NASA's Satellite Research Articles

Improved Biomass Calibration and Validation With Terrestrial LiDAR: Implications for Future LiDAR and SAR Missions

Future NASA and ESA satellite missions plan to better quantify global carbon stocks through detailed observations of forest structure, but ultimately rely on uncertain ground measurement approaches for calibration and validation. A substantial amount of uncertainty in estimating plot-level biomass can be attributed to inadequate and unrepresentative allometric relationships used to convert plot-level tree measurements to estimates of aboveground biomass. These allometric equations are known to have high errors and biases, particularly in carbon-rich forests, because they were calibrated with small and often biased samples of destructively harvested trees. To overcome this issue, we present and test a framework for nondestructively estimating tree and plot-level biomass with terrestrial laser scanning (TLS). We modeled 243 trees from 12 species with TLS and created ten low-RMSE allometric equations. The full 3-D reconstructions, TLS allometry, and Jenkins et al. (2003) allometry were used to calibrate SAR- and LiDAR-based empirical biomass models to investigate the potential for improved accuracy and reduced uncertainty. TLS reduced plot-level RMSE from 18.5% to 9.8% and revealed a systematic negative bias in the national equations. At the calibration stage, allometric uncertainty accounted for 2.8–28.4% of the total RMSE, increasing in relative contribution as calibration improved with sensor fusion. Our findings suggest that TLS plot acquisitions and nondestructive allometry can play a vital role for reducing uncertainty in calibration and validation data for biomass mapping in the upcoming NASA and ESA missions.

Navigating noise when comparing satellite and acoustic remote sensing data

Using a novel combination of NASA satellite products and acoustic remote sensing measurements, we aim to examine the link between the surface expression and vertical structure of ocean productivity and biomass in the California Current System. Water column sonar data collected by the National Marine Fisheries Service for fisheries management have been archived at the NOAA National Centers for Environmental Information. These data are used to evaluate the variability of the marine biogeography. To identify patterns of acoustic reflectance of marine organisms, the data must first be free of noise and seafloor acoustic returns. However, removing the variety of noise present has proved to be a challenge due to need for manual tuning, a resource prohibitive step, and the size and complexity of the acoustic data. Collaboration with the University of Colorado’s Earth Lab has led to the development of machine learning models to automatically remove noise from this large dataset. An analysis of the fully automated, semi-manual, and machine learning quality control processes will be presented. The cleaned acoustic data are then compared to the interannual variability of the distribution of surface chlorophyll concentration and temperature from satellite ocean color measurements.

Evaluation of Reconstructions of Snow/Ice Melt in Greenland by Regional Atmospheric Climate Models Using Laser Altimetry Data

AbstractThe surface mass balance of the Greenland ice sheet critically depends on the intensity of ice melt/snowmelt in its ablation zone, but in situ data have been too limited to quantify the error of regional climate models. Here we use 23 years of NASA satellite and airborne laser altimetry from the Airborne Topographic Mapper; Land, Vegetation, and Ice Sensor; and Ice, Cloud, and land Elevation Satellite to generate time series of elevation change to compare with surface mass balance products from the Regional Atmospheric Climate Model and from the Modèle Atmosphérique Régional. For 1994–2016, the results agree at the 15–26% level, with the largest discrepancy in North Greenland. During the cold summer of 2015, the root‐mean‐square discrepancy is 40% in the north, 30% in the southwest, and 18–25% at low elevation. The difference drops to 23% in the southwest and 14% at low elevation during the 2016 warm summer.

Assessment of Aquarius Sea Surface Salinity

Aquarius was the first NASA satellite to observe the sea surface salinity (SSS) over the global ocean. The mission successfully collected data from 25 August 2011 to 7 June 2015. The Aquarius project released its final version (Version-5) of the SSS data product in December 2017. The purpose of this paper is to summarize the validation results from the Aquarius Validation Data System (AVDS) and other statistical methods, and to provide a general view of the Aquarius SSS quality to the users. The results demonstrate that Aquarius has met the mission target measurement accuracy requirement of 0.2 psu on monthly averages on 150 km scale. From the triple point analysis using Aquarius, in situ field and Hybrid Coordinate Ocean Model (HYCOM) products, the root mean square errors of Aquarius Level-2 and Level-3 data are estimated to be 0.17 psu and 0.13 psu, respectively. It is important that caution should be exercised when using Aquarius salinity data in areas with high radio frequency interference (RFI) and heavy rainfall, close to the coast lines where leakage of land signals may significantly affect the quality of the SSS data, and at high-latitude oceans where the L-band radiometer has poor sensitivity to SSS.

