Subimal Ghosh

• PhD
• Professor (Associate) at Indian Institute of Technology Bombay

The mountainous western coast of India, known as the Western Ghats, is considered to be a biodiversity hot spot, but it is under a constant threat due to human activities. The region is characterized by high orographic monsoon precipitation resulting in dense vegetation cover. Feedback of such a dense vegetation on the southwest monsoon rainfall is...

Climate change, urbanization, and anthropogenic activities have intensified rainfall and urban flooding, especially along coastlines. The high spatiotemporal variability and erratic pattern of rainfall highlight the incompetency of independent application of statistical forecasting techniques, especially over the tropics, and demand the incorporati...

Sundarbans in coastal South Asia, the largest contiguous mangrove forest in the world, face an intensifying compound stress of climate extremes and anthropogenically influenced water pollution. However, our knowledge about the responses of mangroves to these perturbations and their recovery mechanism is largely limited. We address this research gap...

Net Ecosystem Exchange (NEE) is crucial for understanding the carbon balance in ecosystems, indicating whether they act as carbon sinks or sources. While the impact of hydrometeorological factors on NEE at daily and monthly scales has been well‐researched, the significance of sub‐daily variability and the influence of memory in micrometeorological...

Forests play a pivotal role in regulating water and carbon cycles, yet their resilience to climate change remains unexplored for India—the world's second-largest contributor to global greening. Our study projects that global warming will drive the savannization of major Indian forests by the late 21st century. However, targeted human interventions...

Extreme precipitation events are projected to intensify with global warming, threatening ecosystems and amplifying flood risks. However, observation-based estimates of extreme precipitation-temperature (EP-T) sensitivities show systematic spatio-temporal variability, with predominantly negative sensitivities across warmer regions. Here, we attribut...

Evapotranspiration (ET) is one of the most important yet highly uncertain components of the water cycle. Available modeled ET products do not necessarily agree with each other at various spatiotemporal scales, either due to limitations on input data and/or due to model assumptions and simplifications. Therefore, using the water budget equation to e...

In evaluating the impacts of climate and urbanization on urban climates, a comprehensive understanding of surface energy balance at the local scale is imperative. However, such assessments for rapidly growing Indian cities have been hindered by limited studies on energy and water balance, primarily due to the absence of flux observations in urban r...

India has a growing water crisis fueled by global warming and a rising population. There is an urgent need for accurate water availability assessments and sustainable water management strategies for urban and rural areas. This can be achieved by developing novel decision-making tools for effective water resource management by improving the hydrolog...

The increase in water holding capacity of the atmosphere with temperature, given by the Clausius‐Clapeyron (CC) relationship, describes the changes in extreme rainfall intensities at warmer atmospheric states. We study the characteristics of extreme rainfall events (EREs) during the Indian summer monsoon season with respect to thermodynamic changes...

Emerging data-driven techniques, such as Complex Networks (CNs), can identify spatial linkages between droughts on a global scale and can improve early warning systems. Recent studies used CNs to identify hotspots of global drought teleconnections as land drought hubs; however, these studies excluded the ocean regions in CN, an oversight that can u...

India has observed increasingly persistent heat extremes in recent decades, that pose environmental, agricultural, and human health challenges. North-Central India, a highly populated region prone to heatwaves, has experienced record maximum temperatures (>48°C) during the pre-monsoon season. While studies have shown positive trends in heatwaves du...

India is the second-highest contributor to the post-2000 global greening. However, with satellite data, here we show that this 18.51% increase in Leaf Area Index (LAI) during 2001–2019 fails to translate into increased carbon uptake due to warming constraints. Our analysis further shows 6.19% decrease in Net Primary Productivity (NPP) during 2001–2...

Concurrent extreme rainfall events, or synchronous extremes, during Indian Summer Monsoon Rainfall (ISMR), cause significant damage, but their spatiotemporal evolution remains unclear. Using the event synchronization approach to examine the synchronicity of extreme rainfall events from 1901 to 2019, we find that Central India consistently hosts str...

Plain Language Summary In the wake of the continuing threat of urban flooding following landfalling hurricanes, understanding the possible interplay between the urban landscape and hurricane rainfall is an emerging research area. Prior studies have shown that the micro‐climate of the urban regions can modify rain over the city centers and periphery...

