Simulation of a Himalayan cloudburst event
Someshwar Das 1, ∗,Raghavendra Ashrit 1 and M W Moncrieff 2
1 National Center for Medium Range Weather Forecasting, Noida 201 307, India.
2 National Center for Atmospheric Research, Boulder CO 80301, USA.
∗e-mail: somesh@ncmrwf.gov.in

Abstract: Intense rainfall often leads to floods and landslides in the Himalayan region even with rainfall amounts that are considered comparatively moderate over the plains;for example,‘cloudbursts ’, which are devastating convective phenomena producing sudden high-intensity rainfall ( ~10 cm per hour)over a small area.Early prediction and warning of such severe local weather systems is crucial to mitigate societal impact arising from the accompanying flash floods.We examine a cloudburst event in the Himalayan region at Shillagarh village in the early hours of 16 July 2003.The storm lasted for less than half an hour, followed by flash floods that a ffected hundreds of people.We examine the fidelity of MM5 con figured with multiple-nested domains (81,27,9 and 3 km grid-resolution)for predicting a cloudburst event with attention to horizontal resolution and the cloud microphysics parameterization.The MM5 model predicts the rainfall amount 24 hours in advance.
However,the location of the cloudburst is displaced by tens of kilometers.


Fast computation of Hankel Transform using orthonormal exponential approximation of complex kernel function
Pravin K Gupta 1 ,Sri Niwas 1 and Neeta Chaudhary 2
1 Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee 247 667, India.
2 Oil and Natural Gas Corporation, Priyadarshini Building, Sion, Mumbai, India.

Abstract: The computation of electromagnetic (EM)fields,for 1-D layered earth model,requires evaluation of Hankel Transform (HT)of the EM kernel function.The digital filtering is the most widely used technique to evaluate HT integrals.However,it has some obvious shortcomings.We present an alternative scheme,based on an orthonormal exponential approximation of the kernel function, for evaluating HT integrals.This approximation of the kernel function was chosen because the analytical solution of HT of an exponential function is readily available in literature.This expansion reduces the integral to a simple algebraic sum.The implementation of such a scheme requires that the weights and the exponents of the exponential function be estimated.The exponents were estimated through a guided search algorithm while the weights were obtained using Marquardt matrix inversion method.The algorithm was tested on analytical HT pairs available in literature. The results are compared with those obtained using the digital filtering technique with Anderson filters.The field curves for four types (A-,K-,H-and Q-type)of 3-layer earth models are generated using the present scheme and compared with the corresponding curves obtained using the Anderson scheme.It is concluded that the present scheme is more accurate than the Anderson scheme.


Retrieval of stratospheric O and NO vertical profiles using zenith scattered light observations
G S Meena摯瑬敳獩 ,C S Bhosale D B Jadhav
Indian Institute of Tropical Meteorology, Pashan, Pune 411 008, India.
∗e-mail: gsm@tropmet.res.in

Abstract:Daily zenith scattered light intensity observations were carried out in the morning twilight hours using home-made UV-visible spectrometer over the tropical station Pune (18 ◦31 ,73 ◦51 )for the years 2000 –2003.These observations are obtained in the spectral range 462 –498 nm for the solar zenith angles (SZAs)varying from 87 ◦to 91 .5 ◦.An algorithm has been developed to retrieve vertical pro files of ozone (O 3 and nitrogen dioxide (NO 2 from ground-based measurements using the Chahine iteration method.This retrieval method has been checked using measured and recalculated slant column densities (SCDs)and they are found to be well matching.O 3 and NO 2 vertical profiles have been retrieved using a set of their air mass factors (AMFs)and SCDs measured over a range of 87 –91 .5 ◦SZA during the morning.The vertical pro files obtained by this method are compared with Umkehr pro files and ozonesondes and they are found to be in good agreement.The bulk of the column density is found near layer 20 –25 km.Daily total column densities (TCDs)of O 3 and NO 2 along with their stratospheric and tropospheric counterparts are derived using their vertical pro files for the period 2000 –2003.The total column,stratospheric column and tropospheric column amounts of both trace gases are found to be maximum in summer and minimum in the winter season.Increasing trend is found in column density of NO 2 in stratospheric,tropospheric and surface layers,but no trend is observed in O 3 columns for above layers during the period 2000 –2003.


2-D deformation of two welded half-spaces due to a blind dip-slip fault
Sunita Rani摯瑬敳獩 and Neeru Bala
Department of Mathematics,Guru Jambheshwar University,Hisar 125 001,India.
∗e-mail:s −b −rani@redi ffmail.com

Abstract:The solution of two-dimensional problem of an interface breaking long inclined dip-slip fault in two welded half-spaces is well known.The purpose of this note is to obtain the corresponding solution for a blind fault.The solution is valid for arbitrary values of the fault-depth and the dip angle.Graphs showing the variation of the displacement field with the distance from the fault, for di fferent values of fault depth and dip angle are presented.Contour maps showing the stress field around a long dip-slip fault are also obtained.


