nasa-gesdisc/es-publications-researchareas huggingface dataset:
A Global Model for Iodine Speciation in the Upper Ocean (2020)

An ocean iodine cycling model is presented, which predicts upper ocean iodine speciation. The model comprises a three-layer advective and diffusive ocean circulation model of the upper ocean and an iodine cycling model embedded within this circulation. The two primary reservoirs of iodine are represented, iodide and iodate. Iodate is reduced to iodide in the mixed layer in association with primary production, linked by an iodine to carbon (I:C) ratio. A satisfactory model fit with observations cannot be obtained with a globally constant I:C ratio, and the best fit is obtained when the I:C ratio is dependent on sea surface temperature, increasing at low temperatures. Comparisons with observed iodide distributions show that the best model fit is obtained when oxidation of iodide back to iodate is associated with mixed layer nitrification. Sensitivity tests, where model parameters and processes are perturbed, reveal that primary productivity, mixed layer depth, oxidation, advection, surface freshwater flux, and the I:C ratio all have a role in determining surface iodide concentrations, and the timescale of iodide in the mixed layer is sufficiently long for nonlocal processes to be important. Comparisons of the modeled iodide surface field with parameterizations by other authors show good agreement in regions where observations exist but significant differences in regions without observations. This raises the question of whether the existing parameterizations are capturing the full range of processes involved in determining surface iodide and shows the urgent need for observations in regions where there are currently none.

Research areas: Ecosystems
Heterogeneity and chemical reactivity of the remote troposphere defined (2021)

Abstract. The NASA Atmospheric Tomography (ATom) mission built a
photochemical climatology of air parcels based on in situ measurements with
the NASA DC-8 aircraft along objectively planned profiling transects through
the middle of the Pacific and Atlantic oceans. In this paper we present and
analyze a data set of 10 s (2 km) merged and gap-filled observations of the
key reactive species driving the chemical budgets of O3 and CH4
(O3, CH4, CO, H2O, HCHO, H2O2, CH3OOH,
C2H6, higher alkanes, alkenes, aromatics, NOx, HNO3,
HNO4, peroxyacetyl nitrate, other organic nitrates), consisting of
146 494 distinct air parcels from ATom deployments 1 through 4. Six models
calculated the O3 and CH4 photochemical tendencies from this
modeling data stream for ATom 1. We find that 80 %90 % of the total
reactivity lies in the top 50 % of the parcels and 25 %35 % in the top
10 %, supporting previous model-only studies that tropospheric chemistry
is driven by a fraction of all the air. In other words, accurate simulation
of the least reactive 50 % of the troposphere is unimportant for global
budgets. Surprisingly, the probability densities of species and reactivities
averaged on a model scale (100 km) differ only slightly from the 2 km ATom
data, indicating that much of the heterogeneity in tropospheric chemistry
can be captured with current global chemistry models. Comparing the ATom
reactivities over the tropical oceans with climatological statistics from
six global chemistry models, we find excellent agreement with the loss of
O3 and CH4 but sharp disagreement with production of O3. The
models sharply underestimate O3 production below 4 km in both Pacific
and Atlantic basins, and this can be traced to lower NOx levels than
observed. Attaching photochemical reactivities to measurements of chemical
species allows for a richer, yet more constrained-to-what-matters, set of
metrics for model evaluation.

Research areas: Air Quality
Comparison and suggestion of indicators of concentrations associated with CO2 in seawater considering biological activity (2020)

Carbon dioxide capture and storage is expected to reduce large amount of CO2 emissions from pointwise large sources, such as coal power plants, by 2030 in Japan. For offshore CO2 storage, it is necessary to monitor concentrations associated with CO2 in seawater to ensure safe storage. To do so, it is also necessary to know the baseline concentrations in the target seas. However, such concentrations have large regional and seasonal variations, mainly because of biological activity. In this study, we compared various indicators of CO2 dissolved in seawater, using the seawater off Tomakomai, Japan, observed between 2013 and 2018. Among the indicators, we found very strong correlations between [nDIC + kDO] and T and between [DIC  0.5TA + kDO] and T. These indicators are thought to be effective for investigating the possibility of unexpected leakage of CO2 stored in sub-seabed geological formations. However, data always contain a degree of scattering, even when their correlation is very high. In the case of the seawater off Tomakomai, the data that exceeded a criteria based on the residual standard deviation of some indicators were not necessarily the same as those of the other indicators. Therefore, it is suggested that two or more, different types of indicators should be used, such as pCO2-[DO saturation] and [nDIC + kDO]-T or [DIC  0.5TA + kDO]-T.

