nasa-gesdisc/es-publications-researchareas huggingface dataset:
Quantifying the impacts of DEM uncertainty on clear-sky surface (2022)

Accurate estimation of shortwave radiation in mountains will advance our knowledge of climate change effects, especially on mountain ecosystems. Recently, some approaches have been developed to estimate shortwave radiation parameters in mountains with satellite data, but few attempts were made to understand the impacts of digital elevation model (DEM) uncertainty on estimates. Our study investigates such impacts quantitatively in clear-sky conditions at multiple spatial and temporal scales (30-3000 m, instantaneous to daily). We employed a retrieval algorithm to estimate instantaneous and daily mean clear-sky downward shortwave radiation (DSR) and net shortwave radiation (NSR), as a proxy for our evaluation. The accuracy of our method based on accurate terrain data was verified against in-situ measurements with root-mean-square errors (RMSEs) of 65.9 W /m<SUP>2</SUP> and 65.1 W /m<SUP>2</SUP> for instantaneous DSR and NSR, and 21.2 W /m<SUP>2</SUP> and 22.5 W /m<SUP>2</SUP> for daily mean values, respectively. When using satellite DEM products, the DSR estimation uncertainty could increase by 64.0% for instantaneous values and 46.2% for daily mean values. Using AW3D30 and SRTM DEMs for DSR estimation led to a maximum difference of 16.8% (103.6 W /m<SUP>2</SUP>) and 13.0% (25.8 W /m<SUP>2</SUP>) on instantaneous and daily mean values, respectively. That estimation difference of shortwave radiation decreased with an increase in spatial scale, with RMS deviation lower than 2% for spatial resolution beyond 3000 m. In addition, the evaluation of introducing random errors into AW3D30 DEM showed that the shortwave radiation uncertainty caused by DEM may exceed the algorithm uncertainty itself with DEM mean absolute error (MAE) equaling about 5.0 m. Considering the current DEM accuracy, the impacts of DEM errors on shortwave radiation in mountains cannot be ignored. This study emphasizes the potential impacts of DEM uncertainty on surface shortwave radiation estimation, which is crucial in using satellite-derived datasets for energy balance calculation and climate change applications in mountains.

Research areas: Sun-Earth Interactions
Downward shortwave radiation estimation and spatial assessment on sites over complex terrain applying integrative approach of MTCLIM-XL, interpolation, RS and GIS (2017)

Downward shortwave radiation (DSR) is a highly variable solar source on spatiotemporal basis and essential for energy and agriculture systems, while its calculations are helpful in the environment-related studies, climatology, and monitoring fire risk. Statistical methods developed to extrapolate values of climatic variables and radiation could fail to generate reliable findings of DSR over a complex terrain without considering local topographic factors. In the present study, we proposed an integrative approach of MTCLIM-XL extrapolation with remote sensing (RS) and geographic information system (GIS) to estimate real-time DSR and its spatial potential over surfaces of contrasting elevated sites on a mountainous terrain of Quetta (Pakistan).Based on methodological approach, remote sensing data product of high-resolution DEM (SRTM 30m) was processed to extract topographic data, and meteorological data were obtained from a base site, Subsequently, MTCLIM-XL executed the simulation to calculate the daily-based DSR (W/m2).Spatial distribution of DSR was generated by applying deterministic interpolation with complementing quantification of Hillshade analysis for spatially obstructive surfaces, and resultant spatial hotspot-based potential was assessed on basis of specified threshold level (above 250 W/m2 = 2 kW h/m2) over the specified area. We observed usable potential of DSR at target sites and its spatial distribution during the study period of 2015 to April 2016. Using EUMETSAT CMSAF data as a standard, the validation demonstrates agreeable results of low RMSE and high correlation coefficient values for selected sites, except some sites with relatively high elevations and irregular gradients. Analysis of solar zenith angle to evaluate its inverse relation with increment in DSR values shows agreeable high inverse relation, while the negative trend for only some sites features relatively high rugged topography. In conclusion, MTCLIM-XL with RS and GIS integration manifests as a reliable approach for estimation and spatial potential assessment-based exploration of DSR over complex terrain having no ground data, while prospectively it will complement to the environment-related studies on local to mesoscale.

