James G. Acker

Online analysis enhances use of NASA Earth science data

Giovanni, the Goddard Earth Sciences Data and Information Services Center (GES DISC) Interactive Online Visualization and Analysis Infrastructure, has provided researchers with advanced capabilities to perform data exploration and analysis with observational data from NASA Earth observation satellites. In the past 5–10 years, examining geophysical events and processes with remote-sensing data required a multistep process of data discovery, data acquisition, data management, and ultimately data analysis. Giovanni accelerates this process by enabling basic visualization and analysis directly on the World Wide Web. In the last two years, Giovanni has added new data acquisition functions and expanded analysis options to increase its usefulness to the Earth science research community.

Seasonal Variations of Chlorophyll

Monthly climatology of chlorophyll concentration (chl ) based on nine years of SeaWiFS data is used to illustrate seasonal variations and spatial structures in the northern South China Sea (SCS). Chl starts to increase in September at the northern coast of Luzon Island, continues to increase in the autumn, and reaches its maximum in December or January. Maximum chl is centered in the northern SCS off the northwestern coast of Luzon Island. Chl starts to decrease gradually in February, and its values become very low from June to August. The region of elevated chl during the winter bloom season is funnel shaped, with the narrow end at the northern coast of Luzon Island, where the chl value is highest and opening toward the northwest. The sea surface temperature (SST) in this funnel-shaped region is significantly colder than SST in surrounding regions of the same latitude. The present study indicates that the winter blooms indicated by higher chl and colder SST in the northern SCS are linked strongly to the local winter monsoon. The initial data exploration and analysis presented in this study was carried out using Giovanni, a state-of-the-art Web-based data analysis and visualization tool.

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The Sea-viewing Wide Field-of View Sensor (SeaWiFS) Mission has initiated a new era of ocean color remote sensing and has established performance benchmarks that will be emulated by subsequent missions. An integral element of the SeaWiFS mission is the data component, performed by the Goddard Earth Sciences Distributed Active Archive Center (GES DAAC), NASA Goddard Space Flight Center, Greenbelt, MD. Since the beginning of data distribution in September 1997, the GES DAAC has managed the data archive and improved data distribution capability. SeaWiFS data products are archived in a primary, secondary, and tertiary archive structure, ensuring data preservation. Data distribution utilizes a World Wide Web (WWW)-based ordering interface, allowing distribution either electronically or on magnetic tape media. Automatic data subscriptions, supplying user-tailored data product selections, have yielded a high archive-to-distribution ratio. System improvements have increased efficiency and redundancy. The user interface has added features designed to facilitate data access and data usage, enhanced by WWW information resources and comprehensive online dataset documentation. As SeaWiFS enters the latter half of its five-year mission, a system performance assessment provides useful information for other Earth remote sensing missions and allows consideration of future usage objectives for the SeaWiFS data archive.

Concentration in the Northern South China Sea

When Hurricane Katrina passed over southern Florida, Florida Bay and the West Florida Shelf, and into the Gulf of Mexico, empirically derived chl a increases were observed in the Tortugas Gyre circulation feature, and in adjacent waters. Analysis of the empirically derived chl a increase within the gyre has been primarily attributed to initiation of a phytoplankton bloom promoted by nutrients upwelled by Katrinas winds. Detailed analysis of inherent optical properties derived from remotely sensed radiances, however, indicated the interaction of Katrina with shallow coastal and shelf waters likely entrained waters with higher concentrations of chromophoric dissolved organic matter (CDOM) into the gyre circulation, augmenting the chl a signal. Storm-induced upwelling would also transport optically active CDOM to the surface. Increases in empirically derived chl a in the Florida coastal waters influenced by Katrinas winds were therefore partly due to increased absorption by CDOM. This analysis indicates that elevated empirically derived chl a in hurricane-influenced waters should not be unambiguously attributed to increased phytoplankton productivity, particularly in an optically complex coastal environment.

