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Jun A. Zhang, Joseph J. Cione, Evan A. Kalina, Eric W. Uhlhorn, Terry Hock, and Jeffrey A. Smith

Abstract

This study highlights infrared sensor technology incorporated into the global positioning system (GPS) dropsonde platforms to obtain sea surface temperature (SST) measurements. This modified sonde (IRsonde) is used to improve understanding of air–sea interaction in tropical cyclones (TCs). As part of the Sandy Supplemental Program, IRsondes were constructed and then deployed during the 2014 hurricane season. Comparisons between SSTs measured by collocated IRsondes and ocean expendables show good agreement, especially in regions with no rain contamination. Surface fluxes were estimated using measurements from the IRsondes and AXBTs via a bulk method that requires measurements of SST and near-surface (10 m) wind speed, temperature, and humidity. The evolution of surface fluxes and their role in the intensification and weakening of Hurricane Edouard (2014) are discussed in the context of boundary layer recovery. The study’s result emphasizes the important role of surface flux–induced boundary layer recovery in regulating the low-level thermodynamic structure that is tied to the asymmetry of convection and TC intensity change.

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Philippe Drobinski, Fatima Karbou, Peter Bauer, Philippe Cocquerez, Christophe Lavaysse, Terry Hock, David Parsons, Florence Rabier, Jean-Luc Redelsperger, and Stéphanie Vénel

Abstract

During the international African Monsoon Multidisciplinary Analysis (AMMA) project, stratospheric balloons carrying gondolas called driftsondes capable of dropping meteorological sondes were deployed over West Africa and the tropical Atlantic Ocean. The goals of the deployment were to test the technology and to study the African easterly waves, which are often the forerunners of hurricanes. Between 29 August and 22 September 2006, 124 sondes were dropped over the seven easterly waves that moved across Africa into the Atlantic between about 10° and 20°N, where almost no in situ vertical information exists. Conditions included waves that developed into Tropical Storm Florence and Hurricanes Gordon and Helene. In this study, a selection of numerical weather prediction model outputs has been compared with the dropsondes to assess the effect of some developments in data assimilation on the quality of analyses and forecasts. By comparing two different versions of the Action de Recherche Petite Echelle Grande Echelle (ARPEGE) model of Météo-France with the dropsondes, first the benefits of the last data assimilation updates are quantified. Then comparisons are carried out using the ARPEGE model and the Integrated Forecast System (IFS) model of the European Centre for Medium-Range Weather Forecasts. It is shown that the two models represent very well the vertical structure of temperature and humidity over both land and sea, and particularly within the Saharan air layer, which displays humidity below 5%–10%. Conversely, the models are less able to represent the vertical structure of the meridional wind. This problem seems to be common to ARPEGE and IFS, and its understanding still requires further investigations.

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Junhong (June) Wang, Kate Young, Terry Hock, Dean Lauritsen, Dalton Behringer, Michael Black, Peter G. Black, James Franklin, Jeff Halverson, John Molinari, Leon Nguyen, Tony Reale, Jeff Smith, Bomin Sun, Qing Wang, and Jun A. Zhang

Abstract

A GPS dropsonde is a scientific instrument deployed from research and operational aircraft that descends through the atmosphere by a parachute. The dropsonde provides high-quality, high-vertical-resolution profiles of atmospheric pressure, temperature, relative humidity, wind speed, and direction from the aircraft flight level to the surface over oceans and remote areas. Since 1996, GPS dropsondes have been routinely dropped during hurricane reconnaissance and surveillance flights to help predict hurricane track and intensity. From 1996 to 2012, NOAA has dropped 13,681 dropsondes inside hurricane eye walls or in the surrounding environment for 120 tropical cyclones (TCs). All NOAA dropsonde data have been collected, reformatted to one format, and consistently and carefully quality controlled using state-of-the-art quality-control (QC) tools. Three value-added products, the vertical air velocity and the radius and azimuth angle of each dropsonde location, are generated and added to the dataset. As a result, a long-term (1996–2012), high-quality, high-vertical-resolution (∼5–15 m) GPS dropsonde dataset is created and made readily available for public access. The dropsonde data collected during hurricane reconnaissance and surveillance flights have improved TC-track and TC-intensity forecasts significantly. The impact of dropsonde data on hurricane studies is summarized. The scientific applications of this long-term dropsonde dataset are highlighted, including characterizing TC structures, studying TC environmental interactions, identifying surface-based ducts in the hurricane environment that affect electromagnetic wave propagation, and validating satellite temperature and humidity profiling products.

