Joel T. Johnson
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View article: Modeling L-band Microwave Brightness Temperature Time Series for Firn Aquifers
Modeling L-band Microwave Brightness Temperature Time Series for Firn Aquifers Open
Firn aquifers play an important role in polar ice sheet hydrology and the associated mass and energy transport processes. Although firn aquifer extent has been mapped using passive microwave satellite observations, models to predict L-band…
View article: An Analysis of a Commercial GNSS-R Ocean Wind Speed Dataset
An Analysis of a Commercial GNSS-R Ocean Wind Speed Dataset Open
An analysis of Level-2 (L2) ocean wind speed retrievals from 1st May, 2021 to 1st June, 2024 derived from Spire, Inc.’s Global Navigation Satellite System Reflectometry observatories is presented. Comparisons of retrieved ocean surface win…
View article: Wildfire Threshold Detection and Progression Monitoring Using an Improved Radar Vegetation Index in California
Wildfire Threshold Detection and Progression Monitoring Using an Improved Radar Vegetation Index in California Open
To address the recent increase in wildfire severity and incidence, as well as the subsequent financial and physical costs, forest managers and wildland firefighting agencies rely on remotely sensed products for better decision-making and m…
View article: Retrieval of snow water equivalent from dual-frequency radar measurements: using time series to overcome the need for accurate a priori information
Retrieval of snow water equivalent from dual-frequency radar measurements: using time series to overcome the need for accurate a priori information Open
Measurements of radar backscatter are sensitive to snow water equivalent (SWE) across a wide range of frequencies, motivating proposals for satellite missions to measure global distributions of SWE. However, radar backscatter measurements …
View article: Ocean Wave Period Measurements Using S-Band Signals of Opportunity Reflections
Ocean Wave Period Measurements Using S-Band Signals of Opportunity Reflections Open
Ocean wave periods are estimated using measurements of S-band signals-of-opportunity reflections from the sea surface. The measurements were collected on an oil platform and show a time evolving Doppler centroid frequency and spectral widt…
View article: Simulating 0.4–2.5 GHz Brightness Temperatures of the Ross Ice Shelf, Antarctica
Simulating 0.4–2.5 GHz Brightness Temperatures of the Ross Ice Shelf, Antarctica Open
Ice shelves are important parts of the cryosphere that influence ice sheet dynamics and mass loss. The internal temperatures of ice shelves are currently known only from a few borehole sites or from glaciological models. Microwave radiomet…
View article: NISAR Time-Series Ratio Algorithm for Soil Moisture Retrieval: Prelaunch Evaluation With SMAPVEX12 Field Campaign Data
NISAR Time-Series Ratio Algorithm for Soil Moisture Retrieval: Prelaunch Evaluation With SMAPVEX12 Field Campaign Data Open
The NASA ISRO synthetic aperture radar (NISAR) mission scheduled for launch in 2024 will provide global L-band radar observations that can be applied to estimate land surface soil moisture. The mission's soil moisture product will be provi…
View article: Soil Moisture Retrieval Using CYGNSS Data in a Time-Series Ratio Method: Progress Update and Error Analysis, Part II
Soil Moisture Retrieval Using CYGNSS Data in a Time-Series Ratio Method: Progress Update and Error Analysis, Part II Open
This works reports updates to a previously-reported time-series ratio (TSR) algorithm for surface soil moisture retrieval from Cyclone Global Navigation Satellite System (CYGNSS) reflectivity data. Both the original and updated algorithms …
View article: Reservoir Water Level Monitoring Using CYGNSS's Level-1 Observations
Reservoir Water Level Monitoring Using CYGNSS's Level-1 Observations Open
The use of measurements from NASA's CYGNSS mission for the mapping of inland water bodies has been extensively demonstrated in past works. Despite this progress, the use of CYGNSS measurements for monitoring dynamic properties of water bod…
View article: Impacts of Spaceborne GNSS-R System Observations on Storm Surge Prediction: A Hurricane Harvey Case Study Using CYGNSS Full DDM Downlinks
Impacts of Spaceborne GNSS-R System Observations on Storm Surge Prediction: A Hurricane Harvey Case Study Using CYGNSS Full DDM Downlinks Open
This work assesses the impact of the Cyclone Global Navigation Satellite System (CYGNSS) (full delay-Doppler map) informed wind fields on storm surge simulations using the constellation's storm observations. In order to assess the impact o…
View article: On sea ice emission modeling for MOSAiC's L-band radiometric measurements
On sea ice emission modeling for MOSAiC's L-band radiometric measurements Open
The retrieval of sea ice thickness using L-band passive remote sensing requires robust models for emission from sea ice. In this work, measurements obtained from surface-based radiometers during the MOSAiC expedition are assessed with the …
View article: An Analysis of a Commercial GNSS-R Soil Moisture Dataset
An Analysis of a Commercial GNSS-R Soil Moisture Dataset Open
An analysis of a Level-2 (L2) soil moisture record extending from 1 May 2021 to 1 January 2024 derived from Spire, Inc.’s Global Navigation Satellite System Reflectometry (GNSS-R) observatories is presented. The product's sensitivity to la…
View article: On sea ice emission modeling for MOSAiC's L-band radiometric measurements
On sea ice emission modeling for MOSAiC's L-band radiometric measurements Open
The sea ice thickness retrieval using L-band passive remote sensing requires robust sea ice emission models. In this work, measurements from surface-based radiometers during MOSAiC are assessed with the Burke, Wilheit and SMRT models. Thes…
