Meet Dr. Torbjörn Törnqvist, a professor at Tulane University’s Department of  Earth and Environmental Sciences, and learn about his work understanding prehistoric sea levels along the Gulf Coast.  Photo Credit: Paula Burch.

How does sea level rise today compare to sea level fluctuations in Earth’s past? What could current sea level trends mean for coastal communities and how should they prepare? These questions are the focus of Tulane University Professor Dr. Torbjörn Törnqvist’s work.

“Over the last century, the central U.S. Gulf Coast has experienced a rate of sea level rise almost five times the rate seen over the preceding thousand years,” said Törnqvist, who bases this estimate largely on analyses of sediment core samples from the Mississippi River Delta.

This use of deltaic plain sediment cores to establish multi-millennial records of sea level rise was pioneered in the Netherlands. This research was bolstered after the North Sea Flood of 1953, which killed about 2000 people. Törnqvist received both his undergraduate degree and Ph.D. from Utrecht University, where he was first exposed to sediment coring as a freshman. After graduation, Törnqvist turned his attention to the Gulf Coast.

“While doing my post-doctoral research comparing the morphology of the Rheine-Meuse and Mississippi River deltas, I realized that there was a real lack of data for past sea level rise in the Mississippi Delta area,” said Törnqvist. “Better data of prehistoric sea level rise is necessary to understand the evolution of the Mississippi Delta and why what is happening today is happening.”

Louisiana loses a football field sized area of coastal wetlands about every 40 minutes. This loss is due to a combination of factors, including damming of the Mississippi River upstream, which has resulted in a decrease of sediment load by 50 percent over the past 50-100 years. The current three millimeter per year rise in global sea level is also contributing to the wetland loss.

Tulane’s Department of Earth and Environmental Sciences keeps hundreds of 4-5 foot long core samples from the Mississippi Delta. These samples provide a record of more than 8,000 years of coastal evolution. Different layers from these cores are dated using radiocarbon isotope analysis, as well as through a newer technique known as optically stimulated luminescence dating (OSL). Analysis of grain sizes and fossils within the different layers helps determine whether the accumulations were from fresh or saltwater environments. Knowing where the salt and freshwater accumulations are in the cores is key to piecing together past sea levels.

Because of the low tidal range on the Gulf Coast, knowing past sea level behavior there is useful for constraining estimates of past global sea level rise. In addition, Törnqvist’s research on how sea level changed around 8,200 years ago, when a sudden influx of freshwater into the North Atlantic caused an abrupt cooling event, has been useful for paleoclimatology and climate modeling.

“Studying the 8,200 year-ago event is relevant for forecasting the changes in ocean circulation and the climatic response that could occur if melt rates on Greenland and elsewhere in the far North increase,” says Törnqvist.
Törnqvist is also the Director of the National Institute for Climatic Change Research (NICCR) Coastal Center, which is hosted by Tulane University’s School of Science and Engineering. NICCR is funded by the Department of Energy’s Office of Biological and Environmental Research.

Learn more about Dr. Törnqvist’s work.

Meet Dr. Michael Alexander, a meteorologist at NOAA’s Earth Systems Research Laboratory in Boulder, Colorado, who focuses on Pacific multidecadal variability.

The oceans influence the winds and the winds influence the oceans. This is the most basic principle of climatology’s sub-discipline of air-sea interactions, which is the focus of NOAA Meteorologist Dr. Michael Alexander’s research.

Alexander works at NOAA’s Earth Systems Research Laboratory in Boulder, Colorado. For the last 20 years, Alexander has conducted research on how weather and sea surface temperatures in the Pacific vary on decadal time scales. One key component of this decadal variability is the atmospheric bridge between the North and tropical Pacific Oceans.

“The atmosphere can connect two different parts of the ocean though a ‘bridge’ process,” Alexander said. “When warm or El Niño conditions are present in the tropical Pacific, the Aleutian Low in the North Pacific strengthens and moves southward. This strengthens the winds in the central Pacific, which cools the ocean via stronger ocean-to-atmosphere heat fluxes, near-surface ocean currents and by stirring up cold deep water to the surface. The atmospheric bridge affects sea surface temperatures throughout the Pacific Basin and over most of the global oceans.”

