Document Type : Original Research Paper
Authors
1 Department of Geomatics Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran
2 Iranian Space Research Center, Tehran, Iran
Abstract
Background and Objectives: Water vapor in the atmosphere is one of the most critical meteorological parameters, significantly influencing climate studies, weather forecasting, and climate change modeling. Precipitable Water Vapor (PWV) serves as a key indicator in atmospheric studies and is measured using satellite data, including Moderate Resolution Imaging Spectroradiometer (MODIS) sensor products. MODIS provides two PWV products: Near-Infrared (NIR), which is available only during the day, and Infrared (IR), which provides data for both day and night. Due to its broader temporal coverage, the IR product is widely utilized in various applications. However, the accuracy of this product, especially under varying atmospheric conditions during day and night, remains a major challenge. This study aims to enhance the accuracy of MODIS IR PWV data using machine learning and to assess the calibration's impact on day and night conditions.
Methods: This study utilized data from 10 radiosonde stations in Iran during the 2019-2020 period as reference ground-truth data. Three datasets were prepared: raw MODIS data, fitted data, and modified data. A Multi-Layer Perceptron (MLP) model was employed for calibration and to evaluate its performance for day and night data separately. Standard machine learning methods were applied to design and implement the model. The model's accuracy was evaluated using the Root Mean Square Error (RMSE) and correlation coefficient (R) metrics.
Findings: The results demonstrated that the MLP model significantly improved the accuracy of MODIS PWV data. During the day, RMSE decreased from 3.72 mm in the raw data to 2.63 mm in the calibrated model, while the correlation coefficient increased from 0.81 to 0.86. At night, RMSE reduced from 4.9 mm to 3.16 mm, and the correlation coefficient improved from 0.76 to 0.78. Overall, RMSE in raw MODIS data was 4.48 mm, which was reduced to 2.92 mm in the fitted model and 3.03 mm in the modified model. The correlation coefficient also improved from 0.77 to 0.87 and 0.85, respectively.
Conclusion: This study confirmed that the MLP model effectively enhances the accuracy of MODIS PWV data and reduces existing errors under different atmospheric conditions. The primary innovation of this research is the application of the MLP model to calibrate satellite-derived PWV data for day and night conditions. By improving the precision of satellite data, this method enhances its reliability for practical applications, particularly in weather forecasting and climate studies. Limitations include dependency on radiosonde data as the reference and the absence of analysis on specific atmospheric factors influencing modeling. This approach can also be
Keywords
Main Subjects
COPYRIGHTS
© 2025 The Author(s). This is an open-access article distributed under the terms and conditions of the Creative Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) (https://creativecommons.org/licenses/by-nc/4.0/)