Aura Microwave Limb Sounder upper tropospheric and lower stratospheric H ₂ O and relative humidity with respect to ice validation

Abstract

The validation of version 2.2 (v2.2) H 2 O measurements from the Earth Observing System (EOS) Microwave Limb Sounder (Aura MLS) on the Aura satellite are presented. Results from comparisons made with Aqua Atmospheric Infrared Sounder (AIRS), Vaisala radiosondes, frost point hygrometer, and WB57 aircraft hygrometers are presented. Comparisons with the Aura MLS v1.5 H 2 O, Goddard global modeling and assimilation office Earth Observing System analyses (GEOS‐5) are also discussed. For H 2 O mixing ratios less than 500 ppmv, the MLS v2.2 has an accuracy better than 25% between 316 and 147 hPa. The precision is 65% at 316 hPa that reduces to 25% at 147 hPa. This performance is better than expected from MLS measurement systematic error analyses. MLS overestimates H 2 O for mixing ratios greater than 500 ppmv which is consistent with a scaling error in either the calibrated or calculated MLS radiances. The validation of the accuracy of MLS v2.2 H 2 O from 121 to 83 hPa which is expected to be better than 15% cannot be confirmed at this time because of large disagreements among the hygrometers used in the AVE campaigns. The precision of the v2.2 H 2 O from 121 to 83 hPa is 10–20%. The vertical resolution is 1.5–3.5 km depending on height. The horizontal resolution is 210 × 7 km 2 along and perpendicular to the Aura orbit track, respectively. Relative humidity is calculated from H 2 O and temperature. The precision, accuracy, and spatial resolution are worse than for H 2 O.