Research areas: Sun-Earth Interactions
The wider regional benefits of power grids improved resilience through tree-trimming operations evidences from Connecticut, USA (2020)

Tree-trimming operations (TTOs) are expensive, yet popular management practices for increasing power-grid reliability. In this work, we investigate and identify the relationship between TTOs and power outages and quantify the regional economic benefits TTOs provide in the three years following these operations. Our data focus on a portion of Connecticut, for 20092015. We find that even a limited application of TTOs reduce outages substantially. We combine this result with an advanced economic model to estimate the benefits to the state. We find that this reduction in outages translates in to considerable savings for the state's economy, justifying expansion of TTOs.

Research areas: Energy Production/Use
Modeling study of the impact of complex terrain on the surface energy and hydrology over the Tibetan Plateau (2019)

The long-term effects of complex terrain on solar energy distributions and surface hydrology over the Tibetan Plateau (TP) are investigated using the 4th version of the global Community Climate System Model (CCSM4) coupled with a 3-D radiative transfer (RT) parameterization. We examine the differences between the results from CCSM4 with the 3-D RT parameterization and the results from CCSM4 with the plane-parallel RT scheme. In January (winter), the net surface solar flux (FSNS) displays negative deviations over valleys and the north slopes of mountains, especially in the northern margin of the TP, as a result of the 3-D shadow effect. Positive deviations in FSNS in January are found over the south slopes of mountains and over mountain tops, where more solar flux is intercepted. The deviations in total cloud fraction and snow water equivalent (SWE) exhibit patterns opposite to that of FSNS. The SWE decreases due to the 3-D mountain effect in spring and the magnitude of this effect depends on the terrain elevations. The SWE is reduced by 117 mm over the TP in April, with the largest decrease in SWE at an elevation of 3.54.5 km. Negative deviations in precipitation are found throughout the year, except in May and December, and they follow the seasonal variations in the deviations in total cloud fraction. The total liquid runoff at 3.54.5 km elevation increases in April due to earlier (March) snowmelt caused by increased downward solar radiation. The possible deviations in surface energy and SWE over the TP, caused by plane-parallel assumption in most climate models may result in biases in the liquid runoff and the river water resources over the TP and downstream.

Research areas: Sun-Earth Interactions
Development of a Clear-Sky 3D Sub-Grid Terrain Solar Radiative Effect (2022)

Terrains strongly affect the surface solar radiation (SSR) and energy balance, and further greatly modulate the weather and climate in rugged areas. In this study, we have developed a clear-sky 3-dimensional sub-grid terrain solar radiative effect (3DSTSRE) parameterization scheme based on the mountain radiation theory with full consideration of the influences of 3-dimensional configuration of terrains. Results show that the 3DSTSRE scheme achieves the equivalent effect of the downward SSR flux at the model grids derived from those explicitly calculated at the sub-grids without reducing the calculating efficiency of numerical models. It performs well at model grids with different horizontal resolutions. The instant downward SSR flux calculated by the 3DSTSRE scheme at 76.8%, 84.8%, 88.7%, 91.6%, 93.0%, and 87.1% model grids with the horizontal resolution of 0.025°, 0.05°, 0.1°, 0.2°, 0.4°, and 0.8° in the areas featured by complex terrains shows relative errors within ±1.0% against those derived from the explicit calculations at sub-grids, respectively. The normalized mean absolute errors of the instant downward SSR flux calculated by the 3DSTSRE scheme are below 1% (2%) throughout the day and the year for the model grids with resolutions ranging from 0.05° to 0.8° (of 0.025°). Although the performance of 3DSTSRE scheme decreases slightly under the conditions with much lower solar zenith angle and finer model horizontal resolution, the 3DSTSRE scheme developed in current study shows broad application prospects in various numerical models with the advantages of a solid physical foundation, high accuracy, strong portability and flexibility.

