Abstract:

Aerosol measurements are conducted worldwide in order to identify the impact of aerosols on Earth’s radiation balance and its local and global climate. Aerosols are fine solid particles or liquid droplets suspended in the air, with diameters ranging from a few nanometers through a few tens of micrometers. They differ in size, shape, composition, and lifetime, depending on their origin and subsequent atmospheric processing. There are various approaches to aerosol measurements, e.g., ground-based or satellite observations. In this study, we combine satellite measurements obtained by the Multiangle Imaging SpectroRadiometer (MISR) and Moderate Resolution Imaging SpectroRadiometer (MODIS) instruments, respectively, and data from selected stations of the worldwide ground-based Aerosol Robotic Network (AERONET) in order to compare the Ångström exponent (AE) and aerosol optical depth (AOD) at a wavelength of 550 nm. We used AERONET measurements as our frame of reference. Four major aerosol types were investigated: urban-industrial, biomass burning, desert dust and maritime. The results show that MISR and MODIS data demonstrate systematic and significant differences in AE and AOD values with respect to AERONET observations. We attribute these differences between AERONET data and satellite MODIS and MISR data to spatial and temporal sampling procedures as well as model assumptions and retrieval algorithms of satellite data.

Abstract:

The West African Monsoon is a climatological moisture system in the Sahel region of Western Africa. The Sahel is an area of grassland located directly south of the Sahara Desert. The rainfall follows a cyclic pattern that shifts north and south seasonally and supplies the annual source of precipitation to these countries. The band typically reaches the Sahel during the summer months of June to September. When the monsoon season is shorter than normal droughts can occur, such as in 2005, when severe problems arose. Due to the sensitive nature of Sahel Rainfall, it is absolutely crucial that reliable climatological models be developed in order to predict rainfall trends in the near and distant future so that the inhabitants of the region can plan accordingly.

Abstract:

New York City recently implemented an innovative urban heat island mitigation program that involves painting black roofs white with elastomeric acrylic paint. The city is currently applying this technology to one million square feet of rooftops each summer, and similar efforts are beginning in other cities worldwide. We analyzed the first field data from this New York City cool roofs initiative.
Our results showed that the white roof’s surface temperatures were 7.8°C (14.0°F) cooler on average than those of the black roof, and that its high temperatures were 24.3°C (43.7°F) cooler on average. The data show a strong positive correlation between the white surface’s cooling effect and incident radiation, indicating that white roofs are most effective during the hottest part of the day and demonstrating the importance of albedo. The albedo tended to be highest in the early morning and evening and lower around midday, which is consistent with previous studies. When the white roof was recoated, its average albedo increased significantly from .35 to .63, demonstrating that white roofs must be repainted if they are to remain effective. Our emissivity results averaged .97 after the recoating, indicating that the white roof releases absorbed heat efficiently.

Abstract:

Global warming and the future of the Earth’s carbon cycle are at the forefront of many controversial debates today. Studying carbon accumulation in peatland core samples can help us reconstruct past climate. A four meter core spanning 11,000 years was collected from Bear Bog near Cordova, Alaska in July 2010. This location is of particular interest because it is potentially sensitive to future changes in climate. Another core was collected from Goldmine, near Fairbanks Alaska. The Bear Bog core was analyzed using Loss on Ignition (LOI), a technique used to measure the particular amount of combustible organic material in a given sample and is closely related to the carbon content of the peat, and macrofossils, visible plant remains (seeds, needles, etc) which serve as indicators of changes in vegetation, which are also directly related to climate changes. LOI samples were taken every 2 cm, and macrofossils were analyzed every 10 cm. Through the study of macrofossils and LOI, a record of both climate and carbon sequestration is under development at both sites. We hypothesize that carbon accumulation is strongly controlled by climate, such as abundance of available sunlight and precipitation. The study of this bog and other wetlands throughout Alaska will aid in understanding the Aleutian Low, a semi-permanent low pressure over the North Pacific ocean, which is responsible for the production of most of the precipitation in the Northern Hemisphere, and especially in the western areas. Consideration of carbon accumulation and changes in vegetation will allow for an adequate reconstruction of a climate focused timeline, as well as an understanding environments in Northern and Southern Alaska. Bear Bog and Gold Mine are two sites of three to be used in a study of a south to north transect of Alaskan peatlands.

