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Coastal Vulnerability Assessment for Eastern Coast of India, Andhra Pradesh by Using Geo-Spatial Technique

2016-01-01T00:00:00Z

Title: Coastal Vulnerability Assessment for Eastern Coast of India, Andhra Pradesh by Using Geo-Spatial Technique Authors: Basheer Ahammed KK; Mahendra RS; Pandey AC Abstract: The study mainly deals with the physical vulnerability of eastern coast India, Andhra Pradesh. It is one of the Indian states which have a very vast coastal line. Andhra Pradesh is very important to the whole economy, Vishakhapatnam is a major port situated in the eastern coast of India. Andhra Pradesh coastal line about 972 Km long, is affected by Storm surge, Cyclone, Sea Level Rise and Tsunami, etc. The method adopted for identifying the coastal vulnerability mapping was Coastal Vulnerability Index (CVI). Seven parameters were used for identifying Costal Vulnerability mapping which are Historical Shoreline changes, Mean Sea Level Rice, Significance of Wave Height, Mean Tide Range, Coastal Regional Elevation, Coastal Slope and Geomorphology. The final results of this study are in the form of a coastal vulnerability map which shows the environmentally vulnerable areas. This map will give general idea about the probability of an area to undergo coastal hazards due to coastal erosion or sea level rise. According to this study about 16% area of the coast of Andhra Pradesh is identified to have high vulnerability which can harm the environment. The map prepared of the Andhra coast under this study can be used by the state and district administration involved in the disaster mitigation and management plan.

Comparison of aerosol products retrieved from AERONET, MICROTOPS and MODIS over a tropical urban city, Pune, India

2013-01-01T00:00:00Z

Title: Comparison of aerosol products retrieved from AERONET, MICROTOPS and MODIS over a tropical urban city, Pune, India Authors: More S; Pradeep Kumar P; Gupta P; Devara PCS; Aher GR Abstract: Aerosol Optical Depth (AOD) measurements from Aerosol Robotic NETwork (AERONET; level 2.0), Microtops - II sun-photometer and MODerate Resolution Imaging Spectroradiometer (MODIS) (Terra and Aqua; level 2, collection 5, dark target) were compared and used to characterize aerosols over Pune, India. AODs from Microtops and MODIS were compared with those measured by AERONET to evaluate the measurement quality. To the best of our knowledge, this is the first systematic comparison of MODIS aerosol products over Pune, India. The results of the analysis show that during 2008-10, 68 to 84 of the MODIS AODs fell within an expected error, as defined by the MODIS science team, and thus the retrievals from this system are validated and accepted. In addition, during pre-monsoon periods MODIS retrievals are better-matched with ground-based measurements. On the seasonal scale, MODIS retrievals corroborate well with ground-based measurements, with correlation coefficients ranging from 0.62 to 0.93. Despite an overall satellite-ground agreement, MODIS tends to under-estimate AOD during winter, and this may be due to improper assumptions of surface reflectance and the incorrect selection of aerosol types. AERONET retrieved single scattering albedo (SSA) values in winter (0.82-0.86), suggesting the dominance of absorbing aerosols, slightly increased (0.87-0.89) in pre-monsoon season, indicating more scattering type of aerosols. These values are about 8.9-1.1 lower than those of the assumed SSA values in the MODIS algorithm.

Extended range tropical cyclone predictions for East Coast of India

2014-01-01T00:00:00Z

Title: Extended range tropical cyclone predictions for East Coast of India Authors: Rajasekhar M.; Kishtawal C.M.; Prasad M.Y.S.; Seshagiri Rao V.; Rajasekhar M. Abstract: East Coast of India is vulnerable for tropical cyclone hazards which form over Bay of Bengal (BoB). The average annual frequency of tropical cyclones over the BoB and Arabian Sea (AS) is about five (about 5-6 of the global annual average) and about 80 cyclones form around the globe in a year. The frequency is more in the BoB than in the Arabian Sea, the ratio being 4:1. The monthly frequency of tropical cyclones in the north Indian Ocean display a bi-modal characteristic with a primary peak in November and secondary peak in May. Â© 2014 Capital Publishing Company

Aircraft observations of electrical conductivity in warm clouds

1993-01-01T00:00:00Z

Title: Aircraft observations of electrical conductivity in warm clouds Authors: Raj PE; Devara PCS; Selvam AM; Murty ASR Abstract: Aircraft observations of electrical conductivity and cloud microphsical, dynamical and other electrical parameters were made in warm stratocumulus and cumulus clouds forming during the summer monsoon seasons (June-September) of 1983 and 1985 in the Deccan Plateau region, India. A Gerdien type cylindrical condenser was used for the measurement of electrical conductivity. The variations in the electrical conductivity are observed to be closely associated with the updrafts and downdrafts in the cloud, liquid water content, cloud droplet charge and corona discharge current. The value of electrical conductivity in warm clouds is found to be in the order of 10-12 ohm-1 m-1 which is two orders higher than that observed in clear-air at cloud-base levels in some regions by other investigators. Classical static electricity concepts predict reduced conductivity values inside clouds. Cloud electrical conductivity measurements, particularly in warm clouds are few and the results are contradictory. The recently identified mechanism of vertical mixing in clouds lends support to convective charge separation mechanism with inherent larger than clear-air values for cloud electrical conductivity and therefore consistent with the measurements reported herein.

