High road-surface temperature due to heat waves can lead to dangerous driving conditions such as tire blowouts and deformation induced by thermal stress on the roads. In this study, a Mobile Observation Vehicle dataset, with high spatial and temporal resolutions for the heat-wave episode that occurred on 16-17 August 2018, is used to understand environmental characteristics on urban road-surface and air temperatures in Seoul. This study demonstrates that the magnitude of urban road-surface temperature is dependent on the differences in incoming solar radiation due to screening of high-rise buildings in the Gangnam area, and is associated with the topographical features in the Gangbuk area. The road-surface temperature in the section of darker-colored asphalts was higher than that of lighter-colored asphalts, with a mean difference of 6.8°C, and both surface and air temperatures on the iron plate were highest, with means of 51.7°C and 35.1°C, respectively. In addition, during the water-sprinkling period, road-surface temperature was cooled by about 8.7°C (19%) compared with that in the period without water-sprinkling, but there was no significant change in air temperature. The current results could be practically used to improve roadsurface temperature prediction models for civil engineers or road managers.

In this study, we used an intensive observation dataset of a mobile observation vehicle (MOVE) to investigate the characteristics of thermal environments and diurnal variations of road surface temperature (RST) and air temperature, particularly at the urban street level, during the 2019 Building Block 3-dimensional urban Meteorological Experiment (BBMEX) campaign in Seoul. For the purpose of comparing characteristics of RST and air temperature with different surrounding thermal environments, we divided the road into four sections (S1: Open Section, S2: High-Rise Buildings, S3: Low-Rise Buildings, S4: Street Trees). This study demonstrates that the greater sky view factors (SVFs) are generally coincident with the greater RSTs, with a significance at the 5% level. The diurnal variations indicated that the time lag between observed maximum air temperature and RST has about one hour, which is attributable to an increase air temperatures above artificial pavement through heat convection with some latency. The diurnal temperature ranges (DTRs) of RST in S2 and S4 were relatively smaller than those of S1 and S3, with differences ranging from 2.9 °C to 4.5 °C. The current results will assist planners and decision makers in determining policy priorities with regard to urban street design and planning.

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 m 2 s −2 in no-rain, weakrain (< 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.

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