The Diurnal Hysteresis of Snow Albedo

McGuffie, K.; Henderson‐Sellers, A.

doi:10.1017/s0022143000006456

Cited by 26 publications

(19 citation statements)

References 9 publications

(6 reference statements)

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“…Meanwhile, the air temperature is close to zero in the daytime and drops below −8°C in the early morning in clear skies; surface hoar crystals form at “night” and early morning, and then sublimate because of warming in the afternoon. This cycle happens every day and could partially explain the diurnal asymmetry of snow albedo variation [ McGuffie and Henderson ‐ Sellers , 1985; Pirazzini , 2004; Domine et al , 2009]. In contrast, at the seasonal time scale, the near symmetric distribution of the seasonal snow albedo is likely related to the symmetric distribution of SZAs and other SZA/time‐related factors (Figure 3d).…”

Section: Resultsmentioning

confidence: 99%

Arctic and Antarctic diurnal and seasonal variations of snow albedo from multiyear Baseline Surface Radiation Network measurements

Wang¹,

Zender²

2011

J. Geophys. Res.

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[1] This study analyzes diurnal and seasonal variations of snow albedo at four Baseline Surface Radiation Network stations in the Arctic and Antarctica from 2003 to 2008 to elucidate similarities and differences in snow albedo diurnal cycles across geographic zones and to assess how diurnal changes in snow albedo affect the surface energy budget. At the seasonal scale, the daily albedo for the perennial snow at stations South Pole and Georg von Neumayer in Antarctica has a similar symmetric variation with solar zenith angle (SZA) around the austral summer; whereas the daily albedo for the seasonal snow at stations Barrow, Alaska, and Ny-Ålesund, Spitsbergen, in the Arctic tends to decrease with SZA decrease from winter to spring before snow starts melting. At the hourly scale, each station shows unique diurnal cycles due to different processes that affect snow albedo such as cloud cover, snow metamorphism, surface hoar formation, SZA, solar azimuth angle, and surface features. Cloud escalates the snow albedo at all four stations by shifting solar radiation to visible wavelengths and diminishes the diurnal variation by diffusing incident solar radiation. The 24 h mean snow albedo is higher on cloudy than clear days by 0.02 at the South Pole (December) and Barrow (May), 0.05 at Neumayer (December), and 0.07 at Ny-Ålesund (April). Snow surface structures, for example, wind-channeled sastrugi, appear to be a controlling factor in the diurnal variation of clear-sky snow albedo at the South Pole and Ny-Ålesund. The surface hoar formation cycles and snow metamorphism are consistent with the asymmetric diurnal variation of snow albedo at Neumayer and Barrow. Near the melting point temperature, melt-freeze cycles exceed cloud and surface structure impacts and dominate the diurnal variation of snow albedo at stations Barrow and Ny-Ålesund. The satellite-measured clear-sky snow albedo usually underestimates the average all-sky snow albedo at these stations. These results illustrate the potential biases in daily and monthly albedo products constructed from sun-synchronous satellite daily instantaneous observations which inevitably undersample the diurnal variation of snow albedo.Citation: Wang, X., and C. S. Zender (2011), Arctic and Antarctic diurnal and seasonal variations of snow albedo from multiyear Baseline Surface Radiation Network measurements,

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Section: Resultsmentioning

confidence: 99%

Arctic and Antarctic diurnal and seasonal variations of snow albedo from multiyear Baseline Surface Radiation Network measurements

Wang¹,

Zender²

2011

J. Geophys. Res.

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“…In the Antarctic conditions, their observation for the diurnal decline was later in the afternoon. Earlier, a minimum albedo has been detected by McGuffie and Henderson-Sellers (1985) in Canada, too. They suggested the albedo decrease to be due to snow grain metamorphosis caused by heating of the surface.…”

Section: Diurnal Variations In the Albedomentioning

confidence: 92%

“…Also, McGuffie and Henderson-Sellers (1985) have reported of diurnal hysteresis of snow albedo, i.e. that the albedo is different for the same solar elevation angle at different times of day.…”