Left: A schematic diagram of the atmospheric bridge that exists between the Tropical and North Pacific Oceans. Image Courtesy of Giorgiogp2, Wikimedia Commons.

“From examining data and results from computer models, my colleagues and I noticed that sea surface temperatures over the North Pacific associated with the El Niño-Southern Oscillation (ENSO) and variability in the Aleutian Low looked very similar to the pattern of the Pacific Decadal Oscillation (PDO), said Alexander.

The PDO is a multi-decadal cycle of North Pacific sea surface temperature distributions. These temperature distributions are known to affect fisheries throughout the Pacific Basin, notably salmon fisheries. The PDO is associated with precipitation patterns over North America, particularly in the western United States. How much of this precipitation variability is driven by North Pacific sea surface temperatures, however, is unclear.

“Certainly the biggest oceanic driver of North American precipitation variability is ENSO. And of course, because ENSO is linked to the PDO via the atmospheric bridge and other mechanisms, ultimately it is ENSO that drives this variability directly and indirectly,” Alexander said.

By Alexander’s estimates, this atmospheric bridge mechanism accounts for about one third of the variability of the PDO. He recently published a monograph explaining the North Pacific variability mechanics in more detail.

Over the past year, Alexander has been an author on two papers – one published in Journal of Climate and the other in Nature Geoscience – linking changes over the North Pacific with changes in ENSO. Several recent studies have noted an increased frequency of central Pacific warming (CPW) events, also known as El Niño Modoki events. Modoki is a Japanese term for “similar, but different.” These CPW events differ from the more traditional eastern Pacific warming (EPW) events in how they affect the atmosphere, including feedback to the North Pacific Ocean.

Meet Dr. Paul Roundy, assistant professor at SUNY Albany’s Department of Atmospheric and Environmental Sciences, and learn about his research on tropical atmospheric waves.

Atmospheric waves are cyclic disturbances in variables including temperature, surface pressure and wind velocity. Traveling atmospheric waves propagate far and wide from the original point of disturbance. A thunderstorm in the tropics, for example, can create waves that reverberate all the way into the mid-latitudes, affecting America’s weather. Similarly, mid-latitude storms are associated with atmospheric waves that affect the tropics.

“Better understanding this two way connection between the tropics and mid-latitudes can help improve weather forecasts, possibly even leading to an extension of their accuracy beyond four to five days,” said Paul Roundy, assistant professor at SUNY Albany’s Department of Atmospheric and Environmental Sciences. “In a weather model, you cannot put a wall between the tropics and extra tropics and expect to have a reliable long range forecast.”

Current models simulate tropical waves, a key component of global weather, poorly. Roundy and his students focus on several types of tropical waves, with special emphasis on Kelvin Waves, which move eastward along the equator at 40 to 55 feet per second and Equatorial Rossby Waves, which propagate westward at a slower pace of 10 to 19 feet per second. These atmospheric waves have slower moving oceanic counterparts.

“A key challenge is improving our ability to model the coupling between convective disturbances in the tropics and the associated tropical waves. Improving our understanding of this coupling will help to improve our general circulation models and ultimately our mid-latitude forecasts,” said Roundy.

Roundy also focuses on tropical weather and climate signals, specifically the El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO). He conducts statistical analyses of the correlations between the behavior of these signals and weather in the mid-latitudes. The Madden-Julian Oscillation is a system that moves eastward through the tropical Indian and Pacific Oceans creating large regions of both enhanced and suppressed tropical rainfall as it travels.

“When you combine MJO and ENSO signals, particularly when these signals are strong, you get reasonably dependable long-range predictive capacity for the Northern Hemisphere winter,” Roundy said.

For more information on this predictive capacity, read Roundy’s recent Journal of Climate article. Also, visit his waves webpage for links to animations of long-range temperature predictions based on tropical signals.

Roundy also recently published on the influence of oceanic Kelvin waves on global atmospheric flow.

Some future areas of study for Roundy are the relationship between the development of tropical cyclones and tropical waves, as well as the interactions between tropical waves, ENSO and the MJO.

