Climatological relationships among the moisture budget components and rainfall amounts over the Mediterranean based on a super-high-resolution climate model

Fengjun Jin*, Akio Kitoh, Pinhas Alpert

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Moisture budget components over a rectangular region defined by the longitudes 6.0°W-36.0°E and latitudes 30.0°N to 45.0°N, with an area of about 6.08 × 106 km2 over the Mediterranean (Med) Basin, are studied by the use of the Japan Meteorological Agency super-high-resolution (20 km) GCM monthly mean data. The research time periods are 1979-2007 for current run and 2075-2099 for future run. Six rainy months of October to March with a total of 168 months for the current run and 144 months for the future run were selected. The rain months have been categorized into five groups of months based on the mean monthly rainfall amounts where the five groups are P < 1.0, 1.0 ≤ P < 1.5, 1.5 ≤ P < 2.0, 2.0 ≤ P < 2.5, and 2.5 mm/d ≤ P. We found that generally, over the Mediterranean, the outflow-inflow is balancing the independently calculated evaporation- precipitation quite well with a correlation coefficient of about 0.89. The present seasonal (October-March) precipitation simulated from the 20 km GCM showed a quite reasonable agreement with the CRU. The seasonal area mean precipitation and evaporation are 1.85 mm/d and 2.44 mm/d, respectively. The largest two precipitation categories contribute over 50% of the total seasonal rainfall. The evaporation varies positively with the precipitation for all precipitation categories. Also, the relatively high mean recycling ratio (55%) indicates that the local Med evaporation has a central role in the local precipitation. Another important finding is that the decreasing trend of recycling ratio with the rising of the precipitation category implies that the outside moisture inflow role increases with the increase of the precipitation category. For all the precipitation categories, the total outflow is larger than the total inflow, indicating that the Med area is an important source of moisture. Individual boundary moisture flux shows that the main moisture comes from the west boundary and contributes 59% of the total inflow, while the main outflow is through east boundary and is responsible for 46% of total outflow. Analysis of monthly precipitation indicates that the October and November have the two largest amount of precipitation over the research region. The moisture budget study separated for the east and the west Med shows that the area mean precipitation for the east and the west Med are 2.14 and 2.29 mm/d, while the evaporation are 4.48 and 3.59 mm/d. The plausible reason for the differences between these two basins has been discussed. The moisture supplies to the east Med is mainly from the west boundary, while for the west Mediterranean, the north boundary inflow also plays an important role along with the west boundary. The future moisture budget components over Med suggest that the precipitation is decreasing from 1.85 to 1.62 mm/d and the evaporation is increasing from 2.44 to 2.56 mm/d between current and future. Another finding is that the largest precipitation number of months decreases from 12% to only 6% of the total number of months, while the intensity of the precipitation in this category enhances in the future.

Original languageEnglish
Article numberD09102
JournalJournal of Geophysical Research C: Oceans
Issue number9
StatePublished - 2011


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