Unsatisfying forecast of a Mediterranean cyclone: a verification study employing state-of-the-art techniques

International audienceOn 16?17 November 2000, a relatively intense precipitation event on the north-western Italy was heavily underestimated, mainly due to shifting error, by three operational 10-km limited area models (LAMs) which differ about basic equations, domain size, and parameterisation schemes. The scope of the work is to investigate possible common error-sources independent from the single model, in particular the effect of initialisation. Thus, the complex evolution over the western Mediterranean Sea of the cyclone responsible for the event was investigated. Several objective and subjective verification techniques have been employed to check one of the LAMs' forecast against the available observations (precipitation from rain gauge and retrieved from ground-based radar, and satellite-retrieved atmospheric humidity patterns). Despite a clear statement is not achieved, results indicate that high sensitivity to the initial conditions, and the inadequacy of the observational network on the southern Mediterranean area, can play a major role in producing the forecast shifting error on the target area

Verification of precipitation forecasts from two limited-area models over Italy and comparison with ECMWF forecasts using a resampling technique

This paper presents the first systematic limited area model (LAM) precipitation verification work over Italy. A resampling technique was used to provide skill score results along with confidence intervals. Two years of data were used, starting in October 2000. Two operational LAMs have been considered, the Limited Area Model Bologna (LAMBO) operating at the Agenzia Regionale Prevenzione e Ambiente- Servizio Meteorologico Regionale (ARPA-SMR) of the Emilia–Romagna region, and the QUADRICS Bologna Limited Area Model (QBOLAM) running at the Agenzia per la Protezione dell’Ambiente e per i Servizi Tecnici (APAT). A 24-h forecast skill score comparison was first performed on the native 0.1° high-resolution grids, using a Barnes scheme to produce the observed 24-h accumulated rainfall analysis. Two nonparametric skill scores were used: the equitable threat score (ETS) and the Hanssen and Kuipers score (HK). Frequency biases (BIA) were also calculated. LAM forecasts were also remapped on a lowerresolution grid (0.5°), using a nearest-neighbor average method; this remapping allowed for comparison with ECMWF model forecasts, and for LAM intercomparisons at lower resolution, with the advantage of reducing the skill score sensitivity to small displacements errors. LAM skill scores depend on the resolution of the verification grid, with an increase when they are verified on a lower-resolution grid. The selected LAMs have a higher BIA compared to ECMWF, showing a tendency to overforecast precipitation, especially along mountain ranges, possibly due to undesired effects from the large-scale and/or convective precipitation parameterizations. Lower ECMWF BIA accounts for skill score differences. LAMBO precipitation forecasts during winter (adjusted for BIA differences) have less misses than ECMWF over the islands of Sardinia and Sicily. Higher-resolution orography definitely adds value to LAM forecasts

A multiscale approach for precipitation verification applied to the FORALPS case studies

International audienceMultiscale methods, such as the power spectrum, are suitable diagnostic tools for studying the second order statistics of a gridded field. For instance, in the case of Numerical Weather Prediction models, a drop in the power spectrum for a given scale indicates the inability of the model to reproduce the variance of the phenomenon below the correspondent spatial scale. Hence, these statistics provide an insight into the real resolution of a gridded field and must be accurately known for interpolation and downscaling purposes. In this work, belonging to the EU INTERREG IIIB Alpine Space FORALPS project, the power spectra of the precipitation fields for two intense rain events, which occurred over the north-eastern alpine region, have been studied in detail. A drop in the power spectrum at the shortest scales (about 30 km) has been found, as well as a strong matching between the precipitation spectrum and the spectrum of the orography. Furthermore, it has also been shown how the spectra help understand the behavior of the skill scores traditionally used in Quantitative Precipitation Forecast verification, as these are sensitive to the amount of small scale detail present in the fields

Verification of Precipitation Forecasts from Two Limited-Area Models over Italy and Comparison with ECMWF Forecasts Using a Resampling Technique

Abstract This paper presents the first systematic limited area model (LAM) precipitation verification work over Italy. A resampling technique was used to provide skill score results along with confidence intervals. Two years of data were used, starting in October 2000. Two operational LAMs have been considered, the Limited Area Model Bologna (LAMBO) operating at the Agenzia Regionale Prevenzione e Ambiente-Servizio Meteorologico Regionale (ARPA-SMR) of the Emilia–Romagna region, and the QUADRICS Bologna Limited Area Model (QBOLAM) running at the Agenzia per la Protezione dell'Ambiente e per i Servizi Tecnici (APAT). A 24-h forecast skill score comparison was first performed on the native 0.1° high-resolution grids, using a Barnes scheme to produce the observed 24-h accumulated rainfall analysis. Two nonparametric skill scores were used: the equitable threat score (ETS) and the Hanssen and Kuipers score (HK). Frequency biases (BIA) were also calculated. LAM forecasts were also remapped on a lower-resolution grid (0.5°), using a nearest-neighbor average method; this remapping allowed for comparison with ECMWF model forecasts, and for LAM intercomparisons at lower resolution, with the advantage of reducing the skill score sensitivity to small displacements errors. LAM skill scores depend on the resolution of the verification grid, with an increase when they are verified on a lower-resolution grid. The selected LAMs have a higher BIA compared to ECMWF, showing a tendency to overforecast precipitation, especially along mountain ranges, possibly due to undesired effects from the large-scale and/or convective precipitation parameterizations. Lower ECMWF BIA accounts for skill score differences. LAMBO precipitation forecasts during winter (adjusted for BIA differences) have less misses than ECMWF over the islands of Sardinia and Sicily. Higher-resolution orography definitely adds value to LAM forecasts

