This study examines changes in characteristics (amount, frequency, intensity) of daily precipitation in the contiguous United States (CONUS) using high-quality records for a long-term period (1900–2018) and a more recent period (1950–2018) at different temporal (annual and seasonal scales) and different spatial scales (national and sub-regional scales). Results show that the patterns of change during the two periods are very similar. First, on the annual basis, we find an overall increase in the total annual precipitation, frequency of wet days, and intensity of precipitation in both periods in the CONUS, with percentages of stations showing significant increasing trends significantly larger than what can be expected by chance. Second, stations with significant increasing trends are mainly concentrated in eastern CONUS, while stations with decreasing trends are located on the west coast and partial southeast coast. Specifically, the amounts and frequencies of light, moderate, and heavy precipitation mostly have significantly increased at more than 10% of stations. In both periods, there is a non-uniform change for three intensity categories of precipitation, with the frequency and total amount of events with higher intensity showing a larger rate of change, resulting in the smaller contribution of light precipitation to annual total precipitation but larger contribution due to heavy precipitation. Such non-uniform changes can also be observed in most sub-regions and seasons. Moreover, the estimated sensitivities of the amount of light, moderate, heavy precipitation, and heaviest precipitation event to global surface temperature increase for the 1900–2018 period is comparable with that for the 1950–2018 period, indicating that sampling period does not have a substantial effect on the scaling relationship between the amount of different precipitation events and global mean temperature.

本研究使用长期（1900-2018 年）和最近时期（1950-2018 年）的高质量记录检查美国本土 (CONUS) 每日降水特征（数量、频率、强度）的变化在不同的时间（年度和季节尺度）和不同的空间尺度（国家和次区域尺度）。结果表明，两个时期的变化模式非常相似。首先，在年度基础上，我们发现美国大陆两个时期的年总降水量、雨天频率和降水强度总体增加，显示显着增加趋势的站点百分比显着大于预期机会。其次，增加趋势明显的台站主要集中在美国大陆东部，而呈下降趋势的站点则位于西海岸和部分东南海岸。具体而言，小、中、强降水的数量和频率大多在10%以上的站点显着增加。两个时期, 三个强度类别的降水变化不均匀, 强度较高的事件发生的频率和总量变化率较大, 导致小降水对年总降水的贡献较小但较大强降水的贡献。在大多数次区域和季节也可以观察到这种不均匀的变化。此外，估计的轻、中、强降水量的敏感性，