The TanSat mission: preliminary global observations

The Chinese global carbon dioxide monitoring satellite (TanSat) was launched successfully in December 2016 and has completed its on-orbit tests and calibration. TanSat aims to measure the atmospheric column-averaged dry air mole fractions of carbon dioxide (XCO2) with a precision of 4 ppm at the regional scale, and in addition, to derive global and regional CO2 fluxes. Progress towards these objectives is reviewed and the first scientific results from TanSat measurements are presented. TanSat on-orbit tests indicate that the Atmospheric Carbon dioxide Grating Spectrometer is in normal working status and is beginning to produce L1B products. The preliminary TanSat XCO2 products have been retrieved by an algorithm and compared to NASA Orbiting Carbon Observatory-2 (OCO-2) measurements during an overlapping observation period. Furthermore, the XCO2 retrievals have been validated against eight ground-site measurement datasets from the Total Carbon Column Observing Network, for which the preliminary conclusion is that TanSat has met the precision design requirement, with an average bias of 2.11 ppm. The first scientific observations are presented, namely, the seasonal distributions of XCO2 over land on a global scale.

Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive

The McIntosh Archive consists of a set of hand-drawn solar Carrington maps created by Patrick McIntosh from 1964 to 2009. McIntosh used mainly H, He-I 10830A and photospheric magnetic measurements from both ground-based and NASA satellite observations. With these he traced polarity inversion lines (PILs), filaments, sunspots and plage and, later, coronal holes over a ~45-year period. This yielded a unique record of synoptic maps of features associated with the large-scale solar magnetic field over four complete solar cycles. We first discuss how these and similar maps have been used in the past to investigate long-term solar variability. Then we describe our work in preserving and digitizing this archive, developing a digital, searchable format, and creating a website and an archival repository at NOAA’s National Centers for Environmental Information (NCEI). Next we show examples of how the data base can be utilized for scientific applications. Finally, we present some preliminary results on the solar-cycle evolution of the solar magnetic field, including the polar field reversal process, the evolution of active longitudes, and the role of differential solar rotation.

Unmasking the negative greenhouse effect over the Antarctic Plateau

A paradoxical negative greenhouse effect has been found over the Antarctic Plateau, indicating that greenhouse gases enhance energy loss to space. Using 13 years of NASA satellite observations, we verify the existence of the negative greenhouse effect and find that the magnitude and sign of the effect varies seasonally and spectrally. A previous explanation attributes this effect solely to stratospheric CO2; however, we surprisingly find that the negative greenhouse effect is predominantly caused by tropospheric water vapor. A recently developed principle-based concept is used to provide a complete account of the Antarctic Plateau’s negative greenhouse effect indicating that it is controlled by the vertical variation of temperature and greenhouse gas absorption. Our findings indicate that unique climatological conditions over the Antarctic Plateau—a strong surface-based temperature inversion and scarcity of free tropospheric water vapor—cause the negative greenhouse effect.

Detection of transverse cirrus bands in satellite imagery using deep learning

We demonstrate the viability of using a convolutional neural network (CNN) for facial recognition of meteorological phenomena in satellite imagery. Transfer learning was used to fine tune the widely used VGG-16 network architecture and allow the network to successfully detect (94% accuracy) the presence of transverse cirrus bands (TCBs) in NASA MODIS and VIIRS satellite browse imagery. The CNN exhibited better performance compared to a random forest classifier (84% accuracy) and was further validated by applying it to NASA satellite browse imagery in order to create a multi-year (2013–2015) global heat map of TCB occurrence. The annual heat map shows spatial patterns that are consistent with known mechanisms for the generation of TCBs, providing confidence in the CNN classifications. Our study shows that CNNs are well suited for meteorological phenomena detection due to their generalization capabilities and strong performance. An immediate application of our work intends to enable phenomena-based search of big satellite imagery databases. With additional modifications, the CNN could be utilized for other applications such as providing situational awareness to operational forecasters or developing phenomena specific climatologies.

