Characteristics of Spatial-Temporal Distribution of the Stratospheric Quasi-Zero Wind Layer in Low-Latitude Regions

In order to find suitable airspace for the stratospheric airship, the characteristics of spatial-temporal distribution of the stratospheric Quasi-Zero Wind Layer (QZWL) in low-latitude regions are analyzed using the EOF (Empirical Orthogonal Function) method and based on the ERA-Interim daily reanalysis data. The QZWL is mainly influenced by the stratospheric seasonal transition and the Quasi-Biennial Oscillation (QBO), and can be classified into two categories. The northern type of QZWL occurs at 20°N from October to April, while the southern type of QZWL occurs all year round during the westerly QBO phase. The southern type of QZWL is located at around 5°N from May to November and merged with the northern type in the remaining time. Monthly statistical modeling studies in different QBO phases indicate that the probability density function of Weibull distribution fits well wind speed data collected at Haikou station and Nansha station. The specific probability distribution of wind speed predicted by the Weibull distribution and cumulative function can be used to determine suitable airspace for the stratospheric airship. As a result, the airspace at the height between 50 hPa and 30 hPa from October to April at Haikou station and at the height between 70 hPa and 50 hPa for the whole year in the westerly QBO phase at Nansha station are suitable for the stratospheric airship to make smooth flight.