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.
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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
Soil Water - Climate interactions
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