OS34A-01 INVITED
Multi-sensor Satellite Analysis of Upper Ocean Response Before and After Coastally Trapped Disturbances
Along the central California coast, periods of coastal upwelling forced by northerly winds may be followed by wind reversals that lead to cloud clearing periods that may last for several days. This study seeks to understand the upper ocean response between these periods of clear and cloudy conditions through use of multiple sensors including MODIS, which provides sea surface temperature and ocean color, and microwave imagery from synthetic aperture radar (SAR). Wide-swath SAR acquisitions were obtained from both RADARSAT1 and Envisat ASAR, along with MODIS and GOES imagery during such a wind reversal event that took place in early September 2005. We will discuss how the radar backscatter response is related to variations in temperature and ocean productivity and how the backscatter may be used to interpret the upper ocean changes during the wind reversal events. Quantitative comparisons and correlative relationships between the backscatter, and temperature and ocean color parameters will be presented.
OS34A-02
Multi-Sensor Satellite Data Records for Climate Applications: Issues and Lessons Learned During Reanalysis of Historical AVHRR Data
The satellite observations are unique source of information about the ocean, surface and atmosphere. To be useful for climate studies, these data must be processed in the most accurate way to ensure consistency of long- time series. Although there are number of various satellite missions designed for climate applications, the optical data from medium resolution satellite sensors, such as Advanced Very High Resolution Radiometer (AVHRR) on NOAA platforms, play a central role. They deliver time series of the longest duration and global spatial coverage. The paper describes the efforts carried out at the Canada Centre for Remote Sensing (CCRS) on developing satellite data records suitable for climate applications. The archive of 25 years (since 1981) of observation from AVHRR/NOAA at 1-km spatial resolution, followed by MODerate Resolution Imaging Spectroradiometer (MODIS) on Terra platform at 250-m spatial resolution has been generated at CCRS over the large area of North America. Some critical issues were identified during re-analysis of AVHRR data. The consistency of radiometric calibration provided from various sources for all AVHRR sensors since AVHRR/NOAA-6 is analyzed. A calibration approach using the tropical deep convective clouds as the calibration target is described and evaluated. The uncertainties related to the choice of solar reference spectrum and sensor's spectral response functions are quantified. Details of newly designed cloud detection scheme are presented. It is emphasized that detection of cloud shadows should be an integral component of the scene identification process to identify truly clear-sky pixels. Some examples of long term trends in Western Arctic sea-ice extent, albedo and radiation will be discussed that demonstrate rate of climate change in high Arctic region. This work has been supported by the Canadian Space Agency under the Government Related Initiatives Program (GRIP) and the Earth Sciences Sector of the Department of Natural Resources Canada under the Program on "Enhancing Resilience in a Changing Climate".
OS34A-03 INVITED
Progress and Pitfalls in Satellite Surveillance of Loop Current Frontal Eddy Cyclones
In the last decade, significant advances in active and passive remote sensing have transpired that are enabling
researchers to better quantify and model time and space scales of ocean processes. This paper presents recent
attempts to track the motion and development of rapidly propagating cyclonic mesoscale eddies along the outer
margin of the Loop Current in the Gulf of Mexico. Recent research has shown the critical role that these features
play in the intensification of surface currents and as trigger mechanisms for deep flows in oil and gas producing
areas in the northern Gulf of Mexico. The rapid motion of these cyclonic frontal features (35 km/day) has made
their study problematic.
In this paper, we discuss the use of several remote sensing systems and the integration of data from these
systems to better understand the behavior and impacts of the frontal eddy cyclones on Gulf circulation processes.
Mid-infrared (3.5-3.9 micron) measurements from GOES GVAR, available in real-time every 15 minutes over the
Gulf, provide an excellent source of "de-clouded" night-time surface temperature information, from which sea
surface temperatures (SST) are estimated with daily updates (http:www.esl.lsu.edu). Measurements in this
atmospheric window maximize the sampling frequency of ocean information in cloudy and humid ocean regions
such as the Gulf of Mexico. On the other hand, satellite altimetry measurements provide the only remote sensing
technique that directly measures a dynamical variable of ocean state - the sea surface height (SSH). Detection of
mesoscale eddies has been improved by combining multi-mission measurements from TOPEX-Poseidon, ERS-
2, GFO, Jason-1 and Envisat into a gridded product, updated daily (http:argo.colorado.edu/~realtime/welcome).
