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Longitude Grid (longitude + grid)

Distribution by Scientific Domains
Earth and Environmental Science66%

Selected Abstracts

Simple statistical structure in time series for daily air flow characteristics

ENVIRONMETRICS, Issue 1 2008
Piia Post
Abstract The structure function is used for quantifying of non-stationarity in time series for certain daily air flow characteristics (DAFC). The National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis 30 year (1968,97) dataset given over 5°,×,10° latitude longitude grid is used to calculate the DAFC series for the Baltic Sea region. The quantification on the basis of the Hurst exponent H enables us to discriminate between the strong synoptic scale non-stationarity and a mild large-scale one. Presented examples show that the change of H is accompanied by a change of the distribution for the series' increments. Long-range increments for various DAFC appear to be approximately normally distributed with approximately constant variance independent of the increment length over a remarkably wide range. The property might be useful in describing a long-range variability of the air flow characteristics. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Projecting future N2O emissions from agricultural soils in Belgium

GLOBAL CHANGE BIOLOGY, Issue 1 2007
CAROLINE ROELANDT
Abstract This study analyses the spatial and temporal variability of N2O emissions from the agricultural soils of Belgium. Annual N2O emission rates are estimated with two statistical models, MCROPS and MGRASS, which take account of the impact of changes in land use, climate, and nitrogen-fertilization rate. The models are used to simulate the temporal trend of N2O emissions between 1990 and 2050 for a 10, latitude and longitude grid. The results are also aggregated to the regional and national scale to facilitate comparison with other studies and national inventories. Changes in climate and land use are derived from the quantitative scenarios developed by the ATEAM project based on the Intergovernmental Panel on Climate Change-Special Report on Emissions Scenarios (IPCC-SRES) storylines. The average N2O flux for Belgium was estimated to be 8.6 × 106 kg N2O-N yr,1 (STD = 2.1 × 106 kg N2O-N yr,1) for the period 1990,2000. Fluxes estimated for a single year (1996) give a reasonable agreement with published results at the national and regional scales for the same year. The scenario-based simulations of future N2O emissions show the strong influence of land-use change. The scenarios A1FI, B1 and B2 produce similar results between 2001 and 2050 with a national emission rate in 2050 of 11.9 × 106 kg N2O-N yr,1. The A2 scenario, however, is very sensitive to the reduction in agricultural land areas (,14% compared with the 1990 baseline), which results in a reduced emission rate in 2050 of 8.3 × 106 kg N2O-N yr,1. Neither the climatic change scenarios nor the reduction in nitrogen fertilization rate could explain these results leading to the conclusion that N2O emissions from Belgian agricultural soils will be more markedly affected by changes in agricultural land areas. [source]

Cubic-spline interpolation on a non-uniform latitude,longitude grid: achieving cross- and circum-polar continuity

ATMOSPHERIC SCIENCE LETTERS, Issue 3 2010
Markus Gross
Abstract Although it is straightforward to construct cubic splines in Cartesian geometry, this is not so for latitude-longitude grids over the sphere, because of the polar singularity. Previous work has either introduced ad hoc approximations over the polar caps, to the detriment of both continuity and accuracy, or has been restricted to interpolation of fields defined on uniform grids, with an even number of meridians, and with known polar values. These limitations are addressed herein by reformulating the construction of bicubic splines as the minimisation of an appropriate integral subject to certain constraints. © Crown Copyright 2010. Reproduced with the permission of HMSO. Published by John Wiley & Sons, Ltd. [source]

Fibonacci grids: A novel approach to global modelling

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 619 2006
Richard Swinbank
Abstract Recent years have seen a resurgence of interest in a variety of non-standard computational grids for global numerical prediction. The motivation has been to reduce problems associated with the converging meridians and the polar singularities of conventional regular latitude,longitude grids. A further impetus has come from the adoption of massively parallel computers, for which it is necessary to distribute work equitably across the processors; this is more practicable for some non-standard grids. Desirable attributes of a grid for high-order spatial finite differencing are: (i) geometrical regularity; (ii) a homogeneous and approximately isotropic spatial resolution; (iii) a low proportion of the grid points where the numerical procedures require special customization (such as near coordinate singularities or grid edges); (iv) ease of parallelization. One family of grid arrangements which, to our knowledge, has never before been applied to numerical weather prediction, but which appears to offer several technical advantages, are what we shall refer to as ,Fibonacci grids'. These grids possess virtually uniform and isotropic resolution, with an equal area for each grid point. There are only two compact singular regions on a sphere that require customized numerics. We demonstrate the practicality of this type of grid in shallow-water simulations, and discuss the prospects for efficiently using these frameworks in three-dimensional weather prediction or climate models. © Crown copyright, 2006. Royal Meteorological Society [source]

Conservative constraint for a quasi-uniform overset grid on the sphere

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 616 2006
Xindong Peng
Abstract A conservative constraint is presented for a new quasi-uniform overset (Yin-Yang) grid on the sphere. The Yin-Yang grid is a newly developed grid system in spherical geometry created by matching two notched latitude,longitude grids which are normal to each other. Global and local conservation is achieved with an interpolation algorithm that exactly guarantees that the fluxes on boundaries of the two grid components are identical. Several numerical experiments are shown to confirm the conservation in passive transport situations and shallow-water dynamical equations. Copyright © 2006 Royal Meteorological Society. [source]

Development of a high resolution daily gridded temperature data set (1969,2005) for the Indian region

ATMOSPHERIC SCIENCE LETTERS, Issue 4 2009
A. K. Srivastava
Abstract A high resolution daily gridded temperature data set for the Indian region was developed using temperature data of 395 quality controlled stations for the period 1969,2005. A modified version of the Shepard's angular distance weighting algorithm was used for interpolating the station temperature data into 1° latitude × 1° longitude grids. Using the cross validation, errors were estimated and found less than 0.5 °C. The data set was also compared with another high resolution data set and found comparable. Mean frequency of cold and heat waves, temperature anomalies associated with the monsoon breaks have been presented. Copyright © 2009 Royal Meteorological Society [source]