Gerald Heymsfield - Academia.edu (original) (raw)
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Papers by Gerald Heymsfield
AGU Fall Meeting Abstracts, Dec 1, 2012
Journal of Atmospheric and Oceanic Technology, Aug 1, 2023
A new instrument has been proposed for measuring surface air pressure over the marine surface wit... more A new instrument has been proposed for measuring surface air pressure over the marine surface with a combined active/passive scanning multichannel differential absorption radar to provide an estimate of the total atmospheric column oxygen content. A demonstrator instrument, the Microwave Barometric Radar and Sounder (MBARS), has been funded by the National Aeronautics and Space Administration for airborne test missions. Here, a proof-of-concept study to evaluate the potential impact of spaceborne surface pressure data on numerical weather prediction is performed using the Goddard Modeling and Assimilation Office global observing system simulation experiment (OSSE) framework. This OSSE framework employs the Goddard Earth Observing System model and the hybrid 4D ensemble variational Gridpoint Statistical Interpolation data assimilation system. Multiple flight and scanning configurations of potential spaceborne orbits are examined. Swath width and observation spacing for the surface pressure data are varied to explore a range of sampling strategies. For wider swaths, the addition of surface pressures reduces the root-mean-square surface pressure analysis error by as much as 20% over some ocean regions. The forecast sensitivity observation impact tool estimates impacts on the Pacific Ocean basin boundary layer 24-h forecast temperatures for spaceborne surface pressures that are on par with rawinsondes and aircraft and estimates greater impacts than the current network of ships and buoys. The largest forecast impacts are found in the Southern Hemisphere extratropics.
Spaceborne atmospheric radar technologies have been developed at the NASA Goddard Space Flight Ce... more Spaceborne atmospheric radar technologies have been developed at the NASA Goddard Space Flight Center (GSFC) in collaboration with Northrop Grumman Corporation (NGC). This paper gives an overview of future spaceborne radar concepts and key technologies targeted for large satellite platforms, the International Space Station (ISS), and SmallSat applications.
33rd Conference on Hurricanes and Tropical Meteorology, Apr 18, 2018
37th Conference on Radar Meteorology, Sep 16, 2015
AGU Fall Meeting Abstracts, Dec 1, 2020
Science, Sep 10, 2021
Water up Above-anvil cirrus plumes are stratospheric cloud formations that form downwind from the... more Water up Above-anvil cirrus plumes are stratospheric cloud formations that form downwind from the tops of some very strong thunderstorms. Despite their common occurrence, an adequate physical model explaining many of their features and effects does not exist. O’Neill et al . show that the storm supercell that extends into the stratosphere functions like a physical barrier, deflecting wind streams there like a topographic obstacle and driving a hydraulic jump downstream at the tropopause (see the Perspective by Smith). This feature triggers the intense injection of water vapor deep into the stratosphere, leading to a substantial increase in stratospheric humidity. —HJS
Monthly Weather Review, Sep 1, 1985
This brief paper illustrates some profiles of radar reflectivity in various precipitation systems... more This brief paper illustrates some profiles of radar reflectivity in various precipitation systems observed during the 1998-99 Tropical Rainfall Measuring Mission (TRMM) field campaigns. The profiles were collected by a nadir-viewing radar on the NASA ER-2, flying around 20 km altitude. This paper focuses on hurricane environments. Georges. The reflectivity factor (Z) is high in rain, and the spectrum of Z values narrow, implying uniformity along this 60 km long leg.
Geophysical Research Letters, Jun 27, 2023
Many studies have performed microphysical retrievals using radars of different frequencies, platf... more Many studies have performed microphysical retrievals using radars of different frequencies, platforms, and methodologies. However, little is known about the consistency of retrievals derived from different radar platforms (i.e., airborne or spaceborne vs. ground‐based) and their methodologies. This study is the first to directly compare snow mass‐weighted mean diameter (Dm) retrievals from both nadir‐pointing airborne multi‐frequency radars and ground‐based polarimetric range‐height indicator radar scans along the same airborne flight track with a resolution of . Dm retrievals between each method produced mean absolute errors of 0.49, 0.74, and 0.93 mm where the largest differences were between the ground and aircraft retrievals. A triple‐frequency analysis suggests the possibility that snow aggregates were generally composed of needles. These results can be used as a benchmark for comparing retrieval methodologies and highlight the continued uncertainty regarding the optimal approach for ice microphysical retrievals.
