Development of a High-Resolution Multiscale Modeling and Prediction System for Bay of Bengal, Part I: Climatology-Based Simulations

A high-resolution (10 km × 10 km) multiscale ocean modeling system was developed for short-term (1 - 2 weeks) ocean state hindcasting/forecasting in the Bay of Bengal (BOB) region. This paper is Part I of a two-part series of studies. The Regional Ocean Modeling System (ROMS) was implemented and initialized with Levitus 1/4° climatological fields for short-term forecasting. The results from these climatology-based model simulations for three representative months (February, June and October) in three different seasons (winter, summer and autumn) are discussed herein. This high-resolution model implementation simulates most of the observed dominant circulation features. The multiscale features during February include an anticyclonic basin-scalegyre with a strong western boundary current (WBC) in the western basin, the formation of several shallow mesoscale eddies in the head of the Bay and a cyclonic sub-basin-scale Myanmar Gyre in the northeast. During June, no well-defined boundary current is simulated along the Indian coast;instead, alternating cyclonic and anticyclonic eddies appear along the east coast with cross-basin eastward flow to support a deep cyclonic Andaman Gyre. In October, a basin-scale cyclonic gyre with a continuous well-defined East India Coastal Current (EICC), weak inflow from the Malacca Strait to the Andaman Sea and advection of BOB water into the Arabian Sea via the Palk Strait are simulated well by the model. A number of mesoscale eddies appear on the eastern half of the basin during October. Physical pattern of simulated eddies and transports across selected sections are validated against available drifter climatology, ARGO data and previous observations. Application of this system to synoptic short-term predictions for October 2008 will be presented in Part II.

Development of a High-Resolution Multiscale Modeling and Prediction System for Bay of Bengal, Part II: An Application to October 2008

A high-resolution (10 km × 10 km) multiscale ocean modeling system was developed for the Bay of Bengal (BOB) region for short-term ocean hindcasts/forecasts. A physical validation of this system that was based on climatological initialization and short-term simulations was presented in Part I of this series of studies. Realistic structures for prevalent eddies, fronts and gyres were reasonably reproduced and validated for three individual months (February, June and October). In this study, we present an application and synoptic validation of the system for October 2008 in a hindcast mode. The system is based on the Regional Ocean Modeling System (ROMS), which assimilates satellite and in-situ measurements within the background climatology using an objective analysis to produce the synoptic initial condition for the model and/or to produce an estimation of the current ocean state. A meteorological forecast is then input into this synoptic three-dimensional ocean model to produce the ocean hindcast/forecast. The high-density Array for Real-time Geotropic Oceanography (ARGO) observations, and the Tropical Rain Measuring Mission (TRMM) satellite’s microwave imager (TMI) passes during the beginning of the month of October 2008, provided a unique opportunity for the system to assimilate these in-situ observations at initialization. Then, the ARGO and TMI observations during the later part of October 2008 were used for the statistical validation of the system’s fidelity. The validation shows that the hindcast/forecast system can reasonably predict the ocean currents, temperature and salinity. The forecast error increases as the forecast time window increases, although the system has a reasonable predictability for up to seven to ten days. The assimilation of both in-situ ARGO and satellite data at initialization produced better hindcasts/forecasts.

Characterizing Shorea robusta communities in the part of Indian Terai landscape

Shorea robusta Gaertn. f.（Sal）is one of the important tim-ber-yielding plants in India, which dominates the vegetation of Terai landscape of Uttar Pradesh state in India forming various communities based on its associations. The present study deals with delineation, map-ping and characterization of various communities of Sal （Shorea robusta） forests in Terai landscape of Uttar Pradesh, India ranging across over 16 districts. Field survey and visual interpretation based forest vegetation type classification and mapping was carried out as part of the project entitled ‘Biodiversity characterization at landscape level using remote sensing and GIS’. Indian Remote Sensing-P6 （Resourcesat-1） Linear Imaging Self Scanner-III satellite data was used during the study. The total area covered by different Sal forests was found to be approximately 2256.77 km2. Sal communities were identified and characterized based on their spectral properties, physiognomy and phytosociological charac-teristics. Following nine Sal communities were identified, delineated and mapped with reasonable accuracyviz.,Chandar,Damar, dry plains, moist plains, western alluvium, western alluvium plains, mixed moist deciduous, mixed dry deciduous andSiwalik. It is evident from the area estimates that mixed moist deciduous Sal is the most dominant commu-nity in the region covering around （1613.90 km2）, other major communi-ties were found as western alluvium plains Sal （362.44 km2）, mixed dry deciduous Sal （362.44 km2） and dry plains Sal （107.71 km2）. The Terai landscape of Uttar Pradesh faces tremendous anthropogenic pressure leading to deterioration of the forests. Community level information could be used monitoring the status as well as for micro level conserva-tion and planning of the Sal forests in Terai Landscape of Uttar Pradesh.

Modeling the Effects of Nutrient Dynamics and Surface Circulation on the Productivity of Hooghly Estuary

River estuarine environment plays a key role in the cycling of biological and chemical parameters and a significant region for the transaction of freshwater and seawater. In the present study, a first attempt has been made towards the development of a coupled three-dimensional hydrodynamic circulation model with four compartment （nitrate, phytoplankton, zooplankton and detritus） biogeochemical model in the Hooghly estuary （21 °36′-22° 16′1 and 87°42＇-88°15′E） to simulate the varying effect of plankton biomass with the heavy input of anthropogenic litter from industrial effluents of Haldia port which is effecting the chemical and biological processes that control the plankton dynamics in the estuary. In-situ observational data for physico-chemical and biological parameters are collected from Calcutta University during 2010 are assimilated using multiscale OA （objective analysis） for different seasons and incorporated in ROMS （Regional Ocean Modeling System） to develop a high resolution （0.5 km x 0.5 kin） biogeochemical model. Recent analysis on physico-chemical parameters of the estuary is done as it is one of the largest estuaries in India and is the habitat for vast biodiversity. Influence of high nitrate （above 34 μg/L） and phosphate （5.22 μg/L） is predominant whereas DO （dissolved oxygen） is low （4.07 mg/L） in the Haldi River mouth which is sliding the productivity （less than 1 mg/L） and also affects water quality.