Thermodynamic structure of the Atmospheric Boundary Layer over the Arabian sea as revealed by MONSOON-77 data

1993-01-01T00:00:00Z

Title: Thermodynamic structure of the Atmospheric Boundary Layer over the Arabian sea as revealed by MONSOON-77 data Authors: Parasnis SS; Morwal SB Abstract: The thermodynamic structure of the Atmospheric Boundary Layer (ABL) over the Arabian sea region has been studied with the help of 135 aerological observations obtained during MONSOON-77 in the region (10-14Â° N, 64-68Â° E) by USSR research vessels. Low-level inversions were observed over the western Arabian sea region (west of 66Â° E) in association with suppressed convection. The different sublayers of the ABL, viz. the mixed layer, the cloud layer and the inversion/isothermal/stable layer were identified. The low-level stability analysis indicated that in the region east of 66Â° E, conditions were favourable for deep convection. The thermodynamic transformation of the boundary layer after precipitation was documented.

Charge separation associated with splashing of water drops on solid surfaces

1993-01-01T00:00:00Z

Title: Charge separation associated with splashing of water drops on solid surfaces Authors: Chate DM; Kamra AK Abstract: Our laboratory experiments show that the charge separation when water drops splash on a brass surface is about an order of magnitude higher than when they splash on surfaces typical of ground surface, such as soil, silica or grass on which raindrops generally splash on the earth's surface. The change being separated has been observe to increase as the drop diameter increases from 3.6 to 7.0 mm. The size distribution of fragment droplets which result from a splash show that the total number of fragments is much larger when the splash occurs on brass surface as compared to that when it occurs on the soil, silica or grass surface. The results indicate that small drops in the range of 5.8 to 7.0 mm diameter are more efficient in changing the kinetic energy of the drop to electrical energy. Results of the experiment have been used to estimate the charge that is generated when raindrops splash on ground. Results of the experiment have been discussed in terms of the hardness of the target surface and the degree of violence of the splash.

Homogeneous Indian Monsoon rainfall: Variability and prediction

1993-01-01T00:00:00Z

Title: Homogeneous Indian Monsoon rainfall: Variability and prediction Authors: Parthasarathy B; Kumar KR; Munot AA Abstract: The Indian summer monsoon rainfall is known to have considerable spatial variability, which imposes some limitations on the all-India mean widely used at present. To prepare a spatially coherent monsoon rainfall series for the largest possible area, fourteen subdivisions covering the northwestern and central parts of India (about 55 of the total area of the country), having similar rainfall characteristics and associations with regional/global circulation parameters are merged and their area-weighted means computed, to form monthly and seasonal Homogeneous Indian Monsoon (HIM) rainfall series for the period 1871-1990. This paper includes a listing of monthly and seasonal rainfall of HIM region. HIM rainfall series has been statistically analysed to understand its characteristics, variability and teleconnections for long-range prediction. HIM rainfall series isfound to be homogeneous, Gaussian distributed and free from persistence. The mean (R) rainfall is 757 mm (87 of annual) and standard deviation (S) 119 mm, with a Coefficient of Variation (CV) of 16. There were 21 dry (K, -andlt;R S) and 19 wet (R i R S) years during 1871-1990. There were clusters of frequent negative departures during 1899-1920 and 1965-1987 and positive departures during 1942-1961. The recent three decades show very high rainfall variability with 10 dry and 6 wet years. The decadal averages were alternatively positive and negative for three consecutive decades, viz., 1871-1900 (positive); 1901-1930 (negative); 1931-1960 (positive) and 1961-1990 (negative) respectively. Significant QBO and autocorrelation at 14th lag have been found in HIM rainfall series. To delineate the changes in the climatic regime of the Indian summer monsoon, sliding correlation coefficients (CCs) between HIM rainfall series and (i) Bombay msl pressure, (ii) Darwin msl pressure and (iii) Northern Hemisphere surface air temperature over the period 1871-1990 have been examined. The 31-year sliding CCs showed the systematic turning points of positive and negative CCs around the years, 1900 and 1940. In the light of other corroborative evidences, these turning points seem to delineate 'meridional' monsoon regime during 1871-1900 and 1940-1990 and 'zonal' monsoon regime during 1901-1940. The monsoon signal is particularly dominant in many regional and global circulation parameters, during 1951-1990. Using the teleconnections of HIM series with 12 regional/global circulation parameters during the recent 36-year period 1951-86 regression models have been developed for long-range prediction. In the regression equations 3 to 4 parameters were entered, explaining upto 80 of the variance, depending upon the data period. The parameters that prominently enter the multiple regression equations are (i) Bombay msl pressure, (ii) April 500 mb Ridge at 75Â°E, (iii) NH temperature, (iv) Nouvelle minus Agalega msl pressure and (v) South American msl pressure. Eleven circulation parameters for the period 1951-80 were subjected to Principal Component Analysis (PCA) and the PC's were used in the regression model to estimate HIM rainfall. The multiple regression with three PCs explain 72 of variance in HIM rainfall.

