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JWG C.7: Ground-GNSS trends for climate models

Chair: Marcelo Santos (Canada)
Vice chair: Rosa Pacione (Italy)
Affiliations: Commission 4, IGS, IVS, GGOS

Introduction

GNSS Zenith Total Delay (ZTD) estimates are quantities of great interest by climate modellers since atmospheric water vapour is the major greenhouse gas. Therefore, the importance of its accurate, long-term monitoring and evaluation of trends and variability, potentially serving as independent benchmarks to climatological models, both on longer trends derived from GNSS, but also shorter trends, which could be used for assimilation and validation of climate models. ZTD estimates are determined on a regular basis by several processing centers as well as by demand. It has also beendemonstrated that series of ZTD estimates can be used for quality control purposes. At the same time, GNSS is reaching the “maturity age” of 30 years when climate normals of ZTD and gradients can be derived. But what would be the best ZTD series to serve the climate community? What series would offer the most realistic trends? A variety of data sets have been used, namely, the ZTD series derived by the third reprocessing campaign (REPRO3), based on a variety of processing modes and models. PPP-based ZTD estimates can also be generated by scientific software suites, including the PPP-derived IGS product. All of that converges to the opportunity to perform quality control and assess ZTD (and gradient) product best suited to climate studies.

Objectives

The main objective is to define proper quality parameters to satisfy the generation and analysis of long-term trends derived from ground GNSS and inter-annual variation. Proposed activities involve the generation of ZTD estimates using PPP by a few centers (e.g., ESA, GFZ, IGS, UNB) and the tropospheric product from IGS, all based on REPRO3, analysis of trend and harmonics and comparisons with results from the past JWG investigation based on IGS AC estimates.

Program of Activities

  • Collaborate with IGS and IVS in the forthcoming reprocessing campaign.
  • Participate actively in IAG, AGU and EGU conferences and organize sessions.
  • Organize working group meetings, splinter group meetings at the said symposia..

Members

  • Anna Kloss (Poland)
  • Galina Dick (Germany)
  • Haroldo Marques (Brazil)
  • Jonathan Jones (UK)
  • Kalev Rannat (Estonia)
  • Kyriakos Balidakis (Germany)
  • Mayra Oyola-Merced (US)
  • Olalekan Isioye (South Africa)
  • Peng Yuan (Germany)
  • Raul Valenzuela (Chile)
  • Samuel Nahmani (France)
  • Sharyl Byram (US)
  • Thalia Nikolaidou (Canada)
  • Yibin Yao (China)
  • Yidong Lou (China)