Past 2008 STAR Seminars

More than 400 tropical cyclones that occurred worldwide from 1999 through 2005 were examined. Changes in tropical cyclone behavior were observed using geostationary satellite imagery and archival data from the major tropical centers. The upper air environment was observed on satellite data, with emphasis on 6.7 micrometer water vapor imagery, and forecast model winds and temperatures between 500mb and 300mb. Seven categories of tropical cyclone behavior, such as turns and intensity changes were defined; and, 361 "events" were identified and analyzed. Likewise, 6 categories of changes in the upper air environment were defined; and, 376 "events" were identified from the tropical cyclone cases.

Specific types of changes in the upper air environment were found to be related to certain changes in tropical cyclone behavior. Two specific types of tropical cyclone cloud patterns were observed with weakening storms. Middle tropospheric dry air that arrived at the cold cloud shield boundaries of tropical cyclones at small angles and was ingested into the storms, was correlated with spiral shaped "intrusions" in the storm cloud pattern and weakening. Eye replacement cycles were also likely with this type of environmental change. Opening of adjacent upper air systems, that brought flow to the tropical cyclone cold cloud shields at large angles was correlated with cloud pattern deforming and weakening. Four types of environmental changes were well correlated with storm formations and intensification. Although the 153 right turns and 79 left turns were well related to specific categories of upper air changes, the relationships did not provide the quantitative information necessary for accurate track forecasting. However, specific categories of environmental changes related to turns were highly correlated with storm intensity changes during or after the turns. Relationships found in the study are likely to be useful in choosing model results, when various model forecasts diverge. Overall, changes in the adjacent upper air ridge and anticyclones made the greatest contributions to changes in tropical cyclone behavior. The eastward passages of short wave ridges in the westerlies, on the poleward side of storms, was found to be a particularly important type of environmental change affecting tropical cyclone behavior.

Accurate estimation of spatially distributed CO₂2 fluxes is of great importance for regional and global studies of carbon balance. We have found that in irrigated and rainfed crops (maize and soybean) as well as in grasslands, carbon dioxide exchange is closely related to total crop and grass chlorophyll content. The finding allowed development of a new technique for remote estimation of chlorophyll specifically for assessing carbon dioxide exchange / gross primary production (GPP). The technique is based on reflectance in two spectral channels: the near- infrared and either the green or the red-edge. The technique provided accurate estimations of daily carbon dioxide exchange. Validation using independent datasets for irrigated and rainfed maize and soybean documented the robustness of the technique. We report also about applying the developed technique for GPP retrieval from data acquired by both an airborne hyperspectral imaging spectrometer (AISA-Eagle) and ETM+ Landsat. The Chlorophyll Index, retrieved from Landsat ETM+ data, was found to be an accurate surrogate measure for daily carbon dioxide exchange with a root mean square error of GPP prediction of less than 1.58 g C m^-2d^-1 in a GPP range of 1.88 g C m^-2d^-1 to 23.1 g C m^-2d^-1. These results suggest new possibilities for analyzing the spatio- temporal variation of the GPP of crops using not only the extensive archive of Landsat Thematic Mapper imagery acquired since the early 1980s but also the 500-m/pixel data currently being acquired by MODIS.

The Geostationary Lightning Mapper (GLM) is a single channel, near-IR imager/optical transient event detector, used to detect, locate and measure total lightning activity over the full-disk as part of a 3-axis stabilized, geostationary weather satellite system. The next generation NOAA Geostationary Operational Environmental Satellite (GOES-R) series with a planned launch in 2014 will carry a GLM that will provide continuous day and night observations of lightning from the west coast of Africa (GOES-E) to New Zealand (GOES-W) when the constellation is fully operational. The mission objectives for the GLM are to 1) provide continuous, full-disk lightning measurements for storm warning and nowcasting, 2) provide early warning of tornadic activity, and 3) accumulate a long-term database to track decadal changes of lightning. The GLM owes its heritage to the NASA Lightning Imaging Sensor (1997-Present) and the Optical Transient Detector (1995- 2000), which were developed for the Earth Observing System and have produced a combined 13 year data record of global lightning activity. In parallel with the instrument development, a GOES-R Risk Reduction Team and Algorithm Working Group Lightning Applications Team have begun to develop the Level 2 algorithms and applications. Proxy total lightning data from the NASA Lightning Imaging Sensor on the Tropical Rainfall Measuring Mission (TRMM) satellite and regional test beds (e.g., Lightning Mapping Arrays in North Alabama and the Washington DC Metropolitan area) are being used to develop the pre-launch algorithms and applications, and also improve our knowledge of thunderstorm initiation and evolution. Real time lightning mapping data are being provided in an experimental mode to selected National Weather Service (NWS) forecast offices in Southern and Eastern Region. This effort is designed to help improve our understanding of the application of these data in operational settings.

Coral reefs live within a fairly narrow envelope of environmental conditions constrained by water temperatures, light, salinity, nutrients, bathymetry and the aragonite saturation state of seawater. As documented in numerous studies, the world’s coral reefs are "in crisis" as a result of human impacts on their environment. While local stresses currently dominate, coral reefs are increasingly confronted with global-scale changes due to rising greenhouse gas concentrations. These changes are rapidly modifying the environmental envelope of coral reefs through both increased thermal stress and ocean acidification. In the former case, there is a well-documented relationship between thermal stress and the response of corals that include coral bleaching, disease, and mortality. Clear tolerance thresholds exist beyond which high temperature and accumulated thermal stress have deleterious effects. However, the synergistic effects of increasing temperature and ocean acidification are not yet fully understood. At this time, there is mounting concern that decreasing pH and aragonite saturation state will cause net reef accretion to cease or become negative. The threshold at which this could occur is likely to be reached much sooner than the pH drop necessary to induce carbonate dissolution. Both the thermal and chemical limits that control coral survival and reef growth will likely be passed before 2100 assuming even conservative projections reported in the 4th Assessment Report of the Intergovernmental Panel on Climate Change. This talk, based in part on the review paper highlighted with the cover of Science on 14 December, will discuss these thresholds and their ramifications for ecosystems and resource management.