Relationship between circulation and rainfall over India during the southwest monsoon season. Part II: 700 hPa contour height field and some synoptic indices

1993-01-01T00:00:00Z

Title: Relationship between circulation and rainfall over India during the southwest monsoon season. Part II: 700 hPa contour height field and some synoptic indices Authors: Inamdar SR; Singh SV Abstract: Concurrent and lag relationships of 700 hPa contour heights over the Indian region and some large scale synoptic indices with rainfall distribution over various parts of India have been studied on a 1-day to 7-day basis by using 10 years (1966-1975) of data. Important dynamic influences causing rainfall over various parts of the country have been identified by the preparation of concurrent and lag-correlation charts. Multiple regression equations have also been developed for prediction of daily, 3-day and 5-day rainfall by using the synoptic indices. Positive skills with higher values over central India and the west coast have been obtained.

Variation in the relationship of the Indian summer monsoon with global factors

1993-01-01T00:00:00Z

Title: Variation in the relationship of the Indian summer monsoon with global factors Authors: Mooley DA; Munot AA Abstract: Utilizing data for the long period 1871-1990, variation in the relationships between Indian monsoon rainfall (IMR) and tendencies of the global factors. Southern Oscillation Index (SOI) and the sea surface temperature (SST) over eastern equatorial Pacific Ocean has been explored. The periods for which relationships exist have been identified. Tendencies from the season SON (Sept-Oct-Nov) to season DJF (Dec-Jan-Feb) and from DJF to MAM (Mar-Apr-May) before the Indian summer monsoon are indicated respectively by SOIT-2/SSTT-2 and SOIT-l/SSTT-1, current tendency from JJA (June-July-Aug) to SON, by SOIT0/SSTT0, tendencies from SON to DJF and DJF to MAM following monsoon, by SOIT1/SSTT1 and SOIT2/SSTT2 respectively. It is observed that while the relationships of IMR with SSTT-1, SSTT0 and SSTT2 exist almost throughout the whole period, that with SOIT-1 exists for 1942-1990, with SOIT0 for 1871-1921 and 1957-1990 and with SOIT2, for 1871-1921 only. The relationships that exist with SOIT-1, SOIT2, SSTT-1, SSTT2 and with SSTT0 (for period 1931-1990) are found to be very good and those that exist with SOIT0 for periods 1871-1921 and 1957-90 and for SSTT0 for the period 1871-1930 are good. It is thus seen that the relationships of SOIT-1, SOIT0 and SOIT2 with IMR do not correspond well with those of SSTT-1, SSTT0 and SSTT2 with IMR respectively, even though SOI and SST are closely related to each other for all the seasons. SOIT-1 and SSTT-1 can continue to be used as predictors for IMRDuring the whole period, IMR is found to play a passive, i.e. of being influenced or anticipated by SSTT-1 as well as an active role, i.e. of influencing or anticipating SSTT2. This implies a complex and perhaps non-linear interaction between IMR and SST tendency from DJF to MAM. Possibly, this is a part of the larger interaction between Asian monsoon rainfall and the tropical Pacific. A possible physical mechanism for the interaction is indicated.

Ozone in the tropics

1993-01-01T00:00:00Z

Title: Ozone in the tropics Authors: Mani A

Global structure of the Madden-Julian Oscillations during two recent contrasting summer monsoon seasons over India

1993-01-01T00:00:00Z

Title: Global structure of the Madden-Julian Oscillations during two recent contrasting summer monsoon seasons over India Authors: Vernekar AD; Thapliyal V; Kripalani RH; Singh SV; Kirtman B Abstract: The global nature of the Madden-Julian Oscillations (MJOs) have been investigated by applying a frequency filter to daily data for the summer monsoon months (June to September) during two contrasting years-1987, a deficient monsoon year and 1988, an excess monsoon year. Several meteorological parameters at five levels in the troposphere have been examined. Regions with large amplitude of these oscillations are isolated for each year. The results indicate that the global spatial distribution of these oscillations is more in a deficient year than in an excess year, in particular over the Indian subcontinent and the EI NiÃ±o Southern Oscillation (ENSO) regions. The principal modes of variability during these two years have been investigated through Empirical Orthogonal Functions (EOFs). The first two eigenmodes of 850 hPa zonal wind explain nearly 50 of the variance. The dipole type of structure between the Indian and the Pacific region is more apparent in 1987 than in 1988. Time-longitude cross sections of the filtered zonal wind over the equatorial regions clearly show that eastward propagation is detected in 1987, but is virtually absent in 1988. It is also seen that the 30-60 day filtered winds are stronger during the monsoon of 1987 than in 1988.