Statistical Characteristics of Meteoroid Parameters in the Earth’s Atmosphere

Statistical characteristics of meteoroids with kinetic energy from 0.1 to 440 kt TNT are estimated based on NASA satellite observations made in 1994–2016. The distributions of the number of falling meteoroids are constructed and analyzed based on the values of their initial kinetic energy, initial velocity, initial mass, altitude, geographic coordinates of the maximum total radiated energy region, and the year of the fall. Correlation dependences “mass–initial kinetic energy,” “maximum total radiated energy region altitude–initial kinetic energy,” and “maximum total radiated energy region altitude–initial velocity (the square of the initial velocity)” are constructed.

CTR Wilson Meeting 2016

CTR Wilson Meeting 2016

Geohealth: biology based mapping of vector borne disease in the Americas using NASA satellite data

Implementation of a geospatial surveillance and response system data resource for vector borne disease in the Americas (GeoHealth) will be tested using NASA satellite data, geographic information systems and ecological niche modeling to characterize the environmental suitability and potential for spread of endemic and epizootic vector borne diseases. The initial focus is on developing prototype geospatial models for visceral leishmaniasis, an expanding endemic disease in Latin America, and geospatial models for dengue and other Aedes aegypti borne arboviruses (zika, chikungunya), emerging arboviruses with potential for epizootic spread from Latin America and the Caribbean and establishment in North America. Geospatial surveillance and response system open resource data bases and models will be made available, with training courses, to other investigators interested in mapping and modeling other vector borne diseases in the western hemisphere and contributing brokered data to an expanding GeoHealth data resource as part of the NASA AmeriGEOSS initiative.

Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties

Abstract. Information content analysis is used to select channels for a marine liquid cloud retrieval using the high-spectral-resolution oxygen A-band instrument on NASA's Orbiting Carbon Observatory-2 (OCO-2). Desired retrieval properties are cloud optical depth, cloud-top pressure and cloud pressure thickness, which is the geometric thickness expressed in hectopascals. Based on information content criteria we select a micro-window of 75 of the 853 functioning OCO-2 channels spanning 763.5–764.6 nm and perform a series of synthetic retrievals with perturbed initial conditions. We estimate posterior errors from the sample standard deviations and obtain ±0.75 in optical depth and ±12.9 hPa in both cloud-top pressure and cloud pressure thickness, although removing the 10 % of samples with the highest χ2 reduces posterior error in cloud-top pressure to ±2.9 hPa and cloud pressure thickness to ±2.5 hPa. The application of this retrieval to real OCO-2 measurements is briefly discussed, along with limitations and the greatest caution is urged regarding the assumption of a single homogeneous cloud layer, which is often, but not always, a reasonable approximation for marine boundary layer clouds.

Analysis of Various NASA Satellite Images through the Techniques of Image Morphing

Image morphing is a technique that implements linear algebra (geometric and algebraic transformation techniques) to transform one point in a plane to the other. We analyze images through image morphing techniques to predict changes that had happened through time and also what might happen in the future. The purpose of this particular research is to observe the changes of different NASA satellite images, describe the observations, and hypothesize the possible causes of the phenomena observed in the morph. This is performed by using two satellite images. These images were taken at two different intervals of time, morph the images and observed the gradual changes of the objects. The selected pictures did not have additional documentation (for example, images between a selected interval of time) available to compare so morph was used to analyze the transition. How accurate are all these morphing techniques? The accuracy of the transformation is analyzed by taking pictures of a blooming flower and documents all the phases between the blooms. Then, the morphing technique is implemented towards the first and last picture to compare the changes previously observed in the morph. This experiment was conducted to predict the uncertainty of the transformation. Image morphing techniques are important because when satellites document images of an object at a certain time, it may take a while for another picture to be documented again. By then, many things could have changed and the purpose is to investigate how such changes occurred. The morph is an accurate approximation to the actual changes of the objects and a very useful tool to use when it is impossible to take consecutive pictures of a constantly changing place or object. Furthermore, this technique can help to discover patterns of the objects and enable scientists to hypothesize future changes. A morphing software named, Morph Age, was used to morph the pictures.

The End of Night.

The article reports that according to a research there is expansion in the earth's artificially lit area. Topics include replacement of sodium- vapor technology by LED lamps; information on nasa satellite instrument called the Visible Infrared Imaging Radiometer Suite (VIIRS) which can measure long wavelengths of light such as those produced by traditional yellow-and-orange sodium-vapor street lamps; and views of Fabio Falchi, from Light Pollution Science and Technology Institute, on VIIRS.

