Liu Mingyuan

Performance Evaluation of a Self-Developed Ozonesonde and Its Application in an Intensive Observational Campaign

Abstract To make a detailed test on the reliability and detection performance of the electrochemical concentration cell (ECC) type ozonesonde which had been developed and preliminarily evaluated by the authors, an intensive ozonesonde release experiment was held at two sites in Beijing and Changchun in June 2013. The results showed that the mean background current and its standard deviation were 0.03 (0.04) μA and 0.02 (0.03) μA in Beijing (Changchun). The average response time and its standard deviation were 27.8 s (30.4 s) and 4.0 s (3.7 s) in Beijing (Changchun). The ozone partial pressure profiles at both sites showed a central peak in the stratosphere and a side peak in the boundary layer. Large variation in ozone partial pressure was observed at the middle levels of the atmosphere (10–17 km). A more marked gradient of ozone change was observed in Beijing (3.4 mPa kmࢤ1) at the lower atmosphere level, as compared to that in Changchun (0.4 mPa kmࢤ1). The results presented in this paper indicate that this self-developed ozonesonde shows a high level of reliability and good performance. The ozonsonde is expected to play an important role in operational observations of ozone profiles.

Characteristics of a Negative Cloud-to-Ground Lightning Discharge Based on Locations of VHF Radiation Sources

Abstract The lightning very high frequency (VHF) radiation location system based on the short-baseline time-difference of arrival (TDOA) technique provides an effective approach to describe the temporal and spatial development of lightning discharge in two dimensions with high resolution. A negative single-stroke cloud-to-ground (CG) lightning flash was analyzed in detail using the radiation location results and synchronic fast/slow electric field changes. The long-duration preliminary breakdown process appeared to propagate with bi-directional leader channels. The two negative simultaneous discharge channels sloped down with a considerable horizontal component in the lower positive charge region at speeds of about 105 m s-1. The stepped leader was clearly converted from one channel of the preliminary breakdown process and spread downwards with branches. The speeds of the stepped leaders were about 105 m s-1. The K processes after the return stroke could either directly initiate from the start region with negative polarity lightning discharge, or initiate from a new region in the cloud as negative recoil streamers. All K processes propagated along the preceding electrified channel, while not all K processes initiated from the tips of positive breakdowns. The speeds of the K processes were about 106-107 m s-1.