Abstract:

New York City experiences a phenomenon called the Urban Heat Island Effect. This effect causes urban regions, with their closely spaced buildings and extensive paved surfaces, to become as much as 9-27˚F warmer than rural areas. As a result, urban communities experience increases in energy demand, air pollution, greenhouse gas emissions, heat-related and air quality illnesses, and a decrease in water quality. These issues are expected to become more severe with future climate change.
Green roofs help to mitigate the urban heat island effect. They also provide ecological benefits for animals and plants that have been displaced from their primary ecosystems. It is evident that green roofs have a positive impact on our “urban ecosystem,” but the long-term efficiency of green infrastructure under conditions of future climate in the New York City area has not yet been explored. For this project, we will model various climate change scenarios for New York City over the coming decades, and assess whether green roofs in New York City will need to be adapted, either structurally or ecologically, for temperature and precipitation conditions that may be rather different (and perhaps far more severe) than present.

Abstract:

Aerosols, particles of various size and composition suspended throughout our atmosphere, affect both the climate and our health. The amount emitted by both anthropogenic and natural sources changes with time, contributing to the variability of the aerosol. Changes in aerosol composition and size alter the aerosol single scattering albedo (SSA), a measure of how much light is reflected by the aerosol. We observed a decrease in SSA at three locations on the eastern seaboard, and believe sub-micron elemental carbon (EC) may be responsible for this change. In addition to their climatic impact, aerosols can also have adverse health effects. Studies inquiring into the relationship between air pollution and asthma have yielded conflicting results. Differences in size distribution and composition may have more of an effect on asthma than simply the concentration of the aerosol.

Abstract:

Due to the variable nature of the monsoon season, it is important to understand the climate of the Sahel region of Africa. Much effort has been put into creating accurate climate simulations of the region in both the short and long term. The climate model used in this project, the RM3 Regional Model at the Center for Climate Systems Research of Columbia University and the NASA Goddard Institute for Space Studies (GISS), has been configured to simulate weather and climate forecasts over West Africa by taking initial and lateral boundary conditions from either a global model or reanalysis data. The model simulations are used to investigate the impact of sea surface temperatures (SSTs) in the Atlantic Ocean on the movement of storms and intensity of the Inter-tropical Convergence Zone (ITCZ). Certain patterns of SSTs favor Sahel drought. In this project, the forcing data and the SSTs used in the RM3 come from Reanalysis 2, which are provided by the National Centers for Environmental Prediction’s (NCEP), National Atmospheric and Oceanic Administration (NOAA). One simulation uses 2006 SSTs, another uses climatological SSTs, and another tests the impact of cold SST anomalies.

Abstract:

We proposed three questions about green roofs: (A) What are the differences in retaining heat on black and white roofs? (B) What type of insect biodiversity exists on green roofs? (C) How much stormwater runoff can green roofs retain? First, black and white roofs were compared to see which retained less heat in the wintertime. Our conclusions were not as expected because it showed white roofs to be generally warmer than black roofs. Our analysis sent us back to question the manufacturer about the emissivity of the white material used. Second, we observed the insect biodiversity on green roofs. We monitored and collected ants, flies, and bees that begin to inhabit a green roof from initial planting to mature growth. Third, we calculated the percentage of stormwater that was permanently retained on the Con Edison green roofs. Our analysis showed that green roofs retained 30% of the stormwater.

Abstract:

Wetlands are a useful proxy for understanding the changes within an environment over time. Because of the anoxic conditions, marshes preserve leaves, seeds, pollen, and elemental composition in it‘s sediment, which can provide information about vegetational history, land use, climate and carbon storage over time. In order to obtain these preserved samples, cores must be taken in order to accurately study the sediments. The depth of a core is an ecological timeline from top to bottom. Depending on the variety of organic matter, plant species, and elemental composition, we can determine what happened around each sampling interval representing a specific time period. We do this with methods such as Loss on Ignition (LOI) and X-Ray Fluorescence (XRF).

