Annual Report 2005-2006

Scientific Research

Deep Continental Studies

Ongoing activities

• Structure and Evolution of South Indian craton & mobile belts from deep seismic profiling and other geophysical and geological studies (Active and Passive seismics)

In the first phase deep seismic reflection data along Kalugumalai-Kanyakumari (142 km) part of the transect has been acquired. In the second phase six major shot points located at pickets 77 (south of Vattalkundu), 418 (P. Kovilpatti), 808 (Kalainkuruchi), 1271 (R.Puram), 1953 (Panakudi) and 2269 (Kanniyakumari) have been activated to acquire seismic refraction and wide angle reflection data. Data processing is in progress. All the seismic reflection data acquired along Vattalkundu- Kalugumalai part of the profile has been processed and a reasonably good seismic stack section was obtained.

• Deep Seismic Reflection Studies Along the NW Himalayan Geotransect

Deep crustal reflection study has been carried out along 35 km long Barsar-Bhota-Hamirpur and 65 km long Bhota-Ner Chowk-Chail Chowk profiles across the foothills of NW Himalaya under the NW Himalayan geotransect program (Himprobe)of DST using RF telemetry system. The profiles run across the MBT, the Jwalamuhki thrust and other thrust faults in this part of the Himalaya.

In the present work, multifold near vertical reflection data set employing 150 live seismic channels with a source (explosives) spacing of 400 / 200 meters has been obtained. A shot interval of 400/ 200m and geophone group interval of 100m is used for achieving a multiplicity of 15. Reasonably wide band (4.5-200 Hz) seismic signals were recorded with the present configuration using 4.5 Hz low distortion digital grade SM-6 geophone strings. The shallow section indicates thick sequence of Siwalik (younger) sediments up-to 6 s TWT. Many prominent dipping reflection bands have been observed from 3 seconds to 15 seconds TWT even when foldage is low. These dipping events are be related to collision tectonics of the Himalayan orogeny. The seismic image has delineated that the Moho lies at deeper in the eastern of the profile near Ner Chowk. A sub-horizontal reflection band from 12-13.5 S TWT depicts the typical reflection Moho signature in the region. Scattered sub-moho reflections could also be noticed on the reflection sections.

• Geological, Geochemical and Palaeomagnetic studies of West Garo Hills dykes, Meghalaya

The Meghalaya Plateau, a horst like feature covering an area of 40000km2 consists of Garo, Khasi and Jaintia Hills extending through Mikir hills northeast wards beneath the alluvium of Upper Assam. It is an uplifted block bounded by Brahmaputra graben and Oldham fault in the north and Dauki fault in the south and represents a detached portion of Indian Shield. A total of 49 oriented block samples collected from gabbro, dolerite dykes, and pyroxenites around Shillong were cored, cut and measured for their Natural Remanent Magnetic (NRM) properties and susceptibilities. NRM directions of the dolerites and pyroxenites show very good grouping whereas the gabbro dykes show that West Garo Hills dykes and others dolerites are similar to Rajmahal Traps and Sylhet Traps and geology of the region confirms that the dyke activity is contemporaneous with that of Rajmahal and Sylhet volcanism.

• Deep crustal structure of NW Himalaya through gravity and magnetic data analysis

Gravity and total-field magnetic intensity measurements are carried out along the profile, Keylong - Jispa - Patsio - Sarchu- Barlacha la - Pang - Tanglang la - Rumtse. Approximately, 180 gravity and 180 total-field magnetic intensity measurements are carried out. The relevant data processing is in progress.

• Deformation fabrics in granitoids of Chhota Udepur-Alirajpur region from Anisotropy of Magnetic Susceptibility (AMS) studies
• AMS analysis of samples of the Godhra Granite and adjacent gneiss collected across a shear zone reveal that the degree of magnetic anisotropy (P') is highest in samples close to the shear zone. Therefore, it is inferred that the emplacement of Godhra Granite was synchronous with the deformation of the gneiss.
• It has been noted that the degree of magnetic anisotropy (P'), magnitude of magnetic lineation (L) and intensity of shape preferred orientation (SPO) increases towards the southern parts of the Godhra Granite. This southern part has proximity to the Central Indian Tectonic Zone (CITZ). Therefore, it is inferred that emplacement of Godhra Granite is synchronous with the tectonic rejuvenation of the CITZ.