Quantitative precipitation forecasting over Narmada Catchment

1993-01-01T00:00:00Z

Title: Quantitative precipitation forecasting over Narmada Catchment Authors: Kumar KK; Soman MK Abstract: Quantitative precipitation forecasting (QPF) has been attempted over the Narmada Catchment following a statistical approach. The catchment has been divided into five sub-regions for the development of QPF models with a maximum lead-time of 24 hours. For this purpose the data of daily rainfall from 56 raingauge stations, twice daily observations on different surface meteorological parameters from 28 meteorological observatories and upper air data from 11 aerological stations for the nine monsoon seasons of 1972-1980 have been utilized. The horizontal divergence, relative vorticity, vertical velocity and moisture divergence are computed using the kinematic method at different pressure levels and used as independent variables along with the rainfall and surface meteorological parameters. Multiple linear regression equations have been developed using the stepwise procedure separately with actual and square root and log-transformed rainfall using 8-year data (1972-1979). When these equations were verified with an independent data for the monsoon season of 1980, it was found that the transformed rainfall equations fared much better compared to the actual rainfall equations. The performance of the forecasts of QPF model compared to the climatological and persistence forecasts has been assessed by computing the verification scores using the forecasts for the monsoon season of 1980.

Thermodynamic structure of the boundary layer in relation to a monsoon depression over the Bay of Bengal - A case study

1993-01-01T00:00:00Z

Title: Thermodynamic structure of the boundary layer in relation to a monsoon depression over the Bay of Bengal - A case study Authors: Seetaramayya P; Parasnis SS; Nagar SG; Vernekar KG Abstract: Aerological observations carried out on board ORV Sagarkanya at a stationary location (20Â° N, 89Â° E) over the Head Bay of Bengal during August 18-21, 1990 were analysed to study the thermodynamic structure of the marine boundary layer in relation to a monsoon depression which formed in situ with its centre at 20Â° N, 88Â° E. The q(mixing ratio) reversal observed at 850 hPa prior to formation of the low pressure area shifted to a higher level (h<700 hPa) with the formtion of the low. Positive buoyancy below 850 hPa prior to the formation of the low indicated conditions favourable for deep convection. When the low pressure area intensified into a depression, negative buoyancy was observed at lower levels.

Global spectra of energy and enstrophy and their fluxes during July 1979

1993-01-01T00:00:00Z

Title: Global spectra of energy and enstrophy and their fluxes during July 1979 Authors: Desai SS; Mishra SK Abstract: Transient and stationary spectra of kinetic energy (KE), available potential energy (APE) and enstrophy (EN), and their spectral fluxes as a function of the two-dimensional wavenumbern were computed for July 1979. Triangular truncation at zonal wavenumber 42 was used for computation. The slopes of various spectra in the wavenumber range 14?n?25 were obtained by fitting a straight line in log-log scale by the least square method. The transientKE, APE andEN spectra in the lower (upper) troposphere had slopes ?221 (?230), ?265 (?264) and ?036 (?046), respectively. The effect of stationary and divergent motion on the slope values was investigated. The possible correlation between the slope and percentage of transient component in the combined energy and enstrophy was examined to identify the transient motion of the atmosphere with the two-dimensional homogeneous isotropic turbulence. The vertically averaged slope of kinetic energy and enstrophy in the lower (upper) troposphere was close to the value at 700 (200) hPa level

A model study of the growth of summer monsoon disturbances

1993-01-01T00:00:00Z

Title: A model study of the growth of summer monsoon disturbances Authors: Kasture SV; Keshavamurty RN; Satyan V Abstract: Using an appropriate north-south distribution of a diabatic heating in a global multilevel spectral model, we have generated summer monsoon type of basic flow. Then we superimposed a pulse at the point of inflexion to the north of the jet at 900 mb. Using conditional instability of the second kind (CISK) type of cumulus heating we integrated the model keeping the basic flow fixed. We found that the pulse grows into observed type of monsoon depression. When cumulus heating was absent the pulse did not show any appreciable growth. The detailed computations of energetics show that the main growth mechanism of the pulse is by baroclinic energy exchange in the presence of cumulus heating.

Is the trend in chlorophyll-a in the Arabian Sea decreasing?

2012-01-01T00:00:00Z

Title: Is the trend in chlorophyll-a in the Arabian Sea decreasing? Authors: Prakash P; Prakash S; Rahaman H; Ravichandran M; Nayak S Abstract: Recent studies of satellite-derived Chlorophyll concentrations (Chl-a) in the western Arabian Sea (AS) have suggested an increasing temporal trend, but the length of the records used have typically been too short to resolve longer-term trends, if any. Our analysis of a long term satellite ocean color data shows a change of trend in the summer chlorophyll for the western AS before and after 2003; Chl-a concentration was indeed increasing till 2003, but appears to be declining since then, indicating a secular multi-year trend in Chl-a variability. However, this trend is not uniform over the entire region. Analysis of wind, sea surface temperature (SST), Sea Level Anomaly (SLA) and thermocline depth, suggests that the declining summer monsoon chlorophyll-a (Chl-a) concentration may be due to increasing SLA in this region. The earlier observed biological changes in the western AS could be an artifact of the change in local winds and ocean dynamics, which may be a part of the natural long-term variability. Â© 2012. American Geophysical Union.

