Land-Atmosphere Coupling Investigated Across Scales

Abstract:

Investigations of land-atmosphere coupling have shown that surface conditions can influence local boundary layer development and precipitation likelihood across local to regional scales from subdaily to seasonal time scales. Observational techniques utilized for land-atmosphere coupling metrics vary greatly in spatial and temporal scale. When assessing metrics derived across a variety of resolutions, it is important to consider the influence of spatial and temporal resolution on the observations and model output. This study analyzes a recently-developed coupling metric across a variety of spatio-temporal resolutions. High frequency, small footprint eddy covariance tower data and lower frequency, lower resolution MODIS satellite products are both used to quantify a time series of the metric of coupling strength. The time series are decomposed using wavelet analysis, and spectra are investigated in order to determine the temporal scales associated with strong coupling and to consider how coupling strength varies with the scale of observation. In addition, the underlying atmospheric and surface properties are investigated to assess the relative contribution to the overall coupling between the land-atmosphere interface. As soil moisture memory can play a large role in coupling strength, extreme dry and wet conditions are categorized and investigated separately to see how the dynamics of coupling on a local and a regional scale may cause feedbacks promoting continued wet conditions or exacerbating drought.