Research areas: Greenhouse Gases
Simulation of airborne trace metals in fine particulate matter over North America (2019)

Trace metal distributions are of relevance to understand sources of fine particulate matter (PM2.5), PM2.5-related health effects, and atmospheric chemistry. However, knowledge of trace metal distributions is lacking due to limited ground-based measurements and model simulations. This study develops a simulation of 12 trace metal concentrations (Si, Ca, Al, Fe, Ti, Mn, K, Mg, As, Cd, Ni and Pb) over continental North America for 2013 using the GEOS-Chem chemical transport model. Evaluation of modeled trace metal concentrations with observations indicates a spatial consistency within a factor of 2. The spatial distribution of trace metal concentrations reflects their primary emission sources. Crustal element (Si, Ca, Al, Fe, Ti, Mn, K) concentrations are enhanced over the central US from anthropogenic fugitive dust and over the southwestern U.S. due to natural mineral dust. Heavy metal (As, Cd, Ni and Pb) concentrations are high over the eastern U.S. from industry. K is abundant in the southeast from biomass burning. High concentrations of Mg are observed along the coast from sea spray. The spatial pattern of PM2.5 mass is most strongly correlated with Pb, Ni, As and K due to their signature emission sources. Challenges remain in accurately simulating observed trace metal concentrations. Halving anthropogenic fugitive dust emissions in the 2011 National Air Toxic Assessment (NATA) inventory and doubling natural dust emissions in the default GEOS-Chem simulation was necessary to reduce biases in crustal element concentrations. A fivefold increase of anthropogenic emissions of As and Pb was necessary in the NATA inventory to reduce the national-scale bias versus observations by more than 80%, potentially reflecting missing sources.

Research areas: Air Quality
Interannual Variability of the Lena River Plume Propagation in 1993-2020 (2021)

The Lena River plume significantly affects the thermohaline, optical and chemical properties of the eastern Arctic seas. We use sea surface salinity (SSS), temperature (SST), and altimetry measurements to study features of the Lena plume propagation during 19932020. A comparison of Soil Moisture Active Passive (SMAP) SSS measurements with in situ data obtained using the flow-through system in oceanographic surveys in 20182019 demonstrates good coincidence with correlation ~ 0.96 and RMSD ~ 1 psu. The SMAP data were used to reconstruct the plume evolution in 20152020 and to identify three main types of Lena plume propagation, which are mainly related to the variability of dominant zonal wind direction: northernthe plume moves to the north from the delta up to 78 N; easternthe plume moves eastward along the Siberian coast up to 180 E; mixed between two main types. Brackish plume waters were characterized by increased temperature and sea level, which provides the opportunity for studying the Lena plume dynamics using satellite altimetry and infrared measurements. These data were analyzed to study the interannual variability of plume propagation during the ice-free period of 19932020. The obtained results show that the northern type is observed twice more often than the eastern one, but the eastern type has intensified since 2010.

Research areas: Atmospheric/Ocean Indicators
Modeling Gross Primary Production of Midwestern US Maize and Soybean (2020)

Gross primary production (GPP) is a useful metric for determining trends in the terrestrial carbon cycle. To estimate daily GPP, the cloud-adjusted light use efficiency model (LUEc) was developed by adapting a light use efficiency (LUE, ) model to include in situ meteorological data and biophysical parameters. The LUEc uses four scalars to quantify the impacts of temperature, water stress, and phenology on . This study continues the original investigation in using the LUEc, originally limited to three AmeriFlux sites (US-Ne1, US-Ne2, and US-Ne3) by applying gridded meteorological data sets and remotely sensed green leaf area index (gLAI) to estimate daily GPP over a larger spatial extent. This was achieved by including data from four additional AmeriFlux locations in the U.S. Corn Belt for a total of seven locations. Results show an increase in error (RMSE = 3.5 g C m2 d1) over the original study in which in situ data were used (RMSE = 2.6 g C m2 d1). This is attributed to poor representation of gridded weather inputs (vapor pressure and incoming solar radiation) and application of gLAI algorithms to sites in Iowa, Minnesota, and Illinois, calibrated using data from Nebraska sites only, as well as uncertainty due to climatic variation. Despite these constraints, the study showed good correlation between measured and LUEc-modeled GPP (R2 = 0.80 and RMSE of 3.5 g C m2 d1). The decrease in model accuracy is somewhat offset by the ability to function with gridded weather datasets and remotely sensed biophysical data. The level of acceptable error is dependent upon the scope and objectives of the research at hand; nevertheless, the approach holds promise in developing regional daily estimates of GPP.

