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Scott, RC, Nicolas JP, Bromwich DH, Norris JR, Lubin D.  2019.  Meteorological drivers and large-scale climate forcing of West Antarctic Surface Melt. Journal of Climate. 32:665-684.   10.1175/jcli-d-18-0233.1   AbstractWebsite

Understanding the drivers of surface melting in West Antarctica is crucial for understanding future ice loss and global sea level rise. This study identifies atmospheric drivers of surface melt on West Antarctic ice shelves and ice sheet margins and relationships with tropical Pacific and high-latitude climate forcing using multidecadal reanalysis and satellite datasets. Physical drivers of ice melt are diagnosed by comparing satellite-observed melt patterns to anomalies of reanalysis near-surface air temperature, winds, and satellite-derived cloud cover, radiative fluxes, and sea ice concentration based on an Antarctic summer synoptic climatology spanning 1979-2017. Summer warming in West Antarctica is favored by Amundsen Sea (AS) blocking activity and a negative phase of the southern annular mode (SAM), which both correlate with El Nino conditions in the tropical Pacific Ocean. Extensive melt events on the Ross-Amundsen sector of the West Antarctic Ice Sheet (WAIS) are linked to persistent, intense AS blocking anticyclones, which force intrusions of marine air over the ice sheet. Surface melting is primarily driven by enhanced downwelling longwave radiation from clouds and a warm, moist atmosphere and by turbulent mixing of sensible heat to the surface by fohn winds. Since the late 1990s, concurrent with ocean-driven WAIS mass loss, summer surface melt occurrence has increased from the Amundsen Sea Embayment to the eastern Ross Ice Shelf. We link this change to increasing anticyclonic advection of marine air into West Antarctica, amplified by increasing air-sea fluxes associated with declining sea ice concentration in the coastal Ross-Amundsen Seas.

Lubin, D, Ricchiazzi P, Gautier C, Whritner R.  1994.  A method for mapping Antarctic surface ultraviolet radiation using multispectral satellite imagery. Antarctic Research Series. 62:53-81.   10.1029/AR062p0053   Abstract

Satellite-tracking facilities recently deployed at U.S. Antarctic research stations provide an extensive data set for studying the atmospheric radiation budget. Images from the advanced very high resolution radiometers (AVHRR) aboard the National Oceanic and Atmospheric Administration polar orbiters can be used in conjunction with data from the Nimbus 7 total ozone mapping spectrometer (TOMS) to construct maps of biologically active ultraviolet irradiance at the Antarctic Earth surface. We have developed a method to perform this mapping which involves refinements to the satellite data as well as detailed radiative transfer theory. We recalibrate the AVHRR data to account for sensor deterioration in orbit, and we remove bidirectional reflectance effects where possible. A surface albedo map can be constructed for the region and time period of interest by compositing as many cloud-free AVHRR images as are available. The optical depth of clouds over the open ocean can be estimated from AVHRR visible channel imagery by direct application of a delta-Eddington radiative transfer model. Over snow and ice, radiative transfer limitations require the use of an empirical parameterization for cloud optical depth as a function of the brightness temperature difference between AVHRR thermal channels 3 and 4. This parameterization is derived for cloud fields over the ocean and applied to nearby cloud fields over snow and ice. Once each pixel in a satellite image has an associated estimate of total ozone, cloud optical depth, and surface albedo, a delta-Eddington radiative transfer model is used to calculate the surface irradiance at any ultraviolet, visible, or near-infrared wavelength. Estimates of cloud optical depth and surface irradiance can be validated by ground-based radiometers, including the NSF UV monitor.