Anisotropic magnetic Susceptibility facility was set up at Department of Geology & Geophysics, IIT, Kharagpur in 2003. The facility has been upgraded with Digital Image Analyses Facility. This includes a Leica DMLP Research Microscope fitted with Leica DFC 320 Digital Camera that is attached to a computer. Leica Qwin Software is used for Digital Image Analyses (Figure 2.9). This setup enables real time image capture and analyses from microstructures observed in thin sections. The image on the computer monitor documents conversion of the captured image to a binary image for further analyses.

Figure 2.9: National Facility on Anisotropic Magnetic
Susceptibility with Image Analyzer setup at IIT, Kharagpur

• Studies on the Granitic rocks of the Naga Hills Ophiolite Belt

The geological field relationships of the Luthur plagiogranite body of the Naga Hills Opiolite belt were studied and laboratory investigations indicate the granite to be a medium to coarse grained granite with variable mafic to felsic mineral abundances across the outcrop. It is relatively mafic rich compared to several plagiogranite occurrences in the ophiolite sequences.

New Initiatives

• Three new corridors in NE Himalaya have been chosen for multidisciplinary studies under DCS programme. These corridors are located NW-SE in Kameng, Subansiri and Siyang windows. About 20 projects are being funded.
• National facility on Stable Isotope Geochemistry has been established at Department of Geology and Geophysics, Indian Institute of Technology Kharagpur. The equipment has been installed, tested and operational.
• The National Facility on Geochronology and Isotope Geology was set up and commissioned in 2003 at IIT Roorkee to undertake Mass Spectrometry-related research programmes for geochronology on critical sectors of the Indian Lithosphere.

Summary of some of the results achieved is given below:

Palghat-Cauvery Shear Zone:

New 2.9 Ga Granulite facies metamorphism of Kollaimalai and Pachchaimalai Hills in the Palghat-Cauveri Shear Zone (PCSZ).

• Shyok/Indus Suture Zones:

6 samples from Nubra Volcanics yielded ⁸⁷Sr/⁸⁶Sr ratios range from 0.70422 to 0.70492, while 2 samples for the ^143/144 Nd ratio gave 0.512840 to 0.512852.

• ⁸⁷Sr/⁸⁶Sr isotope ratios from Trans-Himalayan Rivers

⁸⁷Sr/⁸⁶Sr isotope ratio varies from 0.70859 to 0.71374 in Nubra River and its tributaries in comparison to 0.70619 to 0.71205 ratios in the Shyok River vary. In the Indus River, the radiogenic Sr is comparatively less (0.71049 to 0.71159) to that of its tributary (0.73491) that drains through ITSZ rocks.

• Rb-Sr whole rock and mineral ages from the Ladakh Batholith

21 whole rock samples yield ⁸⁷Sr/⁸⁶Sr ratios varying from 0.704000 to 0.763413, while ⁸⁷Sr/⁸⁶Sr ratios range from 0.20460 to 28.21580. A perfect 4-point isochron on samples from the Kharu- Chang La section. gives its crystallization age of 61.59±0.05 Ma with initial ⁸⁷Sr/⁸⁶Sr ratio of 0.70417±0.000006. 7 biotite fractions are 36.71±0.05 to 52.48±0.05 Ma in age.

• Himalayan Pan-African granitoids

(i) Landsdown Granite: On the basis of 6-point isochron Rb-Sr age is 172±93 Ma age with high initial ratio of 0.825±0.032 (MSWD = 1661).

(ii) Bhaironghati Granite: Seven-point whole-rock isochron yields an age of 517±26 Ma with Rb-Sr muscovite ages from 2 samples of 380.00±0.40 and 357.24±0.38 Ma and give us the pre- Himalayan ages. Biotite cooling ages gives us the Himalayan metamorphism cooling age and range narrowly between 15.5 and 18 Ma.