Research areas: Ecosystems
Evaluating the economic fairways for hydrogen production in Australia (2021)

Assessments of hydrogen project viability typically focus on evaluating specific sites for development, or providing generic cost-estimates that are independent of location. In reality, the success of hydrogen projects will be intimately linked to the availability of local energy resources, access to key infrastructure and water supplies, and the distance to export ports and energy markets. In this paper, we present an economic model that incorporates assessments of these regional factors to identify areas of high economic potential for hydrogen production  the so-called Economic Fairways for such projects. In doing so, the model provides a tool that can be used to inform investors and policy makers on the available opportunities for hydrogen development and their infrastructure requirements. The model includes analysis of the regional economic potential for both blue and green hydrogen projects. It accounts for hydrogen production from renewable (wind and solar) sources, as well as non-renewable sources (steam-methane reformation and coal gasification) combined with carbon capture and storage. Results from case studies conducted with the tool are presented, illustrating the potential for hydrogen production across Australia.

Research areas: Energy Production/Use
Atmospheric oxidation in the presence of clouds during the Deep Convective Clouds and Chemistry (DC3) study (2018)

Abstract. Deep convective clouds are critically important to the distribution of atmospheric constituents throughout the troposphere but are difficult environments to study. The Deep Convective Clouds and Chemistry (DC3) study in 2012 provided the environment, platforms, and instrumentation to test oxidation chemistry around deep convective clouds and their impacts downwind. Measurements on the NASA DC-8 aircraft included those of the radicals hydroxyl (OH) and hydroperoxyl (HO2), OH reactivity, and more than 100 other chemical species and atmospheric properties. OH, HO2, and OH reactivity were compared to photochemical models, some with and some without simplified heterogeneous chemistry, to test the understanding of atmospheric oxidation as encoded in the model. In general, the agreement between the observed and modeled OH, HO2, and OH reactivity was within the combined uncertainties for the model without heterogeneous chemistry and the model including heterogeneous chemistry with small OH and HO2 uptake consistent with laboratory studies. This agreement is generally independent of the altitude, ozone photolysis rate, nitric oxide and ozone abundances, modeled OH reactivity, and aerosol and ice surface area. For a sunrise to midday flight downwind of a nighttime mesoscale convective system, the observed ozone increase is consistent with the calculated ozone production rate. Even with some observed-to-modeled discrepancies, these results provide evidence that a current measurement-constrained photochemical model can simulate observed atmospheric oxidation processes to within combined uncertainties, even around convective clouds. For this DC3 study, reduction in the combined uncertainties would be needed to confidently unmask errors or omissions in the model chemical mechanism.

Research areas: Validation
Underreporting and open burning–the two largest challenges for sustainable waste management in India (2021)

The total waste generation in India reported for 2015 is highly uncertain (51300 Tgy1), primarily because observational data from rural regions within India is lacking. This makes it difficult to constrain rural waste generation rates. Official government data (51 Tg) denies the existence of rural waste generation in India. The rural data gap makes it difficult to construct accurate open waste burning emission inventories and plan waste management infrastructure. Our study presents activity data from understudied rural regions across India and establishes a relationship between waste generation and household income for both urban and rural India. We use this relationship to create a 0.1 x 0.1 gridded waste generation and waste treatment dataset and construct an open waste burning emission inventory for India (OWBEII) for the year 2020, after segregating both the rural and urban population into 5 income group with the help of socioeconomic data from the national health surveys. We find that out of 192 (102231) Tgy1 waste generated in 2020, 74 (3092) Tgy1 was burned in the open. Open waste burning is a widely established practice of waste disposal in developing nations and emits particulate matter (2851401 Ggy1 PM2.5 and 3221486 Ggy1 PM10), a suite of carcinogens (1982 Ggy1 benzene) and very reactive VOCs, which act as precursors to tropospheric ozone and secondary aerosol formation. The anthropogenic emissions of formaldehyde (a Group 1 carcinogen) from this source are 5.7 times larger than India's currently recognized total anthropogenic budget of formaldehyde in the EDGARv4.3.2 emission inventory.

Research areas: Environmental Impacts
Variation patterns and driving factors of regional atmospheric CO2 anomalies in China (2021)

Atmospheric CO2 anomaly (XCO2) is essential in evaluating regional carbon balance. However, it is difficult to understand XCO2 variation characteristics due to regional differences. This paper explored the inter-annual and inter-monthly variation patterns of XCO2 in different regions of China based on satellite observations. The relation model between regional XCO2 and anthropogenic emissions, gross primary productivity (GPP), wind speed, upwind regions emission, and upwind regions CO2 concentration was established. Results show that the annual average XCO2 in the northwest and southeast regions is stable at around 0 and 12 ppm, respectively. Some municipalities directly under the central government and the southern coastal areas showed relatively intense inter-annual fluctuations. Four inter-monthly XCO2 variation patterns were observed: the northern region has a stable change, the northeast region has the lowest in summer, the southwest region has the highest in summer, and the central region has no obvious change rule. Furthermore, XCO2 in most areas can be explained by the emissionabsorptiontransportation model. Significant positive XCO2 in the southern coastal region in summer may be related to the stable GPP seasonal variation and increased power generation. In the southwestern plateau region, it may be related to the low wind speed and increased soil emission with rising temperature. The stability of the plateau carbon sink and inter-regional cooperation cannot be ignored for improving regional atmospheric environments.

