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Bothale, Rajashree V.
- Spatio-Temporal Dynamics of Surface Melting over Antarctica Using OSCAT and QuikSCAT Scatterometer Data (2001-2014)
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Authors
Affiliations
1 National Remote Sensing Centre (ISRO), Hyderabad 500 037, IN
1 National Remote Sensing Centre (ISRO), Hyderabad 500 037, IN
Source
Current Science, Vol 109, No 4 (2015), Pagination: 733-744Abstract
In this article, spatio-temporal dynamics of snowmelt in Antarctica from 2001 to 2014 using OSCAT and QuikSCAT scatterometer data is presented. Melting over Antarctic ice sheet can influence shelf dynamics and stability. Here, we have utilized the sensitivity of scatterometer data to detect the presence of liquid water in the snow caused due to melt conditions. After analysing decadal data, a spatial and temporal variation in the average backscatter coefficient was observed over the shelf areas. An adaptive thresholdbased classification using austral winter mean and standard deviation of HH polarization is used which takes into account the spatial and temporal variability in backscatter from snow/ice. Significant spatiotemporal variability in melt area, duration and melt index was observed. Around 9.5% of the continent experienced melt over the study period. Larsen C and George VI shelves had maximum melt duration. The high correlation between melt duration obtained from satellite data and the positive degree day validates the efficacy of the melt algorithm used in the analysis and sensitivity of OSCAT data in detecting presence of water due to melt. There is seasonal and spatial variation in melt onset. Based on MI, 2004-05 was the warmest summer over the continent with 2011-12 being the coldest summer. Consistent and intensive melting was observed over Amery, Larsen C, George VI, Lazarev and Fimbul shelves. Melting of sporadic nature was observed over Ronne-Filchner, Ross and Riiser-Larsen shelves. The East Antarctic shelves experienced large melt during the study period. This article presents the suitability of OSCAT in melt identification and status of melt over the continent.Keywords
Ice Shelves, Scatterometer Data, Spatiotemporal Dynamics, Snowmelt.Full Text
- Understanding Relationship between Melt/Freeze Conditions Derived from Spaceborne Scatterometer and Field Observations at Larsemann Hills, East Antarctica during Austral Summer 2015-16
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PDF Views:77
Authors
Affiliations
1 National Remote Sensing Centre (ISRO), Hyderabad 500 037, IN
2 Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547, IN
1 National Remote Sensing Centre (ISRO), Hyderabad 500 037, IN
2 Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547, IN
Source
Current Science, Vol 113, No 04 (2017), Pagination: 733-742Abstract
Snow fork and ground penetrating radar at 200 MHz were used for snow depth, wetness and density measurements towards understanding the relationship between melt/freeze conditions derived from spaceborne Advance Scatterometer (ASCAT) and Oceansat-2 Scatterometer (OSCAT), and field observations. The observations were acquired at Larsemann Hills, East Antarctica in austral summer of 2015-16 during the 35th Indian Scientific Expedition to Antarctica. The field observations of wetness correlated well with identified dry and percolation zones showcasing different behaviours of density and wetness. Ice firn was observed at 50-55 cm depth, even in dry zone. Melt onset and number of melt days based on ASCAT varied spatially and temporally over the years and correlated well with positive degree day (PDD) for automatic weather station data located at the Indian Antarctic station, Bharati. Backscatter measurements by OSCAT showed that winter backscatter reduced with accumulation for both dry and percolation zones, but increased in the later part of winter in the percolation zone. A positive but low correlation was observed between ASCAT backscatter to accumulation and the surface mass balance from regional atmospheric climate model (RACMO2.3). A high correlation of 0.78 was observed between reduction in backscatter due to liquid water content and PDD, which coincides with field observations of wetness. The observations serve as baseline to monitor melt conditions and stability of existing ice sheet.Keywords
Ground Penetrating Radar, Ice Firn, Snow-Fork, Scatterometer, Snowpack Characteristics.Full Text
References
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- Assessment of Cryospheric Parameters Over the Himalaya and Antarctic Regions using SCATSAT-1 Enhanced Resolution Data
Abstract Views :245 |
PDF Views:78
Authors
Sandip R. Oza
1,
Rajashree V. Bothale
2,
D. Ram Rajak
1,
P. Jayaprasad
1,
Saroj Maity
1,
Praveen K. Thakur
3,
Naveen Tripathi
1,
Arpit Chouksey
3,
I. M. Bahuguna
1
Affiliations
1 Space Applications Centre, ISRO, Ahmedabad 380 015, IN
2 National Remote Sensing Centre, ISRO, Hyderabad 500 037, IN
3 Indian Institute of Remote Sensing, ISRO, Dehradun 248 001, IN
1 Space Applications Centre, ISRO, Ahmedabad 380 015, IN
2 National Remote Sensing Centre, ISRO, Hyderabad 500 037, IN
3 Indian Institute of Remote Sensing, ISRO, Dehradun 248 001, IN
Source
Current Science, Vol 117, No 6 (2019), Pagination: 1002-1013Abstract
Antarctica is the focus of scientific studies considering the largest reservoir of terrestrial water in the form of ice and doubling of ice area during winter due to sea-ice growth. The third pole – Himalaya is equally important due to the large extent of snow and ice cover outside the polar regions, which is a major source of water for the Asian countries. At present, the Ku-band scatterometer observing global cryosphere is the SCATSAT-1 launched by India. This article describes the study carried out on different cryospheric parameters using high-resolution (~2.2 km) scatterometer data in the Antarctica and Himalaya. Impact of seasonal variations in snow/ice and ice calving on the backscatter over Antarctica is discussed in detail. A procedure developed for the estimation of sea-ice extent, which yielded overall accuracy of 89%, has been presented and successfully applied for daily monitoring of the Antarctic ice extent for 2017. Surface melting using backscatter and brightness temperature data has been discussed and the contrast between large-sized and small-sized Antarctic ice shelves during the austral summer period of summer 2017–18 is highlighted. The higher average surface melt observed around majority of east Antarctic ice shelves, particularly near the Indian station ‘Maitri’, is of particular interest. Typical surface melting patterns observed over the third largest Antarctic ice shelf, Amery, are discussed in detail. Over northwest Himalaya, derived changes in snow water equivalent (ΔSWE) shows a good correlation between observed and calculated SWE variations. The present study demonstrates that simultaneous availability of high-resolution brightness temperature and backscatter data from SCATSAT-1 provides a unique opportunity to study the polar and mountain cryosphere.Keywords
Calving, Scatterometer, Sea-ice, Snow Water Equivalent, Surface Melt.Full Text
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