Mineral dust aerosols are a key component of the Earth system, and a public health concern under 20^th and 21^st century climate change. The Southern Great Plains, including Texas, Oklahoma, Kansas, and adjacent areas in Colorado and New Mexico, is a potential source for future dust storms with forecast aridity, like during the 1930s Dust Bowl Drought (DBD). Dust storms in 1930s in this area occurred weekly with high atmospheric dust loads persisting for days and are associated with heightened occurrence of cardiorespiratory aliments. However, land to atmosphere interactions across the Great Plains with sustained high temperature conditions and drought are poorly constrained may be source of contribute to lower atmosphere dust loading. This research assessed land surface disturbance in DBD areas from the first generation of aerial photographs taken between 1934 and 1940. These images available in the National Archives were digitized, seamlessly mosaicked, grayscale corrected and geolocated for quantitative studies. Surface disturbance and removal of vegetation in the DBD area was primarily associated with currently stabilized sand dunes and flat sand sheet environments, which are common across the Great Plains. Previous studies have documented that on average only 30 to 40% of the DBD area was cultivated and as the drought progressed additional acreage was fallow. Largescale landform reactivation occurred with excessive heat (>95⁰ F) at the land surface and overlying atmosphere, drought intensity and reduced plant diversity.  The release of very small particles, a 100 times smaller than the width of single strand of hair, (called PM10 or 10 microns in size) for a DBD dust storm with winds >13 mph was 4700?41,610 μg m³/d, similar in magnitude to current dust storms from North Africa and East Asia. Visibility during these dust storms would be < 0.5 miles.

The meteorological catalysts for dust events and surficial dynamics for dust emission was evaluated from a new quantitative record of 20^th century dust storms in the DBD area. These observations were combined with 1930s Soil Conservation Service station reports, reanalysis of meteorological data, and field surveys using a Portable In-Situ Wind Erosion Laboratory (PI-SWERL). The PI-SWERL is a wind tunnel wrapped into a circle and simulates the stress of wind on a land surface with wind speeds from 5 to 55 mph and measures the production (or emission) of dust from the land surface. The PI-SWERL is an important field tool for measuring the dust emission potential from land surfaces.  A multivariate statistical analysis of amongst 22 environmental factors related to 1930s dust storms yield six principal components capturing~60% of the variance to explain the factors for dust event days. This analysis indicates that 1930s dust storms are mostly related to the seasonality (spring and winter) and extreme temperatures, rather than agricultural practice. This analysis indicates that extreme temperatures particularly in Spring and reduced surface moisture and vegetation cover are the principal causative factors for dust storms in the 1930s DBD. Comparatively, South Dakota had a higher area of cultivation and lower area of eolian sand deposits, suggesting that DBD dust storms in the Northern Great Plains were primarily derived from cultivated fields.

This research also characterized dust emission hotspots at White Sands, NM where gypsum dunes and the adjacent playa yield very high dust fluxes up to 8.3 mg/m²/s. In contrast, the active, quartz rich Monahans dunes, TX produce low dust fluxes up to 0.5 mg/m²/s, whereas adjacent stabilized sand sheet areas could produce some of the highest dust emissions at 17.7 mg/m²/s if reactivated. These findings have implications for present and future dust emission potential of eolian systems from the Great Plains to the southwestern United States with a changing climate.

Last Modified: 12/07/2022
Modified by: Steven L Forman