Amino sugars in suspended particulate matter from the Bay of Bengal during the summer monsoon of 2001
Loreta Fernandes Fraddry D’Souza S G P Matondkar and Narayan B Bhosle摯瑬敳獩
National Institute of Oceanography, Dona Paula, Goa 403 004, India.
∗e-mail: bhosle@nio.org

Abstract:Amino sugars (AS)are important constituents of organic matter.However,very little is known about their cycling in marine waters.In this research,we assessed the distribution and cycling of these compounds in waters of the Bay of Bengal.For this purpose,samples of suspended particulate matter (SPM)were collected from 8 depths (surface to 1000 m)at 6 locations during the 166th cruise of the ORV Sagar Kanya in the Bay of Bengal in July/August 2001.The SPM samples were analysed for particulate organic carbon (POC),particulate nitrogen (PN)and AS concentrations and composition.The AS varied between 0.4 and 17.5 nmol/l.Concentrations were high in the surface waters and generally decreased with increasing depth.AS concentration decreased from the south to north.AS accounted for 0.01 to 0.71%and 0.05 to 2.37%of POC and PN,respectively. Rapid decrease in AS-C%and AS-N%with depth indicates that these compounds were preferentially degraded relative to bulk POC and PN.The composition of AS suggests that glucosamine (GLU-N)and galactosamine (GAL-N)were present in the surface SPM samples,and their abundance decreased from surface downwards.Relatively,low values of GLU-N/GAL-N ratio indicate that the organic matter was mostly derived from the detritus of micro-organisms.Our data suggest that chitin,a polymer of the glucosamine produced by many marine organisms was not the major source of AS in the Bay.Rapid cycling of these compounds indicates their importance in the cycling of nitrogen in marine waters.



Seaweed floristic studies along tsunami a ffected Indian coasts:A litmus test scenario after 26th December 2004
Vaibhav A Mantri
Central Salt &Marine Chemicals Research Institute,Bhavnagar 364 002,Gujarat,India.
e-mail:vaibhav@csmcri.org

Abstract:On 26th December 2004,the world witnessed the devastating power of tsunami,a ffecting many countries,bordering the Indian Ocean region.This has caused signi ficant changes in the shallow and intertidal regions of the Indian coast,especially the Andaman and Nicobar Islands,Tamil Nadu, Kerala and Pondicherry.The baseline data on biomass availability and distribution of benthic intertidal seaweed species were collected immediately after this catastrophic event by spot surveying 11 selected localities of the above-mentioned regions.In all,45 species belonging to 31 genera were recorded during the present survey,the maximum number of seaweed species were recorded at Thirumullavarum,Kerala with the minimum at Car Nicobar,Andaman and Nicobar Islands. A very di fferent trend was observed in the case of biomass availability at some locations which was due to the in fluence of habitat suitability over the tsunami damage.The details of this study have been provided in the present communication.


Climate induced changes in the circulation and dispersal patterns of the fluvial sources during late Quaternary inthe middle Bengal Fan
Onkar S Chauhan 1, ∗and E Vogelsang 2
1 National Institute of Oceanography, Dona Paula, Goa 403 004, India.
2 Institut f¨ ur Geowissenschaften, Universit¨ at Kiel, Olshausenstrasse 40, D - 24118 Kiel, Germany.
∗e-mail: onkar@nio.org

Abstract:From a transact along 15 ◦N latitude in the middle Bengal Fan,temporal and spatial variations in the granulometric parameters and clay minerals in 14 C dated box cores from the eastern,the central and the western regions were studied to determine climate induced changes in the hydrography. Clay assemblages have spatial and temporal changes and are markedly di fferent in the eastern and the western bay.From a high abundance of the clay smectite,which has its major source in the Deccan Basalt in peninsular India,it is inferred that the western bay is predominantly a depocenter of ‘peninsular sources ’.The eastern and the central regions of the bay,however, mostly receive sediments of the ‘Himalayan source ’.Related to unstable climate,the reported dominant illite –chlorite (I +C)assemblage in the eastern region of the bay (I +C >60%smectite <15%),between 18 and 12.6 ka BP,points to a predominant supply from the Himalayan sources through equatorwards dispersal by the winter hydrography.Higher smectite,and reduced clays of the Himalayan sources (smectite >25%;I +C >45%)are reported also after 12.5 ka BP from the eastern bay.These are interpreted as evidences of an intensi fied SW monsoon and associated change in the dispersal pattern by stronger summer monsoon hydrography which supports across bay dispersal by anticyclonic gyre.The in fluence of climate on hydrographic changes is consistent during the short events of arid climate (weak NE monsoon)in Holocene in core 31/1(western bay), in which the enhanced contents of the clays of the Himalayan sources are observed (smectite <40% I +C >50%).These findings have implications for climate regulated in fluence of fluvial processes over the areas,hitherto,considered una ffected by the Indian peninsular fluvial sources.



