Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations
Dry spells during the rainy season have a far‐reaching environmental impact in the Levant. A previous study by Saaroni et al. investigated prolonging dry spells (PDSs) and classified them subjectively into three types: “subtropical,” “baroclinic” and “polar.” They developed quantitative indices to i...
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crwiley:10.1002/joc.5862 2024-06-23T07:53:25+00:00 Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations Saaroni, Hadas Ziv, Baruch Harpaz, Tzvi Lempert, Judith The Open University of Israel's Research Fund Israeli Science Foundation 2018 http://dx.doi.org/10.1002/joc.5862 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.5862 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.5862 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor International Journal of Climatology volume 39, issue 2, page 1054-1071 ISSN 0899-8418 1097-0088 journal-article 2018 crwiley https://doi.org/10.1002/joc.5862 2024-06-13T04:22:43Z Dry spells during the rainy season have a far‐reaching environmental impact in the Levant. A previous study by Saaroni et al. investigated prolonging dry spells (PDSs) and classified them subjectively into three types: “subtropical,” “baroclinic” and “polar.” They developed quantitative indices to identify each type. The present study analyses dry events, both individual days and spells, based on the above classification. We found that the indices identifying PDS types are effective for distinguishing among individual dry days of the three types, but not as precursors of dry days. However, when the indices keep positive for 2 or 3 days consecutively, they become effective precursors of dry spells. An alternative, automatic classification, using the K ‐means technique, yielded classes similar to those defined subjectively. The analysis revealed the dominance of the “baroclinic” type and the tendency of “subtropical” type to become “baroclinic.” Composite maps of cyclone tracks which were derived for days belonging to each type showed track distributions characteristic to particular types. For every type, the evolution of dry spells was studied through composite maps of 500‐hPa geopotential height (GPH) anomaly. The maps were derived for 1–3 days preceding the event. Pronounced patterns were identified as precursors of specific dry spell types; positive anomaly over Canada and Greenland, combined with negative anomaly over northwest Europe turned out as precursors of “baroclinic” and “subtropical” events, whereas the North Atlantic Oscillation (NAO), in its positive phase, was found as an exclusive precursor of the “polar” type. All three types of dry days are characterized by an offshore lower‐level wind, and by an absence of Cyprus Lows, due to deflection of cyclone tracks away from the Middle East. This implies that dry conditions in the Levant are caused by both thermodynamic (mesoscale) and dynamic (synoptic scale) factors. Article in Journal/Newspaper Greenland North Atlantic North Atlantic oscillation Wiley Online Library Canada Greenland International Journal of Climatology 39 2 1054 1071 |
institution |
Open Polar |
collection |
Wiley Online Library |
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crwiley |
language |
English |
description |
Dry spells during the rainy season have a far‐reaching environmental impact in the Levant. A previous study by Saaroni et al. investigated prolonging dry spells (PDSs) and classified them subjectively into three types: “subtropical,” “baroclinic” and “polar.” They developed quantitative indices to identify each type. The present study analyses dry events, both individual days and spells, based on the above classification. We found that the indices identifying PDS types are effective for distinguishing among individual dry days of the three types, but not as precursors of dry days. However, when the indices keep positive for 2 or 3 days consecutively, they become effective precursors of dry spells. An alternative, automatic classification, using the K ‐means technique, yielded classes similar to those defined subjectively. The analysis revealed the dominance of the “baroclinic” type and the tendency of “subtropical” type to become “baroclinic.” Composite maps of cyclone tracks which were derived for days belonging to each type showed track distributions characteristic to particular types. For every type, the evolution of dry spells was studied through composite maps of 500‐hPa geopotential height (GPH) anomaly. The maps were derived for 1–3 days preceding the event. Pronounced patterns were identified as precursors of specific dry spell types; positive anomaly over Canada and Greenland, combined with negative anomaly over northwest Europe turned out as precursors of “baroclinic” and “subtropical” events, whereas the North Atlantic Oscillation (NAO), in its positive phase, was found as an exclusive precursor of the “polar” type. All three types of dry days are characterized by an offshore lower‐level wind, and by an absence of Cyprus Lows, due to deflection of cyclone tracks away from the Middle East. This implies that dry conditions in the Levant are caused by both thermodynamic (mesoscale) and dynamic (synoptic scale) factors. |
author2 |
The Open University of Israel's Research Fund Israeli Science Foundation |
format |
Article in Journal/Newspaper |
author |
Saaroni, Hadas Ziv, Baruch Harpaz, Tzvi Lempert, Judith |
spellingShingle |
Saaroni, Hadas Ziv, Baruch Harpaz, Tzvi Lempert, Judith Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations |
author_facet |
Saaroni, Hadas Ziv, Baruch Harpaz, Tzvi Lempert, Judith |
author_sort |
Saaroni, Hadas |
title |
Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations |
title_short |
Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations |
title_full |
Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations |
title_fullStr |
Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations |
title_full_unstemmed |
Dry events in the winter in Israel and its linkage to synoptic and large‐scale circulations |
title_sort |
dry events in the winter in israel and its linkage to synoptic and large‐scale circulations |
publisher |
Wiley |
publishDate |
2018 |
url |
http://dx.doi.org/10.1002/joc.5862 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.5862 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.5862 |
geographic |
Canada Greenland |
geographic_facet |
Canada Greenland |
genre |
Greenland North Atlantic North Atlantic oscillation |
genre_facet |
Greenland North Atlantic North Atlantic oscillation |
op_source |
International Journal of Climatology volume 39, issue 2, page 1054-1071 ISSN 0899-8418 1097-0088 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/joc.5862 |
container_title |
International Journal of Climatology |
container_volume |
39 |
container_issue |
2 |
container_start_page |
1054 |
op_container_end_page |
1071 |
_version_ |
1802645022553669632 |