A34A-01 INVITED
How Nature foiled the 2006 Hurricane forecasts.
In this study, we present new insights from NASA earth observing satellites (TRMM, MODIS, OMI/aura), and historical data to determine the root cause of the switch from the extremely active 2005 Atlantic hurricane season to the relatively mild 2006 season. Our results suggest that the increased loading of Saharan dust in the atmosphere over the Atlantic in 2006 compared to 2005, might have been instrumental, through the shielding of solar radiation at the ocean surface, in initiating rapid drop in SST in the West Atlantic/Caribbean region at the early stage of the hurricane season (June-July). Subsequently, the Caribbean cooling metastasized into a large- scale circulation regime shift in the tropical and subtropical Atlantic atmosphere-ocean through feedback processes, manifested in a Walker-type circulation anomaly with rising motion in the eastern tropical Atlantic and the sinking motion in the West Atlantic/Caribbean region. Associated with the shift was rapid cooling of sea surface temperature over the entire North Atlantic and suppressed hurricane activities. The cooling of the North Atlantic and the warming of the Gulf of Guinea in 2006 appeared to be contrary to the impacts of El Niño from past events. Analyses of historical data also show that Saharan dust has stronger influence than El Niño in the subtropical West Atlantic/Caribbean region, while El Niño influence may be stronger in the tropical eastern Atlantic. Including the pre- and early season effects of Saharan dust on SST cooling may be important in providing better seasonal hurricane predictions.
A34A-02 INVITED
Tropospheric Ozone Over North America
Ozone in the troposphere plays a significant role as an absorber of infrared radiation (greenhouse gas), in the cleansing capacity of the atmosphere as a precursor of hydroxol radical formation, and a regulated air pollutant capable of deleterious health and ecosystem effects. Knowledge of the ozone budget in the troposphere over North America (NA) is required to properly understand the various mechanisms that contribute to the measured distribution and to develop and test models capable of simulating and predicting this key player in atmospheric chemical and physical processes. Recent field campaigns including the 2004 and 2006 INTEX Ozone Network Studies (IONS) http:croc.gsfc.nasa.gov/intexb/ions06.html that have included intensive ozone profile measurements from ozonesondes provide a unique data set for describing tropospheric ozone over a significant portion of the North American continent. These campaigns have focused on the spring and summer seasons when tropospheric ozone over NA is particularly influenced by long-range transport processes, significant photochemical ozone production resulting from both anthropogenic and natural (lightning) precursor emissions, and exchange with the stratosphere. This study uses ozone profiles measured over NA in the latitude band from approximately 12-60N, extending from the tropics to the high mid latitudes, to describe the seasonal behavior of tropospheric ozone over NA with an emphasis on the spring and summer. This includes the variability within seasons at a particular site as well as the contrasts between the seasons. Emphasis is placed on the variations among the sites including latitudinal and longitudinal gradients and how these differ through the seasons and with altitude in the troposphere. Regional differences are most pronounced during the summer season likely reflecting the influence of a wider variation in processes influencing the tropospheric ozone distribution including lightning NOX production in the upper troposphere and active photochemistry from human emitted precursors in the lower troposphere. In all seasons, including the summer, transfer from the stratosphere significantly influences the upper tropospheric distribution at mid latitude (35-55N) locations. Although the seasonal maximum is found in spring in most locations and throughout much of the troposphere, this season tends to show less geographic variability compared to the summer. The FLEXPART Lagrangian tracer model is used to help identify processes associated with distinctive profile characteristics in the ozonesonde measurements.
A34A-03 INVITED
A Brief History of Infrared Limb Scanning
I shall give a brief and non-technical description of the development of this technique, in which I have been deeply involved. I think it makes an interesting story, and also illustrates some general principles. Limb scanning allows the detailed observation of the composition and structure of the upper troposphere and stratosphere. It began with some serendipitous consulting, went on to a speculative paper, and a successful proposal. However, things turned out to be more difficult than first imagined. A major technical barrier surfaced, but a breakthrough in data processing overcame it. After many smaller but no less challenging and interesting difficulties, there were some notable successes. After a brief look at the future, I'll close with some general thoughts.
A34A-04
The Partnership between Stratospheric Constituent Observations and Atmospheric Modeling
Predicting the future atmosphere and its sensitivity to perturbations is a grand challenge for atmospheric scientists. One focus over the past several decades has been the response of stratospheric ozone to variations in solar-ultraviolet radiation, volcanic aerosols, the exhaust of a possible fleet of supersonic aircraft, and changes in the atmospheric burden of man-made chlorofluorcarbons. The interplay between atmospheric models and stratospheric observations of constituents, especially from aircraft campaigns and the Upper Atmosphere Research Satellite, has led to an improved physical basis for the construction of models and more certainty in the predictions of future ozone evolution. Aura, the Earth Observing System platform focused on constituent observations, is providing new information to evaluate and improve models, especially in the lowermost stratosphere and upper troposphere. This talk will highlight comparisons of observations from Aura and other platforms with simulations from several three-dimensional models, emphasizing uncertainties in the simulations that are revealed by comparisons with observations and their relationship to uncertainty in prediction.
A34A-05 INVITED
Effects of Mount Pinatubo Volcanic Eruption on the Hydrological Cycle as an Analog of Geoengineering
Much of my work in recent years has been devoted to understanding the hydrological and energy cycles. The incoming radiant energy from the sun is transformed into various forms (internal heat, potential energy, latent energy, and kinetic energy) moved around in various ways primarily by the atmosphere and oceans, stored and sequestered in the ocean, land, and ice components of the climate system, and ultimately radiated back to space as infrared radiation. The requirement for an equilibrium climate mandates a balance between the incoming and outgoing radiation and further mandates that the flows of energy are systematic. The imbalance at top of atmosphere from increasing greenhouse gases from human activities creates warming. The central concern with geoengineering fixes to global warming is that the cure could be worse than the disease. The problem of global warming arises from the buildup of greenhouse gases such as carbon dioxide from burning of fossil fuels and other human activities that change the composition of the atmosphere. However, the solution proposed is to reduce the incoming sunshine by emulating a volcanic eruption. In between the incoming solar radiation and the outgoing longwave radiation is the entire weather and climate system and the operation of the hydrological cycle. The eruption of Mount Pinatubo in 1991 is used as an analog for the geoengineering and show that there was a substantial decrease in precipitation over land and a record decrease in runoff and streamflow in 1992, suggesting that major adverse effects, such as drought, could arise from such geoengineering solutions.