Hosted by: Andrew Vogelmann

Aerosol monitoring has been conducted at Patras, Greece, an urban area in the Eastern Mediterranean with population near 200,000, for a four year period from December, 2008 to May, 2012. The study was motivated by Greek EPA's results that showed Patras exceeding both daily and annual European Union PM10 (particulate matter with diameter smaller than 10 μm) standards, despite the city's small size and lack of heavy industry. As the Eastern Mediterranean is underrepresented in both the recent month-long aerosol characterization studies conducted over Europe (EUCAARI, MEGAPOLI) and in the European supersite networks dedicated to aerosol research (EUSAAR, ACTRIS), this monitoring also fills an important gap in coverage. Transport from continental Europe and Asia was found to be the dominant source of PM2.5 mass throughout the year accounting for approximately 70%, except during winter when the contribution decreased to 50%. This continental transport typically included almost all of the sulfates and 40-90% of the organic aerosol. During winter, sharp nighttime increases of the PM2.5 mass concentration were observed, with organic aerosol sometimes exceeding 80 μg m-3. Fossil fuel and local biomass combustion emissions for domestic heating were responsible for these levels. A comparison of Patras with different population density environments will also be discussed.

Hosted by: Jian Wang

Atmospheric new particle formation has been found to be closely related to the formation of cloud condensation nuclei, and therefore can cast large uncertainties in global climate modeling. Atmospheric measurements have been carried out all over the world during the last few decades. Nucleation rates and growth rates of newly formed particles in the atmospheric boundary layers are shown to be positively correlated to the sulfuric acid concentration. However, these observed fast rates usually cannot be explained by sulfuric acid alone. In this work, a new conceptual model for nucleation in the polluted atmospheric boundary layers and a novel method of estimating particle growth rates after they are formed are introduced. These results are based on measurements from both a field study and a laboratory chamber study with recently developed instruments of the cluster chemical ionization mass spectrometer (Cluster CIMS) and the diethylene glycol based scanning mobility particle spectrometer (DEG SMPS). These data indicate that the formation of clusters that contain two or three sulfuric acid molecules ("dimer" and "trimer") is the primary bottleneck for nucleation. Basic gaseous compounds (ammonia and amine) stabilize these clusters, thereby enhancing nucleation rates. The sulfuric acid vapor uptake rate of tetramer (around 1 nm in diameter) is found to be close to the collision rate. For particles larger than 1 nm, contribution from chemical species other than sulfuric acid to their growth increases as particle sizes increase. A closed form expression for nucleation rates in terms of the sulfuric acid and basic gas concentration is proposed. Nucleation rates obtained from previous field measurements (Mexico City 2006 and Atlanta 2009) are in reasonable agreement with values predicted by the model.

The sensitivity of land surface parameters such as soil moisture and vegetation fraction to initiation of convection has been studied greatly in the past but with varying results. A reason for this is that many different models are used and each has their own way of simulating the atmosphere. Some of these models are not compared to observations to ensure their experiments are even valid. Before true experiments can begin, one needs to ensure that the model being used is accurate. Here I use WRF version 3.4.1 coupled with the Noah land surface model. A case of high convective activity is chosen, which is the May 10, 2010 severe weather outbreak over Kansas and Oklahoma. The North American Regional Reanalysis (NARR) data are used for initial and boundary conditions. I perform three WRF runs, a control run which uses the NARR data as is, a second run which reduces the soil moisture by 50% over the entire domain, and a final run which increases the soil moisture by 50%. The model is run at a 4 km resolution to capture mesoscale aspects and is started at 00Z May 10 and run 33 hours through 09Z May 11. The runs are compared to each other and also to observations from the Oklahoma Mesonet. I find that while all three runs simulate a highly supportive environment for severe weather, there are some notable differences. As expected, dewpoints in the reduced soil moisture run are lower and temperatures are higher. Convective Available Potential Energy (CAPE) was also lower in the reduced case. Despite this it seems more precipitation developed in the reduced case especially over Southern Oklahoma which is unseen in the control run. When all WRF runs are compared to observations, it appears that soil moisture is higher and temperatures are lower in the observations. The WRF run which used higher soil moisture did produce lower temperatures but still not as low as the observations. Upon further investigation it appears WRF cloud cover was lower than in the obser