Research areas: Sun-Earth Interactions
Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry (2023)

Abstract. Twilight gradients in the concentration of atmospheric species
with short photochemical lifetimes influence the transmission data obtained
in a solar occultation instrument, such as the Stratospheric Aerosol and Gas Experiment III aboard the International Space Station (SAGE III/ISS). These photochemically induced changes result in nonlinear asymmetries in the species distribution near the tangent altitude along the line of sight
(LOS). The bias introduced by neglecting the effects of twilight variations
in the retrieval of mesospheric ozone is the focus of this study. Ozone (O3) in the mesosphere exhibits large variations near the terminator during sunrise
and sunset based on current understanding of the photochemistry of this
altitude region. The algorithm used in the SAGE III/ISS standard retrieval
procedure for mesospheric ozone does not include the effects of these
gradients. This study illustrates a method for implementing a correction
scheme to account for the twilight variations in mesospheric O3 and
gives an estimate of the bias in the standard retrieval. We use the results
from a diurnal photochemical model conducted at different altitudes to
develop a database of ratios of mesospheric O3 at different solar
zenith angles (SZA) around 90 to O3 at a SZA of
90 for both sunrise and sunset conditions. These ratios are used
to scale the O3 at levels above the tangent altitude for appropriate
SZA in the calculation of the optical depth along the LOS. In general, the
impact of the corrections due to twilight variations is to increase the
contribution of the overlying layers to the optical depth thereby reducing
the retrieved O3 concentration at the tangent altitude. We find that
at sunrise the retrieved mesospheric O3 including the diurnal
corrections is lower by more than 30 % compared to the archived O3.
We show the results obtained for different latitudes and seasons. In
addition, for nearly collocated sunrise and sunset scans, we note that these
corrections lead to better qualitative agreement in the sunrise to sunset
O3 ratio with the photochemical model prediction.

Research areas: Air Quality
Solar spectral irradiance reconciliation of SORCE and TSIS1 SIM (2022)

The Solar Radiation and Climate Experiment (SORCE) recorded daily Solar Spectral Irradiance (SSI) measurements from 2003 to 2020, overlapping with the Total and Spectral Irradiance Sensor (TSIS1) for 2 years (Mar. 2018 - Feb. 2020). We use data from the Spectral Irradiance Monitors (SIM), spanning 704 days and 554 time-matched observations, to compare absolute irradiance calibrations in a truly unique space-based UV-IR spectroscopic overlap study. This 2002400 nm comparison was conducted during the Solar Cycle 24 minimum, so observed differences are likely instrumental. We find peak-to-peak (maximum) absolute scale differences of 12% with a mean fractional difference of 0.7  2.9%. A multiplicative scale correction factor (STICR) has been developed to reconcile the TSIS1 and SORCE SIM irradiance differences. Applying this correction to the SORCE-SIM V27 dataset, we provide a re-calibrated dataset known as the TSIS1-SIM Adjusted Values (TAV). We discuss the challenges in the creation of STICR and TAV, and lessons learned about using temporally overlapping space observatories to provide a continuous solar observation record.

Research areas: Sun-Earth Interactions, Validation
Updated GOES-13 Heliosat-2 Method for Global Horizontal Irradiation in (2022)

Increasing the utilization of renewable energy is at the center of most sustainability policies. Solar energy is the most abundant resource of this type on Earth, and optimizing its use requires the optimal estimation of surface solar irradiation. Heliosat-2 is one of the most popular methods of global horizontal irradiation (GHI) estimation. Originally developed for the Meteosat satellite, Heliosat-2 has been modified in previous work to deal with GOES-13 data and named here GOES_H2. This model has been validated through the computation of indicators and irradiation maps for the Guiana Shield. This article proposes an improved version of GOES_H2, which has been combined with a radiative transfer parameterization (RTP) and the McClear clear-sky model (MC). This new version, hereafter designated RTP_MC_GOES_H2, was tested on eight stations from the Baseline Surface Radiation Network, located in North and South America, and covered by GOES-13. RTP_MC_GOES_H2 improves the hourly GHI estimates independently of the type of sky. This improvement is independent of the climate, no matter the station, the RTP_MC_GOES_H2 gives better results of MBE and RMSE than the original GOES_H2 method. Indeed, the MBE and RMSE values, respectively, change from 11.93% to 2.42% and 23.24% to 18.24% for North America and from 4.35% to 1.79% and 19.97% to 17.37 for South America. Moreover, the flexibility of the method may allow to improve results in the presence of snow cover and rainy/variable weather. Furthermore, RTP_MC_GOES_H2 results outperform or equalize those of other operational models.

