nasa-gesdisc/es-publications-researchareas huggingface dataset:
Two decades of nighttime surface urban heat island intensity analysis over nine major populated cities of India and implications for heat stress (2023)

Warmer global climate and urban heat islands (UHIs) interact, by exacerbating heatwaves and increasing the extreme heat days in cities. The implications of added heat stress in urban environments due to intensifying surface UHIs (SUHIs) is of utmost concern. Seasonal, annual and decadal nighttime SUHI intensities (SUHIIs), from 2001 to 2020, for nine major populated cities of India are analyzed. This includes five megacities- Delhi, Mumbai, Kolkata, Bangalore, and Chennai, and four incipient megacities- Hyderabad, Ahmedabad, Surat, and Pune. The key role of increasing urbanization (pre- and post-2010) in expansion and intensification of nighttime SUHIs in India is highlighted. For all cities either pre-monsoon (MAM) or winter (December-February; DJF) seasons show the strongest SUHII development. During the 20012010, and the 20112020 decade, a nighttime SUHII maxima of respectively (i) 2.1C and 2.5C for Delhi, (ii) 1.3C and 1.5C for Mumbai, (iii) 1.3C and 1.5C for Kolkata, (iv) 0.6C and 1.0C Bangalore, (v) 1.7C and 1.9C for Chennai, (vi) 1.8C and 2.3C for Hyderabad, (vii) 2.8C and 3.1C for Ahmedabad, (viii) 1.9C and 2.4C for Surat, and (ix) 0.8C and 1.3C for Pune is noted. Further, all incipient megacities showed a mean annual growth rate of nighttime SUHII of over 0.007C/year, substantially greater than in the megacities. High SUHII magnitudes, greater growth rates of SUHII, and huge populations, severely compounds the vulnerability of Indian cities to excessive heat exposure risk, especially during MAM heatwaves. Lastly, the implications of nighttime SUHII findings from the present study, on the increase in heat stress, the loss of labor productivity and the rise in heat-related mortality rate is emphasized. The study recommends implementation of city-specific action plans to mitigate the heat stressed urban environment. Targeted use of cooling strategies in localized hotspots within the urban areas where high intensity SUHIs are likely to form is also suggested.

Research areas: Heat
Spatio-temporal evolution of surface urban heat island over (2023)

India is one of the rapidly urbanizing major economies in the developing world. As it embarks on its urban transition, many small tier-2 cities are already experiencing a large-scale transformation. This study examines the effects of surface urban heat island intensity (SUHI) effect from 2001 to 2020 on a tropical coastal urban complex, Bhubaneswar and Cuttack, a rapidly expanding tier-2 twin city in the Eastern Indian region. Our study reveals a clear discernible annual nighttime SUHI for both Bhubaneswar and Cuttack (0.75  0.08 and 1.22  0.07 C) with a growth rate of 0.18  0.07 and 0.13  0.07 C/decade, respectively. Surprisingly, the annual daytime SUHI is weakening for Bhubaneswar. Both night and daytime SUHI showed substantial seasonality with a clear asymmetry during the day and night. Daytime urban cool island effect was observed for Cuttack with Bhubaneswar reporting weak SUHI for daytime during dry seasons. Around the periphery of the cities, the diurnal temperature range (DTR) was found to be the highest. Furthermore, A decrease of 2 C in the DTR has been reported over the past two decades. The urbanization effect on the local thermal climate of both cities is seen beyond the physical urban limits. Such changes, even in tier-2 cities, have significant potential to modulate local climate and underscore the need for detailed studies in the rapidly urbanizing cities of India and the world to enable disaster resilience, climate-proofing, and sustainability.

