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Monsoon Season (monsoon + season)
Selected AbstractsIs rainfall intensity significant in the rainfall,runoff process within tropical rainforests of northeast Queensland?HYDROLOGICAL PROCESSES, Issue 18 2010The Hewlett regression analyses revisited Abstract Following the statistical analyses of long-term rainfall-runoff records from research basins in humid temperate latitudes, Hewlett and co-workers extended the global challenge to disprove their findings that rainfall intensity was non-significant. This paper responds to Hewlett's challenge as no preceding analyses have involved forested basins in a tropical cyclone-prone area. Based on a 7 year rainfall-runoff record, quickflow (QF), peak flow (QP) and quickflow response ratios (QRR) were regressed as dependent variables against rainfall parameters (intensity, Pi, amount, P), storm duration, D and antecedent flow, I. These data sets were categorised into total streamflow (Q) classes and stratified into three seasons, (monsoon, post-monsoon and dry) for forested and cleared catchments. Where rainfall variable collinearity met acceptable levels, the addition of Pi to regression models including P, D, I contributed up to 9% and 66% of the respective variations in quickflow and peak flow. For the highest Q storm classes (monsoon), Pi alone accounted for up to 67% and 91% of the variation in QF and QP respectively and was the dominant influence on QP for all seasons. The very high rainfall intensities experienced in the monsoon season is a causal factor why these results differ from those of other research drainage basins. Surprisingly, Pi continued to have a significant influence on QF for dry season classes when less-intense rainfall occurs. Further the results were similar for both catchments across all seasons. P was the dominant independent variable affecting QF above a threshold Q of 50 mm (monsoon), as rainfall contributes directly to saturation overland flow and return flow under saturated conditions. Further although QRR increased with increasing Q for each season, the regression results for that parameter were poor possibly due to the non-linearity of the rainfall-runoff relationship. Copyright © 2010 John Wiley & Sons, Ltd. [source] Large-scale summer monsoon rainfall over India and its relation to 850 hPa wind shearHYDROLOGICAL PROCESSES, Issue 15 2007V. S. Prasad Abstract The daily variations of the horizontal wind shear at the 850 hPa level between a southern region (5,15°N, 40,80°E; Zone 1) and a northern region (20,30°N, 70,90°E; Zone 2) during the period 1979,2002 were investigated. Investigations revealed that the changes of this wind shear on a daily basis are directly related to the large-scale rainfall over the Indian region during the monsoon season. The wind shear of zonal wind together with Zone 2 is useful for determining active, weak and break periods of the Indian summer monsoon (ISM). Thus, the Horizontal Wind Shear can be used as a dynamical circulation Index (HWSI) for studying ISM variability. Copyright © 2007 John Wiley & Sons, Ltd. [source] Stable isotopes in the source waters of the Yamuna and its tributaries: seasonal and altitudinal variations and relation to major cationsHYDROLOGICAL PROCESSES, Issue 17 2002Tarun K. Dalai Abstract Water samples from the Yamuna and its tributaries, one of the major river systems draining the Himalaya, have been analysed for their stable oxygen and hydrogen isotopes during three seasons (summer, monsoon and post-monsoon). The data show clear seasonal and altitudinal variations; waters from higher altitudes and those collected during monsoon season are characterized by relatively depleted isotopic composition. Regression analysis of ,D,,18O data of samples collected during summer and monsoon seasons shows that the slope of the best-fit lines are nearly identical to those of precipitation at New Delhi for the same period. The similarity in their slopes suggests that the isotopic composition of precipitation contributing water to these rivers are reasonably well preserved in both monsoon and non-monsoon seasons, however, during the non-monsoon period both rainfall and river waters carry signatures of evaporation. The ,deuterium excess' in river waters during the three seasons though overlap with each other, the values during October are higher. This can be understood in terms of recycled moisture contributions to precipitation. The ,altitude effect' for ,18O in these waters is determined to be 0·11, per 100 m, a factor of about two less than that reported for the Ganga source waters from similar altitudinal range. The variability in altitude effects in rivers draining the Himalaya seems to be controlled by the ,amount effect' associated with the monsoon. The significant spatial variability in altitude effect in these river basins, which are a few hundred kilometers apart, suggests that reconstruction of palaeoelevation in the Himalaya, based on ,18O-altitude gradients, would depend critically on its proper assessment in the region. This study has established a relationship between total cation abundance and ,18O in waters of the Yamuna mainstream; total cations (corrected for cyclic components) double for a 1·4 km decrease in altitude as the Yamuna flows downstream. Copyright © 2002 John Wiley & Sons, Ltd. [source] Interannual variability of atmospheric water