On the stable stratification of the nocturnal lower troposphere inferred from lidar observations over Pune, India

1993-01-01T00:00:00Z

Title: On the stable stratification of the nocturnal lower troposphere inferred from lidar observations over Pune, India Authors: Raj PE; Devara PCS Abstract: The nocturnal structure of the lower troposphere is studied using aerosol profile data (502800 m AGL) obtained with a bistatic, continuous wave, Argon ion lidar system during October 1986September 1989 at Pune (1832? N, 7351? E, 559m AMSL), India. The top of the nocturnal groundbased inversion is taken as the height above ground where the negative vertical gradient in aerosol concentration first reaches a maximum. During the post-sunset period over this station, this height is as low as 160m and frequently lies around 550m. Greater heights are observed in pre-monsoon months and smaller ones during the southwest monsoon season. Positive vertical gradients in aerosol concentration, indicative of stable/elevated layers, appear frequently around 750m. Temporal variations of aerosol concentration gradients in two adjacent air layers, 9201000m and 1001100m, provide evidence that stability increases downward in the early night hours

Envelope Depth-Area-Duration raindepths for different homogeneous rainstorm zones of the Indian region

1993-01-01T00:00:00Z

Title: Envelope Depth-Area-Duration raindepths for different homogeneous rainstorm zones of the Indian region Authors: Dhar ON; Nandargi S Abstract: About one hundred severe rainstorms occurred in the Indian region during the period between 1880 and 1990. The centres of these severe rainstorms occur mostly in four preferred zones. The two major zones where the bulk of rainstorm centres are located are in north and central India. These two zones have been further sub-divided into four homogeneous subzones for the purpose of rainstorm transposition. For each of these homogeneous sub-zones and zones envelope Depth-Area-Duration (DAD) raindepths have been calculated. These are based on the DAD data of severe rainstorms that have occurred within each zone in order to obtain probable maximum precipitation (PMP) estimates.

Log-normal distribution of the heights of convective clouds around Delhi, north India

1993-01-01T00:00:00Z

Title: Log-normal distribution of the heights of convective clouds around Delhi, north India Authors: Chatterjee RN; Prakash P; Ali K Abstract: Frequency distributions have been examined to investigate whether the growth of such clouds takes place according to a random process that obeys the law of proportionate effects as proposed by Lopez (1977). Echo heights have been found to be distributed log-normally in all seasons except in the largest few per cent of the height categories where the distributions deviated below the log-normal line. The observed distributions confirm that the convective clouds grow according to the above law in this region also. The observed deviation of the distributions below the log-normal line at greater heights indicates the presence of fewer clouds of such heights than a log- normal distribution predicts. This is attributed to the effect of tropopause which limits the vertical development of convective clouds. -from Authors

Tropical stratospheric circulation and monsoon rainfall

1993-01-01T00:00:00Z

Title: Tropical stratospheric circulation and monsoon rainfall Authors: Sikder AB; Patwardhan SK; Bhalme HN Abstract: Interannual variability of both SW monsoon (June-September) and NE monsoon (October-December) rainfall over subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu have been examined in relation to monthly zonal wind anomaly for 10 hPa, 30 hPa and 50 hPa at Balboa (9Â°N, 80Â°W) for the 29 year period (1958-1986). Correlations of zonal wind anomalies to SW monsoon rainfall (r=0.57, significant at 1 level) is highest with the longer lead time (August of the previous year) at 10 hPa level suggesting some predictive value for Coastal Andhra Pradesh. The probabilities estimated from the contingency table reveal non-occurrence of flood during easterly wind anomalies and near non-occurrence of drought during westerly anomalies for August of the previous year at 10 hPa which provides information for forecasting of performance of SW monsoon over Coastal Andhra Pradesh. However, NE monsoon has a weak relationship with zonal wind anomalies of 10 hPa, 30 hPa and 50 hPa for Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu. Tracks of the SW monsoon storms and depressions in association with the stratospheric wind were also examined to couple with the fluctuations in SW monsoon rainfall. It is noted that easterly / westerly wind at 10 hPa, in some manner, suppresses / enhances monsoon storms and depressions activity affecting their tracks.

Optimization of the raingauges for a representative all-India and subdivisional rainfall series

1993-01-01T00:00:00Z

Title: Optimization of the raingauges for a representative all-India and subdivisional rainfall series Authors: Sontakke NA; Singh N; Pant GB Abstract: An objective approach similar to the forward selection of independent variables in the multiple linear regression has been attempted to optimize the network of raingauges for the summer monsoon rainfall (June-September total) series (1871-1984) of India as well as its 29 selected meteorological subdivisions prepared involving the data of 306 raingauges. For the all-India monsoon rainfall series twenty seven gauges entered the selection whose mean showed the correlation coefficient (CC) of 0.9869. Keeping in view the difficulties of getting data from all the 306 gauges, 35 India Meteorological Department (IMD) gauges with mean showing CC of 0.9898 have been identified for updating this series. The constructed all-India monsoon rainfall series for the period 1871-1992 using 35 selected observations is presented. It was interesting to note that the set of 35 gauges selected for the monsoon total has shown equally promising results for the all-India monsoon monthly (June-September) as well as the annual rainfall series. For the 29 subdivisional monsoon rainfall series, however, in total 188 IMD-gauges (62 of the total of 306 gauges) entered the selection. For 17 subdivisions the CC exceeded 0.98, for 3 subdivisions it varied between 0.97 and 0.98, for 5 subdivisions between 0.96 and 0.97 and for the remaining 4 subdivisions between 0.90 and 0.94. They showed equally encouraging results for the monsoon monthly and annual rainfall series for the different subdivisions. Limitations and implications of the optimization technique are also briefly discussed.