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Florence Rabier, Aurélie Bouchard, Eric Brun, Alexis Doerenbecher, Stéphanie Guedj, Vincent Guidard, Fatima Karbou, Vincent-Henri Peuch, Laaziz El Amraoui, Dominique Puech, Christophe Genthon, Ghislain Picard, Michael Town, Albert Hertzog, François Vial, Philippe Cocquerez, Stephen A. Cohn, Terry Hock, Jack Fox, Hal Cole, David Parsons, Jordan Powers, Keith Romberg, Joseph VanAndel, Terry Deshler, Jennifer Mercer, Jennifer S. Haase, Linnea Avallone, Lars Kalnajs, C. Roberto Mechoso, Andrew Tangborn, Andrea Pellegrini, Yves Frenot, Jean-Noël Thépaut, Anthony McNally, Gianpaolo Balsamo, and Peter Steinle

The Concordiasi project is making innovative observations of the atmosphere above Antarctica. The most important goals of the Concordiasi are as follows:

  • To enhance the accuracy of weather prediction and climate records in Antarctica through the assimilation of in situ and satellite data, with an emphasis on data provided by hyperspectral infrared sounders. The focus is on clouds, precipitation, and the mass budget of the ice sheets. The improvements in dynamical model analyses and forecasts will be used in chemical-transport models that describe the links between the polar vortex dynamics and ozone depletion, and to advance the under understanding of the Earth system by examining the interactions between Antarctica and lower latitudes.
  • To improve our understanding of microphysical and dynamical processes controlling the polar ozone, by providing the first quasi-Lagrangian observations of stratospheric ozone and particles, in addition to an improved characterization of the 3D polar vortex dynamics. Techniques for assimilating these Lagrangian observations are being developed.

A major Concordiasi component is a field experiment during the austral springs of 2008–10. The field activities in 2010 are based on a constellation of up to 18 long-duration stratospheric super-pressure balloons (SPBs) deployed from the McMurdo station. Six of these balloons will carry GPS receivers and in situ instruments measuring temperature, pressure, ozone, and particles. Twelve of the balloons will release dropsondes on demand for measuring atmospheric parameters. Lastly, radiosounding measurements are collected at various sites, including the Concordia station.

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Florence Rabier, Steve Cohn, Philippe Cocquerez, Albert Hertzog, Linnea Avallone, Terry Deshler, Jennifer Haase, Terry Hock, Alexis Doerenbecher, Junhong Wang, Vincent Guidard, Jean-Noël Thépaut, Rolf Langland, Andrew Tangborn, Gianpaolo Balsamo, Eric Brun, David Parsons, Jérôme Bordereau, Carla Cardinali, François Danis, Jean-Pierre Escarnot, Nadia Fourrié, Ron Gelaro, Christophe Genthon, Kayo Ide, Lars Kalnajs, Charlie Martin, Louis-François Meunier, Jean-Marc Nicot, Tuuli Perttula, Nicholas Potts, Patrick Ragazzo, David Richardson, Sergio Sosa-Sesma, and André Vargas
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Joseph J. Cione, George H. Bryan, Ronald Dobosy, Jun A. Zhang, Gijs de Boer, Altug Aksoy, Joshua B. Wadler, Evan A. Kalina, Brittany A. Dahl, Kelly Ryan, Jonathan Neuhaus, Ed Dumas, Frank D. Marks, Aaron M. Farber, Terry Hock, and Xiaomin Chen

Abstract

Unique data from seven flights of the Coyote small unmanned aircraft system (sUAS) were collected in Hurricanes Maria (2017) and Michael (2018). Using NOAA’s P-3 reconnaissance aircraft as a deployment vehicle, the sUAS collected high-frequency (>1 Hz) measurements in the turbulent boundary layer of hurricane eyewalls, including measurements of wind speed, wind direction, pressure, temperature, moisture, and sea surface temperature, which are valuable for advancing knowledge of hurricane structure and the process of hurricane intensification. This study presents an overview of the sUAS system and preliminary analyses that were enabled by these unique data. Among the most notable results are measurements of turbulence kinetic energy and momentum flux for the first time at low levels (<150 m) in a hurricane eyewall. At higher altitudes and lower wind speeds, where data were collected from previous flights of the NOAA P-3, the Coyote sUAS momentum flux values are encouragingly similar, thus demonstrating the ability of an sUAS to measure important turbulence properties in hurricane boundary layers. Analyses from a large-eddy simulation (LES) are used to place the Coyote measurements into context of the complicated high-wind eyewall region. Thermodynamic data are also used to evaluate the operational HWRF model, showing a cool, dry, and thermodynamically unstable bias near the surface. Preliminary data assimilation experiments also show how sUAS data can be used to improve analyses of storm structure. These results highlight the potential of sUAS operations in hurricanes and suggest opportunities for future work using these promising new observing platforms.

