Sensitivity of Tropical Cyclone Intensity and Structure to Planetary Boundary Layer Parameterization     

Deepika Rai  Sandeep Pattnaik 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(3):473-488

The advanced weather research and forecasting model is used to investigate the influence of planetary boundary layer (PBL) processes on intensity and structure of the storm Phailin (2013). Five simulations are conducted with five PBL schemes; Yonsei University (YSU), Mellor?Yamada?Nakanishi?Niino order2.5 (MYNN2), Assymetric Convective Model2 (ACM2), Medium Range Forecast (MRF), and Bougeault and Lacarrere (BouLac). The simulation duration includes the pre???intensification and rapid intensification phase of Phailin before landfall. Results indicate that during the pre???intensification phase, storm’s track and intensity are not much sensitivity to PBL but structural changes are noted. A significant sensitivity of track and intensity to PBL parameterizations are found during rapid intensification phase. BouLac and MRF produced two extremes with 39 hPa intense and 16 km compact storm for BouLac than MRF. Further analysis reveals an outward movement of air parcel just above the boundary layer which causes spin-down for YSU and MYNN2. BouLac is associated with stronger eddy diffusivity and moisture fluxes within the boundary layer and stronger cyclonic vorticity just above the boundary layer than other experiments. Stronger cyclonic vorticity above the boundary layer in BouLac favors intense updraft, facilitating more moisture transport from the boundary layer to upper layers aiding stronger secondary circulation and robustly intensifying the storm. A relatively deeper and drier inflow layer associated with weaker cyclonic vorticity just above the boundary layer reduces the moisture transport and weaken the secondary circulation for MRF than others.  相似文献   

Modelling of water table variation in response to time-varying recharge from multiple basins using the linearised Boussinesq equation     

S. N. Rai  A. Manglik 《Journal of Hydrology》1999,220(3-4):141-148

A mathematical model is presented to describe the variations of the water table in an unconfined aquifer due to time-varying recharge applied from four rectangular basins. The model is developed by solving the linearised Boussinesq equation using the extended finite Fourier cosine transform. The time-varying recharge rate is approximated by a number of piecewise linear elements of different lengths and slopes depending on the nature of the variation in recharge rate. Application of this model for the prediction of water table fluctuations and in the sensitivity analysis of various controlling parameters on the aquifer response is demonstrated in an example.  相似文献   

Preparation of volume table of SAL (Shorea robusta) - an approach using satellite data     

V. K. Srivastava  A. M. Rai  R. K. Dixit  M. P. Oza  A. Narayana 《International Journal of Applied Earth Observation and Geoinformation》1999,1(3-4)

Sal (Shorea robusta) is an important forest tree species in north and north-eastern India. Large-scale plantations of this species have been raised there under taungya and coppice system of management. The conventional volume table prepared for high sal forest is referred to infer the volume of production of this species. Earlier workers have used aerial remote sensing data to develop volume tables of this species. In the present study a volume table for sal is developed based on remotely sensed satellite data using a regression technique. A two-step method was developed to estimate mean tree volume from satellite data. In step 1, mean crown diameter — an intermediate variable - was estimated from satellite data. In step 2, the estimated mean crown diameter was used to estimate the mean tree volume. Addition of age of the crop as an independent variable improved the predictive ability of the regression equation.  相似文献   

尼泊尔波哈拉谷地若干湖泊的营养状况：过去、现在与将来     

Ash Kumar Rai 《湖泊科学》1998,10(S1):181-201

Harnessing the natural resources is one of the basis of natural economy in developing countries. The wise use of such resources is very important to sustain the balance between immediate benefits and maintenance of the ecosystem. In Phewa, Begnas and Rupa lakes of Pokhara Valley, plankton feeding fish farming in net cage,enclosure and open water stocking is one of the effective example of natural resources utilisation which sustains a number of households in surrounding lakes for economic activities. These lakes are also used for drinking water, hydroelectricity, irrigation and recreation etc. However, the understanding of trophic status of the lakes is very important for long term sustainable use of the lakes in harmony with human activities. Here, we present the trophic status of three lakes of Pokhara Valley and discuss the impacts of human and natural activities on the trophic status of the lake. The study shows that heavy rain fall in the valley during monsoon is one of the strongest natural forces which flush out the accumulated nutrients from the lakes and migrate the eutrophication processes. Recommendations for sustainable use of lake water have also been discussed.  相似文献   

Statistical study of spatial variation of response spectrum using free field records of dense strong motion arrays     

