| Author(s) | Fahad M. AL- Kulaiby |
| Affiliation | Associate Professor, Department of Geogrophy, College of Arts, King Saud University Riyadh, Saudi Arabia |
| Title | Suggested Mathematical Indices for Determining the Stability and Instability Conditions in the Central Part of Saudi Arabia |
| Source | Journal of King Saud University. Arts. Volume 17, No 2. (2005/1425) |
| Abstract | Prediction of the atmospheric stability is very important for many aspects because it allows avoiding the negative impact of the severe weather conditions such as flash flood, thunderstorms, high-speed wind and hail. The atmospheric stability forecast strongly depends on many mathematical stability indices. In a previous research, It has been found that the recent stability indices that are used by the Presidency of Meteorology and Environment Protection in Saudi Arabia for stability forecast fail, in may cases, in detecting the stability condition in the middle part of Saudi Arabia. This study comes to suggest some modification for some of the recent used stability indices to improve its function and to suggest better new stability indices for the middle part of Saudi Arabia. To achieve the goals of this study, daily surface and upper data for Riyadh weather station were employed. This data represent many meteorological variables that are important for the formation of the stability condition. These variables represent many meteorological elements for the surface and many upper levels; namely, 900mb 9Ph, 850mb 9Ph, 700mb 9Ph,500mb 9Ph, 300mb 9Ph and 200mb 9Ph. In this research, some statistical and meteorological techniques were employed to investigate the nature of the relationships between the studied variables and the stability conditions. In addition, experimental techniques were employed to establish the modifications for the recent indices and to build the new indices The investigations of the relationships between the studied variables and the stability condition in the central part of Saudi Arabia revealed that stability condition in the region is strongly affected by the following variables: 1) The relative humidity at the surface and upper levels up to 700mb. 2) The upper level wind speed between 850mb and 700mb in spring and between 850mb and 500mb in winter. 3) The temperature at 500mb. The mathematical experiments indicate that the modifications in the thresholds of the recent indices improve its functions in detecting the stability conditions in the central part of Saudi Arabia. Also, the experiments, which are based on the nature of the relationship between the studied variables and the stability condition in the region, allowed building better new stability indices for the region. The suggested new indices are two: one for the spring season and the other for the winter season. Testing the new indices indicates that they perform better than the recent used indices in forecasting the stability condition in the region. However, using these two new indices along with the recent ones, after modifying their thresholds, gave better results. |
