Abstract
Atmospheric water vapor content or total precipitable water (TPW) is a highly variable atmospheric constituent, yet it remains one of the meteorological parameters that is most difficult to characterize accurately. We develop a framework for estimating atmospheric TPW from Visible Infrared Imaging Radiometer Suite (VIIRS) data in this study. First, TPW is retrieved from VIIRS top-of-atmosphere (TOA) radiance of channels 15 and 16 using the refined split-window covariance-variance ratio (SWCVR) method. Then, the VIIRS TPW is blended with the microwave integrated retrieval system (MIRS) derived TPW via Bayesian model averaging (BMA) to improve the accuracy of VIIRS TPW. Three years (2014–2017) of ground measurements collected from SuomiNet sites over North America are used to validate the VIIRS TPW and blended TPW. The mean bias error (MBE) and root mean square error (RMSE) of the VIIRS TPW are 0.21 g/cm2 and 0.73 g/cm2, respectively, and the accuracy of the VIIRS TPW in daytime is much better than at night time. The MBE and RMSE of BMA integrated TPW are 0.06 g/cm2 and 0.35 g/cm2, and the accuracy difference between daytime and nighttime is also removed. The global radiosonde measurements are also collected to validate the BMA integrated VIIRS TPW. The MBE and RMSE of the BMA integrated TPW are 0.09 g/cm2 and 0.44 g/cm2 compared to the radiosonde measurements. This accuracy is also superior to the VIIRS TPW. Therefore, it is concluded that the developed framework can be used to derive accurate clear-sky TPW for VIIRS. This is the first time that we can obtain high accuracy TPW from VIIRS. This study will certainly benefit the study of atmospheric processes and climate change.
Highlights
Total atmospheric water content is the mass of water vapor contained in a vertical atmospheric column from the surface to the top of the atmosphere, known as total precipitable water (TPW)
Two indicators are selected to depict the accuracy of the derived TPW, the mean bias error (MBE) and root mean square error (RMSE)
Where N is the number of samples; Ei,true is the true value of TPW, derived from atmosphere profile or measured by the ground-based global positioning systems (GPS) network; Ei,derived is the derived TPW
Summary
Total atmospheric water content is the mass of water vapor contained in a vertical atmospheric column from the surface to the top of the atmosphere, known as total precipitable water (TPW). There are three types of methods for obtaining TPW: ground-based observations, radiosonde techniques, and satellite remote sensing. It is widely acknowledged that the radiosonde technique is one of the most accurate ways to monitor the TPW, as it can even obtain water vapor at various atmosphere pressure levels [5]. Ground-based observations usually have high accuracy and good continuity at time scales for the study of long-term trends. Ground-based observations cannot be used at large scales and cannot reveal the spatial distribution of TPW. Satellite remote sensing provides an effective way for large-scale observation of TPW
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