“Some MJO events amplify Kelvin waves in the ocean and spark El Niño events, while many other MJO events do not. I want to know more about what differentiates the MJOs that do impact ENSO and the MJOs that don’t.”

For more information on Roundy and his work, visit his homepage.

Meet Dr. Molly Baringer, acting deputy director of NOAA’s Atlantic Oceanographic and Meteorology Laboratory (AOML) in Miami, Florida.

Near Palm Beach, Florida, a “picket fence” type system of moorings and other monitoring equipment, which stretches all the way to Africa along 26.5 degrees North latitude, begins. This monitoring system, part of the RAPID-MOC project started in 2004, is currently the only initiative monitoring the Atlantic Meridional Overturning Circulation (MOC), arguably the most important component of the global circulation of heat and nutrients through the oceans.

The ocean currents and the atmosphere work together to create weather. Yet, the top meter of the oceans alone holds as much heat as the entire atmosphere, making this far from an equal relationship. The ocean is the proverbial “dog” and the atmosphere the “tail” of Earth’s climate system. Understanding the different components of ocean circulation and how this circulation varies over time is thus crucial to effective weather and global change prediction.

Dr. Molly Baringer, acting deputy director of NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami is one of the principal investigators of the RAPID-MOC project. Over the past few decades, her research has helped to change the prevailing view of the oceans from relatively static bodies to much more dynamic and fast-changing systems.

“The ocean interiors are much more dynamic and respond to perturbations much more rapidly than we thought, which we have learned as deep ocean monitoring has developed,” Baringer said.

For example, the strength of the Florida current, a major component of the Gulf Stream, has been monitored since 1982 by analyzing voltage changes in a telephone cable that runs across the bottom of the Atlantic at 27 degrees North latitude. This cable is a key part of the RAPID-MOC observation system.

According to Baringer, who now manages the monitoring project, “the flow of this current, which averages about 32 Sverdrups, can vary by over 30 percent over the course of a single day. We knew its strength varied before 1982, we just didn’t realize it varied by that much.” Thirty-two Sverdrups is about 9.5 billion gallons of water per second. That’s about 25,000 times the flow of the Mississippi River at Baton Rogue.

Understanding the strength and position of the Gulf Stream is important for predicting Eastern Seaboard sea-level variation and weather, such as the occurrence of wintertime Nor’easters. But the Gulf Stream is only a part of the larger Meridional Overturning Circulation (MOC).

“Most coupled climate models predict a 20-30 percent decrease in the strength of the MOC over the next century. Yet, over the past 28 years, there has been no observed weakening of the Florida Current, a key component of that circulation. Doing coast to coast, top to bottom monitoring of the Atlantic Ocean, which we are currently doing through the RAPID-MOC project, will help us resolve the current disconnect between what most models are predicting and what has been observed,” Baringer said.

Dr. Baringer also participates in the U.S. AMOC Science Team and is co-editor of NOAA’s annual State of the Climate Report as well as the lead author of the MOC chapter.

For more information on Dr. Baringer and her publications, visit her homepage. Maps and diagrams of the MOC monitoring effort can be found here.

Meet Dr. Matthew Lazzara, principal investigator of the University of Wisconsin – Madison’s Space Science and Engineering Center’s Antarctic Automatic Weather Station Project.

Earth’s most extreme weather happens on its least inhabited continent – Antarctica. The automatic weather stations there often endure temperatures under 100 degrees Fahrenheit below zero and winds of up to 137 miles per hour, conditions that can break the equipment and pose challenges to such monitoring efforts.

Dr. Matthew Lazzara, principal investigator of the University of Wisconsin – Madison’s Space Science and Engineering Center’s Antarctic Automatic Weather Station Project and Antarctic Meteorological Research Center, manages these automated weather stations in some of the world’s trickiest weather conditions. (Right: Dr. Lazzara next to one of the Wisconsin automatic weather stations.)

As Lazzara has learned, “Even the sturdiest automatic stations we have are no match for Antarctica’s fiercest winds. It’s really amazing the kinds of equipment damage I have seen.”

Such challenges don’t discourage Lazzara, however, as the data collected at the automated weather stations is crucial not only to better understanding Antarctica itself, but also for regional operational meteorology and even for improving global weather and climate models.