Abstract:

We are investigating a new method for estimating annual river discharge for the past 6-7 millennia using D/H ratios of fossil leaf waxes in sediment cores in Hudson marshes. We are currently measuring Hydrogen isotopes of leaf waxes in vascular marsh plants (see Figure 1) to be calibrated to salinity and freshwater flux over the past year using data from the United States Geological Survey (USGS). Once the calibration is established, the δD of fossil leaf waxes in marsh cores along the Hudson River will be used to estimate variations in the salinity and thus Hudson River discharge for the past 6,000-7,000 years. This will help us better understand the paleoclimate and paleohydrology of the Hudson River Estuary.

Abstract:

The RM3 Regional Model, developed at the Center for Climate Systems Research of Columbia University and the NASA Goddard Institute for Space Studies (GISS), has been configured to simulate forecasts over West Africa by taking lateral boundary condition data from the National Center for Environmental Prediction’s (NCEP) Global Forecast System (GFS). These boundary conditions are provided in 1° resolution and are downscaled to the model's 0.5° resolution. The model is currently running at both NASA GISS and the headquarters of the African Center of Meteorological Application for Development (ACMAD) in Niamey, Niger. The outputs are then posted on the ACMAD website. To ensure that the people who utilize the resources provided by ACMAD are getting useful information from the RM3, the model must be constantly monitored and validated at NASA GISS. To accomplish this, comparative analyses have been done between RM3 and TRMM (Tropical Rainfall Measuring Mission satellite) for precipitation validation, as well as against NCEP Reanalysis II for wind circulation and surface temperature validation.

Abstract:

In this project we considered three areas of study investigating the mitigation of the Urban Heat Island Effect. The first task compared the interior cooling effects of a controlled dark roof with a green roof. Without being able to control variables, we were unable to establish clear cooling benefits in green roofs. The second task was to find materials that could replace the dangerously hot black mats in playgrounds.  Sand and gray mats were tested and shown to be cooler. The final task involved developing a methodology for using handheld equipment to determine emissivities on various urban surfaces. Through field-testing we produced a working procedure for accurately determining emissivities. These studies provided invaluable insight into the difficulties associated with this relatively new field of Urban Heat Island research. Future studies include doing a before and after comparison to allow for better control of the variables in green roof buildings, studying different types of playground mats, and testing emissivities for a variety of different materials in urban settings.

Abstract:

The aerosols in the atmosphere have an important yet poorly understood effect on human lives. NASA has studied greenhouse gases and their effect on the environment in depth, but NASA is only fairly recently beginning to study and understand aerosols. This coming January, NASA will launch the GLORY mission, a satellite which will collect data on the aerosols in the environment partly by use of a polarimeter. While this data will be extremely valuable, it is also important to collect data at ground level to compare to the data collected from orbit. Thus, this team has been working on developing accurate and effective polarimeters to use from Earth.

In our project last year, we were able to build a solar cell polarimeter that could measure polarization and allowed us to generate DOLP graphs. However, the data we collected was not very accurate and the equipment we were using was bulky and inefficient. This year’s project focuses on the use of newer technology to better measure aerosols, the digital camera. Using a high-tech SLR and polarizing filter, we were able to collect our data and then process it using both Adobe Photoshop and a computer program written in IDL which we are still perfecting.

Abstract:

The Hudson River has had a great history and serve as an important natural resources-from being the sanctuary for waterfowls, fish, and other wildlife, to purifying water. Thus, the understanding of past environmental change and possible future changes is required. Marshes are great archives of ecosystem and climate changes. In this study, we try to investigate the usage of elemental composition of marsh sediments to refer to the paleoclimate and environmental changes on the estuary. Using certain “elemental markers”, we can determine things such as human arrival, land use changes, pollution history, chronology, and climate changes. The study took place at various marshes along the Hudson Estuary, having different vegetation, salinity, and history.