Research areas: Sun-Earth Interactions, Validation
Changing the policy paradigm: A benefit maximization approach to electricity planning in developing countries (2020)

Access to electricity can lead to enhanced education, business, and healthcare opportunities. Governments in emerging economies are often faced with the challenge of increasing access to electricity and reducing system inequality, while operating under severe budget constraints. This paper develops a methodology for finding the optimal expansion of a power system under the objective of maximizing social benefit, as it relates to distributional equality for electricity access, subject to a budget constraint. This contrasts with traditional models, which minimize the cost of satisfying projected electricity demand. We formulate a generation expansion planning problem as a utility-maximization mixed-integer linear program and apply it to a case study analysis of a low-income country with limited electricity infrastructure. We focus our analysis on understanding how the optimal allocation of generation between centralized and distributed resources is impacted by stakeholder preferences toward equality and different budget levels. We find that a high preference for equality leads to lower overall electricity consumption levels, but improved electrification rates due to greater investment (300750 km increase) in transmission infrastructure. If stakeholders move from a low to a high equality preference then they could see a 7287% increase in energy access equality rating depending on the budget. Conversely, indifference to equality leads to higher overall consumption levels in urban areas but reduced electrification rates. This methodology can help decision makers evaluate the social trade-offs between improving energy access, reducing energy inequality and poverty, and increasing total electricity consumption when operating under budget constraints in their countries.

Research areas: Energy Production/Use
Changes in toa sw fluxes over marine clouds when estimated via semiphysical angular distribution models (2021)

Abstract Top-of-atmosphere (TOA) shortwave (SW) angular distribution models (ADMs) approximateper angular direction of an imagined upward hemispherethe intensity of sunlight scattered back from a specific Earthatmosphere scene. ADMs are, thus, critical when converting satellite-borne broadband radiometry into estimated radiative fluxes. This paper applies a set of newly developed ADMs with a more refined scene definition and demonstrates tenable changes in estimated fluxes compared to currently operational ADMs. Newly developed ADMs use a semiphysical framework to consider cloud-top effective radius ( R e) and above-cloud water vapor (ACWV), in addition to accounting for surface wind speed and clouds phase, fraction, and optical depth. In effect, instantaneous TOA SW fluxes for marine liquid-phase clouds had the largest flux differences (of up to 25 W m2) for lower solar zenith angles and cloud optical depth greater than 10 due to extremes in R e or ACWV. In regions where clouds had persistently extreme levels of R e (here mostly for R e<7 m and R e>15 m) or ACWV, instantaneous fluxes estimated from Aqua, Terra, Meteosat-8, and Meteosat-9 satellites using the two ADMs differed systematically, resulting in significant deviations in daily mean fluxes (up to 10 W m2) and monthly mean fluxes (up to 5 W m2). Flux estimates using newly developed, semiphysical ADMs may contribute to a better understanding of solar fluxes over low-level clouds. It remains to be seen whether aerosol indirect effects are impacted by these updates.

Research areas: Sun-Earth Interactions
Evaluating the complementarity of solar, wind and hydropower to mitigate the impact of El Niño Southern Oscillation in Latin America (2021)

Latin America has the largest share of renewable energy for power generation in the world, but has historically been dependent on hydropower, and is vulnerable to long-term phenomena like the El Nino-Southern Oscillation (ENSO). The region is currently experiencing a steady increase in gas-based power generation along with a rapid growth in non-hydro renewables, mainly aimed at improving reliability. But exploiting complementarities between hydropower and other renewables could offer additional benefits. This paper investigates to what extent improved deployment of wind turbines and solar photovoltaic cells (PV), aimed at complementing existing hydropower, could mitigate the impacts of ENSO in Latin America. We use a meteorological reanalysis dataset to model the variations in wind-, solar- and hydropower throughout the entire 20th century and their association with different ENSO phases in the same period. A statistical algorithm is then used to identify locations at national and regional levels offering the maximal level of complementarity. The results show that adding 136 GW of wind- and solar-power with high-complementarity has the potential to cost-effectively compensate the fluctuations of hydropower and reduce the variability of renewable power not only during drought ENSO phases but also outside ENSO events. Benefits include: (i) an increase of up to 5-fold the minimum threshold of renewable power available every month, (ii) a reduction of up to 65% in the variability of renewable power generation, and (iii) reaching a levelized cost of electricity (LCOE) of 0.090.23 $/kWh, which is comparable to that of new gas plants.