Hosted by: Yangang Liu

Vertical wind shear plays an important role in modulating hurricane variability in the tropical Atlantic. The ability of global climate models to simulate the observed variation of North Atlantic vertical wind shear is investigated, using the suite of model integrations performed for the IPCC-AR4 assessment. Significant biases are found in the simulation of the mean shear during July to October, which are related to the biases on the simulation of SST. Moreover, in different time scales, a dominant dipole mode of vertical wind shear over the northern tropical Atlantic is found in both observations and numerical model simulations. Furthermore, uncoupled atmospheric model simulations are conducted to elucidate the mechanisms behind the dominant mode of shear variability. It turns out that the dipole mode of vertical wind shear over the northern tropical Atlantic could be an internal atmospheric mode. There are different prevailing flows at 200hPa over the western and eastern tropical Atlantic. Therefore, under the influence of mean flow, even with the same anomalous wind, there are opposite variations of vertical wind shear over the western and eastern tropical Atlantic. Finally, climate model simulations of the ENSO-shear relationship are compared with observations. It is shown that there is a strong influence of background mean flow on the ENSO-shear relationship, due to the inherently nonlinear nature of vertical wind shear. Even with realistic simulations of the ENSO- induced westerly anomaly in the upper troposphere, overestimated easterly background flow in the model simulations can alter the relationship between ENSO and vertical wind shear.

The core satellite of Global Precipitation Measurement (GPM), which is scheduled to launch in 2014, has a dual-wavelength precipitation radar (DPR). DPR consists of Ku and Ka radars. Ka-band radiowave suffers from strong attenuation for rain and strong Mie scattering effect for snow. Because ground measurements of precipitation (rain and snow) at Ka-band are limited, measurements of backscattering and extinction characteristics of precipitation are necessary for the GPM/DPR algorithm development. For the ground validation of the GPM/DPR, a dual Ka-band radar system was developed by the Japan Aerospace Exploration Agency (JAXA). The Ka radar system consists of two identical Ka radars. When the Ka radars face each other and observe the same precipitation system between the radars with opposite direction, both the equivalent radar reflectivity factor (Ze) and specific attenuation (k) can be measured at each range bin of the path. The measured k-Ze relations of rain, snow, and the melting layers can be used to develop the "scattering table" for the improvement of the GPM/DPR algorithm performance. Observations for both rain and snow using the dual Ka-radar system are ongoing in several locations in Japan. Results of measurements of k-Ze relations of rain and snow are presented. Performance of the system are evaluated by comparing measured Ze and k of rain with those estimated from the disdrometer. Although some biases in Ze exist, the measured k-Ze relations are reasonable. Among snow events, different tendencies of k-Ze plots appear depending on surface temperature. The difference of k-Ze relations of snow is attributed to the difference of the backscattering and attenuation characteristics between wet and dry snow. Moreover, as a transformation of the dual Ka observation, a vertical-slant direction observation for melting layer is proposed. The configuration is that one radar was directed in vertical and the other was in

Infrasonic acoustic energy is known to be generated during the collision of counter propagating ocean surface waves of like periods. The acoustic signals produced by such collisions are known as microbaroms. One significant source of microbarom radiation is the interaction of waves produced by large maritime storms with the background ocean swell. The region in which the microbaroms associated with a large storm are produced tends to be hundreds of kilometers from the eye of the storm. It was suggested by Young and Bedard that, when observed along propagation paths that pass through the storm, the microbarom signal can be severely refracted by the storm itself. Such refraction has been observed in data from the 2010 and 2011 Atlantic hurricane seasons. A data processing algorithm has been developed and implemented using the Capon minimum variance beamforming method. The results of this analysis will be presented and compared with predictions of the refraction using a geometric acoustics propagation model.

Hosted by: Alistair Rogers

There is a growing body of evidence suggesting vegetation mortality during drought or periods of high temperatures is rising globally. Research regarding the mechanisms of vegetation mortality during drought has grown dramatically in the last five years, as has research on the consequences of mortality on climate forcing. This new research has also stimulated valuable debate regarding how universal or variable mortality mechanisms may be globally, and how much feedback there is upon climate. Resolving these questions is essential to improve global climate models due to the inherent land-climate feedbacks. I will review the evidence for the variety of hypothesized mechanisms of death and the subsequent potential climate forcing. I will conclude by outlining a vision towards resolving these grand scientific questions with the ultimate goals of improving our understanding and modeling of climate-terrestrial impacts and feedbacks.

Analysis of observed temperature (from 1979-1997) at the surface, in the atmosphere, in the ocean, and from proxies shows increase of surface temperature but not in the other three time series. What does this signify?

