Springtime microwave emissivity changes in the southern Kara Sea

Crane, Robert G.; Anderson, Mark R.

doi:10.1029/94jc00381

Cited by 14 publications

(9 citation statements)

References 26 publications

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“…Anderson and Drobot [18] have shown that the MO dates in one region of the Arctic are largely independent of the MO dates in other regions. This is most likely due to the regional nature of cyclonic activity and the associated warm air anomalies [13,19] and increased longwave radiation flux at the surface due to enhanced cloud cover (e.g., [36,37]). Therefore, an extreme MO area accumulation (one that is at either the early or late ends of the 50% MO area range) in a region one year may not appear to be an abnormal year for other regions.…”

Section: Variability In Arctic Ocean Sub-regionsmentioning

confidence: 99%

Daily Area of Snow Melt Onset on Arctic Sea Ice from Passive Microwave Satellite Observations 1979–2012

Bliss

Anderson

2014

Remote Sensing

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Variability in snow melt onset (MO) on Arctic sea ice since 1979 is examined by determining the area of sea ice experiencing the onset of melting during the melt season on a daily basis. The daily MO area of the snow and ice surface is determined from passive microwave satellite-derived MO dates for the Arctic Ocean and sub-regions. Annual accumulations of MO area are determined by summing the time series of daily MO area through the melt season. Daily areas and annual accumulations of MO area highlight inter-annual and regional variability in the timing of MO area, which is sensitive to day-to-day variations in spring weather conditions. Two distinct spatial patterns in MO area accumulations including an intense, fast accumulating melt area pattern and a slow accumulating melt pattern are examined for two melting events in the Kara Sea. In comparing the 34 years of MO dates for the Arctic Ocean and sub-regions, melt accumulations have changed during the period. In the earlier years, 1979-1987, the MO generally was later in the year than the mean, while in more recent years, the MO accumulations have been occurring earlier in the melt season. The sub-regions of the Arctic Ocean also exhibit greater annual variability than the Arctic Ocean.

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Section: Variability In Arctic Ocean Sub-regionsmentioning

confidence: 99%

Daily Area of Snow Melt Onset on Arctic Sea Ice from Passive Microwave Satellite Observations 1979–2012

Bliss

Anderson

2014

Remote Sensing

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“…Atmospheric warming above the surface inversion associated with spring cyclones can initiate MO due to enhanced downwelling longwave radiation from thick cloud cover [8]. Further, precipitation and the evolution of the snow grain sizes under freezing surface conditions can impact the Tb signal [9]. The MO date on DOY 68 is unrealistic given the effect of the 20-day window test in this specific event; however given the uncertainties related to the SIC and atmospheric effects for this marginal, first-year ice location, it is also possible that no melting occurred on the later date (DOY 77) when the lower threshold condition was reached.…”

Section: The Barents Seamentioning

confidence: 99%

“…2017, 9,199 18 of 25 including differences greater than 30 days for the Sea of Okhotsk, Baffin Bay, Bering, Greenland, and Barents Seas (Table 3). In most cases, the minima (earlier MO) and maxima (later MO) of the time series are in-phase, although the relative magnitude of the peaks can differ (Figure 7).…”

Section: Original Ahra and Pmwc Trend Comparisonmentioning

confidence: 99%

“…The spring transition period is known to be important for the annual surface energy budget of the Arctic. Modest reductions in surface albedo occur when melting begins [8] and liquid water develops between snow grains [9], thus contributing to increased absorption of solar radiation that enhances the ice-albedo feedback mechanism [10]. When coupled with increasing daylight hours in the spring, the timing of melt onset (MO) on Arctic sea ice can have a propagating effect through the remainder of the melt season [7].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Passive Microwave-Derived Early Melt Onset Records on Arctic Sea Ice

