Obtaining the right diurnal cycle of both cloud cover and precipitation over land has been a longstanding issue in hydrology, meteorology and climate. This has however fundamental repercussion for the study and prediction of land-atmosphere interactions.

The difficulty of the representation of clouds over land compared to its oceanic counterpart is due to the large diurnal variability of the boundary layer induced by the diurnal solar heating of the surface. A better comprehension of shallow convection over land and its connection to the surface is a necessary step toward improved understanding and precipitation of cloud and precipitation processes over land.

There have been recent important developments in our understanding of shallow convection over the ocean through large eddy simulation (Siebesma et al. 2003) and conceptual, toy model, studies (Bretherton and Park 2008). Over the land our understanding based on large eddy simulation studies (e.g. Brown et al. 2002) but there remains gaps in our conceptual understanding of the processes over land.

We here present the first bulk model of land-atmosphere interactions able to resolve both shallow and deep convection and the transitions between the different regimes. This model provides a powerful framework for the study of local land-atmosphere interactions and the coupling between the surface-mixed layer-moist convection and ultimately with the precipitation processes.

Several cases along a East-West transect of the United States are discussed. in particular we highlight the dependence of cloud cover and rainfall on soil moisture for typical observed large-scale conditions taken from reanalysis products. The soil moisture-precipitation feedbacks are shown to be fundamentally different from the West to the East and depending on the synoptic conditions.

The framework presented here can be used in varying conditions to improve our understanding of land-atmosphere interactions from a physical and quantitative standpoint. >