Sensing small-scale structures in the troposphere with tomographic principles (IAG working group)

Abstract

<p>Within the International Association of Geodesy (IAG), a new working group was formed with the intention to bring together researchers and professionals working on tomography-based concepts for sensing the neutral atmosphere with space-geodetic techniques. Hereby the focus lies on Global Navigation Satellite Systems (GNSS) but also on complementary observation techniques, like Interferometric Synthetic Aperature Radar (InSAR) or microwave radiometers, sensitive to the water vapor distribution in the lower atmosphere.</p><p>In the next four years (2019-2023), we will address current challenges in tropospheric tomography with focus on ground-based and space-based measurements, the combination of measurement techniques and the design of new observation concepts using tomographic principles. While geodetic GNSS networks are nowadays the backbone for troposphere tomography studies, further local densifications, e.g. at airports, cities or fundamental stations are necessary to achieve very fine spatial and temporal resolution. Besides, the combination of ground-based GNSS with other microwave techniques like radio occultation or InSAR seems to be beneficial due their complementary nature. Therefore, several further developments in the field of tropospheric tomography are required. This includes more dynamical tomography models - adaptable to varying input data, advanced ray-tracing algorithms for the reconstruction of space-based observations and the coordination of a benchmark campaign.</p><p>In this presentation, we will give an overview about the current challenges in tropospheric tomography and the objectives of working group. The latter will also include standards for data exchange and therefore, make tomographic products available for the assimilation into numerical weather prediction models but also for various other disciplines, which rely on accurate wet refractivities or derived products like tropospheric signal delays.</p>

50 anos de sinergia entre Geodésia Espacial e Meteorologia: do erro no posicionamento GNSS a aplicações de previsão de precipitação de curtíssimo prazo

“…Tratando adequadamente as limitações, a tomografia-GNSS é uma ferramenta promissora na detecção da alta variabilidade espaço-temporal do vapor d'água. Diferentes trabalhos atuais apresentam as melhorias quanto à técnica: Bender et al (2011), Brenot et al (2020), Zhang et al (2020) e Moeller et al (2020). No Brasil, tais estudos ainda não foram desenvolvidos.…”

“…Um estudo recente propõe o uso de receptores GNSS para prever (com antecedência de 30 minutos) eventos extremos de precipitação (>35mm) (SAPUCCI et al, 2019) e há projetos visando explorar dados do COSMIC-2 (constelação de satélites equatoriais dedicados para RO-GNSS) para prever eventos extremos de precipitação (BANOS et al, 2018). Um desenvolvimento em paralelo vem sendo a tomografia do vapor d'água (BRENOT et al, 2020), com potencial de melhor detalhar a distribuição temporal e espacial dessa variável (MOELLER et al, 2020). É consenso que previsão de tempo em condições atmosféricas extremas (severas) é desafiadora e encontra-se na fronteira do conhecimento humano, no qual a sinergia em diferentes áreas do conhecimento é um dos ingredientes mais importantes para se obter o sucesso.…”

GNSS signal ray-tracing algorithm for the simulation of satellite-to-satellite excess phase in the neutral atmosphere

“…Hence, for ground-based GNSS tomography, the transmitter-receiver geometry does not favor the high vertical resolution and leads to solution instability (Trzcina and Rohm 2019;Liu et al 2019). Conversely, Moeller et al (2019) has shown that a tomographic "peeling" approach with space-based observations can significantly increase the vertical resolution if applied to radio occultation measurements. The scanning rays, in our solution, will come from ground-and space-based GNSS observations.…”