Lubin, D, Chen JP, Pilewskie P, Ramanathan V, Valero FPJ.  1996.  Microphysical examination of excess cloud absorption in the tropical atmosphere. Journal of Geophysical Research-Atmospheres. 101:16961-16972.   10.1029/96jd01154   AbstractWebsite

To investigate the excess shortwave absorption by clouds, a numerical cloud generation model has been coupled to a plane-parallel discrete ordinates radiative transfer model. The former was used in a time-dependent fashion to generate a cumulonimbus turret and three types of cirrus anvil (precipitating, extended, detached) representing three stages of cloud evolution outward from the turret. The cloud particle size distributions, as a function of altitude, were used as input to the radiative transfer model using indices of refraction for pure water and pure ice and equivalent sphere Mie theory. The radiative transfer model was used to calculate the ratio of cloud forcing at the surface to cloud forcing at the top of the atmosphere, both for the broadband shortwave and as a function of wavelength. Recent empirical studies have placed this cloud forcing ratio at around 1.5, and our coupled model results approach this value for small solar zenith angles, when the cloud contains large (>100 mu m) ice particles that absorb significantly in the near infrared (primarily the 1.6-mu m window). However, the empirical studies are based on diurnal averages, and our plane-parallel radiative transfer model yields an area and diurnally averaged cloud forcing ratio of only 1.18 for a tropical cumulonimbus and cirrus anvil system, primarily because of the rapid decrease of the ratio with solar zenith angle. The ratio decreases because of the increase in albedo with solar zenith angle, which is a characteristic feature of plane-parallel clouds. Adding dust or aerosol to the cloud layers, to make them absorb at visible wavelengths, makes the instantaneous cloud forcing ratio larger for an overhead Sun but also makes the solar zenith angle dependence in the cloud forcing ratio more pronounced. These two effects cancel, eliminating interstitial aerosol as a possible explanation for the excess cloud absorption in plane-parallel radiative transfer modeling. The strong dependence of the surface/top of the atmosphere cloud forcing ratio on solar zenith angle may be a fundamental defect with the plane-parallel approach to solar radiative transfer in a cloudy atmosphere.

Podgorny, I, Lubin D, Perovich DK.  2018.  Monte Carlo study of UAV-measurable albedo over Arctic Sea ice. Journal of Atmospheric and Oceanic Technology. 35:57-66.   10.1175/jtech-d-17-0066.1   AbstractWebsite

In anticipation that unmanned aerial vehicles (UAVs) will have a useful role in atmospheric energy budget studies over sea ice, a Monte Carlo model is used to investigate three-dimensional radiative transfer over a highly inhomogeneous surface albedo involving open water, sea ice, and melt ponds. The model simulates the spatial variability in 550-nm downwelling irradiance and albedo that a UAV would measure above this surface and underneath an optically thick, horizontally homogeneous cloud. At flight altitudes higher than 100 m above the surface, an airborne radiometer will sample irradiances that are greatly smoothed horizontally as a result of photon multiple reflection. If one is interested in sampling the local energy budget contrasts between specific surface types, then the UAV must fly at a low altitude, typically within 20 m of the surface. Spatial upwelling irradiance variability in larger open water features, on the order of 1000 m wide, will remain apparent as high as 500 m above the surface. To fully investigate the impact of surface feature variability on the energy budget of the lower troposphere ice-ocean system, a UAV needs to fly at a variety of altitudes to determine how individual features contribute to the area-average albedo.

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Kirkman, D, Tytler D, O'Meara JM, Burles S, Lubin D, Suzuki N, Carswell RF, Turner MS, Wampler EJ.  2001.  New Hubble Space Telescope spectra of QSO PG 1718+4807: No evidence for strong deuterium absorption. Astrophysical Journal. 559:23-28.   10.1086/322357   AbstractWebsite

The Z(abs) similar to 0.701 absorption system toward QSO PG 1718 + 4807 is the only example of a QSO absorption system which might have a deuterium/hydrogen ratio approximately 10 times the value found toward other QSOs. We have obtained new Space Telescope Imaging Spectrograph spectra from the Hubble Space Telescope of the Ly alpha and Lyman limit regions of the system. These spectra give the redshift and velocity dispersion of the neutral hydrogen, which produces most of the observed absorption. The Ly alpha line is too narrow to account for all of the observed absorption. It was previously known that extra absorption is needed on the blue side of the main H I near the expected position of deuterium. We do not find evidence in the current data that the extra absorption is entirely deuterium and find that it is more likely that some of the extra absorption is contaminating H. Until new data can be found that can independently constrain the line parameters of the potential contaminating H, it will not be possible to measure D/H in this system. Some uncertainty persists because we have a low signal-to-noise ratio and the extra absorption-be it deuterium or hydrogen-is heavily blended with the Ly alpha absorption from the main hydrogen absorption.

