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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.

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.

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.

Berque, J, Lubin D, Somerville RCJ.  2004.  Infrared radiative properties of the Antarctic plateau from AVHRR data. Part I: Effect of the snow surface. Journal of Applied Meteorology. 43:350-362.   10.1175/1520-0450(2004)043<0350:irpota>;2   AbstractWebsite

The effective scene temperature, or "brightness temperature," measured in channel 3 (3.5-3.9 m m) of the Advanced Very High Resolution Radiometer (AVHRR) is shown to be sensitive, in principle, to the effective particle size of snow grains on the Antarctic plateau, over the range of snow grain sizes reported in field studies. In conjunction with a discrete ordinate method radiative transfer model that couples the polar atmosphere with a scattering and absorbing snowpack, the thermal infrared channels of the AVHRR instrument can, therefore, be used to estimate effective grain size at the snow surface over Antarctica. This is subject to uncertainties related to the modeled top-of-atmosphere bidirectional reflectance distribution function resulting from the possible presence of sastrugi and to lack of complete knowledge of snow crystal shapes and habits as they influence the scattering phase function. However, when applied to NOAA-11 and NOAA-12 AVHRR data from 1992, the snow grain effective radii of order 50 mum are retrieved, consistent with field observations, with no apparent discontinuity between two spacecraft having different viewing geometries. Retrieved snow grain effective radii are 10-20-mum larger when the snow grains are modeled as hexagonal solid columns rather than as spheres with a Henyey-Greenstein phase function. Despite the above-mentioned uncertainties, the retrievals are consistent enough that one should be able to monitor climatically significant changes in surface snow grain size due to major precipitation events. It is also shown that a realistic representation of the surface snow grain size is critical when retrieving the optical depth and effective particle radius of clouds for the optically thin clouds most frequently encountered over the Antarctic plateau.