Distribution of planktonic biogenic carbonate organisms in the Southern Ocean south of Australia: a baseline for ocean acidification impact assessment

Abstract. The Southern Ocean provides a vital service by absorbing about one-sixth of humankind's annual emissions of CO2. This comes with a cost – an increase in ocean acidity that is expected to have negative impacts on ocean ecosystems. The reduced ability of phytoplankton and zooplankton to precipitate carbonate shells is a clearly identified risk. The impact depends on the significance of these organisms in Southern Ocean ecosystems, but there is very little information on their abundance or distribution. To quantify their presence, we used coulometric measurement of particulate inorganic carbonate (PIC) on particles filtered from surface seawater into two size fractions: 50–1000 µm to capture foraminifera (the most important biogenic carbonate-forming zooplankton) and 1–50 µm to capture coccolithophores (the most important biogenic carbonate-forming phytoplankton). Ancillary measurements of biogenic silica (BSi) and particulate organic carbon (POC) provided context, as estimates of the biomass of diatoms (the highest biomass phytoplankton in polar waters) and total microbial biomass, respectively. Results for nine transects from Australia to Antarctica in 2008–2015 showed low levels of PIC compared to Northern Hemisphere polar waters. Coccolithophores slightly exceeded the biomass of diatoms in subantarctic waters, but their abundance decreased more than 30-fold poleward, while diatom abundances increased, so that on a molar basis PIC was only 1 % of BSi in Antarctic waters. This limited importance of coccolithophores in the Southern Ocean is further emphasized in terms of their associated POC, representing less than 1 % of total POC in Antarctic waters and less than 10 % in subantarctic waters. NASA satellite ocean-colour-based PIC estimates were in reasonable agreement with the shipboard results in subantarctic waters but greatly overestimated PIC in Antarctic waters. Contrastingly, the NASA Ocean Biogeochemical Model (NOBM) shows coccolithophores as overly restricted to subtropical and northern subantarctic waters. The cause of the strong southward decrease in PIC abundance in the Southern Ocean is not yet clear. The poleward decrease in pH is small, and while calcite saturation decreases strongly southward, it remains well above saturation ( > 2). Nitrate and phosphate variations would predict a poleward increase. Temperature and competition with diatoms for limiting iron appear likely to be important. While the future trajectory of coccolithophore distributions remains uncertain, their current low abundances suggest small impacts on overall Southern Ocean pelagic ecology.

NASA Satellites Help us to Quickly Detect Forest Fires

The main idea is that, as the forests of the planet are getting smaller, too much wood is cut and the forests are made too slow, there are also large forest fires due to excessive heat, of people arguing with the law, or simply by chance. Extinguishing fires are generally difficult, interventions being difficult anyway due to the increased the heavy access of the firefighters to the forest, the wind that often attacks the fire and especially due to the late intervention of the specialized firefighters. A first aid could come from finding out the moment when such a fire broke out and instantly signaling it with modern wireless systems. Today, the planet's best surveillance system is the one made with artificial geostationary satellites, which instantly signals the outbreak of the fire. The system set up by NASA is indeed the most efficient possible. Find out quickly by the outbreak of fire the chances for him to be controlled quickly grow very much. satellite tools are often the first to detect fires that are burning in distant regions and new fire locations are sent directly to field managers around the world in a few hours of satellite travel. Together, tools, including a number built and run by the JAS NASA lab in Pasadena, California, have detected fire-fighting actions by tracking fires by providing information on fire management and stair scaling in scar scars. NASA has a fleet of earth observation tools, many of which contribute to our understanding of the Earth's fire. Satellites in orbit around the poles provide observations of the entire planet several times a day, while satellites in geostationary orbit offer rough resolution images of smoke and clouds every five to fifteen minutes. NASA's satellite, land and space survey captures the total impact of the fire on the Earth, from early detection of smoke and ecosystems to decades after the fire, said Doug Morton, a researcher at Greenbelt, Maryland. Much of the remote sensing data that NASA collects for fires is quickly available to help disaster response efforts around the world. The NASA earthquake program supports this application science and mobilizes for high-risk global events that cover a range of natural hazards - not only fires, but also earthquakes, tsunamis, floods, landslides, severe weather, winter, tropical cyclones and volcanoes. In this study we want to propose the future use of robots instead of humans for such dangerous fire-fighting interventions in a forest in flame. Robotic and automated vehicles may be prepared to take over this difficult task for man, extinguishing such a fire making it simpler and less dangerous for humans.