balance over South Peninsular India and Sri Lanka during northeast monsoon seasonINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2008Venkatraman Prasanna Abstract In this study we have investigated atmospheric water balance over South Peninsular India and Sri Lanka during the months October to December (OND) using computed moisture convergence (C) and residual evaporation (E) from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and Global Precipitation and Climatology Project (GPCP) precipitation data. The interannual signatures of OND precipitation, moisture convergence and evaporation over the South Peninsular India and Sri Lanka have been captured. The spatial and temporal characteristics of the hydrological cycle and the contribution of evaporation (E) and convergence (C) to precipitation (P) are discussed in detail. Over the South Peninsular India and Sri Lanka, evaporation (E) dominates during the entire monsoon months (OND). However, the interannual variability of precipitation over the domain is not necessarily influenced by the same criteria which influences the mean seasonal precipitation. The moisture from the Indian Ocean (IO) sector also modulates the precipitation over this region on a year-to-year basis. It has been noted that the positive northeast monsoon rainfall (NEMR) is associated with El Nino coupled with IO dipole, but negative NEMR is weakly associated only with La Nina over South Peninsular India and Sri Lanka. There also exists a significant land-atmospheric interaction over the region in modulating the hydrological cycle on a year-to-year basis. Copyright © 2008 Royal Meteorological Society [source] A mark,recapture study of the caecilian amphibian Gegeneophis ramaswamii (Amphibia: Gymnophiona: Caeciliidae) in southern IndiaJOURNAL OF ZOOLOGY, Issue 2 2003G. John Measey Abstract The potentially important ecology of subterranean predators of soil ecosystem engineers is poorly understood. This is especially true of caecilian amphibians (Gymnophiona) for which there are virtually no quantitative data. Results of the first field trials of permanent marking in caecilians are presented. A preliminary assessment is made of the efficacy of mark,recapture studies for estimating population size of Gegeneophis ramaswamii Taylor in 100 m2 of low intensity agriculture in Kerala, India. Over three sampling occasions spanning 58 days of the monsoon season, 114 individuals were captured, 104 marked and released, and 21 recaptured. Models estimate an open population of 60 individuals (95% confidence interval of 45.2 to 151.3), and a closed population of 236 (95% confidence interval of 174 to 351). A census interpretation of the raw capture data gives densities of about 0.31 to 0.48 m,2. Results suggest large movement in and out of the sampled area during the study. Despite caveats associated with these data, progress is made in identifying potential limitations and improvements in the methods used. This study highlights the paucity of knowledge of caecilian ecology, and the need for long-term studies to elucidate further ecological information and to monitor populations. [source] The Chalan beel in Bangladesh: Habitat and biodiversity degradation, and implications for future managementLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2009Mostafa A. R. Hossain Abstract This study provides an overview of the current resources and fisheries status of the Chalan beel, and identifies the scope of opportunities to evolve existing fisheries management strategies, focusing on fish biodiversity conservation. Chalan beel is the largest, most important watershed in the North Central Bangladesh, and covers an area of about 375 km2 during the monsoon season. The watershed serves about 5 million people, predominantly through fisheries and agricultural activities. Although considerably degraded over time, Chalan beel still supports a diverse ichthyofauna of major importance to the local economy and people's livelihoods. The Chalan beel area incorporates 21 rivers and 93 smaller seasonal beels of varying size. Most of the rivers and beels are at risk of partial or total degradation, as a result of agricultural encroachment, siltation and other anthropogenic activities. During the study, , 83% of the rivers, and 68% of the beels in the lean season, shrunk to 0,5% of their maximum (monsoon) water-spread area during the dry season (i.e. critical levels for survival of many fish species). A fish catch survey was carried out in the main fishing season (July to December) over two successive years in the three most important catchment areas; namely, the Gumani, Baral and Katagang Rivers. A total of 72 sampling episodes yielded 9818 individuals, representing 114 fish species. The most abundant fish species during the 2-year study period were punti (Puntius sophore and Puntius ticto), followed by chanda (Chanda nama and Parambassis ranga), chapila (Gudusia chapra) and tengra (Mystus vittatus). The study results indicate at least 19 fish species once considered abundant can now be classified as threatened, with a possibility of local extinction. The mean fish catch was 2.08 ± 0.49 kg, and 1.29 ± 0.32 kg per hour per person, by suti jal (set bag net , the most common gear used in the beel) in 2005 and 2006, respectively, with a significant (P < 0.05) variation among catches in months and years at all three sample sites. In 