An observational study on the energetics of the onset monsoon vortex, 1979

1993-01-01T00:00:00Z

Title: An observational study on the energetics of the onset monsoon vortex, 1979 Authors: George L; Mishra SK Abstract: Strengthening of the meridional and vertical shear of the mean zonal wind is noticed during the period. The vortex is formed to the north of the westerly jet, in the zone of maximum cyclonic shear. The northward shift of the large-scale monsoon current is noticed in association with northward movement of the onset vortex. It is identified from the mean energetics that both barotropic and baroclinic energy conversions, and also the boundary terms, maintain the vortex. Baroclinic energy transfer to eddy kinetic energy (KE) takes place not only in the upper levels but also in the lower levels. Further, the energy conversion from zonal kinetic energy (KZ) to KE dominates over the energy conversion from eddy available potential energy (AE) to KE. The generation rate of the zonal and eddy available potential energy and the frictional dissipation of KE are computed by the residue method; the values are 0.54 W m-2, 0.25 W m-2 and 0.65 W m-2, respectively.

Space-time evolution of meteorological features associated with the onset of Indian summer monsoon

1993-01-01T00:00:00Z

Title: Space-time evolution of meteorological features associated with the onset of Indian summer monsoon Authors: Soman MK; Kumar KK Abstract: Over the peninsular Indian stations, the rainfall composites show sudden and sharp increases with onset except in the case of east coast stations, where rainfall does not substantially change with the onset of the summer monsoon. The composite wind analysis demonstrates how the upper-tropospheric subtropical westerlies weaken and shift poleward and the tropical easterlies strengthen and spread north with the onset of the monsoon. The onset vortex that takes the monsoon northward along the west coast in many years is clearly discernible between 600 and 400 hPa in the composite streamline charts. The relative humidity builds up suddenly in the vertical a few days before the onset at the respective stations. The composite outgoing longwave radiation fields over the north Indian Ocean show rapid buildup of convective activity over the southeast Arabian Sea and east Bay of Bengal with the approach of the monsoon.

Lidar measurements of aerosols in the tropical atmosphere

1993-01-01T00:00:00Z

Title: Lidar measurements of aerosols in the tropical atmosphere Authors: Devara PCS; Raj PE Abstract: Measurements of atmospheric aerosols and trace gases using the laser radar (lidar) techniques, have been in progress since 1985 at the Indian Institute of Tropical Meteorology, Pune (1832?N, 7351?E, 559 m AMSL), India. These observations carried out during nighttime in the lower atmosphere (up to 5.5 km AGL), employing an Argon ion / Helium-Neon lidar provided information on the nature, size, concentration and other characteristics of the constituents present in the tropical atmosphere. The time-height variations in aerosol concentration and associated layer structure exhibit marked differences between the post-sunset and pre-sunrise periods besides their seasonal variation with maximum concentration during pre-monsoon / winter and minimum concentration during monsoon months. These observations also revealed the influence of the terrain of the experimental site and some selected meteorological parameters on the aerosol vertical distributions. The special observations of aerosol vertical profiles obtained in the nighttime atmospheric boundary layer during October 1986 through September 1989 showed that the most probable occurrence of mixing depth lies between 450 and 550 m, and the multiple stably stratified aerosol layers present above the mixing depth with maximum frequency of occurrence at around 750 m. This information on nighttime mixing depth / stable layer derived from lidar aerosol observations showed good agreement with the height of the ground-based shear layer / elevated layer observed by the simultaneously operated sodar at the lidar site

Characteristics of the atmospheric boundary layer over a tropical station as evidenced by tethered balloon observations

1993-01-01T00:00:00Z

Title: Characteristics of the atmospheric boundary layer over a tropical station as evidenced by tethered balloon observations Authors: Vernekar KG; Mohan B; Saxena S; Patil MN Abstract: A tethersonde observational program was conducted for eight days during February and March 1989 at Pune, India, during daytime for the study of mixed-layer evolution. A surface-based nocturnal inversion of intensity 8-10 K (100 m)-1 was observed on most of the days. It takes about 2 h after sunrise for this inversion to start eroding and 4-5 h for complete erosion. Profiles of potential temperature, mixing ratio, and wind are discussed. Using Tenekes and Driedonks' convective boundary-layer model an average sensible heat flux of 129 W ,-2 is estimated during morning hours, which is comparable to the flux value obtained by an earlier study using an eddy correlation technique at a nearby site during March and April.

