| 1 | The orientation of the minimal safe flight height is researched. | |
| 2 | The circulation of the free atmosphere is predominantly (largely) zonal and only to a slight extent (to a less degree) meridional. | |
| 3 | To slope or incline . The tendency to grow at an oblique or horizontal angle . | |
| 4 | The current designs with optimum global isotropy are developed through an exhaustive search. | |
| 5 | Just based on the above reasons and arguments, the author put forward a completely new concept:tropism. |