Research areas: Greenhouse Gases
Long-term observational constraints of organic aerosol dependence on inorganic species in the southeast US (2020)

Abstract. Organic aerosol (OA), with a large biogenic fraction in the summertime southeast US, adversely impacts air quality and human health. Stringent air
quality controls have recently reduced anthropogenic pollutants including sulfate, whose impact on OA remains unclear. Three filter measurement
networks provide long-term constraints on the sensitivity of OA to changes in inorganic species, including sulfate and ammonia. The 20002013
summertime OA decreases by 1.7 % yr11.9 % yr1 with little month-to-month variability, while sulfate
declines rapidly with significant monthly difference in the early 2000s. In contrast, modeled OA from a chemical-transport model (GEOS-Chem) decreases
by 4.9 % yr1 with much larger monthly variability, largely due to the predominant role of acid-catalyzed reactive uptake of
epoxydiols (IEPOX) onto sulfate. The overestimated modeled OA dependence on sulfate can be improved by implementing a coating effect and assuming
constant aerosol acidity, suggesting the needs to revisit IEPOX reactive uptake in current models. Our work highlights the importance of secondary
OA formation pathways that are weakly dependent on inorganic aerosol in a region that is heavily influenced by both biogenic and anthropogenic
emissions.

Research areas: Air Quality
River plastic emissions to the world's oceans (2017)

Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies.

Research areas: Environmental Impacts, Water Quality
Socio-Hydrological Approach to the Evaluation of Global Fertilizer Substitution by Sustainable Struvite Precipitants from Wastewater (2018)

Abstract. Despite Africa controlling the vast majority of the global phosphate it also faces the greatest food shortages  partially due to a lack of access to the fertilizer market. A more accessible source of phosphorus comes from wastewater flows, which is currently lost through the discharge to open surface waters. Analysing the potential phosphorus production of urban and livestock wastewater in meeting partial agricultural demand for phosphorus can improve food security, reduce consumption of unrenewable phosphorus, reduce pollution, and aid the transitioning to a circular economy. In this study, a global overview is provided where a selection of P-production and P-consumption sites have been determined using global spatial data. Distances, investment costs and associated carbon footprints are then considered in modelling a simple, alternative trade network of struvite phosphorus flows. The network reveals potential for increasing the phosphorus security through phosphorus recycling in particularly the South Africa, Lake Victoria and Nigeria regions. Given Africa's rapid urbanization, phosphorus recovery from wastewater will prove an important step in creating sustainable communities, protecting the environment while improving food security, and so contributing to the United Nations 2030 Agenda for Sustainable Development.

Research areas: Water Quality
Constraining Fossil Fuel CO<inf>2</inf> Emissions From Urban Area Using OCO-2 Observations of Total Column CO<inf>2</inf> (2020)

Satellite observations of the total column dry-air CO<SUB>2</SUB> (X<SUB>CO2</SUB>) are expected to support the quantification and monitoring of fossil fuel CO<SUB>2</SUB> (ffCO<SUB>2</SUB>) emissions from urban areas. We evaluate the utility of the Orbiting Carbon Observatory 2 (OCO-2) X<SUB>CO2</SUB> retrievals to optimize whole-city emissions, using a Bayesian inversion system and high-resolution transport modeling. The uncertainties of constrained emissions related to transport model, satellite measurements, and local biospheric fluxes are quantified. For the first two uncertainty sources, we examine cities of different landscapes: "plume city" located in relatively flat terrain, represented by Riyadh and Cairo; and "basin city" located in basin terrain, represented by Los Angeles (LA). The retrieved scaling factors of emissions and their uncertainties show prominent variabilities from track to track, due to the varying meteorological conditions and relative locations of the tracks transecting plumes. To explore the performance of multiple tracks in retrieving emissions, pseudo data experiments are carried out. The estimated least numbers of tracks required to constrain the total emissions for Riyadh (&lt;10% uncertainty), Cairo (&lt;10%), and LA (&lt;5%) are 8, 5, and 7, respectively. Additionally, to evaluate the impact of biospheric fluxes on derivation of the ffX<SUB>CO2</SUB> enhancements, we conduct simulations for Pearl River Delta metropolitan area. Significant fractions of local X<SUB>CO2</SUB> enhancements associated with local biospheric X<SUB>CO2</SUB> variations are shown, which potentially lead to biased estimates of ffCO<SUB>2</SUB> emissions. We demonstrate that satellite measurements can be used to improve urban ffCO<SUB>2</SUB> emissions with a sufficient amount of measurements and appropriate representations of the uncertainty components.

Research areas: Greenhouse Gases