On detection of the thermophysical state of landfast first-year sea ice using in-situ microwave emission during spring melt

B Hwang, Alexandre Langlois, David G. Barber, Timothy N. Papakyriakou

Research output: Contribution to journalArticle

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Abstract

In this study we examine the critical linkages between thermophysical properties and microwave emissions of landfast snow-covered first-year sea ice during spring melt. For this we analyzed the temporal evolution of radiation fluxes, electro-thermophysical properties and microwave emissions, and perform model simulations to evaluate the observations. The results show five major microwave signature events: brine-rich, blowing snow, melt onset, the onset of funicular regime, and freezing. A brine-rich snow basal layer can considerably increase the snow wetness in the upper and mid layers, resulting in a significant increase in complex permittivity that in turn increases in polarization difference (δp) at 19 and 37 GHz. A dense (∼ 0.40 g cm- 3) wind-packed snow surface layer, during a blowing snow event, was found to increase the permittivity (i.e., surface reflectivity) that in turn increases δp in microwave emissions. Melt onset caused by sustained warming (above - 5 °C) corresponded to increased δp of ∼ 9 K at 19 GHz. The most dramatic increase in δp (up to 17 K at 19 GHz) coincided with the occurrence of a rainstorm. During a freezing, melt-freeze events enlarged snow grains and led to formation of ice lenses and layers within the snow, thereby significantly decreasing microwave emissions. We found that these five factors state above were critical to the melt indicators (i.e., ΔTB(H) (TB(19H) - TB(37H)) and XPGR ([TB(19H) - TB(37V)]/[TB(19H) + TB(37V)])) commonly used in the satellite melt detection algorithms. The results suggests that the absolute value of TB(19H) (brightness temperature of horizontal polarization at 19 GHz) would be a good indicator along with ΔTB(H) (or XPGR) to delineate the melt onset from ambiguous factors (i.e., a brine-rich slush layer or wind-packed layer), and that the funicular stage of snow melt on sea ice could be unambiguously detected by either ΔTB(H) or XPGR.

Original languageEnglish
Pages (from-to)148-159
Number of pages12
JournalRemote Sensing of Environment
Volume111
Issue number2-3
DOIs
Publication statusPublished - 30 Nov 2007
Externally publishedYes

Fingerprint

Springs (water)
Sea ice
Snow
snow
sea ice
ice
Microwaves
melt
blowing snow
brine
permittivity
Blow molding
freezing
Freezing
polarization
Permittivity
Thermodynamic properties
Polarization
detection
microwave

Cite this

Hwang, B ; Langlois, Alexandre ; Barber, David G. ; Papakyriakou, Timothy N. / On detection of the thermophysical state of landfast first-year sea ice using in-situ microwave emission during spring melt. In: Remote Sensing of Environment. 2007 ; Vol. 111, No. 2-3. pp. 148-159.
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abstract = "In this study we examine the critical linkages between thermophysical properties and microwave emissions of landfast snow-covered first-year sea ice during spring melt. For this we analyzed the temporal evolution of radiation fluxes, electro-thermophysical properties and microwave emissions, and perform model simulations to evaluate the observations. The results show five major microwave signature events: brine-rich, blowing snow, melt onset, the onset of funicular regime, and freezing. A brine-rich snow basal layer can considerably increase the snow wetness in the upper and mid layers, resulting in a significant increase in complex permittivity that in turn increases in polarization difference (δp) at 19 and 37 GHz. A dense (∼ 0.40 g cm- 3) wind-packed snow surface layer, during a blowing snow event, was found to increase the permittivity (i.e., surface reflectivity) that in turn increases δp in microwave emissions. Melt onset caused by sustained warming (above - 5 °C) corresponded to increased δp of ∼ 9 K at 19 GHz. The most dramatic increase in δp (up to 17 K at 19 GHz) coincided with the occurrence of a rainstorm. During a freezing, melt-freeze events enlarged snow grains and led to formation of ice lenses and layers within the snow, thereby significantly decreasing microwave emissions. We found that these five factors state above were critical to the melt indicators (i.e., ΔTB(H) (TB(19H) - TB(37H)) and XPGR ([TB(19H) - TB(37V)]/[TB(19H) + TB(37V)])) commonly used in the satellite melt detection algorithms. The results suggests that the absolute value of TB(19H) (brightness temperature of horizontal polarization at 19 GHz) would be a good indicator along with ΔTB(H) (or XPGR) to delineate the melt onset from ambiguous factors (i.e., a brine-rich slush layer or wind-packed layer), and that the funicular stage of snow melt on sea ice could be unambiguously detected by either ΔTB(H) or XPGR.",
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On detection of the thermophysical state of landfast first-year sea ice using in-situ microwave emission during spring melt. / Hwang, B; Langlois, Alexandre; Barber, David G.; Papakyriakou, Timothy N.

