Global measurements of Sea Surface Temperature using the Infrared Atmospheric Sounding Interferometer

Global measurements of Sea Surface Temperature using the Infrared Atmospheric Sounding Interferometer

Global Sea Surface Temperature (SST) is an important parameter in weather  forecasting and climate monitoring. The remote sensing principle is simple:
measuring the radiance emitted by the sea surface in an infrared atmospheric  window region.  The difficulty is in obtaining a useful accuracy of a few tenths  of Kelvin, which imposes strict requirements on radiometric calibration and  radiative transfer modelling.

Starting in 1991 there has been a series of satellite instruments specifically  designed to provide accurate SST measurements. These are well-calibrated  broad-band radiometers with approx 1km spatial resolution. However, since the  demise of AATSR (on Envisat) in April 2012 and the launch of SLSTR (on Sentinel  3) in February 2016 there has been a 4-year gap during which SST measurements  have been obtained from the less well-calibrated AVHRR instruments on the NOAA  and MetOp satellites.

The aim of this project is to derive SST data from the IASI instruments which  have been operating on the the MetOp satellites since 2006.  IASI is an infrared  fourier transform spectrometer, with high spectral resolution (0.5cm-1) but  relatively low spatial resolution (12km). Measuring the full spectrum not only  allows the synthesis of the broadband radiometer channels of the other  instruments but also resolves atmospheric absorption features (primarily H2O and  CO2) which should lead to more sophisticated techniques for correcting for atmospheric effects.

The envisaged tasks are as follows  a) Use IASI to simulate measurements from the AVHRR instrument (on the same  MetOp) platform to establish an improved radiometric calibration for AVHRR.  b) Use IASI to simulate AATSR and SLSTR channels to provide a transfer standard  across the 4-year gap  c) Develop an IASI-specific SST retrieval algorithm utilising the full spectral  resolution

The CASE partner for the project is the UK Met Office, and the co-supervisor  will be Roger Saunders, head of the Satellite Applications group.  While at the Met Office the main scientific task is to  compare the IASI SSTs with the OSTIA SST analysis generated there using all the  available satellite and in-situ data.  This would involve an element of training  in using large model datasets in the analysis. Working at the Met Office is also  an opportunity to learn from the scientists in the Satellite Applications group  on the use of satellite data for numerical weather prediction. There are also  possible opportunities to attend training courses at the Met Office College.

Please contact Anu Dudhia anu.dudhia@physics.ox.ac.uk to apply.

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