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The lack of in situ data has always posed challenges to remote-sensing-data product validation. Herein, the products of sea-ice concentration (SIC) data derived using the arctic radiation and turbulence interaction study (ARTIST) sea ice (ASI) algorithm were evaluated by comparing them with SICs from a high-resolution sea-ice aerial image obtained during the 27th China Antarctic expedition in January 2011. Results suggest that data obtained from the advanced microwave scanning radiometer for the earth-observing system (AMSR-E) underestimate SICs by 19%. We performed step-by-step comparisons among the aerial image, moderate-resolution-imaging spectroradiometer (MODIS), and AMSR-E SIC. These types of comparisons have not been made in previous validation studies. First, SICs acquired from MODIS-Terra imagery were acquired using a tie-point method and corrected by SICs derived from the aerial photography. Second, SICs of MODIS-Aqua images were trained based on the consistency of SIC results between MODIS-Terra and MODIS-Aqua over the selected region on the same day. Finally, the MODIS-Aqua SICs were employed to validate synchronous AMSR-E swath SIC products. The results show that the AMSR-E products underestimate SICs by 8.5% in the marginal ice zone in comparison with MODIS SICs. According to our further analysis between sea-ice types and AMSR-E biases, the higher the proportion of first-year ice, the smaller the AMSR-E SIC bias. In other words, results suggest that the higher the thin ice proportion, the more the AMSR-E underestimates the SIC. [ABSTRACT FROM AUTHOR]

In consideration of the Antarctic special environment, a new sea-ice extraction method of u-sing the 0.86 µm. and 1.24 µm wave bands of MODIS is proposed, based on the Normalize Difference Snow Index (NDSI). It can extract the sea ice under the clear sky and thin cloud condition respectively, which largely improve the efficiency and spatial resolution of Antarctic sea-ice monitoring. The new method is used to obtain the monthly sea ice images in the whole Antarctica of recent years. Then, combining the AMSR-E data, the change monitoring of Antarctic sea ice is executed. It indicates that, from 2002 to 2010, both the Antarctic sea-ice extent and sea-ice area reach the minimums in February, with the averages are 3.17 x 106 km² and 2.42 x 106 km² respectively. And the maxi-mums appear in September, with the averages are 18.440 x 106 km² and 16. 60 x 106 km². The inter annual change of Antarctic sea ice can be divided to three periods: the flat period of the year from 2002 to 2004, the reduced period of 2005 to 2007, and the increased period of 2008 to 2010. It verifies the 20 years cycle of Antarctic sea ice in the inter annual change. The change trend of the whole Antarctic sea ice is not obvious in the recent nine years [ABSTRACT FROM AUTHOR]

Abstract: Comparison of surface velocities measured during the Ross Ice Shelf Geophysical and Glaciological Survey (RIGGS, 1973 to 1978) and velocities measured via feature tracking between two Moderate-resolution Imaging Spectroradiometer (MODIS) mosaics (compiled from 2003/4 and 2008/9 images) reveals widespread slowing and minor areas of acceleration in the Ross Ice Shelf (RIS) over the approximately 30 year interval. The largest changes ( ) occur near the Whillans and Mercer Ice Streams grounding line in the southernmost part of the ice shelf. Speed has increased over the interval (up to ) between the MacAyeal Ice Stream grounding line and the shelf front, and along the eastern shelf front. Changes in ice thickness computed using ICESat laser altimetry are used together with a well-tested model of the ice shelf to investigate underlying causes of change in the flow of the ice shelf over time. The observed transients represent a combination of recent forcings and ongoing response to ice stream discharge variations over the past millennium. While evidence of older events may be present, the modern signal is dominated by shorter time scale events, including the stagnation of Kamb Ice Stream about 160 years ago, recent changes in basal drag on the Whillans Ice Stream ice plain and, perhaps, iceberg calving. Details in embayment geometry, for example the shallow sea floor below Crary Ice Rise, modulate the spatial pattern of ice shelf response to boundary condition perturbations. [Copyright &y& Elsevier]

We have examined the development of the Terra Nova Bay polynya (TNBP) using a two-month sequence of Moderate Resolution Imaging Spectroradiometer (MODIS) ice surface temperature (IST) images, complemented by a set of synthetic aperture radar (SAR) images. Results of a comparison between the clear-sky ISTs and the contemporaneous SAR images revealed that the polynya is characterized in the ISTs by a warm core and in the SARs by a bright backscattering area, due to the presence of seawater and grease ice. The activity of the polynya during the period was highly dynamic, with opening and closing phases that had similar temporal length scales, sometimes of less than 24 h. The recent activity of the polynya is evidenced in the SARs by alternate bright and dark backscatter bands formed during openings and calm periods and transported offshore by the ice drift. The thermal fronts that separate the warm core of the polynya from the surrounding ice sheet appeared sharp during the opening phase and smooth during the closing phase. The spatial resolution of 1 km of MODIS ISTs, compared with space-borne passive microwave systems with maximum resolution of approximately 10 km, provides a smaller area for the TNBP than do passive microwave data. The polynya area was detectable up to 80% of time with a revisit time of a few hours, giving an average area of ∼1300 km2 and peaks up to 3000 km2. The polynya is forced by katabatic winds that have a warm signature, which is also visible in the IST sequence. Katabatic airflows descending from the Reeves Glacier valley contribute to the opening of the polynya in the central part of the bay, while airflows descending from the surrounding glacier valleys contribute to the opening in the north and south of the bay. [ABSTRACT FROM AUTHOR]

The article discusses a research study on the unconformable and complex englacial stratigraphy in the Byrd Glacier in East Antarctica with crystallized layers and englacial cosets. Researchers used a Global Positioning Radar (GPR) and a deep-sounding system to record 14-bit samples per trace for profiles display in grayscale amplitude format. Also used were differential kinematic global positioning system (GPS) and satellite imagery with Moderate Resolution Imaging Spectroradiometer (MODIS). Results showed images of 5-15 kilometers long cosets from 400-800 meters deep and modified layers as well as unresolved englacial cosets and firn-englacial transition. It also notes the interpretation of parallel folding as indicator of possible stick-slip or basal slip behavior.