2005,2006, the annual fish production in Chalan beel was 12 217 tonnes, being less than half of the production observed in 1982. The stakeholders identified several major causes they thought were directly responsible for the continued decrease in fish production and biodiversity of the beel area. Several management strategies were suggested by the same stakeholders, and the findings are discussed in the context of overall developments in the Chalan beel fisheries related to habitat and biodiversity management. [source] Subsurface drainage for reversing degradation of waterlogged saline landsLAND DEGRADATION AND DEVELOPMENT, Issue 6 2006D. P. Sharma Abstract In irrigated agriculture of arid and semiarid regions waterlogging coupled with salinity is a serious problem. Experimental evidence at several locations has led to the realization that subsurface drainage is an essential intervention to reverse the processes of land degradation responsible for the formation of waterlogged saline lands. This paper presents the results of a study conducted from 1995 to 2000 to evaluate the impacts of subsurface drainage on soil properties, groundwater-table behaviour and crop productivity in a waterlogged saline area of 2200,ha. A subsurface drainage system was installed at 1·6,m depth with 60,m drain spacing covering an area of 1200,ha (23 blocks) during 1997,99 and compared with an undrained block of 1000,ha. Subsurface drainage facilitated the reclamation of waterlogged saline lands and a decrease in the soil salinity (ECe, dS,m,1) that ranged from 16·0 to 66·3,per,cent in different blocks. On average, 35·7,per,cent decrease in salt content was observed when compared with the initial value. Provision of subsurface drainage controlled the water-table below the root zone during the monsoon season and helped in bringing the soil to optimum moisture content for the sowing of winter crops. In the drained area, the increase in yields of different crops ranged from 18·8 to 27·6,per,cent. However, in the undrained area the yield of different crops decreased due to the increased waterlogging and soil salinity problems. Overall the results indicated that investment in subsurface drainage is a viable option for reversing the land degradation of waterlogged saline lands in a monsoon climate. Copyright © 2006 John Wiley & Sons, Ltd. [source] Erratum: Bias-free rainfall forecast and temperature trend-based temperature forecast using T-170 model output during the monsoon seasonMETEOROLOGICAL APPLICATIONS, Issue 3 2010Rashmi Bhardwaj No abstract is available for this article. [source] Statistical interpretation of NWP products in IndiaMETEOROLOGICAL APPLICATIONS, Issue 1 2002Parvinder Maini Although numerical weather prediction (NWP) models provide an objective forecast, poor representation of local topography and other features in these models, necessitates statistical interpretation (SI) of NWP products in terms of local weather. The Perfect Prognostic Method (PPM) is one of the techniques for accomplishing this. At the National Center for Medium Range Weather Forecasting, PPM models for precipitation (quantitative, probability, yes/no) and maximum/minimum temperatures are developed for monsoon season by using analyses from the European Centre for Medium-Range Weather Forecasts. The SI forecast is then obtained by using these PPM models and output from the operational NWP model at the Center. Direct model output (DMO) obtained from the NWP model and the SI forecast are verified against the actual observations. The present study shows the verification scores obtained during the 1997 monsoon season for 10 locations in India. The results show that the SI forecast has good skill and is an improvement over DMO. Copyright © 2002 Royal Meteorological Society. [source] An objective definition of the Indian summer monsoon season and a new perspective on the ENSO,monsoon relationshipTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 624 2007Prince K. Xavier The concept of an interannually varying Indian summer monsoon season is introduced here, considering that the duration of the primary driving of the Indian monsoon,the large-scale meridional gradient of the deep tropospheric heat source,may vary from one year to another. Onset (withdrawal) is defined as the day when the tropospheric heat source shifts from south to north (north to south). This physical principle leads to a new thermodynamic index of the seasonal mean monsoon. While the traditional measure of seasonal rainfall, averaged from 1 June to 30 September, indicates a breakdown of the ENSO,monsoon relationship in recent decades, it is argued that this breakdown is partly due to the inappropriate definition of a fixed monsoon season. With a new physically based definition of the seasonal mean, the ENSO,monsoon relationship has remained steady over the decades. El Niño (La Niña) events contract (expand) the season, and thus decrease (increase) the seasonal mean monsoon by setting up persistent negative (positive) tropospheric temperature (TT) anomalies over the southern Eurasian region. Thus, we propose a new pathway, whereby the Indian summer monsoon could be influenced by remote climatic phenomena via modification of TT over Eurasia. Diagnostics of the onset and withdrawal processes suggest that onset delay is due to the enhanced adiabatic subsidence that inhibits vertical mixing of sensible