運輸多目的衛星MTSAT観測による可降水量推定手法の開発

抄録

Japanese geostationary meteorological satellite, Multi-functional Transport Satellite (MTSAT), was launched in February 2005 and the algorithms for land surface temperature (LST) retrieval from MTSAT were developed for the monitoring of urban heat island and the other phenomenon¹⁾²⁾. In order to improve the accuracy of LST retrieval from satellite remote sensing data, the information of atmospheric condition, especially atmospheric water vapor content, is absolutely imperative. In addition, since atmospheric water vapor is one of the dominant greenhouse gases and it influences the process of partitioning of incoming solar radiation into sensible and latent heats, the atmospheric water vapor content is one of the key parameters for the analysis of global environmental changes. However, the products of water vapor content are not offered except for radiosonde data and reanalysis products.
Precipitable water (PW) is one of the physical quantities which represents the atmospheric water vapor content. This study aims to produce the hourly precipitable water maps using MTSAT data. A set of precipitable water estimating equations were derived and demonstrated for mapping of hourly PW distribution in clear sky condition using MTSAT data and reanalysis products. These equations were derived by a multiple regression analysis between brightness temperature of MTSAT infrared channels and temperature at 700 hPa from reanalysis products, and PW derived from radiosonde data. The monthly root mean square errors ranged approximately from 6.5 to 11.5 mm. It was revealed that the PW estimating equations could estimate PW with relatively high accuracy from July to September, but it could not in January and February.