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  • 1
    Digitale Medien
    Digitale Medien
    Numerical Simulation of the Sensitivity of Summer Monsoon Circulation and Rainfall over India to Land Surface Processes (1998)
    Springer
    Pure and applied geophysics 152 (1998), S. 781-809 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Numerical simulation, summer monsoon, circulation, land surface, parameterization.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The influence of soil moisture and vegetation variation on simulation of monsoon circulation and rainfall is investigated. For this purpose a simple land surface parameterization scheme is incorporated in a three-dimensional regional high resolution nested grid atmospheric model. Based on the land surface parameterization scheme, latent heat and sensible heat fluxes are explicitly estimated over the entire domain of the model. Two sensitivity studies are conducted; one with bare dry soil conditions (no latent heat flux from land surface) and the other with realistic representation of the land surface parameters such as soil moisture, vegetation cover and landuse patterns in the numerical simulation. The sensitivity of main monsoon features such as Somali jet, monsoon trough and tropical easterly jet to land surface processes are discussed.¶Results suggest the necessity of including a detailed land surface parameterization in the realistic short-range weather numerical predictions. An enhanced short-range prediction of hydrological cycle including precipitation was produced by the model, with land surface processes parameterized. This parameterization appears to simulate all the main circulation features associated with the summer monsoon in a realistic manner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050178
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  • 2
    Digitale Medien
    Digitale Medien
    A Study on the Performance of the NCMRWF Analysis and Forecasting System During Asian Summer Monsoon: Thermodynamic Aspects (1999)
    Springer
    Pure and applied geophysics 154 (1999), S. 141-162 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Asian summer monsoon, systematic errors, temperature, moisture, heat budget, moisture budget.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The thermodynamic characteristics of the Asian summer monsoon are examined with a global analysis-forecast system. In this study, we investigated the large-scale balances of heat and moisture by making use of operational analyses as well as forecast fields for June, July and August (JJA), 1994. Apart from elucidating systematic errors in the temperature and moisture fields, the study expounds the influence of these errors on the large-scale budgets of heat and moisture over the monsoon region. The temperature forecasts of the model delineate predominant cooling in the middle and lower tropospheres over the monsoon region. Similarly, the moisture forecasts evince a drying tendency in the lower troposphere. However, certain sectors of moderate moistening exist over the peninsular India and adjoining oceanic sectors of the Arabian Sea and Bay of Bengal.¶The broad features of the large-scale heat and moisture budgets represented by the analysis/forecast fields indicate good agreement with the observed aspects of the summer monsoon circulation. The model forecasts fail to retain the analyzed atmospheric variability in terms of the mean circulation, which is indicated by underestimation of various terms of heat and moisture budgets with an increase in the forecast period. Further, the forecasts depict an anomalous diabatic cooling layer in the lower middle troposphere of the monsoon region which inhibits vertical transfer of heat and moisture from the mixed layer of the atmospheric boundary layer to the middle troposphere. In effect, the monsoon circulation is considerably weakened with an increase in the forecast period. The treatment of shallow convection and the use of interactive clouds in the model can reduce the cooling bias considerably.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050225
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  • 3
    Digitale Medien
    Digitale Medien
    Numerical Investigation of the Somali Jet Interaction with the Western Ghat Mountains (1999)
    Springer
    Pure and applied geophysics 154 (1999), S. 365-396 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Numerical investigation, Somali jet, the Western Ghat.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —Several major features of the interaction of the Somali jet with the Western Ghat Mountains have been observed. These include a pressure ridge, strong vertical motions, and occurrences of highly reflective cloud and heavy rainfall rates along the west coast of India. A triple nested regional weather prediction model has been used to investigate the dynamic interaction between the Somali jet and the Western Ghat Mountains. Two numerical experiments were conducted; one with the topography of western India and the other without. In the experiment without topography, the Western Ghat Mountains were removed from the innermost domain. The results for the innermost domain in the two experiments were analyzed and compared. The results from the simulation with topography captured several of the observed features of the Somali jet interaction with the Western Ghat Mountains. The simulation without topography failed to reveal these features. The results suggest that the blocking effect of the Western Ghats plays an important role in the prediction of the rainfall over the west coast of India.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050234