Abstract:

N2O, or nitrous oxide, is a lesser-known but potent greenhouse gas, with over 300x the greenhouse warming potential of carbon dioxide. It is also one of six greenhouse gases recently classified by the U.S. Environmental Protection Agency (EPA) as a pollutant that can be regulated. While the Intergovernmental Panel on Climate Change (IPCC) has included N2O in its various scenarios for climate change over the next century, one potential anthropogenic source of N2O has not been included in their projections – namely, N2O emissions from wastewater treatment plants (WWTPs). For this project, we added new projections for N2O emissions from WWTPs to the IPCC climate change scenarios, to gauge the potential warming impact from this additional man-made source of N2O.

Tasks Accomplished:

This study is a stratigraphic examination of core sediment samples collected from Decodon Pond in Alley Pond Park at Queens, New York on January 30, 2008 and core sample sediments collected on July 21, 2008 in Jamaica Bay, Queens, NY. We examine macrofossils in Decodon Pond core and organic matter content in both cores. Decodon Pond macrofossils record indicates significant vegetation shifts, organic matter and charcoal increases, and change in lithology toward the present time. Jamaica Bay core exhibits changes in LOI and inorganic matter density as well.

The Pliocene Epoch (5.3 to 2.6 Ma) is the last “great global warming” before the beginning of the Pleistocene ice age. Paleoclimate proxy data, such as animal and plant fossils on land or in the ocean, suggest that the Earth was 2 to 3 degrees C warmer than present, with the most pronounced heating found in the polar regions. There may also have been a persistent El Niño-like feature, called El Padre, that led to increased warmth of tropical ocean surface waters. Despite these differences, the concentration of atmospheric CO2 during the Pliocene was similar to current day levels (380 ± 40 ppm). For this reason, climate researchers want to understand whether the Pliocene represents a warm world in an equilibrium state, a condition that we may eventually achieve in the near future even if CO2 emissions are stabilized. For our study, we used EdGCM/GISS GCM Model II to explore whether an El Padre could have contributed to the Pliocene global warming. We have also examined to what extent we can draw parallels between the regional climate impacts of an El Padre-driven Pliocene climate, and a strong modern El Niño, such as the 1997/1998 event, which has been projected to become a persistent feature of a future warm climate. We find that an El Padre/persistent El Niño could have played an important warming role for the Pliocene, and therefore has implications for our future climate.

This project studies the different ways to gather information about the variety of aerosols in the atmosphere. This project also focuses on trying to improve the current methods of collecting such information. Instruments such as the Microtops II Handheld Sun Photometer can be used to measure the aerosol optical thickness of the atmosphere; however, it does not tell us the refractive indices of the particles. Furthermore, these instruments cannot tell us the degree of polarization of sunlight at different scattering angles. In this study, we focused on using the polarization of light in the atmosphere to try to gain insight into what was causing that polarization of previously unpolarized natural light. To do this, we built a solar cell polarimeter which detects and measures the intensity of light at different angles, polarizations, and wavelengths. We collected data using this polarimeter and used it to further understand the aerosol particles in the air. Another aspect of this project was improving our solar cell polarimeter so that it works more efficiently and increases the validity of our data. To improve our polarimeter, we began to design a Wollaston Prism polarimeter which will collect data more accurately and efficiently. The Wollaston Prism polarimeter is still in the process of being built, but early analysis shows promise for the device.

The RM3 28-atmospheric layer Regional Model at the NASA Goddard Institute for Space Studies is configured to simulate the climate of West Africa. Using NCEP (National Center for Environmental Prediction) reanalysis data for boundary conditions, the RM3 interprets the information and produces a higher resolution distribution of data points with 0.5° (50km) spacing. However, in order to optimize the accuracy of the model, it must be assessed through validation against other sources such as TRMM (Tropical Rainfall Measuring Mission), FEWS (Famine Early Warning System), and CMORPH (Climate Prediction Center Morphing Technique). These observational estimates compute sets of data using algorithms to combine different satellite readings of atmospheric conditions. As a result, their ability to be used as controls for model validation must be tested. Comparisons between data sets have demonstrated notable differences in their outputs. Different comparative techniques are being considered, as well as the inclusion of ground observational data for more local areas to provide an “unaltered” meteorological reading. Once the most reliable data set is determined, its data will be used for comparative analysis with the RM3 as well as other regional climate models, including the UK Met Office model and the WRF (Weather Research and Forecasting) model.