Hosted by: Dr. Alistair Rogers

Among renewable energy sources, only biomass can provide fuel and electricity in a form and scale that is compatible with existing transportation and power generation infrastructure. Unlike wind and solar energy, biomass can be converted directly into liquid fuel by a variety of conversion routes, as is current practice with petroleum, or it can be stored to generate electricity on-demand, as is current practice with coal. Further, lignocellulosic biomass can be produced in such a way as to balance the three pillars of sustainability: economic, social and environmental sustainability. This presentation will discuss a portfolio of high-yielding biomass crops including Miscanthus spp., switchgrass (Panicum virgatum), prairie cordgrass (Spartina pectinata) and other grasses that, if managed appropriately, can be integrated into the US agricultural system with little impact on food production in many regions. Importantly, the technology for implementing biomass energy from these crops exists today.

Hosted by: Alistair Rogers

Abstract: We have developed Xeml Lab, a platform with a graphical interface, which helps the user to plan experiments and concomitantly generate machine-readable metadata files, based on different ontologies. We performed meta-analyses of a large set of experiments that were carried out during 5 years. This revealed that Arabidopsis achieves a remarkable metabolic homeostasis across a wide range of photoperiod treatments, and that adjustment of starch turnover and the leaf protein content contribute to this metabolic homeostasis.

Hosted by: Stephen Schwartz

There is a vigorous debate now about whether our oil, natural gas, and coal resources will be sufficient in the future. At the same time, there is an intense effort to predict the changes in climate that will result from consuming these fossil fuels. There has been surprisingly little effort to connect these two. Do we have a fossil-fuel supply problem? Do we have a climate-change problem? Do we have both? Which comes first? We will see that the trend for future fossil-fuel production is less than what is assumed in the United Nations climate-change assessments. The implication is that an understanding of producer limitations could help us do a better job of predicting climate change. We will also see that the time scale for exhausting fossil fuels is much smaller than that for global temperature change. This means that to reduce the future temperature rise, it is critical to reduce the total fossil-fuel production, not just slow it down. One possible approach for reducing total production would be to establish fossil-fuel preserves on federal lands that would be off limits for new leases for drilling and mining.

Hosted by: Lucian Wielopolski

Soils pay an important role in the global C cycle. They store twice as much organic C than is found in above ground biomass. For over a decade, terrestrial soils have been considered to be the likely location of the "missing CO2 sink" in the global C budget. Yet, the most of the researchers quantifying soil C storage and identifying the processes controlling soil C sequestration have found terrestrial soils that will be net sources (rather than net sinks) of atmospheric CO2 as temperatures rise. Estuaries store significant amounts of organic C, but these ecosystems have not been included into global C budgets. These landscapes occupy extensive areas along the New England coast and store similar amounts of soil C (to 1m) to other ecosystems in the region. The majority of the OC in these sediments is fixed by estuarine biota, not upland plants. As sea level rises, the newly fixed C is buried in the anoxic sediments, which prevents it from being remineralized and returning to the atmosphere. Preliminary calculations indicate that the C stored in these ecosystems represents a substantial portion of the C missing from North American C budgets.

Hosted by: Warren Wiscombe

The scenario is this: A category four tornado suddenly touches down outside Norman, Oklahoma, in a region of the country known as Tornado Alley. Almost simultaneously, a close-knit array of tiny state-of-the-art radars zeroes in on the lethal twister. The radar beams precisely triangulate on the location of the vortex and chase it with pinpoint accuracy down Berry Street. Personnel at the National Weather Service in Norman use a specially-designed console to trace the exact route as the tornado rumbles down this major shopping thoroughfare, chewing up buildings and hurling vehicles out of its path. Armed with precise positioning, the Weather Service issues an emergency alert that saves lives and reroutes ground and air traffic away from the progress of the storm. Meanwhile, another tornado touches down across town and appears to be heading for a hospital. Should the network continue tracking the first storm? Should it switch to pinpoint tracking of the second storm? Or should the system resources be configured for “best effort” tracking of both storms simultaneously? These questions reflect the mix of technology and policy challenges being undertaken within the NSF Center for Collaborative Adaptive Sensing of the Atmosphere (CASA). The CASA team is creating the new technology of user-driven radar networks that are capable of comprehensively mapping regions of the atmosphere that are beyond the reach of today’s radars, such as the crucial boundary layer where storms form and impact us. The driving vision of the center is that dramatic improvements in sensing, detecting, predicting, warning, and responding to hazardous weather events can be achieved by building a system that targeting its resources onto key regions where and when the end-user need is greatest. Achieving this vision requires the sustained collaboration of engineers, decision scientists, computer scientists, meteorologists, and sociologists, working in conjunction with the ultimate end-users

Measurements of the properties of marine stratus/stratocumulus clouds were made over the Eastern Pacific Ocean during the month of July 2005 using the Department of Energy G-1 aircraft. Flights were conducted over a coastal site located at Pt Reyes National Seashore just north of San Francisco, and extended west over the Pacific Ocean to as much as 200 km offshore, and as far south as Monterey Bay. Clouds sampled during these flights extended from near the ocean surface to altitudes between 300 and 450 m, (msl). Analysis will be presented showing the effects of aerosol loading on cloud microphysics from the perspective of both the first and the second indirect aerosol effects.

