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Xiaoyan Chen
,
Graham D. Quartly
, and
Ge Chen

Abstract

Argo floats are widely used to characterize vertical structures of ocean eddies, yet their capability to invert sea-surface features of eddies, especially those overlooked by available altimeters, has not been explored. In this paper, we propose an “interior-to-surface” inversion algorithm to effectively expand the capacity of eddy detection by estimating altimeter-missed eddies’ surface attributes from their Argo-derived potential density anomaly profiles, given that interior property and surface signature of eddies are highly correlated. An altimeter-calibrated machine learning ensemble is employed for the inversion training based on the joint altimeter-Argo eddy data and shows promising performance with mean absolute errors of 5.4 km, 0.5 cm, and 14.3 cm2/s2 for eddy radius, amplitude, and kinetic energy. Then, the trained ensemble model is applied to independently invert the properties of eddies captured by an Argo-alone detection scheme, which yields a high spatiotemporal consistency with their altimeter-captured counterparts. In particular, a portion of Argo-alone eddies is ~25% smaller than altimeter-derived ones, indicating Argo’s unique capability of profiling weaker submesoscale eddies. Sea surface temperature and chlorophyll data are further applied to validate the reliability of eddies identified and characterized by the Argo-only algorithm. This new methodology effectively complements that of altimetry in eddy detecting and can be expanded to estimate other physical/biochemical eddy variables from a variety of in-situ observations.

Open access
Taylor D. Swaim
,
Emalee Hough
,
Zachary Yap
,
Jamey D. Jacob
,
Siddharth Krishnamoorthy
,
Daniel C. Bowman
,
Léo Martire
,
Attila Komjathy
, and
Brian R. Elbing

Abstract

Heliotropes are passive solar hot-air balloons that are capable of achieving nearly level flight within the lower stratosphere for several hours. These inexpensive flight platforms enable stratospheric sensing with high cadence enabled by the low cost to manufacture, but their performance has not yet been assessed systematically. During July–September of 2021, 29 heliotropes were successfully launched from Oklahoma and achieved float altitude as part of the Balloon-based Acoustic Seismology Study (BASS). All of the heliotrope envelopes were nearly identical with only minor variations to the flight line throughout the campaign. Flight data collected during this campaign comprise a large sample to characterize the typical heliotrope flight behavior during launch, ascent, float, and descent. Each flight stage is characterized, dependence on various parameters is quantified, and a discussion of nominal and anomalous flights is provided.

Restricted access
Free access
Elizabeth M. Berg
,
Louis J. Urtecho
,
Siddharth Krishnamoorthy
,
Elizabeth A. Silber
,
Andrew Sparks
, and
Daniel C. Bowman

Abstract

Heating of the surficial layer of the atmosphere often generates convective vortices, known as “dust devils” when they entrain visible debris. Convective vortices are common on both Earth and Mars, where they affect the climate via dust loading, contribute to wind erosion, impact the efficiency of photovoltaic systems, and potentially result in injury and property damage. However, long-duration terrestrial convective vortex activity records are rare. We have developed a high-precision and high-recall method to extract convective vortex signatures from infrasound microbarometer data streams. The techniques utilizes a wavelet-based detector to capture potential events and then a template matching system to extract the duration of the vortex. Since permanent and temporary infrasound sensors networks are present throughout the globe (many with open data), our method unlocks a vast new convective vortex dataset without requiring the deployment of specialized instrumentation.

Significance Statement

Convective vortices, or “dust devils,” contribute to regional dust loading in Earth’s atmosphere. However, long-duration convective vortex activity records are rare. We came up with a way to autonomously detect the pressure signatures left by convective vortices striking low-frequency sound, or “infrasound,” sensors. Since permanent infrasound stations have been active for decades, our method has the potential to add orders-of-magnitude more events than previously catalogued.

Open access
Je-Yuan Hsu

Abstract

A new rotating axes method (RAM) is developed to improve the vertical resolution of the horizontal current velocity measurements u at EM-APEX floats. Unlike the traditional harmonic fitting method (HFM), which yields u averaged in 50-s intervals, RAM decodes and interprets 1-Hz measurements of horizontal seawater velocity u ˜ , and averages u ˜ in 12-s windows for removing wind waves with a typical peak frequency ∼ 0.12 Hz. Estimates of u from RAM agree with those from HFM but with a higher vertical resolution of ∼1.5 m, 4 times better than HFM. Note that extracting float signals due to seawater motion needs to assume slow-varying voltage offset ΔΦoffset. The typical variations of estimated ΔΦoffset do not affect the results of u significantly. Estimates of u are excluded when ΔΦoffset fluctuates strongly in time and scatter significantly. RAM is applied to float measurements taken near Mien-Hua Canyon, Taiwan. Composite vertical shear spectra Ψ computed using u from RAM exhibit a spectral slope of −1, as expected for the saturated internal waves in the vertical fine-scale range. The RAM provides EM-APEX float’s horizontal velocity measurements into fine vertical scales and will help improve our understanding of energy cascade from internal wave breaking and shear instability into turbulence mixing.

