Factors Influencing the Spatial and Temporal Distrubtion of Primary Productivity and Community Respiration in the Mississippi Coastal Estuarine Region

This study describes the spatial and temporal distribution of net primary productivity (NetPP) and respiration (RESP) in relation to the biogeochemical, optical, and hydrographic variability in the Mississippi Sound and Mississippi Bight over the course of one year. Surface in-situ measurements of NetPP and RESP were regularly determined at two stations by a time-course detection of dissolved oxygen (DO) using novel optode technology. In addition, various biogeochemical, optical, and hydrographic parameters were examined over 14 stations throughout the estuary over a year, using ground and satellite (MODIS Aqua) measurements. In this study, consistently low dissolved inorganic N:P ratios (average N:P \u3c 4.3 for all stations) suggest that rates ofNetPP were nitrogen limited, while the NetPP rates measured in the Mississippi Sound showed periodic growth limitation due to low watercolumn light availabi lity. Measured RESP rates were partially correlated to both allochthonous (POM, r2 = 0.78, p \u3c 0.01 , n = 20) and authochthonous (chlorophyll-a, r2 = 0.74, p \u3c 0.01 , n = 23) proxies for organic matter sources. There was also some evidence that ambient seasonal light levels may have driven some enhanced light-dependent respiration. Time and depth integrations ofNetPP and RESP indicate that net heterotrophic conditions persisted in Mississippi waters through most of the year, and that both integrated rates tended to be higher in the Mississippi Bight compared to the Mississippi Sound. As light availability appears to play an important role in regulating biological activity in this estuary, an empirical model (derived from multiple regression analysis) for predicting the down welling light attenuation coefficient [Kd(P AR)] is proposed for Mississippi waters. The model is based on contributing biogeochemical parameters [suspended particulate matter (SPM), chromophoric dissolved organic matter (CDOM), and chlorophyll-a] and the partitioning of each biogeochemical parameter using the empirical model reveals that SPM was the dominant contributor to Kd(P AR). However, relative contribution of SPM ( as well as values of Kd) diminished in the Mississippi Bight as the fraction of Particulate Inorganic Matter (PIM) to total SPM decreased. Finally, the extrapolation of biologically significant parameters to larger spatial scales via satellite remote sensing was assessed for the study area. Comparisons of measured chlorophyll-a, SPM, CDOM, Kd, euphotic depth (Zeu), and photosynthetically available radiation (PAR) to various products derived from the MODIS time-series showed high con-elations (r2 \u3e 0.8), with the exception of chlorophyll-a (r2 :S 0.6). Overall, a quasi-analytical algorithm (QAA) approach was better suited for measuring the distribution of light (i.e. Kd and Zeu) using satellite remote sensing methods in these optically complex waters, while simpler remote sensing reflectance (Rrs) and band ratios , tended to predict SPM and CDOM distribution better. The results of this study demonstrate that the drivers of biogeochemical variability as well as the balance between NetPP and RESP are determined by a multitude of factors

Caribbean Oceans: Utilizing NASA Earth Observations to Detect, Monitor, and Respond to Unprecedented Levels of Sargassum in the Caribbean Sea

In 2011 and 2015, the nations of the Caribbean Sea were overwhelmed by the unprecedented quantity of Sargassum that washed ashore. This issue prompted international discussion to better understand the origins, distribution, and movement of Sargassum, a free-floating brown macro alga with ecological, environmental, and commercial importance. In the open ocean, Sargassum mats serve a vital ecological function. However, when large quantities appear onshore without warning, Sargassum threatens local tourist industries and nearshore ecosystems within the Caribbean. As part of the international response, this project investigated the proliferation of this macro alga within the Caribbean Sea from 2003-2015, and used NASA Earth observations to detect and model Sargassum growth across the region. The Caribbean Oceans team calculated the Floating Algal Index (FAI) using Terra Moderate Resolution Imaging Spectroradiometer (MODIS) data, and compared the FAI to various oceanic variables to determine the ideal pelagic environment for Sargassum growth. The project also examined the annual spread of Sargassum throughout the region by using Earth Trends Modeler (ETM) in Clark Labs' TerrSet software. As part of the international effort to better understand the life cycle of Sargassum in the Caribbean, the results of this project will help local economies promote sustainable management practices in the region