Frontiers in remote sensing, Feb 13, 2023
This study simulates V-band sea surface reflectance and normalized radar crosssection (NRCS) for ... more This study simulates V-band sea surface reflectance and normalized radar crosssection (NRCS) for sea surface air pressure barometry using a differential absorption radar operating at three spectrally even spaced close frequency bands (65.5, 67.75 and 70.0 GHz) with ± 15°cross-track scanning angle. The reflectance ratios of two neighboring frequency pairs and the ratio of the two ratios or three-channel approach are the focus of this study. Impacts of major sea surface geophysical variables such as sea surface temperature, wind, salinity, whitecap, and incidence angle on these reflection properties are analyzed. The reflection simulation is essentially based on geometric optics of rough sea surface. Simulation shows that NRCS values are sufficiently strong within the scanning angle and sea surface salinity would only introduce minimal variations in the surface reflection. The impact of sea surface reflection variations with sea surface temperature, wind, and whitecaps on sea surface barometry are mitigated when the ratios of frequencypaired radar signals are used. Furthermore, the ratios of a three-channel approach are very close to unity and calibration or compensation for the reflectance ratios may not be needed for sea level pressure retrievals. These results improve our understanding of sea surface reflection variations and would help the system design and development.
AGU Fall Meeting Abstracts, Dec 1, 2020
AGU Fall Meeting Abstracts, Dec 1, 2018
Journal of Atmospheric and Oceanic Technology, Mar 1, 2021
The High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) dual-frequency conically scann... more The High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) dual-frequency conically scanning airborne radar provides estimates of the range-profiled mean Doppler and backscattered power from the precipitation and surface. A velocity-azimuth display analysis yields near-surface estimates of the mean horizontal wind vector y h in cases in which precipitation is present throughout the scan. From the surface return, the normalized radar cross section (NRCS) is obtained, which, by a method previously described, can be corrected for path attenuation. Comparisons between y h and the attenuation-corrected NRCS are used to derive transfer functions that provide estimates of the wind vector from the NRCS data under both rain and rain-free conditions. A reasonably robust transfer function is found by using the mean NRCS (hNRCSi) over the scan along with a filtering of the data based on a Fourier series analysis of y h and the NRCS. The approach gives good correlation coefficients between y h and hNRCSi at Ku band at incidence angles of 308 and 408. The correlation degrades if the Ka-band data are used rather than the Ku band.
AGU Fall Meeting Abstracts, Dec 1, 2016
AGU Fall Meeting Abstracts, Dec 1, 2012
Journal of Atmospheric and Oceanic Technology, Aug 1, 2023
A new instrument has been proposed for measuring surface air pressure over the marine surface wit... more A new instrument has been proposed for measuring surface air pressure over the marine surface with a combined active/passive scanning multichannel differential absorption radar to provide an estimate of the total atmospheric column oxygen content. A demonstrator instrument, the Microwave Barometric Radar and Sounder (MBARS), has been funded by the National Aeronautics and Space Administration for airborne test missions. Here, a proof-of-concept study to evaluate the potential impact of spaceborne surface pressure data on numerical weather prediction is performed using the Goddard Modeling and Assimilation Office global observing system simulation experiment (OSSE) framework. This OSSE framework employs the Goddard Earth Observing System model and the hybrid 4D ensemble variational Gridpoint Statistical Interpolation data assimilation system. Multiple flight and scanning configurations of potential spaceborne orbits are examined. Swath width and observation spacing for the surface pressure data are varied to explore a range of sampling strategies. For wider swaths, the addition of surface pressures reduces the root-mean-square surface pressure analysis error by as much as 20% over some ocean regions. The forecast sensitivity observation impact tool estimates impacts on the Pacific Ocean basin boundary layer 24-h forecast temperatures for spaceborne surface pressures that are on par with rawinsondes and aircraft and estimates greater impacts than the current network of ships and buoys. The largest forecast impacts are found in the Southern Hemisphere extratropics.
Spaceborne atmospheric radar technologies have been developed at the NASA Goddard Space Flight Ce... more Spaceborne atmospheric radar technologies have been developed at the NASA Goddard Space Flight Center (GSFC) in collaboration with Northrop Grumman Corporation (NGC). This paper gives an overview of future spaceborne radar concepts and key technologies targeted for large satellite platforms, the International Space Station (ISS), and SmallSat applications.
