The Annual March of Precipitation in Arizona, New Mexico, and Northwestern Mexico
AuthorBryson, Reid A.
AffiliationInstitute of Atmospheric Physics, The University of Arizona
KeywordsPrecipitation (Meteorology) -- Arizona.
Precipitation (Meteorology) -- New Mexico.
Precipitation (Meteorology) – Mexico.
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AbstractThis report is concerned with the annual march of monthly precipitation amount in an area comprising the states of Arizona, New Mexico, Sonora, Sinaloa, Durango, and western Chihuahua. Fourier analysis was used to reduce the twentyyear mean monthly values to six harmonic terms, four of which were then plotted on charts and studied. The results of this study indicate that an area consisting largely of the Sierra Madre Occidental in northwestern Mexico, and the portion of Arizona southeast of Tucson constitute a single rainfall province with a strong summer maximum of rainfall. This province also has a winter maximum but only in Arizona does the semi-annual term exceed the annual in amplitude. Within the United States the Gila and Rio Grande valleys constitute rainfall provinces of internally similar annual march, while the upland areas tend to resemble the Pacific coastal pattern to the west.
Series/Report no.University of Arizona, Institute of Atmospheric Physics, Technical Reports on the Meteorology and Climatology of Arid Regions, No. 6
SponsorsThe work reported herein is part of a study supported by the Alfred P. Sloan Foundation
Except where otherwise noted, this item's license is described as Public Domain: This material has been identified as being free of known restrictions under U.S. copyright law, including all related and neighboring rights.
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Exploring trends in wet-season precipitation and drought indices in wet, humid and dry regionsFunk, Chris; Harrison, Laura; Alexander, Lisa; Peterson, Pete; Behrangi, Ali; Husak, Greg; Univ Arizona, Dept Hydrol & Atmospher Sci (IOP PUBLISHING LTD, 2019-10-29)This study examines wet season droughts using eight products from the Frequent Rainfall Observations on GridS database. The study begins by evaluating wet season precipitation totals and wet day counts at seasonal and decadal time scales. While we find a high level of agreement among the products at a seasonal time scale, evaluations of 10 year variability indicate substantial non-stationary inter-product differences that make the assessment of low-frequency changes difficult, especially in data-sparse regions. Some products, however, appear more reliable than others on decadal time scales. Global time series of dry, middle, and wet region standardized precipitation index time series indicate little coherent change. There is substantial coherence in year-to-year variations in these time series for the better-performing products, likely indicative of skill for monitoring variations at large spatial scales. During the wet season, the data do not appear to indicate widespread global changes in precipitation, reference evapotranspiration (RefET) or Standardized Precipitation Evapotranspiration Index (SPEI) values. These data also do not indicate a global shift towards increasing aridity. Focusing on SPEI values for dry regions during droughts, however, we find modest increases in RefET and decreases in SPEI when wet season precipitation is below normal. Dry region SPEI values during droughts have decreased by −0.2 since the 1990s. The cause of these RefET increases is unclear, and more detailed analysis will be needed to confirm these results. For wet regions, however, the majority of products appear to indicate increases in wet season precipitation, although many products perform poorly in these regions due to limited observation networks, and estimated increases vary substantially. Synopsis: Our analysis indicates a lack of increasing aridity at global scales, issues associated with non-stationary systematic errors, and concerns associated with increases in reference evapotranspiration in global dry regions during droughts.