Investigation of Colored Dissolved Organic Matter and Dissolved Organic Carbon Using Combination of Ocean Color Data and Numerical Model in the Northern Gulf of Mexico

The first part of this thesis includes evaluating and developing empirical band ratio algorithms for the estimation of colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) for SeaWiFS, MODIS and MERIS ocean color sensors for the northern Gulf of Mexico. For CDOM, matchup comparison between SeaWiFS-derived CDOM absorption coefficients and in situ absorption measurements at 412 nm (aCDOM(412)) were examined using the D’Sa et al. (2006) and the Mannino et al. (2008) algorithms. These reflectance band ratio algorithms were also assessed to retrieve aCDOM(412) from MODIS and MERIS data using the Rrs(488)/Rrs(555) and Rrs(510)/Rrs(560) band ratios, respectively. Since DOC cannot be measured directly by remote sensors, CDOM as the colored component of DOC is utilized as a proxy to estimate DOC remotely. A seasonal relationship between CDOM and DOC was established for the summer and spring-winter with high correlation for both periods. Seasonal band ratio empirical algorithms to estimate DOC were thus developed. In the second part of this study, a numerical model to study CDOM dynamics in the northern Gulf of Mexico was examined. To derive surface CDOM concentration maps from simulated salinity output from the Navy Coastal Ocean Model (NCOM), a highly correlated linear inverse relationship between CDOM and salinity is required which was examined for both inner-shelf and outer-shelf areas for the spring-winter and the summer periods. Applying these relationships on NCOM simulated salinity resulted in hourly maps of CDOM exhibiting high consistency with CDOM patterns derived from SeaWiFS sensor. Overlaying the NCOM-derived CDOM maps on the simulated currents showed the profound effect of currents on CDOM advection. Cold fronts strongly impact CDOM advection in both the inner and outer shelves by flushing CDOM-laden waters out of the coastal bays

SeaWiFS technical report series. Volume 6: SeaWiFS technical report series cumulative index: Volumes 1-5

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is the follow-on ocean color instrument to the Coastal Zone Color Scanner (CZCS), which ceased operations in 1986, after an eight year mission. SeaWiFS is expected to be launched in August 1993, on the Sea Star satellite, being built by Orbital Sciences Corporation (OSC). The SeaWiFS Project at the NASA/Goddard Space Flight Center (GSFC) has undertaken the responsibility of documenting all aspects of this mission, which is critical to the ocean color and marine science communities. This documentation, entitled the SeaWiFS Technical Report Series, is in the form of NASA Technical Memoranda Number 104566. All reports published are volumes within the series. This volume serves as a reference, or guidebook, to the previous five volumes and consists of four main sections including an index to key words and phrases, a list of all references cited, and lists of acronyms and symbols used. It is our intention to publish a summary index of this type after every five volumes in the series. This will cover the topics published in all previous editions of the indices, that is, each new index will include all of the information contained in the preceding indices

Estimation of aboveground terrestrial net primary productivity and analysis of its spatial and temporal trends in the conterminous United States from 1997 to 2007 using NASA-CASA model

This study estimated monthly and annual Net Primary Productivity (NPP), an important indicator of carbon sequestration, in the Conterminous US from 1997 to 2007 using Carnegie-Ames-Stanford Approach. Vegetation condition, temperature, precipitation, photosynthetically active radiation and soil water holding capacity were used as model’s inputs. NPP values were lower than mean annual values during the year 2000 to 2003 which was probably due to extreme drought conditions during these years. Higher NPP per square meter was generally found in Savannah and Subtropical eco-divisions whereas Tropical/Subtropical deserts had the lowest NPP. Southeastern states had the highest NPP per square meter thus, made the highest contribution to the terrestrial carbon sequestration in US. Since the vegetation is one of the main factors in NPP and thus carbon sequestration, the results of this study could help in various environmental policy decisions on forest and cropland management at the state, EPA and federal levels

