An efficient optimum interpolation scheme for objective analysis over Indian region |
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Authors: | S K Sinha S G Narkhedkar S Rajamani |
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Institution: | (1) Indian Institute of Tropical Meteorology, Pashan Road, 411008 Pune, India |
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Abstract: | In the optimum interpolation scheme, the weights for the observations are computed by solving a set of linear equations for
every grid point. As the number of observations increases particularly over data-rich regions, the matrix dimension increases
and the computer time required to solve these equations to determine weights increases considerably. In order to reduce the
computer time for computing the weights, Tanguay and Robert suggested schemes in which the gaussian function representing
the autocorrelation function has been approximated by a second-order and also by a fourth-order Taylor series expansion. This
resulted in the solution of matrices of order 4 or 9 respectively to obtain weighting functions irrespective of the number
of observations used in the analysis. In the present study, the analyses of mean sea level pressure and geopotential height
at 700 mbar level have been carried out for five days using the above two schemes and the regular OI scheme. The analyses
are found to be similar in all the three cases suggesting that a lot of computer time could be saved without sacrificing the
analysis accuracy by using the modified scheme in which the second-order approximation is utilized. |
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Keywords: | Efficient optimum interpolation weighting function autocorrelation function structure function objective analysis |
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