Publications

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Book Chapter
Lubin, D, Holm-Hansen O.  1995.  Atmospheric ozone and the biological impact of solar ultraviolet radiation. Encyclopedia of environmental biology. Vol. 1, A-E. 1( Nierenberg WA, Ed.).:147-168.: Academic Press Abstract
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Tytler, D, O'Meara JM, Suzuki N, Lubin D, Burles S, Kirkman D.  2000.  Measurements of the primordial D/H abundance towards quasars. Light Elements and Their Evolution. ( DaSilva L, Spite M, DeMedeiros JR, Eds.).:125-134., San Francisco: Astronomical Soc Pacific Abstract

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. In this review we concentrate on recent data which give the primordial deuterium (D) abundance. We have measured the primordial D/H in gas with very nearly primordial abundances. We use the Lyman series absorption lines seen in the spectra of quasars. We have measured D/H towards three QSOs, while a fourth gives a consistent upper limit. All QSO spectra are consistent with a single value for D/H: 3.325(-0.25)(+0.22) x 10(-5). From about 1994-1996, there was much discussion of the possibility that some QSOs show much higher D/H, but the best such example was shown to be contaminated by H, and no other no convincing examples have been found. Since high D/H should be much easier to detect, and hence it must be extremely rare or non-existent. The new D/H measurements give the most accurate value for the baryon to photon ratio, eta, and hence the cosmological baryon density: Omega(b) = 0.0190 +/- 0.0009 (1sigma) A similar density is required to explain the amount of Lyalpha 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.

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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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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Kerr, J, Seckmeyer G, Bais AF, Bernhard G, Blumthaler M, Diaz SB, Krotkov NA, Lubin D, Mckenzie RL, Sabziparvar AA, Verdebout J.  2002.  Surface Ultraviolet Radiation: Past and Future. Scientific assessment of ozone depletion, 2002. Executive summary. ( Organization W, Ed.).:5.1-5.46., [Washington, D.C.]; [Nairobi, Kenya]; [Geneva, Switzerland]; [Brussels, Belgium]: National Oceanic and Atmospheric Administration : National Aeronautics and Space Administration ; United Nations Environment Programme ; World Meteorological Organization ; European Commission Abstract
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Bais, AF, Lubin D, Arola A, Bernhard G, Blumthaler M, Chubarova N, Erlick C, Gies HP, Krotkov NA, Lantz K, Mayer B, Mckenzie RL, d. Piacentini R, Seckmeyer G, Slusser JR, Zerefos CZ.  2007.  Surface Ultraviolet Radiation: Past, Present, and Future. Scientific assessment of ozone depletion: 2006. ( Organization W, Ed.)., Geneva, Switzerland: World Meteorological Organization Abstract
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Lubin, D, Holm-Hansen O, Helbling EW.  1993.  Ultraviolet radiation and its effects on organisms in aquatic environments. Environmental UV photobiology. ( Young AR, Ed.).:379-345., New York: Plenum Press Abstract
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Journal Article
Lubin, D, Wittenmyer RA, Bromwich DH, Marshall GJ.  2008.  Antarctic Peninsula mesoscale cyclone variability and climatic impacts influenced by the SAM. Geophysical Research Letters. 35   10.1029/2007gl032170   AbstractWebsite

The frequency of mesoscale cyclones in the Western Antarctic Peninsula (WAP) region during 1991-94 is correlated with the Southern Hemisphere Annular Mode (SAM) index, most strongly during winter and spring. Also, during periods of positive SAM index polarity there is a shift in the storm tracks to favor more east-bound trajectories, consistent with strengthening of circumpolar westerlies. The presence of mesoscale cyclones is associated with positive near-surface-air temperature anomalies in the WAP region year-round, largest during winter.