Hideji Kawakami  Shailendra Sharma 《地震工程与结构动力学》1999,28(11):1273-1294

Spatial variation of acceleration response spectra is examined using strong motion records for a large number of events from dense accelerometer arrays at Chiba in Japan and SMART-1 in Lotung, Taiwan. The effects of earthquake component, structural damping, earthquake magnitude, focal depth, epicentral distance, structural time period, and station separation on the intra-event variation of response spectra are examined first through an empirical analysis and then through a least-square regression fit for parametric study. A very large scatter of the response spectra ratio is observed for both arrays, especially for SMART-1 array. The mean values of the ratio vary from 10 to 20 per cent for Chiba array while they vary from 25 to 50 per cent for SMART-1 array. The coefficients of variation of the ratio range from 5 to 25 per cent for Chiba array and 30 to 50 per cent for SMART-1 array. The correlation among response spectra is found to be inversely proportional to station separation and shows frequency dependence. For larger time periods, the correlation is lower and not higher. The correlation is also lower for UD earthquake component as compared to the two horizontal components. For higher damping ratio, the correlation among spectra is higher. The effect of the earthquake magnitude, focal depth and epicentral distance on the spatial variation is complex. The three parameters having implicit interdependence, considering their combined effect, a positive contribution to the value of ratio of response spectra is observed in the case of larger earthquake events. Furthermore, as mentioned above, the spatial variation for SMART-1 array is much larger than that for Chiba array. This difference can be attributed mainly to the difference in distance between the instruments in the two arrays. However, some of the difference is considered to be due to site specific characteristics. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Understanding hydrological processes of glacierized catchments in the western Himalayas by a multi-year tracer-based hydrograph separation analysis     

Tanveer Dar  Nachiketa Rai  Sudhir Kumar  Mohd Aadil Bhat 《水文研究》2024,38(2):e15083

Snow and glacier melt are significant contributors to streamflow in Himalayan catchments, and their increasing contributions serve as key indicators of climate change. Consequently, the quantification of these streamflow components holds significant importance for effective water resource management. In this study, we utilized the spatio-temporal variability of isotopic signatures in stream water, rainfall, winter fresh snow, snowpack, glaciers, springs, and wells, in conjunction with hydrometeorological observations and Snow Cover Area (SCA) data, to identify water sources and develop a conceptual understanding of streamflow dynamics in three catchments (Lidder, Sindh, and Vishow) within the western Himalayas. The following results were obtained: (a) endmember contributions to the streamflow exhibit significant spatial and seasonal variability across the three catchments during 2018–2020; (b) snowmelt dominates streamflow, with average contributions across the entire catchment varying: 59% ± 9%, 55% ± 4%, 56% ± 6%, and 55% ± 9% in Lidder, 43% ± 6%, 38% ± 6%, 32% ± 4%, and 33% ± 5% in Sindh and 45% ± 8%, 40% ± 6%, 39% ± 6%, and 32% ± 5% in Vishow during spring, summer, autumn, and winter seasons, respectively; (c) glacier melt contributions can reach ~30% to streamflow near the source regions during peak summer; (d) The primary uncertainties in streamflow components are attributed to the spatiotemporal variability of tracer signatures of winter fresh snow/snowpack (±1.9% to ±20%); (e)regarding future streamflow components, if the glacier contribution were to disappear completely, the annual average streamflow in Lidder and Sindh could decrease up to ~20%. The depletion of the cryosphere in the region has led to a rapid increase in runoff (1980–1900), but it has also resulted in a significant streamflow reduction due to glacier mass loss and changes in peak streamflow over the past three decades (1990–2020). The findings highlight the significance of environmental isotope analysis, which provides insights into water resources and offers a critical indication of the streamflow response to glacier loss under a changing climate.  相似文献   

Optimization and biokinetic studies on pretreatment of sludge for enhancing biogas production     

P. Divyalakshmi  D. Murugan  M. Sivarajan  A. Sivasamy  P. Saravanan  C. L. Rai 《International Journal of Environmental Science and Technology》2017,14(4):813-822

Excess sludge generation is a major problem in biological effluent treatment processes. Utilization of excess sludge for gas production is an attractive route, which could be enhanced by pretreatment methods. This study involves two sets of experiments. The first set covers mechanical pretreatment of both feed and inoculum. The second set involves alkaline and mechanical treatments of feed and only mechanical treatment of inoculum. Response surface methodology was used for experimental design, analysis and optimization. The optimized mechanical treatment volume of feed was found to be 50%. Diligent mechanical treatment of inoculum resulted in enhanced microbial activity and improved gas production. Reduction in volatile solids, proteins and carbohydrates was observed to a maximum of 63, 84 and 78.5%, respectively. Feed was subjected to alkali treatment in order to reduce mechanical energy input and to improve solubilization. Compared to mechanical treatment alone, enhanced gas production of about 15% was observed at an optimized pH of 11.8 and SRT of 21 days. A biokinetic model was formulated, simulated and validated for the degradation of organics and gas production.  相似文献   

