Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Hurricane Florence was the sixth named storm in the Atlantic hurricane season 2018. It caused dozens of deaths and major economic damage. In this study, we present in situ observations of trace gases within tropical storm Florence on 2 September 2018, after it had developed a rotating nature, and of a tropical wave observed close to the African continent on 29 August 2018 as part of the research campaign CAFE Africa (Chemistry of the Atmosphere: Field Experiment in Africa) with HALO (High Altitude and LOng Range Research Aircraft). We show the impact of deep convection on atmospheric composition by measurements of the trace gases nitric oxide (NO), ozone (O<span class="inline-formula"><sub>3</sub></span>), carbon monoxide (CO), hydrogen peroxide (H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>2</sub></span>), dimethyl sulfide (DMS) and methyl iodide (CH<span class="inline-formula"><sub>3</sub></span>I) and by the help of color-enhanced infrared satellite imagery taken by GOES-16. While both systems, i.e., the tropical wave and the tropical storm, are deeply convective, we only find evidence for lightning in the tropical wave using both in situ NO measurements and data from the World Wide Lightning Location Network (WWLLN).

Highlights

  • Tropical cyclones are low-pressure systems evolving over warm tropical waters usually close to the equator (± 20◦) - an area which is referred to as the Intertropical Convergence Zone (ITCZ) (Frank and Roundy, 2006; Deutscher Wetterdienst)

  • We show the impact of deep convection on atmospheric composition by measurements of the trace gases nitric oxide (NO), ozone (O3), carbon monoxide (CO), hydrogen peroxide (H2O2), dimethyl sulfide (DMS) and methyl iodide (CH3I), and by the help of color enhanced infrared satellite imagery taken by GOES-16

  • We have presented in situ observations of a tropical cyclone which developed into hurricane Florence during the Atlantic hurricane season 2018

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Summary

Introduction

Tropical cyclones are low-pressure systems evolving over warm tropical waters usually close to the equator (± 20◦) - an area which is referred to as the Intertropical Convergence Zone (ITCZ) (Frank and Roundy, 2006; Deutscher Wetterdienst). A tropical cyclone formed over the Atlantic Ocean - most often west of the African continent - with a maximum wind speed of 64 knots (118 km/h) and higher is defined as a hurricane according to the Beaufort scale. Zipser reported significantly reduced lightning activity over tropical oceans despite heavy rainfall from convective clouds in comparison to tropical continental and coastal areas with similar rainfall based on shipborn observations during the Global Atmospheric Research Program Atlantic Tropical Experiment in 40 1974 (GATE) (Zipser, 1994). Data from in situ measurements are sparse and to our knowledge, the in situ aircraft observation of deep convection in tropical cyclones accompanied by and in 80 the absence of lightning depending on the stage of development has not been reported before. The data are examined for evidence of deep convection and lightning activity

Observations
Cloud Top
Trace gas measurements
Deep convection
Lightning
Conclusions
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