Research areas: Heat
Modeling the intensity of surface urban heat island based on the (2023)

The urban heat island (UHI) effect is anticipated to be intensified and cause severe damage to human society under future urbanization and climate change. Due to the complicated human-nature interactions in the urban domain, it is challenging to characterize the intensity of UHI quantitatively, especially at the global scale. Here, we proposed a framework to estimate the surface urban heat island intensity (SUHII) based on satellite-derived land surface temperature (LST) and the derived impervious surface area (ISA) data across 355 cities worldwide from 2003 to 2018. First, we employed linear regression models to estimate LST using ISA as the explanatory variable, given that the LST generally elevated with increasing urban intensity along the urban-rural gradient. Then, using the modeled LST, we estimated the spatiotemporal patterns of SUHII worldwide. The established linear regression models with ISA as the explanatory variable perform reasonably well in estimating LST for both daytime and nighttime, with average RMSEs of 1.40 and 0.80 C, respectively. The resulting SUHII reasonably captures the spatial heterogeneity across cities in the world, with the highest value in the tropical region at daytime and in the arid region at nighttime. The estimated and observed SUHII show good agreement with average R2 values of 0.81 and 0.72 for daytime and nighttime, respectively. Using ISA as an indicator for LST estimation, this study first implemented a comprehensive estimation of SUHII at the global scale. The proposed methodology is of great potential to project future SUHII by expanding urban impervious surfaces under diverse scenarios jointly determined by shared socioeconomic pathways and climate change scenarios.

Research areas: Heat
Differences in urban heat island and its driving factors between central (2023)

Urban heat island (UHI) is one of the important effects of urbanization on built environment. Land surface temperature data was taken from moderate-resolution imaging spectroradiometer (MODIS) to investigate the long-term spatiotemporal patterns of UHI in Wuhan during 2001~2018 and, the UHI intensity changes of built-up land in 13 administrative regions in Wuhan were analyzed. Furthermore, 34 spatial error models and 34 ordinary least squares models were established and compared. Spatial error models showed good fitting effect, which were used to determine the influence of normalized difference vegetation index (NDVI), normalized difference building index (NDBI), and socialeconomic factors (population and nighttime light) on UHI intensity in central urban area and new urban area. The explanatory power changes of these four indicators during 2001~2018 were explored as well. The average UHI intensity in 2014~2018 has increased by about 0.45 C compared to that in 2001~2005. NDBI is the most dominant factor contributing to the increase in temperature. The impact of NDVI on UHI intensity changes from negative to positive, and the impact of NDBI on UHI intensity in central urban area is weakened during 20012018. Socialeconomic factors have a greater impact on new urban area than on central urban area. These findings show the effects and the explanatory power changes of driving factors during 18 years, which can provide a better understanding of the formation and development of UHI and support for the future urban planning of Wuhan.

Research areas: Heat
Anthropogenic heat variation during the COVID-19 pandemic control (2023)

Anthropogenic heat (AH) is an important input for the urban thermal environment. While reduction in AH during the Coronavirus disease 2019 (COVID-19) pandemic may have weakened urban heat islands (UHI), quantitative assessments on this are lacking. Here, a new AH estimation method based on a remote sensing surface energy balance (RS-SEB) without hysteresis from heat storage was proposed to clarify the effects of COVID-19 control measures on AH. To weaken the impact of shadows, a simple and novel calibration method was developed to estimate the SEB in multiple regions and periods. To overcome the hysteresis of AH caused by heat storage, RS-SEB was combined with an inventory-based model and thermal stability analysis framework. The resulting AH was consistent with the latest global AH dataset and had a much higher spatial resolution, providing objective and refined features of human activities during the pandemic. Our study of four Chinese megacities (Wuhan, Shanghai, Beijing, and Guangzhou) indicated that COVID-19 control measures severely restricted human activities and notably reduced AH. The reduction was up to 50% in Wuhan during the lockdown in February 2020 and gradually decreased after the lockdown was eased in April 2020, similar to that in Shanghai during the Level 1 pandemic response. In contrast, AH was less reduced in Guangzhou during the same period and increased in Beijing owing to extended central heating use in winter. AH decreased more in urban centers and the change in AH varied in terms of urban land use between cities and periods. Although UHI changes during the COVID-19 pandemic cannot be entirely attributed to AH changes, the considerable reduction in AH is an important feature accompanying the weakening of the UHI.