heating from warm landmass during the pre-monsoon months. On the other hand, the major factor that determines whether the withdrawal is early or late is the horizontal advective cooling. Most of the late (early) onsets and early (late) withdrawals are associated with El Niño (La Niña). This link between the ENSO and the monsoon is realized through vertical and horizontal advections associated with the stationary waves in the upper troposphere set up by the tropical ENSO heating. Copyright © 2007 Royal Meteorological Society [source] Response of the Asian summer monsoon to changes in El Niño propertiesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 607 2005H. Annamalai Abstract Diagnostics from observed precipitation and National Centers for Environmental Prediction,National Center for Atmospheric Research re-analysis products reveal that after the 1976,77 climate shift in the Pacific there was a dramatic change in the response of the Indian summer monsoon (ISM) to El Niño, particularly during the months of July and August. Based on 1950,75 (PRE76) and 1977,2001 (POST76) El Niño composites: the western North Pacific monsoon (WNPM) was stronger than normal in both periods; the ISM was weaker than normal during the entire monsoon season in PRE76, but in POST76 was weaker only during the onset and withdrawal phases. In terms of observed sea surface temperature (SST) during July,August, the major differences between the two periods are the presence of cold SST anomalies over the Indo,Pacific warm pool and the intensity of warm SST anomalies in the central Pacific in POST76. The effect of these differences on the ISM is investigated in a suite of experiments with an Atmospheric General Circulation Model (AGCM) that has a realistic monsoon precipitation climatology. Separate ten-member ensemble simulations with the AGCM were conducted for PRE76 and POST76 El Niño events with SST anomalies inserted as follows: (i) tropical Indo,Pacific (TIP), (ii) tropical Pacific only (TPO), and (iii) tropical Indian Ocean only (TIO). Qualitatively, TPO solutions reproduce the observed differences in the monsoon response in both periods. Specifically, during July,August of POST76 the cold SST anomalies in conjunction with remote subsidence suppress precipitation (3,5 mm day,1) over the maritime continent and equatorial central Indian Ocean. Inclusion of Indian Ocean SST anomalies in the TIP runs further suppresses precipitation over the entire equatorial Indian Ocean. The low-level anticyclonic circulation anomalies that develop as a Rossby-wave response to these convective anomalies increase the south-westerlies over the northern Indian Ocean, and favour a stronger ISM and WNPM. During PRE76 the non-occurrence of cold SST anomalies over the Indo,Pacific warm pool reinforces El Niño's suppression on the ISM. In contrast, TIO solutions show a reduced ISM during July,August of POST76; the solutions, however, show a significant effect on the WNPM during both PRE76 and POST76 periods. It is argued that SSTs over the entire tropical Indo,Pacific region need to be considered to understand the El Niño Southern Oscillation,monsoon linkage, and to make predictions of rainfall over India and the western North Pacific. Copyright © 2005 Royal Meteorological Society [source] Temporal variability in fish larval supply to Malindi Marine Park, coastal KenyaAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2009Boaz Kaunda-Arara Abstract 1.Larval supply to reef sites influences adult population structure, reef connectivity and conservation potential of marine reserves, but few studies have examined this topic in the Western Indian Ocean (WIO). 2.Fish larval supply to Malindi Marine Park in Kenya was studied using light-traps for a period extending from March 2005 to June 2006. The traps caught pre-settlement fish larvae at two sites spread across the park. Catch rates (number trap,1night,1) were used to represent larval abundance and to test the influence of seasonality and habitat characteristics on larval abundance in the park. 3.Thirty-three species of reef fish larvae in 15 families were sampled. Larval supply to the park was more diverse during the north-east monsoon season (30 species) than in the south-east monsoon season (15 species), with inter-annual variability in abundance. Higher catch rates of larvae occurred in the north-east monsoon month of March in both 2005 and 2006 and the inter-monsoon month of September 2005. 4.Family-specific temporal variation in larval abundance showed dominance of the families Apogonidae and Caesionidae in the park, with higher abundance during the north-east monsoon months. A few families (e.g. Canthigasteridae) showed dominance during the south-east monsoon season. Regression and rank Spearman correlation analyses indicated positive correlation of chlorophyll-a with larval supply while water depth had significant negative correlation with abundance of the Apogonidae and Caesionidae. 