Smith, WL, Hansen C, Bucholtz A, Anderson BE, Beckley M, Corbett JG, Cullather RI, Hines KM, Hofton M, Kato S, Lubin D, Moore RH, Rosenhaimer MS, Redemann J, Schmidt S, Scott R, Song S, Barrick JD, Blair JB, Bromwich DH, Brooks C, Chen G, Cornejo H, Corr CA, Ham SH, Kittelman AS, Knappmiller S, LeBlanc S, Loeb NG, Miller C, Nguyen L, Palikonda R, Rabine D, Reid EA, Richter-Menge JA, Pilewswskie P, Shinozuka Y, Spangenberg D, Stackhouse P, Taylor P, Thornhill KL, Van Gilst D, Winstead E.  2017.  ARCTIC RADIATION-ICEBRIDGE SEA AND ICE EXPERIMENT The Arctic Radiant Energy System during the Critical Seasonal Ice Transition. Bulletin of the American Meteorological Society. 98:1399-1426.   10.1175/bams-d-14-00277.1   AbstractWebsite

Through ARISE, NASA acquired unique aircraft data on clouds, atmospheric radiation and sea ice properties during the critical period between the sea ice minimum in late summer and autumn and the commencement of refreezing.

McComiskey, A, Ricchiazzi P, Gautier C, Lubin D.  2006.  Assessment of a three dimensional model for atmospheric radiative transfer over heterogeneous land cover. Geophysical Research Letters. 33   10.1029/2005gl025356   AbstractWebsite

A three-dimensional (3D) atmospheric radiative transfer model that explicitly represents surface albedo heterogeneity is tested against a one-dimensional model and surface irradiance observations in a polar region where land cover heterogeneity is high. For observations located near high latitude coastlines, the contrast between the highly absorbing ocean and reflective snow surface creates spatial heterogeneity, or a 3D effect, around the observation site. The resulting effect on radiation at the sensor should be taken into account when using a solar radiative transfer model to interpret measurements. This assessment shows that better closure is obtained with a three-dimensional model (<= 5%) versus a plane-parallel model (<= 7%). The importance of the surface 3D effect increases with aerosol or cloud optical depth and with surface albedo contrast. The model used here can be implemented at any surface site given the surrounding land cover properties.

Kahn, BH, Irion FW, Dang VT, Manning EM, Nasiri SL, Naud CM, Blaisdell JM, Schreier MM, Yue Q, Bowman KW, Fetzer EJ, Hulley GC, Liou KN, Lubin D, Ou SC, Susskind J, Takano Y, Tian B, Worden JR.  2014.  The Atmospheric Infrared Sounder version 6 cloud products. Atmospheric Chemistry and Physics. 14:399-426.   10.5194/acp-14-399-2014   AbstractWebsite

The version 6 cloud products of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) instrument suite are described. The cloud top temperature, pressure, and height and effective cloud fraction are now reported at the AIRS field-of-view (FOV) resolution. Significant improvements in cloud height assignment over version 5 are shown with FOV-scale comparisons to cloud vertical structure observed by the CloudSat 94 GHz radar and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP). Cloud thermodynamic phase (ice, liquid, and unknown phase), ice cloud effective diameter (D-e), and ice cloud optical thickness (tau) are derived using an optimal estimation methodology for AIRS FOVs, and global distributions for 2007 are presented. The largest values of tau are found in the storm tracks and near convection in the tropics, while D-e is largest on the equatorial side of the midlatitude storm tracks in both hemispheres, and lowest in tropical thin cirrus and the winter polar atmosphere. Over the Maritime Continent the diurnal variability of tau is significantly larger than for the total cloud fraction, ice cloud frequency, and D-e, and is anchored to the island archipelago morphology. Important differences are described between northern and southern hemispheric midlatitude cyclones using storm center composites. The infrared-based cloud retrievals of AIRS provide unique, decadal-scale and global observations of clouds over portions of the diurnal and annual cycles, and capture variability within the mesoscale and synoptic scales at all latitudes.

