Cosmological Constraints from Moments of the Thermal Sunyaev-Zel'dovich Effect

In this paper, we explain how moments of the thermal Sunyaev-Zel'dovich (tSZ) effect can constrain both cosmological parameters and the astrophysics of the intracluster medium (ICM). As the tSZ signal is strongly non-Gaussian, higher moments of tSZ maps contain useful information. We first calculate the dependence of the tSZ moments on cosmological parameters, finding that higher moments scale more steeply with sigma_8 and are sourced by more massive galaxy clusters. Taking advantage of the different dependence of the variance and skewness on cosmological and astrophysical parameters, we construct a statistic, ||/^1.4, which cancels much of the dependence on cosmology (i.e., sigma_8) yet remains sensitive to the astrophysics of intracluster gas (in particular, to the gas fraction in low-mass clusters). Constraining the ICM astrophysics using this statistic could break the well-known degeneracy between cosmology and gas physics in tSZ measurements, allowing for tight constraints on cosmological parameters. Although detailed simulations will be needed to fully characterize the accuracy of this technique, we provide a first application to data from the Atacama Cosmology Telescope and the South Pole Telescope. We estimate that a Planck-like full-sky tSZ map could achieve a <1% constraint on sigma_8 and a 1-sigma error on the sum of the neutrino masses that is comparable to the existing lower bound from oscillation measurements.Comment: 11 pages, 12 figures, to be submitted to Phys. Rev. D; v2: 14 pages, 16 figures, matches PRD accepted version (changes from v1 include additional calculations with primordial non-Gaussianity and a new appendix discussing the tSZ kurtosis

The evolution and energetics of large amplitude nonlinear internal waves on the Portuguese shelf

Intensive in-situ observations of nonlinear internal waves on the Portuguese shelf were made in August 1994, including measurements of the same wavepacket at three locations as it propagated on-shelf. The waves were characterized by sudden isotherm depressions of up to 45 m lasting 10-35 minutes, accompanied by current surges of up to 0.45 m s-1 and shears of up to 0.7 m s-1 over 60 m. The waves propagated away from the shelf break with an estimated phase speed of 0.57 m s-1. The amplitude of the waves was comparable to the theoretical maximum. The kinetic and potential energies of the waves were calculated directly from the observed current and density structures. Individual waves were associated with a total energy of up to approximately 3.0 M J m-1 per unit crest length. The depth integrated on-shelf internal wave energy flux approached 2000 W m-1 per unit crest length near the shelf break and decreased on-shore at a depth integrated rate of approximately 7.7 × 10-2 W m-2. The internal waves provided an important source of vertical mixing where they occurred on the Portuguese shelf throughout most of August 1994, represented by a sustained vertical eddy diffusivity profile which peaked at Kz ≈ 2.2 × 10-3 m2 s-1 at 30 m depth. Internal mixing would have to be parameterized by such a Kz profile in any model of the Portuguese shelf in which the stratification were to be accurately represented

Monitored Energy Use Patterns in Low-Income Housing in a Hot and Humid Climate

The Florida Solar Energy Center (FSEC) is metering energy use in two Habitat for Humanity developments. The objective is to understand how energy is used in low income housing and how it can be effectively reduced. The ten "control homes" come from a conventional housing project built by in 1993 Habitat for Humanity in Homestead, Florida. Another ten "experimental homes" have been recruited from the 190 home Jordan Commons development in the same vicinity. These houses, which are soon to be metered, are designed to be energy efficient with high SEER air conditioners, reflective roofing, solar water heaters and energy efficient lighting and appliances.' The instrumentation was installed in the control homes in July of 1994 with a year of 15-minute data now collected on all sites. Data are obtained on seven electrical end-uses (air conditioning, heating, hot water, dryer, range, refrigerator, washer/freezer) as well as total. Weather conditions are also monitored as well as interior comfort conditions (temperature and humidity) and hot water consumption and window ventilation status. The field data allow unique insight into how energy is used in low income housing in a hot and humid climate

Spatial eigensolution analysis of discontinuous Galerkin schemes with practical insights for under-resolved computations and implicit LES

The study focusses on the dispersion and diffusion characteristics of discontinuous spectral element methods - specifically discontinuous Galerkin (DG) - via the spatial eigensolution analysis framework built around a one-dimensional linear problem, namely the linear advection equation. Dispersion and diffusion characteristics are of critical importance when dealing with under-resolved computations, as they affect both the numerical stability of the simulation and the solution accuracy. The spatial eigensolution analysis carried out in this paper complements previous analyses based on the temporal approach, which are more commonly found in the literature. While the latter assumes periodic boundary conditions, the spatial approach assumes inflow/outflow type boundary conditions and is therefore better suited for the investigation of open flows typical of aerodynamic problems, including transitional and fully turbulent flows and aeroacoustics. The influence of spurious/reflected eigenmodes is assessed with regard to the presence of upwind dissipation, naturally present in DG methods. This provides insights into the accuracy and robustness of these schemes for under-resolved computations, including under-resolved direct numerical simulation (uDNS) and implicit large-eddy simulation (iLES). The results estimated from the spatial eigensolution analysis are verified using the one-dimensional linear advection equation and successively by performing two-dimensional compressible Euler simulations that mimic (spatially developing) grid turbulence

