Parameterization of global and longwave incoming radiation for the Greenland Ice Sheet

Konzelmann, Thomas; Wal, R. S. W. van de; Greuell, Wouter; Bintanja, Richard; Henneken, Edwin A.; Abe‐Ouchi, Ayako

doi:10.1016/0921-8181(94)90013-2

Cited by 226 publications

(287 citation statements)

References 18 publications

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“…At the higher elevations, the ice is covered by snow for a greater proportion of the year, which is more likely to reduce algal growth. However, global radiation strongly increases with altitude on the Greenland ice sheet, because of decreasing cloudiness and a more transparent atmosphere (Konzelmann et al, 1994). This effect might be an important factor for the biological activity.…”

Section: Discussionmentioning

confidence: 99%

Dust from the dark region in the western ablation zone of the Greenland ice sheet

et al. 2011

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Abstract.A dark region tens of kilometres wide is located in the western ablation zone of the Greenland ice sheet. The dark appearance is caused by higher amounts of dust relative to the brighter surroundings. This dust has either been deposited recently or was brought to the surface by melting of outcropping ice. Because the resulting lower albedos may have a significant effect on melt rates, we analysed surface dust on the ice, also called cryoconite, from locations in the dark region as well as locations from the brighter surrounding reference ice with microscopic and geochemical techniques to unravel its composition and origin. We find that (part of) the material is derived from the outcropping ice, and that there is little difference between dust from the dark region and from the reference ice. The dust from the dark region seems enriched in trace and minor elements that are mainly present in the current atmosphere because of anthropogenic activity. This enrichment is probably caused by higher precipitation and lower melt rates in the dark region relative to the ice marginal zone. The rare earth elemental ratios of the investigated material are approximately the same for all sites and resemble Earth's average crust composition. Therefore, the cryoconite probably does not contain volcanic material. The mineralogical composition of the dust excludes Asian deserts, which are often found as provenance for glacial dust in ice cores, as source regions. Consequently, the outcropping dust likely has a more local origin. Finally, we find cyanobacteria and algae in the cryoconite. Total Organic Carbon accounts for up to 5 weight per cent Correspondence to: I. G. M. Wientjes (i.g.m.wientjes@uu.nl) of the cryoconite from the dark region, whereas dust samples from the reference ice contain only 1 % or less. This organic material is likely formed in situ. Because of their high light absorbency, cyanobacteria and the organic material they produce contribute significantly to the low albedo of the dark region.

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Section: Discussionmentioning

confidence: 99%

Dust from the dark region in the western ablation zone of the Greenland ice sheet

et al. 2011

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“…9. In the interior parts of the Greenland and Antarctica ice sheets; however, typical clouds are optically thin (τ c < 1) (Konzelmann et al, 1994;Mahesh et al, 2001), and therefore cloud-free conditions are assumed for these regions. This is seen in Fig.…”

Section: Quality Controlmentioning

confidence: 99%

Operational surface UV radiation product from GOME-2 and AVHRR/3 data

Kujanpää

Kalakoski

2015

Atmos. Meas. Tech.

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“…When characterizing the effect of clouds on the surface shortwave radiation budget, it is important to describe the clouds with a quantity that is not dependent on the radiation field itself. In several previous studies (Konzelmann et al, 1994;Bintanja and van den Broeke, 1996), cloud transmission, as defined in Equation (1), has been used to characterize the optical properties of the cloud. But, as pointed out by, e.g.…”

Section: Cloud Optical Thickness (τ )mentioning

confidence: 99%

“…Long and Ackerman (2000) present a method to estimate cloud fraction (N ) using global and diffuse solar radiation measurements, which limits the application to daytime periods, and to locations where diffuse shortwave radiation is measured. Marty and Philipona (2000) present the Clear-Sky Index to separate clear and cloudy skies using longwave radiation measurements, the derivation of which is based, to a large extent, on Konzelmann et al (1994). Dürr and Philipona (2004) extend the Clear-Sky Index to an algorithm that retrieves N from downwelling longwave measurements.…”

Section: Introductionmentioning

confidence: 99%

Assessing the retrieval of cloud properties from radiation measurements over snow and ice

Munneke

Reijmer

Broeke

2011

Intl Journal of Climatology

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ABSTRACT:We critically review and improve a simple method to extract year-round records of cloud optical thickness from radiation measurements made by automatic weather stations (AWSs) over snow and ice surfaces. A 'longwaveequivalent cloudiness', N ε , obtained from longwave radiation measurements, is combined with the effective cloud optical thickness, τ , from shortwave data, to obtain consistent, year-round information on cloud properties. The method is applied to radiation data from six AWSs in Dronning Maud Land, Antarctica, and the ablation area of the West-Greenland ice sheet. The good correlation between daily-mean N ε and τ for all locations (0.77 < r < 0.94) shows that shortwave radiative properties of clouds can be inferred using longwave radiation even in the absence of solar radiation itself. An error analysis shows that retrievals of τ are sensitive to the quality of the input data, but accurate to about 21% for hourly values, 11% for daily means, and about 6% for monthly means. As three applications of the method presented above, we discuss the influence of clouds on the radiation budget (Application I), the relation between cloud cover and broadband albedo (Application II) at the six AWS locations, and we demonstrate the possibility to detect trends in τ in longer data series (Application III). About one-third of the attenuation of solar radiation by clouds is compensated by multiple reflections between the high-albedo surface and the cloud base (Application I). Cloudy-sky surface albedo is higher than the clear-sky albedo for snow surfaces but not for ice (Application II): over snow surfaces, clouds deplete near-infrared (IR) radiation and thus increase the broadband albedo. Ice surfaces have a much lower albedo for visible radiation, weakening this enrichment of visible radiation and thus the increase of broadband albedo. The method is used to detect a trend in τ of −0.40 ± 0.15 y −1 in the 1995-2004 time series from Neumayer, Antarctica (Application III).

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Parameterization of global and longwave incoming radiation for the Greenland Ice Sheet

Cited by 226 publications

References 18 publications

Dust from the dark region in the western ablation zone of the Greenland ice sheet

Dust from the dark region in the western ablation zone of the Greenland ice sheet

Operational surface UV radiation product from GOME-2 and AVHRR/3 data

Assessing the retrieval of cloud properties from radiation measurements over snow and ice

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