IISER Pune Digital Repository

A repository of scholarly research output from the Indian Institute of Science Education and Research (IISER) Pune.

Browse publications, theses, and other research output produced by the IISER Pune community.

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Theses submitted to IISER Pune in partial fulfilment of the requirements of the BS-MS dual degree, MSc. and Ph.D programmes. Also, project reports submitted by the students.

Recent Submissions

Access status: Embargo ,
On the dynamical organization of temperature variability over South Asia
(2026-10) SHAH, HARDIK; MONTEIRO, JOY; Dept. of Earth and Climate Science; 20203734
Temperature extremes are identified as threshold-defined events, but their intensity, persistence, and warm-cold asymmetry are governed by the dynamical processes that shape the tails of regional temperature distributions. This thesis develops a diagnostic framework for understanding temperature variability, using a South Asian pre-monsoon (March-June) heatwave hotspot. The analysis focuses on March-April, when near-surface temperature changes are strongly linked to resolved atmospheric advection. Lower-tropospheric dry static energy (DSE) advection over 600-900 hPa is used as a dynamical bridge between synoptic circulation and near-surface temperature variability. The thesis first establishes that lower-tropospheric DSE advection is closely related to daily near-surface temperature tendencies and is embedded within vertically coherent synoptic disturbances. The DSE-advection tendency is then decomposed into quasilinear and nonlinear Reynolds components. The tendency distribution is primarily organized by quasi-linear interactions between transient anomalies and the climatological background state, while the tails require nonlinear anomaly–anomaly interactions. Interpretable machine-learning techniques like decision-trees and regression help identify advective regimes associated with growth and decay of pre-existing lower-tropospheric DSE anomalies. The thesis next examines how nonlinear advection modifies the quasilinear tendency distribution and shapes skewness. Although nonlinear terms are strongly active in both tails, their components partly compensate across zonal, meridional, and vertical components. Weak skewness can therefore coexist with strong nonlinear tail activity. This shows that scalar distribution moments should be decomposed to yield dynamically important tail interactions. Finally, the thesis shows that cold and warm near-surface anomalies decay through structurally different pathways. Cold decay is associated with anomalous vertical motion acting on a lower-tropospheric DSE anomaly gradient, while low-level nonlinear horizontal advection helps maintain near-surface cold anomalies under relatively stable stratification. Warm decay exhibits weaker vertical contrast, low-level nonlinear horizontal advection that weakens the anomaly, and rapid thermodynamic adjustment. Together, these results show that regional temperature extremes are dynamically organized regions of a probability distribution, shaped by synoptic circulation, nonlinear advection, orographically modified transport pathways, and stability-modulated contrast between the lower and upper troposphere.
Access status: Open Access ,
Monthly Bulletin of New Publications - October 2026
(2026-10) Srinivasa Ramanujan Library
Access status: Metadata only ,
Integrating satellite remote sensing and deep learning for mapping glacier boundary and its changes in the Himalaya
(Elsevier B.V., 2027--01) Verma, Sarvesh Kumar; Vijay, Saurabh; BANERJEE, ARGHA; Dept. of Earth and Climate Science
Himalaya glaciers are changing rapidly, and therefore, need to be mapped with greater frequency. However, traditional mapping methods are challenging, especially over debris-covered areas and accumulation zones. These areas can easily be confused with bare rocks and perennial snow patches, respectively. In this study, we integrated glacier-dynamic variables, surface velocity and elevation change, along with multispectral data from Sentinel-2 and Landsat-8, InSAR coherence and backscatter from Sentinel-1, DEM derivatives, and multi-year minimum NDSI (perennial snowpatches) into five improved DL models (UNet++, M-LandsNet, GlacierNet-2, GlaViTU, and SAUNet) for delineating glaciers in the five basins of the Himalaya. We identified the most relevant layers that retain up to 80% of the information, reducing redundancy. This modified UNet++ achieved the highest mIoU of 0.92–0.98, surpassing the 18-layer input (mIoU = 0.84–0.94) in discriminating snow patches from small glaciers. The modified UNet++ model was applied to generate outlines of more than 500 glaciers in three epochs: 2010, 2019, and 2024. Lake-terminating glaciers retreated 2–3 times faster than land-terminating glaciers, with the highest frontal retreat rate observed in the Chhombo Chhu watershed (∼18–22 m yr−1), while debris-covered glaciers such as Gangotri showed lower rates (<10 m yr−1). This study highlights the importance of glacier dynamics as the input layer for detecting different types of glacier surfaces (e.g., debris, snow), discriminating between similar adjacent off-glacier surfaces, and delineating multi-temporal mountain glacier boundaries. This study shows the potential of integrating satellite data with deep learning methods to efficiently map mountain glaciers, which may be useful in investigating their response to the changing climate.
Access status: Metadata only ,
Congruences for the ratios of Rankin–Selberg L-functions
(Springer Nature, 2026-10) NARAYANAN, P.; Raghuram, A.; Dept. of Mathematics
A well-known principle states that a congruence between objects should give rise to a corresponding congruence between the special values of L-functions attached to these objects. We computationally investigate this principle for Rankin–Selberg L-functions attached to pairs of holomorphic cuspforms, and formulate a precise conjecture in general.
Access status: Metadata only ,
Reversible Oxidation of a Nonathia[42]Nonaphyrin(1.1.0.1.1.0.1.1.0) to a 40π Dication Diradicaloid
(American Chemical Society, 2026-10) PANCHMUKHI, NIKITA; UDAYA, HOSAHALLI S.; DESWAL, SWATI; SHUKLA, PRAGATI; ANAND, V. G.; Dept. of Chemistry
A one-pot condensation of bithiophene with thiophene diol under acidic conditions yields 28π, 42π, and 56π expanded porphyrinoids. X-ray crystallographic studies revealed a planar topology for both 28π and 42π macrocycles. Spectroscopic and quantum chemical calculations reveal weak ring current effects, while they undergo reversible two-electron ring oxidation as confirmed by electrochemical studies. Spectroscopic and quantum chemical calculations support a diradicaloid character for the 40π dicationic species.