The characterization of the water vapor vertical distribution on Mars is currently a very active research topic. Until this last decade, the water cycle has been studied mainly with the analysis of column density abundances. The recent possibility of solar occultation (SO) observations has opened a new path towards a better understanding of the Martian climate [1]. The Mars we observe today is a dry and cold planet although there are abundant evidences suggesting a warmer and wetter environment in the past [2]. Despite being a minor species in the current Martian atmosphere (~0.03%), water vapor has a large variability throughout the year, resulting in a very complex hydrological cycle involving sublimation and condensation processes affected by dust and atmospheric transport [1]. Global Dust Storm Data analysis Super­saturation and water ice Seasonal variation Contact: adrianbm@iaa.es WATER VAPOR VERTICAL DISTRIBUTION ON MARS DURING 5 YEARS OF EXOMARS­TGO/NOMAD OBSERVATIONS A. Brines1, M. A. López­Valverde1, A. Stolzenbach1, A. Modak1, B. Funke1, F. G. Galindo1, S. Aoki2,3, G. L. Villanueva4, G. Liuzzi4,5, I. R. Thomas2, J. T. Erwin2, U. Grabowski6, F. Forget7, J.J. Lopez­Moreno1, J. Rodriguez­Gomez1, F. Daerden2, L. Trompet2, B. Ristic2, M. R. Patel8, G. Bellucci9 and A. C. Vandaele2 1Instituto de Astrofísica de Andalucía (IAA/CSIC), Spain; 2Royal Belgian Institute for Space Aeronomy, Belgium; 3Department of Complexity Science and Engineering, University of Tokyo, Japan; 4NASA Goddard Space Flight Center, USA 5American University, Washington DC, USA; 6Karlsruhe Institute of Technology, Karlsruhe, Germany; 7Laboratoire de Météorologie Dynamique, IPSL, Paris, France; 8Open University, UK; 9Istituto di Astrofisica e Planetologia, Italy VII Reunión de Ciencias Planetarias y Exploración del Sistema Solar Valladolid 11, 12 y 13 de julio de 2023 Here we present a summary of results about the characterization of the water vapor in the Martian atmosphere. We study its seasonal variability during 3 Martian Years (MY) analyzing almost 5 years (April 2018 to December 2022) of NOMAD SO observations. We present a detailed insight of specific periods showing the effects of dust storms and detections of supersaturation. NOMAD is an infrared spectrometer covering the spectral range between 0.2 to 4.3 µm. Its SO uses an echelle grating with with an Acousto­Optical Tunable Filter (AOTF) to select different diffraction orders to be used during the observations. The spectral resolution of the SO channel is λ/∆λ = 20,000. The sampling allows a vertical resolution of 1 km. Also, the AOTF permits probing the atmosphere at a given altitude through 6 different diffraction orders [7]. For this study, we use Level 1 SO calibrated transmittances [8] of diffraction orders 134 (3011­3035 cm­1), 136 (3056­3081 cm­1) for the lower atmosphere and 168 (3775­3806 cm­1), 169 (3798­3828 cm­1) for the upper atmosphere. We have developed pre­processing tools to identify and eliminate residual artifacts in the spectra (bending, spectral shift) using the line­by­line radiative transfer algorithm KOPRA [9]. For the inversions, we use the latest calibration of the NOMAD AOTF and its instrumental line ­ shape (ILS) [10]. The retrievals are done combining the spectra of low altitude orders (134,136) with spectra of high altitude orders (168,169) up to 120 km for occultations where those orders where observed simultaneously. The bottom panels show two examples of typical NOMAD spectra (black) after its bending and spectral shift corrections for diffraction orders 136 (panel A) and 169 (panel B) at 30 and 100 km respectively. We also show the fitting after the retrieval (red). For optimization purposes, we only fit the data at certain spectral windows where the strongest H2O absorption lines are located. The panel on the right shows a typical retrieved H2O vertical profile (blue) and the GCM a priori used during its inversion. For this example, we are not fitting the data