5.On a short-term temporal scale larval abundance in the park was highly correlated with the new moon lunar phase more than the full moon. However, on a long-term scale (16 months) larval supply to the park was significant only over a 2-month period and was correlated with environmental productivity more than ambient temperature. These results are useful in understanding the role of larval supply in structuring adult fish populations and the factors that force larval flux at reef sites. Copyright © 2009 John Wiley & Sons, Ltd. [source] Changes of State: Slow-Motion Trauma in the Gangetic Plains of IndiaARCHITECTURAL DESIGN, Issue 5 2010Anthony Acciavatti Abstract In recent years, the vicissitudes wrought by harsh weather patterns and natural disasters have resulted in hurricanes and earthquakes and had a catastrophic impact on people's lives. The Ganges River Corridor in northern India is a region that perennially undergoes extreme changes in weather and climate with the onslaught of the monsoon season. AnthonyAcciavatti, in his Dynamic Atlas series of drawings, has measured the effects of rainfall and agrarian processes in relation to the fast-paced modes of urbanisation in the area. Copyright © 2010 John Wiley & Sons, Ltd. [source] Black carbon aerosol mass concentration variation in urban and rural environments of India,a case studyATMOSPHERIC SCIENCE LETTERS, Issue 1 2009K. V. S. Badarinath Abstract The present study provides an account of the black carbon (BC) aerosol mass concentration variation in contrasting environments of India corresponding to the urban and rural areas of Hyderabad and Anantapur during August 2006. The study period corresponds to the monsoon season over the Indian region. The diurnal variation of BC showed two peaks, during morning and late evening, which are mostly, related to the diurnal changes in the local boundary layer and traffic density patterns. BC mass concentrations over Hyderabad are estimated to be 92% higher compared to those at the Anantapur site suggesting considerable contrast in its spatial variations. Copyright © 2009 Royal Meteorological Society [source] Scavenging efficiency of rainfall on black carbon aerosols over an urban environmentATMOSPHERIC SCIENCE LETTERS, Issue 3 2005K. Madhavi Latha Abstract Black carbon (BC) aerosols are the optically absorbing part of carbonaceous aerosols that have significantly different optical and radiative properties. The present study addresses the estimation of black carbon aerosol scavenging coefficient by using ground-based measurements over an urban environment of India, namely, Hyderabad. Extensive ground measurements of black carbon have been carried out during January to December 2004 over a tropical urban environment of Hyderabad. Seasonal variations of black carbon aerosol mass concentration showed high values during dry season and low values during monsoon season. The diurnal variations of BC suggest that the concentrations increased by a factor of ,2 during morning and evening hours compared to afternoon hours. Drastic reduction in black carbon aerosol loading has been observed during rainy days. The statistical fit between black carbon aerosol mass concentration and rainfall suggests the reduction of ,3.6 µg/m3 in atmospheric black carbon aerosol loading for every 1-mm increase in rainfall intensity over the study area. The scavenging coefficient of black carbon aerosols is found to be 1.64 × 10,5 s,1. © Crown Copyright 2005. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] Skill of statistical interpretation forecasting system during monsoon season in IndiaATMOSPHERIC SCIENCE LETTERS, Issue 1 2002Ashok Kumar Abstract An evaluation of statistical interpretation(SI) forecast skill for rainfall and maximum/minimum temperature during monsoon season (June,September) is presented. A brief description of the methodology used for SI forecast and data used is also given. The skill of SI forecast is calculated during 1999, monsoon and has been found encouraging. Copyright © 2002 Royal Meteorological Society. [source] Post-wildfire changes in suspended sediment rating curves: Sabino Canyon, ArizonaHYDROLOGICAL PROCESSES, Issue 11 2007Sharon L. E. Desilets Abstract Wildfire has been shown to increase erosion by several orders of magnitude, but knowledge regarding short-term variations in post-fire sediment transport processes has been lacking. We present a detailed analysis of the immediate post-fire sediment dynamics in a semi-arid basin in the southwestern USA based on suspended sediment rating curves. During June and July 2003, the Aspen Fire in the Coronado National Forest of southern Arizona burned an area of 343 km2. Surface water samples were collected in an affected watershed using an event-based sampling strategy. Sediment rating parameters were determined for individual storm events during the first 18 months after the fire. The highest sediment concentrations were observed immediately after the fire. Through the two subsequent monsoon seasons there was a progressive change in rating parameters related to the preferential removal of fine to coarse sediment. During the corresponding winter seasons, there was a lower supply of sediment from the hillslopes, resulting in a time-invariant set of sediment rating parameters. A sediment mass-balance model corroborated the physical interpretations. The temporal variability in the sediment rating parameters demonstrates the importance of storm-based sampling in areas with intense monsoon activity to characterize post-fire sediment transport accurately. In particular, recovery of rating parameters depends on the number of high-intensity rainstorms. These findings can be used to constrain rapid assessment fire-response models for planning mitigation activities. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||