Restricted access
Yoshiro Yamada
,
Subrena Harris
,
Michael Hayes
,
Rob Simpson
,
Werenfrid Wimmer
,
Raymond Holmes
,
Tim Nightingale
,
Arrow Lee
,
Nis Jepsen
,
Nicole Morgan
,
Frank-M. Göttsche
,
Raquel Niclòs
,
Martín Perelló
,
Craig Donlon
, and
Nigel Fox

Abstract

An international comparison of field deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted in June 2022. The campaign comprised a laboratory comparison and a field comparison. In the laboratory part, the radiometers were compared with reference standard blackbodies, while the same was done with the blackbodies used for the calibration of the radiometers against a transfer standard radiometer. Reference values were provided by the National Physical Laboratory (NPL), traceable to the primary standard on the International Temperature Scale of 1990. This was followed by the field comparison at a seaside pier on the south coast of England, where the radiometers were compared against each other while viewing the closely adjacent surface of the sea. This paper reports the results of the laboratory comparison of radiometers and blackbodies. For the blackbody comparison, the brightness temperature of the blackbody reported by the participants agreed with the reference value measured by the NPL transfer standard radiometer within the uncertainties for all temperatures and for all blackbodies. For the radiometer comparison, the temperature range of most interest from the SSTskin retrieval point of view is 10°–30°C, and in this temperature range, and up to the maximum comparison temperature of 50°C, all participants’ reported results were in agreement with the reference. On the other hand, below 0°C the reported values showed divergence from the reference and the differences exceeded the uncertainties. The divergence shows there is room for improvement in uncertainty estimation at lower temperatures, although it will have limited implication in the SSTskin retrieval.

Restricted access
Yoshiro Yamada
,
Subrena Harris
,
Werenfrid Wimmer
,
Raymond Holmes
,
Tim Nightingale
,
Arrow Lee
,
Nis Jepsen
,
Nicole Morgan
,
Frank-M. Göttsche
,
Raquel Niclòs
,
Martín Perelló
,
Vicente Garcia-Santos
,
Craig Donlon
, and
Nigel Fox

Abstract

An international comparison of field-deployed radiometers for sea surface skin temperature (SSTskin) retrieval was conducted during two weeks in June 2022. The comparison comprised a laboratory comparison and a field comparison. The field comparison of the radiometers took place on the second week at a seaside pier on the south coast of England. Six thermal infrared radiometers were compared with each other while continuously viewing the closely adjacent surface of the sea from the end of the pier. This paper reports the results of this field comparison. All participants’ radiometers agreed with the reference value, evaluated as the simple mean of the participant-reported values, within the claimed uncertainties. The SSTskin variation during the 5-day period was within 3°C around 18.3°C, which is 2 times as large in range as in the previous comparison in 2016, while the mean of the difference from the reference value over the period evaluated for each participant was found to be within 0.07°C, which is a 2-times improvement on the previous results. During the comparison an insignificant but noticeable abrupt shift in measured value occurred in one of the radiometers, which could not have been detected without comparison with other instruments. This demonstrated the effectiveness of having long-term stable internal reference sources in the instrument, a feature this particular radiometer did not have. The combined results from the laboratory comparison and the field comparison contribute to improve confidence in the retrieved SSTskin.