(iii) Akpa Granite: Rb-Sr work on Akpa Granite was undertaken during the DST sponsored Contact Programme on Isotope Geology and Geochronology: Rb-Sr systematics have yielded wholerock isochron age of 558 ±69 Ma on 4 samples. Muscovite age tuned out to be 19.335±0.07 Ma, while its bites are of14.197± 0.02 and 12.359± 0.01 Ma.

(iv) Jispa Granite: Five-point whole-rock isochron yields an age of 517±26 Ma 298±8.7, while 5 biotite age ranges from 15.14± 0.16 to 32.75± 0.34 with a preponderance of ~25 Ma.

ICP-MS National Facility (CSIR-DST Funded Project) at NGRI, Hyderabad

The ICP-MS Lab at NGRI has been catering to several in-house and sponsored projects. About 8000 samples were analyzed for trace, REE, PGE and Au during Jan-Dec.2005. ICP-MS was extensively utilized for generating geo-analytical data by universities, national laboratories, research organisations and industrial establishments;

Analytical methods were developed for the precise estimation of PGE in geological samples, trace elements in air particulates, plant samples, fish tissues, blood plasma, steiner films and inorganic impurities in bulk drug samples. A study was also undertaken for analysis of seawater samples for V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Se, Mo, Cd, Pb and U at various pH (ranging from 2 to 8.9) following APDC/ MIBK pre-concentration method. PGE were estimated in road dust and the results were found to encouraging.

New Programme on Science of Shallow Subsurface

In order to address several issues of societal and environmental relevance a new programme in earth sciences has been initiated with multidisciplinary and multi-institutional participation. Under this programme integrated proposals on three corridors in Ganga, Cauvery river basins and Gujarat alluvial plains have been formulated. In Gujarat alluvial plains, three windows viz., Baroda, Narmada and Kutchh have been identified. Eighteen projects on multidisciplinary aspects with multi-institutional participation have been sanctioned for Gujarat corridor. Under Ganga corridor, five projects and under Cauvery corridor, nine projects have been sanctioned. Scientific Research

Himalayan Glaciology

The Himalayan Glaciology programme of DST is continuing since 1986. The programme is aimed at understanding the behaviour of glaciers in general and their interaction with climate and hydrological systems in the region as also to train manpower and create research and development related facilities in this vital area of societal relevance. The programme is overseen by the Programme Advisory and Monitoring Committee on Himalayan Glaciology (PAMC-HG).

During the period, the Programme Advisory and Monitoring Committee on Himalayan Glaciology (PAMC-HG) met twice. The PAMC-HG reviewed progress of the on-going projects as also achievements made under the completed projects. The Committee also considered new proposals for funding and deliberated on various issues for overall development of the Himalayan Glaciology Programme.

A brief account of the progress made in respect of individual projects under Gangotri Glacier and Dokriani Bamak Glacier is given below:

• Establishment and operation of mountain meteorological observatory at Gangotri Glacier

The work was carried out by Snow and Avalanche Study Establishment, Chandigarh by establishing one research station and 3 Automatic Weather Stations in various zones of Glaciers of varying height between 3800m-5000m. The data collected from this research stations and AWS were connected to user agencies and to SASE Research and Development Centre for its refinement, documentation and use in research models. The aim of establishing High Altitude Research Station at Bhojbassa and 3 Automatic Weather Stations on Glacial surfaces were completed successfully. These equipments and stations were functioning well.

The standard meteorological observatory (30mm x 30 m ) was set up at about 3800m altitude near the gauging site at Bhojbassa. The observatory was equipped with meteorolgical instruments. Some observations were made round the clock using automatic instruments. This year rotation data was also collected and the analysis of the same was under progress. For collecting discharge data for summer 2005, an additional discharge gauges site was established about 2 km up stream of the previously existing gauging site. Discharge data was collected at both the sites for the whole summer period. The important feature of discharge observed during summer 2005 was that melting of glacier was slow in the beginning due to cooler climatic conditions. However, after sometime it reached to the range of discharge of other years. Actual values of discharge would be made available after the analysis of data. The samples of rainfall, snow, ice and discharge were collected during summer 2005 for isotopic analysis of each component. The samples were being analysed at NIH, Nuclear Laboratory. This analysis would be helpful in identifying contribution of different components in the discharge and its variation with time.