Cryogenic and room temperature strength of sapphire jointed by hydroxide-catalysis bonding

Hydroxide-catalysis bonding is a precision technique used for jointing components in opto-mechanical systems and has been implemented in the construction of quasi-monolithic silica suspensions in gravitational wave detectors. Future detectors are likely to operate at cryogenic temperatures which will lead to a change in test mass and suspension material. One candidate material is mono-crystalline sapphire. Here results are presented showing the influence of various bonding solutions on the strength of the hydroxide-catalysis bonds formed between sapphire samples, measured both at room temperature and at 77 K, and it is demonstrated that sodium silicate solution is the most promising in terms of strength, producing bonds with a mean strength of 63 MPa. In addition the results show that the strengths of bonds were undiminished when tested at cryogenic temperatures

Calibration of the LIGO displacement actuators via laser frequency modulation

We present a frequency modulation technique for calibration of the displacement actuators of the LIGO 4-km-long interferometric gravitational-wave detectors. With the interferometer locked in a single-arm configuration, we modulate the frequency of the laser light, creating an effective length variation that we calibrate by measuring the amplitude of the frequency modulation. By simultaneously driving the voice coil actuators that control the length of the arm cavity, we calibrate the voice coil actuation coefficient with an estimated 1-sigma uncertainty of less than one percent. This technique enables a force-free, single-step actuator calibration using a displacement fiducial that is fundamentally different from those employed in other calibration methods.Comment: 10 pages, 5 figures, submitted to Classical and Quantum Gravit

Three models intercomparison for Quantitative Precipitation Forecast over Calabria

In the framework of the National Project “Sviluppo di distretti industriali per le Osservazioni della Terra” (Development of Industrial Districts for Earth Observations)funded by MIUR (Ministero dell’Universit`a e della Ricerca Scientifica —Italian Ministry of the University and Scientific Research)t wo operational mesoscale models were set-up for Calabria, the southernmost tip of the Italian peninsula. Models are RAMS (Regional Atmospheric Modeling System)and MM5 (Mesoscale Modeling 5)that are run every day at Crati scrl to produce weather forecast over Calabria (http://www.crati.it). This paper reports model intercomparison for Quantitative Precipitation Forecast evaluated for a 20 month period from 1th October 2000 to 31th May 2002. In addition to RAMS and MM5 outputs, QBOLAM rainfall fields are available for the period selected and included in the comparison. This model runs operationally at “Agenzia per la Protezione dell’Ambiente e per i Servizi Tecnici”. Forecasts are verified comparing models outputs with raingauge data recorded by the regional meteorological network, which has 75 raingauges. Large-scale forcing is the same for all models considered and differences are due to physical/numerical parameterizations and horizontal resolutions. QPFs show differences between models. Largest differences are for BIA compared to the other considered scores. Performances decrease with increasing forecast time for RAMS and MM5, whilst QBOLAM scores better for second day forecast

Search for Gravitational Waves from Compact Binary Coalescence In LIGO and Virgo Data from S5 and VSR1

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo detectors. Five months of data were collected during the concurrent S5 (LIGO) and VSR1 (Virgo) science runs. The search focused on signals from binary mergers with a total mass between 2 and 35 M. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for nonspinning binary neutron stars, black hole-neutron star systems, and binary black holes to be 8.7×10−3 yr−1L−1 10 , 2.2×10−3 yr−1L−1 10 , and 4.4×10−4 yr−1L−1 10 respectively, where L10 is 1010 times the blue solar luminosity. These upper limits are compared with astrophysical expectations

Feasibility of measuring the Shapiro time delay over meter-scale distances

The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to construct, present an example design, and calculate the signal that would be detectable by Advanced LIGO. This offers the first opportunity to measure space-time curvature effects on a laboratory distance scale.Comment: 13 pages, 6 figures; v3 has updated instrumental noise curves plus a few text edits; resubmitted to Classical and Quantum Gravit

Gravitational Waves from Known Pulsars: Results from the Initial Detector Era

We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper