New Ocean Winds Satellite Mission to Probe Hurricanes and Tropical Convection

Abstract

The Cyclone Global Navigation Satellite System (CYGNSS) is a new NASA earth science mission scheduled to be launched in 2016 that focuses on tropical cyclones (TCs) and tropical convection. The mission’s two primary objectives are the measurement of ocean surface wind speed with sufficient temporal resolution to resolve short-time-scale processes such as the rapid intensification phase of TC development and the ability of the surface measurements to penetrate through the extremely high precipitation rates typically encountered in the TC inner core. The mission’s goal is to support significant improvements in our ability to forecast TC track, intensity, and storm surge through better observations and, ultimately, better understanding of inner-core processes. CYGNSS meets its temporal sampling objective by deploying a constellation of eight satellites. Its ability to see through heavy precipitation is enabled by its operation as a bistatic radar using low-frequency GPS signals. The mission will deploy an eight-spacecraft constellation in a low-inclination (35°) circular orbit to maximize coverage and sampling in the tropics. Each CYGNSS spacecraft carries a four-channel radar receiver that measures GPS navigation signals scattered by the ocean surface. The mission will measure inner-core surface winds with high temporal resolution and spatial coverage, under all precipitating conditions, and over the full dynamic range of TC wind speeds.

Spatiotemporal Evaluation of GNSS-R Based on Future Fully Operational Global Multi-GNSS and Eight-LEO Constellations

“…Therefore, to ensure that our work is both feasible and meaningful, the main orbit parameters used for the GNSS-R LEO constellation are the same as those of CYGNSS. All the microsatellites are in repeated ground track orbits with 13 day periods, and an inclination of 35 • was selected to ensure coverage of most of the areas in which cyclones and typhoons occur [24]. In addition, the orbit altitudes are approximately 500 km to ensure that the GNSS reflected signals have sufficient power.…”

“…In recent years, some researchers have begun to consider the spatial and temporal resolutions of GNSS-R anew because of the NASA (National Aeronautics and Space Administration) mission called the Cyclone Global Navigation Satellite System (CYGNSS). At the end of 2016, NASA launched the CYGNSS mission, which used eight micro-satellites; each individual observatory can track up to four parallel reflected GPS L1 signals [24]. The medium and mean revisit times for CYGNSS missions were computed using an empirical distribution.…”

“…The results showed that the median time is 2.8 h and the mean revisit time is 7.2 h when calculated across the entire 13-day cycle. Zavorotny et al [31] showed that the mean revisit time over the equatorial regions with an approximate latitude range of ±38 • is approximately 5 h, but they may have adopted a different strategy from that of Ruf et al [24]. In addition, Zavorotny et al [31] performed a coverage and revisit time simulation for a possible GNSS-R constellation consisting of 24 polar orbiting satellites, with each of these satellites tracking up to 10 parallel reflections from both GPS and Galileo satellites.…”

On the Predictability and Error Sources of Tropical Cyclone Intensity Forecasts

“…Within the community of scientists working on tropical cyclones, efforts have been directed toward improving dedicated tropical cyclone models (e.g., Gopalakrishnan et al 2011), real-time in situ and remote sensing observations of storms (e.g., Ruf et al 2016), assimilation of those observations into models (Zhang and Weng 2015;Weng and Zhang 2016;Zhang et al 2016), and statistical forecast models, which are still competitive with deterministic models (Kaplan et al 2015). Numerical modeling of tropical cyclones is especially challenging owing to the very high resolution required to resolve the critical eyewall region (Rotunno et al 2009), to the complex physics of boundary layers and air-sea interaction at high winds speeds (Nolan et al 2009;Green and Zhang 2014;Andreas et al 2015;Green and Zhang 2015), and to the importance of correctly modeling the response of the upper ocean to the storms (Moon et al 2007;Yablonsky and Ginis 2009).…”

Apport de la télédétection spatiale à la représentation des champs de vents cycloniques

“…C'est donc assez naturellement qu'on en vient à se demander si ces données ne pourraient pas être aussi utilisées pour améliorer les modèles de vent paramétriques, et donc les résultats des études d'aléas cycloniques. Dans cette étude, nous nous intéresserons plus particulièrement à la mission CYGNSS de la NASA, spécifiquement conçue pour estimer les vents de surface en condition cyclonique, avec une couverture spatiale et temporelle inégalée (plusieurs passages par jour au dessus d'une même zone dans la bande intertropicale, RUF et al, 2016). (HU et al, 2012).…”