• SAR data analysis for snow pack Characteristics and Glacier (Movement Studies on Gangotri Glacier)

These projects have since been implemented recently and the detailed information about Envisat ASAR data was obtained. This software would give important information like data type, polarisation, ascending/descending pass, Swath mode, range spacing, azimuth spacing etc. The research staff has been recruited and field visit has been undertaken to collect preliminary data.

• Studies on Dokriani Bamak Glacier

The studies on Dokriani Bamak in Bagirathi river catchment were focused on atmospheric deposition, glacier mass balance, glacier run off and its facts on the river hydrologic regime. The sediment transfer from Glacierised , non-glacierised and hydrology on Din Gad catchment. Field visits were undertaken to collect the data related to above mentioned areas. Three discharge and three meteorological stations were established in the Din Gad catchment to monitor, discharge, suspended sediments concentration and meteorolgical parameters were established. Data were being collected for further analysis. Scientific Research

Monsoon & Tropical Climate (MONTCLIM) & Agrometeorology

Research and developmental activities towards better understanding of the complex land-oceanatmosphere interactive processes at different spatial and temporal scales are being coordinated under atmospheric science scheme. Studies conducted under MONTBLEX related to the physics and dynamics of monsoons, coupled land-ocean-atmospheric system, Agrometeorology and indigenous development of technology for atmospheric science applications are being supported under MONTCLIM. In order to study the effect of weather and climate in the tropics, efforts are being made to improve parameterization of land-ocean-atmospheric processes in the atmospheric general circulation models (GCM). During the period two meetings of the 'Project Advisory and Monitoring Committee on Weather and Climate Research Programmes' were organized. A group monitoring workshop was organized in which 16 completed projects were evaluated and monitored the progress of the 22 ongoing projects. The salient achievements under the above programs are as follows:

Atmospheric Dynamics and Modeling

Study on the variability of winter/spring Eurasian snow depth and the subsequent Indian summer monsoon circulation and rainfall in the annual and decadal time scales revealed that winter snow depth anomaly over west (east) Eurasia has the highest negative (positive) correlation with the subsequent Indian Summer Monsoon Rainfall. Model simulations confirm that excess Tibetan snow in April decreases the rainfall over India in the following monsoon season. A study on the biosphere-atmosphere interaction on the monsoon circulation has been completed. The northward propagation of model precipitation events is found to follow the real climatic manifestation of intra-seasonal behavior of the Indian Summer Monsoon. Study of Tropical Cyclones over the Orissa region with a regional model (MM5), is in progress. Two coastal blocks of Bhadrak district (Orissa) has been surveyed and documented the demographic information within 10 km in the coastal zone.

Ocean -Atmosphere Coupling

A study has been carried out to examine the surface characteristics of the atmospheric boundary layer (ABL) over the eastern Arabian Sea and the western coastal land stations during the summer monsoon season of 2002. Surface meteorological observations collected onboard ORV Sagar Kanya and five land stations along the west coast of India during the ARMEX-2002 indicated that the variations in the surface parameters are less over the oceanic regions as compared to coastal stations. Study of air-sea interaction using Bay of Bengal Monsoon Experiment data set is under progress.