Tytler, D, O'Meara JM, Suzuki N, Lubin D.  2000.  Big bang nucleosynthesis. Nuclear Physics B-Proceedings Supplements. 87:464-473.   10.1016/s0920-5632(00)00721-0   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.

Podgorny, I, Lubin D.  1998.  Biologically active insolation over Antarctic waters: Effect of a highly reflecting coastline. Journal of Geophysical Research-Oceans. 103:2919-2928.   10.1029/97jc02763   AbstractWebsite

Near an Antarctic coastline or sea ice edge, multiple reflection of photons between the high-albedo surface and a cloud will increase the downwelling surface insolation not only over the high-albedo surface itself but also out over the adjacent open water. This insolation enhancement is examined with a Monte Carlo radiative transfer model. The insolation enhancement extends to a typical distance of 4 km out to sea, with the most important effects being within 2 km of the coastline. The strength of the multiple reflection effect depends primarily on cloud base height and cloud optical depth and only slightly on cloud geometrical thickness. The insolation enhancement is also a function of wavelength, being larger for ultraviolet wavelengths than for the visible. This is due to a slightly greater contribution from Rayleigh scattering at the shorter wavelengths, although at ultraviolet wavelengths where ozone absorption is strong, tropospheric ozone absorption can offset the Rayleigh scattering contribution at larger cloud optical depths. On the basis of the limited range of the multiple reflection effect (2-4 km out to sea) the insolation enhancement due to the high-albedo coastline is unlikely to be a major influence on the primary productivity of all Antarctic waters; however, it may influence phytoplankton blooms near the coast and photobiological experiments carried out at coastal research stations. Also, the insolation enhancement may have significance in sea ice leads and polynyas.

Frederick, JE, Lubin D.  1988.  The Budget of Biologically-Active Ultraviolet-Radiation in the Earth-Atmosphere System. Journal of Geophysical Research-Atmospheres. 93:3825-3832.   10.1029/JD093iD04p03825   AbstractWebsite

This study applies the concept of a budget to describe the interaction of solar ultraviolet (UV) radiation with the Earth-atmosphere system. The wavelength ranges of interest are the biologically relevant UV-B between 280 and 320 nm and the UV-A from 320 to 400 nm. The Nimbus 7 solar backscattered ultraviolet (SBUV) instrument provides measurements of total column ozone and information concerning cloud cover which, in combination with a simple model of radiation transfer, define the fractions of incident solar irradiance absorbed in the atmosphere, reflected to space, and absorbed at the ground. Results for the month of July quantify the contribution of fractional cloud cover and cloud optical thickness to the radiation budget's three components. Scattering within a thick cloud layer makes the downward radiation field at the cloud base more isotropic than is the case for clear skies. For small solar zenith angles, typical of summer midday conditions, the effective path length of this diffuse irradiance through tropospheric ozone is greater than that under clear-sky conditions. The result is an enhanced absorption of UV-B radiation in the troposphere during cloud-covered conditions. Major changes in global cloud cover or cloud optical thicknesses could alter the ultraviolet radiation received by the biosphere by an amount comparable to that predicted for long-term trends in ozone.

Lubin, D, Vogelmann AM.  2006.  A climatologically significant aerosol longwave indirect effect in the Arctic. Nature. 439:453-456.   10.1038/nature04449   AbstractWebsite

The warming of Arctic climate and decreases in sea ice thickness and extent(1,2) observed over recent decades are believed to result from increased direct greenhouse gas forcing, changes in atmospheric dynamics having anthropogenic origin(3-5), and important positive reinforcements including ice - albedo and cloud - radiation feedbacks(6). The importance of cloud - radiation interactions is being investigated through advanced instrumentation deployed in the high Arctic since 1997 (refs 7, 8). These studies have established that clouds, via the dominance of longwave radiation, exert a net warming on the Arctic climate system throughout most of the year, except briefly during the summer(9). The Arctic region also experiences significant periodic influxes of anthropogenic aerosols, which originate from the industrial regions in lower latitudes(10). Here we use multisensor radiometric data(7,8) to show that enhanced aerosol concentrations alter the microphysical properties of Arctic clouds, in a process known as the 'first indirect' effect(11,12). Under frequently occurring cloud types we find that this leads to an increase of an average 3.4 watts per square metre in the surface longwave fluxes. This is comparable to a warming effect from established greenhouse gases and implies that the observed longwave enhancement is climatologically significant.

