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 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 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 Sea Ice Concentration and Sea Ice Extent Mapping with L-Band Microwave Radiometry and GNSS-R Data from the FFSCat Mission Using Neural Networks

2021 ◽  
Vol 13 (6) ◽  
pp. 1139
Author(s):  
David Llaveria ◽  
Juan Francesc Munoz-Martin ◽  
Christoph Herbert ◽  
Miriam Pablos ◽  
Hyuk Park ◽  
...  
Keyword(s):  
Sea Ice ◽  
Microwave Radiometer ◽  
Cost Effective ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
Neural Network Approach ◽  
Ice Concentration ◽  
L Band ◽  
Moderate Cost

CubeSat-based Earth Observation missions have emerged in recent times, achieving scientifically valuable data at a moderate cost. FSSCat is a two 6U CubeSats mission, winner of the ESA S3 challenge and overall winner of the 2017 Copernicus Masters Competition, that was launched in September 2020. The first satellite, 3Cat-5/A, carries the FMPL-2 instrument, an L-band microwave radiometer and a GNSS-Reflectometer. This work presents a neural network approach for retrieving sea ice concentration and sea ice extent maps on the Arctic and the Antarctic oceans using FMPL-2 data. The results from the first months of operations are presented and analyzed, and the quality of the retrieved maps is assessed by comparing them with other existing sea ice concentration maps. As compared to OSI SAF products, the overall accuracy for the sea ice extent maps is greater than 97% using MWR data, and up to 99% when using combined GNSS-R and MWR data. In the case of Sea ice concentration, the absolute errors are lower than 5%, with MWR and lower than 3% combining it with the GNSS-R. The total extent area computed using this methodology is close, with 2.5% difference, to those computed by other well consolidated algorithms, such as OSI SAF or NSIDC. The approach presented for estimating sea ice extent and concentration maps is a cost-effective alternative, and using a constellation of CubeSats, it can be further improved.

scholarly journals Implications of sea-ice biogeochemistry for oceanic production and emissions of dimethyl sulfide in the Arctic

2017 ◽  
Vol 14 (12) ◽  
pp. 3129-3155 ◽  
Author(s):  
Hakase Hayashida ◽  
Nadja Steiner ◽  
Adam Monahan ◽  
Virginie Galindo ◽  
Martine Lizotte ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Column ◽  
Dimethyl Sulfide ◽  
Phytoplankton Bloom ◽  
Model Simulation ◽  
Field Measurements ◽  
Sulfur Cycle ◽  
The Arctic ◽  
Model Parameters ◽  
Ocean Ecosystem

Abstract. Sea ice represents an additional oceanic source of the climatically active gas dimethyl sulfide (DMS) for the Arctic atmosphere. To what extent this source contributes to the dynamics of summertime Arctic clouds is, however, not known due to scarcity of field measurements. In this study, we developed a coupled sea ice–ocean ecosystem–sulfur cycle model to investigate the potential impact of bottom-ice DMS and its precursor dimethylsulfoniopropionate (DMSP) on the oceanic production and emissions of DMS in the Arctic. The results of the 1-D model simulation were compared with field data collected during May and June of 2010 in Resolute Passage. Our results reproduced the accumulation of DMS and DMSP in the bottom ice during the development of an ice algal bloom. The release of these sulfur species took place predominantly during the earlier phase of the melt period, resulting in an increase of DMS and DMSP in the underlying water column prior to the onset of an under-ice phytoplankton bloom. Production and removal rates of processes considered in the model are analyzed to identify the processes dominating the budgets of DMS and DMSP both in the bottom ice and the underlying water column. When openings in the ice were taken into account, the simulated sea–air DMS flux during the melt period was dominated by episodic spikes of up to 8.1 µmol m−2 d−1. Further model simulations were conducted to assess the effects of the incorporation of sea-ice biogeochemistry on DMS production and emissions, as well as the sensitivity of our results to changes of uncertain model parameters of the sea-ice sulfur cycle. The results highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that should be better constrained by new observations.

scholarly journals DESIGN OF CARTESIAN FEEDBACK RF POWER AMPLIFIER FOR L-BAND FREQUENCY RANGE