Groundwater depletion due to agricultural intensification is a major threat to water and food security in the Indo-Gangetic Plain (IGP), a critical food bowl, home to 400 million people and currently producing 135 million metric tonnes of cereals. Among the solutions proposed to address this unsustainable water consumption, crop switching has recei...

Massive river interlinking projects are proposed to offset observed increasing droughts and floods in India, the most populated country in the world. These projects involve water transfer from surplus to deficit river basins through reservoirs and canals without an in-depth understanding of the hydro-meteorological consequences. Here, we use causal...

The monsoons in Pakistan have been exceptionally harsh in recent decades, resulting in extraordinary drought conditions and record flooding events. The changing characteristics of extreme events are widely attributed to climate change. However, given this region’s long history of floods and droughts, the role of natural climate variability cannot b...

A novel flood risk forecasting‐based response priority framework is proposed in this study, which will facilitate efficient decision‐making ahead of an extreme precipitation event. This study is demonstrated over a highly flood‐prone and geomorphologically diverse coastal catchment in Mumbai city, the financial capital of India, and is subjected to...

Emerging data-driven techniques, such as Complex Networks (CNs), can identify spatial linkages between droughts on a global scale and, subsequently, drought propagation, which can improve early warning systems. Recent studies used CNs to identify hotspots of global drought teleconnections as land drought hubs; however, these studies excluded the oc...

Mumbai, a densely populated city, experiences frequent extreme rainfall events leading to floods and waterlogging. However, the lack of real-time flood monitoring and detailed past flooding data limits the scientific analysis to extreme rainfall assessment. To address this, we explore the usability of crowdsourced data for identifying flood hotspot...

Many global climate models, including the Climate Forecast System version 2 (CFSv2), have a biased representation of subseasonal modes of variability of the Indian summer monsoon. For instance, they simulate a weaker summer mean monsoon low‐pressure systems (LPS) climatology, faster than observed northward propagation of monsoon intraseasonal oscil...

Higher warming will affect more regions globally with intensified agricultural and ecological droughts. Higher CO2 concentration improves vegetation's water use efficiency (WUE), but its potential to alleviate extreme agricultural and ecological droughts is unclear. India is the second-highest contributor to global greening, having two of the eight...

Higher CO2 concentration improves vegetation's water use efficiency by CO2 fertilization effects. However, anthropogenic climate change increases temperature and thus atmospheric water demand and Evapotranspiration globally, which may cause more intense frequent agricultural and ecological droughts. India is an agriculture-dependent country, with m...

The Bay of Bengal (BoB) receives a large amount of freshwater from rains and rivers, resulting in large upper-ocean stratification due to the freshening effect. This salinity stratification has been theorized to impact sea-surface temperature (SST) and convection on intra-seasonal time scales by affecting the ocean mixed layer and the barrier layer...

Sundarbans in the coastal South Asia, the largest contiguous mangrove forest in the world, faces an intensifying compound stress of climate extremes and anthropogenically influenced water pollution. However, our knowledge about the responses of mangroves to these stressors with the recovery mechanism is largely limited. We address this research gap...

The monsoons in Pakistan have been exceptionally harsh in recent decades, resulting in extraordinary drought conditions and record flooding events. The changing frequency of extreme events is widely attributed to climate change. However, given this region's long history of floods and droughts, the role of natural climate variability cannot be rejec...

Indian Summer Monsoon Rainfall (ISMR) is one of the most well-documented areas of hydrometeorology; however, the processes associated with ISMR are not well understood. This attributes to the complexities associated with ISMR at multiple spatio-temporal scales. This further results in inconsistencies across the literature to assess the impacts of g...

The enormous progress in weather and extended range predictions for the Indian monsoon over the last decade has not been translated to operationalized irrigation water management tools despite many agricultural advisories from operational agencies. The limited implementation is mainly due to the resolution mismatches of forecasts and decision-needs...

India receives more than 70% of its annual rainfall in the summer monsoon from June to September. The rainfall is scanty and scattered for the rest of the year. Combining satellite data and model simulations, we show that the soil-vegetation continuum works as a natural capacitor of water, storing the monsoon pulse and releasing the moisture to the...

Increased irrigation due to agricultural intensification has profound impacts on the surface water and energy balance at regional to local scales. Recent updates of the state‐of‐the‐art Land Surface Models (LSMs) include the impacts of irrigation on surface hydrology. The Indo‐Gangetic Plain (IGP) is one of the global hotspots of irrigation water a...

