The Earth Observing System (EOS) Microwave Limb Sounder (MLS) is one of four instruments on the NASA's EOS Aura satellite, launched on July 15, 2004. More information about Aura's science contributions can be found here. MLS makes measurements of atmospheric composition, temperature, humidity and cloud ice that are needed to (1) track stability of the stratospheric ozone layer, (2) help improve predictions of climate change and variability, and (3) help improve understanding of global air quality.

In addition to the operational analysis of MLS by BASCOE, available since 2009, BRAM (BASCOE Reanalysis of Aura MLS) provides analyses since September 2004 when MLS starts to deliver. BRAM is obtained by the EnKF version of BASCOE and is driven by ERA-Interim wind and temperature fields provided by ECMWF. The horizontal resolution of BRAM is 3,75° in longitude and 2,5° in latitude. The vertical domain is from the surface to 0.1 hPa resolved by 37 levels (25 levels above 100 hPa) which are a subset of the 60 levels of ERA-Interim. The output frequency is 6 hours.

MLS assimilated species are: O3, H2O, N2O, HNO3, HCl, ClO, CH3Cl and CO, i.e. the MLS species that do not need to be averaged before scientific use. BRAM outputs, for version r9718 Release 1, are the same species plus Cl2O2. The dataset is provided in NetCDF-CF files with one file per year and per constituents. Constituents abundance is given in volume mixing ratio (vmr or mol/mol) on the hybrid pressure grid of BASCOE. To allow conversion of vmr to number densities and/or transforming the vertical pressure grid into geopotential height, the ERA-Interim temperature and the Earth geopotential at the same resolution of BRAM are also available.

Currently, BRAM is validated by comparison against satellite observations provided by ACEFTS, MIPAS (IMK retrieval algorithm) and the Harmoz O3 CCI limb profiles.


Access to BRAM datasets



 18-Apr-17: Web page open to public. Datasets not yet available.