Estimation of seismic hazard in Gujarat region, India

2013-01-01T00:00:00Z

Title: Estimation of seismic hazard in Gujarat region, India Authors: Chopra S; Kumar D; Rastogi BK; Choudhury P; Yadav RBS Abstract: The seismic hazard in the Gujarat region has been evaluated. The scenario hazard maps showing the spatial distribution of various parameters like peak ground acceleration, characteristics site frequency and spectral acceleration for different periods have been presented. These parameters have been extracted from the simulated earthquake strong ground motions. The expected damage to buildings from future large earthquakes in Gujarat region has been estimated. It has been observed that the seismic hazard of Kachchh region is more in comparison with Saurashtra and mainland. All the cities of Kachchh can expect peak acceleration in excess of 500 cm/s2 at surface in case of future large earthquakes from major faults in Kachchh region. The cities of Saurashtra can expect accelerations of less than 200 cm/s2 at surface. The mainland Gujarat is having the lowest seismic hazard as compared with other two regions of Gujarat. The expected accelerations are less than 50 cm/s2 at most of the places. The single- and double-story buildings in Kachchh region are at highest risk as they can expect large accelerations corresponding to natural periods of such small structures. Such structures are relatively safe in mainland region. The buildings of 3-4 stories and tall structures that exist mostly in cities of Saurashtra and mainland can expect accelerations in excess of 100 cm/s2 during a large earthquake in Kachchh region. It has been found that a total of 0.11 million buildings in Rajkot taluka of Saurashtra are vulnerable to total damage. In Kachchh region, 0.37 million buildings are vulnerable. Most vulnerable talukas are Bhuj, Anjar, Rapar, Bhachau, and Mandvi in Kachchh district and Rajkot, Junagadh, Jamnagar, Surendernagar and Porbandar in Saurashtra. In mainland region, buildings in Bharuch taluka are more vulnerable due to proximity to active Narmada-Son geo-fracture. The scenario hazard maps presented in this study for moderate as well as large earthquakes in the region may be used to augment the information available in the probabilistic seismic hazard maps of the region.

Universal quantification for deterministic chaos in dynamical systems

1993-01-01T00:00:00Z

Title: Universal quantification for deterministic chaos in dynamical systems Authors: Selvan AMary Abstract: A cell dynamic system model for deterministic chaos enables precise quantification of the round-off error growth, i.e., deterministic chaos in digital computer realizations of mathematical models of continuum dynamical systems. The model predicts the following: a) The phase space trajectory (strange attractor) when resolved as a function of the computer accuracy has intrinsic logarithmic spiral curvature with the quasiperiodic Penrose tiling pattern for the internal structure. b) The universal constant for deterministic chaos is identified as the steady-state fractional round-off-error k for each computational step.

On the spatio-temporal variations of the tropopause height over india and indian summer monsoon activity

1993-01-01T00:00:00Z

Title: On the spatio-temporal variations of the tropopause height over india and indian summer monsoon activity Authors: Kulkarni JR; Verma RK Abstract: The spatio-temporal variation of the tropopause height (TH) over the Indian region (5Â°N-35Â°N, 70Â°E-95Â°E) has been studied using monthly mean TH data, for 22-year period, 1965 to 1986. The study revealed that the stations south of 20Â°N showed maximum TH in April/May and minimum in September. This variation in TH has been attributed to the corresponding variation of average sea surface temperature (SST) over Â±20Â° latitudinal belt over Indian Ocean, Arabian Sea and Bay of Bengal. Further the stations north of 20Â°N showed maximum in June and minimum in October/November. This maximum in TH has primarily been attributed to the increased insolation and convection. Furthermore it is noticed that the anomaly of TH moved northwards during the period April to July. The interannual variability of the Indian Summer Monsoon Activity (ISMA) has been studied in relation to all India mean TH (at 12 GMT) for six months April through September. The composites of mean TH for good and bad monsoon years showed that all India mean TH is statistically higher in good monsoon years than in bad monsoon years. The relationship between ISMA and all India mean May TH has been studied using the contingency table. The study suggested that the forecast of ISMA could be prepared using mean May TH.

02.O.02 Investigations of aerosol optical depth variations using spectroradiometer at an urban station, Pune, India

1994-01-01T00:00:00Z

Title: 02.O.02 Investigations of aerosol optical depth variations using spectroradiometer at an urban station, Pune, India Authors: Devara PCS; Pandithurai G; Raj PE; Sharma S Abstract: Multi-spectral measurements using solar radiometers to derive atmospheric optical depth, aerosol size distribution and total column content of gas constituents have been reported by many authorslT4. A High Spectral Resolution Radiometer (HSRR) has been developed at the Indian Institute of Tropical Meteorology, Pune (18'32', 73'51'E, 559 m AMSL), India for continuous scanning of solar spectrum in any specified wavelength region at a faster rate so that information content will give a better estimation of atmospheric aerosols and trace gas constituents.