Time-Lapse Acoustic Imaging of Mesoscale and Fine-Scale Variability within the Faroe-Shetland Channel

We describe and analyze the results of a three‐dimensional seismic (i.e. acoustic) reflection survey from the Faroe‐Shetland Channel that is calibrated with near‐coincident hydrographic and satellite observations. 54 vertical seismic transects were acquired over a period of 25 days. On each transect, a 250‐‐400 m band of reflections is observed within the water column. Hydrographic measurements demonstrate that this reflective band is caused by temperature variations within the pycnocline that separates warm, near‐surface waters of Atlantic origin from cold, deep waters which flow southward from the Nordic Seas. Tilting of reflective surfaces records geostrophic shear between these near‐surface and deep waters. Measurements of temporal changes of pycnoclinic depth and of reflection tilt are used to infer the existence of an anticyclonic vortex that advects northeastward. Comparison with satellite measurements of sea‐surface temperature and height suggests that this vortex is caused by meandering of the Continental Slope Current. A model of a Gaussian vortex is used to match seismic and satellite observations. This putative vortex has a core radius of 20—30 km and a maximum azimuthal velocity of 0.3‐‐0.4 m s‐1. It translates at 0.01‐‐0.1 m s‐1. Within the pycnocline, diapycnal diffusivity, K , is estimaed by analyzing the turbulent spectral subrange of tracked reflections. K varies between 10‐5.7 and 10‐5.0 m 2 s‐1 in a pattern that is broadly consistent with translation of the vortex. Our integrated study demonstrates the ability of time‐lapse seismic reflection surveying to dynamically resolve the effects that mesoscale activity has upon deep thermohaline structure on scales from meters to hundreds of kilometers.Natural Environment Research Council (NERC) Engineering and Physical Science Research Council 794 Program Grant EP/K034529/

Influence of Attic Radiant Barrier Systems on Air Conditioning Demand in an Utility Pilot Project

A utility monitoring project has evaluated radiant barrier systems (RBS) as a new potential demand site management (DSM) program. The study examined how the retrofit of attic radiant barriers can be expected to alter utility residential space conditioning loads. An RBS consists of a layer of aluminum foil fastened to roof decking or roof trusses to block radiant heat transfer between the hot roof surface and the attic below. The radiant barrier can significantly lower summer heat transfer to the attic insulation and to the cooling duct system. Both of these mechanisms have strong potential impacts on cooling energy use as illustrated in Figures 1 and 2. The pilot project involved installation of RBS in nine homes that had been extensively monitored over the preceding year. The houses varied in conditioned floor area from 939 to 2,440 square feet; attic insulation varied from R-9 to R-30. The homes had shingle roofs with varying degrees of attic ventilation. The radiant barriers were installed during the summer of 2000. Data analysis on the pre and post cooling and heating consumption was used to determine impacts on energy use and peak demand for the utility. The average cooling energy savings from the RBS retrofit was 3.6 kWh/day, or about 9%. The average reduction in summer afternoon peak demand was 420 watts (or about 16%)

FLASTAR: Measured Savings of a Comprehensive Energy Retrofit in a Florida Elementary School

This paper describes the final results for the pilot demonstration of the Florida Public Building Loan Concept. This loan program was intended to provide low cost funds to eligible public entities for upgrade of building energy systems. The site was an elementary school in Central Florida which served as the pilot project to demonstrate energy savings in public buildings similar to that achieved by the Texas LOANSTAR program (Verdict et.al., 1990). Termed FLASTAR (Florida Alliance for Saving Taxes and Resources), the study entailed the comprehensive metering of a test site to demonstrate energy savings potential. Over twenty channels of weather and submetered energy data have been collected since April 12.1995. Annual billed energy consumption for the 41.000 square foot facility was approximately 775,000 kWh (60 kBtu/ft^2) or $55,200 in the base year (1994). During the summer of 1995, replacement of aging chillers resulted in 30energy use. The second retrofit was occupancy sensor controls for classroom and office lighting which were installed in December 1995. However, post retrofit data showed that metered lighting energy use actually increased after the occupancy sensors were installed. Our data, and that of other projects. suggests that the occupancy sensor retrofit may have increased lighting on-times. Previously school personnel practiced responsible manual switching. but then came to depend on automatic control after the retrofit. The final project retrofit saw an energy management system (EMS) added in the summer of 1996. The system provided direct digital control @DC) of the school chiller, air handlers and packaged direct expansion (DX) roof-top cooling systems. The EMS equipment reduced chiller energy use by a further 16by 30The project retrofits were found to reduce overall school energy use by approximately 15120.000 kWh per year. The annual energy savings totaled$4,600 at current energy prices, although the retrofits did not significantly impact facility peak load