In: Remote Sensing of Environment, Vol. 111, No. 2-3, 30.11.2007, p. 148-159.

Research output: Contribution to journalArticle

TY - JOUR

T1 - On detection of the thermophysical state of landfast first-year sea ice using in-situ microwave emission during spring melt

AU - Hwang, B

AU - Langlois, Alexandre

AU - Barber, David G.

AU - Papakyriakou, Timothy N.

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N2 - In this study we examine the critical linkages between thermophysical properties and microwave emissions of landfast snow-covered first-year sea ice during spring melt. For this we analyzed the temporal evolution of radiation fluxes, electro-thermophysical properties and microwave emissions, and perform model simulations to evaluate the observations. The results show five major microwave signature events: brine-rich, blowing snow, melt onset, the onset of funicular regime, and freezing. A brine-rich snow basal layer can considerably increase the snow wetness in the upper and mid layers, resulting in a significant increase in complex permittivity that in turn increases in polarization difference (δp) at 19 and 37 GHz. A dense (∼ 0.40 g cm- 3) wind-packed snow surface layer, during a blowing snow event, was found to increase the permittivity (i.e., surface reflectivity) that in turn increases δp in microwave emissions. Melt onset caused by sustained warming (above - 5 °C) corresponded to increased δp of ∼ 9 K at 19 GHz. The most dramatic increase in δp (up to 17 K at 19 GHz) coincided with the occurrence of a rainstorm. During a freezing, melt-freeze events enlarged snow grains and led to formation of ice lenses and layers within the snow, thereby significantly decreasing microwave emissions. We found that these five factors state above were critical to the melt indicators (i.e., ΔTB(H) (TB(19H) - TB(37H)) and XPGR ([TB(19H) - TB(37V)]/[TB(19H) + TB(37V)])) commonly used in the satellite melt detection algorithms. The results suggests that the absolute value of TB(19H) (brightness temperature of horizontal polarization at 19 GHz) would be a good indicator along with ΔTB(H) (or XPGR) to delineate the melt onset from ambiguous factors (i.e., a brine-rich slush layer or wind-packed layer), and that the funicular stage of snow melt on sea ice could be unambiguously detected by either ΔTB(H) or XPGR.

AB - In this study we examine the critical linkages between thermophysical properties and microwave emissions of landfast snow-covered first-year sea ice during spring melt. For this we analyzed the temporal evolution of radiation fluxes, electro-thermophysical properties and microwave emissions, and perform model simulations to evaluate the observations. The results show five major microwave signature events: brine-rich, blowing snow, melt onset, the onset of funicular regime, and freezing. A brine-rich snow basal layer can considerably increase the snow wetness in the upper and mid layers, resulting in a significant increase in complex permittivity that in turn increases in polarization difference (δp) at 19 and 37 GHz. A dense (∼ 0.40 g cm- 3) wind-packed snow surface layer, during a blowing snow event, was found to increase the permittivity (i.e., surface reflectivity) that in turn increases δp in microwave emissions. Melt onset caused by sustained warming (above - 5 °C) corresponded to increased δp of ∼ 9 K at 19 GHz. The most dramatic increase in δp (up to 17 K at 19 GHz) coincided with the occurrence of a rainstorm. During a freezing, melt-freeze events enlarged snow grains and led to formation of ice lenses and layers within the snow, thereby significantly decreasing microwave emissions. We found that these five factors state above were critical to the melt indicators (i.e., ΔTB(H) (TB(19H) - TB(37H)) and XPGR ([TB(19H) - TB(37V)]/[TB(19H) + TB(37V)])) commonly used in the satellite melt detection algorithms. The results suggests that the absolute value of TB(19H) (brightness temperature of horizontal polarization at 19 GHz) would be a good indicator along with ΔTB(H) (or XPGR) to delineate the melt onset from ambiguous factors (i.e., a brine-rich slush layer or wind-packed layer), and that the funicular stage of snow melt on sea ice could be unambiguously detected by either ΔTB(H) or XPGR.

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KW - Microwave emission

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KW - Snow

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