Drought Monitoring based on Vegetation Types using Observations and Reanalysis Data

Abstract:

A drought is a period of abnormally dry weather lasting long enough to cause a serious hydrological imbalance, which can have a major impact on society in terms of economics, environment, and human life. Forests cover 63% of South Korea and identifying the effects of droughts on different forms of vegetation is therefore an important issue for society. In addition, the severity and causes of droughts need to be examined from various perspectives, including precipitation, temperature, solar radiation, and water content of the soil. There have been difficulties in diagnosing droughts in South Korea using reanalysis data due to its low resolution. In addition, there has been a lack of research on the relationship of droughts to vegetation forms. Therefore, this study utilizes reanalysis data to derive various indexes that represent meteorological drought, such as the standardized precipitation index (SPI), effective drought index (EDI), China-Z index (CZI), modified CZI (MCZI), rainfall anomaly index (RAI), Delices (RD), and Z-Score Index (ZSI), and evaluates their accuracy in the South Korea based on observation data acquired from the Korea Meteorological Administration and the National Institute of Forest Science. Furthermore, this research aims to examine changes in the spatio-temporal distribution of drought indexes based on vegetation classification. From the reanalysis data, an examination was made of the major cases of drought that occurred from 1979 to the present in the South Korea using ERA5 (latest climate reanalysis produced by ECMWF), which has a high resolution of 0.25° × 0.25°. According to the preliminary results based on the last 10 years, it was discovered that the drought indexes that were calculated using the reanalysis data represented droughts in 2013 and 2017 relatively well, and it was shown that the SPI and RAI indexes captured these cases with high accuracy. The most appropriate drought index for the Korean forest areas was identified based on this. In addition, the spatio-temporal variability of droughts in the South Korea over 41 years was analyzed using various factor analysis and correlation analysis methods, for their use in high-resolution forest drought monitoring based on observations and modeling.