scholarly journals SMAP Salinity Retrievals near the Sea-Ice Edge Using Multi-Channel AMSR2 Brightness Temperatures

2021 ◽  
Vol 13 (24) ◽  
pp. 5120
Author(s):  
Thomas Meissner ◽  
Andrew Manaster
Keyword(s):  
Sea Ice ◽  
Large Error ◽  
Sea Surface Salinity ◽  
Retrieval Algorithm ◽  
Surface Salinity ◽  
Band Frequency ◽  
Brightness Temperatures ◽  
L Band ◽  
Ice Edge ◽  
Sea Ice Edge

Sea-ice contamination in the antenna field of view constitutes a large error source in retrieving sea-surface salinity (SSS) with the spaceborne Soil Moisture Active Passive (SMAP) L-band radiometer. This is a major obstacle in the current NASA/Remote Sensing Systems (RSS) SMAP SSS retrieval algorithm in regards to obtaining accurate SSS measurements in the polar oceans. Our analysis finds a strong correlation between 8-day averaged SMAP L-band brightness temperature (TB) bias and TB measurements from the Advanced Microwave Scanning Radiometer (AMSR2) in the C-through Ka-band frequency range for sea-ice contaminated ocean scenes. We show how this correlation can be employed to develop: (1) a discriminant analysis that is able to reliably flag the SMAP observations for sea-ice contamination and (2) subsequently remove the sea-ice contamination from the SMAP observations, which results in significantly more accurate SMAP SSS retrievals near the sea-ice edge. We provide a case study that evaluates the performance of the proposed sea-ice flagging and correction algorithm. Our method is also able to detect drifting icebergs, which go often undetected in many available standard sea-ice products and thus result in spurious SMAP SSS retrievals.

scholarly journals Weekly gridded Aquarius L-band radiometer/scatterometer observations and salinity retrievals over the polar regions – Part 2: Initial product analysis

2014 ◽  
Vol 8 (3) ◽  
pp. 915-930 ◽  
Author(s):  
L. Brucker ◽  
E. P. Dinnat ◽  
L. S. Koenig
Keyword(s):  
Sea Ice ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sea Surface Salinity ◽  
Product Analysis ◽  
Surface Salinity ◽  
Initial Product ◽  
Band Frequency ◽  
Freeze Thaw ◽  
L Band

Abstract. Following the development and availability of Aquarius weekly polar-gridded products, this study presents the spatial and temporal radiometer and scatterometer observations at L band (frequency ~1.4 GHz) over the cryosphere including the Greenland and Antarctic ice sheets, sea ice in both hemispheres, and over sub-Arctic land for monitoring the soil freeze/thaw state. We provide multiple examples of scientific applications for the L-band data over the cryosphere. For example, we show that over the Greenland Ice Sheet, the unusual 2012 melt event lead to an L-band brightness temperature (TB) sustained decrease of ~5 K at horizontal polarization. Over the Antarctic ice sheet, normalized radar cross section (NRCS) observations recorded during ascending and descending orbits are significantly different, highlighting the anisotropy of the ice cover. Over sub-Arctic land, both passive and active observations show distinct values depending on the soil physical state (freeze/thaw). Aquarius sea surface salinity (SSS) retrievals in the polar waters are also presented. SSS variations could serve as an indicator of fresh water input to the ocean from the cryosphere, however the presence of sea ice often contaminates the SSS retrievals, hindering the analysis. The weekly grided Aquarius L-band products used are distributed by the US Snow and Ice Data Center at http://nsidc.org/data/aquarius/index.html , and show potential for cryospheric studies.

scholarly journals Weekly-gridded Aquarius L-band radiometer/scatterometer observations and salinity retrievals over the polar regions: applications for cryospheric studies