Atmospheric Chemistry

Monitoring of ambient air quality and surface ozone in Kullu-Manali tourist complex indicated an increasing trend of atmospheric aerosols. High concentrations of total suspended particulate matter (TSP) and particulate matter below 10 microns in size (PM10) in a particular month or season at Mohal and Kullu may be due to vehicular emission during peak tourist season and bio-mass burning during winter. Washout effect due to rain results in minimum level of TSP and PM10. The monthly SO2 level recorded at Mohal and Kullu are less than the ambient air quality standards. Precipitation samples were collected in eight different environments around, "National Capital Region" of Delhi during the monsoon season and analyzed. Rain water was found to be alkaline in nature with an average pH value of 6.22. Studies on the impact of urban air pollution in Delhi, indicated a weak association between air pollution and respiratory health. It was observed that individuals from higher pollution zone have lower mean level for each parameter i.e., lower lung efficiency as compared to those from lower pollution zone. There was a highly significant linear relationship between increasing age and occurrence of symptoms. In both pollution zones, there was a greater proportion of symptomatic among male subjects than among females. The chemical composition of fog water samples collected at Delhi showed that the fog was alkaline in nature. Further measurements of physiochemical parameters and aerosols at these environments are in progress.

Monitoring of chemical composition of aerosols during the winter and summer months (dust events) and radioactive forcing of aerosols in Kanpur region in the Ganga basin has been undertaken. The effect of the transported dusts on the aerosol optical properties is analysed. The source of these dusts are inferred based on air mass trajectories and satellite data, indicates mixing with anthropogenic pollutants along their transport pathways. Zinc and Lead concentration is higher in fine mode compared to coarse mode. Cadmium was almost absent in coarse mode. The size distribution parameters for different aerosol species in fine and coarse mode were calculated. Studies on aerosols and black carbon and their impacts in Chatiisgarh region are in progress. Seasonal and temporal variation of suspended particulate matter is being studied.

Agrometeorology

The field experiments on land-surface processes, radiation balance of wheat crop were carried out. The study indicated higher wind speed during booting phase was detrimental for wheat. Higher wind may cause lodging of crop resulting in poor yield. Daily mean incident solar radiation during the crop season received by the wheat field was 393 W/m², 19.5% reflected back to the atmosphere as albedo, while 63% remained as net radiation. The experimental data sets required for the 'Soil Plant Atmosphere Water (SPAW)' model were collected and analyzed for rabi wheat crop. SPAW model was used to simulate soil moisture profiles in sandy loam soil of Anand under wheat crop grown over a period of three years (2001-04) to test the validation of the model and demonstrate its capability for identifying the threshold soil moisture needed for irrigation scheduling. The testing and validation process of the model for kharif groundnut crop is in progress.

A study for prediction of mustard aphid based on crop-weather-aphid relationship under Punjab conditions, is underway. Regression analysis revealed that aphid population was negatively correlated with maximum and minimum temperature whereas it was positively correlated with relative humidity. Historical data on aphid incidence was analysed in relation to rainfall, date of sowing, wind direction and degree days. Evaluation of potential productivity of major oil seed crops in Punjab using crop simulation models is being carried out. The field crop data, weather and soil information are being put in dynamic crop growth simulation model for groundnut. The sensitivity analysis, calibration and validation of the model using field data is currently in progress. A study is initiated for validation and application of dynamic CERES-Wheat model for simulating growth and yield of wheat in temperate Kashmir. Initiated a study on the use of climatic predictions as inputs to reservoir operation models with a case study of Mahanadi river basin. Also initiated studies towards the integration of application of medium range weather forecasts and Agromet databank facility towards providing skillful advisories to the farmers of Andhra Pradesh. The Expert Committee reports on i) Agrometeorology in India: A kaleidoscopic view of activities and Vision for R&D in Agrometeorology are being published towards accelerating the research activities in Agrometeorology.

Meso-scale experiments on Thunderstorms/Norwesters

In order to undertake detailed investigations on the 'Norwesters' or severe thunderstorms in the eastern and northeastern regions of India, prepared a Science Plan on 'Severe Thunderstorms: Observations and Regional Modeling (STORM)'. Considering the complex physical processes, intensive observational strategy and modeling activities required for a longer period, a "Programme Implementation Committee (PIC) on STORM" has been constituted. The PIC-STORM is working towards initiating the Programme with a pilot experiment during April-May, 2006.

