Themis G. Chronis

Improving Convective Precipitation Forecasting through Assimilation of Regional Lightning Measurements in a Mesoscale Model

Abstract A technique developed for assimilating regional lightning measurements into a meteorological model is presented in this paper. The goal is to assess the effectiveness of cloud-to-ground (CG) lightning information for improving the convective precipitation forecasting. The main concept of the technique is that utilizing real-time location, timing, and flash-rate data retrieved from a long-range lightning detection network, a regional/mesoscale meteorological model is informed about the deep moist convection spatiotemporal development and intensity. This information is then used to nudge the model-generated humidity profiles to empirical profiles as a function of the observed lightning intensity. The empirical humidity profiles are assumed to be representative of convective regimes since they have been produced on the basis of atmospheric soundings obtained during thunderstorm days. Case studies from three thunderstorm developments in a warm-season environment over the Mediterranean are used to inv...

Evidence of Tropical Forcing of the 6.5-Day Wave from Lightning Observations over Africa

A study employing observations and climatic reanalysis data is concerned with links between convection and the well-documented 6.5-day stratospheric global wave. Observations from a long-range lightning detection network, known as ZEUS, reveal an in-phase behavior between the maximization of daily lightning activity over Africa and the intensification of the wave. To extend the observations on a climatological basis, the authors make use of the outgoing longwave radiation (OLR) as proxy for convection and the surface level pressure (SLP) as an indicator of atmospheric column forcing. Cross-spectral analysis shows significant peaks in coherency between OLR and SLP, apparent only over equatorial Africa and South America (Amazon basin), while strong coherency in this frequency band is absent over the Maritime Continent.

New receiver network advances long-range lightning monitoring

An experimental long-range lightning detection system (ZEUS) based on a network of six very low-frequency (VLF) receivers is being implemented and operated by the National Observatory of Athens and the University of Connecticut. The system hardware takes advantage of the latest computing technology signal processing algorithms, geographic positioning systems (GPS), and communications networking to improve the state-of-the-art in receiver design at long-range frequencies. The receivers are situated in six remote locations around Europe, selected for their low rates of manmade electric noise. The sites are near Birmingham, United Kingdom; Roskilde, Denmark; Iasi, Romania; Larnaka, Cyprus; Mt. Etna, Italy; and Evora, Portugal. Deployment of the ZEUS receivers was completed on 15 June 2001. Since then, lightning activities have been monitored with great detail and accuracy throughout Europe and its surrounding waters, and with lesser accuracy along the U.S. east coast and in west Asia and central Africa.

The Worth of Long-Range Lightning Observations on Overland Satellite Rainfall Estimation

Lightning is a physical phenomenon that was excessively deified and feared for centuries. Even in the progressive minds of the ancient Greek society lightning was considered as the inescapable wrath of Zeus, seeking to punish mankind. It was in the dawn of the 1750’s when Benjamin Franklin, the American philosopher and inventor, brought the lightning phenomenon to human proportions by relating it with atmospheric electricity. Years later, in the beginning of the 20

Understanding the Mediterranean Water Cycle: 3rd Hydrological Cycle in the Mediterranean Experiment (HyMEx) Workshop; Gouves, Heraklion, Crete, Greece, 1–5 June 2009

The Hydrological Cycle in the Mediterranean Experiment (HyMEx) project aims for better understanding and quantification of the hydrological cycle and related processes in the Mediterranean. The main goals of the 3rd HyMEx Workshop were to promote a synergistic approach to (1) provide an in-depth description of the Mediterranean water cycle, its variability, and trends; (2) understand how water cycle processes contribute to the regional climate; and (3) validate the regional oceanic, atmospheric, and hydrological models and suggest improved parameterizations.