Abstract
Abstract. Atmospheric water vapor plays a key role in Earth's radiation balance and hydrological cycle, and the precipitable-water-vapor (PWV) product under clear-sky conditions has been routinely provided by the advanced Medium Resolution Spectral Imager (MERSI-II) on board Fengyun-3D since 2018. The global evaluation of the PWV product derived from MERSI-II is performed herein by comparing it with PWV from the Integrated Global Radiosonde Archive (IGRA) based on a total of 462 sites (57 219 matchups) during 2018–2021. The monthly averaged PWV from MERSI-II presents a decreasing distribution of PWV from the tropics to the polar regions. In general, a sound consistency exists between PWV values of MERSI-II and IGRA; their correlation coefficient is 0.951, and their root mean squared error (RMSE) is 0.36 cm. The histogram of mean bias (MB) shows that the MB is concentrated around zero and mostly located within the range from −1.00 cm to 0.50 cm. For most sites, PWV is underestimated with the MB between −0.41 and 0.05 cm. However, there is also an overestimated PWV, which is mostly distributed in the area surrounding the Black Sea and the middle of South America. There is a slight underestimation of MERSI-II PWV for all seasons with the MB value below −0.18 cm, with the bias being the largest magnitude in summer. This is probably due to the presence of thin clouds, which weaken the radiation signal observed by the satellite. We also find that there is a larger bias in the Southern Hemisphere, with a large value and significant variation in PWV. The binned error analysis revealed that the MB and RMSE increased with the increasing value of PWV, but there is an overestimation for PWV smaller than 1.0 cm. In addition, there is a higher MB and RMSE with a larger spatial distance between the footprint of the satellite and the IGRA station, and the RMSE ranged from 0.33 to 0.47 cm. There is a notable dependency on solar zenith angle of the deviations between MERSI-II and IGRA PWV products.
Highlights
Water vapor is an important component of the atmosphere and widely known as an important greenhouse gas, since it can significantly affect climate change, the radiation balance, and the hydrological cycle (Kiehl and Trenberth, 1997; Held and Soden, 2000; Dessler and Wong, 2009; Zhao et al, 2012)
The averaged PWV derived from Medium Resolution Spectral Imager (MERSI)-II shows a decreasing distribution of PWV with increasing latitude, and high PWV values are mostly found in the tropics and rarely in high latitudes
We evaluated the global clear-sky PWV product derived from FY-3D MERSI-II by comparing it with PWV from 462 Integrated Global Radiosonde Archive (IGRA) stations, with 57 219 matchups during the period from September 2018 to June 2021
Summary
Water vapor is an important component of the atmosphere and widely known as an important greenhouse gas, since it can significantly affect climate change, the radiation balance, and the hydrological cycle (Kiehl and Trenberth, 1997; Held and Soden, 2000; Dessler and Wong, 2009; Zhao et al, 2012). The spatiotemporal variations in water vapor are essential for understanding the formation of clouds, and mesoscale meteorological systems in those clouds and precipitation always rely on changes in water vapor (Trenberth et al, 2003). Water vapor can influence the atmospheric transmittance and the upward radiance measured by the satellite sensor. The information about water vapor is required to correct atmospheric effects in the satellite-based retrieval algorithm for land surface temperature (Meng et al, 2017). Zhang et al.: Global evaluation of the MERSI-II PWV product
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
