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Theoretical arguments and modeling experiments suggest that heavy precipitation is expected to intensify in a warmer climate. These projections have been supported by observational evidence at the daily scale, whereas the lack of long-term subdaily records has limited the ability to conduct analyses at shorter durations. In this study, we address this research gap using the Hourly Precipitation Data (HPD) from the National Climatic Data Center (NCDC). Due to the presence of relatively large periods with missing observations, we first implement a procedure to reconstruct probable missing zeros using the Analysis of Record Calibration (AORC) hourly gridded product. After the reconstruction, we identify 1404 gages with more than 75% (median of 94%) of complete records in the period 1979-2019 that cover the continental U.S. with good density. We then perform trend test analyses on the hourly observations where, at each gage, (1) independent events are identified, (2) peak-over- threshold series above the 90th, 95th, and 99th quantiles are extracted, and (3) trend tests are performed on the annual frequency and mean intensity of the POT series. After accounting for field significance, we find that hourly heavy precipitation exhibits statistically significant trends that are increasing for the frequency (+1% - +2% every year) but decreasing for the intensity (- 0.4 mm/h - -1.8 mm/h every 10 years). This is true in most of the country, except for some areas in the Southwest and South regions. Analyses repeated with the signals aggregated at 2, 3, 6, 12, and 24 hours lead to similar patterns, although a lower number of statistically significant trends is found as the duration increases. Overall, the statistical evidence of the trends is higher when focusing on the frequency rather than the intensity of heavy precipitation, and it is reduced when considering higher quantiles likely because of the lower test power. The results of this study are useful for the validation of climate and atmospheric models and the incorporation of nonstationarities due to global warming in intensity-duration- frequency curves of extreme precipitation used for infrastructure design.
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Evidence of Emerging Increasing Trends in Observed Subdaily Heavy Precipitation Frequency in the United States
Abstract The magnitude and frequency of heavy precipitation are expected to increase under warming temperatures caused by climate change. These trends have emerged in observational records but with much larger evidence on a daily rather than a subdaily scale. Here, we quantify long‐term changes in heavy precipitation frequency in the United States using hourly observations in 1949–2020 from 332 gauges. We demonstrate that, when analyzed collectively, the frequencies of heavy precipitation at multiple durations from hourly to daily exhibit an increase that cannot be explained by natural climate variability. Upward trends are significant at ∼20%–40% of the gauges throughout the country except for the coastal western and southeastern regions, with higher percentages for longer durations. We also show that the frequency of hourly heavy precipitation has mainly grown after ∼2000, thus explaining the limited evidence of trends at the subdaily scale reported in past studies.
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- PAR ID:
- 10614159
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 52
- Issue:
- 12
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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