Wilson, A, Scott RC, Cadeddu MP, Ghate V, Lubin D.  2018.  Cloud optical properties over West Antarctica from shortwave spectroradiometer measurements during AWARE. Journal of Geophysical Research-Atmospheres. 123:9559-9570.   10.1029/2018jd028347   AbstractWebsite

A shortwave spectroradiometer was deployed on the West Antarctic Ice Sheet (WAIS) as part of the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program ARM West Antarctic Radiation Experiment (AWARE). This instrument recorded 1-min averages of downwelling hemispheric spectral irradiance covering the wavelength range 350-2,200nm with spectral resolution 3 and 10nm for wavelengths shorter and longer than 1,000nm, respectively. Using simultaneous micropulse lidar data to identify the thermodynamic phase of stratiform clouds, a radiative transfer algorithm is used to retrieve optical depth and effective droplet (or particle) size for single-phase liquid water and ice water clouds. The AWARE campaign on the WAIS first sampled typical climatological conditions between 7 December 2015 and 9 January 2016 and then a much warmer air mass with more moisture associated with a surface melt event between 10 and 17 January 2016. Before the melt event most liquid cloud effective droplet radii were consistent with pristine polar maritime clouds (mode radius 13.5m) but showed a second local maximum in the distribution (at 8m) consistent with colder, moisture-limited conditions. Most ice clouds sampled occurred before the melt event (mode optical depth 4 and effective particle size 19m). During the melt event liquid water cloud optical depth nearly doubled (mode value increasing from 8 to 14). AWARE therefore sampled on the WAIS two cases relevant to climate model simulations: typical current climatological conditions, followed by warmer meteorology possibly consistent with future increasing surface melt scenarios.

Mulmenstadt, J, Lubin D, Russell LM, Vogelmann AM.  2012.  Cloud properties over the North Slope of Alaska: Identifying the prevailing meteorological regimes. Journal of Climate. 25:8238-8258.   10.1175/jcli-d-11-00636.1   AbstractWebsite

Long time series of Arctic atmospheric measurements are assembled into meteorological categories that can serve as test cases for climate model evaluation. The meteorological categories are established by applying an objective k-means clustering algorithm to 11 years of standard surface-meteorological observations collected from 1 January 2000 to 31 December 2010 at the North Slope of Alaska (NSA) site of the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM). Four meteorological categories emerge. These meteorological categories constitute the first classification by meteorological regime of a long time series of Arctic meteorological conditions. The synoptic-scale patterns associated with each category, which include well-known synoptic features such as the Aleutian low and Beaufort Sea high, are used to explain the conditions at the NSA site. Cloud properties, which are not used as inputs to the k-means clustering, are found to differ significantly between the regimes and are also well explained by the synoptic-scale influences in each regime. Since the data available at the ARM NSA site include a wealth of cloud observations, this classification is well suited for model observation comparison studies. Each category comprises an ensemble of test cases covering a representative range in variables describing atmospheric structure, moisture content, and cloud properties. This classification is offered as a complement to standard case-study evaluation of climate model parameterizations, in which models are compared against limited realizations of the Earth atmosphere system (e.g., from detailed aircraft measurements).