Research areas: Heat
One-Year Monitoring of a Ground Heat Exchanger Using the In Situ Thermal (2022)

The use of renewable energies, and of geothermal energy in particular, is increasingly being applied in Germany and Europe for the development of new residential districts. The use of geothermal borehole heat exchangers (BHE), in combination with ground-source heat pumps (GSHP), represents an important part of shallow geothermal systems, which are used, among other systems, in urban areas due to their small space requirements. Over the course of planning BHE systems, performance must be determined via the parameters of thermal conductivity, thermal capacity, undisturbed ground temperature, and borehole thermal resistance. These can be identified by the experimental approach known as thermal response testing (TRT). The thermal parameters change due to the influences of the seasonal temperature fluctuations that take place in the ground. In this paper, a pilot double-U BHE heat exchanger field with a depth of 120 m was investigated from this perspective. TRT was carried out using monthly measurements taken over the period of one year using an electrically powered mobile TRT device. The evaluation of the individual tests was carried out using the line-source, moving-line-source, and cylinder-source theories. Our results show that the season in which TRT was implemented had an influence on the determined thermal parameters, with better thermal conditions being obtained in winter months. This is especially visible for thermal conductivity, with monthly deviations of 0.1 W/(mK), independent of the evaluation approaches used.

Research areas: Energy Production/Use
Recent urbanization increases exposure to humid-heat extreme events over populated regions of China (2023)

Extreme-heat research has largely focused on dry heat, while humid heat, which presents a major societal impact, especially on human health, remains relatively understudied. Previous studies have revealed that a wet-bulb temperature (TW) of 35 C marks our upper physiological limit, and much lower values also have serious health impacts. Our evaluations from observations showed that the daily maximum TW values over China have been scarcely reported above 35 C, but humid-heat extreme days of TW above 30 C have been reported each year during the past four decades, being mainly centered over the highly populated regions, including East China, South China, and the Sichuan basin. Further analyses indicated that the recent rapid urbanization process in China has amplified the societal impacts of humid-heat extremes, and land exposure to humid heat over urban regions is expected to increase at a faster rate than other regions of China. This suggests increasing risks of humid-heat extremes on human health in big cities of densely populated regions due to rapid urbanization. As indicated here, the population of China has become increasingly exposed to such extremes, with a strong increasing tendency of about 3100 persons per day per year since 2000.

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Research areas: Heat
Geospatial and statistical analysis of urban heat islands and thermally vulnerable zones in Bangalore and Hyderabad cities in India (2023)

Urban Heat Island (UHI) effects caused by urbanization and associated anthropogenic activities have adverse environmental and social impacts. The social impacts of UHIs on Indian cities are not well documented. To fill this void, the current paper examines the spatial variation of the UHI effects on the populations of two Indian cities: Bangalore and Hyderabad. Land Surface Temperature (LST) data for the past two decades is obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor to analyse the spatial and temporal variation of the thermal environment of the cities. The regions experiencing different levels of UHI effects within the cities, along with the population in these zones, are identified in the study. The average UHI intensity for the past two decades in Bangalore and Hyderabad is found to be 1.9 C and 2.44 C, respectively. The UHI intensity in Bangalore and Hyderabad is found to be increasing annually at a rate of 0.040 C per year and 0.033 C per year, respectively. Around 1 million people in Bangalore and 1.8 million people in Hyderabad are inhabitants of the high temperate zone, experiencing an average LST of 3.14 C and 3.55 C higher than the rest of the population, respectively. The study emphasizes the need for regionally scaled UHI mitigation strategies and identifies the most vulnerable regions within the study area to prioritize mitigation strategies.

