Identification

Title

Ocean surface retracking in tropical cyclones with the KaIA airborne radar altimeter

Abstract

<span style="-webkit-text-stroke-width:0px;background-color:rgb(255, 255, 255);color:rgb(51, 51, 51);display:inline !important;float:none;font-family:"HelveticaNeue Regular", sans-serif;font-size:18px;font-style:normal;font-variant-caps:normal;font-variant-ligatures:normal;font-weight:400;letter-spacing:normal;orphans:2;text-align:start;text-decoration-color:initial;text-decoration-style:initial;text-decoration-thickness:initial;text-indent:0px;text-transform:none;white-space:normal;widows:2;word-spacing:0px;">KaIA is an airborne Ka-band radar altimeter capable of centimetric range resolution and near real-time significant wave height retrievals. Beginning in 2019, KaIA has been installed on National Oceanic and Atmospheric Administration (NOAA) WP-3D Hurricane Hunter aircraft to collect data in Atlantic tropical cyclones during the hurricane season, and extratropical cyclones during the winter storm season. This article details recent retracker algorithm innovations that address specific difficulties with airborne altimetry in extreme weather. Our two most significant contributions to retracker algorithm development are: 1) a higher-order expansion of the classic Brown (1977) altimetry waveform to accommodate off-nadir pointing angles up to 3.25<span class="MathJax" style="-webkit-text-stroke-width:0px;background-color:rgb(255, 255, 255);border-width:0px;box-sizing:border-box;color:rgb(51, 51, 51);direction:ltr;display:inline;float:none;font-family:"HelveticaNeue Regular", sans-serif;font-size-adjust:none;font-size:18px;font-style:normal;font-variant-caps:normal;font-variant-ligatures:normal;font-weight:400;letter-spacing:normal;line-height:normal;margin:0px;max-height:none;max-width:none;min-height:0px;min-width:0px;orphans:2;overflow-wrap:normal;padding:0px;text-align:left;text-decoration-color:initial;text-decoration-style:initial;text-decoration-thickness:initial;text-indent:0px;text-transform:none;white-space:nowrap;widows:2;word-spacing:0px;" id="MathJax-Element-113-Frame" tabindex="0"><nobr style="border-width:0px;box-sizing:border-box;line-height:normal;margin:0px;max-height:none;max-width:none;min-height:0px;min-width:0px;padding:0px;text-decoration:none;transition:none;vertical-align:0px;white-space:nowrap !important;"><span class="math" style="border-width:0px;box-sizing:content-box;display:inline-block;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;width:0.507em;" id="MathJax-Span-2843"><span style="border-width:0px;box-sizing:content-box;display:inline-block;font-size:21.78px;height:0px;line-height:normal;margin:0px;padding:0px;position:relative;text-decoration:none;transition:none;vertical-align:0px;width:0.416em;"><span style="border-width:0px;box-sizing:content-box;clip:rect(1.38em, 1000.42em, 2.344em, -999.998em);display:inline;left:0em;line-height:normal;margin:0px;padding:0px;position:absolute;text-decoration:none;top:-2.202em;transition:none;vertical-align:0px;"><span class="mrow" style="border-width:0px;box-sizing:content-box;display:inline;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2844"><span class="msubsup" style="border-width:0px;box-sizing:content-box;display:inline;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2845"><span style="border-width:0px;box-sizing:content-box;display:inline-block;height:0px;line-height:normal;margin:0px;padding:0px;position:relative;text-decoration:none;transition:none;vertical-align:0px;width:0.416em;"><span style="border-width:0px;box-sizing:content-box;clip:rect(3.859em, 1000em, 4.135em, -999.998em);display:inline;left:0em;line-height:normal;margin:0px;padding:0px;position:absolute;text-decoration:none;top:-3.992em;transition:none;vertical-align:0px;"><span class="texatom" style="border-width:0px;box-sizing:content-box;display:inline;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2846"><span class="mrow" style="border-width:0px;box-sizing:content-box;display:inline;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2847"><span style="border-width:0px;box-sizing:content-box;display:inline-block;height:3.997em;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;width:0px;"><span class="texatom" style="border-width:0px;box-sizing:content-box;display:inline;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2848"><span class="mrow" style="border-width:0px;box-sizing:content-box;display:inline;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2849"><span class="mo" style="border-width:0px;box-sizing:content-box;display:inline;font-family:MathJax_Main;font-size:15.3985px;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;" id="MathJax-Span-2850">∘<span style="border-width:0px;box-sizing:content-box;display:inline-block;height:3.997em;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;width:0px;"><span style="border-width:0px;box-sizing:content-box;display:inline-block;height:2.206em;line-height:normal;margin:0px;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:0px;width:0px;"><span style="border-bottom-style:initial;border-color:initial;border-image:initial;border-left-style:solid;border-right-style:initial;border-top-style:initial;border-width:0px;box-sizing:content-box;display:inline-block;height:0.947em;line-height:normal;margin:0px;overflow:hidden;padding:0px;position:static;text-decoration:none;transition:none;vertical-align:-0.053em;width:0px;"><span style="-webkit-text-stroke-width:0px;background-color:rgb(255, 255, 255);color:rgb(51, 51, 51);display:inline !important;float:none;font-family:"HelveticaNeue Regular", sans-serif;font-size:18px;font-style:normal;font-variant-caps:normal;font-variant-ligatures:normal;font-weight:400;letter-spacing:normal;orphans:2;text-align:start;text-decoration-color:initial;text-decoration-style:initial;text-decoration-thickness:initial;text-indent:0px;text-transform:none;white-space:normal;widows:2;word-spacing:0px;">; 2) a GPS stabilization algorithm to enable along-track averaging while aircraft altitude is changing unpredictably. Comparisons against coincident measurements and modeled data are presented to validate algorithm improvements and document KaIA's performance throughout the 2021-2023 hurricane seasons. We measure less than 0.1 m bias in significant wave height retrievals relative to coincident satellite altimeters.

Resource type

document

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Unique resource identifier

code

https://n2t.net/ark:/85065/d7bk1hrj

codeSpace

Dataset language

eng

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code identifying the spatial reference system

Classification of spatial data and services

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geoscientificInformation

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title

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reference date

date type

publication

effective date

2016-01-01T00:00:00Z

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date type

publication

effective date

2025-02-01T00:00:00Z

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Conformity

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Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Limitations on public access

None

Responsible organisations

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contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

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pointOfContact

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