Restricted access
Falk Feddersen
,
Olavo B. Marques
,
James H. MacMahan
, and
Robert L. Grenzeback

Abstract

Wave spectra and directional moment measurements are of scientific and engineering interest and are routinely estimated with wave buoys. Recently, both fixed-location and Uncrewed Aircraft System (UAS)-mounted lidar have estimated surfzone wave spectra. However, nearshore wave statistics seaward of the surfzone have not been measured with lidar due to low return number and nearshore directional moments have not been measured at all. We use a multi-beam scanning lidar mounted on a gasoline-powered UAS to estimate wave spectra, wave slope spectra, and directional moments on the inner shelf in ≈ 10 m water depth from an 11-min hover and compare to a co-located wave buoy. Lidar returns within circular sampling regions with varying radius R are fit to a plane and a 2D parabola, providing sea-surface and slope timeseries. Wave spectra across the sea-swell (0.04–0.4 Hz) are robustly estimated for R ≥ 0.8 m. Estimating slope spectra is more challenging. Large R works well in the swell band and smaller R work well at higher frequencies, in good agreement with a wave buoy inferred slope spectrum. Directional Fourier coefficients, estimated from wave and slope spectra and cross-spectra, are compared to a wave buoy in the sea-swell band. Larger R and the 2D parabola-fit yield better comparison to the wave buoy. Mean wave angles and directional spreads, functions of the directional Fourier coefficients, are well reproduced at R = 2.4 m and the 2D parabola-fit, within the uncertainties of the wave buoy. The internal consistency of the UAS-lidar-derived results and their good comparison to the Spotter wave buoy demonstrate the effectiveness of this tool for estimating wave statistics.

Restricted access
Scott D. Miller
,
Marc Emond
,
Doug Vandemark
,
Shawn Shellito
,
Jason Covert
,
Ivan Bogoev
, and
Edward Swiatek

Abstract

Eddy covariance (EC) air–sea CO2 flux measurements have been developed for large research vessels, but have yet to be demonstrated for smaller platforms. Our goal was to design and build a complete EC CO2 flux package suitable for unattended operation on a buoy. Published state-of-the-art techniques that have proven effective on research vessels, such as airstream drying and liquid water rejection, were adapted for a 2-m discus buoy with limited power. Fast-response atmospheric CO2 concentration was measured using both an off-the-shelf (“stock”) gas analyzer (EC155, Campbell Scientific, Inc.) and a prototype gas analyzer (“proto”) with reduced motion-induced error that was designed and built in collaboration with an instrument manufacturer. The system was tested on the University of New Hampshire (UNH) air–sea interaction buoy for 18 days in the Gulf of Maine in October 2020. The data demonstrate the overall robustness of the system. Empirical postprocessing techniques previously used on ship-based measurements to address motion sensitivity of CO2 analyzers were generally not effective for the stock sensor. The proto analyzer markedly outperformed the stock unit and did not require ad hoc motion corrections, yet revealed some remaining artifacts to be addressed in future designs. Additional system refinements to further reduce power demands and increase unattended deployment duration are described.

Open access
Erica L. McGrath-Spangler
,
N. C. Privé
,
Bryan M. Karpowicz
,
Isaac Moradi
, and
Andrew K. Heidinger

Abstract

The Geostationary Extended Observations (GeoXO) program plans to include a hyperspectral infrared (IR) sounder on its central satellite, expected to launch in the mid-2030s. As part of the follow-on to the GOES program, the NOAA/NASA GeoXO Sounder (GXS) instrument will join several international counterparts in a geostationary orbit. In preparation, the NASA Global Modeling and Assimilation Office (GMAO) assessed the potential effectiveness of GXS both as a single GEO IR sounder and as part of a global ring that includes international partners. Using a global observing system simulation experiment (OSSE) framework, GXS was assessed from a numerical weather prediction (NWP) perspective. Evaluation of the ability of GXS, both alone and as part of a global ring of GEO sounders, to improve weather prediction of thermodynamic variables was performed globally and regionally. GXS dominated regional analysis and forecast improvements and contributed significantly to global increases in forecast skill relative to a Control. However, more sustained global improvements, on the order of 4 days, relied on international partnerships. Additionally, GXS showed the capability to improve hurricane forecast track errors on the time scales necessary for evacuation warnings. The FSOI metric over CONUS showed that the GXS observations provided the largest radiance impact on the moist energy error norm reduction. The high-temporal-resolution atmospheric profile information over much of the Western Hemisphere from GXS provides an opportunity to improve the representation of weather systems and their forecasts.

Significance Statement

NOAA and NASA are currently planning the GeoXO mission as a follow-on to the GOES program. As part of this process, NASA’s Global Modeling and Assimilation Office has performed several experiments using an observing system simulation experiment (OSSE) framework to assess the potential impact of the GeoXO Sounder (GXS) on numerical weather prediction within the context of international partners launching similar instruments. As part of this assessment, it was found that assimilation of GXS data has the ability to improve both the model analyzed weather and forecasts of the weather, specifically over the domain that GXS observes. Global improvements relied more heavily on a solution consisting of multiple instruments to form a global ring.

Open access