This study analyzed the organic matter accumulation rates of wetlands in Alaska and wetlands in New York. A Loss-On-Ignition (LOI) analysis was done to obtain the amount of organic matter in the sediment samples. Using LOI data and sedimentation rates based on radiocarbon dates, organic matter accumulation values were plotted against time. After a comparing the results from Alaskan wetlands to each other, it is evident that annual precipitation and temperatures affect organic matter accumulation. After comparing the results from the wetlands from New York to each other, we see how salinity and vegetation types also affect organic matter accumulation. Results from Alaskan wetland sites shows that Swanson Fen has higher peat accumulation than Dark Bank. From New York wetlands, the salt marshes at Joco and Yellow Bar have accumulation 100 times higher than Tivoli Bays, the freshwater site. The New York sites have higher peat accumulation than the Alaska sites, potentially related to temperature, growing season length, and vegetation type.

Carbon dioxide (CO2) is one of the major greenhouse gases that contribute to global warming. The natural carbon cycle is a process that keeps the atmospheric level of CO2 as close to equilibrium as possible. However, after the start of the industrial era, the amount of atmospheric CO2 has been increasing at an alarming rate. Due to the excess amount of anthropogenic CO2 being released into the atmosphere, the natural sinks were unable to absorb the extra amount of CO2. Studies have shown that if the atmospheric level of CO2 were to continue to increase, there will be an adverse affects on the climate. The main focus of this study is to attribute the atmospheric CO2 to each country’s emission and to determine which measure of attribution is the best. To quantify the contributions of each country, three different computational methods are used.

The RM3 Regional Model at the NASA Goddard Institute for Space Studies is configured to simulate the climate of West Africa. Using the larger, lower-resolution Global Climate Model and the NCEP (National Center for Environmental Prediction) reanalysis data for boundary conditions, the RM3 interprets the information and produces a higher resolution distribution of data points with 0.5° (50km) spacing. However, in order to optimize the accuracy of the model, it must be assessed through validation against observations. From atmospheric observation programs instituted by AMMA (African Monsoon Multidisciplinary Analysis) and NAMMA (NASA African Monsoon Multidisciplinary Analysis) as well as from satellites such as the TRMM (Tropical Rainfall Measuring Mission), MODIS (Moderate-resolution Imaging Spectroradiometer), and QuikSCAT (Quick Scatterometer), data can be collected and organized so that the Regional Model can be validated with representations of actual climate events. In order for the observational data to be useful, the meteorological variables, times of observation and exact locations of atmospheric measurements must be acquired from the many different sources. In addition, the different graphical representations of the observational data must be considered as well as their tabulation. As the RM3 is validated and perfected, its accuracy and ability to simulate future atmospheric conditions can be improved. Once the RM3 is ready, it can serve many different functions, including weather prediction for organizations such as ACMAD (African Center of Meteorological Applications for Development). Another function of the RM3, the simulation of soil moisture and surface (or “skin”) temperature, would allow scientists to analyze the relationships between meteorological events such as storms and droughts and the environment’s ability to produce a substantial crop yield. Most importantly, improved climate and weather forecasts for African countries would help prepare citizens for epidemics of diseases such as meningitis and malaria that occur during the rainy season, as well as economic difficulties from deficient agricultural production associated with drought. Agricultural preparations would help to counteract the specter of long and all too frequent occurrences of drought that have led to famine throughout West Africa.

