Atmospheric water vapour is among the most important climate variables (Cess et al., 1990, IPCC-AR4). In particular over oceans, a strong trend in total column water vapour (TCWV) has been observed (Trenberth et al., 2005). TCWV also appears to be a key factor regulating tropical precipitation (Bretherton et al., 2004).

The Microwave Radiometer (MWR) instruments on board the satellites ERS-1, ERS-2, and Envisat have measured TCWV over the ocean during the last 20 years. MWR is a nadir-looking passive microwave radiometer observing in two channels centred at 23.8 GHz and 36.5 GHz and allows for the simultaneous retrieval of TCWV and cloud liquid water path.

The EMiR project aims at better understanding the instrumental characteristics of each MWR instrument in order to improve sensitivity and long-term stability of the whole dataset. Based on a newly derived harmonised brightness temperature time series, an improved TCWV product will be produced.

The knowledge gained through the EMiR  project will provide important guidance for exploiting the next generation MWR instruments flown on-board the Copernicus Sentinel-3 satellite series.

Cited references:

Bretherton, C. S., M. E. Peters, and L. E. Back (2004): Relationships between water vapor path and precipitation over the tropical oceans, J. Clim., 17(7), 1517-1528, DOI: 10.1175/1520-0442(2004)017<1517:RBWVPA>2.0.CO;2.

Cess, R. D., et al. (1990): Intercomparison and interpretation of climate feedback processes in 19 atmospheric general-circulation models, J Geophys Res-Atmos, 95 (D10), 16601-16615, DOI: 10.1029/JD095iD10p16601.

IPCC-AR4 (2007)Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Core Writing Team, Pachauri, R.K. and Reisinger, A. (Eds.), IPCC, Geneva, Switzerland. pp 104.

Trenberth, K. E., J. Fasullo, and L. Smith (2005): Trends and variability in column-integrated atmospheric water vapor. Clim. Dyn., 24, 741-758, DOI: 10.1007/s00382-005-0017-4.

[Last edited: 2018-06-14]