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Heat events were identified based on the daily maximum temperature data at 27 meteorological stations located in the Beijing-Tianjin-Hebei region from 1960 to 2019. The Copula function was introduced to fit the joint cumulative probability distribution of the two characteristics, taking into account the duration of heat events and the heat intensity (defined as ≥35°C accumulated temperature), so as to obtain the joint return period of the heat events with arbitrary duration and heat intensity and analyze the return period characteristics of heat events in the Beijing-Tianjin-Hebei region. The results demonstrate that the distribution of the frequency and severity of heat events in the Beijing-Tianjin-Hebei region is higher in the south and lower in the north, but the increase in frequency, duration and average daily intensity is lower in the south and higher in the north; the effect of POISS function is optimal at all sites by fitting the edge distribution of the duration of heat events; when fitting the heat intensity, the GEV function works more efficiently at a greater number of station; when combining the duration and intensity of heat events in two dimensions, the Copula function used most is Symmetrised Joe-Clayton function, followed by Frank function; return period of heat events lasting more than five days in the study area exceeds once in five years, and once in 100 years in the northern region. The results of the study can provide a reference for heat disaster prevention and mitigation in the Beijing-Tianjin-Hebei region. [ABSTRACT FROM AUTHOR]

Based on the runoff and sediment yield data from 59 erosive rainfall plots with different slope lengths (5, 10, 15, 20, 25 m) in Shiqiao small watershed of Guizhou Province from 2012 to 2014, we analyzed the relationship between runoff and sediment yield and slope length under diffe-rent rainfall conditions. The results showed that, with the increases of slope length, the runoff yield of slope showed a 'V-shape' pattern, the sediment yield of slope increased first and then decreased. According to rainfall amount, rainfall duration, and average rainfall intensity, the 59 erosive rainfall in the study area could be divided into three types, including type A with short duration, heavy rain intensity and small rainfall, type B with medium duration, light rain intensity and medium rainfall, and type C with long duration, medium rain intensity and large rainfall. The relationships between runoff and sediment yield and slope length were different under different rainfall patterns. There was about 20 m critical slope length of sediment yield under type A and B. The sediment yield gradually increased with the increases of slope length under type C. There was a good cubic function relationship between slope length and runoff and sediment yield under different rainfall patterns. The variable amplitude of runoff and sediment yield was different among different slope lengths. Except the slope length of 15-20 m, the variable amplitude of runoff and sediment yield under type C was relatively large. The variation amplitude of sediment yield was significantly higher than that under other rainfall patterns. The total runoff yield under different rainfall patterns was type A>B>C. The sediment yield under type B was the smallest, that of type A at the slope length of 20 m was the largest and that of type C at other slope lengths was the largest. The correlation between compound rainfall factors and runoff and sediment yield was better than that of single rainfall factor under type A (common rainfall type in the study area). Rainfall amount ( P ), the pro-duct of rainfall duration and maximum 30 min rainfall intensity ( TI 30 ), product of rainfall duration and average rainfall intensity ( TI ), product of rainfall amount and rainfall duration ( PT ) were significantly correlated with the runoff and sediment yield. Among those factors, P and TI had the strongest correlation with runoff. Further, the relationship between them and runoff under different slope lengths could be expressed by linear equation and S-curve. There was a good cubic function relationship between the sediment yield and its corresponding rainfall factors under different slope lengths.