Structures and morphotectonic evolution of the frontal fold–thrust belt,Kameng river section,Arunachal Himalaya,India

The Neogene–Quaternary Siwalik foreland fold and thrust belt is studied for better understanding of tectonics along the Kameng river section of Arunachal Pradesh, India. The Kimi, Dafla, Subansiri, and the Kimin Formation correspond to Lower, Middle and Upper Siwaliks, respectively. The lithology in the foreland basin is dominantly sandstones, siltstones, claystones, carbonaceous shales, and boulder beds in the upper part. The structural style of the sedimentary sequence from the Main Boundary Thrust southward shows first order ramp-flat geometry. The brittle shear transfers slip across glide horizons to shallower depth. Repeated splay generations from a major regional-scale floor transfers slip from one glide horizon to another that shortens and thickens the crust. In the micro-scale, the lithological response in the structural development is well documented as pressure solution seams and other diagenetic deformation signatures. The basement asperity plays a significant role as the moving thrust front produced a major lateral ramp. The differential movement of the mountain front on both sides of the ramp is decipherable. This is especially true at the western part of the SE flowing Kameng river. The tectonic evolution of the area initiated with slip along the MBT \(\sim \)11 Ma ago along with the deposition of the Siwalik sediments. With southward propagation of the mountain front, the foreland basin shifted towards S, produced splay thrusts from the Himalayan Frontal Thrust-1 (HFT-1), which has been uplifting the Kimin and the older terraces.     

Validation of a satellite-based cyclogenesis technique over the North Indian Ocean

Indian region is severely affected by the tropical cyclones (TCs) due to the long coast line of about 7500 km. Hence, whenever any low level circulation (LLC) forms over the Indian Seas, the prediction of its intensification into a TC is very essential for the management of TC disaster. Satellite Application Centre (SAC) of Indian Space Research Organization (ISRO), Ahmedabad, has developed a technique to predict TCs based on scatterometer-derived winds from the polar orbiting satellite, QuikSCAT and Oceansat-II. The India Meteorological Department (IMD) has acquired the technique and verified it for the years 2010–2013 for operational use. The model is based on the concept of analogs of the sea surface wind distribution at the stage of LLC or vortex (T1.0) as per Dvorak’s classifications, which eventually leads to cyclogenesis (T2.5). The results indicate that the developed model could predict cyclogenesis with a probability of detection of 61% and critical success index of 0.29. However, it shows high over-prediction of the model is better over the Bay of Bengal than over Arabian Sea and during post-monsoon season (September–December) than in pre-monsoon season (March–June).     

Utilization of high-resolution EGM2008 gravity data for geological exploration over the Singhbhum-Orissa Craton,India

High-resolution EIGEN6C4 and EGM2008 Bouguer gravity data of 2190 degree spherical harmonic over the Singhbhum-Orissa Craton, India, have been generated from the International Centre for Global Earth Models. The Bouguer gravity anomaly difference maps of (i) in situ and EIGEN6C4, (ii) in situ and EGM2008 and iii) EIGEN6C4 and EGM2008 of the study area are compared. It reveals that EIGEN6C4 has lesser systematic error than EGM2008. However, from different profile plots of Bouguer gravity, east–west horizontal derivative and north–south horizontal derivative anomalies of the in situ, EIGEN6C4 and EGM2008, it is observed that most of the signatures of lithounits and geological structural elements are delineated very well by EGM2008 and match 94–98% with those of EIGEN6C4. Further, the Bouguer gravity, east–west horizontal derivative and north–south horizontal derivative anomalies of EGM2008 data over the study area have been used effectively for identifying various lithounits and geological structural elements.     

Modeling impacts of erosion and deposition on soil organic carbon in the Big Creek Basin of southern Illinois

Land use land cover (LULC) plays an important role in influencing the spatial intensity of water erosion which is the primary governor of horizontal translocation of soil organic carbon (SOC). The fate of redistributed SOC through erosion remains debatable and the mineralization rate of exposed SOC protected in soil aggregates is the major focus of this argument. Cohesive spatially explicit modeling of SOC and erosion can potentially reduce some of the controversy. To this end we simulated erosion/deposition, and photosynthetic (in situ) flux of SOC in a small watershed of ~ 28.42 ha, located in the Big Creek basin of southern Illinois. The main objectives of this research were: (a) to study erosion and deposition dynamics under different LULC, (b) to examine the extent of carbon dislocation and deposition possible in the study area, and (c) to determine the net SOC accretion and reduction possible by accounting for gains through annual photosynthesis and deposition, and losses from erosion under different LULC scenarios. To fulfill our objectives, we combined GeoWEPP, an erosion/deposition process model, with CENTURY 4.0, an ecosystem model used for simulating SOC. Our results show that between 11 and 31% of the eroded soil gets deposited in the same basin depending on the LULC type, leaving the remainder to be transported downstream. Additionally, as expected, SOC flux due to erosion and deposition varies with the type of management practices. In the case of conservation management practices, the flux associated with erosion and deposition remains below 10% in comparison to in situ SOC transformations due to annual photosynthesis. However in the case of non-conservation management practices this proportion rises above 50%.     