Soil moisture (SM) deficit and atmospheric aridity pose a significant threat to agricultural and ecological services. These two events co-occur and affect vegetation with different underlying mechanisms. SM affects the carbon cycle through its vital role in vegetation growth. Fluctuation in SM supply can affect the physiological functions of vegeta...

India is the second-highest contributor to the post-2000 global greening. With satellite data, here we show that this 18.51% increase in Leaf Area Index (LAI) during 2001-2019 fails to translate into increased carbon uptake due to warming constraints. Our analysis further shows 6.19% decrease in Net Primary Productivity (NPP) during 2001-2019 over...

Continuous remote-sensed daily fields of ocean color now span over two decades; however, it still remains a challenge to examine the ocean ecosystem processes, e.g., phenology, at temporal frequencies of less than a month. This is due to the presence of significantly large gaps in satellite data caused by clouds, sun-glint, and hardware failure; th...

Massive river interlinking projects are proposed to offset observed increasing trends of extremes, such as droughts and floods in India, the second highest populated country.These river interlinking projects involve water transfer from surplus to deficit river basins through reservoirs and canals, but without an in-depth understanding of the hydro-...

Limited surface observations of turbulent heat fluxes result in incomplete knowledge about the surface energy balance that drives the climate system. Here, we developed a novel, purely physics-based analytical method grounded on the thermodynamic principle of maximum power. The approach derives the turbulent heat flux only from the four inputs of i...

Causal and attribution studies are essential for earth scientific discoveries and critical for informing climate, ecology, and water policies. However, the current generation of methods needs to keep pace with the complexity of scientific and stakeholder challenges and data availability combined with the adequacy of data-driven methods. Unless care...

Indian river basins are intensively managed with country-specific agricultural practices of cultivating submerged paddy and uncontrolled groundwater irrigation. Numerical experiments with the state-of-the-art land surface models, such as Variable Infiltration Capacity (VIC), without incorporating region-specific practices, could be misleading. Here...

Increased occurrence of heatwaves across different parts of the world is one of the characteristic signatures of anthropogenic warming. With a 1.3 billion population, India is one of the hot spots that experience deadly heatwaves during May-June – yet the large-scale physical mechanism and teleconnection patterns driving such events remain poorly u...

Climate models predict an intensification of precipitation extremes as a result of a warmer and moister atmosphere at the rate of 7 % K-1. However, observations in tropical regions show contrastingly negative precipitation–temperature scaling at temperatures above 23–25 ∘C. We use observations from India and show that this negative scaling can be e...

The variations of the atmospheric Carbon uptake by vegetation over India, the second-highest global greening contributor, have enormous climate change mitigation implications. Global studies conclude that Temperature and Total Water Storage (TWS) cause interannual variations of carbon uptake based on the correlation coefficient, which is not a caus...

A robust understanding of the sub-seasonal cold season (November–March) precipitation variability over the High Mountains of Asia (HMA) is lacking. Here, we identify dynamic and thermodynamic pathways through which natural modes of climate variability establish their teleconnections over the HMA. First, we identify evaporative sources that contribu...

The Extended Range Predictions (ERP) provide Sub-seasonal to Seasonal (S2S) prediction of meteorological variables at a lead time of multiple weeks. Despite the considerable improvements in the ERP system, their applications in real-time irrigation water management are limited. Such limited use of ERP is due to uncertainty in predictions and a spat...

Quantifying flood hazards by employing hydraulic/hydrodynamic models for flood risk mapping is a widely implemented non-structural flood management strategy. However, the unavailability of multi-domain and multi-dimensional input data and expensive computational resources limit its application in resource-constrained regions. The fifth and sixth IP...

Hot extremes are anticipated to be more frequent and more intense under climate change, making the Indo-Gangetic Plain of India, with a 400 million population, vulnerable to heat stress. Recent studies suggest that irrigation has significant cooling and moistening effects over this region. While large-scale irrigation is prevalent in the Indo-Gange...

Rivers form an essential component of the earth system, with ~36,000 km3 of riverine freshwater being dumped into the global oceans every year. The role of rivers in controlling the sea-surface salinity and ensuing air-sea interactions in the Bay of Bengal (BoB) is well-known from observational studies; however, attempts to include rivers in couple...

