Page 76 - 《高原气象》2021年第5期

5 期 张一平等：河套及周边地区干线触发对流天气特征初步分析 1037

A Preliminary Analysis of the Characteristics of Drylines and Its

Triggering Convections in the Hetao and Surrounding Regions

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ZHANG Yiping ，YU Xiaoding ，WANG Di ，GUO Yakai ，WU Wenbo ，HAO Xiaozhen 1，2
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（1. Henan Key Laboratory of Agrometeorological Ensuring and Applied Technique，Zhengzhou 450003，Henan，China；
2. Henan Meteorological Observatory，Zhengzhou 450003，Henan，China；
3. China Meteorological Administration Training Center，Beijing 100081，China）
Abstract：Based on the conventional aerological sounding and surface data and the satellite images，the paper
preliminary discussed 52 convective weather processes triggered by drylines in Hetao and its surrounding regions
during May to September from 2013 to 2017，and statistically analyzed the temporal and spatial distribution，the
influence systems and the characteristics of surface meteorological elements and sounding environmental parame‐
ters around the drylines. The result shows that，（1）the drylines in the Hetao and its vicinity areas mainly appears
on the north of Hetao，including its northwest and northeast，and the inner region，with the main orientations
from east-northeast to south-southwest and northeast to southwest，the width of 80~100 km，and the length of
about 300~800 km. The occurrence frequency of drylines has obvious annual change with the annual average of
10. 4 times，that always appearing during June to August and at 11:00（Beijing time，the same as after）-17:00，
especially at 14:00.（2）The convective weather processes triggered by drylines mostly occur in the situation of
high-altitude northwest flow and Mongolia vortex with the influence of low trough south of the vortex，associat‐
ed with convergence lines or shear lines in the atmospheric boundary layer. The drylines is mostly located at the
intersection of the westerly flow in the south and southeast of the continental low and Mongolia low（or cyclone）
and the southerly flow behind the coastal high in the surface weather chart.（3）The statistical characteristics of
ground factors are as follows：the temperature on the dry side of the drylines is higher than on the wet side with
the difference of 1~2 ℃. The sea level pressure on the wet side is slightly higher than that on the dry side and the
pressure difference between the two sides generally ranges from 1. 5~2 hPa. In addition，one of the most impor‐
tant features is the large dew point difference on both sides，with the average of 11 ℃，primarily between 10 and
16 ℃. The dew point gradient is generally above 10 ℃·（100 km） ，with the maximum of 20 ℃·（100 km） or
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above. The westerly wind is prevalent on the dry side while the southly wind on the wet side，producing the con‐
vergence flow field，which is another important feature.（4）According to the statistical results of sounding envi‐
ronmental parameters，the atmospheric precipitable water and the specific humidity of 700 and 850 hPa on the
wet side are significantly larger than those on the dry side. The average atmospheric precipitable water on the wet
and dry side are 2. 5 cm and 1. 5 cm separately. The average convective available potential energy on the wet side
reaches the moderate intensity of 1440 J·kg . while on the dry side less than 10 J·kg ，and the thermal instabili‐
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ty on the wet side is more abundent. The deep vertical wind shear of 0~6 km on both sides is mostly moderate or
above and slightly larger on the dry side，with the average of 12. 2 m·s and 13. 1 m·s on the wet and dry side
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respectively.
Key words：Hetao Area；drylines；convective weather；meteorological elements；statistical characteristicsss