Research areas: Heat
Intensive and extensive margins of mining and development: Evidence from Sub-Saharan Africa (2019)

What are the economic consequences of mining in Sub-Saharan Africa? Using a panel of 3,635 districts from 42 Sub-Saharan African countries for the period 1992 to 2012 we investigate the effects of mining on living standards (measured by night-lights and household/cohort characteristics from Demographic and Health Surveys) and public service provisions (from Afrobarometer). Night-lights increase in mining districts when mineral production expands (intensive margin), but large effects are mainly associated with new discoveries and new production (extensive margin). We identify the effect by carefully choosing feasible but not yet mined districts as a control group. In addition, we exploit first, single-first, giant and major discoveries as exogenous news shocks. Mines in Africa exhibit enclave characteristics as we find little evidence of significant spillovers to other districts.

Research areas: Energy Production/Use
MCDM and GIS based modelling technique for assessment of solar and wind farm locations in India (2021)

In the recent past, various factors have led to an increase in the use of renewable energy sources, among which, the depleting fossil fuel reserves, increasing fuel prices, and rising environmental concerns are the most prominent. With this increasing reliance on renewable energy sources, a proper assessment of the suitable sites becomes necessary for the optimum utilization of these resources. The present study investigates the spatial suitability of the solar and wind farms locations in India based on the technical, economic, and socio-environmental perspectives. The analysis is performed with the coupled use of the Geographical Information System (GIS) and Multi-Criteria Decision Making (MCDM) approaches. Analysis of present research work shows that 4.13% of the study area (133,874 km2) is highly suitable for the deployment of solar plants while 0.91% of the total area (29,457 km2) is highly suitable for the wind farms. The study further concludes that the Rajasthan state in India has the highest suitable land for the installation of solar plants (20,881 km2) as well as wind farms (6323 km2). The proposed model can be used for the development of policies related to renewable energy resources and the assessment of suitability of already sanctioned projects.

Research areas: Energy Production/Use
Making use of the complementarity of hydropower and variable renewable energy in Latin America: A probabilistic analysis (2022)

Latin America is one of the regions most vulnerable to the effects of climate variability on hydropower generation. Hydropower is the backbone of the Latin-American power system and a key technology for ensuring low-carbon power generation in the region. Despite its importance, our understanding of the impact and likelihood of seasonal variability and of long-term phenomena such as the El Nino Southern Oscillation (ENSO) on hydropower is limited. There is an essential need to understand how likely these effects are and to identify measures to counterbalance them. A combination of wind, solar, and hydropower offers the potential to mitigate the impact of climate variability on renewable power generation and thus improve its reliability. Here we present a modeling framework to quantify the potential benefits of such combination. The modeling framework relies on a meteorological reanalysis dataset, large-scale renewable power generation models, and statistic models. We consider the countries with the largest hydropower capacity in the region, namely Argentina, Brazil, Colombia, Mexico, and Venezuela. We examine whether the probability of a production deficit is reduced when all renewable resources are combined compared to a scenario based solely on hydropower, especially during droughts. The approach presented allows for the first time an in-depth analysis of the benefits of a combined wind, solar, and hydropower-based power generation under different geographical conditions in altered ENSO phases. Our results suggest thatdepending on the country and the percentilethe hydropower generated during drought ENSO phases could be up to 50% lower than that during neutral phases. The countries most affected are Colombia and Venezuela, while the reduction is somewhat less severe in Argentina, Brazil, and Mexico. Combining hydropower with variable renewable energy (VRE) offers the potential to reduce the risk of a power deficit during the 10th percentile of the driest months of the year, both in drought and neutral phases. Argentina is the country with the most effective combination of resources to mitigate a power deficit, as each MW of installed VRE generates 0.218 GWh of additional power. It is followed by Brazil and Mexico with 0.185 GWh per MW of VRE and by Venezuela and Colombia with 0.1280.098 GWh/MW of VRE, respectively. These results can contribute to informing future decisions on capacity planning and regional transmission grids.