2008 ◽  
Vol 2 ◽  
pp. 207-222 ◽  
Author(s):  
Jit Singh Mandeep ◽  
Anand Lokesh ◽  
Syed Idris Syed Hassan ◽  
mohd nazri Mahmud ◽  
Mohd Fadzil Ain
Keyword(s):  
Power Amplifier ◽  
Rf Power ◽  
Frequency Range ◽  
Band Frequency ◽  
Rf Power Amplifier ◽  
L Band

scholarly journals Study of spatial and temporal characteristics of L-band scintillations over the Indian low-latitude region and their possible effects on GPS navigation

2006 ◽  
Vol 24 (6) ◽  
pp. 1567-1580 ◽  
Author(s):  
P. V. S. Rama Rao ◽  
S. Gopi Krishna ◽  
K. Niranjan ◽  
D. S. V. V. D. Prasad
Keyword(s):  
Indian Region ◽  
Sunspot Activity ◽  
Navigation Systems ◽  
Positional Accuracy ◽  
Band Frequency ◽  
Latitude Range ◽  
Ionospheric Scintillations ◽  
Simultaneous Study ◽  
L Band ◽  
Spatio Temporal

Abstract. The scintillation data (S4-index) at the L-band frequency of 1.575GHz, recorded from a total of 18 GPS receivers installed at different locations in India under the GAGAN project, have provided us with a unique opportunity, for the first time in the Indian region, to make a simultaneous study of spatio-temporal and intensity characteristics of the trans-ionospheric scintillations during the 18-month, low sunspot activity (LSSA) period from January 2004 to July 2005. During this period, the occurrence of scintillations is found to be maximum around the pre-midnight hours of equinox months, with very little activity during the post-midnight hours. No significant scintillation activity is observed during the summer and winter months of the period of observation. The intensity (S4 index) of the scintillation activity is stronger around the equatorial ionization anomaly (EIA) region in the geographic latitude range of 15° to 25° N in the Indian region. These scintillations are often accompanied by the TEC depletions with durations ranging from 5 to 25 min and magnitudes from 5 to 15 TEC units which affect the positional accuracy of the GPS by 1 to 3 m. Further, during the intense scintillation events (S4>0.45≈10 dB), the GPS receiver is found to lose its lock for a short duration of 1 to 4 min, increasing the error bounds effecting the integrity of the SBAS operation. During the present period of study, a total of 395 loss of lock events are observed in the Indian EIA region; this number is likely to increase during the high sunspot activity (HSSA) period, creating more adverse conditions for the trans-ionospheric communications and the GPS-based navigation systems.

scholarly journals Effects of decimetre-scale surface roughness on L-band Brightness Temperature of Sea Ice

2019 ◽  
Author(s):  
Maciej Miernecki ◽  
Lars Kaleschke ◽  
Nina Maaß ◽  
Stefan Hendricks ◽  
Sten Schmidl Søbjrg
Keyword(s):  
Surface Roughness ◽  
Sea Ice ◽  
Brightness Temperature ◽  
Large Scale ◽  
Ice Thickness ◽  
Emission Model ◽  
Vertical Polarization ◽  
Sea Ice Thickness ◽  
L Band ◽  
Scale Surface

Abstract. Sea ice thickness measurements with L-band radiometry is a technique which allows daily, weather-independent monitoring of the polar sea ice cover. The sea-ice thickness retrieval algorithms relay on the sensitivity of the L-band brightness temperature to sea-ice thickness. In this work, we investigate the decimetre-scale surface roughness as a factor influencing the L-band emissions from sea ice. We used an airborne laser scanner to construct a digital elevation model of the sea ice surface. We found that the probability density function of surface slopes is exponential for a range of degrees of roughness. Then we applied the geometrical optics, bounded with the MIcrowave L-band LAyered Sea ice emission model in the Monte Carlo simulation to simulate the effects of surface roughness. According to this simulations, the most affected by surface roughness is the vertical polarization around Brewster's angle, where the decrease in brightness temperature can reach 8 K. The vertical polarization for the same configuration exhibits a 4 K increase. The near-nadir angles are little affected, up to 2.6 K decrease for the most deformed ice. Overall the effects of large-scale surface roughness can be expressed as a superposition of two factors: the change in intensity and the polarization mixing. The first factor depends on surface permittivity, second shows little dependence on it. Comparison of the brightness temperature simulations with the radiometer data does not yield definite results.

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