Climate models predict an intensification of precipitation extremes as a result of a warmer and moister atmosphere at the rate of 7 %/K. However, observations in tropical regions show contrastingly negative precipitation-temperature scaling at temperatures above 23°–25 °C. We use observations from India and show that this negative scaling can be ex...

A robust understanding of the sub-seasonal cold season (November–March) precipitation variability over the High Mountains of Asia (HMA) is currently lacking. Here, we identify dynamic and thermodynamic pathways through which natural modes of climate variability establish their teleconnections over the HMA. First, we identify evaporative sources tha...

Globally increasing intensity and frequency of extreme rainfall events demand reliable early warning systems. Despite significant improvements in the skills of weather models, the state-of-art extreme rainfall forecasts, at a sufficient lead time, still suffer from high biases, high uncertainties, low hit rates, and high false alarms. Bias correcti...

The Surface Water and Ocean Topography (SWOT) mission, which is scheduled to launch in 2022, would offer India with unprecedented hydrologic applications. This study presents the preliminary results of the CNES Large- Scale SWOT Hydrology Simulator to illustrate how SWOT data can be used to monitor reservoir water levels. Except for some factors su...

Floods are the most frequently occurring natural hazard in Canada. An in-depth understanding of flood seasonality and its drivers at a national scale is essential. Here, a circular, statistics-based approach is implemented to understand the seasonality of annual-maximum (AM) floods (streamflow) and to identify their responsible drivers across Canad...

Continuous remote-sensed daily fields of ocean color now span over two decades; however, it still remains a challenge to examine the ocean ecosystem processes, e.g., phenology, at temporal frequencies of less than a month. This is due to the presence of significantly large gaps in satellite data caused by clouds, sun-glint, and hardware failure; th...

Continuous remote-sensed daily fields of ocean color now span over two decades; however, it still remains a challenge to examine the ocean ecosystem processes, e.g., phenology, at temporal frequencies of less than a month. This is due to the presence of significantly large gaps in satellite data caused by clouds, sun-glint, and hardware failure; th...

This chapter assesses changes in weather and climate extremes on regional and global scales, including observed changes and their attribution, as well as projected changes. The extremes considered include temperature extremes, heavy precipitation and pluvial floods, river floods, droughts, storms (including tropical cyclones), as well as compound e...

Green Roofs (GRs) are one of the measures considered for Urban Heat Island (UHI) mitigation. The cooling effects of GRs are well studied in the literature. However, previous work has not addressed the impacts of GRs on heavy rainfall in cities. This study develops and tests the hypothesis that incorporating green roofs in urban areas enhances the m...

Decadal predictions have gained immense importance over the last decade because of their use in near-term adaption planning. Computationally expensive coupled model intercomparison project phase 5 general circulation models (GCMs) are initialized every 5 years and they generate the decadal hindcasts with moderate skill. Here we test the hypothesis...

Despite the remarkable improvements in skillful weather forecasts, their uses in irrigation water management at a farm scale are still limited. This is attributable to the scale mismatch between weather and hydrologic models as well complexities in farmscale ecohydrological processes. Here, we have developed a simulation-optimization algorithm for...

Interannual variations of Indian summer monsoon rainfall (ISMR) are modulated by external forcings such as El Niño Southern Oscillation, Indian Ocean Dipole, and the Atlantic Niño. Vegetation over land responds to variations in ISMR, but the feedback from vegetation to ISMR variability has not been fully explored yet. To address this gap, we perfor...

Reliable forecasting of heavy convective rainfall events continues to be one of the greatest challenges for numerical weather prediction models. Studies across the globe have indicated that Doppler weather radar (DWR) data assimilation through three‐dimensional variational methods (3D‐Var) has a considerable impact on improving the forecast skill o...

The evacuation of the population from flood-affected regions is a non-structural measure to mitigate flood hazards. Shelters used for this purpose usually accommodate a large number of flood evacuees for a temporary period. Floods during a pandemic result in a compound hazard. Evacuations under such situations are difficult to plan as social distan...

The establishment and maintenance of an exhaustive hydrometeorological network are challenging tasks in densely populated coastal cities having erratic rainfall patterns. The current study proposes a robust statistical framework to rationalize an existing Automatic Weather Station (AWS) network which monitors multiple hydrometeorological observatio...