View article: Building a bimodal landscape: bedrock lithology and bed thickness controls on the morphology of Last Chance Canyon, New Mexico, USA
Building a bimodal landscape: bedrock lithology and bed thickness controls on the morphology of Last Chance Canyon, New Mexico, USA Open
We explore how rock properties and channel morphology vary with rock type in Last Chance Canyon, Guadalupe Mountains, New Mexico, USA. The rocks here are composed of horizontally to near-horizontally interbedded carbonate and sandstone. Th…
View article: Retrieval of SWE from dual-frequency radar measurements: Usingtimeseries to overcome the need for accurate a priori information
Retrieval of SWE from dual-frequency radar measurements: Usingtimeseries to overcome the need for accurate a priori information Open
Measurements of radar backscatter are sensitive to snow water equivalent (SWE) across a wide range of frequencies, motivating proposals for satellite missions to measure global distributions of SWE. However, radar backscatter measurements …
View article: Polar firn properties in Greenland and Antarctica and related effects on microwave brightness temperatures
Polar firn properties in Greenland and Antarctica and related effects on microwave brightness temperatures Open
In studying the mass balance of polar ice sheets, fluctuations in firn density near the surface is a major uncertainty. In this paper, we explore these variations at locations on the Greenland Ice Sheet and at the Dome C location in Antarc…
View article: Comment on egusphere-2022-1285
Comment on egusphere-2022-1285 Open
Abstract. We explore how rock properties and channel morphology vary with rock type in Last Chance canyon, Guadalupe mountains, New Mexico, USA. The rocks here are composed of horizontally to near horizontally interbedded carbonate and san…
View article: Comment on egusphere-2022-1285
Comment on egusphere-2022-1285 Open
Abstract. We explore how rock properties and channel morphology vary with rock type in Last Chance canyon, Guadalupe mountains, New Mexico, USA. The rocks here are composed of horizontally to near horizontally interbedded carbonate and san…
View article: Ice Sheet and Sea Ice Ultrawideband Microwave radiometric Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay
Ice Sheet and Sea Ice Ultrawideband Microwave radiometric Airborne eXperiment (ISSIUMAX) in Antarctica: first results from Terra Nova Bay Open
An airborne microwave wide-band radiometer (500–2000 MHz) was operated for the first time in Antarctica to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay to Dome C. The …
View article: CAGE13-7 Cruise Report: Gas Release Activity & Underwater Landslide Research Cruise
CAGE13-7 Cruise Report: Gas Release Activity & Underwater Landslide Research Cruise Open
The overall aim of the CAGE 13-7 cruise was to study the gas release activity from gas hydrated sub-seabed environments at the continental margin off Svalbard towards the Norwegian-Greenland Sea and Arctic Ocean. Acoustic measurements in t…
View article: Using Synthetic Cyclone Models for High Wind GNSS-R Calibration, Validation, and Algorithm Development: A CYGNSS Case Study
Using Synthetic Cyclone Models for High Wind GNSS-R Calibration, Validation, and Algorithm Development: A CYGNSS Case Study Open
This work reports a case study of the use of synthetic cyclone models for the development, assessment and validation of global navigation satellite system reflectometry (GNSS-R) wind speed remote sensing algorithms using a cyclone global n…
View article: Calibration Assessments of The NASA CSDA Spaceborne GNSS-R Dataset
Calibration Assessments of The NASA CSDA Spaceborne GNSS-R Dataset Open
GNSS-R is a form of microwave remote sensing in which receiver(s) operate in a specular (the incidence angle of the incoming signal is equivalent to the scattering angle of the reflected signal), passive (the satellite with a GNSS-R payloa…
View article: Building a Bimodal Landscape with Varying Bed Thicknesses in Last Chance Canyon, New Mexico
Building a Bimodal Landscape with Varying Bed Thicknesses in Last Chance Canyon, New Mexico Open
We explore how rock properties and channel morphology vary with rock type in Last Chance canyon, Guadalupe mountains, New Mexico, USA. The rocks here are composed of horizontally to near horizontally interbedded carbonate and sandstone. Th…
View article: A review of recent developments in low-frequency ultra-wideband microwave radiometry for studies of the cryosphere
A review of recent developments in low-frequency ultra-wideband microwave radiometry for studies of the cryosphere Open
Over the past decade, a series of airborne experiments in the Arctic and Antarctica explored microwave emission from sea ice and ice sheets at frequencies from 0.5 to 2 GHz. The experiments were motivated by the fact that lower frequencies…
View article: Comment on tc-2022-59
Comment on tc-2022-59 Open
Abstract. An airborne microwave wide-band radiometer (500â2000âMHz) was operated for the first time in Antarctica to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay t…
View article: Comment on tc-2022-59
Comment on tc-2022-59 Open
Abstract. An airborne microwave wide-band radiometer (500â2000âMHz) was operated for the first time in Antarctica to better understand the emission properties of sea ice, outlet glaciers and the interior ice sheet from Terra Nova Bay t…
View article: Comment on egusphere-2022-698
Comment on egusphere-2022-698 Open
Abstract. In studying the mass balance of polar ice sheets, the fluctuation of the firn density near the surface is a major uncertainty. In this paper, we explore these variations at locations in the Greenland Ice Sheet and at the Dome C l…