Improving Land Surface Modeling Using Satellite and Field Observation Data for a Meteorology and Air Quality Modeling System

Ingesting MODIS satellite derived leaf area index (LAI), fraction of absorbed photosynthetically active radiation (FPAR), and albedo into the Pleim-Xiu (PX) land surface model (LSM) in the combined meteorology and air quality modeling system WRF/CMAQ, composed of the Weather Research and Forecast (WRF) model and Community Multiscale Air Quality (CMAQ), adds realism to the system especially for vegetation fractional coverage in western drylands because the PX LSM intentionally exaggerates vegetation coverage in these sparsely vegetated areas for more effective soil moisture nudging for surface temperature and water vapor mixing ratio estimations. Initial simulations with realistic MODIS vegetation show mixed results with greater error and bias in daytime temperature and greater high bias for ozone concentrations but reduced error and bias in moisture over the western arid regions. Incorporating yearlong MODIS input into an updated WRF/CMAQ with recent improvements in vegetation, soil, and boundary layer processes results in improved 2 m temperature (T) and mixing ratio (Q), 10 m wind speed, and surface ozone simulations across the U.S. WRF/CMAQ 12km domain compared to the initial simulations. Yearlong MODIS input helps reduce bias of the 2 m Q estimation during the growing season from April to September. Improvements follow the green up in the southeast from April and move towards the west and north through August. A coupled photosynthesis-stomatal conductance model with two-big leaf canopy scaling (PX PSN) is developed for the PX LSM in a diagnostic box model. The PX PSN shows distinct advantages in simulating latent heat over landscapes with short vegetation such as grassland and cropland. The advanced approach performs exceptionally well in simulating ozone deposition velocity and flux while the current PX approach significantly overestimates.Doctor of Philosoph

SeaWiFS technical report series. Volume 12, SeaWiFS technical report series cumulative index: Volumes 1-11

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is the follow-on ocean color instrument to the Coastal Zone Color Scanner (CZCS), which ceased operations in 1986, after an 8-year mission. SeaWiFS is expected to be launched in 1994, on the SeaStar satellite, being built by Orbital Sciences Corporation (OSC). The SeaWiFS Project at the National Aeronautics and Space Administration's (NASA) Goddard Space Flight Center (GSFC) has undertaken the responsibility of documenting all aspects of this mission, which is critical to the ocean color and marine science communities. This documentation, entitled the SeaWiFS Technical Report Series, is in the form of NASA Technical Memorandum Number 104566. All reports published are volumes within the series. This particular volume serves as a reference, or guidebook, to the previous 11 volumes and consists of 6 sections including: an errata, an addendum (a summary of the SeaWiFS Working Group Bio-optical Algorithm and Protocols Subgroups Workshops), an index to keywords and phrases, a list of all references cited, and lists of acronyms and symbols used. It is the editors' intention to publish a cumulative index of this type after every five volumes in the series. This will cover the topics published in all previous editions of the indices, that is, each new index will include all of the information contained in the preceding indices

SeaWiFS calibration and validation plan, volume 3

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) will be the first ocean-color satellite since the Nimbus-7 Coastal Zone Color Scanner (CZCS), which ceased operation in 1986. Unlike the CZCS, which was designed as a proof-of-concept experiment, SeaWiFS will provide routine global coverage every 2 days and is designed to provide estimates of photosynthetic concentrations of sufficient accuracy for use in quantitative studies of the ocean's primary productivity and biogeochemistry. A review of the CZCS mission is included that describes that data set's limitations and provides justification for a comprehensive SeaWiFS calibration and validation program. To accomplish the SeaWiFS scientific objectives, the sensor's calibration must be constantly monitored, and robust atmospheric corrections and bio-optical algorithms must be developed. The plan incorporates a multi-faceted approach to sensor calibration using a combination of vicarious (based on in situ observations) and onboard calibration techniques. Because of budget constraints and the limited availability of ship resources, the development of the operational algorithms (atmospheric and bio-optical) will rely heavily on collaborations with the Earth Observing System (EOS), the Moderate Resolution Imaging Spectrometer (MODIS) oceans team, and projects sponsored by other agencies, e.g., the U.S. Navy and the National Science Foundation (NSF). Other elements of the plan include the routine quality control of input ancillary data (e.g., surface wind, surface pressure, ozone concentration, etc.) used in the processing and verification of the level-0 (raw) data to level-1 (calibrated radiances), level-2 (derived products), and level-3 (gridded and averaged derived data) products