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  • 4
    Digitale Medien
    Digitale Medien
    Influence of the Planetary Boundary Layer Physics on Medium-range Prediction of Monsoon over India (1999)
    Springer
    Pure and applied geophysics 155 (1999), S. 33-55 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: PBL parameterisation, TKE closure, Indian summer monsoon, monsoon depression, medium-range forecast.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The present study emphasizes the importance of proper representation of boundary layer physics in a general circulation model. The Turbulent Kinetic Energy (TKE) closure scheme incorpo rates important processes of the Planetary Boundary Layer (PBL) compared to a simplistic first-order closure model. Hence the model which has the TKE closure scheme is capable of simulating important weather systems associated with summer monsoon, such as monsoon depressions and lows that form over the Indian subcontinent quite well compared to the first-order closure model. The present study indicates better performance of the global model with the TKE scheme in the prediction of the monsoon circulation, including the tracks of the depressions over the Indian subcontinent. Medium-range weather prediction has also improved with the use of the TKE closure. However further studies are necessary to improve the forecast, with emphasis on boundary layer processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050253
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  • 5
    Digitale Medien
    Digitale Medien
    The Role of Radiative Transfer in Maintaining the Indian Summer Monsoon Circulation (1997)
    Springer
    Pure and applied geophysics 149 (1997), S. 601-622 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Atmospheric radiative transfer, circulation, Indian summer monsoon, thermal forcing.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The radiative-convective feedback and land-sea thermal forcing play significant roles in maintenance of the summer monsoon circulation over the Indian sub-continent. In this study, the role of radiative transfer in maintaining the monsoon circulation is examined with numerical sensitivity experiments. For this purpose, a sixteen layer primitive equation limited area model is used to perform numerical simulations with and without atmospheric radiative transfer processes parameterized in the model. The initial values and boundary conditions for the numerical integrations of the model are derived from operational analyses of the ECMWF, UK. The results show that the radiative transfer is essential in maintaining the intensity of the low level Somali Jet as well as the upper level Tropical Easterly Jet (TEJ) over the Indian sub-continent and adjoining seas. The meridional circulation over the region is also well simulated. As a result, enough moisture transports from the warm equatorial region to simulate more realistic orographic precipitation in the windward side of the mountains along the West coast of India. Without radiative transfer processes in the model atmosphere the simulated monsoon circulation weakens, moisture transport decreases and the precipitation lessens.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050043
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  • 6
    Digitale Medien
    Digitale Medien
    Use of a Lennard-Jones calculation for molecular diffusivity of pollutant gases in the PBL and its bearing on scavenging models (1986)
    Springer
    Boundary layer meteorology 34 (1986), S. 311-316 
    Details
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Use of a Lennard-Jones calculation for estimation of molecular diffusivity of gases like SO2 for use in scavenging models is recommended. A profile of molecular diffusivity of SO2 in air through the PBL is obtained. Results indicate a change of about 17.5% between the diffusivity values at the surface and at the top of the PBL. The possible changes that could result in scavenging model calculations due to this change are also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00122385
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  • 7
    Digitale Medien
    Digitale Medien
    Mixed-layer characteristics as related to the monsoon climate of New Delhi, India (1994)
    Springer
    Boundary layer meteorology 67 (1994), S. 213-227 
    Details
    ISSN: 1573-1472
