Comment on “Five Decades of Observed Daily Precipitation Reveal Longer and More Variable Drought Events Across Much of the Western United States”
Changes in precipitation patterns with climate change could have important impacts on human and natural systems. Zhang et al. report trends in daily precipitation patterns over the last five decades in the western United States, focusing on meteorological drought. They report that dry intervals (calculated at the annual or seasonal level) have increased across much of the southwestern U.S., with statistical assessment suggesting the results are statistically robust. However, Zhang et al. preprocess their annual (or seasonal) averages to compute 5-year moving window averages before using established statistical techniques for trend analysis that assume independence about some fixed trend. Here we show that the moving window preprocessing violates that independence assumption and inflates the statistical significance of their trend estimates. This raises questions about the robustness of their results. We conclude by discussing the difficulty of adjusting for spatial structure when assessing time trends in a regional context.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE; USDOE Office of Science (SC), Biological and Environmental Research (BER). Earth And Environmental Systems Science (EESS)
- Grant/Contract Number:
- AC02-05CH11231; DE‐AC02‐05CH11231
- OSTI ID:
- 2278732
- Alternate ID(s):
- OSTI ID: 2278733; OSTI ID: 2283452; OSTI ID: 2337618
- Journal Information:
- Geophysical Research Letters, Vol. 51, Issue 1; ISSN 0094-8276
- Publisher:
- American Geophysical Union (AGU)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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