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A K SRIVASTAVA SOMENATH DUTTA S R KSHIRSAGAR KAVITA SRIVASTAVA 《Journal of Earth System Science》2014,123(3):445-456
In the paper, influence of extratropical circulation features on Indian Summer Monsoon Rainfall (ISMR) is examined. Energetics of extratropics, north of Indian subcontinent for deficient and non-deficient ISMR years, during two periods 1951–1978 and 1979–2005, are calculated and critically analyzed. It is observed that for the period 1951–1978, only two out of the 10 energetics parameters, viz., the zonal available potential energy (high) and conversion of zonal kinetic energy to eddy kinetic energy (low) differed significantly in JJA months of the deficient years from that of the non-deficient years. However, during the 1979–2005 period, as many as six out of the 10 energetics parameters, viz., eddy available potential energy, zonal available potential energy, eddy kinetic energy, generation of zonal available potential energy, conversion of zonal available potential energy to zonal kinetic energy and conversion of zonal kinetic energy to eddy kinetic energy differed significantly in JJA months of the deficient years from that of the non-deficient years. These results confirm growing influence of the transient stationary waves in deficient years after the climate shift year, 1979. Analysis of energetics parameters of the pre-monsoon season of the two periods also reveals similar results. This suggests that forcings apparently responsible for energetics in JJA months of the deficient years of the later period were present even before the advent of Indian summer monsoon season. 相似文献
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An analysis system experiment was conducted for the month of June 2008 with Gridpoint Statistical Interpolation (GSI) analysis
scheme using NCMRWF’s (National Centre for Medium Range Weather Forecasting) T254L64 model. Global analyses were carried out
for all days of the month and respective forecast runs are made up to 120-hr. These analyses and forecasts are inter-compared
with the operational T254L64 model outputs which uses Spectral Statistical Interpolation (SSI) analysis scheme. The prime
objective of this study is to assess the impact of GSI analysis scheme with special emphasis on Indian summer monsoon as compared
to SSI. 相似文献
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The satellite-derived wind from cloud and moisture features of geostationary satellites is an important data source for numerical weather prediction(NWP) models. These datasets and global positioning system radio occultation(GPSRO)satellite radiances are assimilated in the four-dimensional variational atmospheric data assimilation system of the UKMO Unified Model in India. This study focuses on the importance of these data in the NWP system and their impact on short-term24-h forecasts. The quality of the wind observations is compared to the short-range forecast from the model background. The observation increments(observation minus background) are computed as the satellite-derived wind minus the model forecast with a 6-h lead time. The results show the model background has a large easterly wind component compared to satellite observations. The importance of each observation in the analysis is studied using an adjoint-based forecast sensitivity to observation method. The results show that at least around 50% of all types of satellite observations are beneficial. In terms of individual contribution, METEOSAT-7 shows a higher percentage of impact(nearly 50%), as compared to GEOS, MTSAT-2and METEOSAT-10, all of which have a less than 25% impact. In addition, the impact of GPSRO, infrared atmospheric sounding interferometer(IASI) and atmospheric infrared sounder(AIRS) data is calculated. The GPSRO observations have beneficial impacts up to 50 km. Over the Southern Hemisphere, the high spectral radiances from IASI and AIRS show a greater impact than over the Northern Hemisphere. The results in this study can be used for further improvements in the use of new and existing satellite observations. 相似文献
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Characterizing spatial and seasonal variability of carbon dioxide and water vapour fluxes above a tropical mixed mangrove forest canopy, India 总被引：1，自引：0，他引：1
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V S PRASAD SAJI MOHANDAS SURYA KANTI DUTTA M DAS GUPTA G R IYENGAR E N RAJAGOPAL SWATI BASU 《Journal of Earth System Science》2014,123(2):247-258
Medium range weather forecasts are being generated in real time using Global Data Assimilation Forecasting System (GDAFS) at NCMRWF since 1994. The system has been continuously upgraded in terms of data usage, assimilation and forecasting system. Recently this system was upgraded to a horizontal resolution of T574 (about 22 km) with 64 levels in vertical. The assimilation scheme of this upgraded system is based on the latest Grid Statistical Interpolation (GSI) scheme and it has the provision to use most of available meteorological and oceanographic satellite datasets besides conventional meteorological observations. The new system has an improved procedure for relocating tropical cyclone to its observed position with the correct intensity. All these modifications have resulted in improvement of skill of medium range forecasts by about 1 day. 相似文献