A new long instrumental serie for the Etesian winds since 1877
Trabajo presentado en la EGU General Assembly 2016 (European Geosciences Union), celebrada en Viena del 17 al 22 de abril de 2016. The meteorological observations found in old ships’ logbooks have been recognized as a useful source of climatic information in periods and areas not covered by other so...
| Main Authors: | , , , , , |
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| Other Authors: | |
| Format: | Still Image |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | http://hdl.handle.net/10261/188717 https://doi.org/10.13039/501100003329 |
| Summary: | Trabajo presentado en la EGU General Assembly 2016 (European Geosciences Union), celebrada en Viena del 17 al 22 de abril de 2016. The meteorological observations found in old ships’ logbooks have been recognized as a useful source of climatic information in periods and areas not covered by other sources. In the last five years several studies have employed the wind direction observations contained in logbooks to generate climatic indices of instrumental character related to large scale patterns such as the atmospheric westerly circulation in North Atlantic, the strength of the West African Monsoon or the start date of the Indian Summer Monsoon (ISM). This study is focused on the winds in the eastern Mediterranean (EM) and its relation to the subtropical climate at decadal scale. Previous studies have shown a significant link between the frequency and strength of the prevalent summer northerly winds (Etesian winds) of the EM and the strength of the ISM. This relationship had only been studied in detail for the second half of the 20th century due to the absence of long and continuous series of wind observations in the EM for previous periods. In this work, we use historical wind data contained in ship’s logbooks to generate a new climatic index, the “Etesian Wind Index”, which can be defined as the percentage of days with prevalent northerly wind (between 315º and 45º) in a fixed region [10ºW-20ºW, 32ºN-36ºN]. We have been able to produce an index of the Etesian winds starting in 1877 suitable to analyze its long term variability and its relation with the ISM in unprecedented detail. Our first results show that the frequency of the northerly winds in the EM was significantly larger in the first half of the studied period, mainly due to an intensification of the zonal component in the second half of the studied period. Interestingly, the comparison with analogous Etesian wind indices computed from reanalysis products (NCEP/NCAR 20th Century (V2c) and ERA20C), shows strong discrepancies among them and with our ... |
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