33rd Conference on Hurricanes and Tropical Meteorology, Apr 18, 2018
37th Conference on Radar Meteorology, Sep 16, 2015
AGU Fall Meeting Abstracts, Dec 1, 2020
Science, Sep 10, 2021
Water up Above-anvil cirrus plumes are stratospheric cloud formations that form downwind from the... more Water up Above-anvil cirrus plumes are stratospheric cloud formations that form downwind from the tops of some very strong thunderstorms. Despite their common occurrence, an adequate physical model explaining many of their features and effects does not exist. O’Neill et al . show that the storm supercell that extends into the stratosphere functions like a physical barrier, deflecting wind streams there like a topographic obstacle and driving a hydraulic jump downstream at the tropopause (see the Perspective by Smith). This feature triggers the intense injection of water vapor deep into the stratosphere, leading to a substantial increase in stratospheric humidity. —HJS
Monthly Weather Review, Sep 1, 1985
This brief paper illustrates some profiles of radar reflectivity in various precipitation systems... more This brief paper illustrates some profiles of radar reflectivity in various precipitation systems observed during the 1998-99 Tropical Rainfall Measuring Mission (TRMM) field campaigns. The profiles were collected by a nadir-viewing radar on the NASA ER-2, flying around 20 km altitude. This paper focuses on hurricane environments. Georges. The reflectivity factor (Z) is high in rain, and the spectrum of Z values narrow, implying uniformity along this 60 km long leg.
Geophysical Research Letters, Jun 27, 2023
Many studies have performed microphysical retrievals using radars of different frequencies, platf... more Many studies have performed microphysical retrievals using radars of different frequencies, platforms, and methodologies. However, little is known about the consistency of retrievals derived from different radar platforms (i.e., airborne or spaceborne vs. ground‐based) and their methodologies. This study is the first to directly compare snow mass‐weighted mean diameter (Dm) retrievals from both nadir‐pointing airborne multi‐frequency radars and ground‐based polarimetric range‐height indicator radar scans along the same airborne flight track with a resolution of . Dm retrievals between each method produced mean absolute errors of 0.49, 0.74, and 0.93 mm where the largest differences were between the ground and aircraft retrievals. A triple‐frequency analysis suggests the possibility that snow aggregates were generally composed of needles. These results can be used as a benchmark for comparing retrieval methodologies and highlight the continued uncertainty regarding the optimal approach for ice microphysical retrievals.
Frontiers in remote sensing, Feb 13, 2023
This study simulates V-band sea surface reflectance and normalized radar crosssection (NRCS) for ... more This study simulates V-band sea surface reflectance and normalized radar crosssection (NRCS) for sea surface air pressure barometry using a differential absorption radar operating at three spectrally even spaced close frequency bands (65.5, 67.75 and 70.0 GHz) with ± 15°cross-track scanning angle. The reflectance ratios of two neighboring frequency pairs and the ratio of the two ratios or three-channel approach are the focus of this study. Impacts of major sea surface geophysical variables such as sea surface temperature, wind, salinity, whitecap, and incidence angle on these reflection properties are analyzed. The reflection simulation is essentially based on geometric optics of rough sea surface. Simulation shows that NRCS values are sufficiently strong within the scanning angle and sea surface salinity would only introduce minimal variations in the surface reflection. The impact of sea surface reflection variations with sea surface temperature, wind, and whitecaps on sea surface barometry are mitigated when the ratios of frequencypaired radar signals are used. Furthermore, the ratios of a three-channel approach are very close to unity and calibration or compensation for the reflectance ratios may not be needed for sea level pressure retrievals. These results improve our understanding of sea surface reflection variations and would help the system design and development.
AGU Fall Meeting Abstracts, Dec 1, 2020
AGU Fall Meeting Abstracts, Dec 1, 2018
Journal of Atmospheric and Oceanic Technology, Mar 1, 2021
The High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) dual-frequency conically scann... more The High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) dual-frequency conically scanning airborne radar provides estimates of the range-profiled mean Doppler and backscattered power from the precipitation and surface. A velocity-azimuth display analysis yields near-surface estimates of the mean horizontal wind vector y h in cases in which precipitation is present throughout the scan. From the surface return, the normalized radar cross section (NRCS) is obtained, which, by a method previously described, can be corrected for path attenuation. Comparisons between y h and the attenuation-corrected NRCS are used to derive transfer functions that provide estimates of the wind vector from the NRCS data under both rain and rain-free conditions. A reasonably robust transfer function is found by using the mean NRCS (hNRCSi) over the scan along with a filtering of the data based on a Fourier series analysis of y h and the NRCS. The approach gives good correlation coefficients between y h and hNRCSi at Ku band at incidence angles of 308 and 408. The correlation degrades if the Ka-band data are used rather than the Ku band.
AGU Fall Meeting Abstracts, Dec 1, 2016