This dataset is part of MEaSUREs 2012 Program, and represent Aqua/AIRS-Aura/MLS collocation indexes, in netCDF-4 format. These data map AIRS profile indexes to those of MLS. The A-Train provides water vapor (H2O) retrievals from both the Atmospheric Infrared Sounder (AIRS) and Microwave Limb Sounder (MLS). While AIRS loses sensitivity to H2O at the elevated portions of the upper troposphere (UT), MLS cannot detect H2O below 316 hPa. Therefore, to obtain a full profile of H2O in the whole column of air, this dataset manages to join the two products together by utilizing their own averaging kernels (AK). In doing so, the dataset builds a solid H2O of the whole column of air, which will help understand the H2O budget and many processes governing the humidity around the upper troposphere and lower stratosphere (UTLS). The short name for this collections is AIRS_MLS_IND