Research areas: Energy Production/Use
Simulating the cumulative effects of potential open-pit mining and climate change on streamflow and water quality in a mountainous watershed (2022)

Land use and climate change effects on water quality and water quantity are well documented globally. Most studies evaluate individual factors and effects, without considering the interrelationships between land use, climate, water quality, and water quantity. This study provides an integrated assessment of the cumulative effects of climate change and potential open-pit coal mining on streamflow and water quality in the Oldman River Basin, Alberta, Canada. A hydrological model was developed that incorporates estimates of future selenium loading, water use, and projected changes in air temperature and precipitation to evaluate changes in water quantity and quality. Model results indicate that estimated selenium concentrations, absent any attenuation, are likely to be substantially above most water quality guidelines and strong reliance on mitigation technologies would be required to maintain adequate water quality in the watershed if mine development were to take place. Streamflow is sensitive to changes in climatic conditions, and modelling results suggest there are likely to be increases in winter flow, earlier peak flow, and reductions in flow during the summer and fall months under the climate change scenarios. These changes can have direct impacts on the degree of selenium dilution and more generally on aquatic habitat, ecosystem health, and socioeconomic needs. This study highlights that water management decisions may mis-evaluate the risks and tradeoffs of future mine development if they fail to adequately consider climate change and changing streamflow regimes and their indirect effects on water quality.

Research areas: Energy Production/Use
The impact of climatic extreme events on the feasibility of fully renewable power systems: A case study for Sweden (2019)

Long term time series of variable renewable energy (VRE) generation and electricity demand (load) provide important insights into the feasibility of fully renewable power systems. The coverage of energy statistics is usually too short or the temporal resolution too low to study effects related to interannual variability or the impact of climatic extreme events. We use time series simulated from climate data to assess the frequency, duration, and magnitude of extreme residual load events of two fully renewable power scenarios with a share of VRE generation (wind and solar PV) of about 50% for the case of Sweden. We define residual load as load  wind  PV  nuclear generation. Extreme residual load events are events that exceed the balancing or ramping capacities of the current power system. For our analysis, we use 29 years of simulated river runoff and wind and PV generation. Hourly load is derived from MERRA reanalysis temperature data by applying statistical models. Those time series are used along with historic capacity and ramping restrictions of hydro and thermal power plants in an optimization model to minimize extreme residual load events. Our analysis shows that even highly flexible power systems, as the Swedish one, are affected by climatic extreme events if they increase their VRE shares. Replacing current nuclear power capacities by wind power results on average in three extreme residual load events per year that exceed the current power system's flexibility. Additional PV generation capacities instead of wind increase the number of extreme residual load events by about 4%, as most events occur during the winter month when solar generation is close to zero and thus not able to counterbalance low wind events. Contrarily, overproduction and the need to curtail VRE generation become more pressing with higher shares of PV. In the discussion we highlight measures that could provide additional balancing capabilities to cope with the more frequent and severe residual load events in a fully renewable power system with high shares of VRE generation.

Research areas: Energy Production/Use
The albedo-climate penalty of hydropower reservoirs (2021)

Hydropower emits less carbon dioxide than fossil fuels but the lower albedo of hydropower reservoirs compared to terrestrial landscapes results in a positive radiative forcing, offsetting some of the negative radiative forcing of hydroelectricity generat ion. The cumulative effect of this lower albedo has not been quantified. Here we show, by quantifying the difference in remotely sensed albedo between globally distributed hydropower reservoirs and their surrounding landscape, that 19% of all investigated hydropower plants required 40 years or more for the negative radiative forcing from the fossil fuel displacement to offset the albedo effect. The length of these break-even times depends on the specific combination of climatic and environmental constraints, power plant design characteristics and country-specific electricity carbon intensities. We conclude that future hydropower plants need to minimize the albedo penalty to make a meaningful contribution towards limiting global warming.

Research areas: Energy Production/Use