The article presents a study which investigates the impact of cloud over snow and ice on the absorption of ozone in Antarctica. The study made use of Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) cloud top pressure and Aura Ozone Monitoring Instrument (OMI) effective scene pressure to find non-shielding and shielding clouds. The result of the study shows that shielding clouds are seen on clouds optical thickness while non-shielding clouds are seen in lower cloud optical thickness.

A case study illustrating cloud processes and other features associated with the Ross Ice Shelf airstream (RAS), in Antarctica, is presented. The RAS is a semipermanent low-level wind regime primarily over the western Ross Ice Shelf, linked to the midlatitude circulation and formed from terrain-induced and large-scale forcing effects. An integrated approach utilizes Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery, automatic weather station (AWS) data, and Antarctic Mesoscale Prediction System (AMPS) forecast output to study the synoptic-scale and mesoscale phenomena involved in cloud formation over the Ross Ice Shelf during a RAS event. A synoptic-scale cyclone offshore of Marie Byrd Land draws moisture across West Antarctica to the southern base of the Ross Ice Shelf. Vertical lifting associated with flow around the Queen Maud Mountains leads to cloud formation that extends across the Ross Ice Shelf to the north. The low-level cloud has a warm signature in thermal infrared imagery, resembling a surface feature of turbulent katabatic flow typically ascribed to the RAS. Strategically placed AWS sites allow assessment of model performance within and outside of the RAS signature. AMPS provides realistic simulation of conditions aloft but experiences problems at low levels due to issues with the model PBL physics. Key meteorological features of this case study, within the context of previous studies on longer time scales, are inferred to be common occurrences. The assumption that warm thermal infrared signatures are surface features is found to be too restrictive. [ABSTRACT FROM AUTHOR]

The Antarctic ozone hole appears in the Antarctic spring, just after the polar night period when sunlight is not available on the surface. Because it is not possible to have a large solar elevation angle in the Antarctic winter and spring, it is hard to make observations of total ozone amounts with TOMS or Dobson spectrophotometers using sunlight. Because of this there is not enough information about the total ozone amounts over the Antarctic just before and after the seasonal appearance of the Antarctic ozone hole. We have made an analysis of the total ozone amounts with a Dobson spectrophotometer, using moonlight as well as sunlight at the three Antarctic stations and Macquarie Island. The results derived from the analysis are as follows: (1) The decrease of the total ozone amounts leading to the Antarctic ozone hole started at the beginning of August at around 69° south and then took place at the higher latitudes later in the period from 1993 to 2005: (2) The total ozone amounts at the higher latitudes in the Antarctic show the smaller value as a latitudinal gradient of about 1.6 DU per degree in the period from 1993 to 2005. The author hopes that these results will be useful for better understanding of the Antarctic ozone hole. [ABSTRACT FROM AUTHOR]

Extensive observations of total column ozone (TCO) made over the Antarctic region at the Indian station 'Maitri' (70.76oS, 11.74oE) during two summer periods of 2004-2005 and 2006-2007 using a ground-based optical remote sensing instrument (ozonometer) have been examined to study the short-term variations. Mean TCO during 2004-05 summer was 288.7 DU with a variability of 8% and the corresponding values during 2006-2007 summer were 280.4 DU and 11%. Both ozonometer and Dobson spectrophotometer measurements at this Antarctic station during January 2005 showed a short-term decrease in TCO by about 70 DU before regaining original value. Simultaneous changes in precipitable water and surface temperature points to a possible interplay of chemistry and meteorological conditions. Occurrence of an intense solar proton event in January 2005 also suggests the possible role of precipitating charged particles in causing short-lived ozone decrease through production of OH radical. [ABSTRACT FROM AUTHOR]

Total ozone content derived from version 8 of the Earth Probe Total Ozone Mapping Spectrometer (EP-TOMS) satellite data was compared with that from ground-based data obtained with the Dobson spectrophotometer no. 031 at the Ukrainian Antarctic Vernadsky station. The period of comparison is 1996-2005. The statistics for cloudy and clear sky observations are presented separately, in order to assess the influence of cloudiness on the difference between the satellite and ground-based measurements. The main findings obtained from the TOMS-Dobson difference analysis were: (i) a significant disagreement between clear and cloudy sky differences of about 9%, which is almost the same value as in version 7; and (ii) the difference for all data equals -2.0% (2625 days), whereas in cloudless and cloudy conditions the difference is 4.1% (137 days) and -4.5% (1048 days), respectively. We conclude that the TOMS (Dobson) measurements are mostly responsible for the data disagreement in clear (cloudy) sky conditions. [ABSTRACT FROM AUTHOR]

Deals with the effects of solar radiation over long periods of time on both natural phytoplankton assemblages and on monospecific phytoplankton cultures isolated from Arthur Harbor, Antarctica. Spectroradiometer used to monitor solar radiation; Water samples taken from the harbor; Treatments performed on the cultures.