Investigations of newly formed sea ice in the Cape Bathurst polynya: 2. Microwave emission

B Hwang, Jens K. Ehn, David G. Barber, Ryan Galley, Thomas C. Grenfell

Research output: Contribution to journalArticle

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Abstract

This study examines the role of newly formed sea ice geophysical state on microwave emission. Coincident with sea ice geophysical sampling, ship-based passive microwave emission data (dual-polarized at 19, 37 and 85 GHz) were collected in the Cape Bathurst Polynya during 18 October and 13 November 2003. Using polarization ratios (PRs), we found that bare thin ice was separable from snow-covered ice. Thin snow (equal to 0.02-0.13 m) thickness is significantly correlated with the spectral gradient ratios GRV(85,19) (R2 = 0.55, P-value <0.05) and GRV(85,37) (R2 = 0.66, P-value < 0.05), but not with GRV(37,19) (R2 = 0.19, P-value > 0.2). The relationship between atmospherically corrected R37 and bare ice thickness showed an exponential relationship very comparable to that reported by Martin et al. [2004], which is ascribed to the reduction of bare ice surface salinity based on both observational and modeling studies. However, the relationship quickly becomes invalid for even thin snow covered ice, due to significant impact of thin wet (liquid water fraction ∼0.02-0.04) snow on microwave emission. Our results suggest that the sea ice algorithms NASA Team and NASA Team 2 could underestimate total ice concentration over thin bare ice by 35% on average, while both algorithms underestimate the total ice concentration by 20% over snow-covered ice. Using PR(85) sea ice could be delineated from open water using a properly adjusted threshold value accounting for cloud or fog effects, possibly with the exception of dark nilas and/or bare consolidated pancakes.
LanguageEnglish
Article numberC05003
Number of pages14
JournalJournal of Geophysical Research: Oceans
Volume112
Issue numberC5
DOIs
Publication statusPublished - 1 May 2007
Externally publishedYes

Fingerprint

microwave emission
polynya
Sea ice
sea ice
Ice
ice
Microwaves
snow
Snow
NASA
polarization
Polarization
microwave
ice thickness
fog
Water
open water
Fog
ships
salinity

Cite this

Hwang, B ; Ehn, Jens K. ; Barber, David G. ; Galley, Ryan ; Grenfell, Thomas C. / Investigations of newly formed sea ice in the Cape Bathurst polynya : 2. Microwave emission. In: Journal of Geophysical Research: Oceans. 2007 ; Vol. 112, No. C5.
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abstract = "This study examines the role of newly formed sea ice geophysical state on microwave emission. Coincident with sea ice geophysical sampling, ship-based passive microwave emission data (dual-polarized at 19, 37 and 85 GHz) were collected in the Cape Bathurst Polynya during 18 October and 13 November 2003. Using polarization ratios (PRs), we found that bare thin ice was separable from snow-covered ice. Thin snow (equal to 0.02-0.13 m) thickness is significantly correlated with the spectral gradient ratios GRV(85,19) (R2 = 0.55, P-value <0.05) and GRV(85,37) (R2 = 0.66, P-value < 0.05), but not with GRV(37,19) (R2 = 0.19, P-value > 0.2). The relationship between atmospherically corrected R37 and bare ice thickness showed an exponential relationship very comparable to that reported by Martin et al. [2004], which is ascribed to the reduction of bare ice surface salinity based on both observational and modeling studies. However, the relationship quickly becomes invalid for even thin snow covered ice, due to significant impact of thin wet (liquid water fraction ∼0.02-0.04) snow on microwave emission. Our results suggest that the sea ice algorithms NASA Team and NASA Team 2 could underestimate total ice concentration over thin bare ice by 35{\%} on average, while both algorithms underestimate the total ice concentration by 20{\%} over snow-covered ice. Using PR(85) sea ice could be delineated from open water using a properly adjusted threshold value accounting for cloud or fog effects, possibly with the exception of dark nilas and/or bare consolidated pancakes.",
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Investigations of newly formed sea ice in the Cape Bathurst polynya : 2. Microwave emission. / Hwang, B; Ehn, Jens K.; Barber, David G.; Galley, Ryan; Grenfell, Thomas C.

In: Journal of Geophysical Research: Oceans, Vol. 112, No. C5, C05003, 01.05.2007.

Research output: Contribution to journalArticle

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AU - Hwang, B

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AU - Barber, David G.

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AU - Grenfell, Thomas C.

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N2 - This study examines the role of newly formed sea ice geophysical state on microwave emission. Coincident with sea ice geophysical sampling, ship-based passive microwave emission data (dual-polarized at 19, 37 and 85 GHz) were collected in the Cape Bathurst Polynya during 18 October and 13 November 2003. Using polarization ratios (PRs), we found that bare thin ice was separable from snow-covered ice. Thin snow (equal to 0.02-0.13 m) thickness is significantly correlated with the spectral gradient ratios GRV(85,19) (R2 = 0.55, P-value <0.05) and GRV(85,37) (R2 = 0.66, P-value < 0.05), but not with GRV(37,19) (R2 = 0.19, P-value > 0.2). The relationship between atmospherically corrected R37 and bare ice thickness showed an exponential relationship very comparable to that reported by Martin et al. [2004], which is ascribed to the reduction of bare ice surface salinity based on both observational and modeling studies. However, the relationship quickly becomes invalid for even thin snow covered ice, due to significant impact of thin wet (liquid water fraction ∼0.02-0.04) snow on microwave emission. Our results suggest that the sea ice algorithms NASA Team and NASA Team 2 could underestimate total ice concentration over thin bare ice by 35% on average, while both algorithms underestimate the total ice concentration by 20% over snow-covered ice. Using PR(85) sea ice could be delineated from open water using a properly adjusted threshold value accounting for cloud or fog effects, possibly with the exception of dark nilas and/or bare consolidated pancakes.

AB - This study examines the role of newly formed sea ice geophysical state on microwave emission. Coincident with sea ice geophysical sampling, ship-based passive microwave emission data (dual-polarized at 19, 37 and 85 GHz) were collected in the Cape Bathurst Polynya during 18 October and 13 November 2003. Using polarization ratios (PRs), we found that bare thin ice was separable from snow-covered ice. Thin snow (equal to 0.02-0.13 m) thickness is significantly correlated with the spectral gradient ratios GRV(85,19) (R2 = 0.55, P-value <0.05) and GRV(85,37) (R2 = 0.66, P-value < 0.05), but not with GRV(37,19) (R2 = 0.19, P-value > 0.2). The relationship between atmospherically corrected R37 and bare ice thickness showed an exponential relationship very comparable to that reported by Martin et al. [2004], which is ascribed to the reduction of bare ice surface salinity based on both observational and modeling studies. However, the relationship quickly becomes invalid for even thin snow covered ice, due to significant impact of thin wet (liquid water fraction ∼0.02-0.04) snow on microwave emission. Our results suggest that the sea ice algorithms NASA Team and NASA Team 2 could underestimate total ice concentration over thin bare ice by 35% on average, while both algorithms underestimate the total ice concentration by 20% over snow-covered ice. Using PR(85) sea ice could be delineated from open water using a properly adjusted threshold value accounting for cloud or fog effects, possibly with the exception of dark nilas and/or bare consolidated pancakes.

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