Assessment of the response of the Himalayan river flows to climate change is complex due to multiple contributors: rainfall, snowmelt, and glacier‐melt. The number of studies is limited in this direction due to lack of data availability as well as non‐availability of models considering all the above‐mentioned components. As for example, the state‐o...

The dynamics of interactions between the environmental and the meteorological variables in an urban region is extremely complex due to continuously evolving coupled human-natural processes in an urban setting. We attempt to understand the same with the networks of variables using information theory, known as process network. We monitored local mete...

In 2020, we are in the doorstep of a new decade, during which the UN Sustainable Development Goals (SDG) are to be achieved, collectively as one nation and one human-hood, where availability of safe, sustainable and clean water and air forms the core of multiple goals. However, the emergence of the COVID-19 pandemic across the globe has resulted a...

Forecast of the Indian summer monsoon on an extended range (beyond the conventional one-week lead time) is critical for an agronomic economy like India. Although dynamic models have been quite successful in capturing and representing monsoon circulation, they fail to sustain this skill beyond the standard weather time scale (7–10 days). As such, th...

In this study, the impacts of land use/land cover (LULC) and climate change on the streamflow and sediment yield were investigated for the Payaswani River Basin, Western Ghats, India. The LULC was determined using Landsat images, and climate data were procured from five general circulation models for representative concentration pathway (RCP) 4.5 (...

Non-structural mitigation measures to the globally increasing flood events include forecast based alert generation. However, the extreme rainfall forecasts are associated with low hit rate, high false alarm, and spatiotemporal bias; which makes it difficult to rely on them. Further, the losses due to flood in a region not only depend on rainfall se...

The evacuation of the population from flood-affected regions is a non-structural measure to mitigate flood hazards. Shelters used for this purpose usually accommodate a large number of flood evacuees for a temporary period. Floods during pandemic result in a compound hazard. Evacuations under such situations are difficult to plan as social distanci...

Topographic data in the form of digital elevation models (DEMs) play a significant role in flood management. Despite the increasing availability of DEMs for large regions, there is a need to evaluate their performance at the inundation/flood level, while considering the overall complexity of flood models. The present study identifies, for the first...

Plain Language Summary Clausius‐Clapeyron (CC) equation suggests a rise in atmospheric moisture‐holding capacity by 6–7%/°C. Extreme precipitation events are expected to intensify in response to increased warming, at a similar rate. However, observational evidences show large spatiotemporal variability in the extreme precipitation scaling with sign...

Crop loss and ensuing social crises can be detrimental for the agriculture-driven economy of India. Though some studies identify country-wide increasing temperatures as the dominant factor for crop loss, the agro-climatic diversity within the country necessitates an understanding of the influence of climate variability on yields at regional scales....

In this study, the impacts of changes in land use/ land cover (LULC) and climate on surface runoff are investigated in the Kadalundi river basin, Western Ghats, India. Land Change Modeller (LCM) was applied to project the future LULC scenarios in 2030 and 2050. Climate change scenarios of the future time period of near (2011−2040), mid (2041−2070),...

Plain Language Summary Flooding in the Western Himalayan rivers has caused colossal loss of life and property in the recent decades. We present a first analysis of changing patterns of observed peak streamflow in Western Himalayan rivers at multiple locations, using high‐quality in situ data. With a high degree of confidence, we conclude that the o...

The Himalayan ecosystem is a global biodiversity hotspot and a vital component of the global water cycle. However, the studies characterizing the ecohydrological processes of the Himalayas are still limited. Looking at a system as a network, having nonlinear couplings, can give us better insights into its dynamics. Here, using an information-theore...

This study investigated the impacts of changes in land cover and climate on runoff and sediment yield in a river basin in India. Land Change Modeler was used to derive the future land cover and its changes using the Sankey diagram approach. The future climatic parameters were derived from five general circulation models for two emission scenarios w...

Anthropogenic changes are likely to intensify rainfall extremes, posing a risk to human, environmental and urban systems. Understanding the impact of urbanization on rainfall extremes is critical for both reliable climate projections as well as sustainable urban development. This study presents the unexplored impacts of changes arising in urban are...

Regional water resources modelling is important for evaluating system performance by analyzing the reliability, resilience and vulnerability criteria of the system. In water resource systems modelling, several uncertainties abound, including data inadequacy and errors, modeling inaccuracy, lack of knowledge, imprecision, inexactness, randomness of...