A strong and positive coupling between sea surface temperature (SST) and surface wind speed on scales shorter than about 1000 km is well established from satellite measurements of surface winds by the QuikSCAT scatterometer and SST by the Advanced Microwave Scanning Radiometer (AMSR). This ocean-atmosphere interaction is clearly evident in the ECMWF global forecast model, although it is underestimated by about a factor of two. The SST influence on surface winds is barely detectable in the NCEP global forecast model. Simulations with the Weather Research & Forecasting (WRF) mesoscale model suggest that this is due to a combination of inadequate resolution of the SST boundary condition used for the NCEP model and underestimation of vertical mixing in the marine atmospheric boundary layer.

CIOSS research is “on the edge” in a number of ways. First, by definition, all research occurs on the edge of knowledge. Next, considering spatial dimensions, remote sensing of the ocean occurs at the very top edge of the ocean, due to the strong absorption of electromagnetic radiation (EMR) by water. This is a major difference between oceanographic and atmospheric remote sensing. At CIOSS, we also have a focus on the horizontal edge of the ocean – the coastal environment. Several efforts are underway to push microwave (active and passive) remote sensing closer to the coast, where contamination of EMR signals is caused by reflection and emision from the land into the antenna side-lobes. Finally, some of our ocean color group work is with hyperspectral data, pushing at the edges of spectral and spatial resolution. Examples will be presented of ongoing research at CIOSS in all of these, with a special emphasis on retrieving altimeter data closer to the coast.

Warming climates have been widely recognized to advance spring vegetation phenology. However, the delayed responses of vegetation phenology to rising temperature and their mechanisms are poorly understood. To investigate seasonal variations in AVHRR NDVI from 1982 to 2005, we developed a sigmoidal model (describing vegetation seasonal growth) to fit the NDVI temporal trajectory which was used to identify vegetation phenology. Integrating AVHRR-based phenology and climate data during last 25 years, we revealed the mechanisms of diverse responses of vegetation phenology to climate changes in North America. From 40°N northwards, the decrease in chilling days by winter warming temperature has little impacts on spring thermal-time requirement for vegetation greenup onset. Thus, spring warming temperature has constantly advanced greenup onset by 0.32 days/year. However, from 40°N southward, the shortened winter chilling days are insufficient for fulfilling plant chilling requirement, so that the thermal-time requirement for greenup onset during spring increases gradually. Consequently, vegetation greenup onset changes progressively from an early trend to a later trend along the latitude transition zone from 40-31°N. The greenup onset is delayed by 0.15 days/year below 31°N. Finally, by combining phenology models, we found that warming climates trigger the poleward shift of phenological transition zone with a rate of 0.1 latitude degree per year.

Over 20 STAR scientists will be presenting oral and poster presentations at the 88th Annual AMS Meeting in New Orleans, LA during the week of January 20, 2008. Come see overviews of many of these talks at the various symposia in New Orleans next week.

The attitude (or orientation) of a Geostationary Operational Environmental Satellite (GOES) is maintained on orbit in two ways. One is to let the spacecraft spin rapidly, which creates a gyro effect through the conservation of angular momentum, hence the name spin-stabilization. The other is to stabilize the spacecraft in all three dimensions, or 3-axis stabilization, such that the spacecraft appears truly stationary relative to the earth. Stabilization of a spacecraft has profound impact on every aspect of its mission, including the calibration of instrument onboard the spacecraft. Earlier GOES, as well as all the FY-2 and METEOSAT, was stabilized by spinning. Current GOES (starting with GOES-8) achieved 3-axis stabilization. This talk is a brief review of calibration experience during the transition of this major configuration change, including the expectation and preparation before the change and lessons learned after. It is hoped that the experience could help the preparation for GOES-R, another major advance in GOES history.

NOAA has considered flying an ocean color imager on the next series of GOES satellites to address its needs for data to assess the state of and manage coastal ecosystems and fisheries. The Coastal Ocean Applications and Science Team (COAST) was formed by NOAA to assess the need and utility of measuring coastal ocean color from a geostationary satellite. The first COAST experiment was conducted in Monterey Bay September 3-15, 2006. The goal of this experiment was to collect data that exceeds all possible requirements for a geostationary ocean color imager so that the data may be binned spatially or spectrally to create a simulated data set for any possible set of requirements. For the Monterey Bay experiment we used the Florida Environmental Research Institute's (FERI) Spectroscopic Aerial Mapper with On-board Navigation (SAMSON). SAMSON collects a full hyperspectral dataset covering 256 bands in the VNIR (3.5 nm resolution over 380 to 970 nm range) at 75 frames per second. It is designed with a Signal-to-Noise Ratio (SNR), stability, dynamic range, and calibration sufficient for dark target spectroscopy. Monterey Bay was sampled at 5 m Ground Sample Distance (GSD) as frequently as every 30 minutes. At the time of the COAST experiment there was a large Harmful Algal Bloom in the North-East corner of Monterey Bay. Here we use the SAMSON data to describe the short term dynamics of that bloom. Driven by tides and currents the bloom was seen to move kilometers on a time scale of hours. There is also evidence of vertical migration with the bloom concentrating on the surface near noon.