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

•We observed substantial variability in VPD, Tair, and RH in a small grassland watershed.•Within-field variability was greatest under stable atmospheric conditions.•Stability class and weather factors were essential to modeling variability.•Microclimates need to be reconsidered as temporally dynamic...

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Vydáno v:Agricultural and forest meteorology Ročník 372; s. 110723
Hlavní autoři: Barnard, David M, Macdonald, Jacob, Erskine, Robert H., Green, Timothy R., Mahood, Adam, Gleason, Sean M.
Médium: Journal Article
Jazyk:angličtina
Vydáno: Elsevier B.V 15.09.2025
Témata:
Atmospheric stability
Cold air drainage
Growing degree days
Potential evapotranspiration
Richardson number
Temperature inversion
Growing degree days
Potential evapotranspiration
Cold air drainage
Temperature inversion
Richardson number
Atmospheric stability
ISSN:0168-1923
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Shrnutí:•We observed substantial variability in VPD, Tair, and RH in a small grassland watershed.•Within-field variability was greatest under stable atmospheric conditions.•Stability class and weather factors were essential to modeling variability.•Microclimates need to be reconsidered as temporally dynamic. 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.
ISSN:0168-1923
DOI:10.1016/j.agrformet.2025.110723