Looking for a charge asymmetry in cosmic rays

We combine the data from PAMELA and FERMI-LAT cosmic ray experiments by introducing a simple sum rule. This allows to investigate whether the lepton excess observed by these experiments is charge symmetric or not. We also show how the data can be used to predict the positron fraction at energies yet to be explored by the AMS-02 experiment.Comment: Contribution to the proceedings of DISCRETE 2010, 5 pages, 2 figure

Phenomenological Consequences of Soft Leptogenesis

Soft supersymmetry breaking terms involving heavy singlet sneutrinos can be the dominant source of leptogenesis. The relevant range of parameters is different from standard leptogenesis: a lighter Majorana mass, M < 10^9 GeV (allowing a solution of the gravitino problem), and smaller Yukawa couplings, Y_N < 10^{-4}. We investigate whether the various couplings of the singlet sneutrinos, which are constrained by the requirement of successful `soft leptogenesis', can have observable phenomenological consequences. Specifically, we calculate the contributions of the relevant soft supersymmetric breaking terms to the electric dipole moments of the charged leptons and to lepton flavor violating decays. Our result is that these contributions are small.Comment: 11 pages, 1 figure; v2: an additional contribution is considered (modifying: fig. 1, eq. 10-13, 22) and a reference added. Conclusions unchange

Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC). Analy- sis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uni- form, 10◦ wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs) observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simu- late more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscilla- tions that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature. This study shows that the potential for baroclinic instabil- ity in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect

New Physics summary

We introduce the various contributions to the New Physics Session by identifying four main areas: Higgs-like signatures, supersymmetry, exotica and lepton flavour violation searches

The CMCC-INGV Global Ocean Data Assimilation System (CIGODAS)

This report summarizes the technical structure and main characteristics of the CMCCINGV Global Ocean Data Assimilation System (CIGODAS) based on a Reduced Order Optimal Interpolation scheme and a coarse resolution Global Ocean Model for the assimilation of temperature and salinity observations. It is intended to be a reference guide for new users who are interested in setting up and running an experiment using this approach and producing estimates of the timevarying, threedimensional state of the global ocean

Estimation and Impact of Nonuniform Horizontal Correlation Length Scales for Global Ocean Physical Analyses

Optimally modeling background-error horizontal correlations is crucial in ocean data assimilation. This paper investigates the impact of releasing the assumption of uniform background-error correlations in a global ocean variational analysis system. Spatially varying horizontal correlations are introduced in the recursive filter operator, which is used for modeling horizontal covariances in the Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC) analysis system. The horizontal correlation length scales (HCLSs) were defined on the full three-dimensional model space and computed from both a dataset of monthly anomalies with respect to the monthly climatology and through the so-called National Meteorological Center (NMC) method. Different formulas for estimating the correlation length scale are also discussed and applied to the two forecast error datasets. The new formulation is tested within a 12-yr period (2000–11) in the ½° resolution system. The comparison with the data assimilation system using uniform background-error horizontal correlations indicates the superiority of the former, especially in eddy-dominated areas. Verification skill scores report a significant reduction of RMSE, and the use of nonuniform length scales improves the representation of the eddy kinetic energy at midlatitudes, suggesting that uniform, latitude, or Rossby radius-dependent formulations are insufficient to represent the geographical variations of the background-error correlations. Furthermore, a small tuning of the globally uniform value of the length scale was found to have a small impact on the analysis system. The use of either anomalies or NMC-derived correlation length scales also has a marginal effect with respect to the use of nonuniform HCLSs. On the other hand, the application of overestimated length scales has proved to be detrimental to the analysis system in all areas and for all parameters

Impact of extreme CO2 levels on tropical climate: A CGCM study

A coupled general circulation model has been used to perform a set of experiments with high CO2 concentration (2, 4, 16 times the present day mean value). The experiments have been analyzed to study the response of the climate system to strong radiative forcing in terms of the processes involved in the adjustment at the ocean-atmosphere interface. The analysis of the experiments revealed a non-linear response of the mean state of the atmosphere and ocean to the increase in the carbon dioxide concentration. In the 16xCO2 experiment the equilibrium at the ocean-atmosphere interface is characterized by an atmosphere with a shut off of the convective precipitation in the tropical Pacific sector, associated with air warmer than the ocean below. A cloud feedback mechanism is found to be involved in the increased stability of the troposphere. In this more stable condition the mean total precipitation is mainly due to large-scale moisture flux even in the tropics. In the equatorial Pacific Ocean the zonal temperature gradient of both surface and sub-surface waters is significantly smaller in the 16xCO2 experiment than in the control experiment. The thermocline slope and the zonal wind stress decrease as well. When the CO2 concentration increases by about two and four times with respect to the control experiment there is an intensification of El Nino. On the other hand, in the experiment with 16 times the present-day value of CO2, the Tropical Pacific variability weakens, suggesting the possibility of the establishment of permanent warm conditions that look like the peak of El Nino