Estimation of snow and glacial melt contribution through stable isotopes and assessment of its impact on river morphology through stream power approach in two Himalayan river basins     

L. Sardine Varay  S. P. Rai  S. K. Singh  Vikrant Jain 《Environmental Earth Sciences》2017,76(23):809

The impact of increased temperature on the Third Pole, as the Himalayas is referred to, and the likely cascading impacts on the general downstream hydrology have been widely noted. However, the impact on fluvial geomorphology has not received specific attention. Change in the glacial domain in terms of melt increase will change discharge and sediment flux into fluvial system, which will induce changes in fluvial processes and forms. The present work attempts to study this process-based glacio-fluvial coupling in the two neighbouring glaciated river basins in the Northwest Himalaya, viz., the Sutlej and the Yamuna river basins till the mountain front. A total of 194 samples of river, tributary and groundwater of pre- and post-monsoon seasons in the two river basins were analysed for stable isotopes. The trend of δ¹⁸O and electrical conductivity along the mainstream gives qualitative idea on the influence of headwaters in the downstream of the catchment thereby allowing inference on melt contribution. Further, two component mixing model using stable oxygen isotope of two seasons water samples showed that melt contributes about 41.1–66.8 and 6.6–10.6% at different points to the total river discharge in the Sutlej and the Tons River (the glaciated, major tributary of the Yamuna River) basins, respectively. For different scenarios of increase in melt, stream power increase in the Sutlej River basin is significant as opposed to the Tons River. River channel in the Sutlej River basin will be significantly more impacted in comparison with the Yamuna River system.  相似文献   

Magnetic and radiometric signatures over a Proterozoic massive sulfide setting of northern fringe of Dalma Volcanics,eastern India: An implication to metallogeny     

Pramod Kumar Yadav  P. K. Adhikari  Shalivahan  Anurag Tripathi  Shailendra Singh  Roshan K. Singh  Ashish K. Bage 《Journal of the Geological Society of India》2017,89(6):705-710

Magnetic and radiometric surveys were carried out over a felsic dominated rifted margin of Proterozoic volcanic terrain of a mobile belt in the eastern India. The studies were made in blocks I and II of 0.65 sq km and 0.70 sq km respectively over a previously identified conductor in the northern fringe of Dalma Volcanics (DVs). In general, both the blocks show high magnetic signature associated with sulfide mineralisation. The interpretation of magnetic data suggests that nature of the causative source is mainly horizontal cylinder in both the blocks. The depth to the top of the causative source is about 25 m in both the blocks and extends upto 60 m in block I and 40m in block II. Gamma count rate exhibits about a factor of two to three enhancements above the field background for both the blocks. The obtained iso-rad maps are similar to uranium and copper belt in the Singhbhum shear zone south of the study area. The anomalous radiometric signature of the residual soil/rock of the area indicates towards hydrothermal alteration. The detailed magnetic surveys and preliminary iso-rads results seems quite encouraging and may be attributed to VMS setting in the area and potential sulfide mineralisation with uranium mineral association in the DVs province.  相似文献   

In‐plane and out‐of‐plane behavior of confined masonry walls for various toothing and openings details and prediction of their strength and stiffness          下载免费PDF全文

Vaibhav Singhal  Durgesh C. Rai 《地震工程与结构动力学》2016,45(15):2551-2569

Eight half‐scale brick masonry walls were tested to study two important aspects of confined masonry (CM) walls related to its seismic behavior under in‐plane and out‐of‐plane loads. Four solid wall specimens tested to investigate the role of type of interface between the masonry and tie‐columns, such as toothing varying from none to every course. The other four specimens with openings were tested to study the effectiveness of various strengthening options around opening to mitigate their negative influence. In the set of four walls, one wall was infilled frame while the other three were CM walls of different configurations. The experimental results were further used to determine the accuracy of various existing models in predicting the in‐plane response quantities of CM walls. Confined masonry walls maintained structural integrity even when severely damaged and performed much better than infill frames. No significant effect of toothing details was noticed although toothing at every brick course was preferred for better post‐peak response. For perforated walls, provision of vertical elements along with continuous horizontal bands around openings was more effective in improving the overall response. Several empirical and semi‐empirical equations are available to estimate the lateral strength and stiffness of CM walls, but those including the contribution of longitudinal reinforcement in tie‐columns provided better predictions. The available equations along with reduction factors proposed for infills could not provide good estimates of strength and stiffness for perforated CM walls. However, recently proposed relations correlating strength/stiffness with the degree of confinement provided reasonable predictions for all wall specimens. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献