Boreal summer intraseasonal oscillations and seasonal Indian monsoon prediction in DEMETER coupled models

Even though multi-model prediction systems may have better skill in predicting the interannual variability (IAV) of Indian summer monsoon (ISM), the overall performance of the system is limited by the skill of individual models (single model ensembles). The DEMETER project aimed at seasonal-to-interannual prediction is not an exception to this case. The reasons for the poor skill of the DEMETER individual models in predicting the IAV of monsoon is examined in the context of the influence of external and internal components and the interaction between intraseasonal variability (ISV) and IAV. Recently it has been shown that the ISV influences the IAV through very long breaks (VLBs; breaks with duration of more than 10 days) by generating droughts. Further, all VLBs are associated with an eastward propagating Madden–Julian Oscillation (MJO) in the equatorial region, facilitated by air–sea interaction on intraseasonal timescales. This VLB-drought–MJO relationship is analyzed here in detail in the DEMETER models. Analyses indicate that the VLB-drought relationship is poorly captured by almost all the models. VLBs in observations are generated through air–sea interaction on intraseasonal time scale and the models’ inability to simulate VLB-drought relationship is shown to be linked to the models’ inability to represent the air–sea interaction on intraseasonal time scale. Identification of this particular deficiency of the models provides a direction for improvement of the model for monsoon prediction.     

Eastward propagating MJO during boreal summer and Indian monsoon droughts

Improved understanding of underlying mechanism responsible for Indian summer monsoon (ISM) droughts is important due to their profound socio-economic impact over the region. While some droughts are associated with ‘external forcing’ such as the El-Niño and Southern Oscillation (ENSO), many ISM droughts are not related to any known ‘external forcing’. Here, we unravel a fundamental dynamic process responsible for droughts arising not only from external forcing but also those associated with internal dynamics. We show that most ISM droughts are associated with at least one very long break (VLB; breaks with duration of more than 10 days) and that the processes responsible for VLBs may also be the mechanism responsible for ISM droughts. Our analysis also reveals that all extended monsoon breaks (whether co-occurred with El-Niño or not) are associated with an eastward propagating Madden–Julian Oscillation (MJO) in the equatorial Indian Ocean and western Pacific extending to the dateline and westward propagating Rossby waves between 10° and 25°N. The divergent Rossby wave associated with the dry phase of equatorial convection propagates westward towards Indian land, couple with the northward propagating dry phase and leads to the sustenance of breaks. Thus, the propensity of eastward propagating MJO during boreal summer is largely the cause of monsoon droughts. While short breaks are not accompanied by westerly wind events (WWE) over equatorial western Pacific favorable for initiating air–sea interaction, all VLBs are accompanied by sustained WWE. The WWEs associated with all VLB during 1975–2005 initiate air–sea interaction on intraseasonal time scale, extend the warm pool eastward allowing the convectively coupled MJO to propagate further eastward and thereby sustaining the divergent circulation over India and the monsoon break. The ocean–atmosphere coupling on interannual time scale (such as El-Niño) can also produce VLB, but not necessary.     

Possible role of warm SST bias in the simulation of boreal summer monsoon in SINTEX-F2 coupled model

Reasonably realistic climatology of atmospheric and oceanic parameters over the Asian monsoon region is a pre-requisite for models used for monsoon studies. The biases in representing these features lead to problems in representing the strength and variability of Indian summer monsoon (ISM). This study attempts to unravel the ability of a state-of-the-art coupled model, SINTEX-F2, in simulating these characteristics of ISM. The coupled model reproduces the precipitation and circulation climatology reasonably well. However, the mean ISM is weaker than observed, as evident from various monsoon indices. A wavenumber–frequency spectrum analysis reveals that the model intraseasonal oscillations are also weaker-than-observed. One possible reason for the weaker-than-observed ISM arises from the warm bias, over the tropical oceans, especially over the equatorial western Indian Ocean, inherent in the model. This warm bias is not only confined to the surface layers, but also extends through most of the troposphere. As a result of this warm bias, the coupled model has too weak meridional tropospheric temperature gradient to drive a realistic monsoon circulation. This in turn leads to a weakening of the moisture gradient as well as the vertical shear of easterlies required for sustained northward propagation of rain band, resulting in weak monsoon circulation. It is also noted that the recently documented interaction between the interannual and intraseasonal variabilities of ISM through very long breaks (VLBs) is poor in the model. This seems to be related to the inability of the model in simulating the eastward propagating Madden–Julian oscillation during VLBs.