Ocean color sensors (SeaWiFS, MODIS, Oceansat-1 OCM) provide surface pigment information (chlorophyll a,
CDOM) that can aid in the discrimination of Gulf features as cold core eddies contain more chlorophyll a, due to
the upwelling of nutrients.
In our attempt to characterize the behavior of these dynamic mesoscale features and their impacts on circulation,
we present several case studies which showcase our progress as well as potential problems associated with
these sensors. We present new results on air-sea interaction and hurricane intensity changes over Gulf eddies
as well as the impacts of eddies on surface and sub-surface current accelerations in deep water.
http:www.esl.lsu.edu/research/
OS34A-04
Multi-Year Optical Variability in the Northern Gulf of Mexico: Impact of Atmospheric and Oceanic Forcing
One of the main advantages of a data base of archived satellite imagery is the ability to examine consistent products over several years, to assess long-term variability. The distributions of bio-optical properties are influenced by atmospheric and oceanic forcing through local and remote processes. We examine the impact of winds, waves, precipitation, and river discharge on coastal optical properties in the northern Gulf of Mexico, to assess the response of the optical fields to the forcing. We also couple the ocean color imagery with a numerical circulation model (HYCOM), with the ultimate goals of improving our understanding of the linkages between the physical forcing and the optical response, and providing a short-term predictive capability (1-3 day time scale) for ocean optics. We have assembled a complete 5-year data base of ocean color imagery (SeaWiFS, MODIS) covering the Gulf of Mexico (2001-2005). We have reprocessed all the imagery with consistent atmospheric correction and bio-optical algorithms to produce a full suite of optical products, including remote sensing reflectances, absorption (partitioned) and backscattering coefficients, chlorophyll concentration, total suspended sediment concentration (partitioned into organic and inorganic components), and new optical water mass classification images. We have also constructed data bases of winds (from buoys in the northern Gulf of Mexico), rainfall (from the TRMM satellite), and river discharge (USGS stream flow data) corresponding to the time period covered by the imagery. We present quantitative, statistical, time-series analyses to characterize the spatial/temporal changes in the water mass optical properties over time and how they relate to the physical forcing in the northern Gulf of Mexico. A frequency analysis using monthly optical water mass classification images provides an indication of the expected seasonal spatial distributions of optical water types. We also present examples of predicted optical fields (derived by coupling ocean color imagery with the numerical circulation model).
OS34A-05
Global 9 km multi-satellite, multi-sensor sea surface temperatures from MODIS, AMSR-E, and TMI
Current global sea surface temperature (SST) datasets do not take full advantage of the numerous satellites and
different sensors now retrieving SST. Existing operational SST products depend on a single sensor to produce
global datasets. This results in a lower spatial and temporal resolution than what is possible with a multi
satellite, multi sensor SST analysis. Initial efforts indicate that blending data from different sensors requires
much more rigorous bias and error characterization than is necessary when only including data from a single
sensor type. Therefore, creating a high-quality multi-sensor SST requires careful inter-calibration of different
satellite sensors, calculation of sensor-specific observation errors that consider environmental variables, location
of observation, and sensor calibration problems; and development of techniques for relating and combining
measurements at different spatial resolutions and times of the day. A global daily 9 km optimally interpolated
SST has been calculated from MODIS, AMSR-E and TMI SST data. Initial methodology, validation results, and
future work will be discussed. This improved global daily SST should be useful for a wide range of scientific and
operational activities.
http:www.misst.org
OS34A-06
Oceanic Aerosol Network: A Maritime Component of AERONET
We suggest the establishment of the Oceanic Aerosol Network as a new component of the Aerosol Robotic Network (AERONET) that adheres to AERONET calibration and processing. Climate change studies, atmospheric correction of the satellite data, satellite data validation, and aerosol modeling creates a strong demand for new data acquisition. Ship-based measurements can at least partly fill the gap in our knowledge on the global aerosol distribution over the oceans and complement island-based AERONET sites. We plan to reestablish NASA's ship-based aerosol optical depth measurement network by deploying hand-held sun photometers on various ships of opportunity; developing an archival system, similar to the AERONET browser, but specifically designed for "moving" objects (i.e., ships); developing a calibration protocol; developing stand alone processing, utilizing AERONET's Version 2 algorithm; and developing a centralized archiving and distribution system allowing for public domain, web-based access. The suggested Oceanic Aerosol Network (AERONET - OAN) will provide important information for the Ocean Color community as well as global ocean and global climate studies.