Technology Development

The indigenously developed Wind Profiler-Radio Acoustic Sounding System (WP/RASS) for continuous atmospheric monitoring was made fully operational. A data archival and utilization centre was established and software was developed for analyzing the data. A web site has been uploaded. Special observational studies are being planned to study thunderstorms and rain drop size distribution using WP/RASS. Scientific Research

Indian Climate Research Programme (ICRP)

Studies related to temporal and spatial variability of climate, past climate and climate change and relationships between climate and agriculture are being coordinated under ICRP. Special emphasis was given to evolve and implement multi-agency, multi-disciplinary coordinated field experimental campaigns to investigate the land-ocean-atmosphere interactions and their role in monsoon variability. Successfully planned and completed the observational campaigns of the Arabian Sea Monsoon Experiment (ARMEX) during 2002, 2003 and 2005. The initial results of the ARMEX were published as a special issue of the Journal 'Mausam', January, 2005. A Brainstorming Seminar on Continental Tropical Convergence Zone (CTCZ) was organized to assess the scientific potential to initiate another large scale monsoon experiment. A Scientific Steering Committee for CTCZ is constituted for preparing detailed science and implementation plans to be implemented during 2006-2010. The salient achievements under the programme are as follows:

Summer Monsoon Prediction

Long range monsoon forecasting is an important problem with implications in varied socio-economic sectors. Modeling the monsoon behavior towards developing an efficient monsoon prediction from 10-30 days and seasonal scale is very much essential. To deliberate on the recommendations of the a 'Workshop on Extended Range Monsoon Prediction (ERMP), was organized at SAC, Ahmedabad, during March, 2004. Four Working Groups were constituted on the following i) Observational Systems ii) Models and Diagnostics iii) Computing and Human Resources iv) Field Campaigns. Five meetings of the Working Groups were organized during the period under report. Based on the report of the Working Group on Models and Diagnostics, sincere efforts are put by all the modelers to provide experimental ERMP for 2005. This is the first time all the atmospheric modelers are working together for evolving a national programme on ERMP. An attempt is also made for empirical prediction of active and weak phases of the Indian summer monsoon. The transitions from active to break conditions are intrinsically more chaotic than transitions from active to break. This study indicates that active monsoon conditions would be much more difficult to predict than breaks. An empirical model for prediction of monsoon breaks upto 18 days in advance is demonstrated. This model has high potential for applying it on real time extended range prediction of monsoon breaks in the years to come.

Model inter-comparison studies have been initiated with global and regional atmospheric models to assess the skill of individual models in predicting various atmospheric processes associated with monthly and seasonal forecasts over the Indian region.

Palaeoclimate Studies

Long-term climate change in western Himalaya using high-resolution tree-ring data obtained from samples of Cedrus deodara (Himalayan cedar) and Pinus gerardiana (chilgoja pine) from various sites in Kinnaur, Himachal Pradesh. A 1584-year long ring-width chronology of Himalayan pencil cedar (Juniperus macropoda) using increment core and disc samples, collected from moisture stressed sites in Keylong, Lahul, Himachal Pradesh was developed. This makes the longest record of tree ring chronology from the Indian region. The preliminary study has indicated the possibility of developing more than 1000-year long chronologies of Pinus gerardiana and Cedrus deodara from this region. Efforts are being made to develop chronology using biological growth trend to obtain low frequency variations in climate.

Preparation of rainfall Atlas

An Atlas on the spatial features of moisture regions and rainfall of India was prepared. This Atlas covers longest instrumental monthly, seasonal and annual rainfall series for the whole country, seven homogeneous rainfall zones, different states, different meteorological sub-divisions and different major river basins.

Arabian Sea Monsoon Experiment (ARMEX)

Successfully completed the Arabian Sea Monsoon Experiment (ARMEX). The main aim of this large-scale land-ocean-atmosphere field experiment was to obtain more insight into the intricacies involved in the formation and development of the off-shore vortex and the warm pool over the Arabian Sea. About 24 organizations participated in this national endeavor. All the observational data sets are collated and the quality checked data sets were made available to the Indian scientific community for detailed analysis. A special 21 day cruise on ORV Sagar Kanya was organized during April-May, 2005 to meet the objectives of ARMEX that could not be accomplished during 2003. A met-ocean buoy was deployed by the National Institute of Ocean Technology, Chennai, with additional sensors for this experiment. The buoy was successfully retrieved without any loss of sub-surface data.

