摘要 :
Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land br...
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Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land breeze-like circulation, which interacts with dominating westerlies and leads to an intense cloud formation over the sea ～10-20 km from the coastal line. As a result, most of the precipitation falls on the sea without reaching the land. At the same time the eastern Mediterranean region experiences a lack of freshwater. For investigating a possibility to shift the release of precipitation from sea to land, numerical simulations were performed using the Hebrew University 2-D cloud model and the 3-D Weather Research and Forecasting model, both operating with spectral bin microphysics, and the 3-D COSMO model of the German Weather Service applying a two-moment bulk parameterization for cloud physics. The respective results indicate that an increase in concentration of small aerosols leads to a delay in raindrop formation and fosters the formation of extra ice particles with low settling velocity. This ice is advected inland by the background wind. As a result, precipitation over land increases at the expense of precipitation over sea by 15%-20%. The spatial shift of precipitation from sea to land can be as large as 50-70 km depending on the wind speed of the background flow. These results suggest a new possibility to enhance precipitation in a particular region by cloud seeding with small aerosols.
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摘要 :
Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land br...
展开
Precipitation in the eastern Mediterranean takes place during the cold season, when sea surface temperature is higher than the land surface temperature by 5℃-10℃. This temperature difference leads to the formation of the land breeze-like circulation, which interacts with dominating westerlies and leads to an intense cloud formation over the sea ～10-20 km from the coastal line. As a result, most of the precipitation falls on the sea without reaching the land. At the same time the eastern Mediterranean region experiences a lack of freshwater. For investigating a possibility to shift the release of precipitation from sea to land, numerical simulations were performed using the Hebrew University 2-D cloud model and the 3-D Weather Research and Forecasting model, both operating with spectral bin microphysics, and the 3-D COSMO model of the German Weather Service applying a two-moment bulk parameterization for cloud physics. The respective results indicate that an increase in concentration of small aerosols leads to a delay in raindrop formation and fosters the formation of extra ice particles with low settling velocity. This ice is advected inland by the background wind. As a result, precipitation over land increases at the expense of precipitation over sea by 15%-20%. The spatial shift of precipitation from sea to land can be as large as 50-70 km depending on the wind speed of the background flow. These results suggest a new possibility to enhance precipitation in a particular region by cloud seeding with small aerosols.
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