OS34A-07
Unusual blooms of Noctiluca miliaris in the Arabian Sea during the Northeast Monsoon
Until the late 1990's Noctiluca miliaris Suriray (synonym Noctiluca scintillans Macartney), a large
heterotrophic dinoflagellate was a minor component of phytoplankton populations in the Arabian Sea, appearing
in bloom form only sporadically in coastal regions predisposed to upwelling and deep slope water intrusions
during the Southwest monsoon. Since then however, N. miralis blooms have increased in frequency and
intensity, but with the majority of blooms being observed following the Northeast monsoon (NEM) and at times, in
association with the well known blooms of the diazotroph Trichodesmium sp. Microscopy and
chemotaxonomy from HPLC analysis of phytoplankton pigments undertaken in 2003-2004. as well as satellite
ocean color data suggest that N. miralis blooms are becoming more intense and widespread in the Arabian
Sea. Large blooms of these organisms have started appearing in the Gulf of Oman and off the coast of Oman.
This study uses recent, merged SeaWiFS and MODIS-Aqua ocean color datasets to investigate the temporal
evolution and spatial extent of these taxonomically validated blooms. Aqua-MODIS SST and altimetry data
suggest that mesoscale eddies that populate the Western Arabian Sea during the NEM may be playing a
significant role in the production and dispersal of these blooms from the Gulf of Oman into the Central Arabian
Sea.
http:www.bigelow.org/climatechange
OS34A-08
A Multi-frequency Beam-forming HF Radar for Tsunami Detection
We discuss a new multi-frequency beam-forming HF radar design for robust detection and tracking of tsunami
waves from 200 km distances, providing continuous coverage of the tsunami wave pattern after it impinges on the
continental shelf. The method works by mapping ocean currents at long range using traditional HF radar method
of radial Bragg line Doppler shift measurements. The tsunami is detected by anomalous spatial patterns of
higher than normal Bragg-line shifts due to the large orbital wave of the series of tsunami wave crests as they
impinge on the continental shelf. An approach using beam forming of 16 or 32 antenna elements provides an
update every five minutes or less, while Direction-of-Arrival method systems using just a few antenna elements
inherently require of the order of 30 to 60 minutes for a reliable current map.
The multi-frequency radar provides a more robust capability than the single frequency HF radar for at least two
reasons. First, because the HF channel user spectrum suffers diurnal variability in channel occupancy due to the
ionosphere changing with time of day, low frequencies can become contaminated with user noise, so that
maximum range for reliable detection not achieved. Under this condition, one would rely on quiet higher HF
frequencies that lie above the Maximum Usable Frequency (MUF) for ionospheric reflection propagation.
Alternatively, for daylight operation when low frequency utilization can be used to minimize surface wave
propagation loss, the sea state might not be sufficiently active to allow long range coverage needed for reliable
detection, due to the lack of ocean wave spectral energy at the Bragg-resonant wave frequency. Thus, single-
frequency radars, operating in the 4-6 MHz range to minimize propagation losses to achieve long-range coverage,
would suffer due to low wind conditions. The multi-frequency HF radar discussed here allows one to dynamically
choose the optimum frequency from a set of 8 to 16, as allowed by local radio frequency allocation authorities,
assuming just a single frequency is used at a time. Alternatively, one may choose four to eight frequencies
operating simultaneously, to allow the clearest channel and best signal strength channel for enhanced
processing. We will discuss the tradeoffs on multiple frequency use versus single optimum frequency use, both
using a multi-frequency radar capability. Results of preliminary testing of a prototype system at Duck, NC will also
be presented.
http:www.isr-sensing.com