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Lubin, D, Vogelmann AM.  2010.  Observational quantification of a total aerosol indirect effect in the Arctic. Tellus Series B-Chemical and Physical Meteorology. 62:181-189.   10.1111/j.1600-0889.2010.00460.x   AbstractWebsite

We use 6 yr of multisensor radiometric data (1998-2003) from the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program to provide an observational quantification of the short-wave aerosol first indirect effect in the Arctic. Combined with the previously determined long-wave indirect effect, the total (short-wave and long-wave) first indirect effect in the high Arctic is found to yield a transition from surface warming of +3 W m(-2) during March to a cooling of -11 W m(-2) during May, therefore altering the seasonal cycle of energy input to the Arctic Earth atmosphere system. These data also reveal evidence of a first indirect effect that affects optically thinner clouds during summer. which may represent an additional negative climate feedback that responds to a warming Arctic Ocean with retreating sea ice.

Lubin, D, Frederick JE.  1990.  Observations of ozone and cloud properties from NSF ultraviolet-monitor measurements at Palmer Station, Antarctica. Antarctic Journal of the United States, Washington, DC. 25:241-242. AbstractWebsite

The National Science Foundation scanning spectroradiometer at Palmer Station provides hourly ground-based measurements of solar ultraviolet irradiance. In addition to defining the ultraviolet radiation environment of the region, these measurements allow the derivation of the column density of atmospheric ozone above the station nearly every daylight hour. This hourly time resolution, not generally available from other methods of monitoring Antarctic ozone abundances, enables the detection of large and rapid changes in total column ozone and ultraviolet surface irradiance associated with the dynamics of the polar vortex. In conjunction with a daily record of sky conditions and radiative transfer modeling, the ultraviolet-monitor measurements permit a quantitative understanding of the role of cloud cover in regulating ultraviolet radiation levels at the Antarctic Earth surface.

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Lubin, D, Massom R, SpringerLink.  2006.  Polar Remote Sensing Volume I: Atmosphere and Oceans. , Berlin, Heidelberg: Praxis Pub., Chichester, UK Abstract
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Massom, R, Lubin D, SpringerLink.  2006.  Polar Remote Sensing Volume II: Ice Sheets. , Berlin, Heidelberg: Praxis Pub., Chichester, UK Abstract
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Frederick, JE, Lubin D.  1988.  Possible Long-Term Changes in Biologically-Active Ultraviolet-Radiation Reaching the Ground. Photochemistry and Photobiology. 47:571-578.   10.1111/j.1751-1097.1988.tb08846.x   AbstractWebsite

Three scenarios for long-term changes in atmospheric ozone over the time period 1960 to 2030 lead to different projections for the ultraviolet radiation flux at the earth's surface. Biologically effective fluxes for damage to DNA and generalized damage to plants vary by a factor of 10 or more with latitude and season irrespective of possible changes in ozone. The natural latitudinal gradient in radiation corresponds to spatial changes in biologically effective fluxes which are large compared to temporal changes expected from trends in ozone over the time period analyzed. In an extreme scenario of ozone change, based on an assumed increase in chlorofluorocarbon release rates of 3% per year after 1980, the annually integrated effective flux for damage to DNA increases by 13.5% at latitude 40°N between 1960 and 2030. With chlorofluorocarbon release rates held fixed at their 1980 values, the corresponding radiation increase is only 2.3%. In a scenario where atmospheric chlorine remains fixed at its 1960 value, trends in atmospheric methane and nitrous oxide imply a decrease in biologically effective flux at 40°N of 5.3% between 1960 and 2030.