Dendroclimatic reconstruction of summer precipitation at Srinagar, Kashmir, India, since the late-eighteenth century

1994-01-01T00:00:00Z

Title: Dendroclimatic reconstruction of summer precipitation at Srinagar, Kashmir, India, since the late-eighteenth century Authors: Borgaonkar HP; Pant GB; Rupa Kumar K

Study of laser scintillation in different atmospheric conditions

1993-01-01T00:00:00Z

Title: Study of laser scintillation in different atmospheric conditions Authors: Raj PE; Sharma S; Devara PCS; Pandithurai G Abstract: Laser scintillation observations were carried out over a flat surface in different atmospheric conditions on 33 separate days during March 1990-April 1991 and were analyzed and studied. The principal results of the analysis reveal: 1) marked seasonal variations in optical turbulence (through the measurement of refractive-index structure function Cn 2) and scintillation intensity (measured in terms of percent modulation Pm), 2) close correspondence among the variations in Cn 2, Pm, and atmospheric temperature; 3) lower values of Cn 2 during cloud sky as compared to clear sky conditions; and 4) agreement between the observations and theory in respect of the pathlength dependence of Cn 2 and Pm. The results are discussed with reference to the possible meteorological origin of turbulence, and the importance of the study for making measurements of optical turbulence remotely over inaccessible regions is highlighted.

Evaluation of forecast performance of an economical explicit time integration scheme in a limited area model over Indian region

1994-01-01T00:00:00Z

Title: Evaluation of forecast performance of an economical explicit time integration scheme in a limited area model over Indian region Authors: Bandyopadhyay A; Singh SS Abstract: An economical explicit scheme of time integration is implemented in a regional model over Indian region to achieve computational economy. The model is also integrated by explicit Leap-Frog Scheme. The performance of economical explicit scheme is evaluated by comparing the forecast results with those produced by leap-frog scheme. The results show that the economical explicit scheme produces more or less similar forecasts as compared to those produced with leap-frog scheme. However, application of the economical explicit scheme saves substantial amount of computer time. The scheme is found nearly four times economical as compared to explicit leap-frog scheme.

Remote sensing of atmospheric aerosol in the nocturnal boundary layer using lidar

1994-01-01T00:00:00Z

Title: Remote sensing of atmospheric aerosol in the nocturnal boundary layer using lidar Authors: Devara PCS; Ernest Raj P; Sharma S Abstract: This paper presents the results of the lidar experiments that have been performed during January 1989 through August 1990 to study the aerosol vertical distributions in the nocturnal atmosphere and their comparison with near-simultaneous aerological soundings for environmental monitoring. During the study period, the aerosol distributions showed significant stratified aerosol layer structures in the lower atmosphere throughout the south-west monsoon season (June-September), while these structures appear to be either erratic or absent during remaining months of the year. In addition, the aerosols present in the lowest air layers up to 200 m are found to contribute significantly (about 40) to the aerosol loading in the nocturnal boundary layer at the lidar site. The pre-monsoon to winter ratio of mixing depth and ventilation coefficient were found to be 1Â·11 and 1Â·62, respectively. Thus the height of the mixed layer (around 350 m) and the associated ventilation coefficients suggest that early winter evenings tend to have higher pollution potential at the experimental site. The results indicate that the lidar technique has the potential to yield good information on the structure of the nocturnal atmosphere which is found to be influenced by the atmospheric stability conditions as revealed by aerological observations.

Lidar-observed long-term variations in urban aerosol characteristics and their connection with meteorological parameters

1994-01-01T00:00:00Z

Title: Lidar-observed long-term variations in urban aerosol characteristics and their connection with meteorological parameters Authors: Devara PCS; Raj PE; Sharma S; Pandithurai G Abstract: More than 200, weekly spaced, lidar-derived vertical profiles of aerosol concentration in the lower atmosphere (up to 1380 m above ground level) obtained during night-time between October 1986 and August 1990 at the Indian Institute of Tropical Meteorology (IITM), Pune (1832'N, 7351'E, 559 m above mean sea-level), India, have been used to study the long-term variations in aerosol concentration in different air layers. Selected meteorological parameters for the above period at Pune have also been examined to investigate their association with the aerosol concentration. The spectral analysis of the data revealed significant periodicities in four different characteristic ranges, namely 2.513.5, ca. 27, ca. 33 and 4048 weeks in both lidar-derived aerosol content and meteorological parameters; the fourth range being more predominant in all the parameters. These results, together with those of cross-correlation analysis of the data, indicate an association between the long-term trends present in both aerosol and meteorological parameters at the station

Variation in the ionic composition in convective showers in Pune, India

1994-01-01T00:00:00Z

Title: Variation in the ionic composition in convective showers in Pune, India Authors: Naik MS; Khemani LT; Momin GA; Rao PSP; Pillai AG; Safai PD Abstract: Rain water samples of equal volume (100 ml) were collected sequentially from 5 convective shower events for a period of 2 years during the summer monsoon seasons of 1988 and 1989 at Pune. A marked decrease in the concentrations of soil-oriented elements Na , K , Ca2 and Mg2 was observed in the first few samples in all the events followed by a decrease in pH of the subsequent samples. Surprisingly, SO42- also showed similar variation, indicating that soil is contributing some SO42- in rain water. Washout process appears to be an important mechanism for the removal of the major ions from the atmosphere. However, rainout processes seem to be important for the removal of NO3- ions. The study points out that sequential sampling during a single shower appears to give better information about the relationship among H , Na , K , Ca2 , Mg2 , SO42- and NO3- as compared to bulk sampling for longer duration.