The Development of the DAPHNE Conceptual Model for the Potentiality of Designing a Precipitation Enhancement Project in Thessaly, Greece

The project DAPHNE aims at tackling the problem created from the impact of climate change and the continued increase in water needs for urban and agricultural use, which have largely exhausted the water supplies in the most vital agricultural area of Greece, Thessaly, by means of Weather Modification. The main objective is the development of a conceptual model, through the necessary scientific tools, to support the potentiality and applicability of a well designed precipitation enhancement program, to investigate its importance and assess thoroughly the impact of its implementation on the environment. Besides developing and applying state-of-the-art modeling tools, the project objectives are accomplished by performing measurement campaigns. During the experimental phase of the project, cloud seeding experiments take place on suitably chosen appropriate clouds over Thessaly area.

The database of the project DAPHNE includes surface and upper air observations and gridded analyses, weather radar images from a C-band weather radar, specially equipped aircraft measurements, gridded projections of regional climate models for the period 2041-2050 and chemical samples of soil and water from the seeded and unseeded areas, for environmental impact assessment studies.

The project DAPHNE integrates all contemporary components in order to have the most comprehensive state-of-the-science results. These components include the use of the state-of-the-art Weather Research and Forecasting (WRF) numerical model at very high resolution (1km x 1km), considering the different types of hydrometeors through sophisticated microphysical parameterizations, the adaptation and redevelopment of a 3D cloud model for performing simulations of seeding material dispersion and high-performance seeding aircraft. It is the first time that these state-of-the-art tools and aircraft observations are combined in order to create the fundamental principles for the development of the Conceptual Model that define the feasibility potential of a rain enhancement program in Thessaly. The conceptual model will define if, when, where and how a precipitation enhancement program would be applicable over the examined area. It sets the spatial, temporal and meteorological conditions that must be met, so as cloud seeding of appropriate cloud types will be feasible, aiming in precipitation enhancement and mitigation of drought in the area of Thessaly.

The non hydrostatic WRF model with the Advanced Research (WRF-ARW) dynamic solver is installed on a parallel computing platform (cluster) and all the necessary pre and post-processing modules have been created. It was configured using telescoping nesting and focusing in the area of interest. Three interactive model domains (2-way nested) cover Europe, Greece and the wider area of Thessaly, at horizontal grid-spacing of 15kmx15km, 5kmx5km and 1kmx1km, respectively, utilizing the staggered Arakawa C grid. Fine-resolution data (30”x30”) were used in the definition of topography and land use. The selected microphysical scheme (WSM6) contains separate variables for the calculation of cloud water, rain water, ice, snow and graupel.

The WRF model is used to produce very high spatiotemporal resolution simulations of the atmospheric conditions in the area of interest and provide the forcing fields to the 3D cloud model, which is applied to representative cases of past/present-weather and future projected conditions, using the actual radiosonde data and the output of the WRF simulations. The cloud model sensitivity to the different sources of input data (radiosonde, WRF) is assessed for the present-weather cases. Storm characteristics are obtained and identified from weather radar reflectivity images received and analyzed from the C-band weather radar, being located within the area of interest. The cell tracker TITAN has been used to retrieve convective storm tracks and characteristics from radar reflectivity measurements that roughly have 750x750m spatial and 3.5min temporal resolution. The storm characteristics include: initiation time, duration, direction, speed, volume, area and precipitation area, rain rate, maximum reflectivity, cloud top and many more parameters.

The prevailing synoptic conditions in the greater area of central Greece, during the 10-year period 2001-2010, have been classified, one by one day, according to the general circulation pattern of the middle troposphere. This information was retrieved by daily analyses of ECMWF at 500 hPa at 1200 UTC. The classification methodology procedure was also adopted for the mid-tropospheric synoptic circulation patterns, projected by RegCM3 regional climate model, under the IPCC scenario A1B, during the period 2041-2050. The resulting daily synoptic circulation patterns are statistically analyzed and compared, in order to investigate the prevailing near-present and future synoptic conditions. To meet the project objectives, representative cases of the near-present and future synoptic conditions are selected for the model simulations.

The core experimental work, during the measurement campaigns, incorporate surface and upper air meteorological measurements, weather radar images and aircraft flights, conducted by specially instrumented and equipped aircrafts, with specialized on the subject pilots, in order to perform in-situ measurements. At the same time, and after meeting pre-specified criteria, cloud seeding experiments are carried out on selected clouds. Chemical samplings of soil and water from the seeded area are conducted, in order to perform the impacts study analysis. Sampling from background areas are also take place for comparison purposes.

It is believed, that it is for the first time that all these state-of-the-art tools and aircraft observations are combined, in order to create the necessary fundamental principles for the development of the Conceptual Model that will define the feasibility potential and applicability of a rain enhancement program in Thessaly. The conceptual model will define -if, when, where and how- a precipitation enhancement program would be applicable over the examined area. It sets the spatial, temporal and meteorological conditions that must be met, so that cloud seeding of appropriate cloud types will be feasible, aiming in precipitation enhancement and mitigation of drought in the area of Thessaly.

Acknowledgments This research work of DAPHNE project (contract number 11SYN-8-1088) is co-funded by the European Union (European Regional Development Fund) and Greek National Funds, through the action "COOPERATION 2011: Partnerships of Production and Research Institutions in Focused Research and Technology Sectors" in the framework of the operational programme "Competitiveness and Entrepreneurship" and Regions in Transition (OPC II, NSRF 2007-2013).