Time Scales of Layered Soil Moisture Memory in the Context ofLand–Atmosphere Interaction

Abstract

Abstract The time scales of layered soil moisture memory in the Common Land Model (CLM) coupled with the National Center for Atmospheric Research Community Climate Model, version 3 (NCAR CCM3) have been examined using a 50-yr climate simulation. Such soil moisture memory has been characterized in terms of the spatial, seasonal, and vertical variations of 1-month-lag autocorrelation coefficients and the corresponding e-folding decay time scales. To understand this land memory mechanism, in terms of the variations that occur in the model, a cross-spectral analysis has been applied to the soil moisture profile with precipitation (P), runoff (R), evapotranspiration (ET), transpiration, and the residual of P − ET − R, respectively, together with an examination of the surface water budget of the annual cycle. These collectively provide physical insights on time scales of layered soil moisture memory in the context of land–atmosphere interaction. The major findings are: 1) soil moisture memory in warm climates c...