Lubin, D, Harper DA.  1996.  Cloud radiative properties over the South Pole from AVHRR infrared data. Journal of Climate. 9:3405-3418.   10.1175/1520-0442(1996)009<3405:crpots>2.0.co;2   AbstractWebsite

Over the Antarctic plateau, the radiances measured by the AVHRR middle infrared (11 and 12 mu m) channels are shown to depend on effective cloud temperature, emissivity, ice water path, and effective radius of the particle size distribution. The usefulness of these dependencies is limited by radiometric uncertainties of up to 2 K in brightness temperature and by the fact that the radiative transfer solutions are not single valued over all possible ranges of temperature, effective radius, and ice water path. Despite these limitations, AVHRR imagery can be used to characterize cloud optical properties over the Antarctic continent if surface weather observations and/or radiosonde data can be collocated with the satellite overpasses. From AVHRR imagery covering the South Pole during 1992, the mean cloud emissivity is estimated at 0.43 during summer and 0.37 during winter, while the mean summer and winter effective radii are estimated at 12.3 and 5.6 mu m, respectively. When a radiative transfer model is used to evaluate these results in comparison with surface pyrgeometer measurements, the comparison suggests that the AVHRR retrieval method captures the overall seasonal behavior in cloud properties. During months when the polar vortex persists, AVHRR infrared radiances may be noticeably influenced by polar stratospheric clouds.

Ricchiazzi, P, Gautier C, Lubin D.  1995.  Cloud Scattering Optical Depth and Local Surface Albedo in the Antarctic - Simultaneous Retrieval Using Ground-Based Radiometry. Journal of Geophysical Research-Atmospheres. 100:21091-21104.   10.1029/95jd01461   AbstractWebsite

We have used solar irradiance measurements from a ground-based multichannel radiometer system deployed at Palmer Station, Antarctica (64 degrees 46'S, 64 degrees 04'W), during spring 1991 to simultaneously estimate cloud scattering optical depth and surface albedo. Irradiance measurements at 410 and 630 nm, in conjunction with a discrete ordinate radiative transfer (RT) model, enable this simultaneous retrieval by exploiting the wavelength dependence in Rayleigh scattering strength. The RT model is used in an inverse mode to find the values of surface albedo and cloud optical depth that match calculated and measured irradiances at both wavelengths. Under the homogeneous stratiform cloud cover for which the technique applies, surface albedo at 630 nm was consistently retrieved at above 0.9. For most homogeneous, overcast conditions, cloud optical depth (at 630 nm) is found to be in the range 20-50, with a most probable value of 25. This measurement and retrieval technique should be useful for compiling high-latitude cloud opacity and surface albedo climatologies of interest for global change and photobiology research.

Lubin, D, Frederick JE.  1990.  Column Ozone Measurements from Palmer-Station, Antarctica - Variations During the Austral Springs of 1988 and 1989. Journal of Geophysical Research-Atmospheres. 95:13883-13889.   10.1029/JD095iD09p13883   AbstractWebsite

The National Science Foundation scanning spectroradiometer at Palmer Station, Antarctica (64°46′S, 64°04′W), provides hourly ground-based measurements of solar ultraviolet (UV) irradiance. In addition to defining the UV 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 UV surface irradiance associated with the dynamics of the polar vortex. Column ozone abundance is derived from a ratio of measured irradiances at 300 and 313.5 nanometers (nm) by means of theoretical calculation of this ratio as a function of total ozone amount. Noontime ozone abundances over Palmer Station obtained from this method agree with those obtained by the Total Ozone Mapping Spectrometer (TOMS) instrument aboard Nimbus 7 to within about 10% throughout the austral spring of 1988. Ozone recovery at Palmer Station, associated with the breakup of the polar vortex as indicated by TOMS satellite ozone observations, occurred rapidly within a 24-hour period beginning in midafternoon on November 15. Over the Antarctic Peninsula, the 1989 ozone depletion was slightly greater than in 1988, the minimum noontime ozone abundances over Palmer Station as measured by the spectroradiometer being 194 and 166 Dobson units for October 14, 1988, and October 14, 1989, respectively. The 1989 ozone depletion however ended by November 5 over the Antarctic Peninsula, 10 days earlier than the 1988 event.

