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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #422207
Research Project: Improving Resiliency of Semi-Arid Agroecosystems and Watersheds to Change and Disturbance through Data-Driven Research, AI, and Integrated Models

Location: Water Management and Systems Research

Title: Surface boundary layer stability and meteorological drivers of temporal microclimate variability in a semiarid grassland

Author
item Barnard, David
item JACOB, MACDONALD - Colorado State University
item Erskine, Robert
item Green, Timothy
item Mahood, Adam
item Gleason, Sean

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2025
Publication Date: 7/9/2025
Citation: Barnard, D.M., Jacob, M., Erskine, R.H., Green, T.R., Mahood, A.L., Gleason, S.M. 2025. Surface boundary layer stability and meteorological drivers of temporal microclimate variability in a semiarid grassland. Agricultural and Forest Meteorology. 372. Article e110723. https://doi.org/10.1016/j.agrformet.2025.110723.
DOI: https://doi.org/10.1016/j.agrformet.2025.110723

Interpretive Summary: Microclimates in fields respond to small-scale weather patterns and play a key role in how plants respond to environmental change. Landscape effects are important, but less attention has been given to the weather factors that drive microclimate variability. We found that even over short distances in a field, air temperature (up to 15°C) and relative humidity (up to 50%) varied a lot, especially between the high and low points on the field. Atmospheric stability, windspeed, and solar radiation were the main drivers of these variations, especially at night. As temperatures increase due to climate change, cool, sheltered areas in a field may become less stable, impacting plant growth and development. This also will add an important factor in site-specific precision crop management.

Technical Abstract: Microclimates are fine-scale departures from bulk conditions often attributed to static landscape characteristics and topography, but their temporal variability in response to dynamic meteorological conditions remains poorly understood. In this study, we deployed a network of air temperature (Tair) and relative humidity (RH) sensors across a small grassland watershed in northern Colorado, USA to assess microclimate variability, atmospheric stability and concurrent meteorological conditions. We found significant within-field spatial variability in Tair at 2 m fluctuating by >15 °C, RH by >50 %, and vapor pressure deficit by > 1 kPa at 15 min intervals. The mean Tair difference between the highest and lowest points in the watershed was 0.29 °C, or a near-surface lapse rate of 10 °C km-1, exceeding the free-air lapse rate of 6.5 °C km-1. Within-field variability was driven primarily by atmospheric stability (defined by Richardson number) and was highest during stable or inversion conditions when mechanical turbulence and convective mixing were low. These variations in Tair and RH scaled up to annual variability in biophysical metrics within the field, such as growing degree days and potential evapotranspiration, that exceeded 7 %. An inverse relationship between within-field Tair mean and variability suggests warmer temperatures in the future may minimize microclimates in similar areas with low topographic complexity to this study. This study advances knowledge by identifying important temporal dynamics in microclimates within a grassland field that vary with atmospheric stability. These dynamics should be incorporated into microclimate models and future studies investigating microclimate effects in ecological, hydrological, and agricultural applications.