme events. Recent work has improved our understanding of the links between stationary waves andregional climate and identified robust stationary wave responses to climate change, which include an increased zonal lengthscalein winter, a poleward shift of the wintertime circulation over the Pacific, a weakening of monsoonal circulations, and an overallweakening of stationary wave circulations, particularly their divergent component and quasi-stationary disturbances.SummaryNumerous factors influence Northern Hemisphere stationary waves, and mechanistic theories exist for only a fewaspects of the stationary wave response to climate change. Idealized studies have proven useful for understanding the climateresponses of particular atmospheric circulation features and should be a continued focus of future research.R.C.J.W. received funding from the TamakiFoundation, NSF (Grant AGS-1929775), and NASA (GrantNNX17AH56G). R.H.W. received funding from the European UnionHorizon 2020 research and innovation programme under the MarieSkłodowska-Curie grant agreement No. 797961. XJL received fundingfrom the European Union Horizon 2020 research and innovation pro-gramme under the Marie Skłodowska-Curie grant agreement No.754433.Peer ReviewedPostprint (published version