Lubin, D, Mitchell BG, Frederick JE, Alberts AD, Booth CR, Lucas T, Neuschuler D.  1992.  A Contribution toward Understanding the Biospherical Significance of Antarctic Ozone Depletion. Journal of Geophysical Research-Atmospheres. 97:7817-7828.   10.1029/91JD01400   AbstractWebsite

Measurements of biologically active UV radiation made by the National Science Foundation (NSF) scanning spectroradiometer (UV-monitor) at Palmer Station. Antarctica, during the Austral springs of 1988, 1989, and 1990 are presented and compared. Column ozone abundance above Palmer Station is computed from these measurements using a multiple wavelength algorithm. Two contrasting action spectra (biological weighting functions) are used to estimate the biologically relevant (dose from the spectral measurements: a standard weighting function for damage to DNA, and a new action spectrum representing the potential for photosynthesis inhibition in Antarctic phytoplankton. The former weights only UV-B wavelengths (280-320 nm) and gives the most weight to wavelengths shorter than 300 nm, while the latter includes large contributions out to 355 nm. The latter is the result of recent Antarctic field work and is relevant in that phytoplankton constitute the base of the Antarctic food web. The modest ozone hole of 1988, in which the ozone abundance above Palmer Station never fell below 200 Dobson units (DU), brought about summerlike doses of DNA-effective UV radiation 2 months early, but UV doses which could inhibit photosynthesis in phytoplankton did not exceed a clear-sky "maximum normal" dose for that time of year. The severe ozone holes of 1989 and 1990, in which the ozone abundance regularly fell below 200 DU, brought about increases in UV surface irradiance weighted by either action spectrum. Ozone abundances and dose-weighted irradiances provided by the NSF UV-monitor are used to derive the radiation amplification factors (RAFs) for both DNA-effective irradiance and phytoplankton-effective irradiance. The RAF for DNA-effective irradiance is nonlinear in ozone abundance and is in excess of the popular "two for one" rule, while the RAF for phytoplankton-effective irradiance approximately follows a "one for one" rule.

Xiong, XZ, Lubin D, Li W, Stamnes K.  2002.  A critical examination of satellite cloud retrieval from AVHRR in the Arctic using SHEBA data. Journal of Applied Meteorology. 41:1195-1209.   10.1175/1520-0450(2002)041<1195:aceosc>2.0.co;2   AbstractWebsite

This study examines the validity and limitations associated with retrieval of cloud optical depth tau and effective droplet size r(e) in the Arctic from Advanced Very High Resolution Radiometer ( AVHRR) channels 2 (0.725-1.10 mum), 3 (3.55-3.93 mum), and 4 (10.3-11.3 mum). The error in r(e) is found to be normally less than 10%, but the uncertainty in tau can be more than 50% for a 10% uncertainty in the satellite- measured radiance. Model simulations show that the satellite- retrieved cloud optical depth tau(sat) is overestimated by up to 20% if the vertical cloud inhomogeneity is ignored and is underestimated by more than 50% if overlap of cirrus and liquid water clouds is ignored. Under partially cloudy conditions, tau(sat) is larger than that derived from surface-measured downward solar irradiance (tau(surf)) by 40%-130%, depending on cloud-cover fraction. Here, tau(sat) derived from NOAA-14 AVHRR data agrees well with tau(surf) derived from surface measurements of solar irradiance at the Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp in summer, but tau(sat) is about 2.3 times tau(surf) before the onset of snowmelt. This overestimate of tau(sat) is mainly due to the high reflectivity in AVHRR channel 2 over snow/ ice surfaces, the presence of partial cloud cover, and inaccurate representation of the scattering phase function for mixed-phase clouds.

