Patterns of Precipitation and Convection Occurrence over the Mediterranean Basin Derived from a Decade of Microwave Satellite Observations

Abstract

Abstract:The Mediterranean region is characterized by its vulnerability to changes in the water cycle, with the impact of global warming on the water resources being one of the major concerns in social, economical and scientific ambits. Even if precipitation is the best-known term of the Mediterranean water budget, large uncertainties remain due to the lack of suitable offshore observational data. In this study, we use the data provided by the Advanced Microwave Sounding Unit-B (AMSU-B) on board NOAA satellites to detect and analyze precipitating and convective events over the last decade at spatial resolution of 0.2° latitude × 0.2° longitude. AMSU-B observation shows that rain occurrence is widespread over the Mediterranean in wintertime while reduced in the eastern part of the basin in summer. Both precipitation and convection occurrences display a weak diurnal cycle over sea. In addition, convection occurrences, which are essentially located over land during summertime, shift to mostly over the sea during autumn with maxima in the Ionian sub-basin and the Adriatic Sea. Precipitation occurrence is also inferred over the sea from two other widely used climatological datasets, HOAPS (Hamburg Ocean Atmosphere OPEN ACCESSAtmosphere 2014, 5 371Parameters and Fluxes from Satellite Data) and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis interim (ERA-Interim). There is generally a rather fair agreement between these climatologies for describing the large-scale patterns such as the strong latitudinal gradient of rain and eastward rain signal propagation. Furthermore, the higher spatial resolution of AMSU-B measurements (16 km at nadir) gives access to mesoscale details in the region (e.g., coastal areas). AMSU-B measurements show less rain occurrences than HOAPS during wintertime, thereby suggesting that some of the thresholds used in our method might be too stringent during this season. We also observed that convection occurrences in ERA-Interim are systematically lower than those derived from AMSU-B. These results are potentially valuable to evaluate the rainfall parameterization in weather and climate models and to constrain ocean models.

Review Article: Atmospheric conditions inducing extreme precipitation over the eastern and western Mediterranean

“…While there is less variability over the sea. Alhammoud et al (2014) found a maximum frequency of deep convection over the MB in September-October and a minimum one in June and July, which is consistent with Funatsu et al (2009) and Melani et al (2013).…”

“…Some of these regions coincide with areas characterized as being vulnerable to heavy precipitation that induces floods over the MR (Harats et al, 2010). Claud et al (2012) and Alhammoud et al (2014) have extended the data set using measurements from the AMSU-B and the Microwave Humidity Sensor instruments onboard additional NOAA satellites. They found that interannual variability of deep convection is strongest along the northern coasts of the MB.…”

Application of logistic regression to simulate the influence of rainfall genesis on storm overflow operations: a probabilistic approach

“…The physics of the phenomenon is complex and depends on the dynamics of rainfall, the changes in rainfall over time, and the characteristics of urban catchment areas with storm overflows. Currently, the annual number of overflows in the catchment areas can be assessed based on long-term observations of their operation (Price, 2000;Andrés-Doménech et al, 2010;Gamerith et al, 2011), but it is a costly solution due to the need for the continuous monitoring of flows. An alternative approach is to build a hydrodynamic model of the catchment, which requires detailed data about the basin, precipitation from a long period (30 years according to the German Association for Water, Wastewater and Waste's (DWA) standard DWA-A 118E, 2006) and flows to calibrate the model from a period of at least 2 years (Szeląg et al, 2016).…”

An inverse method to derive surface fluxes from the closure of oceanic heat and water budgets: Application to the north‐western Mediterranean Sea

“…A similar conclusion was reached by Alhammoud et al . [] who noted that rainfall and specially convective rainfall in ERA‐INTERIM over the Mediterranean Sea were systematically underestimated compared to microwave satellite retrievals. The large dispersion between NWPM, both for heat and water fluxes, suggest the importance of errors and drift affecting model runs, when ocean models are forced with atmospheric NWPM flux fields without any correction [e.g., Sanchez‐Gomez et al ., ; Valdivieso et al ., ].…”