Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December. (Photos: Xinhua)

Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December.

Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December.

Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December.

Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December.

Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December.

Aerial photo taken on Dec. 27, 2019 shows the Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake went into a "frozen period" in mid-December.