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Gary A. Wick, Terrence F. Hock, Paul J. Neiman, Holger Vömel, Michael L. Black, and J. Ryan Spackman

1. Introduction Detailed measurements of the kinematic and thermodynamic structure of the atmosphere are important for numerical weather prediction (NWP) and physical process studies. While satelliteborne microwave and infrared sounders retrieve global thermodynamic profiles at relatively coarse vertical resolution, radiosondes and dropsondes (also called dropwindsondes) provide high-quality high-vertical-resolution in situ measurements of atmospheric wind, temperature, and relative humidity

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William A. Komaromi and James D. Doyle

1. Introduction Until recently, a single ER-2 flight over Hurricane Erin (2001) provided the only direct dropsonde observations through the full depth of the tropical cyclone (TC) outflow layer ( Halverson et al. 2006 ). Conventional aircraft observations of TCs, such as by the U.S. Air Force C-130s and the NOAA P-3s, tend to be limited to the middle to lower levels of the cyclone with a typical flight level of 700 hPa ( Aberson et al. 2006 ). Synoptic observations provided by the NOAA G-IV are

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Sandrine Bony and Bjorn Stevens

stratocumulus—and only at the level of the aircraft. Though not well suited to characterizing the vertical profile of divergence, these measurements raise the question if, by measuring the vertical profile of the horizontal wind using dropsondes launched from an aircraft, one could estimate the vertical profile of large-scale mass divergence. Presuming that it is possible in principle, the important practical question then becomes how many sondes would be required to get an estimate of the divergence that

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Florian Harnisch and Martin Weissmann

1. Introduction Tropical cyclones (TCs) usually develop over data-sparse regions of the tropical oceans. The limited number of observations and the rapid development of TCs increases uncertainties of the model analysis in these regions, which can lead to significant forecast errors ( Langland 2005 ). Surveillance programs deploying dropsonde observations in and around TCs have been operated for the Atlantic ( Burpee et al. 1996 ; Aberson 2002 ) and the western North Pacific basin ( Wu et al

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T. Connor Nelson, Lee Harrison, and Kristen L. Corbosiero

1. Introduction The Office of Naval Research conducted the Tropical Cyclone Intensity (TCI) experiment in 2015 ( Doyle et al. 2017 ). Three of the tropical cyclones (TCs) that were sampled during TCI are Marty (27–28 September), Joaquin (2–5 October), and Patricia (20–23 October). A total of 725 global positioning system (GPS) dropwindsondes (hereinafter referred to as “dropsondes”) were launched into these three TCs. The dropsondes used were the Expendable Digital Dropsondes (XDDs

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Jonathan Zawislak and Edward J. Zipser

) involved consecutive and coordinated aircraft missions. Participating dropsonde-equipped aircraft include the NASA DC-8 (GRIP), NCAR/NSF G-V (PREDICT), NOAA P-3s and G-IV, and U.S. Air Force (USAF) C-130s. Collaborative investigations during PGI include the rapid intensification and mature stages of Hurricane Earl, the nonredevelopment of Tropical Storm Gaston, the genesis of Tropical Storm Matthew, and perhaps most impressive, the entire life cycle of Hurricane Karl starting 4 days before genesis, to

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William A. Komaromi

strength of this dataset comes not only from the unprecedented quantity of developing and nondeveloping tropical waves sampled, but also from the temporally evolving nature of data associated with distinct pouches. Two recent papers, Smith and Montgomery (2011) and Davis and Ahijevych (2012) , examined PREDICT dropsonde data for Tropical Storm (TS) Matthew, Hurricane Karl, and ex-TS Gaston. Smith and Montgomery (2011) found lower values of equivalent potential temperature between the surface and 3

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Daniel P. Stern and George H. Bryan

. Recently, Stern et al. (2016 , hereafter S16) presented a comprehensive dataset of extreme updrafts and wind speeds sampled by GPS dropsondes (hereafter, “sonde” is used interchangeably with “dropsonde”) in the lower troposphere (0–3 km) within tropical cyclones. S16 found that updrafts exceeding 10 m s −1 are quite common within category 4 and 5 TCs and are nearly exclusively found within the eyewall, just inward of the radius of maximum winds (RMW). Importantly, a substantial fraction of the

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T. Connor Nelson, Lee Harrison, and Kristen L. Corbosiero

1. Introduction The introduction of the high-definition sounding system (HDSS) and its expendable digital dropsondes (XDDs) has increased the spatial resolution of global positioning system (GPS) dropwindsondes (hereafter, referred to as “dropsondes” or “sondes”) in tropical cyclones (TCs; Black et al. 2017 ). The HDSS can launch sondes as frequently as once every 10 s and the telemetry capacity allows for the data acquisition of as many as 40 sondes simultaneously. The HDSS/XDD system used

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Martin Weissmann, Florian Harnisch, Chun-Chieh Wu, Po-Hsiung Lin, Yoichiro Ohta, Koji Yamashita, Yeon-Hee Kim, Eun-Hee Jeon, Tetsuo Nakazawa, and Sim Aberson

:// ). A substantial part of these improvements is likely due to advanced numerical models, increased resolution, advanced data assimilation, and the steady increase of satellite observations assimilated in different models. Targeted airborne dropsonde observations are another factor that has contributed to improvements of TC track forecasts. Several studies documented that average track forecast improvements of the order of 10%–30% can be achieved with additional airborne dropsonde observations

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