Xiong, XZ, Storvold R, Stamnes K, Lubin D.  2004.  Derivation of a threshold function for the Advanced Very High Resolution Radiometer 3.75 mu m channel and its application in automatic cloud discrimination over snow/ice surfaces. International Journal of Remote Sensing. 25:2995-3017.   10.1080/01431160310001619553   AbstractWebsite

The distinct contrast between the reflectance of solar radiation in Advanced Very High Resolution Radiometer (AVHRR) channel 3 (3.75 mum) by clouds and by bright surfaces provides an effective means of cloud discrimination over snow/ice surfaces. A threshold function for the top-of-atmosphere (TOA) albedo in channel 3 (r(3)) is derived and used to develop an improved method for cloud discrimination over snow/ice surfaces that makes explicit use of TOA r(3) . Corrections for radiance anisotropy and temperature effects are required to derive accurate values of r(3) from satellite measurements and to utilize the threshold function. It has been used to retrieve cloud cover fractions from National Oceanic and Atmospheric Administration (NOAA)-14 AVHRR data over the Arctic Ocean and over the North Slope of Alaska (NSA) Atmospheric Radiation Measurement (ARM) site in Barrow, Alaska. The retrieved cloud fractions are in good agreement with SHEBA (Surface HEat Budget of the Arctic Ocean) surface visual observations and with NSA cloud radar and lidar observations, respectively. This method can be utilized to improve cloud discrimination over snow/ice surfaces for any satellite sensor with a channel near 3.7 mum.

Collins, WD, Bucholtz A, Flatau P, Lubin D, Valero FPJ, Weaver CP, Pilewski P.  2000.  Determination of surface heating by convective cloud systems in the central equatorial Pacific from surface and satellite measurements. Journal of Geophysical Research-Atmospheres. 105:14807-14821.   10.1029/2000jd900109   AbstractWebsite

The heating of the ocean surface by longwave radiation from convective clouds has been estimated using measurements from the Central Equatorial Pacific Experiment (CEPEX). The ratio of the surface longwave cloud forcing to the cloud radiative forcing on the total atmospheric column is parameterized by the f factor. The f factor is a measure of the partitioning of the cloud radiative effect between the surface and the troposphere. Estimates of the f factor have been obtained by combining simultaneous observations from ship, aircraft, and satellite instruments. The cloud forcing near the ocean surface is determined from radiometers on board the National Oceanic and Atmospheric Administration P-3 aircraft and the R/V John Vickers. The longwave cloud forcing at the top of the atmosphere has been estimated from data obtained from the Japanese Geostationary Meteorological Satellite GMS 4. A new method for estimating longwave fluxes from satellite narrowband radiances is described. The method is based upon calibrating the satellite radiances against narrowband and broadband infrared measurements from the high-altitude NASA ER-2 aircraft. The average value of f derived from the surface and satellite observations of convective clouds is 0.15 +/- 0.02. The area-mean top-of-atmosphere longwave forcing by convective clouds in the region 10 degrees S-10 degrees N, 160 degrees E-160 degrees W is 40 W/m(2) during CEPEX. Those results indicate that the surface longwave forcing by convective clouds was approximately 5 W/m(2) in the central equatorial Pacific and that this forcing is the smallest radiative component of the surface energy budget.

Tytler, D, O'Meara JM, Suzuki N, Lubin D.  2000.  Deuterium and the baryonic density of the universe. Physics Reports-Review Section of Physics Letters. 333:409-432.   10.1016/s0370-1573(00)00032-6   AbstractWebsite

Big bang nucleosynthesis (BBN) is the creation of the light nuclei, deuterium, He-3, He-4 and Li-7 during the first few minutes of the universe. Here we discuss recent measurements of the D to H abundance ratio, D/H, in our galaxy and towards quasars. 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 to 1996, it appeared that there could be a factor of 10 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 are 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, eta, 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. (C) 2000 Elsevier Science B.V. All rights reserved.