5.  Vujnović, V. and I. Lisac: De Aurora Boreali (1737) - Contemporary insight to the young Bošković's treatise.

An analysis of Bošković's early paper concerned with the polar light (aurora borealis) gives an insight into the validity of the mathematical method which the young Bošković applied to significant geophysical phenomena in order to comprehend their nature. Based on the given data, we have examined numerical results about the height of atmosphere and the heights of the auroras which were observed over Europe in 1726 and in 1737. In his text there is not a single mathematical formula. Following his instructions we have derived a formula which may be used to determine the distance of an aurora by observing it from one station. For the assumed aurora model, his method is applicable. We find that described ideas on the physical cause of aurora, conceived in a fluid coming from the sun, have elements of modern knowledge.

Keywords: Ruđer Bošković, aurora borealis, atmosphere dimensions and density

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6.  Chun, O. W. and J. S. Mandeep: Empirical methods for converting rainfall rate distribution from several higher integration times into a 1-minute integration time in Malaysia.

The rapid development of the radio communications system, especially in developed countries, has drawn the attention of telecommunication systems engineers to explore the frequency band above the Ku-band. Because radio communication systems operating in the frequency band above the Ku-band (10 GHz) suffer from rain attenuation during rainy conditions, prediction of rain attenuation using a 1-min rainfall rate distribution is indeed vital. However, a 1-min rainfall rate distribution is not widely available compared to rainfall rate distributions with longer integration times. Therefore, a suitable conversion method is required to predict 1-min rainfall rate distributions of distinct integration times. This paper presents several conversion methods such as Segal, Burgueno et al., Chebil and Rahman, Joo et al., EXCELL RSC and LG. The Segal method provides an overall Root Mean Square (RMS) error below 5% at different integration times and is suitable to be used in Malaysia.

Keywords: integration time, rainfall rate distribution, conversion method, conversion coefficient, microwave

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7.  Shrivastava, G., S. Karmakar, M. Kumar Kowar and P. Guhathakurta: BPN model for long-range forecast of monsoon rainfall over a very small geographical region and its verification for 2012.

New operational long range forecasting model of India Meteorological Department (IMD) is statistical in nature, which has many inherent limitations. The correlation between monsoon rainfall and its predictors can never be perfect. They may suffer epochal changes and there may be a cross correlations among predictors. It is almost impossible to identify appropriate predictors of monsoon rainfall over a smaller region like district or division as well. Thus, attempts to forecast monsoon rainfall over a small geographical region like district through this current IMD's operational model become inaccurate. It is found that Back Propagation Neural Network (BPN) is skilled enough to identify the internal dynamics of chaotic data time series and sufficiently suitable to predict future value by past recorded data time series. Thus a BPN model in deterministic forecast has been developed for a long range forecast (LRF) of monsoon rainfall over smaller Indian geographical region. Our study area, Ambikapur is located at 23° 07' 23" N, 83° 11' 39" E, an average elevation of 623 meters (i.e., 2078 feet) and Total Geographical Area (TGA) is 15 733 km2. Performance of the model during the development period (1951-2007) has been found excellent. The performance during the testing period (2008-2011) has also been found good except for the years of 2009 and 2010. The model has also been verified independently and operated for the year 2012. The deviation between actual and predicted monsoon rainfall in Long Period Average (% of LPA) for this year is found 2.7% only. These facts exhibit the efficacy of the proposed model.

Keywords: meteorology, long-range forecast, monsoon rainfall, neural network, back-propagation, deterministic

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8.  Durai, V. R. and R. Bhardwaj: Improving precipitation forecasts skill over India using a multi-model ensemble technique.

In this paper a Multi-Model Ensemble (MME) technique is experimented for improving day to day rainfall forecast over India in short to medium range time scale during summer monsoon of 2010. Four operational global Numerical Weather Prediction (NWP) models namely, ECMWF, JMA, NCEP GFS and UKMO available on real time basis at India Meteorological Department (IMD), New Delhi are used simultaneously with appropriate weights to obtain the MME Technique. In this technique, weights for each NWP model at each grid point is assigned on the basis of the correlation coefficient (CC) between model forecasts and observed daily rainfall time series of south west monsoon (JJAS) season. Apart from MME, a simple ensemble mean (ENSM) forecast are also generated and experimented. The rainfall prediction skill of the weighted MME is examined against ENSM and member models. The inter-comparison reveals that the weighted MME is able to provide more accurate forecast of rainfall over Indian monsoon region by taking the strength of each constituent member model. It has been further found that the rainfall prediction skill of MME is higher as compared to ENSM and member models in the short range time scale. The rainfall prediction skill of weighted MME technique improved significantly over India.

Keywords: numerical weather prediction, multimodel ensemble (MME) forecasting, rainfall prediction skill, global model

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9.  Narayan J. P. and V. Kumar: A fourth-order accurate finite-difference program for the simulation of SH-wave propagation in heterogeneous viscoelastic medium.

This article presents a staggered grid time-domain finite-difference (FD) program for the simulation of SH-wave propagation in a viscoelastic heterogeneous medium. The incorporation of realistic damping in FD program is based on a rheological model widely known as generalized Maxwell body (GMB-EK). The accuracy of implementation of realistic damping is validated by comparing the numerically computed frequency dependent quality factors and phase velocity with the same computed using GMB-EK rheological model and the Futterman's relationship. The accuracy was also validated by comparing the numerically computed soil amplification at resonance frequency for different damping with the analytical solutions. The stability and grid dispersion are also studied in details.

Keywords: viscoelastic SH-wave equations, finite difference program, fourth order spatial accuracy, VGR-stress imaging technique, and stability and grid dispersion

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10.  Book J. W., H. Perkins and M. Wimbush: Correction to "North Adriatic tides: observations, variational data assimilation modeling, and linear tide dynamics".

A precision/round-off error has been discovered in the tidal analysis routines used in the paper "North Adriatic tides: observations, variational data assimilation modeling, and linear tide dynamics" by J. W. Book, H. Perkins, and M. Wimbush (2009, Geofizika, 26, 115-143). Tidal elevation phases for 12 of the 15 stations are, on average, too low by 3.9° for the diurnal constituents and 7.9° for the semidiurnal constituents in Tabs. 4 and 5. These tables have been corrected and are republished here.

The error also had an effect on the input data used for the linear variational data assimilation model, and combined with a nearest neighbor interpolation scheme produced an approximate 15 minute forward shift in time for 6 of the 43 synthesized tidal records. The error produced final model solutions that had tidal elevation phases 3.5° too high for M ₂, 1.6° too high for K₁, and similar matching phase shifts for other semidiurnal and diurnal constituents. The errors in the input data have been corrected, the interpolation scheme has been changed to a piecewise cubic spline method, and the model runs have all been redone.

The new model results suggest a minor change in optimal friction parameter, which in turn alters model Q factors and dissipation. However, the original finding that these values are not well determined by this methodology remains true. Model and observational results originally shown in Figs. 5-7 and Figs. 13-14 have slightly changed and are republished here. The main conclusions from the original work regarding Kelvin waves and TRW dynamics for the North Adriatic basin remain unaltered by these corrections.

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