Skill assessment of the PELAGOS global ocean biogeochemistry model over the period 1980–2000

Global Ocean Biogeochemistry General Circulation Models are useful tools to study biogeochemical processes at global and large scales under current climate and future scenario conditions. The credibility of future estimates is however dependent on the model skill in capturing the observed multi-annual variability of firstly the mean bulk biogeochemical properties, and secondly the rates at which organic matter is processed within the food web. For this double purpose, the results of a multi-annual simulation of the global ocean biogeochemical model PELAGOS have been objectively compared with multi-variate observations from the last 20 years of the 20th century, both considering bulk variables and carbon production/consumption rates. Simulated net primary production (NPP) is comparable with satellite-derived estimates at the global scale and when compared with an independent data-set of in situ observations in the equatorial Pacific. The usage of objective skill indicators allowed us to demonstrate the importance of comparing like with like when considering carbon transformation processes. NPP scores improve substantially when in situ data are compared with modeled NPP which takes into account the excretion of freshly-produced dissolved organic carbon (DOC). It is thus recommended that DOC measurements be performed during in situ NPP measurements to quantify the actual production of organic carbon in the surface ocean. The chlorophyll bias in the Southern Ocean that affects this model as well as several others is linked to the inadequate representation of the mixed layer seasonal cycle in the region. A sensitivity experiment confirms that the artificial increase of mixed layer depths towards the observed values substantially reduces the bias. Our assessment results qualify the model for studies of carbon transformation in the surface ocean and metabolic balances. Within the limits of the model assumption and known biases, PELAGOS indicates a net heterotrophic balance especially in the more oligotrophic regions of the Atlantic during the boreal winter period. However, at the annual time scale and over the global ocean, the model suggests that the surface ocean is close to a weakly positive autotrophic balance in accordance with recent experimental findings and geochemical considerations

A process-oriented model study of equatorial Pacific phytoplankton: the role of iron supply and tropical instability waves

The response of phytoplankton growth to iron supply and its modulation by large-scale circulation and tropical instability waves (TIWs) in the eastern equatorial Pacific has been investigated with an ocean biogeochemical model. This process study shows that iron can be efficiently advected from the New Guinea shelf through the Equatorial Undercurrent (EUC) to the eastern Pacific. The presence of a continental iron source is necessary for the maintenance of the observed subsurface iron maximum in the EUC core. In the eastern Pacific region, phytoplankton production is enhanced when additional iron is available in the EUC. Simulated phytoplankton variability is linked to TIWs activity, as revealed by a wavelet analysis of the total autotrophic carbon. The net local effect of the waves on phytoplankton can be either positive or negative depending on several factors. When the iron nutricline is sufficiently shallow to be reached by the wave vertical scale, the effect of the waves is to enhance iron availability in the euphotic zone leading to a net local increase of phytoplankton biomass. We therefore suggest that the local maxima of phytoplankton observed in moorings off the Equator in the eastern Pacific might be not only the result of concentration mechanisms, but also the result of an increase in local production sustained by advected iron

Tropical Pacific - North Pacific teleconnection in a coupled GCM: Remote and local effects

The connection between Tropical Pacific and North Pacific variability is investigated in a state of the art coupled ocean-atmosphere model, comparing two twentieth century simulations at T30 and T106 atmospheric horizontal resolutions. Despite a better simulation of the frequency and the spatial distribution of the Tropical Pacific anomalies associated with the El Nino Southern Oscillation (ENSO) in the T106 experiment, the response in the North Pacific is scarcely different from the T30 experiment, where the ENSO variability is weaker and more frequent than observed. In both experiments, the weakness of the atmospheric teleconnection in the North Pacific can be related with the weaker than observed precipitation anomalies simulated in the tropical Pacific that act as a less effective vorticity source. The teleconnection as a response to the Rossby waves originating from the tropics appears to be affected by local coupling processes, likely induced by different atmospheric resolutions. The coupling occurring between sea level pressure (SLP) and SST in the North Pacific, as well as the influence of the Tropical Pacific SST, is measured by means of the “coupled manifold”. In the high-resolution experiment, the fraction of the SLP variances linked with the North Pacific SST “free” from the Tropics is comparable to the fraction due to the tropical Pacific SST. On the other hand, in the low-resolution case the SLP variances linked with the “free” North Pacific SST are weak and the regions where the coupling is stronger are somehow driven by the tropics, consistently with the observations. The results show that increasing the atmospheric horizontal resolution does not reduce the coupled model systematic errors in the representation of the teleconnection between the North and the Tropical Pacific. This suggests that the validation of coupled models have to consider separately remote and local processes