Small Scale Variability in the Wet Troposphere Impacts the Interpretation of SWOT Satellite Observations

The Surface Water and Ocean Topography (SWOT) mission offers new insights into submesoscale ocean processes. Realizing this requires careful consideration of other geophysical signals such as the signal delay induced by water vapor in the troposphere. Over short spatial scales (<∼80 km), this signal is not well-captured by radiometer observations. Here we investigate the wet troposphere in Australian coastal regions during SWOT's 3-month calibration phase. Using a high-resolution atmospheric model and a novel in situ array of GNSS observations, we find the SWOT error budget for wet troposphere is regularly exceeded, with signal magnitudes up to double the error budget at small scales. We also find centimeter level biases in radiometer derived delays within ∼50 km of the coast. We suggest that, given the low radar noise and high resolution of SWOT KaRIn observations, wet troposphere errors can bias geophysical interpretation and hence have increased significance for ocean topography.