Lomax, AS, Lubin D, Whritner RH.  1995.  The Potential for Interpreting Total and Multiyear Ice Concentrations in Ssm/I 85.5 Ghz Imagery. Remote Sensing of Environment. 54:13-26.   10.1016/0034-4257(95)00082-c   AbstractWebsite

The 85.5 GHz vertically and horizontally polarized channels of the Special Sensor Microwave Inagers (SSM/1) aboard the Defense Meteorological Satellite Program (DMSP) spacecraft offer the potential to map sea ice with a spatial resolution of 12.5 km, a factor of two improvement over the popular National Aeronautics and Space Administration (NASA) Team algorithm, but with the limitation of increased atmospheric influence on the sea ice signal. Application of an algorithm for estimating total ice concentration from 85.5 GHz data, which exploits the large polarization for open water versus the small polarization for most ice types, reveals agreement with the NASA Team algorithm typically within. a standard deviation of +/- 3% for nearly cloud-free winter conditions. The uncertainty increases to a standard deviation of +/- 6% for cloudy winter conditions. In winter, volume scattering from multiyear ice has a noticeable impact on the 85.5 GHz brightness temperatures. By employing a polarization corrected temperature variable previously defined to isolate precipitation in mid-latitude DMSP imagery, it is possible to exploit the large differences in 85.5 GHz emissivity between first year and multiyear ice to interpret an 85.5 GHz image in terms of both total ice and multiyear ice concentration. Preliminary results, for nearly cloud-free winter conditions, reveal agreement between these interpretations and the NASA Team algorithm to within a standard deviation of +/- 6%, with slightly better agreement at Low multiyear ice concentration.

Suzuki, N, Tytler D, Kirkman D, O'Meara JM, Lubin D.  2005.  Predicting QSO continua in the Ly alpha forest. Astrophysical Journal. 618:592-600.   10.1086/426062   AbstractWebsite

We present a method to make predictions with sets of correlated data values, in this case QSO flux spectra. We predict the continuum in the Lyalpha forest of a QSO, from 1020 to 1216 8, using the spectrum of that QSO from 1216 to 1600 Angstrom. We find correlations between the unabsorbed flux in these two wavelength regions in the Hubble Space Telescope (HST) spectra of 50 QSOs. We use principal component analysis to summarize the variety of these spectra, relate the weights of the principal components for 1020-1600 Angstrom to the weights for 1216-1600 Angstrom, and apply this relation to make predictions. We test the method on the HST spectra and find an average absolute flux error of 9%, with a range of 3%-30%, where individual predictions are systematically too low or too high. We mention several ways in which the predictions might be improved.

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Kirkman, D, Tytler D, Burles S, Lubin D, O'Meara JM.  2000.  QSO 0130-4021: A third QSO showing a low deuterium-to-hydrogen abundance ratio. Astrophysical Journal. 529:655-660.   10.1086/308317   AbstractWebsite

We have discovered a third quasar absorption system which is consistent with a low deuterium-to-hydrogen abundance ratio, D/H = 3.4 x 10(-5). The z(abs) similar to 2.8 partial Lyman limit system toward Q0130-4021 provides the strongest evidence to date against large D/H ratios because the H I absorption, which consists of a single high column density component with unsaturated high-order Lyman series lines, is readily modeled-a task which is more complex in other D/H systems. We have obtained 22 hr of spectra from the High-Resolution Echelle Spectrograph on the W. RI. Keek Telescope, which allow a detailed description of the hydrogen. We see excess absorption on the blue wing of the H I Ly alpha line, near the expected position of deuterium. However, we find that deuterium cannot explain all of the excess absorption, and hence there must be contamination by additional absorption, probably H I. This extra H I can account for most or all of the absorption at the D position, and hence D/H = 0 is allowed. We find an upper limit of D/H less than or equal to 6.7 x 10(-5) in this system, consistent with the value of D/H similar or equal to 3.4 x 10(-5) deduced toward QSO 1009 + 2956 and QSO 1937 - 1009 by Buries and Tytler. This absorption system shows only weak metal-line absorption, and we estimate [Si/H] less than or equal to -2.6, indicating that the D/H ratio of the system is likely primordial. All four of the known high-redshift absorption-line systems simple enough to provide useful limits on D are consistent with D/H = 3.4 +/- 0.25 x 10(-5). Conversely, this QSO provides the third case which is inconsistent with much larger values.

