Analysis of the Dominant Wind Direction of Danniang Dune

Danniang's sand dunes were formed by the accumulation of wind power. Every winter and spring (mainly from October to March of the next year), the climate in this area was dry, and the wind was strong. In addition, the vegetation was thin, and the wind was less blocked by the river surface, thus forming a vortex updraft. The airflow carried sand grains on the sandbars and floodplains. It was blocked by the mountainous terrain along the river, and the wind speed slowed down. The sand grains piled up on the hillside and accumulated over time to form sand dunes. Regarding the dominant wind direction of Danniang Dune, according to the information provided, documents 1 and 2 described that Danniang Dune was located at the foothills on the north bank of the Yarlung Zangbo River in Milin County, Xizang, while documents 2 and 3 mentioned that there was little rainfall in winter and spring, the river level was low, and the beach and sandbar were exposed. However, there was no clear information about the direction of the wind. Thus, it was impossible to determine the dominant wind direction of Danniang's sand dune.

Danniang's sand dunes were formed by the accumulation of wind power. Every winter and spring, the climate in this area was dry, and the wind was strong. In addition, the vegetation was thin, so the wind was less blocked by the river surface, forming a vortex updraft. These air currents carried sand grains from the sandbars and floodplains, which were blocked by the mountainous terrain by the river. The wind speed slowed down, and the sand grains piled up on the hillside, forming Danniang sand dunes over time. The formation of sand dunes took decades or even centuries. It was the result of the interaction between the natural environment and the wind.

Danniang Sand Dune was located in Danniang Township, Milin County, Xizang, 90 kilometers away from the confluence of the two rivers. It was the largest sand dune in the middle of the Yarlung Zangbo River. The sand dunes were formed mainly because the sand grains from the nearby sandbars and floodplains were piled up on the slopes by the wind, forming the current sand dunes over time. Danniang Sand Dune was also known as the Buddha Palm Sand Dune because it was shaped like a Buddha's palm. The climate in this area is diverse, including tropical, sub-tropical, temperate-zone and frigid climate, and the annual rainfall is about 650 millimeters. The best season to view Danniang sand dunes was winter and spring. At this time, the water flow of the Yarlung Zangbo River slowed down, the riverbed was exposed, and the wind was strong, making the sand dunes more obvious.

The Danniang Sand Dune was named because it was shaped like a giant Buddha's palm. It reflected the reflection of the Yarlung Zangbo River, as if two Buddha's palms were praying. Therefore, Danniang Sand Dune was also known as Buddha Palm Sand Dune.

The sand source of Danniang Sand Dune mainly came from the exposed river course of the Yarlung Zangbo River during the dry season. Sand grains accumulated on the hillside over time to form sand dunes.

The direct sand source of Danniang Sand Dune mainly came from the nearby sandbars and floodplains.

The terrain of the river where Danniang Dune was located was a river valley.

The valley where Danniang Dune was located was featured by dense contours on both sides of the valley floor, steep valley slopes, large slopes, and relatively high heights. The contours near the valley where the sand dunes were located were sparse and extended to higher altitudes. The river course was more curved, the flow of the river was slower, and the accumulation of water was stronger. The sand dunes were formed by the accumulation of wind power, and the source of the sand was the flood plains and sandbars.

Danniang sand dunes were formed in the winter and spring season (October to March of the following year). The climate was dry and windy. The area where the strong wind passed by had little vegetation. In addition, it passed through the river surface, so it was less blocked, forming a vortex ascending airflow. These airflows carried the sand on the sandbars and river banks, which were blocked by the mountainous terrain beside the river. The wind speed slowed down, and the sand piled up on the hillside. After a long time, it formed the Danniang sand dune.

The direct reason for the decrease in the area of Danniang sand dunes might be the destruction of vegetation upstream.