Based on observed minute precipitation data during Lekima influencing Zhejiang (from 2019–08-07 00:00:00 to 2019–08-12 23:55:00), the rainfall thresholds for debris flow and landslide are investigated. The rainfall intensity and duration (I-D) thresholds are I = 1247.73D−403.44 + 19.09 and I = 142.63D−0.58–3.37 for debris flow and landslide, respectively. Hourly meteorological data and soil data reveal that (1) the soil volume water content (SVWC) at deep soil layers (50–100 cm) fluctuated continuously during the occurrence of debris flow and landslide. At the end of the landslide period, SVWC at deep soil layers returned stable. (2) At the same soil layer, there was little difference between the upper adjacent values of SVWC in the periods of debris flow and landslide, but the lower adjacent values in the period of landslide were smaller. However, different from the distribution of soil moisture, the lower adjacent values of the soil temperature at all layers were basically the same when debris flow and landslide occurred, while the upper adjacent values were higher when landslide occurred than when debris flow occurred. (3) Compared with the whole typhoon influencing period and debris flow occurrence period, ground surface temperature and surface air temperature, soil temperature, and surface air temperature showed better correlations in landslide occurrence period. (4) Both during debris flow and landslide occurrence time, the soil temperature at all layers did not change with the change of soil depth. Soil temperature and moisture at shallow soil layers owned better correlations than at deep soil layers.

Abstract. The lightning location system based on multiple sub-stations is an effective means of lightning observation. This study first compares the two nationwide lightning location systems in China, the Advanced TOA and Detection System (ADTD) and the Three-Dimensional Lightning Location System (3D-LLS), using the observations in 2020. As a significantly updated version of ADTD, 3D-LLS has a cloud-to-ground (CG) detection efficiency of nearly twice ADTD. However, its scarce distribution sites in central Tibet, western Xinjiang, eastern Qinghai, and eastern Heilongjiang account for some blind observation areas where ADTD could play a supplementary role. The ratio of +CG and the distribution of currents indicate that 3D-LLS misjudges a certain number of intracloud (IC) pulses as return strokes. Besides, the IC detection developed by 3D-LLS is still inefficient. In the results, the IC flashes only account for half of CG flashes, much smaller than the regular ratio (twice). According to the comparison with the nearly no-miss optical observations in Guangzhou, the CG detection efficiency of ADTD and 3D-LLS herein is 24.5 % and 50.5 %. Further improvements are expected in terms of the above shortages. Still, the ground-based observation has better detection efficiency and accuracy than the satellite, especially for CG lightning. The dataset from ADTD in 2016–2021 is employed to analyze the lightning characteristics' temporal and spatial distributions and the difference between +CG and −CG over China. It can be concluded that low latitude, undulating terrain, seaside, and humid surface are favorable factors for lightning occurrence. Thus the southeast coastland has the largest lightning density, while the northwest deserts and basins and the western and northern Tibetan Plateau have almost no lightning. For the period with high CG frequency (summer of a year or afternoon of a day), the ratio of +CG and the discharge intensity is relatively small. The Tibetan Plateau leads to the complexity of lightning activity in China and lays the foundation for studying the impact of surface elevation on lightning. Results indicate that the +CG ratio on the eastern and southern plateau is up to 15 %, and the west and north sides have a low percentage. The discharge intensity of +CG and −CG on the Tibetan Plateau is approximate, while the +CG always has a larger current than −CG on the plains.

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