Observational and Numerical Study on the Influence of Large-Scale Flow Direction and Coastline Shape on Sea-Breeze Evolution

In this study radar, surface observations and numericalsimulations are used to examine the inland penetrationand intensity of the sea breeze during various large-scaleflow regimes along the curved coastline of the Carolinas,U.S.A. The results clearly indicate that the flow directionrelative to the curved coastline has a significant effecton the sea-breeze evolution.Overall, during northerly flow regimes alongthe curved North Carolina coast, observationsand numerical simulations show that the sea-breezefront has a tendency to remain close to the south-facingcoast. During these same flow regimes the frontmoves further inland relative to the east-facingcoast. The sea-breeze front during westerly flowcases progressed further inland relative to the southcoast and less so from the east-facing coastline.South-westerly flow allows the sea breeze to moveinland from both coastlines but the coastal shapeinfluence makes the inland penetration less fromthe easterly facing beaches. During periods of lightonshore flow (south-east), the sea breeze movesconsiderable distances inland but is not discernableuntil later in the afternoon. The simulations indicatedthat the sea-breeze intensity is greatest (least) when thelarge-scale flow direction has an offshore (onshore)component. Model results indicate the existence of astrong front well inland in the late afternoon duringlight onshore flow. Also noted was that the simulatedsea-breeze front develops earlier in the afternoon duringoffshore regimes and later in the day as the large-scaleflow becomes more onshore. It is concluded that thecoastline shape and coast-relative flow direction areimportant factors in determining how the sea-breezecirculation evolves spatially.     

Segmentation and classification of high spatial resolution images based on Hölder exponents and variance

Pixel-based or texture-based classification technique individually does not yield an appropriate result in classifying the high spatial resolution remote sensing imagery since it comprises textured and non-textured regions. In this study, Hölder exponents (HE) and variance (VAR) are used together to transform the image for measuring texture. A threshold is derived to segment the transformed image into textured and non-textured regions. Subsequently, the original image is extracted into textured and non-textured regions using this segmented image mask. Afterward, extracted textured region is classified using ISODATA classification algorithm considering HE, VAR, and intensity values of individual pixel of textured region. And extracted non-textured region of the image is classified using ISODATA classification algorithm. In case of non-textured region, HE and VAR value of individual pixel is not considered for classification for significant textural variation is not found among different classes. Consequently, the classified outputs of non-textured and textured regions that are generated independently are merged together to get the final classified image. IKONOS 1 m PAN images are classified using the proposed algorithm, and the classification accuracy is more than 88%.     

An iterative algorithm for removing the effect of thin cloud cover from LANDSAT imagery

In this paper, we propose an iterative algorithm for removing the effect of thin cloud cover from LANDSAT imagery. It is seen that the noise in such images is multiplicative as well as additive. The recorded image is first processed to update different parameters of the image formation model to known values. Processing algorithm and knowledge of parameter values are developed by considering the physics of the situation. A low-pass filter is then applied to the processed image to remove the effect of the cloud. The filter is of a tapered shape, and its parameters are adjusted to minimize the estimation error.     

Impact of cyclone Nilam on tropical lower atmospheric dynamics

A deep depression formed over the Bay of Bengal on 28 October 2012, and developed into a cyclonic storm. After landfall near the south coast of Chennai, cyclone Nilam moved north-northwestwards. Coordinated experiments were conducted from the Indian stations of Gadanki(13.5?N, 79.2?E) and Hyderabad(17.4?N, 78.5?E) to study the modification of gravity-wave activity and turbulence by cyclone Nilam, using GPS radiosonde and mesosphere–stratosphere–troposphere radar data. The horizontal velocities underwent large changes during the closest approach of the storm to the experimental sites. Hodograph analysis revealed that inertia gravity waves(IGWs) associated with the cyclone changed their directions from northeast(control time) to northwest following the path of the cyclone. The momentum flux of IGWs and short-period gravity waves(1–8 h) enhanced prior to, and during, the passage of the storm(±0.05 m2s-2and ±0.3 m2s-2, respectively), compared to the flux after its passage. The corresponding body forces underwent similar changes, with values ranging between ±2–4m s-1d-1and ±12–15 m s-1d-1. The turbulence refractivity structure constant(C2n) showed large values below 10 km before the passage of the cyclone when humidity in the region was very high. Turbulence and humidity reduced during the passage of the storm when a turbulent layer at ～17 km became more intense. Turbulence in the lower troposphere and near the tropopause became weak after the passage of the cyclone.     

Estimation of daily average net radiation and its variation over West Bengal,India using MODIS products

A simple and exclusively satellite-based instantaneous net radiation (INR) and its components have been estimated and it is based on the method proposed. The method has been used to check its suitability over West Bengal, India on clear sky days which is eliminating the need for ground-based observations. The method explicitly recognizes the need for spatially varied input parameters to estimate net radiation using remote sensing information and provides a distributed daily average net radiation map with finer spatial resolution. The satellite-derived radiative flux components were compared with the Eddy Flux Tower measurements located at Bonnie camp within mangrove forest. The bias, root-mean square error and R² between modelled and measured INR are 52.07, 49.5 W m^?2 and 0.74, respectively which are within the acceptable limit. The errors in the downward short wave and long wave as well as upward short-wave and long-wave radiative flux are 13.78, 3.54, 12.41 and 3.54%, respectively. Further, variations of all the radiative flux components were analysed over different eco-systems.     

Buried nodules and associated sediments from the central Indian basin

Buried nodules from siliceous sediments in the central Indian Basin are morphologically variable and mineralogically consist ofd-MnO₂ and incipient todorokite. Compositionally they are weakly diagenetic. The sediment coarse fractions (>63 μm) at different depths show variable abundances of micronodules, volcanic glass shards and biodebris. Dissolution of biodebris increases and abundance of micronodules decreases with increasing depth. Enrichment in Mn, Fe, Cu, Ni, Co, together with a decrease in organic carbon in the sediment column, may result from diagenetic metal remobilization. Diagenetically remobilized trace metals might have been utilized for the growth of micronodules over the buried nodules. The details of the chemical analyses of buried nodules and associated sediments can be obtained from the first author.