Research areas: Energy Production/Use
Incorporating dynamic factors for improving a GIS-based solar radiation model (2020)

Solar radiation has been a major input to agricultural, hydrological, and ecological modeling. However, solar radiation is usually influenced by three groups of dynamic factors: sun–earth position, terrain, and atmospheric effects. Therefore, an integrated approach to accurately consider the impacts of those dynamic factors on solar radiation is essential to estimate solar radiation over rugged terrain. In this study, a spatial and temporal gap‑filling algorithm was proposed to obtain a seamless daily MODIS albedo dataset. A 1 km‑resolution digital elevation model was used to model the impact of local topography and shading by surrounding terrain on solar radiation. A sunshine‑based model was adopted to simulate radiation under the influence of clouds. A GIS‑based solar radiation model that incorporates albedo, shading by surrounding terrain, and variations in cloudiness was used to address the spatial variability of these factors in mountainous terrain. Compared with other independent solar radiation products, our model generated a more reliable solar radiation product over rugged terrain, with an R2 of 0.88 and an RMSE of 2.55 MJ m−2 day−1. The improved solar radiation products and open source app can be used further in practice or scientific research.

Research areas: Sun-Earth Interactions
Mean-preserving interpolation with splines for solar radiation modeling (2022)

Interpolation is a fundamental process in solar resource assessment that glues consecutive components of the modeling chain. Most interpolation techniques assume that the interpolating function must go through the interpolation points. However, this assumption does not fit with averaged datasets or variables that must be conserved across interpolation. Here I present a mean-preserving splines method for interpolating one-dimensional data that conserves the interpolated field and is appropriate for averaged datasets. It uses second-order polynomial splines to minimize the fluctuations of the interpolated field, restricts the interpolation results to user-provided limits to prevent unphysical values, deals with periodic boundary conditions in the interpolated field, and can work with non-uniform averaging grids. The validity and performance of the method are illustrated against regular second- and third-order splines using relevant case examples in the solar resource assessment realm.

Research areas: Sun-Earth Interactions, Validation
The BepiColombo solar conjunction experiments revisited (2021)

BepiColombo ESA/JAXA mission is currently in its 7 year cruise phase towards Mercury. The Mercury orbiter radioscience experiment (MORE), one of the 16 experiments of the mission, will start its scientific investigation during the superior solar conjunction (SSC) in March 2021 with a test of general relativity (GR). Other solar conjunctions will follow during the cruise phase, providing several opportunities to improve the results of the first experiment. MORE radio tracking system allows to establish precise ranging and Doppler measurements almost at all solar elongation angles (up to 7-8 solar radii), thus providing an accurate measurement of the relativistic time delay and frequency shift experienced by a radio signal during an SSC. The final objective of the experiment is to place new limits to the accuracy of the GR as a theory of gravity in the weak-field limit. As in all gravity experiments, non-gravitational accelerations acting on the spacecraft are a major concern. Because of the proximity to the Sun, the spacecraft will undergo severe solar radiation pressure acceleration, and the effect of the random fluctuations of the solar irradiance may become a significant source of spacecraft buffeting. In this paper we address the problem of a realistic estimate of the outcome of the SSC experiments of BepiColombo, by including in the dynamical model the effects of random variations in the solar irradiance. We propose a numerical method to mitigate the impact of the variable solar radiation pressure on the outcome of the experiment. Our simulations show that, with different assumptions on the solar activity and observation coverage, the accuracy attainable in the estimation of γ lays in the range [6-13] ×10<SUP>-6</SUP>.

Research areas: Sun-Earth Interactions