Exergy Analysis

This paper argues for a continuing exploration of Nature’s organizing principles that sustain prolonged homeostasis of the earth’s ecosystems punctuated by forceful transitions to new emergent states. Ecosystems develop and maintain a dynamically stable state by transacting energy and materials with the surrounding flows to keep reversing their continual fall to the ground state. Conversely, the elevation of any component of the ecosystem above the ground level may be regarded as a measure of its functional efficiency. This measure, called exergy, can be calculated for an eco-subsystem based on knowledge of the energy and material fluxes that thread it and, most importantly, of where the ground level happens to be. Admittedly, it is not straightforward to quantify these figures, and the departure of assumptions from reality will inevitably translate into errors in the calculated exergy figures. However, the variance may be estimated by analysing the results of an ensemble..

Attributing Vegetation Recovery During the Indian Summer Monsoon to Climate Drivers in Central India

Increasing droughts and heat waves as a result of global warming pose a major threat to forests and croplands in India. Monitoring the dynamics of vegetation during a drought and its recovery is essential for the Indian socio-economy and biodiversity. We investigate vegetation recovery from a stressed state in the pre-monsoon (May) period to the end of the monsoon period (September). We then attribute net change during the monsoon period to climate drivers such as temperature, precipitation, and soil moisture. To delineate non-linear interactions, we use an information-theoretic metric to understand the relative association of climate variables with vegetation productivity on a daily scale. We found that pre-monsoon vegetation stress is influenced by soil moisture (r = 0.8, p < 0.01), which is driven by variations in temperature and precipitation. During the monsoons, precipitation contributes to vegetation recovery from pre-monsoon stress through soil moisture recharge while inhibiting vegetation productivity by limiting the amount of radiation available for photosynthesis. Linear regression shows the significant negative dependence of vegetation recovery on precipitation (β = –0.7, p < 0.01) and positive dependence on soil moisture (β = 0.4, p < 0.1) indicating radiation limitation on photosynthesis..

Attributing Vegetation Recovery D uring the Indian Summer Monsoon to Climate Drivers in Central India

Increasing droughts and heat waves as a result of global warming pose a major threat to forests and croplands in India. Monitoring the dynamics of vegetation during a drought and its recovery is essential for the Indian socio-economy and biodiversity. We investigate vegetation recovery from a stressed state in the pre-monsoon (May) period to the end of the monsoon period (September). We then attribute net change during the monsoon period to climate drivers such as temperature, precipitation, and soil moisture. To delineate non-linear interactions, we use an information-theoretic metric to understand the relative association of climate variables with vegetation productivity on a daily scale. We found that pre-monsoon vegetation stress is influenced by soil moisture (r = 0.8, p 0.1). Mutual information showed the stronger, non-linear dependence of vegetation recovery on soil moisture than on precipitation, which is a contrasting result that highlights the importance of including non-linear measures in analyses of natural systems. Our results show that vegetation recovery in central India is driven by soil moisture during the Indian summer monsoon and is independent of pre-monsoon vegetation stress

Exergy Analysis: A Guide to Sustainability?

This paper argues for a continuing exploration of Nature’s organizing principles that sustain prolonged homeostasis of the earth’s ecosystems punctuated by forceful transitions to new emergent states. Ecosystems develop and maintain a dynamically stable state by transacting energy and materials with the surrounding flows to keep reversing their continual fall to the ground state. Conversely, the elevation of any component of the ecosystem above the ground level may be regarded as a measure of its functional efficiency. This measure, called exergy, can be calculated for an eco-subsystem based on knowledge of the energy and material fluxes that thread it and, most importantly, of where the ground level happens to be. Admittedly, it is not straightforward to quantify these figures, and the departure of assumptions from reality will inevitably translate into errors in the calculated exergy figures. However, the variance may be estimated by analysing the results of an ensemble of calculations with randomly perturbed input values. Even with these limitations, however, a map of exergy losses characterizing different parts of an ecosystem has the potential to reveal relative thermodynamic efficiencies for appropriate ameliorative interventions

Exergy Analysis: A Guide to Sustainability?

This paper argues for a continuing exploration of Nature’s organizing principles that sustain prolonged homeostasis of the earth’s ecosystems punctuated by forceful transitions to new emergent states. Ecosystems develop and maintain a dynamically stable state by transacting energy and materials with the surrounding flows to keep reversing their continual fall to the ground state. Conversely, the elevation of any component of the ecosystem above the ground level may be regarded as a measure of its functional efficiency. This measure, called exergy, can be calculated for an eco-subsystem based on knowledge of the energy and material fluxes that thread it and, most importantly, of where the ground level happens to be. Admittedly, it is not straightforward to quantify these figures, and the departure of assumptions from reality will inevitably translate into errors in the calculated exergy figures. However, the variance may be estimated by analysing the results of an ensemble of calculations with randomly perturbed input values. Even with these limitations, however, a map of exergy losses characterizing different parts of an ecosystem has the potential to reveal relative thermodynamic efficiencies for appropriate ameliorative interventions

River interlinking alters land-atmosphere feedback and changes the Indian summer monsoon

Abstract 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 delineation techniques, a coupled regional climate model, and multiple reanalysis datasets, and show that land-atmosphere feedbacks generate causal pathways between river basins in India. We further find that increased irrigation from the transferred water reduces mean rainfall in September by up to 12% in already water-stressed regions of India. We observe more drying in La Niña years compared to El Niño years. Reduced September precipitation can dry rivers post-monsoon, augmenting water stress across the country and rendering interlinking dysfunctional. Our findings highlight the need for model-guided impact assessment studies of large-scale hydrological projects across the globe