Page 198 - 《高原气象》2025年第3期

高 原 气 象 44 卷
756

Analysis of the Characteristics and Causes of Drought-Flood Abrupt

Alternation in Qingyang， Gansu Province in 2022

2
YIN Lixia ， ZHANG Qiang ， CAO Yanchao ， WANG Yanfeng 1
1
3
（1. Gansu Weather Modification Office， Lanzhou 730020， Gansu， China；
2. Gansu Provincial Meteorological Bureau， Lanzhou 730020， Gansu， China；
3. Qingyang Meteorological Bureau， Qingyang 745000， Gansu， China）

Abstract： In the spring and summer of 2022， the spatio-temporal variance of rainfall in Qingyang， Gansu Prov‐
ince， was conspicuously manifest. Regional and staged drought and flood disasters occurred alternately， and ex‐
treme weather phenomena emerged frequently and profoundly. Relying on precipitation observation， circulation
index data， and sophisticated correlation analysis methods， this paper meticulously analyzes the precipitation
characteristics and underlying potential causes of the abrupt change of drought and flood conditions in Qingyang
during 2022. The results are elaborated as follows： （1） The spring and summer precipitation in Qingyang City in
2022 demonstrated remarkable and distinct features. It involved a prolonged duration of drought， an incredibly
rapid transformation between drought and flood， and extreme precipitation that surpassed the historical extremes
with remarkable magnitude. From March to June， the precipitation in numerous counties was less than 50%. In‐
triguingly， the precipitation in July suddenly turned out to be 41. 0% more than that in the same period. The max‐
imum daily rainfall recorded in the regional torrential rain on July 15 was an astonishing 373. 1 mm， shattering
the historical records. Such a rapid and dramatic change in the precipitation pattern is highly uncommon and rare‐
ly observed.（2） The precipitation of each county from March to May exhibited a significantly positive correla‐
tion with the ONI index， while a notably negative correlation with ONI was evident in July. During La Nina
years， the position of the Western Pacific subtropical high shifted northward. Due to high temperatures and
scarce rainfall in spring， Qingyang City became prone to extreme precipitation in summer. In the spring of 2022，
the La Nina event began to intensify with considerable force， which exerted a profound and significant influence
on the sudden and drastic change of drought and flood conditions in Qingyang City.（3） From March to mid-
May， the Arctic Oscillation （AO） index was strikingly higher than the historical average. The weakened cold air
activity led to an overall reduction in precipitation. From mid-July to mid-August， the negative phase of AO col‐
laborated seamlessly with the strong subtropical high， facilitating the concentrated occurrence of heavy rain.
（4） From March to June and August 2022， the 500 hPa at the mid-high latitude in Eurasia presented a distinctive
"two trough and one ridge" circulation pattern. Despite the robustness of the Western Pacific subtropical high， the
airflow convergence zone did not encompass Qingyang. Conspicuously， in July， the 500 hPa transformed into a
"two ridges and one trough" pattern. The vigorous cold air and the intense water vapor transportation conspired to
increase the frequency of heavy precipitation， ultimately resulting in the occurrence of extreme precipitation.
Key words： rapid changes in drought and flood； Spring and summer seasons； La Niña； Arctic Oscillation；
Western Pacific subtropical high