ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Research on the Features of Drylines Triggering Convective Weather in Shandong
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Abstract:
Using conventional upper-air and surface observations, Doppler radar data, satellite nephogram and ERA5 reanalysis data, 451 drylines cases and 156 drylines cases triggering convection in Shandong Province from 2001 to 2022 were analyzed. Results are as follows: the total number of days for drylines in Shandong from 2001 to 2022 was 451 days, with 156 days triggering convective drylines. Drylines triggering convection occurred from April to September. May and the first ten-day period of May were the months and ten-day periods with the highest frequency of drylines occurrences. The primary occurrence time was between 14:00 and 17:00 (Beijing Time). The drylines are primarily distributed in central and northwestern Shandong. The formation of drylines is related to the influence of mountain ranges and the distribution of land and sea. The widths of convective and non-convective drylines are 75–106 km and 80–114 km, respectively, with dew point gradients of 11.8–16.7°C/(100 km) and 9.8–15°C/(100 km). Temperature distributions on both dry and wet sides of drylines range from 23 to 33°C, with a temperature gradient of 1–3 °C /(100 km), temperatures on the dry side are slightly higher. Compared to non-convective drylines, convective drylines exhibit higher temperatures and dew points on both the warm and cold sides, narrower widths, greater dew point gradients, this is related to the fact that the circulation associated with the force-driven component becomes stronger when the horizontal dew point gradient is large. The thresholds of the key environmental parameters for drylines triggering convection reveal that while vertical wind shear between 0-1 km and 0-3 km are difficult to distinguish due to minimal differences, other parameters including surface dew point temperature(Td), precipitable water (PW), CAPE, CIN, temperature difference between 850 and 500 hPa, DCAPE, severe weather threat index (SWEAT), and vertical wind shear between 0–6 km exhibit certain distinguishability between convective and non-convective drylines. The seasonal variation in convective parameters under unstable conditions is relatively small, but environmental parameters related to moisture conditions and vertical wind shear between 0–6 km exhibit significant seasonal differences. Therefore, their thresholds should be differentiated by season. Drylines frequently develop under conditions of northwest flow, ahead of westerly trough, and northeast low-pressure vortex at the upper-level 500 hPa. They are primarily influenced by the shear line of the low-pressure vortex or the northwest flow at the lower-level 700 hPa and 850 hPa, with the boundary layer often accompanied by shear lines. The surface situation is primarily situated within the convergence flow field of continental warm low or at the bottom or front of low-pressure systems.
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