Supernova 1987A, 30 Years Later

Most supernova theories state that this phenomenon lasts for a few seconds and ends with a big final explosion. However, these theories do not take into account several experimental results obtained with neutrino and gravitational wave detectors during the explosion of SN 1987A, the only supernova observed in a nearby galaxy in modern age. According to these experimental results the phenomenon is much more complex that envisaged by current theories, and has a duration of several hours. Since recent data of the X-ray NASA Satellite NuSTAR show a clear evidence of an asymmetric collapse, we have revisited the experimental data recorded by some underground and gravitational wave detectors running at the time of SN 1987A. New evidence is shown that confirms the previous results, namely that the data recorded by the gravitational wave detectors running in Rome and in Maryland are strongly correlated with the data of both the LSD (Mont Blanc) and the Kamiokande detectors, and that the correlation extends over a long period of time (one or two hours) centered at the Mont Blanc time. In addition, the signals of the GW detectors preceded the signals of the underground detectors by a time of order of one second. This result, obtained by comparing six independent files of data recorded by four different experiments located at intercontinental distances, indicates that also Kamiokande detected neutrinos at theMont Blanc time, but these interactions were not identified because not grouped in a burst. A similar correlation was also found in the data of the underground experiments in Mont Blanc and Baksan.

The Near Bottom Hypoxia and Hydrogen Sulphide Formation on the Black Sea Shelf

Purpose. Estimation of the Northwestern part of the Black Sea Shelf in modern period. Methods. The sample of average daily measurements of the temperature, salinity on the surface, level, wind velocity and direction during 2007, 2012 and 2017 had been done. The analyses of the cruise investigation parameters and NASA satellite photos had been done in this region as well. Results. Increasing of nutrient, heavy metals, oil concentration in the Danube, Dnieper and Dniester of water runoff was fixed during the last 50 years. It was the reason of its permanent accumulation in marine ecosystem. Also it was the reason of anthropogenic eutrophication development in the sea water in spring and at the beginning of summer time. Later, at the end of summer and in autumn the dissolved oxygen is decreasing in the bottom layers because of destruction of organic matter. In the last years, decreasing of nutrient from the rivers input was marked. It provided the increasing the transparency in the sea column and made the water condition more positive. But for assessment of the whole ecosystem state the complexes monitoring is absolutely necessary. In September of 2017 the special investigation cruise was done. The result shown the deficit of the dissolved oxygen – hypoxia in the near bottom layer is spreading in the center of the shelf ecosystem (the depths are more than 20 m). The oxygen concentrations were less than 2,0 ml/l.. The reason of this negative phenomena was provided by NASA satellite photos of eutrophication process in summer and marking of upwelling at the shallow waters during the warm period in 2007, 2012 and 2017. Conclusions. Anthropogenic eutrophication development in the sea water was fixed as well as the near bottom hypoxia and hydrogen sulphide formation in the Ukrainian part of the Northwestern shelf of the Black sea in the modern period. Spatial scale of this phenomena is comparable with the scales from 70's of last century.

Assessing Irrigation Aquifer Depletion: Introduction

Assessing Irrigation Aquifer Depletion: Introduction

Collaborations and Partnerships in NASA’s Earth Science Data Systems

NASA has been collecting Earth observation data from spaceborne instruments since 1960. Today, there are tens of satellites orbiting the Earth and collecting frequent global observations for the benefit of mankind. Collaboration between NASA and organizations in the US and other countries has been extremely important in maintaining the Earth observation capabilities as well as collecting, organizing and managing the data. These collaborations have occurred in the form of: 1. NASA’s developing and launching spacecraft and instruments for operation by other agencies; 2. Instruments from collaborating organizations being flown on NASA satellites; and 3. Instruments from NASA being flown on satellites from collaborating organizations. In addition, there are collaborations such as joint science teams, data exchanges, and participation in international organizations to promote interoperability of various data systems. The purpose of this paper is to describe some of the Earth science data-related collaborative efforts in which NASA participates, and highlight a few results relevant to Earth system science research obtained through such collaborations.