Role of interaction between dynamics,thermodynamics and cloud microphysics on summer monsoon precipitating clouds over the Myanmar Coast and the Western Ghats     

Siddharth Kumar  Anupam Hazra  B. N. Goswami 《Climate Dynamics》2014,43(3-4):911-924

Indian summer monsoon circulation can be characterized by mean tropospheric temperature (TT) gradient between ocean and land. Two major heat sources, one near the Myanmar Coast and the other near the Western Ghats play seminal role in defining this TT gradient. While both regions are characterized by very similar orographic features, there are significant differences in frequency of occurrence of precipitating clouds and their characteristics even when the amount of rain in June–July months is almost same in the two regions. Deeper (shallower) clouds appear more frequently over the Myanmar Coast (the Western Ghats). There is a sharp decrease in amount of rainfall from June–July to August–September in both the areas. Rather counter intuitively, during the June–July–August–September season, low and moderate rains contribute more to the total rain in the Myanmar Coast while heavy rains contribute more to the total rain in the Western Ghats. Western Ghats also gets more intense rains but less frequently. With significant differences in moisture availability, updraft, amount and characteristics of cloud condensate in the two regions, this study proposes that the nontrivial differences in features between them could be explained by linkages between cloud microphysics and large scale dynamics. Presence of more cloud liquid water and the role of giant cloud condensation nuclei reveals dominance of warm rain process in the Western Ghats whereas more cloud ice, snow and graupel formation in the Myanmar Coast indicates stronger possibility of cold rain coming from mixed phase processes. Stronger heating caused by mixed phase process in the mid and upper troposphere in the Myanmar Coast and its feedback on buoyancy of air parcel explains the appearance of deeper clouds. Thus, our study highlights importance of mixed phase processes, a major cause of uncertainty in GCMs.  相似文献   

Analyses of rainfall using probability distribution and Markov chain models for crop planning in Daspalla region in Odisha,India     

K. G. Mandal  J. Padhi  A. Kumar  S. Ghosh  D. K. Panda  R. K. Mohanty  M. Raychaudhuri 《Theoretical and Applied Climatology》2015,121(3-4):517-528

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Improvement in convective and stratiform rain fractions over the Indian region with introduction of new ice nucleation parameterization in ECHAM5     

Anupam Hazra  H. S. Chaudhari  S. Pokhrel 《Theoretical and Applied Climatology》2015,120(1-2):173-182

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Spectral analysis and Euler deconvolution technique of gravity data to decipher the basement depth in the Dehradun-Badrinath area     

G. K. Ghosh  C. L. Singh 《Journal of the Geological Society of India》2014,83(5):501-512

The stratigraphic and tectonic setting in the northwest part of Himalayan belt is complex and thrusted due to the collision of Indian plate and the Eurasian plate. During the past, the Himalaya is divided into four parts; these are Outer Himalaya, Lesser Himalaya, Greater or Higher Himalaya and Tethys Himalaya. The appearance of basement rocks played a significant role in the Himalayan periphery for stratigraphic, structural and tectonic movement. The deformation pattern of the crustal rocks causing the rise of basement rocks which constitutes an integral part of crustal configuration during the evolutionary stages of the Himalaya. In this study, an attempt has been made to estimate the basement depth configuration using spectral analysis and Euler deconvolution technique of gravity data in the northwest Himalaya region. The elevation increases continuously from 500 m to 5100 m in SW to NE direction, however, Bouguer gravity anomaly decreases continuously from ?130 mGal to ?390 mGal in SW to NE direction due to the isostaic adjustment. Gravity anomaly is very low near Harsil, Badrinath and Joshimath area and observed higher elevation due to the deep rooted basement. However, there are extrusion of crystalline basement in and around the Badrinath area due to the resettlement of geologic process which are overlaid to the top surface of the sedimentary layers. Euler deconvolution technique has been applied to detect the direct basement depth and results show a good correlation with the average depth of the spectral analysis and other works carried by different authors. Three gravity profiles are selected in appropriate places orienting SW-NE direction with a profile length of 160 km, 150 km and 140 km respectively in the study area for calculating the average depth of the basement rock. The average basement depth calculated is around 11.27 km using the spectral analysis technique and results are well correlated with the results of various workers. Euler deconvolution studies along the three selected profiles have been interpreted. It has been observed that there are more number of cluster points falling between depth ranges of 10 to 15 km, dipping in SW to NE direction. Euler’s study shows deep rooted connection near Main Frontal Thrust (MFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT), Bearing Thrust (BT) and Vaikrita Thrust (VT) locations as per profile study. Based on these studies three geological models have been prepared along the profiles showing different tectonic resettlement and depth of crystalline basement. Crystalline rocks exposed at the surface may be due to uplift along the shear in the MCT zone by kinetic flow basically, Munsiayari Thrust (MT) and VT in the of NW-Himalaya region.  相似文献   

Plant remains from the Tharumsa Formation of Ladakh,India     

R. C. Mehrotra  Madhav Kumar  Amit K. Ghosh  K. Kumar  Ritesh Arya 《Journal of the Geological Society of India》2014,83(6):647-652

Plant remains, including both mega and micro collected from the middle part of the Tharumsa Foramtion (early Miocene) are described for the first time from the Tharumsa village of the Kargil district, Jammu and Kashmir to reconstruct the palaeoenvironment. They indicate their affinities with Broussonetia of the Moraceae and Abies, Cedrus and Pinus of the Pinaceae. Their presence indicates warm and moist tropical to sub-tropical climate in the Kargil area during the depositional period against the cold and dry climate prevailing at present.  相似文献   

Chromian spinel-rich black sands from eastern shoreline of Andaman Island,India: Implication for source characteristics     

Koyel Bhatta  Biswajit Ghosh 《Journal of Earth System Science》2014,123(6):1387-1397

Black sands rich in chromian spinel commonly occur in pockets along the eastern shoreline of Andaman Island where various types of peridotites and volcanics belonging to the Andaman ophiolite suite are exposed in close vicinity. The chemistry of these detrital chromian spinels has been extensively used here in identifying the source rocks vis-à-vis deciphering the source characteristics. The composition of the chromian spinels (Cr#: 0.20–0.88, Mg#: 0.26–0.77, Al ₂ O ₃: 5.04–48.21 wt.%, TiO ₂: up to 1.39 wt.% and Fe ²⁺/Fe ³⁺: 1.73–9.12) varies widely signifying multiple sources, of which mantle peridotites and volcanic rocks are relevant in an ophiolitic terrain. The volcanic chromian spinels are relatively fresh, commonly euhedral, sometimes with compositional variations, and contain inclusions in contrast to the mantle peridotitic chromian spinels which are rounded, extensively fractured, and altered. We used a number of geochemical bivariate plots in order to know the provenance protoliths. The volcanic chromian spinels show geochemical characters of MORB, related to spreading centers (either MOR or back-arc) and also boninites/arc-tholeiites, related to active subduction. On the other hand, the peridotitic spinels indicate partially depleted lherzolite and depleted harzburgite source of the ophiolite suite.  相似文献   

Preferential formation of C-O bonds in carbonate minerals, estimated using first-principles lattice dynamics     

Edwin A. Schauble  Prosenjit Ghosh 《Geochimica et cosmochimica acta》2006,70(10):2510-2529

Equilibrium constants for internal isotopic exchange reactions of the type: