Presentation Information
[AAS15-P12]Development of a method for estimating water vapor content from near-infrared celestial bodies using a ground-based all-sky camera★Invited Papers
*Haruki Sugiyama1, Yukihiro Takahashi1, Hisayuki Kubota1 (1.Department of Cosmosciences, Graduate School of Science, Hokkaido University)
Keywords:
Water vapor,near-infrared observation,Ground observation
In recent years, East Asia has seen severe damage caused by torrential rainfall due to developed cumulonimbus clouds. To mitigate these damages, it is necessary to predict the occurrence and scale of these cumulonimbus clouds more quickly.Predicting mesoscale phenomena such as cumulonimbus clouds requires a spatial resolution of approximately 100 m (Bryan et al., 2003). However, the temporal and spatial resolution of existing observational instruments, such as lidar and satellite microwave observations, has been insufficient, making it difficult to provide initial observation-based values with sufficient spatial and temporal resolution for prediction models. In particular, the time it takes for heavy rain to occur after water vapor condenses into clouds (about one hour) after cumulonimbus clouds, and heavy rain events are localized, typically spanning a few kilometers. Therefore, predicting these events necessitates the development of observational methods with higher temporal and spatial resolution than conventional methods.In this study, we aim to use a ground-based all-sky camera system equipped with a fisheye lens and bandpass filter to measure line-of-sight water vapor content over a range of several kilometers with a temporal resolution of approximately 15 minutes. This system acquires spectra from celestial objects at night and calculates the strength of absorption by the Earth's atmosphere. By performing this calculation for multiple celestial bodies within the field of view, it is possible to simultaneously obtain precipitable water vapor in the line of sight within a radius of several kilometers. This should make it possible to obtain water vapor distributions with a spatial resolution of several hundred meters, which has been difficult to achieve with previous ground-based lidars and microwave radiometers.The wavelengths used for observations were the water vapor absorption band around 720 nm, the oxygen absorption band at 761 nm, and four surrounding bands with no absorption. These wavelengths were selected based on the results of previous standard star spectrum observations conducted in Antarctica (Sugiyama, 2023).In this presentation, we will compare the results of test observations conducted in Sapporo with precipitable water vapor data from other observations, and discuss future improvements.