Hellenic Center for Marine Research - Institute of Inland Waters

PreWec Marie Curie Excellence Research Team

Soil water – Climate Interactions

Soil water content (both at saturated and vadose zones) is an important component of the hydrological cycle, included in many land surface models used to provide a lower boundary condition for soil moisture, which in turn plays a key role in the land-vegetation-atmosphere interactions and the ecosystem dynamics. In regional-scale climate applications land surface models (LSM) are commonly coupled to atmospheric models to close the surface energy, mass and carbon balance. Because of the limited horizontal resolution, LSMs in these applications are used to resolve the averaged vertical fluxes of heat, water and carbon vertical fluxes accounting for the effect of vegetation, soil type and other surface parameters spatial distribution, but lack of adequate resolution prevents using them to resolve, or they neglect to parameterize, the horizontal sub-grid processes. Specifically, LSMs resolve the large-scale runoff production associated with infiltration excess and for sub-grid groundwater convergence and shallow water table, often through the TOPMODEL approach. Land surface models resolve the vertical moisture and heat fluxes in the vadose zone and the groundwater recharge by percolation, but they traditionally neglect the role of rivers, e.g. they neglect loosing streams effect and all the related lateral hydrological processes that redistribute the water lost by the rivers to the groundwater at larger large scales. Therefore, in terms of bulk reservoirs, all possible exchanges of water between atmosphere, surface, vadose zone and groundwater are accounted, but the water flux from the surface and the rivers to groundwater is not. Thus, the potential feedback of surface water on groundwater is typically neglected in regional simulations.

Figure 1: Effect of soil moisture redistribution on groundwater table depth in the Po valley (Northeast Italy)

Through the analysis of observed data on soil moisture from the Mesonet (Oklahoma Mesoscale Network) stations in Oklahoma (US) and MODIS derived land surface temperature derived from MODIS we show evidence that the regional scale soil moisture and surface temperature patterns are affected by the surface water, especially in correspondence of rivers. This is demonstrated based on simulations from a land surface model (i.e., the Community Land Model – CLM, version 3.5) that does not account for the feedback of surface water on groundwater. It is shown that the model cannot reproduce the observed soil moisture and temperature spatial patterns, and that the underlying mechanism is the reinfiltration of surface water to groundwater that directly explains the effect on soil moisture directly and, indirectly, the effect on surface temperature by. Specifically, we implement a parameterization of this mechanism in the TOPMODEL based runoff generation approach used in CLM. The modified model exhibits an ability to reproduce considerable fraction of the soil moisture spatial variability that relates to the river distribution at regional scale. The CLM with the new surface-groundwater interaction parameterization is used to evaluate impacts of the lateral hydrological processes on water cycle parameters and the surface energy budget at regional scale.

Predicting Floods With Distributed Hydrological Models

Using Satellite Data to Study Water Cycle Parameters

Measuring Rainfall Using Mobile Weather Radar

Measuring Rainfall over the Oceans Using Underwater Sound Data

Numerical Weather Prediction Air- Sea interactions

Coastal Ecosystem and Water Quality

Climate Research

Soil Water - Climate interactions