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Wind Observations (wind + observation)

Distribution by Scientific Domains
Earth and Environmental Science66%

Selected Abstracts

Modeling and predicting complex space,time structures and patterns of coastal wind fields

ENVIRONMETRICS, Issue 5 2005
Montserrat Fuentes
Abstract A statistical technique is developed for wind field mapping that can be used to improve either the assimilation of surface wind observations into a model initial field or the accuracy of post-processing algorithms run on meteorological model output. The observed wind field at any particular location is treated as a function of the true (but unknown) wind and measurement error. The wind field from numerical weather prediction models is treated as a function of a linear and multiplicative bias and a term which represents random deviations with respect to the true wind process. A Bayesian approach is taken to provide information about the true underlying wind field, which is modeled as a stochastic process with a non-stationary and non-separable covariance. The method is applied to forecast wind fields from a widely used mesoscale numerical weather prediction (NWP) model (MM5). The statistical model tests are carried out for the wind speed over the Chesapeake Bay and the surrounding region for 21 July 2002. Coastal wind observations that have not been used in the MM5 initial conditions or forecasts are used in conjunction with the MM5 forecast wind field (valid at the same time that the observations were available) in a post-processing technique that combined these two sources of information to predict the true wind field. Based on the mean square error, this procedure provides a substantial correction to the MM5 wind field forecast over the Chesapeake Bay region. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Trends in storminess over the Netherlands, 1962,2002

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2005
A. Smits
Abstract Trends in the annual number of independent wind events over the Netherlands are studied for the period 1962,2002. The events are selected out of 13 hourly 10 m wind speed records that are part of a high quality dataset of near-surface wind observations at Dutch meteorological stations. Comparisons are made with trends in independent wind events selected from geostrophic wind speed records and reanalysis data. The results for moderate wind events (that occur on average 10 times per year) and strong wind events (that occur on average twice a year) indicate a decrease in storminess over the Netherlands between 5 and 10%/decade. This result is inconsistent with National Centers for Environmental Prediction,National Center for Atmospheric Research or European Centre for Medium-Range Weather Forecasts reanalysis data, which suggest increased storminess during the same 41 year period. Possible explanations are given for the discrepancy between the trends in storminess based on station data and the trends in storminess based on reanalysis data. Evaluation of trends in geostrophic wind, both from station data and reanalysis data, and evaluation of trends in vector-averaged (upscaled) 10 m wind over the Netherlands point towards inhomogeneities in the reanalysis data as the main cause of the discrepancy. We conclude that it is likely that the decrease in storminess observed in Dutch station records of near-surface wind in the past four decades is closer to reality than the increase suggested by the reanalysis data. Copyright © 2005 Royal Meteorological Society. [source]

Non-linear damping of slab modes and cosmic ray transport

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008
A. Shalchi
ABSTRACT By applying recent results for the slab correlation time-scale on to cosmic ray scattering theory, we compute cosmic ray parallel mean free paths within the quasi-linear limit. By employing these results on to charged particle transport in the Solar system, we demonstrate that much larger parallel mean free paths can be obtained in comparison to previous results. A comparison with solar wind observations is also presented to show that the new theoretical results are much closer to the observations than the previous results. [source]

Construction and application of covariance functions with variable length-fields

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 619 2006
Gregory Gaspari
Abstract This article focuses on construction, directly in physical space, of three-dimensional covariance functions parametrized by a length-field, and on an application of these functions to improve the representation of the Quasi-Biennial Oscillation (QBO) in the Goddard Earth Observing System, Version 4 (GEOS-4) data assimilation system. The covariance functions are obtained by fusing collections of auto-covariance functions having different constant length-scales with their associated cross-covariance functions. This construction yields covariance functions with length-scales that can vary arbitrarily over any finite partition of the spatial domain. A simple, and also motivating application of these functions is to the case where the length-scale varies in the vertical direction only. The class of covariance functions with variable length-fields constructed in this article will be called multi-level to associate them with this application. The multi-level covariance functions extend well-known single-level covariance functions depending only on a constant length-scale. Generalizations of the familiar first-and third-order autoregressive covariances in three dimensions are given, providing multi-level covariances with zero and four continuous derivatives at zero separation, respectively. Multi-level piecewise rational covariances with two continuous derivatives at zero separation are also provided. Multi-level power-law covariances are constructed with continuous derivatives of all orders. Additional multi-level covariance functions are constructed using the Schur product of single- and multi-level covariance functions. A multi-variate, multi-level power-law covariance with a large troposphere-to-stratosphere length-field gradient is employed to reproduce the QBO from sparse radiosonde wind observations in the tropical lower stratosphere. This covariance model is described along with details of the assimilation experiments. The new covariance model is shown to represent the vertical wind shear associated with the QBO much more effectively than the multi-variate, multi-level covariance model in the baseline GEOS-4 system. Copyright © 2006 Royal Meteorological Society [source]

Short-range urban dispersion experiments using fixed and moving sources

ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
D. E. Shallcross
Abstract Four perfluorocarbon tracer dispersion experiments were carried out in central London, United Kingdom in 2004. These experiments were supplementary to the dispersion of air pollution and penetration into the local environment (DAPPLE) campaign and consisted of ground level releases, roof level releases and mobile releases; the latter are believed to be the first such experiments to be undertaken. A detailed description of the experiments including release, sampling, analysis and wind observations is given. The characteristics of dispersion from the fixed and mobile sources are discussed and contrasted, in particular, the decay in concentration levels away from the source location and the additional variability that results from the non-uniformity of vehicle speed. Copyright © 2009 Royal Meteorological Society [source]

Comparison of four non-hydrostatic models for flow over the Isle of Arran

ATMOSPHERIC SCIENCE LETTERS, Issue 3 2005
Juma Al-Maskari
Abstract Four non-hydrostatic atmospheric models were compared for a case study of southerly airflow over the Isle of Arran in Scotland. The model results are contrasted with each other and aircraft wind observations. All resolve qualitatively similar the background gravity wave flow, despite different formulations. Copyright © 2005 Royal Meteorological Society [source]