Remedy 4: Reference-quality dielectric constant measurements of pure and saline water for the frequency range 1 – 200 GHz

Primary gap remedy type: 
Proposed remedy description: 

Ocean emissivity models rely on accurate measurements of the dielectric constant of water and seawater for a range of temperatures and frequencies. However, there are inconsistencies between measurements available in the literature (Lawrence et al 2017) and none have SI-traceable uncertainties. Measurements should be taken that are reference quality, i.e. SI-traceable and with validated uncertainty estimates. The uncertainties should include a calculation of the correlation between measurements of the real and imaginary components of the dielectric constant, so that the uncertainties can be properly transformed into radiance space. As well as ocean emissivity, this would also support dielectric constant models for cloud radiative transfer (e.g. the dielectric constant of super-cooled liquid water).


This will support a reference ocean emissivity model, allowing for cal/val of microwave imagers and surface sensitive channels of microwave sounders to reference standards.

Measurable outcome of success: 

Documented and freely available measurements of the dielectric constant of seawater and pure water for a range of frequencies (1 200 GHz) and temperatures (-5 to +35 °C) with traceable uncertainty estimates

Expected viability for the outcome of success: 
  • Medium
Scale of work: 
  • Other, please specify:
PhD or post-doctoral student
Time bound to remedy: 
  • Less than 5 years
Indicative cost estimate (investment): 
  • Medium cost (< 5 million)
Indicative cost estimate (exploitation): 
  • No
Potential actors: 
  • National funding agencies
  • Academia, individual research institutes