This project studies temperatures of typical urban surfaces to understand urban heat island mitigation. Contrasting environmental conditions include white versus black roofs, natural versus artificial turf, shaded versus non-shaded areas, and bare versus ivied walls. East Harlem is also studied. Infrared thermosensors measure surface and air temperatures there. Analysis shows that high albedos and evapo-transpiration can cause cooling. Urban heat island mitigation strategies that use these factors, such as vegetated & reflective surfaces, may be more effective. Preliminary evidence suggests that urban vegetation is significantly more effective than high-albedo surfaces.

NASA has tentative plans to launch the GLORY satellite in 2008 that will measure atmospheric aerosols and pollutants. The study of aerosols is very important because aerosols have both cooling and heating effects on earth’s climate. The cooling effect that aerosols have on the surface of the Earth is known as direct climate forcing. This is due to the direct reflection of radiation from the sun. Aerosols also have an effect on the radiative properties of Earth's cloud cover, known as indirect climate forcing. Although scientists are studying the properties of aerosols, not much is known about them. Through this investigation, data is being collected and analyzed to help locate regional aerosol trends, and use devices that measure Aerosol Optical Thickness to validate other instruments. The Polarimeter on the GLORY satellite has the ability to measure aerosols by looking at light reflectance, which can help identify concentrations of different types of aerosol in the air. Ultimately, sifting through data retrieved on particle concentration and Aerosol Optical thickness from land-based instruments will allow for the recognition of trends. This will define “baseline” aerosol characteristics in the New York region that can be used for validation purposes. Comparisons between urban and rural areas have also been made. Another aspect of this project is developing an initial protocol for the GLORY ground-truth validation. By comparing GLOBE sunphotometer data to AOT data from other instruments, the accuracy of the sunphotometers can be analyzed. After tests have been completed to make sure the instruments have been calibrated correctly, a protocol for accurate readings by high school and middle school students can be created. These instruments will be distributed to students around the world to take readings of Aerosol Optical Thickness as part of the satellite validation plan.

Facts to Know about the Late Ordovician Ice Age:

Based upon the date, data from the TRMM Satellite (Tropical Rainfall Measuring Mission) is needed for the simulated time period.

The TRMM helps in making sure that the output from the regional models is at least close to accurate.

The satellite gives an account of what actually happened for the time period specified, in the region specified.

All outputs from the TRMM and Regional Model(s) will be run through Transform

Gives a side-by-side comparison of the TRMM (actual) and the Regional Models

When all outputs are put through Transform and interpolated (image creation), a comparison can be made by differencing either the 28 layer with the TRMM or the 16 layer with the TRMM.

The SCIAMACHY satellite was used to track the amount of NO2 released

For the month of July New York City is seen to have high levels of NO2 as evidenced by our study.

This investigation will focus on investigating the distribution of aerosol in the New York City metropolitan region through the analysis of Multi-Filter Rotating Shadowband Radiometer (MFRSR) data. The MFRSR simultaneously measures the amount of sunlight transmitted through the atmosphere in six narrowband spectral channels. The spectral locations of the channels have been selected to provide information on aerosols (effective radius and optical depth, a measure of how much aerosol are present), and gases (ozone, nitrogen dioxide and water vapor column amounts). The spatial distribution of MFRSRs in the New York Metropolitan region will allow us to assess whether or not New York City is a source of regional aerosol. Since aerosols have been shown to alter the properties of clouds and hence precipitation rates and component of this investigation will seek to put our aerosol investigation into a climatological perspective by examining local changes in precipitation patterns.

(1) The NYSERDA Urban Heat Island Study: This project received funding from the NY State Energy Research and Development Authority (NYSERDA). The project began during the Summer 2004. It is a collaboration between NASA GISS and Hunter College researchers with Dr. Cynthia Rosenzweig (GISS) and Dr. William Solecki (Hunter) as the co-principle investigators.

The goal of the project is to elucidate the principle factors in NY city’s urban heat island (UHI) effect and to integrate these findings with an analysis of climate change and Con Edison ‘load pocket’ electricity consumption data. The project is also studying various mitigation scenarios for the UHI, especially urban tree planting and green roofing scenarios. The regional climate model MM5 is being run along with extensive GIS data analyses to quantify these scenarios. NASA Landsat-7 surface temperature and land cover data play a central role in the project.