2017

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Two long records of melt onset (MO) on Arctic sea ice from passive microwave brightness temperatures (Tbs) obtained by a series of satellite-borne instruments are compared. The Passive Microwave (PMW) method and Advanced Horizontal Range Algorithm (AHRA) detect the increase in emissivity that occurs when liquid water develops around snow grains at the onset of early melting on sea ice. The timing of MO on Arctic sea ice influences the amount of solar radiation absorbed by the ice-ocean system throughout the melt season by reducing surface albedos in the early spring. This work presents a thorough comparison of these two methods for the time series of MO dates from 1979 through 2012. The methods are first compared using the published data as a baseline comparison of the publically available data products. A second comparison is performed on adjusted MO dates we produced to remove known differences in inter-sensor calibration of Tbs and masking techniques used to develop the original MO date products. These adjustments result in a more consistent set of input Tbs for the algorithms. Tests of significance indicate that the trends in the time series of annual mean MO dates for the PMW and AHRA are statistically different for the majority of the Arctic Ocean including the Laptev, E. Siberian, Chukchi, Beaufort, and central Arctic regions with mean differences as large as 38.3 days in the Barents Sea. Trend agreement improves for our more consistent MO dates for nearly all regions. Mean differences remain large, primarily due to differing sensitivity of in-algorithm thresholds and larger uncertainties in thin-ice regions.

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“…Sea ice also affects the temperature-albedo feedback (Lutgens and Tarbuck 2001). The albedo varies from 40% to 80% for sea ice, and is about 10% for open water (Crane and Anderson 1994). Also, sea ice emissivity, defined as the ratio of the radiant flux from the material to that of a blackbody at the same physical temperature (Comiso 1983), can give insight into the following factors; ice types, composition, edge, age, thickness, surface characteristics, incidence angle, snow cover, frequency, polarization, ocean currents, weather, and etc.…”

Section: Introductionmentioning

confidence: 99%

Surface Emissivity and Hydrometeors Derived from Microwave Satellite Observations and Model Reanalyses

Yoo¹,

Prabhakara

Iacovazzi

2003

Journal of the Meteorological Society of Japan

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Satellite-observed Microwave Sounding Unit (MSU) channel 1 (Ch1) brightness temperature, and General Circulation Model (GCM) reanalyses over the globe, as well as radiative transfer simulations, have been used to investigate microwave surface emissivity, and low-tropospheric hydrometeors, during the period from January 1981 to December 1993. The average model Ch1 temperature has been derived from three kinds of GCM reanalyses, based on the MSU weighting function. Since the Ch1 temperature constructed from GCM-reanalysis air temperature neglects effects from surface emissivity differences and hydrometeors, it is highest in the summer hemisphere. On the other hand, MSU temperature over land is much higher than it is over ocean, due to depressed surface emissivity over water. Over the high latitude ocean the MSU Ch1 temperature is enhanced because of ice/snow emissivity, while it is reduced over the high latitude land.The difference values of Ch1 temperature between reanalysis and MSU decrease, in the regions of the ITCZ, SPCZ and sea ice mainly because of increased MSU temperature. The values decrease by about 4-6 K in the ITCZ and SPCZ regions, due to hydrometeors. This difference is found to decrease by about 10-30 K in sea ice regions, due to change in surface emissivity. To explain these results, we have estimated the contribution of surface emissivity and hydrometeors to the MSU Ch1 temperature, utilizing radiative transfer theory. The increase of 4-6 K in the temperature over the ITCZ and SPCZ is estimated to result from hydrometeors that give a precipitation rate of 1-1.5 mm/day under the horizontal homogeneity of rain within the MSU radiometer field of view (fov, @110 km), and 7-11 mm/day under inhomogeneous rain distribution within the fov, consistent with TRMM observations. The increase of 10-30 K over the high latitude ocean, arises from ice emissivity of 0.6-0.9. Seasonal movements of sea ice boundary also have been discussed. This study could be valuable by providing an independent technique of computing surface emissivity and hydrometeors over the globe, and for long time periods from microwave measurements, such as MSU and AMSU.

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Springtime microwave emissivity changes in the southern Kara Sea

Cited by 14 publications

References 26 publications

Daily Area of Snow Melt Onset on Arctic Sea Ice from Passive Microwave Satellite Observations 1979–2012

Daily Area of Snow Melt Onset on Arctic Sea Ice from Passive Microwave Satellite Observations 1979–2012

Comparison of Passive Microwave-Derived Early Melt Onset Records on Arctic Sea Ice

Surface Emissivity and Hydrometeors Derived from Microwave Satellite Observations and Model Reanalyses

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