Technical note Evidence of the coexistence of upstream and downstream solitary wavetrains in the real atmosphere

From a true colour image of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) onboard the Orbview-2 satellite, we observed two packets of orderly wave clouds on two sides of Hainan Island in the South China Sea. A packet of 23 wave clouds stretches southward from the island. A second packet of more than 20 wave clouds stretches north-eastward off the north-east coast of the island. The concave orientation of the wave cloud lines implies that both packets are propagating away from the island. A chart of geopotential height and velocity at 850 mbar shows a south-westerly air flow over the island; hence the two wave cloud packets propagate upstream and downstream, simultaneously. Thus, we have found new evidence of the coexistence of both upstream and downstream solitary wavetrains generated in the real atmosphere by land topographic disturbances. Comparison with theoretical results supports this conclusion.