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Lubin, D, Simpson AS.  1997.  Measurement of surface radiation fluxes and cloud optical properties during the 1994 Arctic Ocean Section. Journal of Geophysical Research-Atmospheres. 102:4275-4286.   10.1029/96jd03215   AbstractWebsite

During a voyage to the north pole from Alaska by the icebreakers USCGC Polar Sea and Canadian CGC Louis S. St.-Laurent (the 1994 Arctic Ocean Section, July 24 to September 3) an atmospheric radiation and remote sensing experiment measured downwelling shortwave and longwave radiation reaching the sea ice surface. The experiment included a Fourier transform infrared (FTIR) spectroradiometer which measured zenith radiance at 1 cm(-1) resolution in the middle infrared wavelength range 5-20 mu m, an Eppley pyranometer measuring most of the downwelling shortwave flux (0.28-2.80 mu m), an Eppley pyranometer measuring the downwelling near-infrared flux (0.78-2.80 mu m), and an Eppley pyrgeometer measuring the downwelling longwave flux. In conjunction with a discrete-ordinates radiative transfer model, the FTIR emission spectra are used to estimate 8-12 mu m cloud emissivity and effective radius of the cloud droplet size distribution. The broadband shortwave flux measurements are used to estimate shortwave cloud scattering optical depth. Most of the FTIR emission spectra recorded under overcast skies are consistent with cloud effective radius in the range 10-12 mu m, but 27% of the spectra are more consistent with the range 4-6 mu m, suggesting an occasional continental aerosol influence to Arctic cloud microphysics. The average daily shortwave cloud-scattering optical depth ranged from 2 to 46, which is similar to a range inferred from radiometer data recorded at Barrow, Alaska, during the same season. The downwelling shortwave flux measurements and estimates of net surface flux are generally consistent with a four-decade Russian climatology but also suggest that the frequency of cloud cover sampled during the 1994 Arctic Ocean Section was somewhat larger than the climatological average. These radiation measurement data from the 1994 Arctic Ocean Section should be useful for examining the treatment of atmospheric radiation and surface energy input in Arctic climate model simulations.

Lubin, D, Frederick JE, Booth CR, Lucas T, Neuschuler D.  1989.  Measurements of Enhanced Springtime Ultraviolet-Radiation at Palmer-Station, Antarctica. Geophysical Research Letters. 16:783-785.   10.1029/GL016i008p00783   AbstractWebsite

Measurements of ultraviolet solar spectra from Palmer Station, Antarctica have defined the surface radiation environment of the region during the Austral spring of 1988. At wavelengths where absorption by ozone is negligible, 335–345 nm, the noontime irradiances show the expected gradual increase from the first day of measurements, 19 September, through 21 December. Large variations related to cloudiness are imposed on this background. At wavelengths less than 310 nm the influence of the 1988 ozone “hole” is apparent. The noontime irradiance observed in the wavelength band 295–305 nm on 19 October, two months prior to summer solstice, exceeded any value measured through 21 December.

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.

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.