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Collins, WD, Valero FPJ, Flatau PJ, Lubin D, Grassl H, Pilewskie P.  1996.  Radiative effects of convection in the tropical Pacific. Journal of Geophysical Research-Atmospheres. 101:14999-15012.   10.1029/95jd02534   AbstractWebsite

The radiative effects of tropical clouds at the tropopause and the ocean surface have been estimated by using in situ measurements from the Central Equatorial Pacific Experiment (CEPEX). The effect of clouds is distinguished from the radiative effects of the surrounding atmosphere by calculating the shortwave and longwave cloud forcing. These terms give the reduction in insolation and the increase in absorption of terrestrial thermal emission associated with clouds. At the tropopause the shortwave and longwave cloud forcing are nearly equal and opposite, even on daily timescales. Therefore the net effect of an ensemble of convective clouds is small compared to other radiative terms in the surface-tropospheric heat budget. This confirms the statistical cancellation of cloud forcing observed in Earth radiation budget measurements from satellites. At the surface the net effect of clouds is to reduce the radiant energy absorbed by the ocean. Under deep convective clouds the diurnally averaged reduction exceeds 150 W m(-2). The divergence of flux in the cloudy atmosphere can be estimated from the difference in cloud forcing at the surface and tropopause. The CEPEX observations show that the atmospheric cloud forcing is nearly equal and opposite to the surface forcing. Based upon the frequency of convection, the atmospheric forcing approaches 100 W m(-2) when the surface temperature is 303 K. The cloud forcing is closely related to the frequency of convective cloud systems. This relation is used in conjunction with cloud population statistics derived from satellite to calculate the change in surface cloud forcing with sea surface temperature. The net radiative cooling of the surface by clouds increases at a rate of 20 W m(-2)K(-1)during the CEPEX observing period.

Lubin, D, Massom R.  2007.  Remote sensing of Earth's polar regions - Opportunities for computational science. Computing in Science & Engineering. 9:58-71.   10.1109/mcse.2007.16   AbstractWebsite

Polar remote sensing offers numerous opportunities for computer scientists, including spacecraft design and data processing, the development of algorithms for geophysical product retrieval, operational assistance for aircraft and ship navigation, and database management at national archives.

Lubin, D, Ayres G, Hart S.  2009.  REMOTE SENSING OF POLAR REGIONS Lessons and Resources for the International Polar Year. Bulletin of the American Meteorological Society. 90:825-+.   10.1175/2008bams2596.1   AbstractWebsite

Polar researchers have historically been innovative and adaptive users of satellite remote sensing data, and their experiences can suggest ways to enhance the use of remote sensing throughout the climate sciences. We performed a semistructured survey of the polar research community on the use of remote sensing at the beginning of the NASA Earth Observing System (EOS) era. For the most part, remote sensing plays a supporting but critical role in the research as described by the respondents. Data acquisition and analysis is mostly at the home institution, with field telemetry appearing in a small minority of responses. Most polar researchers have not had formal training in remote sensing, but they have adapted and trained themselves very thoroughly. Although a significant number of polar researchers are content with visual inspection of satellite images, a roughly equal number develop their own algorithms for derivation of geophysical products, and more have become adept at using high-level graphical programming languages to work with data. Given the self-sufficiency in remote sensing training that characterizes polar researchers, nontraditional satellite data users (e.g., life scientists) tend to view the "learning curve" as steep, as compared with physical scientists. Although up to a third of respondents report no significant obstacles in accessing satellite data, obstacles such as a) difficulty locating data centers for their needs, b) the cost of acquiring data, and c) insider or restricted access to data were each reported by about one-quarter of the respondents. The major ongoing challenges with remote sensing in polar research can be met with aspects of modern cyberinfrastructure involving data interoperability.