Investigating the Eco-Hydrological Impact of Tropical Cyclones in the Southeastern United States

<p>Tropical Cyclones (TCs) intensity and frequency are expected to be impacted by climate change. Despite their destructive potential, these phenomena, which can produce heavy precipitation, are also an important source of freshwater. Therefore any change in frequency, seasonal timing and intensity of TCs is expected to strongly impact the regional water cycle and consequently the freshwater availability and distribution. This is critical, due to the fact that freshwater resources in the US are under stress due to the population growth and economic development that increasingly create more demands from agricultural, municipal and industrial uses, resulting in frequent over-allocation of water resources. </p><p>In this study we concentrate on monitoring the impact of hurricanes and tropical storms on vegetation activity along their terrestrial tracks and investigate the underlying physical processes. To characterize and monitor the spatial organization and time of recovery of vegetation disturbance in the aftermath of major hurricanes over the entire southeastern US, a remote sensed framework based on MODIS enhanced vegetation index (EVI) was developed. At the SE scale, this framework was complemented by a water balance approach to estimate the variability in hurricane groundwater recharge capacity spatially and between events. Then we investigate the contribution of TCs (season totals and event by event) to the SE US annual precipitation totals from 2002 to 2011. A water budget approach applied at the drainage basins scale is used to investigate the partitioning of TCs' precipitation into surface runoff and groundwater system in the direct aftermath of major TCs. This framework allows exploring the contribution of TCs to annual precipitation totals and the consequent recharge of groundwater reservoirs across different physiographic regions (mountains, coastal and alluvial plains) versus the fraction that is quickly evacuated through the river network and surface runoff. </p><p>Then a Land surface Eco-Hydrological Model (LEHM), combining water and energy budgets with photosynthesis activity, is used to estimate Gross Primary Production (GPP) over the SE US The obtained data is compared to AmeriFlux and MODIS GPP data over the SE United States in order to establish the model's ability to capture vegetation dynamics for the different biomes of the SE US. Then, a suite of numerical experiments is conducted to evaluate the impact of Tropical Cyclones (TCs) precipitation over the SE US. The numerical experiments consist of with and without TC precipitation simulations by replacing the signature of TC forcing by NARR-derived climatology of atmospheric forcing ahead of landfall during the TC terrestrial path. The comparison of these GPP estimates with those obtained with the normal forcing result in areas of discrepancies where the GPP was significantly modulated by TC activity. These areas show up to 10% variability over the last decade.</p>Dissertatio

Inferring Radiative Fluxes from a New Generation of Satellites: Model Updates

In this study an inference scheme is developed to derive surface, Top of the Atmosphere (TOA), and atmospheric spectral shortwave (SW) radiative fluxes for implementation with observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) type of sensors. The model takes into account all atmospheric constituents and addresses the characteristics of water and ice clouds and the variation of cloud particle effective radius. The near infrared spectrum is divided into three bands to better represent the spectral variation of cloud optical properties and water vapor absorption. A multi-layered structure allows for the treatment of surface elevation effects and for the representation of the vertical distribution of the radiative fluxes. Spectral fluxes such as Photosynthetically Active Radiation (PAR) and near-infrared radiation (NIR) are also estimated. The new inference scheme is implemented with MODIS one degree products as well as with the 5 km swath products. The derived fluxes are evaluated against the globally distributed Baseline Radiation Network (BSRN) measurements and compared with products from independent satellites. It was demonstrated that the MODIS products are in good agreement with ground observations and provide improved estimates of radiative fluxes than the other evaluated satellite products. In problematic areas for most satellite retrievals, such as the Tibet Plateau and Antarctica, the MODIS results have shown a substantial improvement. Availability of the high resolution swath based estimates of surface radiative fluxes allow, for the first time, to address unique space-time coupling issues