2013 ◽  
Vol 7 (6) ◽  
pp. 5921-5970 ◽  
Author(s):  
L. Brucker ◽  
E. Dinnat ◽  
L. S. Koenig
Keyword(s):  
Sea Ice ◽  
Grid Cell ◽  
Frozen Soil ◽  
Sea Surface Salinity ◽  
Data Sets ◽  
Polar Regions ◽  
Surface Salinity ◽  
Band Frequency ◽  
L Band ◽  
Polar Oceans

Abstract. Passive and active observations at L band (frequency ~1.413 GHz) from the Aquarius/SAC-D mission offer new capabilities to study the polar regions. However, due to the lack of polar-gridded products, applications over the cryosphere are limited. To allow for an efficient use of the Aquarius data over the polar regions, and to move forward our understanding of the L-band observations of ice sheet, sea ice, permafrost, and polar oceans, we present three weekly-polar-gridded products. Aquarius data at latitudes higher than 50° were averaged and gridded into three weekly products of Brightness Temperature (TB), Normalized Radar Cross Section (NRCS), and Sea Surface Salinity (SSS). These products are suited for cryospheric studies, and each grid cell contains sea ice fraction and the standard deviation of TB, NRCS, and SSS along with the number of footprint observations collected during the seven-day cycle. The data sets are produced on the version 2.0 Equal-Area Scalable Earth (EASE2.0) grid, with a grid cell resolution of 36 km. This paper describes the products, and presents maps and time series of Aquarius weekly-gridded data over the Greenland and Antarctic ice sheets, sea ice in both hemispheres, subarctic land where seasonal snow and frozen soil may exist, and the polar oceans. A brief analysis of L-band observations is given to encourage future use of the products. They can be used for improving our understanding of low microwave frequency observations, and for the development of algorithms. The new weekly-polar-gridded datasets start in August 2011, with the first Aquarius observations, and it is anticipated that they will be updated on a monthly basis following the release schedule of the Level 2 data sets.

scholarly journals Weekly gridded Aquarius L-band radiometer/scatterometer observations and salinity retrievals over the polar regions – Part 1: Product description

2014 ◽  
Vol 8 (3) ◽  
pp. 905-913 ◽  
Author(s):  
L. Brucker ◽  
E. P. Dinnat ◽  
L. S. Koenig
Keyword(s):  
Sea Ice ◽  
Grid Cell ◽  
Sea Surface Salinity ◽  
Data Sets ◽  
Polar Regions ◽  
Surface Salinity ◽  
Monthly Basis ◽  
Band Frequency ◽  
L Band ◽  
Product Description

Abstract. Passive and active observations at L band (frequency ~1.4 GHz) from the Aquarius/SAC-D mission offer new capabilities to study the polar regions. Due to the lack of polar-gridded products, however, applications over the cryosphere have been limited. We present three weekly polar-gridded products of Aquarius data to improve our understanding of L-band observations of ice sheets, sea ice, permafrost, and the polar oceans. Additionally, these products intend to facilitate access to L-band data, and can be used to assist in algorithm developments. Aquarius data at latitudes higher than 50° are averaged and gridded into weekly products of brightness temperature (TB), normalized radar cross section (NRCS), and sea surface salinity (SSS). Each grid cell also contains sea ice fraction, the standard deviation of TB, NRCS, and SSS, and the number of footprint observations collected during the seven-day cycle. The largest 3 dB footprint dimensions are 97 km × 156 km and 74 km × 122 km (along × across track) for the radiometers and scatterometer, respectively. The data is gridded to the Equal-Area Scalable Earth version 2.0 (EASE2.0) grid, with a grid cell resolution of 36 km. The data sets start in August 2011, with the first Aquarius observations and will be updated on a monthly basis following the release schedule of the Aquarius Level 2 data sets. The weekly gridded products are distributed by the US National Snow and Ice Data Center at http://nsidc.org/data/aquarius/index.html .

scholarly journals Retrieving sea surface salinity with multiangular L-band brightness temperatures: Improvement by spatiotemporal averaging

