Abstract
Abstract. The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
Highlights
Deep convective systems influence global circulation and the mass exchange between the troposphere and stratosphere (Fueglistaler et al, 2009), and they have been recognized as a crucial process for the understanding of the climate changes
The past and ongoing GPS Radio Occultation (RO) missions, Global Positioning System/Meteorology (GPS/MET) satellite (Rocken et al, 1997), the CHAllenging Minisatellite Payload (CHAMP) satellite (Wickert et al, 2001), the Satellite de Aplicaciones Cientificas-C (SAC-C) satellite (Hajj et al, 2004), the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) six-satellite constellation (Anthes et al, 2008), and the Gravity Recovery And Climate Experiment (GRACE) twin satellites (Beyerle et al, 2005), have a denser number of measurements at mid and high latitude due to the inclination of the orbits, but they do not provide a good coverage of the tropical area (Fig. 1)
Our results show that the bending angle from the GPS RO signal contains interesting information on the tropopause during tropical cyclones (TCs)
Summary
Deep convective systems influence global circulation and the mass exchange between the troposphere and stratosphere (Fueglistaler et al, 2009), and they have been recognized as a crucial process for the understanding of the climate changes. Temperature and water vapour variation in the upper troposphere and lower stratosphere (UTLS) are closely connected to the convection (Danielsen, 1982; Sherwood et al, 2003; Chae et al, 2011) but the difficulty to measure those parameters at such altitudes, with high vertical resolution and sensitivity still raises many questions on their behaviour (Forster and Shine, 1999). The tropical cyclones (TCs) are severe weather events often leading to deep convective activity and persisting for long time. They alter the physics and chemistry of the TTL and they play a fundamental role on the atmospheric circulation and troposphere-stratosphere exchange (Ray and Rosenlof, 2007; Cairo et al, 2008; Fueglistaler et al, 2009; Romps and Kuang, 2009). A new advanced GPS receiver is planned to be launched in the near future on board of the International Space Station (ISS) as part of the Atomic Clock Ensemble in Space
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