Numerical modeling of the off-shore trough and associated heavy rainfall events during ARMEX was carried out. Four cases of heavy rainfall along the west coast of India during ARMEX-1. During July, 2002, the boundary layer moisture convergence was inhibited as a result of reduced convective heating in the middle and upper troposphere. The dryness continued until the boundary layer can be moistened by advective processes and was carried out upto 3.0 KMs to shallow convective boundary layer during the supressed convection period had a single mixing line through the cloud and inverstion layer. However, with deep convective boundary layers at times, double mixing lines were noted, possibly due to precipitation and re-evaporation process. The bundary layer height (BLH) increased significantly during active convection processes just before the onset of heavy rainfall. The diurnal variability of BLH over Goa was more pronounced than that observed over the Arabian Sea. However, the average BLH over the Arabian Sea off the west coast of India during the convectively active case was higher than that observed over Goa.

The study of atomosphere-land-ocean interactions indicated that the heat budget of the eastern Arabian Sea behaves similar to that of Bay of Bengal, implying the role of low salinity in the thermodynamics of the upper layer. On interannual time scales the heat budgets of the eastern Arabina Sea and Bay of Bengal are strongly controlled by the winds through the latent heat flux. The formation of barrier layers following the rain events observed during the summer monsoon of 2002 also confirms the importance of salinity in thermodynamics of the eastern Arabian Sea. However, longer time series measurements are necessary to quantify these effects. Hydrographyic observations showed that the upwelling first starts in the south and then propagates towards north. It reaches off Goa in October.

Expendable Bathy Thermography (XBT) observations were systematically collected at fortnightly
intervals along a triangular transect (Kochi-Minicoy-Kavaratti-Chetlat-Kochi) onboard M/s. Shipping Corporation of India Ltd passenger cum cargo ships. One of the most interesting results emerged from the analysis of XBT data is the occurrence of temperature inversions and their spatial and temporal variation in the Lakshadweep Sea (LS) during winter season. Percentage of occurrence of temperature inversions in the LS showed considerable year to year variability. Inversions first appeared off Kochi during December, by January they moved westwards and occupied the entire region by February, thus indicating westward migration of temperature inversions. Numerical simulation also showed such a westward propagation of temperature inversions in the LS with a phase shift. Temperature inversions occur in the LS during winter, coinciding with the arrival of Bay of Bengal low salinity waters. These low salinity waters and the temperature inversions propagated westwards together. This is the first observational evidence for the westward propagation similar to the "Lakshadweep High" propagate westwards as a consequence of westward propagating Rossby waves. The formation, westward propagation and eventual annihilation of the barrier layer in the LS are thus a consequence of ocean dynamics and near-surface thermodynamics involving air-sea fluxes. The ARMEX data also revealed that the remotely forced ocean dynamics plays an active role in the genesis and collapse of the core of the warm pool in the South-Eastern Arabian Sea.

During ARMEX, extensive measurements of aerosol spectral optical depth, mass concentration and mass size distribution of ambient aerosols as well as mass concentration of aerosol Black Carbon (BC) were made on board ORV Sagar Kanya during the inter-monsoon period over the Arabian Sea adjoining Indian peninsula. Simultaneous measurements of Aerosol optical depth (AOD) were made at different regions over the adjoining Indian land mass. Mean AODs over the ocean (0.44) were comparable to those over the coastal land (0.47) but were lower than the values observed over the plateau regions of central Indian Peninsula (0.61). A substantial reduction in the atmospheric forcing observed was compared to those reported during north-east monsoon is attributed to the reduced BC mass fraction. This large in-homogeneity in aerosol forcing over the ocean and land at short time scales as well as their sensitivity to the nature of the air-back-trajectories have important implications in assessing climate impact. Further, observations during April, 2005 indicated that the effective heat flux determines mixed layer temperature. The observed and predicted mixed layer temperatures are in good agreement.