Section: Asymmetric Albedomentioning

confidence: 99%

Diurnal variations in the UV albedo of arctic snow

et al. 2008

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Abstract. The relevance of snow for climate studies is based on its physical properties, such as high surface reflectivity. Surface ultraviolet (UV) albedo is an essential parameter for various applications based on radiative transfer modeling. Here, new continuous measurements of the local UV albedo of natural Arctic snow were made at Sodankylä (67 • 22 N, 26 • 39 E, 179 m a.s.l.) during the spring of 2007. The data were logged at 1-min intervals. The accumulation of snow was up to 68 cm. The surface layer thickness varied from 0.5 to 35 cm with the snow grain size between 0.2 and 2.5 mm. The midday erythemally weighted UV albedo ranged from 0.6 to 0.8 in the accumulation period, and from 0.5 to 0.7 during melting. During the snow melt period, under cases of an almost clear sky and variable cloudiness, an unexpected diurnal decrease of 0.05 in albedo soon after midday, and recovery thereafter, was detected. This diurnal decrease in albedo was found to be asymmetric with respect to solar midday, thus indicating a change in the properties of the snow. Independent UV albedo results with two different types of instruments confirm these findings. The measured temperature of the snow surface was below 0 • C on the following mornings. Hence, the reversible diurnal change, evident for ∼1-2 h, could be explained by the daily metamorphosis of the surface of the snowpack, in which the temperature of the surface increases, melting some of the snow to liquid water, after which the surface freezes again.

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“…Two effects besides cloud conditions and instrumental errors might have contributed to a change in albedo: (1) the varying contribution of specular reflection from the snow surface with solar angle and (2) the metamorphism (recrystallization on the surface and within the snow pack). Regarding (l), the snow albedo increases as the solar elevation decreases because the first scattering event happens closer to the surface at low sun angles than at larger ones (Dirmhirn & -Sellers 1985). Thus, the chance for an summer time) at the measuring site on 9 June.…”

Section: Satellite-derived Surface Albedo Of Austre Br@ggerbreen and mentioning

confidence: 99%

Landsat TM derived and in situ summer reflectance of glaciers in Svalbard

Winther¹

1993

Polar Research

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Winther, J-G. 1993: Landsat TM derived and in situ summer reflectance of glaciers in Svalbard. Polar Research 12(1), 37-55.The paper presents satellite-derived and in situ reflectance from the Austre Br~ggerbreen and Midre LovCnbreen glaciers located 78"50", 1 l"50'E in the Svalbard archipelago. The satellite data are Landsat-5 TM images recorded on 7 August 1987 and 31 August 1988. In situ measurements of shortwave and spectral reflectance of snow, glacier ice and moraine were carried out in August 1991 and in June 1992. In 1987, Austre Br~ggerbreen had a positive net mass balance of +0.22 m of water equivalent while the net mass balance in 1988 was negative (-0.52 m). This is reflected in the atmospherically corrected satellitederived albedo which shows that the reflective characteristics of the ablation and accumulation zones are more uniform and better separated in 1987 than in 1988. Besides the long-term year to year variations of surface albedo, the glaciers show a considerable short-term as well as spatial variability in reflectance. For example, the satellite-derived TM Band 4 albedo was found to vary between 0.19 and 0.65 at Midre Lovtnbreen on 31 August 1988. In silu measurements show a drop in daily mean albedo from 0.88 to 0.13 during 4 days at a fixed location on Austre Br~ggerbreen in August 1991 (300 m.a.s.1.). Furthermore, spectral measurements of snow albedo in June 1992 clearly demonstrate that the near-infra-red albedo decreases when the snow metamorphoses, i.e. when the characteristic grain size increases. The effect of cloud cover on the snow albedo is also discussed. The integrated albedo (37CL900 nm) increased from 0.812 to 0.869 (7%) when the weather condition changed from clear sky to 100% overcast within 2 hours on 9 June 1992. The bidirectional reflectance of snow is measured by taking spectral scans for viewing angles 0" (nadir), 15". 30". 45" and 60" for viewing directions facing the sun and at azimuths 90" and 180" away from the sun. The increase in albedo relative to the nadir albedo is found to be 8, 15, 19 and 26% for viewing angles 15". 30". 45" and 60". respectively. The largest anisotropy is seen for metamorphosed snow in measurements facing the sun. Consequently, it may be necessary to correct for the specular properties of snow if satellite-derived surface reflectance is going to be considered in terms of absolute values. Hydrotechnical Laboratory, N-7034 Trondheim, Norway. Jan-Gunnar Winther, SINTEF Norwegian

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The Diurnal Hysteresis of Snow Albedo

Cited by 26 publications

References 9 publications

Arctic and Antarctic diurnal and seasonal variations of snow albedo from multiyear Baseline Surface Radiation Network measurements

Arctic and Antarctic diurnal and seasonal variations of snow albedo from multiyear Baseline Surface Radiation Network measurements

Diurnal variations in the UV albedo of arctic snow

Landsat TM derived and in situ summer reflectance of glaciers in Svalbard

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