Trends in Orographic Rainfall over the Fertile Crescent

摘要

The author presents a precipitation climatology and its trend over the mountainous areas of the Middle East using the dense network rain-gauge observation data gathered by the APHRODITE project. Coastal and orographically induced precipitation zones are found in semi-arid regions, and those patterns are consistent with those observed by the Precipitation Radar of the Tropical Rainfall Measuring Mission. The author then uses 34-year monthly precipitation data over Turkey, Israel and Iran to show seasonal precipitation trends. There is a strong and significant decreasing trend over Turkey and Israel in winter, especially in January. Trends over Turkey differ from month to month, while general trends over Iran differ little from season to season. On the other hand, Iran has orographically characterized trends. Trends are affected by the mountain ridges and slopes of the Taurus, Anatolian, Zagros, Erboz and other ranges. Then she compares the trends at thirteen high stations paired with low stations under the same synoptic conditions for the winter season. Most station pairs showed decreasing trends in the ratio of precipitation at the high stations to that at the low stations. Exceptional cases, which showed increasing trends in the ratio, were observed in the easternmost part of the Taurus Mountains (north of Syria) and in the northwestern part of Turkey.