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Stephen A. Cohn, Terry Hock, Philippe Cocquerez, Junhong Wang, Florence Rabier, David Parsons, Patrick Harr, Chun-Chieh Wu, Philippe Drobinski, Fatima Karbou, Stéphanie Vénel, André Vargas, Nadia Fourrié, Nathalie Saint-Ramond, Vincent Guidard, Alexis Doerenbecher, Huang-Hsiung Hsu, Po-Hsiung Lin, Ming-Dah Chou, Jean-Luc Redelsperger, Charlie Martin, Jack Fox, Nick Potts, Kathryn Young, and Hal Cole

Constellations of driftsonde systems— gondolas floating in the stratosphere and able to release dropsondes upon command— have so far been used in three major field experiments from 2006 through 2010. With them, high-quality, high-resolution, in situ atmospheric profiles were made over extended periods in regions that are otherwise very difficult to observe. The measurements have unique value for verifying and evaluating numerical weather prediction models and global data assimilation systems; they can be a valuable resource to validate data from remote sensing instruments, especially on satellites, but also airborne or ground-based remote sensors. These applications for models and remote sensors result in a powerful combination for improving data assimilation systems. Driftsondes also can support process studies in otherwise difficult locations—for example, to study factors that control the development or decay of a tropical disturbance, or to investigate the lower boundary layer over the interior Antarctic continent. The driftsonde system is now a mature and robust observing system that can be combined with flight-level data to conduct multidisciplinary research at heights well above that reached by current research aircraft. In this article we describe the development and capabilities of the driftsonde system, the exemplary science resulting from its use to date, and some future applications.

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Morris L. Weisman, Robert J. Trapp, Glen S. Romine, Chris Davis, Ryan Torn, Michael Baldwin, Lance Bosart, John Brown, Michael Coniglio, David Dowell, A. Clark Evans, Thomas J. Galarneau Jr., Julie Haggerty, Terry Hock, Kevin Manning, Paul Roebber, Pavel Romashkin, Russ Schumacher, Craig S. Schwartz, Ryan Sobash, David Stensrud, and Stanley B. Trier

Abstract

The Mesoscale Predictability Experiment (MPEX) was conducted from 15 May to 15 June 2013 in the central United States. MPEX was motivated by the basic question of whether experimental, subsynoptic observations can extend convective-scale predictability and otherwise enhance skill in short-term regional numerical weather prediction.

Observational tools for MPEX included the National Science Foundation (NSF)–National Center for Atmospheric Research (NCAR) Gulfstream V aircraft (GV), which featured the Airborne Vertical Atmospheric Profiling System mini-dropsonde system and a microwave temperature-profiling (MTP) system as well as several ground-based mobile upsonde systems. Basic operations involved two missions per day: an early morning mission with the GV, well upstream of anticipated convective storms, and an afternoon and early evening mission with the mobile sounding units to sample the initiation and upscale feedbacks of the convection.

A total of 18 intensive observing periods (IOPs) were completed during the field phase, representing a wide spectrum of synoptic regimes and convective events, including several major severe weather and/or tornado outbreak days. The novel observational strategy employed during MPEX is documented herein, as is the unique role of the ensemble modeling efforts—which included an ensemble sensitivity analysis—to both guide the observational strategies and help address the potential impacts of such enhanced observations on short-term convective forecasting. Preliminary results of retrospective data assimilation experiments are discussed, as are data analyses showing upscale convective feedbacks.

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Greg M. McFarquhar, Elizabeth Smith, Elizabeth A. Pillar-Little, Keith Brewster, Phillip B. Chilson, Temple R. Lee, Sean Waugh, Nusrat Yussouf, Xuguang Wang, Ming Xue, Gijs de Boer, Jeremy A. Gibbs, Chris Fiebrich, Bruce Baker, Jerry Brotzge, Frederick Carr, Hui Christophersen, Martin Fengler, Philip Hall, Terry Hock, Adam Houston, Robert Huck, Jamey Jacob, Robert Palmer, Patricia K. Quinn, Melissa Wagner, Yan (Rockee) Zhang, and Darren Hawk
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