Radio Science ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. Camps ◽  
M. Vall-llossera ◽  
L. Batres ◽  
F. Torres ◽  
N. Duffo ◽  
...  
Keyword(s):  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Salinity ◽  
Brightness Temperatures ◽  
L Band

Use of C-Band Scatterometer for Sea Ice Edge Identification

2012 ◽  
Vol 50 (7) ◽  
pp. 2669-2677 ◽  
Author(s):  
Lars-Anders Breivik ◽  
Steinar Eastwood ◽  
Thomas Lavergne
Keyword(s):  
Sea Ice ◽  
Ice Edge ◽  
Sea Ice Edge

On the Bering Sea ice edge front

1985 ◽  
Vol 90 (C2) ◽  
pp. 3185 ◽  
Author(s):  
Robin D. Muench ◽  
James D. Schumacher
Keyword(s):  
Sea Ice ◽  
Bering Sea ◽  
Ice Edge ◽  
Sea Ice Edge ◽  
The Bering Sea

Surface-based and Fully Polarimetric L-band Frequency Scatterometer System for Field Measurements of Sea Ice

2021 ◽  
Author(s):  
Randall Kenneth Scharien ◽  
Torsten Geldsetzer ◽  
Jim Mead ◽  
Vishnu Nandan ◽  
Mallik Mahmud ◽  
...  
Keyword(s):  
Sea Ice ◽  
Field Measurements ◽  
Band Frequency ◽  
L Band

scholarly journals Sea ice led to poleward-shifted winds at the Last Glacial Maximum: the influence of state dependency on CMIP5 and PMIP3 models

2016 ◽  
Vol 12 (12) ◽  
pp. 2241-2253 ◽  
Author(s):  
Louise C. Sime ◽  
Dominic Hodgson ◽  
Thomas J. Bracegirdle ◽  
Claire Allen ◽  
Bianca Perren ◽  
...  
Keyword(s):  
Sea Ice ◽  
Last Glacial Maximum ◽  
Heat Fluxes ◽  
Glacial Maximum ◽  
State Dependency ◽  
Last Glacial ◽  
Poleward Shift ◽  
Future Warming ◽  
Ice Edge ◽  
Sea Ice Edge

Abstract. Latitudinal shifts in the Southern Ocean westerly wind jet could drive changes in the glacial to interglacial ocean CO2 inventory. However, whilst CMIP5 model results feature consistent future-warming jet shifts, there is considerable disagreement in deglacial-warming jet shifts. We find here that the dependence of pre-industrial (PI) to Last Glacial Maximum (LGM) jet shifts on PI jet position, or state dependency, explains less of the shifts in jet simulated by the models for the LGM compared with future-warming scenarios. State dependence is also weaker for intensity changes, compared to latitudinal shifts in the jet. Winter sea ice was considerably more extensive during the LGM. Changes in surface heat fluxes, due to this sea ice change, probably had a large impact on the jet. Models that both simulate realistically large expansions in sea ice and feature PI jets which are south of 50° S show an increase in wind speed around 55° S and can show a poleward shift in the jet between the PI and the LGM. However, models with the PI jet positioned equatorwards of around 47° S do not show this response: the sea ice edge is too far from the jet for it to respond. In models with accurately positioned PI jets, a +1° difference in the latitude of the sea ice edge tends to be associated with a −0.85° shift in the 850 hPa jet. However, it seems that around 5° of expansion of LGM sea ice is necessary to hold the jet in its PI position. Since the Gersonde et al. (2005) data support an expansion of more than 5°, this result suggests that a slight poleward shift and intensification was the most likely jet change between the PI and the LGM. Without the effect of sea ice, models simulate poleward-shifted westerlies in warming climates and equatorward-shifted westerlies in colder climates. However, the feedback of sea ice counters and reverses the equatorward trend in cooler climates so that the LGM winds were more likely to have also been shifted slightly poleward.

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