(2) Columbia Green Roofs Workshop:This workshop is the first of its kind in the New York area and is being offered this Spring 2005 by Columbia University’s School of International and Public Affairs (SIPA). Dr. Stuart R. Gaffin of Columbia is the instructor.

The workshop is an intensive study of the potential role of extensive green roofing for mitigating a number of environmental problems for the NY metropolitan region including: the urban heat island and energy demand, air quality, stormwater overflows into the NY harbor, the need for urban green space and real estate amenity and other issues.The students consist of Master’s Thesis candidates in SIPA and the workshop is intended to be a research experience with new emerging data. Urban heat island and energy consumption mitigation is a major thematic topic in the class. Some of students are focusing on this and advancing GISS’s understanding of how green roofs can help reduce global warming and UHI impacts.

The students are working with the same NASA Landsat-7 image shown above and will be relating it to local issues. For example, Columbia University is planning a new Manhattanville campus in the West 130th Street area and ‘green’ building design, including green roofs is a focus. The Landsat data show clearly that Manhattanville is a hotspot with respect to UHI and this will be integrated into the planning. The workshop students will be partnering with Columbia planners and other classes studying the best urban design solutions for the new campus.

Results from the NYSERDA project described above are being made available to the students as the NYSERDA project proceeds.

Ongoing paleoenvironmental data from pollen and seeds in the protected marshes of the lower Hudson River Valley (Jamaica Bay, Staten Island, Piermont Marsh) indicates that major shifts in the watershed of the Hudson Valley have taken place.  These shifts involve climate change as well as estuarine changes due to European impact. We have just published evidence for the dramatic drought that New York experienced during the Medieval Warming Interval, approximately 800-1250 AD (Pederson et al., Quaternary Research, in press). We would like to expand our research to include a modern pollen sample database from the Hudson marshes and upland lakes that would serve as an ideal benchmark to evaluate our paleorecords. We also would like to sample the vegetation from the individual marshes to document their C-13 isotopic signature (C-4 vs. C-3 plants), as we are documenting the C-13 changes downcore.  These projects are comprised of both field laboratory components for a NASA NYC Research Initiative (NYCRI) team of high school, undergraduate and graduate students and faculty. Specific details of this research project are available upon request.

Climate variability in Africa's Sahel region has serious soci-economic implications. A better understanding of the climate dynamics for this region must consider synoptic weather and climate features, such as African wave disturbances (AWD), squall lines, the mid-tropospheric African Easterly Jet, the intertropical convergence precipitation maximum and the Tropical Easterly Jet, which are all under-resolved by the typical resolutions of global analyses and global climate models. Prior work at the Columbia University Center for Climate Systems Research has demonstrated the advantages of a high resolution, limited area, regional climate model (RM) for studying the characteristics of AWD and their relationship to the mean summer climate. Discrepancies in RM simulated mean climate fields and their implications for synoptic systems were previously noted. RM performance has been improved by incorporating the same land surface process model and the same moist convection parameterization used for years in the GISS GCM. The proposed research will produce a new set of climate analyses by downscaling NCEP re-analyses to a 0.5° grid over West Africa with the latest version of the RM. Some twenty seasons of the RM product will be systematically validated and evaluated and differences between rainy and drought composites will be documented. The proposed research will greatly benefit from the recent availability of 0.5° gridded analyses of observed monthly mean precipitation accumulations and surface air temperatures created by the Climate Research Unit of the University of East Anglia (New et al., 2000). Results from the improved RM can now be validated against the CRU observations at the same horizontal resolution. AWD characteristics, periodicities, amplitudes, frequency of occurrence and associated precipitation patterns will be analyzed for each simulated summer and differences between rainy and dry conditions noted. Relevant climate mechanisms, from planetary to regional scales will be identified to increase our understanding of how they influence the interannual variability of Sahel seasonal rainfall. An experiment has been designed to evaluate the improvements in the spatial definition of climate features achieved by the downscaling technique. The relative advantages of nudging and periodic reinitialization will be tested.