Han, W, Stamnes K, Lubin D.  1999.  Remote sensing of surface and cloud properties in the Arctic from AVHRR measurements. Journal of Applied Meteorology. 38:989-1012.   10.1175/1520-0450(1999)038<0989:rsosac>2.0.co;2   AbstractWebsite

Algorithms to retrieve cloud optical depth and effective radius in the Arctic using Advanced Very High Resolution Radiometer (AVHRR) data are developed, using a comprehensive radiative transfer model in which the atmosphere is coupled to the snowpack. For dark surfaces AVHRR channel 1 is used to derive visible cloud optical depth, while for bright surfaces AVHRR channel 2 is used. Independent inference of cloud effective radius from AVHRR channel 3 (3.75 mu m) allows for derivation cloud liquid water path (proportional to the product of optical depth and effective radius). which is a fundamental parameter of the climate system. The algorithms are based on the recognition that the reflection function of clouds at a nonabsorbing wavelength (such as AVHRR channel 1) in the solar spectrum is primarily a function of cloud optical thickness, whereas the reflection function at a liquid water absorbing wavelength (such as AVHRR channel 3) is primarily a function of cloud particle size. For water clouds over highly reflecting surfaces (snow and ice), the reflectance in AVHRR channel 1 is insensitive to cloud optical depth due to the multiple reflections between cloud base and the underlying surface; channel 2 (0.85 mu m) must be used instead for optical depth retrieval. Water clouds over tundra or ocean are more straightforward cases similar to those found at lower latitudes, and in these cases a comprehensive atmospheric radiative transfer model with a Lambertian surface under cloud is used. Thus, for water cloud over tundra and ocean, channel 1 is used for cloud optical depth retrieval. In all cases, channel 3 is used for independent retrieval of cloud droplet effective radius. The thermal component of channel 3 is estimated by making use of channel 4 (11 mu m) and is subtracted from the total channel 3 radiance. Over clear-sky scenes, the bidirectional reflectance properties of snow are calculated directly by the coupled snowpack-atmosphere model. This results in greater overall accuracy in retrieved surface properties as compared with the simplified approach that uses a Lambertian approximation for the surface albedo. To test the physical soundness of the algorithms the authors have applied them to AVHRR data over Barrow, Alaska, from April to August 1992. Downwelling irradiances at the surface calculated using the retrieved cloud optical depth and effective radius are compared with field irradiance measurements, and encouraging agreement is found. The algorithms are also applied to three areas of about 100-km dimension around Barrow, each having a different underlying surface (ocean, tundra, snow).

Tytler, D, O'Meara JM, Suzuki N, Lubin D.  2000.  Review of big bang nucleosynthesis and primordial abundances. Physica Scripta. T85:12-31.   10.1238/Physica.Topical.085a00012   AbstractWebsite