Hosted by: Warren Wiscombe

The world's critical energy problems require solutions beyond those policy makers are exploring now. Global warming is accelerating the rate at which radical transformations of energy systems away from fossil fuels are needed to avoid "dangerous human interference with the climate system." Given the world's large -- but climatically problematical, if CO2 is freely vented to the atmosphere -- coal resources, such a transition might be deferred to the 22nd Century. But global warming is the canary in the mine. Already arctic sea ice, tundra, alpine glaciers and the Greenland Ice cap are melting; sea level is rising; tropical disease vectors carrying West Nile virus and cholera penetrate temperate latitudes; and sea surface temperatures have warmed to the point where intense hurricanes like Katrina are not only more probable; but happen. Given the decades lost since the US last had an appropriate-scale alternate energy R & D program in the 70s I will argue that only a radical and disruptive Manhattan Project- or Apollo Program-style approach will work; and that engineers and scientists need to become pro-active on this issue.

Large uncertainties in aerosol properties and simple assumptions in aerosol models have made accurate prediction of aerosol radiative forcing and climate impact difficult. A common assumption in most models is that that black carbon (BC) aerosol consists of spherical particles. In reality, BC particles consist of smaller particles that aggregate into clusters having highly irregular and complex morphology. These properties have consequences regarding the atmospheric lifetime and optical properties of BC. Despite the complexity, the overall structure of BC aggregates can be described by fractals. Using fractal modeling, we can better understand the fate of BC and its optical properties.

Please contact Barbara Roland (roland@bnl.gov) for copy of the abstract.

Hosted by: Jian Wang

Atmospheric observations made during the past decade have shown that new particles are frequently formed by nucleation from the gas phase. The number of particles formed can be much greater than the number of preexisting particles, and freshly nucleated particles typically grow to sizes of 10-100 nm during the course of a day. Furthermore, nucleation often occurs over widespread areas in locations including urban areas, the continental boundary layer, the outflows of convective clouds, and coastal zones. Therefore, nucleation may be an important global source of cloud condensation nuclei, and may play an important role in regulating climate. In this lecture, observations of particle production and growth rates in various locations will be summarized. These observations were made possible by the recent availability of instruments to measure concentrations of certain gas phase precursors (e.g., H2SO4, NH3), and size distributions of particles as small as 3 nm and ions as small as 0.5 nm. Valuable insights have also been obtained from techniques that have recently been developed to measure the composition and properties of freshly nucleated particles. These new measurement techniques include the thermal desorption chemical ionization mass spectrometer to measure the composition of sub-10 nm particles and the Nano-Tandem Differential Mobility Analyzer to study their hygroscopicity and volatility. This lecture will summarize what these new analytical capabilities have taught us about atmospheric nucleation. A simple criterion that determines whether or not observable new particle formation occurs on a given day will also be described.

Hosted by: Alistair Rogers

Biosphere-Atmosphere Interactions in a Changing World – A Focus on Water Stan D. Wullschleger Environmental Sciences Division Oak Ridge National Laboratory Predicted changes in global and regional climate associated with increasing concentrations of atmospheric CO2 and other greenhouse gases have raised concerns about the potential impact of precipitation and temperature on the water budgets of terrestrial ecosystems. Few studies, however, have experimentally examined these impacts under relevant field conditions, thus complicating our ability to characterize important interactions between the biosphere and atmosphere. Several large-scale studies being conducted at Oak Ridge National Laboratory (e.g., free-air CO2 enrichment and long-term manipulation of precipitation) offer preliminary insights into some of these concerns. Data will be reviewed with a special emphasis on water use at the scale of leaves, trees, and forest ecosystems. It is suggested that as the spatial and temporal scale of our measurements and experiments has increased, so too has our perception of how leaf-level processes are involved in regulating water cycles at large spatial scales and over long periods of time.

Hosted by: Andy Vogelmann

Kilometer-scale clouds interact with the global circulation of the atmosphere in many important ways. Clouds are important for climate change and a wide variety of other geophysical processes. Despite decades of effort, our understanding of these, the role of clouds in global processes is poor and only slowly improving. New approaches are needed. This talk describes a prototype "multi-scale" approach that has generated promising results, but has many shortcomings. Ideas for further development are sketched.

Hosted by: Andrew Vogelmann