COMPARATIVE ANALYSIS OF SURFACE WINDS IN THE MID-CONTINENTAL UNITED STATES DURING SEVERE DROUGHTS IN THE 1950S AND 2010S

Over the last 86 years, the Mid-Continental United States of America (USA) has experienced several extreme droughts, which are frequently linked with increased dust storms and dust production in response to reduced vegetation and intensified surface wind speeds. While many studies have focused on the relationship between dust and drought via changes in land surface conditions, the extent to which surface winds may have changed during past droughts (and thus impacted dust emission) remains an open question.

This investigation examined surface wind speed behavior in the mid-continental USA between 1954 and 2016 to assess differences in wind speeds between severe drought and wetter periods and determine what climatic conditions may have influenced these changes. We examine distributions of hourly wind speed data from 87 meteorological stations in the Mid-Continental USA (25° to 49°N, 116° to 93°W) for two drought periods (1954-1956, 2011-2013) and two relatively wet periods (1983-1987, 1992-1998), as determined using the Palmer Drought Severity Index (PDSI). Wind speeds during the 1950s Southwest drought were significantly higher than all three other periods (p < 0.01; Mann Whitney test). In addition, monthly 50th and 90th percentile wind speeds during the 1950’s drought were 15% and 9% greater than those of the 2010s drought, respectively, most notable during Spring months (the season of greatest dust emission in the mid-continental USA). Composite patterns of sea-level pressure, temperature, and PDSI were used to compare the two drought and wet periods, as well as years with the five highest and five lowest average wind speeds.

This analysis revealed that ‘drought’ and ‘windy’ years had anomalously lower PDSI values and higher surface temperatures within the study region, which would make these periods more vulnerable to soil erosion and subsequent dust storms from high winds. However, the 1950s drought experienced substantially higher wind speeds than the 2010s drought in spite of strong similarities in regional surface temperature, surface pressure patterns, precipitation, and PDSI. This might suggest that land surface conditions and management practices rather than climatic changes have been responsible for regional decreases in surface winds.