Lazzara also works at the opposite end of the Earth as principal investigator of the Arctic Composite Satellite Project. This new project uses the University of Wisconsin – Madison’s extensive archive of weather satellite data to form a more complete picture of how Arctic weather unfolds over time. Similar efforts for Antarctic composites have been going on for almost two decades.

“We don’t know a lot about the weather in the ten or so degree latitude band between the polar jet stream and the winds at the pole. Using composites of satellite images from both geostationary and polar orbiting satellites, we can learn more about this zone where other observational data is scarce,” Lazzara said. “Better forecasts for this zone will be useful for the increasing amount of air traffic going over or near the poles.”

There are also global implications. “When you don’t include polar winds in weather prediction models, noticeable differences in midlatitude weather are observed. Understanding polar weather improves our understanding of midlatitude climates.”

Learn more about Lazzara’s work by visiting his homepage.

Meet Dr. Robert Hart, an associate professor at Florida State University’s Department of Meteorology.

Dr. Robert Hart, associate professor at Florida State University’s Department of Meteorology, remembers always being curious about the weather. This curiosity was whetted during his middle school years when Hurricane Gloria passed through his hometown of North Branford, Conn. in September 1985.

“Only the first half of Gloria hit us,” he said. “We sat in the eye waiting for the second half to come, as was forecast, but it never did. I wanted to understand why.”

Years of trying to understand the “whys” of short-term and fine-scale meteorology prompted fundamental questions on the very nature of these storms.

“Tropical cyclones transport heat upwards and polewards, but the scientific community is only beginning to quantify this. Their existence means that other heat transport mechanisms, such as the Hadley cell circulation, don’t have as much work to do. What would Earth’s climate be like without hurricanes?”

Another fundamental question has to do with how the climate “remembers” tropical cyclones, or how they affect the weather even after the storms themselves dissipate. Hart, along with Ph.D. student Benjamin Schenkel, are investigating this impact.

“Hurricanes heat the atmosphere and cool the ocean surface in their wake. The negative sea surface temperature anomalies, for example, can persist for as long as 50-60 days after a category 3-5 storm, leading to persistent effects on both the weather and climate.” Hart said.

Climate “memory” may also extend to seasonal scales.

“Statistical relationships exist between the intensity of a tropical cyclone season and conditions in the subsequent winter seasons. We are just beginning to investigate the possible physical relationships that may underlie these statistical relationships.”

In addition to studying these fundamental issues, Hart continues to work on improving short-term hurricane forecasts. Through funding from NASA, he recently began taking a closer look at the last few decades of airplane reconnaissance data.

“This data is irregular and can be noisy, and is not particularly easy to use. Nonetheless, it is a unique data set with some important information on short-term intensity changes within storms.”

To learn more about Dr. Hart and his research, visit his homepage.

Meet Dr. Kenneth Kunkel, executive director of the Desert Research Institute’s Division of Atmospheric Sciences in Reno, Nevada.

Dr. Kenneth Kunkel, executive director of the Desert Research Institute’s Division of Atmospheric Sciences in Reno, Nevada, focuses on better understanding the causes of extreme weather events and relevant historic trends. He has been a lead author of two U.S. Global Change Research Program reports: Weather and Climate Extremes in a Changing Climate and Climate Models: An Assessment of Strengths and Limitations.

An interest in weather that developed while growing up on a farm in southern Illinois led Kunkel to pursue a Ph.D. in Meteorology from the University of Wisconsin. He served as New Mexico’s State Climatologist from 1982 to 1988 before moving on to the Midwestern Regional Climate Center (MRCC). Kunkel began his tenure at MRCC in 1988 – a year of severe drought in the Midwest that prompted the Center to focus on the links between weather extremes and agriculture.

“A La Niña event is believed to be one of the factors that caused an upper-air high pressure system to sit for weeks over the Midwest during the spring of 1988, causing a lack of rainfall and desiccation of soils. This rendered summertime precipitation, which is in large part recycled spring rainfall, to be almost non-existent,” Kunkel said. This focus on extremes was reinforced by the 1993 Midwest floods.