SeaWiFS ocean color data archive and distribution system: assessment of system performance

Abstract: The NASA Giovanni data analysis system ha s been recognized as a useful tool to access and analyze many different types of remote sensing data. The variety of environmental data types has allowed the use of Giovanni for different application areas, such as agriculture, hydrology, a nd air quality research. The us e of Giovanni for researching connections between public health issues and Earth’s environment and climate, potentially exacerbated by anthropogenic influence, has been increasingly demonstrated. In this communication, the pertinence of several different data parameters to public health will be described. This communication also provides a case study of the use of remote sensing data from Giovanni in assessing the associations between seasonal influenza and meteorological parameters. In this study, logistic regression was employed with precipitation, temperature and specific humidity as predictors. Specific humidity was found to be associated ( p < 0.05) with influenza activity in both temperate and tr opical climate. In the two temperate locations

Interaction of Hurricane Katrina With Optically Complex Water in the Gulf of Mexico: Interpretation Using Satellite-Derived Inherent Optical Properties and Chlorophyll Concentration

In 1858, less than two decades after the invention of daguerrotype photography, a photograph of Paris was taken from a balloon. This event is generally recognized as the first demonstration of “remote sensing.” The use of aerial photography was attempted soon afterward during the Civil War in the United States, and this effort demonstrated that balloons were both useful observational platforms and easily recognizable targets. Photographs from balloons at higher altitude, kites, airplanes, and even pigeons were acquired in subsequent years, with an emphasis on military applications, particularly during the two world wars. The idea of photographing the earth from space, however, was apparently first described for nonmilitary applications by Dr. Harry Wexler at a symposium held at the Hayden Planetarium in New York in 1954. Dr. Wexler included a sketch of what a satellite camera 4000 miles over Texas might observe. In 1957 (the International Geophysical Year), President Dwight Eisenhower announced Project Vanguard, which would orbit several earth-observing satellites. Although numerous Vanguard launches failed, Vanguard 2, launched on February 17, 1959, carried a cloud-cover observation experiment, but satellite wobble prevented the acquisition of useful imagery. The first U.S. satellite, Explorer 1, which launched on January 31, 1958, carried Geiger counters provided by Dr. James Van Allen. The Geiger counter data indicated the existence of the Van Allen radiation belts, the first geophysical discovery made by satellites. Vanguard mission SLV-6, launched on June 22, 1959, carried a radiation balance experiment created by Verner Suomi, but the mission failed to reach orbit. However, Explorer VII, launched on October 13, 1959, carried a similar experiment, and this mission provided the first measurement of the solar constant and the first longwave radiation budget map of the earth.

Use of the NASA Giovanni Data System for Geospatial Public Health Research: Example of Weather-Influenza Connection

Blizzards, floods, droughts, and heat waves from January to July 2010 brought into sharp focus a primary expected manifestation of global climate change: significant alteration of Earths hydrological cycle. Increased numbers of extreme events, and longer-term and larger-scale precipitation pattern shifts that will stress both natural ecosystems and human societal norms, are anticipated as consequences of this alteration. For 25 years, NASA has orbited satellite sensors providing data on Earths interconnected energy and hydrologic systems; new missions for this purpose are scheduled to launch in coming years, including the Global Precipitation Measurement mission in 2013. These missions, and complementary studies, have produced large and steadily increasing volumes of data, either archived at NASA data centers or held by investigators, particularly those in the NASA Energy and Water Cycle Study (NEWS) program. This increasing volume has induced a data management dilemma: Investigators encounter an increasingly complex process to locate, access, and utilize such data, especially when seeking to combine heterogeneous data sets for innovative research.

Remote Sensing from Satellites

The Ocean Color Time-Series Project based at NASA Goddard Space Flight Center (NASA GSFC) will produce a multi-decade ocean color dataset by combining data from the Coastal Zone Color Scanner (1978-1986), the Ocean Color and Temperature Scanner (1996-1997), the Sea-viewing Wide Field-of-view Sensor (1997-present) and the Moderate Resolution Imaging Spectroradiometer (2002-present) on the Aqua satellite. The ocean color time-series products can potentially be extended to data acquired by sensors on the operational National Polar Orbiting Environmental Satellite System (NPOESS). The use of these data sets is facilitated by the Laboratory for Ocean Color Users (LOCUS). LOCUS is hosted by the Goddard Earth Sciences Data and Information Services Center (GES DISC) and features “Giovanni”, the GES DISC Interactive Online Visualization and Analysis Infrastructure. The easy-to-use interface and rapid functionality of Giovanni allows users to perform basic data analyses on global ocean color data products. Giovanni requires only a World Wide Web browser for the performance of sophisticated data analysis and the creation of publication-ready numerical and graphic output. LOCUS provides a framework through which professors, teachers, and students can fully utilize ocean color time-series data and Giovanni. Full development of LOCUS includes tutorials which demonstrate examples of research projects; an extensive online user’s manual of Giovanni functions; educational modules which discuss fundamental oceanographic concepts utilizing interactive data analysis exercises; concept-to-completion guidelines for the creation of independent investigational research projects; and a user forum that allows scientists and data professionals to interact with LOCUS participants on their particular research programs.