Hellenic Center for Marine Research - Institute of Inland Waters

PreWec Marie Curie Excellence Research Team






Summary of Research

In relation to the project’s first subject area (hydrometeorology), we have investigated the effect of forcing the land surface cheme of an atmospheric mesoscale model with remotely sensed precipitation datasets. The goal of this research is to provide improved surface conditions for the atmospheric model in order to achieve accurate simulations of the mesoscale circulations that can significantly affect timing, distribution and intensity of convective precipitation. Results from this work have been published in Advances in Water Resources. Several presentations
on various aspects of the herein work have been made by members of the team. This work has formulated the Ph.D. topic of ESR team member E. Serpertzoglou (to be completed in 2011).
Secondly, we have investigated the use of satellite rainfall for hydrological applications. This research focuses on three hydrological problems: the prediction of flash floods in complex terrain environment, estimation of soil moisture variability for model initialization and the prediction of large-scale floods for major river basins. Specifically, we

(i) carried out a data-based numerical experiment in order to understand the scale relationships of the error propagation of satellite rainfall for flood evaluation applications in complex terrain basins;
(ii) investigated the sensitivities of runoff generation to rainfall variability and initial wetness conditions for a major flash flood event that occurred during August 29, 2003 on the upper Tagliamento river basin in the eastern Italian Alps;

(iii) investigated the potential use of high resolution satellite precipitation products for simulating a major flash flood event over a complex terrain basin in Northeastern Italy, and (iv) conducted data-driven numerical experiments based on a satellite rainfall error model applied on different satellite rainfall products available at various spatio-temporal resolutions. Results from this work are published in five journal articles (three in the Journal of Hydrometeorology, one in the IEEE Transactions on Geosciences and Remote Sensing and one in the Journal of Hydrology) and two book chapters. Several presentations on various aspects of the herein work have been made by members of the team.
This work has formulated the Ph.D. topic of ESR team member E. Nikolopoulos (defended in April 2010).
Thirdly, we advanced underwater acoustical monitoring of sea environment. Specifically, we developed a new technique for quantifying rainfall and wind speed over oceans through the sound produced by rainfall and wind-induced waves underwater. We developed an acoustic recorder and completed processing data from an experiment combining deep underwater acoustic recordings of rainfall with high-resolution weather radar. Analysis of the data has shown that the signal from rainfall is easily detected under a variety of wind and noise conditions, and it is robust at depth. Moreover, we show that underwater sound signal contains a wealth of information that can be used to quantify a number of other sources beyond rain and wind (e.g., underwater gas emissions, shipping, biological activity, underwater landslides, etc.). Results from this work are published in three journal articles (Nuclear Instruments and Methods in Physics Research, Sea Technology Magazine and IEEE Transaction of Geosciences and Remote Sensing). Several presentations on various aspects of the herein work have been made by members of the team.


The last subject of this task was to investigate how significant is the effect of high-resolution topographic data on simulating the hydrologic response during complex terrain flash-flood events. The study was presented at AGU and is under preparation for submission to CATENA journal.

In relation to the project’s second subject area (coastal ecosystem/pollution), an extensive field measurement and monitoring program was performed under Dr. Tzortziou’s leadership, focusing on water resources, pollution pressures, inland and coastal water quality and relations to hydrologic conditions, biogeochemical processes, and anthropogenic influences. Among our objectives was assessing the major pollution pressures in the studied systems and examine the effects of anthropogenic activities and changes in watershed characteristics on the sources, composition, and cycling of carbon and nutrients along the continuum of river, wetland, and coastal zone. A comprehensive and detailed database (i.e. physico-chemical, optical, biological, biogeochemical, hydrological parameters) has been created, which fills critical gaps in current knowledge related to the sources, transformation and fate of organic compounds, nutrients and pollutants in coastal E. Mediterranean ecosystems. Our results show that, although the Mediterranean Sea is an extremely oligotrophic region, organic carbon and nutrient amounts in E. Mediterranean coastal wetlands can reach high values, of the order of those typically measured in highly eutrophic, optically complex, estuarine systems. The composition, properties and dynamics of dissolved organic matter (DOM) and the various biogeochemical processes taking place within the studied river and wetland systems under different hydrological conditions are discussed in two under preparation journal manuscripts (by Tzortziou et al. and Zeri et al.).

Our measurements in Evros, Sperchios, Louros, Arachthos, and Evrotas rivers highlighted the use of fluorescence spectroscopy as an effective monitoring tool for pollution detection and control of industry impacts on river systems. Our chemical analyses provided new data and information on the sources, quality, and elemental, isotopic and molecular composition of DOM in E. Mediterranean catchments. We found that intensive industrial and agricultural activities and extensive use of N based fertilizers and organophosphoric insecticides in the Evros basin result in waters enriched in DOC, DON, and DOP concentrations. Elevated inorganic nitrogen loads in Evros River originating either from agricultural runoff (mainly as NO3-) and/or from anthropogenic inputs (mainly as NH4+), give rise to substantial autotrophic production, especially during summer months with low water flow. Our water monitoring program in the Ervos basin was applied to assess the environmental status in the Greek part of the river and
identify associated pollution pressures. Potential land use hazards were mapped and estimated pollution risks were evaluated. These are discussed in two submitted manuscripts by Dimitriou et al. Finally, results from our work in this task have been presented in several conference presentations.In relation to the project’s third subject area (climate change), first, we investigated the impact of precipitation and canopy water storage sub-grid variability on climate model simulations. The team has shown that including sub-grid variability reduces the interception loss and increases the plant transpiration, with the total evapotranspiration (latent heat flux) staying more or less the same. In their results the team regionally averaged precipitation increases by 0.59 mm per day for Central Africa and 0.52 mm per day for Amazonia when the sub-grid variability is considered in the model. This increased moisture convergence and enhancement of atmospheric instability explains the seeming discrepancy between increased precipitation and unchanged evapotranspiration over tropical regions. The second subject of this task was to explore the effects of dynamic vegetation on climate prediction over the Mediterranean region using a linked regional climate-vegetation model. Regional simulations of future climate show that including effects of structural changes in vegetation reduces the warming by 2°K and modifies the precipitation decrease to a 4% increase. The third subject was the development of a model torepresent the interactions between surface and groundwater at the regional scale and to study the effects on water cycle parameters and the surface energy budget at regional scale. The last subject examined the characteristics of open-sea areas in the Mediterranean region with respect to the water vapor variability. It is found that Eastern basin presents distinct, well marked regional characteristics, namely a stronger seasonal cycle of relative humidity and dryer upper troposphere during summer. Differences in the seasonal variability of relative humidity between the maritime and coastal environments are found. Our results show that generally, coastal profiles describe reasonably well the open-sea conditions for winter months, characterized by low synoptic variability. Results from this work are described in five journal articles (Climate Dynamics, ADGEOS, J. of Climatology, J. of Hydrology and Atmospheric Research) and
several conference presentations.













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