The heat wave of June 2007 in Athens, Greece – Part 2: Modeling study and sensitivity experiments

In the frame of this paper a heat wave that resulted in record high temperatures in Athens Greece is analysed. Namely the analysis focuses in the ability of three widely used planetary boundary layer parameterisations to reproduce the heat wave temperatures. The simulations were performed with the Pennsylvania State University – National Center for Atmospheric Research MM5 model that is also used for operational weather forecasting at the National Observatory of Athens since 2002. The 2-m temperature at a grid increment of 1-km over the highly complex terrain of the Athens Area is statistically verified against the available surface station observations. The results of the analysis showed that the two nonlocal schemes, namely Blackadar and MRF succeeded much better than the local scheme ETA to reproduce the heat wave 2-m temperature although they considerably underestimated the maximum observed temperatures. In addition, it was found that the model grid points characterised by “urban” land-use provided better statistical verification results, with reduced cold bias. Further, in order to study the role of the initial skin temperature conditions on the 2-m temperature forecasts, satellite observed skin temperatures have been used to initialise the high resolution simulations. This sensitivity test showed that when using the satellite observed skin temperature in the model initial conditions, the simulation of the 2-m temperature is positively affected during the early stages of the simulation while later on the model physical parameterisations are decisive for the time evolution of temperature.