Development and Validation of a New Ozone Dataset Using Complete Data Fusion of MIPAS and IASI Observations: A Step Towards Understanding Stratospheric Ozone Intrusions in the Himalayan Region

Abstract. We present a new ozone dataset generated using the Complete Data Fusion (CDF) algorithm, which combines limb observations from MIPAS-ENVISAT along with nadir observations from IASI during their overlapping operational period (2008–2011). The fusion aims to enhance ozone profile information in the Upper Troposphere–Lower Stratosphere (UTLS), particularly over the Himalayas—a key region for stratospheric intrusion events. The fused dataset, mapped onto the IASI- MetOp grid, includes ozone partial columns with associated uncertainty estimates (covariance matrices, averaging kernels, and a priori profiles). After tuning the algorithm on 2008 data, the product was validated for the 2009–2011 period against ozonesondes from WOUDC stations across multiple latitude bands. Results show that the fused profiles improve vertical information content (degrees of freedom) and reduce uncertainty, successfully propagating MIPAS information to lower altitudes even in regions lacking direct limb observations. While the dataset initially exhibited altitude- and latitude-dependent biases, primarily inherited from IASI, these were significantly reduced through bias correction. The final product is suitable for data assimilation and model evaluation, offering valuable support for atmospheric reanalyses and studies of troposphere–stratosphere exchange processes.