Abstract
Local air-sea interaction over the Mediterranean may amplify the effects of climate change. This study investigates the sensitivity of simulations of two different high impact weather events to changes in the specification of sea surface temperature (SST) using a regional atmospheric model. First we assess the impact of specifying SST from two reanalysis data sets with differing spatial resolution. The simulated tropical-like cyclone (TLC) is slightly stronger in the case of the lower resolution SST which is warmer over the formation region, most notably in the maximum rainfall which is ~7% higher. The differences in the two explosive cyclone simulations are negligible, most likely due to intensification occurring mainly over land. We then test the sensitivity of the storms to a range of SST anomalies. The TLC showed a clear trend of increasing storm intensity as SST rises. These results suggest that SST plays a direct role in determining the intensity of the storm. For the explosive cyclone there is no clear trend in dynamical intensity except for the highest warming anomalies. However, the rainfall increases with the magnitude of the SST anomaly. Our results suggest that extreme weather events over the Mediterranean will become more extreme if SST increases as the climate warms, assuming that upper air conditions do not change.
Highlights
The Mediterranean region is unique in many ways
Our goal is to examine the sensitivity of simulations of case studies of a tropical-like cyclone and an explosive cyclone to the specification of sea surface temperature (SST) by using regional atmospheric model forced with high spatial resolution SST data as compared to the lower resolution fields typically included in reanalysis data sets
We present the results from the “climate change” scenarios in which the more detailed Mediterranean Forecasting System (MFS) SST field is used as the reference run and 10 sensitivity simulations with the SST across the Mediterranean changed in increments of 1 ◦C ranging from −5 ◦C to +5 ◦C
Summary
The Mediterranean region is unique in many ways. It is characterized by a Mediterranean climate type with hot, dry summers and cool wet winters. While the Mediterranean Sea is small relative to the large ocean basins where the most intense storms are frequently formed, the unique combination of the geographical and climate factors leads to the frequent occurrence of high impact weather events such as intense cyclones, strong winds, heavy precipitation and flooding in the cool season as well as prolonged heat waves in summer and multiyear droughts [1] Two such processes which are the focus of this paper are (1) Mediterranean hurricanes (medicanes), which are tropical-like cyclones (TLC) and (2) meteorological bombs or bomb cyclones, which are referred to as explosive cyclogenesis.
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