Today, at the Desert Research Institute, Kunkel focuses his studies on the meteorology behind precipitation extremes.

“Recent trends in more extreme events may be largely a product of increases in water vapor, or more ‘juice’ in the atmosphere, yet changes in other processes are likely affecting storm formation as well.”

Understanding these other processes is important to predict future precipitation regimes.

“Modeling mean precipitation itself is challenging and few extreme events appear in model simulations because such events are rare in nature. In the future, higher resolution models and faster computers will give us more realistic portrayal of such extreme events, allowing us to better understand what governs their formation,” he said.

Kunkel is also applying data from global climate models to drive higher-resolution regional climate models. “Use of this higher-resolution downscaled approach can markedly improve model accuracy of precipitation for the United States as a whole,” he says.

Download related Earth Gauge video: Heavy Rain Trends in the Eastern United States.

Meet Dr. Benjamin Kirtman, a professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences

Dr. Benjamin Kirtman grew up in southern California, where he spent many wet El Niño winters pumping water out of his family’s flooded basement. This firsthand experience with the effects of the El Niño-Southern Oscillation (ENSO) – arguably the most potent driver of year-to-year climate variability – and an aptitude for mathematics led him to a career in improving weather and climate prediction.

Today, as a professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences, Dr. Kirtman focuses on refining our ability to understand and predict the behavior of ENSO, a five- to seven-year cycle in the equatorial Pacific that also displays decadal variability. In the United States, different phases of ENSO correspond to pronounced regional differences in winter precipitation.

“While bodies like the IPCC focus on time scales of 100 to150 years, improving our predictive capacity on decadal [10 to 20-year] time scales will be more helpful for people planning on those time scales, such as power and water resource managers,” he said. There are several challenges to improving that predictive capacity.

“Right now, models have difficulty accurately representing how tropical convective systems organize,” Kirtman said. “These systems influence sea surface temperature distributions and thus ENSO’s properties. Another opportunity lies in better knowledge of the biology of the eastern tropical Pacific. These waters are nutrient rich and cloud cover here is rare. This biology affects how sunlight penetrates the ocean waters and the vertical structure of the upper ocean.”

While better ENSO forecasts stand to benefit the United States, a strong motivator for Dr. Kirtman is helping the developing world.

“Developing countries in the tropics have less adaptive capacity than richer nations and because weather in the tropics is more extreme and variable than at the mid-latitudes, improving our predictive capacity on year-to-year and decadal time scales can go a long way in terms of saving lives and money in those areas.”

Related Resources:
More information about current ENSO conditions from NOAA’s Climate Prediction Center.
A recent Nature publication on El Niño in a changing climate.

Meet Dr. Adam Schlosser, a Principal Research Scientist in the Center for Global Change Science, and the Assistant Director of Research for the Joint Program on the Science and Policy of Global Change at the Massachusetts Institute of Technology.

Water, energy and biogeochemical cycles of the land form a critical component of Earth’s climate system. Understanding how flows and stores of carbon, water, heat, nitrogen and other nutrients interact as well as how these cycles relate to land cover changes is crucial for predicting future climate states. Dr. Adam Schlosser, a Principal Research Scientist at the Massachusetts Institute for Technology’s Center for Global Change Science, has been studying these issues and their applications to meteorology and climate since the early 1990s when he was a graduate student at the University of Maryland’s Department of Meteorology.

This graduate work, as well as the work he did during his post-doctoral years at NOAA’s Geophysical Fluids Dynamics Lab, focused on getting models to reproduce long-term variability in hydro-climate.

“Two key issues are ‘can we predict future climate states based on how wet or dry land is at a given point in the year?’ and ‘do measurements of snow-cover and depth help us predict climate?’” said Schlosser.

To help answer these questions, Schlosser also participates in NASA’s Energy and Water Cycle Study (NEWS) Science Integration Team. “We must balance as well as reduce global precipitation and evaporation observations below one percent relative uncertainty in order for anticipated human-induced changes to be faithfully detected and predictions improved.”

At MIT, Schlosser focuses on developing the land component of the Institute’s Integrated Global Systems Model (IGSM), an Earth Systems Model of Intermediate Complexity (EMIC).

