A Quantum Rosetta Stone for Interferometry

Heisenberg-limited measurement protocols can be used to gain an increase in measurement precision over classical protocols. Such measurements can be implemented using, e.g., optical Mach-Zehnder interferometers and Ramsey spectroscopes. We address the formal equivalence between the Mach-Zehnder interferometer, the Ramsey spectroscope, and the discrete Fourier transform. Based on this equivalence we introduce the ``quantum Rosetta stone'', and we describe a projective-measurement scheme for generating the desired correlations between the interferometric input states in order to achieve Heisenberg-limited sensitivity. The Rosetta stone then tells us the same method should work in atom spectroscopy.Comment: 8 pages, 4 figure

ON THE INTERACTION BETWEEN SEA BREEZE AND SUMMER MISTRAL AT THE EXIT OF THE RHÔNE VALLEY DURING THE ESCOMPTE EXPERIMENT

The abstract investigates experimentally and numerically the structure of a combined Mistral sea breeze event at the exit of the Rhône valley in southeastern France, as well as the near shoreline water variability at the alternation between the Mistral and the sea breeze

Evaluating model simulations of twentieth-century sea-level rise. Part II: regional sea-level changes

Twentieth-century regional sea level changes are estimated from 12 climate models from phase 5 of the Climate Model Intercomparison Project (CMIP5). The output of the CMIP5 climate model simulations was used to calculate the global and regional sea level changes associated with dynamic sea level, atmospheric loading, glacier mass changes, and ice sheet surface mass balance contributions. The contribution from groundwater depletion, reservoir storage, and dynamic ice sheet mass changes are estimated from observations as they are not simulated by climate models. All contributions are summed, including the glacial isostatic adjustment (GIA) contribution, and compared to observational estimates from 27 tide gauge records over the twentieth century (1900–2015). A general agreement is found between the simulated sea level and tide gauge records in terms of interannual to multidecadal variability over 1900–2015. But climate models tend to systematically underestimate the observed sea level trends, particularly in the first half of the twentieth century. The corrections based on attributable biases between observations and models that have been identified in Part I of this two-part paper result in an improved explanation of the spatial variability in observed sea level trends by climate models. Climate models show that the spatial variability in sea level trends observed by tide gauge records is dominated by the GIA contribution and the steric contribution over 1900–2015. Climate models also show that it is important to include all contributions to sea level changes as they cause significant local deviations; note, for example, the groundwater depletion around India, which is responsible for the low twentieth-century sea level rise in the region

The Open Global Glacier Model (OGGM) v1.1

Despite their importance for sea-level rise, seasonal water availability, and as a source of geohazards, mountain glaciers are one of the few remaining subsystems of the global climate system for which no globally applicable, open source, community-driven model exists. Here we present the Open Global Glacier Model (OGGM), developed to provide a modular and open-source numerical model framework for simulating past and future change of any glacier in the world. The modeling chain comprises data downloading tools (glacier outlines, topography, climate, validation data), a preprocessing module, a mass-balance model, a distributed ice thickness estimation model, and an ice-flow model. The monthly mass balance is obtained from gridded climate data and a temperature index melt model. To our knowledge, OGGM is the first global model to explicitly simulate glacier dynamics: the model relies on the shallow-ice approximation to compute the depth-integrated flux of ice along multiple connected flow lines. In this paper, we describe and illustrate each processing step by applying the model to a selection of glaciers before running global simulations under idealized climate forcings. Even without an in-depth calibration, the model shows very realistic behavior. We are able to reproduce earlier estimates of global glacier volume by varying the ice dynamical parameters within a range of plausible values. At the same time, the increased complexity of OGGM compared to other prevalent global glacier models comes at a reasonable computational cost: several dozen glaciers can be simulated on a personal computer, whereas global simulations realized in a supercomputing environment take up to a few hours per century. Thanks to the modular framework, modules of various complexity can be added to the code base, which allows for new kinds of model intercomparison studies in a controlled environment. Future developments will add new physical processes to the model as well as automated calibration tools. Extensions or alternative parameterizations can be easily added by the community thanks to comprehensive documentation. OGGM spans a wide range of applications, from ice–climate interaction studies at millennial timescales to estimates of the contribution of glaciers to past and future sea-level change. It has the potential to become a self-sustained community-driven model for global and regional glacier evolution.</p

Assimilation of water vapour airborne lidar observations: Impact study on the COPS precipitation forecasts

