Abstract
Abstract. The Infrared Atmospheric Sounding Interferometer (IASI) is a new generation spaceborne passive sensor mainly dedicated to meteorological applications. Operational Level-2 products have been available via the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) for several years. In particular, vertical profiles of water vapor measurements are retrieved from infrared radiances at the global scale. Nevertheless, the robustness of such products has to be checked because only a few validations have been reported. For this purpose, the field experiments that were held during the HyMeX and ChArMEx international programs are a very good opportunity. A H2O-Raman lidar was deployed on the Balearic island of Menorca and operated continuously for ~ 6 and ~ 3 weeks during fall 2012 (Hydrological cycle in the Mediterranean eXperiment – HyMeX) and summer 2013 (Chemistry–Aerosol Mediterranean Experiment – ChArMEx), respectively. It measured simultaneously the water vapor mixing ratio and aerosol optical properties. This article does not aim to describe the IASI operational H2O inversion algorithm, but to compare the vertical profiles derived from IASI onboard (meteorological operational) MetOp-A and the ground-based lidar measurements to assess the reliability of the IASI operational product for the water vapor retrieval in both the lower and middle troposphere. The links between water vapor contents and both the aerosol vertical profiles and the air mass origins are also studied. About 30 simultaneous observations, performed during nighttime in cloud free conditions, have been considered. For altitudes ranging from 2 to 7 km, root mean square errors (correlation) of ~ 0.5 g kg−1 (~ 0.77) and ~ 1.1 g kg−1 (~ 0.72) are derived between the operational IASI product and the available lidar profiles during HyMeX and ChArMEx, respectively. The values of both root mean square error and correlation are meaningful and show that the operational Level-2 product of the IASI-derived vertical water vapor mixing ratio can be considered for meteorological and climatic applications, at least in the framework of field campaigns.
Highlights
Satellite observations are powerful tools for meteorological forecasting
The atmospheric situations observed during the coincidences present significantly high moisture content (WVMR > 5 g kg−1 in the free troposphere and water vapor integrated content (WVIC) close to 2 g cm−2) for 4 (5) cases during the HyMeX (ChArMEx) time period, which correspond to coincidence number (CN) = 1, 2, 6 and 10 (2, 5, 6, 7 and 8)
Such situations are generally well represented by the Level-2 product of the Infrared Atmospheric Sounding Interferometer (IASI) operational ground segment, excepted for CN = 10 during the HyMeX time period, where the IASI product overestimates the water vapor mixing ratio (WVMR) by ∼ 25 %
Summary
Satellite observations are powerful tools for meteorological forecasting. Their assimilation in models leads to an improvement in weather forecasts (e.g., Collard and McNally, 2009; Bormann et al, 2010). Among the main components of the atmospheric state, water vapor is an essential element, which plays a key role in frontogenesis, convection (e.g., Held and Soden, 2000), cloud formation, and aerosol hydration (e.g., Larson and Taylor, 1983; Rood et al, 1987; Randriamiarisoa et al, 2006). In this way, it significantly influences the Earth climate and the atmospheric chemistry (e.g., IPCC, 2013). For reliable weather forecasts, the vertical profile of the water vapor has to be precisely assessed
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