“The IGSM incorporates the human economy and time-dependent emissions of key greenhouse gases and other pollutants, and in order to account for the inherent uncertainties involved in these types of models, we must run hundreds or thousands of simulations to achieve reliable averages.”

Visit Schlosser’s Web site for more information.

Meet Dr. Irina Sokolik, a Professor at the Georgia Institute of Technology’s School of Earth and Atmospheric Sciences.

Mineral dust suspended in the atmosphere plays an active role in Earth’s climate, affecting things like energy balance, convection, photosynthesis, clouds, precipitation, tropical cyclone development and air quality. How to model and predict such effects is less clear.

Dr. Irina Sokolik, a professor at Georgia Tech’s School of Earth and Atmospheric Sciences, formally began studying dust in the late-1980′s as part of a joint project between the U.S. and Russian Academies of Sciences, where she observed dust in arid regions of Central Asia and California’s Owens Lake.

“Ground observations are necessary to accurately model dust. Each basin’s dust is unique, consisting of unique proportions of different minerals, which means the way it absorbs and reflects different types of radiation is also unique,” she said.

Yet, mineral properties are only part of modeling dust. “Each dust particle is a different shape and size, and this must also be accounted for. Even if you put the same total mass into the models, very different effects can result from changes in particle size and shape distributions.”

The latest generation of satellite sensors provides the unique capability to make observations of dust on the global scale.  As part of NASA’s CALIPSO science team, Sokolik uses data from the “A-Train” satellite constellation to better understand the interactions between dust and clouds.

“Most models just show how dust is transported. Feedbacks between heating rates in the dust layer, convective mixing and cloud formation have yet to be fully incorporated in such models,” said Sokolik. How land cover changes play into these relationships is also an important question.

“While moderate dust events do not have the global effects the dust storms do, they noticeably impact regional climate, air quality and public health, particularly children’s health.” Sokolik is one of the leaders of the Northern Eurasia Earth Partnership Initiative (NEESPI), an interdisciplinary program which studies these problems in the broad context of environmental and climatic changes occurring in the region.

Read Dr. Sokolik’s articles in the Bulletin of the American Meteorological Society and Journal of Geophysical Research- Atmospheres. This research is funded by the NASA Land-Cover and Land-Use Change Program.

Meet Dr. Warren Wiscombe, Senior Scientist at NASA Goddard Space Flight Center.

While working in the private sector research industry after obtaining his Ph.D. in Applied Math from the California Institute of Technology, Dr. Warren Wiscombe essentially “fell into” the fledgling subject of climate modeling. In the late 1960′s he volunteered to work on a subcontract through the Department of Defense’s Advanced Research Project Agency’s (ARPA) Climate Dynamics Program, the first large-scale climate research program centered around modeling. Today, he continues to improve models by working as a senior scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., and acting as chief scientist for the Department of Energy’s (DOE) largest global change research program, called the Atmospheric Radiation Measurement (ARM) Program.

“As chief scientist I focus on finding good projects. When people have a good idea, I push it,” said Wiscombe, who has been leading the ARM program since 2005.

ARM focuses on better understanding clouds and radiative feedbacks – currently the largest sources of uncertainty in the climate models. The program has 75 principal investigators and over 300 scientists, six participating DOE National Laboratories, and numerous research stations across the globe including in the Equatorial Pacific, Alaska’s North Slope and the southern Great Plains.

“One of the more challenging aspects of the job is to prioritize amongst so many good ideas in order to maintain our focus on efficiently improving the models,” Wiscombe said.

One project Dr. Wiscombe has highlighted as particularly important is an imminent field campaign in the Chilean Andes to monitor the radiative effects of water vapor in the upper atmosphere. He also spearheaded the recent transition at ARM from using vertically oriented radars, which can only monitor clouds as they pass directly overhead, to scanning radars, which can monitor any clouds within 20 miles.

When asked about the future, Wiscombe is particularly excited about the potential use of Uninhabited Aerospace Systems (UAS, more commonly known for their use in war and reconnaissance). “They can fly missions too dull, dirty and dangerous for human beings, but which can provide crucial information.” He is also passionate about the resurrection of the Deep Space Climate Observatory (DSCOVR), which will sit about one million miles from the Earth and enable researchers to watch the step-by-step progression of terrestrial events, whereas today’s low-orbital satellites only provide twice-daily snapshots.

