Combined Analysis of a convective precipitation event in Athens, Greece, by utilizing the H03B product of EUMETSAT HSAF and ground-based OTT PARSIVEL Laser-based optical Disdrometer measurements

The assessment and interpretation of an extreme hydrometeorological event and the consequent impacts such as flash floods, especially within urban environment, is of high interest, especially in the Anthropocene era. Global warming intensifies Urban Heat Island resulting in local intense convective precipitation over a densely urbanized area.  Urbanization on one hand, increases the sensible heat flux  and transports more water vapor, mixing it into the upper atmosphere and on the other hand, increases the surface roughness and as a consequence mechanical turbulence drives low-level convergence resulting in enhanced intensity and frequency of convectional extreme precipitation (Nastos and Zerefos, 2007; Li et al., 2023).

In this study, we focus on an extreme summer convective event on August 24, 2022, in Athens, Greece, where the precipitation intensity reached instantly 116 mm/h and the visibility was limited to 600m. More specifically, we analyzed and compared the H03B product of EUMETSAT Hydrology Satellite Applications Facility (HSAF) with the ground-based OTT PARSIVEL Laser-based optical Disdrometer measurements.

Product H03B is based on the infrared (IR) electromagnetic spectrum from the SEVIRI instrument on board of Meteosat Second Generation satellites. The product is generated at the 15-min imaging rate of SEVIRI, and the spatial resolution is consistent with the SEVIRI pixel. Precipitation is obtained by combining IR equivalent blackbody temperatures at 10.8 μm with rain rates from polar microwave measurements.

OTT PARSIVEL Disdrometer is ideal for simultaneous measurement of PARticle SIze and VELocity of all liquid and solid precipitation. It detects and identifies 8 different precipitation types as drizzle, mixed drizzle/rain, rain, mixed rain/snow, snow, snow grains, freezing rain and hail. Besides, it provides drop size distributions on the ground and a function to derive a local Z/R relation – ready to be used to adjust the radar data.

The findings of the combined analysis showed that, towards early warning of convective precipitation in urban areas, combined high temporal resolution measurements carried out by satellites and ground based disdrometer measurements could provide a high-performance regional early warning system.

Keywords: extreme convective precipitation, EUMETSAT HSAF, PARSIVEL, rain rate, Athens

Acknowledgement: This work is co-financed by Iceland, Liechtenstein, Norway European Economic Area (EEA) Grants 2014 – 2021 and Greek Public Investments Program.

References:

• Panagiotis T. Nastos, Christos S., Zerefos (2007), On extreme daily precipitation totals at Athens, Greece. Advances in Geosciences10, DOI: 5194/adgeo-10-59-2007
• Chenxi Li, Xihui Gu, Louise J. Slater, Jianyu Liu, Jianfeng Li, Xiang Zhang, Dongdong Kong (2023), Urbanization-Induced Increases in Heavy Precipitation are Magnified by Moist Heatwaves in an Urban Agglomeration of East China. Journal of Climate, 36 (2), 693–709, DOI: https://doi.org/10.1175/JCLI-D-22-0223.1