Big Bang Nucleosynthesis (BBN) is the synthesis of the light nuclei, Deuterium (D or H-2), He-3, He-4 and Li-7 during the first few minutes of the universe. This review concentrates on recent improvements in the measurement of the primordial (after BBN, and prior to modification) abundances of these nuclei. We mention improvement in the standard theory, and the non-standard extensions which are limited by the data. We have achieved an order of magnitude improvement in the precision of the measurement of primordial D/H, using the HIRES spectrograph on the W M. Keck telescope to measure D in gas with very nearly primordial abundances towards quasars. From 1994 - 1996, it appeared that there could be a factor of ten range in primordial D/H, but today four examples of low D are secure. High D/H should be much easier to detect, and since there are no convincing examples, it must be extremely rare or non-existent. All data are consistent with a single low value for D/H, and the examples which an consistent with high D/H are readily interpreted as H contamination near the position of D. The new D/H measurements give the most accurate value for the baryon to photon ratio II, and hence the cosmological baryon density. A similar density is required to explain the amount of Ly alpha absorption from neutral Hydrogen in the intergalactic medium (IGM) at redshift z similar or equal to 3, and to explain the fraction of baryons in local clusters of galaxies. The D/H measurements lead to predictions for the abundances of the other light nuclei, which generally agree with measurements. The remaining differences with some measurements can be explained by a combination of measurement and analysis errors or changes in the abundances after BBN. The measurements do not require physics beyond the standard BBN model. instead, the agreement between the abundances is used to limit the non-standard physics. New measurements are giving improved understanding of the difficulties in estimating the abundances of all the light nuclei, but unfortunately in most cases we are not yet seeing much improvement in the accuracy of the primordial abundances. Since we are now interested in the highest accuracy and reliability for all nuclei, the few objects with the most extensive observations give by far the most convincing results. Earlier measurements of He-4 may have obtained too low a value because the He emission line strengths were reduced by undetected stellar absorption lines. The systematic errors associated with the He-4 abundance have frequently been underestimated in the past, and this problem persists. When two groups use the same data and different ways to estimate the electron density and He-4 abundance, the results differ by more than the quoted systematic errors. While the methods used by Izotov and Thuan [1] seem to be an advance on those used before, the other method is reasonable, and hence the systematic error should encompass the range in results. The abundance of Li-7 is measured to high accuracy, but we do not know how much was produced prior to the formation of the stars, and how much was destroyed (depleted) in the stars. Li-6 helps limit the amount of depletion of Li-7, but by an uncertain amount since it too has been depleted. BBN is successful because it uses known physics and measured cross-sections for the nuclear reactions. It gives accurate predictions for the abundances of five light nuclei as a function of the one free parameter eta. The other initial conditions seem natural: the universe began homogeneous and hotter than T > 10(11) K (30 Mev). The predicted abundances agree with most observations, and the required eta is consistent with other, less accurate, measurements of the baryon density. Abundance measurements of the baryon density, from the CMB, clusters of galaxies and the Ly alpha forest, will give II. Although the accuracy might not exceed that obtained from D/H, this is an important advance because BBN then gives abundance predictions with no adjustable parameters. New measurement in the coming years will give improved accuracy. Measurement of D/H in many more quasar spectra would improve the accuracy of D/H by a factor of a few, to a few percent, but even with improved methods of selecting the target quasars, this would need much more time on the largest telescopes. More reliable He-4 abundances might be obtained from spectra which have higher spectral and spatial resolution, to help correct for stellar absorption, higher signal to noise to show weaker emission lines, and more galaxies with low metal abundances, to minimize the extrapolation to primordial abundances. Measurements of Li-6, Be and Boron in the same stars and observations of a variety of stars should give improved models for the depletion of Li-7 in halo stars, and hence tighter constraints on the primordial abundance. However, in general, it is hard to think of any new methods which could give any primordial abundances with an order of magnitude higher accuracy than those used today. This is a major unexploited opportunity because it means that we can not yet test BBN to the accuracy of the predictions.

Lubin, D.  1994.  The Role of the Tropical Super Greenhouse-Effect in Heating the Ocean Surface. Science. 265:224-227.   10.1126/science.265.5169.224   AbstractWebsite

Measurements made by a Fourier transform infrared (FTIR) spectroradiometer operating in the middle infrared (5 to 20 micrometers, with a spectral resolution of one inverse centimeter) imply that there is an anomalously large greenhouse effect over equatorial oceans that is caused by water vapor. As sea-surface temperature increased from 297 to 303 degrees kelvin, the net infrared cooling at the surface decreased by 30 to 50 watts per square meter. Thus, according to the FTIR data, the super greenhouse effect that had been inferred from satellite measurements contributes directly to radiative heating of the sea surface. The data demonstrate that most of this heating occurs in the middle infrared by means of the continuum emission window of water vapor and that tropical deep convection contributes substantially to this super greenhouse effect.

