Evaluating satellite limb measurements of nitrous oxide

<jats:p>Abstract. As of the early 2000s, multiple contemporaneous global and vertically resolved nitrous oxide (N2O) datasets have become available from a suite of limb-viewing satellite instruments. Together, these datasets provide a 23-year and counting continuous N2O record. Due to its long lifetime, N2O is a valuable tracer of atmospheric transport, and a reliable long-term record therefore allows the examination of changes in stratospheric circulation as a result of climate change. In order to combine results from different satellite datasets for these purposes, it is necessary to account for their biases, which can be determined through evaluation studies. Here, N2O measurements in the upper troposphere and lower-to-middle stratosphere (5–40 km) are evaluated from five different satellite limb sounders: ACE-FTS on SCISAT, HIRDLS and MLS on Aura, MIPAS on Envisat, and SMR on Odin. This is done by comparing colocated satellite measurements with each other to determine the instruments’ relative biases and by comparing each dataset with independent reference data from balloon-borne instruments. ACE-FTS (v5.2), the two MIPAS datasets (V8), and SMR (v3.0.0) agree within ±5–10 %, but HIRDLS (v07) has variable performance depending on the region and time of year. MLS (v5) has a persistent deviation resulting in a low bias of up to 30 % in the lower stratosphere at 24 km. This bias is substantially reduced in v6. These findings are corroborated by the comparisons of each satellite instrument with balloon-borne data. This study lays the groundwork for creating a merged and bias-corrected N2O time series spanning from 2002 to the present using ACE-FTS, MIPAS, SMR, and possibly the MLS v6 dataset.</jats:p>