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Annual variations of mixed-layer characteristics at New Delhi, India have been studied for a weak monsoon (1987) and a strong monsoon (1988) year. In the weak monsoon year (1987), the maximum mixing depthh max was found to have a value of around 3000 m during the pre-monsoon, less than 2000 m during the summer monsoon, around 2000 m during the post-monsoon, and less than 1000 m in the winter season. For the strong monsoon year (1988),h max values were less than 1987 values for comparable periods throughout the year. The seasonal and yearly differences ofh max were explained by the surface energy balance and potential temperature gradient γ at a time close to sunrise. According to the spatial patterns of γ obtained by an objective analysis of the 850 to 700 hPa layers. mixed-layer characteristics obtained at New Delhi are representative of the north and central regions of India.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00713142
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  • 8
    Digitale Medien
    Digitale Medien
    A Study On Atmospheric Boundary-Layer Characteristics At Anand, India Using Lsp Experimental Data Sets (2000)
    Springer
    Boundary layer meteorology 96 (2000), S. 393-419 
    Details
    ISSN: 1573-1472
    Schlagwort(e): Fluxes ; Land surface processes ; Planetary boundary layer ; Turbulent kinetic energy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract An attempt is made to study the planetary boundary layer (PBL) characteristics during the winter period at Anand (22.4°N, 72.6°E), a semi-arid region, which is located in the western part of India. A one-dimensional turbulent kinetic energy (TKE) closure model is used for the study. The structure of the PBL,which consists of profiles of zonal and meridional components of wind,potential temperature and specific humidity, is simulated. A one-dimensional soil heat and moisture transport parameterization scheme is incorporated for the accurate representation of the energy exchange processes at the soil-atmosphere interface. The diurnal variation of fluxes of sensible heat, latent heat, shortwave radiation, net radiation and soil flux, soil temperature at different depths, Richardson number and TKE at the height of the constant flux layer is studied. The model predictions are compared with the available observations obtained from a special Land Surface Processes (LSP) experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1002699522932
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  • 9
    Digitale Medien
    Digitale Medien
    Effect of three different boundary-layer parameterisations in a regional atmospheric model on the simulation of summer monsoon circulation (1997)
    Springer
    Boundary layer meteorology 84 (1997), S. 363-381 
    Details
    ISSN: 1573-1472
    Schlagwort(e): Indian summer monsoon circulation ; Monsoon depression ; Planetary boundary layer ; Bulk method ; First order closure scheme ; TKE closure scheme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Bulk, first-order and turbulent kinetic energy (TKE) closure schemes are used to parameterise the boundary-layer physics in a high resolution, limited area model. The model was used to simulate the summer monsoon circulations over India. The domain selected included the monsoon trough over northern India, a region of mesoscale convection. A monsoon depression was present at the time of the simulation. The results indicate that the TKE closure scheme combined with the Monin–Obukhov surface-layer similarity relation provided the best 48-hour simulation of the circulation and the rainfall associated with the monsoon depression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1000402013655
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  • 10
    Digitale Medien
    Digitale Medien
    Monsoon rainfall simulations with the Kuo and Betts-Miller schemes (1994)
    Springer
    Meteorology and atmospheric physics 53 (1994), S. 33-49 
    Details
    ISSN: 1436-5065
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Summary Two numerical experiments are performed using a nested grid regional model to study the performance of the Kuo and the Betts-Miller cumulus parameterization schemes in simulating the rainfall during an active monsoon period. Results indicate that the monsoon circulation features, such as the Somali jet and monsoon depression are better simulated with the Kuo scheme. With the Kuo scheme, predicted intensity and associated rainfall of the monsoon depression are in good agreement with the observations. Uncertainty in the adjustment parameters in the Betts-Miller scheme appears to have lead to the poor prediction of rainfall. Also, the Betts-Miller scheme showed considerable sensitivity to the convergence in the lower troposphere in the initial conditions over the Arabian Sea, leading to a prediction of a spurious intense tropical cyclone. This cyclone replaced the normal heat-low over the desert region. Rainfall distribution and its maximum along the west coast of India were predicted better with the Kuo scheme. Area-averaged convective heating rates indicated that the cumulus convection is deeper and more intense with the Kuo scheme. Also, area averaged evaporation rates far exceeded the rainfall rates with the Betts-Miller scheme while with the Kuo scheme these rates are in balance after the spinup period. Forecast erros in the zonally averaged specific humidities indicate that the model atmosphere is more humid with the Betts-Miller scheme.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01031903
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