“Imagine being able to observe the development of a thunderstorm, or a dust storm, from start to finish. Imagine being able to watch air quality changes in a single location over the course of an entire day. The DSCOVR location makes such observations possible.”

View a list of Wiscombe’s publications.

Meet Dr. Paquita Zuidema, Associate Professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science – Division of Meteorology and Physical Oceanography.

Clouds both warm the Earth by trapping heat and cool it by reflecting sunlight. Understanding how clouds work is crucial for modeling the global climate system and predicting how it will change in the future. One of the scientists committed to improving understanding of cloud dynamics is at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

“It was fortunate that I chose to get a graduate degree in physics at a school [University of Washington] with a strong atmospheric science program. I decided then that the most socially relevant way to use my education would be working to improve our understanding of Earth’s climate,” said Zuidema. “Currently, cloud processes are poorly resolved in climate models and create the largest source of uncertainty in climate change predictions. The 50-kilometer resolution of most of these models may be too coarse to accurately depict cloud dynamics. Our best guesses on how aerosols [a key variable for cloud properties] affect the climate through clouds, for example, come from observations.”

Despite this uncertainty, Zuidema notes the significant progress made over the course of her career. “There used to be discrepancies in the models regarding low level clouds, which tend to cool the Earth as they reflect more energy than they trap. Now, most models predict that there will be less low level clouds in the future. As far as understanding what will happen to clouds that form higher up in the atmosphere, however, we still have a way to go.”

Zuidema’s research has included studying monsoon dynamics by gathering data in the Bay Bengal and the Gulf of California and traveling to the Arctic to better understand cloud ice-initiation processes. Recently, she has been improving understanding of stratus decks, which form where cold ocean currents run next to continents to the east, such as off the coast of California and, for her study, off the the northern Chilean coast. She also worked with Dr. Ping Zhu at Florida International University’s Department of Earth Sciences on a recent publication in Geophyscial Research Letters that identified some potential biases in current cloud modeling schemes.

View a listing of Dr. Zuidema’s recent publications.

Over the past decade, the interactions between land surface changes and climate changes, particularly on a regional level, have gained recognition as being important to understanding the climate system.  Dr. Benjamin Cook, currently an Adjunct Associate Research Scientist with NASA’s Goddard Institute for Space Studies and a former NOAA Climate and Global Change Postdoctoral Research Fellow, focuses on how land cover change can affect climate directly by altering the exchange of energy and water between the surface and the atmosphere, and indirectly by promoting phenomena such as wind erosion.

“Land cover changes, such as reduction in plant cover resulting from a drought, can result in more wind erosion, which puts more dust in the atmosphere, resulting in reductions in surface radiation, convective heating, soil evaporation, and the ability for convective storms to form and produce rainfall.  This reduction in rainfall results in more drying and more dust, and the cycle continues,” says Cook.  This phenomenon, an example of a postive feedback loop, is illustrated in one of Cook’s recent publications detailing how the ModelE climate model at NASA’s Goddard Institute for Space Studies (GISS) simlated the 1930′s “Dust Bowl.”  This work was co-authored by Ron Miller, a GISS expert on modeling the radiative effects of atmospheric dust, and Richard Seager, an expert on sea surface temperature (SST) forcings at Columbia University’s Lamont-Doherty Earth Observatory, and explains how SST anomalies alone do not explain the severity or position of the “Dust Bowl” drought.  Only through a combination of SST data and estimated atmospheric dust concentrations can the climate of the 1930′s Midwest be accurately modeled.

“Three of the key variables controlling the frequency and severity of drought are: sea surface temperature variations, including varitions in the Pacific due to the El Nino Southern Oscillation; well mixed greenhouse gases and their climate impact; and the land surface [conditions],” says Cook.  “We have seen these interactions in regions as diverse as North America during the Dust Bowl, the decades-long Sahel drought in West Africa, and even in Europe during the extreme drought of 2003.”

View a listing of Dr. Cook’s recent publications.