Modeling of groundwater flow for Mujib aquifer, Jordan
Fayez Abdulla 1, ∗and Tamer Al-Assa’d 2
1 Associate Professor of Water Resources, Civil Engineering Department, Jordan University
of Science & Technology, P.O Box 3030, Irbid 22110, Jordan.
2 Water Resources Consultant, Eco-Consult, Amman, Jordan.
∗e-mail: fabdulla@just.edu.jo

Abstract:Jordan is an arid country with very limited water resources.Groundwater is the main source for its water supply.Mujib aquifer is located in the central part of Jordan and is a major source of drinking water for Amman,Madaba and Karak cities.High abstraction rates from Mujib aquifer during the previous years lead to a major decline in water levels and deterioration in groundwater quality. Therefore,proper groundwater management of Mujib aquifer is necessary;and groundwater flow modeling is essential for proper management.For this purpose,Mod flow was used to build a groundwater flow model to simulate the behavior of the flow system under di fferent stresses.The model was calibrated for steady state condition by matching observed and simulated initial head counter lines.Drawdown data for the period 1985 –1995 were used to calibrate the transient model by matching simulated drawdown with the observed one.Then,the transient model was validated by using drawdown data for the period 1996 –2002.The results of the calibrated model showed that the horizontal hydraulic conductivity of the B2/A7 aquifer ranges between 0.001 and 40 m/d. Calibrated speci fic yield ranges from 0.0001 to 0.15.The water balance for the steady state condition of Mujib aquifer indicated that the total annual direct recharge is 20 . × 10 6 m 3 ,the total annual in flow is 13 . × 10 6 m 3 ,springs discharge is 15 . × 10 6 m 3 ,and total annual out flow is 18 . × 10 6 m 3 . Di fferent scenarios were considered to predict aquifer system response under di fferent conditions.  The results of the sensitivity analysis show that the model is highly sensitive to horizontal hydraulic conductivity and anisotropy and with lower level to the recharge rates.Also the model is sensitive to speci fic yield.



Operational mesoscale atmospheric dispersion prediction using a parallel computing cluster
C V Srinivas 1, ∗,R Venkatesan 1 ,N V Muralidharan 1 ,Someshwar Das 2 ,
Hari Dass 3 and P Eswara Kumar 3
1 Radiological Safety Division, SE Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India.
2 National Centre for Medium Range Weather Forecasting, New Delhi 110 003, India.
3 Institute of Mathematical Sciences, Chennai 600 113, India.
∗e-mail: cvsri@igcar.ernet.in

Abstract:An operational atmospheric dispersion prediction system is implemented on a cluster supercomputer for Online Emergency Response at the Kalpakkam nuclear site.This numerical system constitutes a parallel version of a nested grid meso-scale meteorological model MM5 coupled to a random walk particle dispersion model FLEXPART.The system provides 48-hour forecast of the local weather and radioactive plume dispersion due to hypothetical airborne releases in a range of
100 km around the site.The parallel code was implemented on di fferent cluster con figurations like distributed and shared memory systems.A 16-node dual Xeon distributed memory gigabit ethernet cluster has been found su fficient for operational applications.The runtime of a triple nested domain MM5 is about 4 h for a 24 h forecast.The system had been operated continuously for a few months and results were ported on the IMSc home page. Initial and periodic boundary condition data for MM5 are provided by NCMRWF,New Delhi. An alternative source is found to be NCEP,USA.These two sources provide the input data to the operational models at di fferent spatial and temporal resolutions using di fferent assimilation methods.A comparative study on the results of forecast is presented using these two data sources for present operational use.Improvement is noticed in rainfall forecasts that used NCEP data, probably because of its high spatial and temporal resolution.


Global surface temperature in relation to northeast monsoon rainfall over Tamil Nadu
S Balachandran摯瑬敳獩 ,R Asokan and S Sridharan
Regional Meteorological Centre, 50(New 6) College Road, Chennai 600 006, India.
∗e-mail: balaimd@yahoo.co.in
Abstract:The local and teleconnective association between Northeast Monsoon Rainfall (NEMR)over Tamil Nadu and global Surface Temperature Anomalies (STA)is examined using the monthly grid-ded STA data for the period 1901 –2004.Various geographical regions which have signi ficant tele-connective signals associated with NEMR are identi fied.During excess (de ficient)NEMR years,it is observed that the meridional gradient in surface air temperature anomalies between Europe and north Africa,in the month of September is directed from the subtropics (higher latitudes)to higher latitudes (subtropics).It is also observed that North Atlantic Oscillation (NAO)during September in fluences the surface air temperature distribution over north Africa and Europe.Also,the NAO index in January shows signi ficant inverse relationship with NEMR since recent times.The central and eastern equatorial Paci fic oceanic regions have signi ficant and consistent positive correlation with NEMR while the western equatorial region has signi ficant negative correlation with NEMR. A zonal temperature anomaly gradient index (ZTAGI)de fined between eastern equatorial Paci fic and western equatorial Paci fic shows stable signi ficant inverse relationship with NEMR.