The Convective and Orographically-driven Precipitation Study (COPS) carried out in summer 2007 over northeastern France and southwestern Germany provided a fairly comprehensive description of the low-troposphere water-vapour field, thanks in particular to the deployment of two airborne differential absorption lidar systems. These lidar observations were assimilated using the 3D-Var assimilation system of the Application of Research to Operations at MEsoscale (AROME) numerical weather prediction mesoscalemodel. The assimilation was carried out for the period 4 July�3 August by running a three-hour forward intermittent assimilation cycle. First, the impact of the lidar observations was assessed by comparing the analyses with a set of more than 200 independent soundings. The lidar observations were found to have a positive impact on the analyses by reducing the dry bias in the first 500 m above ground level and by diminishing the root-mean-square error by roughly 15% in the first km. Then the impact of the lidar observations was assessed by comparing the precipitation forecasts (obtained with and without the lidar observations for the period 15 July�2 August) with the gridded precipitation observations provided by the Vienna Enhanced Resolution Analysis. In general, the impact was found to be positive but not significant for the 24 h precipitation and positive and significant for the 6 h precipitation, with an improvement lasting up to 24 h. Some selected case studies show that the improvement was obtained through a better depiction of convection initiation or through a more accurate positioning of the precipitation systems

Monitoring Saturation Changes with Ambient Seismic Noise and Gravimetry in a Karst Environment

On a heterogeneous karstic site in the Larzac plateau (France), we performed cross-correlations of ambient seismic noise recorded at two broadband seismometers to obtain daily seismic velocity changes. Rayleigh velocity changes at the 6- to 8-Hz frequency band show variations of ±0.2% over 1 yr. Assuming a simple velocity profile, changes are expected to come from depths of tens of meters. Therefore velocity changes at 6 to 8 Hz were interpreted as induced by water saturation changes. A slow infiltration rate would explain the delay of several months between the rainy season (November) and the minimum velocity (June). Superconducting gravimeter, evapotranspiration, and magnetic resonance sounding (MRS) measurements were then combined with seismic data in one-dimensional physical simulations. Velocity changes clearly constrain hydrological parameters, like saturated hydraulic conductivity, even if the Biot–Gassmann theory does not explain all of the amplitude observed. Nevertheless, this nondestructive method demonstrates great potential in hydrological model calibration. It overcomes the lack of depth resolution of gravimetry and the lack of temporal resolution of MRS. The combination of ambient seismic noise with gravimetry and MRS could fill the instrumental gap currently existing in hydrology for the study of deep and/or complex critical zones

Forecasting summer convection over the Black Forest: A case study from the Convective and Orographically-induced Precipitation Study (COPS) experiment

In the mid-afternoon of 15th July 2007, during the Convective and Orographically-induced Precipitation Study (COPS), in a very warm and dry environment, an isolated, short-lived, deep convective system developed over the southern Black-Forest. Most of the high-resolution, convection-permitting models involved in COPS were unable to capture this event whereas the Meso-NH forecast was quite skilful. To further assess the Meso-NH performance, the model results were carefully checked against the various and numerous COPS observations. In full agreement with clear-air radar observations, model results underlined the triggering role of a low-level level convergence line, which developed in the lee of the Feldberg. The main departure from the observations was found to be in the low-level moisture fields, which appeared significantly moister in the model than in the observations and also slightly moister than in the other models. Sensitivity studies showed that this departure from the observations was strongly controlled by the initial surface moisture conditions. When the surface moisture was reduced by 20% or replaced by the value derived from a different analysis, the evolution of the planetary boundary layer was more accurately represented while the storm evolution was still correctly captured. These results demonstate that the quality of the initial forecast cannot be ascribed to the moist bias of the model. It could therefore be hypothesized that the key parameters for a satisfactory forecast of this event lay more in the ability of the model to accurately reproduce the dynamical forcing than in the characteristics of the air-mass instability

Potential of shipborne GPS atmospheric delay data for prediction of Mediterranean intense weather events

International audienceHigh spatial and temporal variability of mesoscale moisture fields is still a challenge for quantitative precipitation forecast within numerical weather prediction (NWP) models especially over ocean regions where observations are lacking. This study presents the comparison between integrated water vapor over the Mediterranean Sea determined from shipborne GPS, the NWP ALADIN/Météo-France model and MODIS retrieval during a 4-month campaign (autumn 2008). While moisture prediction of the NWP remains accurate during most of the observation period, there are significant periods with offsets between GPS data and model predictions. We analyze such events and discuss the associated meteorological situation

Final scientific report of synthesis on territorial intelligence, deliverable 33 of caENTI, project funded under FP6 research program of the European Union.

deliverable 33 of caENT