Speaker
Description
Atmospheric water vapor is vital in regulating the global energy balance and the hydrological cycle. Accurate estimates of atmospheric water vapor profiles in the troposphere are essential for understanding the mechanisms that control Earth's climate. The temperature and water vapor retrieved from global GNSS radio occultation (RO) data are invaluable for climate studies due to their accurate, all-sky global observations over both land and ocean. Consistency in multi-RO mission water vapor data is particularly important for long-term global climate studies, which require reliable and consistent data to identify trends, patterns, and changes in atmospheric water vapor. In this study, we use water vapor data from multiple RO missions (e.g., COSMIC-1, COSMIC-2, MetOp A/B/C, KOMPSAT-5, GeoOptics, PlanetiQ, and Spire), consistently retrieved with the same NOAA Center for Satellite Applications and Research (STAR) 1DVAR retrieval model, to establish long-term climate data records (CDRs) of tropospheric water vapor and further study water vapor trends. Since different missions have varying penetration depths, calculating total column water vapor (TCWV) involves filling in the water vapor gap between the RO penetration depth and the surface. This process can introduce uncertainties in RO water vapor trends. To address this issue and reduce the uncertainties, we instead calculated the partial column water vapor (PCWV) from RO data by integrating the water vapor from 850 hPa to upper troposphere. We constructed the time series of PCWV from multiple RO missions, removed sampling errors, de-seasonalized the time series by removing annual cycles, and then estimated global and regional PCWV trends. We quantitatively evaluated the spatiotemporal variabilities of STAR RO PCWV. The RO PCWV trends are compared with those in both PCWV and TCWV derived from ERA5 water vapor data to understand the consistency and difference between RO and reanalysis models over global land+ocean, land, and ocean, and on regional scales. The difference between ERA5 PCWV and TCWV trends (%/decade) is further assessed to understand the effects of water vapor below and above 850 hPa on the overall trends in TCWV. We also identified anomalous water vapor variations related to El Niño or La Niña events and assessed their regional extents in RO and reanalysis data. Furthermore, the relationship between surface temperature and the atmosphere's capacity to hold water vapor, governed by the Clausius-Clapeyron equation (approximately 7% increase in atmospheric water vapor per 1 K global surface temperature rise when negligible changes in relative humidity are assumed), was assessed with RO and ERA5 data. We quantitatively evaluated the relation between global and regional RO and ERA5 water vapor trends and ERA5 surface temperature changes in the context of climate change.
| You plan to attend | Online (MS Teams) |
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