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Lubin, D, Jensen EH.  1997.  Satellite mapping of solar ultraviolet radiation at the earth's surface. Solar ultraviolet radiation : modelling, measurements, and effects. ( Zerefos CS, Bais AF, Eds.)., Berlin; New York: Springer Abstract
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Satheesh, SK, Lubin D.  2003.  Short wave versus long wave radiative forcing by Indian Ocean aerosols: Role of sea-surface winds. Geophysical Research Letters. 30   10.1029/2003gl017499   AbstractWebsite

[1] Recent observations over the Indian Ocean have demonstrated aerosol short wave absorption as high as 20 to 25 W m(-2). The aerosol net radiative forcing reduces substantially while considering the broad spectrum including the long wave region (due to large infrared forcing which is opposite in sign). At highwinds, presence of large amounts of sea-salt aerosols (absorbing in infrared) enhances the infrared forcing; hence reduces the net radiative forcing. In this paper, we examine the role of sea-surface winds (which enhance sea-salt aerosols) on long wave aerosol forcing. Even at moderate winds (6-10 m s(-1)), the short wave forcing reduces by similar to45% due to the dominance of sea-salt aerosols. At high winds (>10 m s(-1)), a major fraction of the long wave forcing is contributed by sea-salt (more than 70%). Our studies show that neglecting aerosol long wave radiative forcing can cause large errors in climate models.

Lubin, D, Ricchiazzi P, Payton A, Gautier C.  2002.  Significance of multidimensional radiative transfer effects measured in surface fluxes at an Antarctic coastline. Journal of Geophysical Research-Atmospheres. 107   10.1029/2001jd002030   AbstractWebsite

[1] At a coastal high-latitude site, multiple reflection of photons between the high albedo surface and an overlying cloud can enhance the downwelling shortwave flux out over the adjacent open water to a distance of several kilometers. This coastal albedo effect has been predicted by theoretical radiative transfer studies and has also been measured under ideal conditions. In this study, three multispectral solar ultraviolet radiometers were deployed in the vicinity of Palmer Station, Antarctica (64degrees 46'S, 64degrees 04'W) to determine the prevalence of the coastal albedo effect under the region's natural variability in cloud cover. One radiometer was deployed near the base of a glacier, and the other two radiometers were deployed on Janus Island and Outcast Island, islets similar to2.8 km (1.5 nautical miles) and 5.6 km (3 nautical miles) distant from Palmer Station, respectively. The radiometers were operated simultaneously for 16 days during late December 1999 and January 2000. Under all cloudy sky conditions sampled by this experiment the coastal albedo effect is seen in the data 60% of the time, in the form of a decreasing gradient in surface flux from Palmer Station through Janus and Outcast Islands. During the other 40% of the cloudy sky measurements, local cloud inhomogeneity obscured the coastal albedo effect. The effect is more apparent under overcast layers that appear spatially uniform and occurs 86% of the time under the low overcast decks sampled. The presence of stratus fractus of bad weather, under higher overcast layers, obscures the coastal albedo effect such that it occurs only 43% of the time. A wavelength dependence is noted in the data under optically thin cloud cover: the ratio of a flux measured at an islet to that measured at the station increases with wavelength. This wavelength dependence can be explained by plane-parallel radiative transfer theory.

Morrow, E, Scheeres DJ, Lubin D.  2001.  Solar sail orbit operations at asteroids. Journal of Spacecraft and Rockets. 38:279-286.   10.2514/2.3682   AbstractWebsite

The inherent capabilities of solar sails and that they need no onboard supplies of fuel for propulsion make them well suited for use in long-term, multiple-objective missions. They are especially well suited for the exploration of asteroids, where one spacecraft could rendezvous with a number of asteroids in succession. The orbital mechanics of solar sail operations about an asteroid, however, have not yet been studied in detail. Building an previous studies, we find both hovering points and orbiting trajectories about various sized asteroids using equations of motion for a solar sail spacecraft. The orbiting trajectories are stable and offer good coverage of the asteroid surface, although restrictions on sail acceleration are needed for smaller asteroids.

Holm-Hansen, O, Lubin D.  1994.  Solar ultraviolet radiation: effect on rates of CO2 fixation in marine phytoplankton. Regulation of atmospheric CO2 and O2 by photosynthetic carbon metabolism. ( Tolbert NE, Preiss J, Eds.).:55-74., New York; Oxford: Oxford University Press Abstract
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