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Synoptic and dynamic analysis of few extreme rainfall events in Iraq

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  • Mustansiriyah Uneversity, College of Science
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Rainfall is most important factor influencing the atmospheric cycle of the atmosphere, since its spatial and temporal distributions are very complex. Heavy rainfall events may cause flash floods in the arid and semi-arid regions Middle East. The present study investigates the synoptic and dynamics situations of four extreme rainfall events that occurred in Iraq on 04, 15, 24, and 30 of November 2018. Rainfall data were acquired from the Global Precipitation Mission (GPM), and surface and upper meteorological variable were acquired from the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5). The Rainfall analysis showed that November 2018 was characterized by the most unusual heavy rain events during the past two decades with a maximum of 200 mm/month (an anomaly of about 120 mm/month) near the town of Kut in the east part of the country (with an anomaly of about 120 mm/month). Analysis of surface and upper level charts indicated that during the four events the region was dominated by the Active Red Sea Trough (ARST), a situation when RST at the surface is associated by mid-tropospheric trough. The results also denoted that moisture was transported from equatorial north east Africa and the Red Sea towards north east regions including Iraq. The 850 hPa chart denoted that the warm moist air was advancing towards the cooler areas with a maximum speed of 20 m/s above the axis of the RST. The negative vertical pressure velocity along with high values of relative humidity suggests that cloud continued to develop at that level. 500 hPa charts showed that during all four events there was a positive vorticity advection towards the areas where rain was falling. This advection process contributes to a lifting of the air to upper levels. The 200 hPa composite maps of polar front jet stream and ageostrophic divergence indicated that in all four events there were high air suction from lower levels which enforced upward vertical motion at these levels and deepening low pressure areas at the surface.
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Modeling Earth Systems and Environment (2022) 8:4939–4952
https://doi.org/10.1007/s40808-022-01419-1
ORIGINAL ARTICLE
Synoptic anddynamic analysis offew extreme rainfall events inIraq
JasimH.Kadhum1· MunyaF.Al‑Zuhairi1· AhmedA.Hashim1
Received: 24 November 2021 / Accepted: 21 April 2022 / Published online: 23 May 2022
© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2022
Abstract
Rainfall is most important factor influencing the atmospheric cycle of the atmosphere, since its spatial and temporal distri-
butions are very complex. Heavy rainfall events may cause flash floods in the arid and semi-arid regions Middle East. The
present study investigates the synoptic and dynamics situations of four extreme rainfall events that occurred in Iraq on 04, 15,
24, and 30 of November 2018. Rainfall data were acquired from the Global Precipitation Mission (GPM), and surface and
upper meteorological variable were acquired from the European Centre for Medium-Range Weather Forecasts (ECMWF)
Reanalysis v5 (ERA5). The Rainfall analysis showed that November 2018 was characterized by the most unusual heavy rain
events during the past two decades with a maximum of 200mm/month (an anomaly of about 120mm/month) near the town
of Kut in the east part of the country (with an anomaly of about 120mm/month). Analysis of surface and upper level charts
indicated that during the four events the region was dominated by the Active Red Sea Trough (ARST), a situation when RST
at the surface is associated by mid-tropospheric trough. The results also denoted that moisture was transported from equato-
rial north east Africa and the Red Sea towards north east regions including Iraq. The 850hPa chart denoted that the warm
moist air was advancing towards the cooler areas with a maximum speed of 20m/s above the axis of the RST. The negative
vertical pressure velocity along with high values of relative humidity suggests that cloud continued to develop at that level.
500hPa charts showed that during all four events there was a positive vorticity advection towards the areas where rain was
falling. This advection process contributes to a lifting of the air to upper levels. The 200hPa composite maps of polar front
jet stream and ageostrophic divergence indicated that in all four events there were high air suction from lower levels which
enforced upward vertical motion at these levels and deepening low pressure areas at the surface.
Keywords Extreme rainfall· Floods· Vorticity· Ageostrophic· Red sea trough· Iraq
Introduction
The study and evaluation of rainfall in arid and semi-arid
regions of the world. is not only of particular interest to deci-
sion makers (i.e. water managers, agronomists, industrialists,
climatologists, etc.) but also important for human life and
activities (Al-Salihi etal. 2013). Precipitation measurements
provide essential detailed information from spatial and tem-
poral variation in precipitation, which is required for hydro-
logical and climatic models which employ in floods events
and severe weather disasters, which occur by heavy rainfall
and runoff (Asinya and Alam 2021). Flash flood is the most
severe type of flood because it is quick, short-lived, and
hazardous. Both types of floods have negative environmen-
tal and socio-economic impacts. Flash floods are typically
triggered by a large volume of rain in a short period of time
(Murray and Ebi 2012). Because runoff is created rapidly
and intensively, water levels increase quickly, and discharge
reaches its peak in a short period of time; therefore it is very
challenging to predict flash flood events (Borga etal. 2011;
Asinya and Alam 2021). In recent decades, global warming
and climate change have resulted in increasing unpredictable
weather events such as flash floods (Groisman etal. 2005).
In most parts of the world climate change causes a decline in
annual rainfall and an increase in extreme rain events leading
to flash flood.
During the past decade many arid and semi-arid countries
in the Middle East have experienced flash flood disasters
(AL-Salihi 2017). Saudi Arabia experienced the worst flood-
ing in living memory during Nov 2009 and May 2010 in the
two cities of Jeddah and Riyadh, respectively (Alamri 2011).
* Munya F. Al-Zuhairi
munya83.m@gmail.com
1 Department ofAtmospheric Sciences, College ofScience,
Mustansiriyah University, Baghdad, Iraq
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