2018 Volume 14 Pages 86-90
The kinetic energy associated with Chang-ma periods was investigated using rawinsonde data from Korea during 2013-2015. Changes in kinetic energy (which is defined in terms of storm relative helicity, SRH) were more pronounced than changes in thermal energy (which is defined in terms of convective available potential energy, CAPE) during precipitation. The median value of SRH increased by 14, 125, and 185 m2 s−2 in no-rain, weak-rain (< 5 mm 3 hr−1), and strong-rain (≥ 5 mm 3 hr−1) time periods, respectively. However, the values of CAPE remained below 100 J kg−1 regardless of the rainfall intensity. Moreover, the correlation coefficients (R) between SRH and precipitation amount about 0.4 with 99% confidence level. In addition, we used two vectors constituting the SRH (storm motion vector and horizontal wind vector) to determine the reason for the SRH differences. The change in the y-components of the horizontal wind vector at low levels (850-750 hPa) was determined to be closely related to SRH. The increase in SRH during the precipitation periods was therefore determined to be due to the low-level southerly wind. Based on these results, we conclude that SRH can be used not only to predict mesoscale storms but also to forecast precipitation in the early summer monsoon season in Korea.
