Embed Size (px)
Citation preview
5th International Conference on ReanalysisEVALUATION OF SZILAGYI WATERSPOUT NOMOGRAM AND TRIANGLE
DIAGRAM BY ERA-INTERIM
Asilhan Sirdas1, S., Ozmen1, I., Aydın1, M., Yavuz1, V.Y., and Kaya1, S.
1Istanbul Technical University, Faculty of Aeronautics and Astronautics, Department of Meteorological
Engineering, 34469, Maslak/Istanbul
([email protected], [email protected], [email protected], [email protected], [email protected], [email protected])
ABSTRACT
Climate change impacts on extreme and rare weather events are much more obvious so that many scientific
studies have been focused on worldwide. The connection between the formation of waterspouts that are
considered as rare event for Turkey, and the climate change has been a matter of curiosity. The vortex incident
and waterspout have been observed 260 times in the period between 1997 and 2015 at Turkey, and the most of
them were observed in the coast and lakes of Antalya. In this study, the data sets of ground base stations and
ERA- Interim are studied for four extreme waterspout cases in Kale – Demre, Antalya station which were
observed at the period between 2008 - 2013 were discussed in the study. ECMWF Reanalyse data ERA-Interim
is used for different vertical heights, and the meteorological variables of ERA-Interim is downscaled on the
station of Kale – Demre. The vertical thermodynamic structure of vortexes are analysed by diagrams and
vertical indexes of Plymouth State Weather Center. The acceptability of the Szilagyi Waterspout Index for four
extreme cases are computed and the availability of waterspout predictions have been examined in the study. In
addition, a triangle diagram was created as a new technique to predict the waterspouts by merging Sweat Index,
relative humidity and 850 mb wind speed. Triangle Waterspout Diagram is designed for the waterspout cases in
the Antalya region for period of 2000 and 2012.
Key words: Triangle Diagram, Climate Change, Extreme Weather, Szilagyi Waterspout Index, Demre
INTRODUCTION
The waterspouts that are increasingly seen in Turkey in the recent period are considered to be one of the
natural disasters that cause destruction of lives and property. Rennό and Bluestein (2001) has included the
dynamic formulas of water waterspouts in their work "A Simple Theory for Waterspout" [1]. In the work
"Numerical Simulation of Waterspouts Observed in The Tyrrhenian Sea", the position is simulated by the
dynamic formula of the waterspout model located in the southeast of the island of Capraia [2]. Sioutasa and
Keu investigated synoptic circulation patterns in the 28 waterspout event in the central and eastern regions of
the Mediterranean [3]. The Szilagyi Nomogram, which Szilagyi included in his work "A Waterspout
Forecasting Technique", was the basis of this study [4]. In Turkey, the number of cases in Turkey in 1940 -
2010-time period (Fig 1a) and the distribution of cases (Fig 1b) are given below (Fig 1).
Fig 1 The distribution of observed waterspouts related to thunderstorms in Turkey between 2001 and 2010
The number of waterspouts has been increased the importance of the waterspout estimate. For this
reason, we tried to investigate the consistency of the four water waterspout events in the 2008 – 2012 period
in the Antalya region where the cases of Szilagyi Waterspout Index, which is used for water waterspout
estimation in our study, concentrate and a triangle diagram of cases in the Antalya region was created during
2000 – 2012 period.
DATA AND METHODOLOGY
The basis of the Szilagyi Waterspout Index,
which we investigated for our consistency for Kale-
Demre / Antalya (Fig 2), is based on the Szilagyi
Waterspout Nomogram (Fig 3) developed by
Szilagy. The nomogram was created using 172 water
waterspouts coming into the market for 21 years [4].
Fig 2 Location of study area in the south-western coast
of Turkey; a) Turkey, b) Mediterranean coast of Turkey,
and c) Kale-Demre town
Fig 3 The Szilagyi Waterspout Nomogram
The water waterspout nomogram was created by
Wade Szilagyi in 1996 for the Great Lakes region.
In this research, Szilagyi nomogram, which has been
adapted to use in Mediterranean countries, has been
used with minor changes [6].
In the Szilagyi Waterspout Index, the nominal
value is calculated by calculating the Sea - 850 mb
temperature difference and EL - LCL for the date
when the event is expected to occur, and the
potential water waterspout formation is predicted.
It is an important detail that the nominal
result for the Mediterranean is that the additional
850 mb wind speed should be lower than 42
knots [6]. Sea temperature, 850 mb temperature,
850 mb wind speed, vertical temperature and
vertical relative humidity values required for
nomogram are the reanalyses obtained from
ECMWF. The data was opened using MATLAB
and the edits were made via EXCEL. Vertical
dew point values are calculated from EXCEL
using the following formulas. [7]
e_s=0,6113*exp(5423*(1/273,15-1/T)) (1)
RH(%)=e/e_s (2)
e=RH*100*e_s (3)
T_d=((1/273,15)-(1,844*〖10〗^(-4) )*ln(e/e_(0 ) )
)^(-1) (4)
Vertical temperature and vertical dew point
values were processed in Skew - t diagram to find
Equilibrium Level (EL) and Lifting Condensation
Level (LCL) heights. Convective cloud depth (EL
- LCL) was calculated with the help of EXCEL.
The correctness of the LCL level is also checked
by the following formula [8].
z_LCL= a*(T-Td) (5)
a = 0,125 km K^(-1) (6)
The triangle diagram at the end of the work
was created at the Antalya location with the
values of humidity - Sweat Index - 850 mb wind
speeds in the dates of the water waterspouts
between 2000 and 2012. The parameters used in
the diagram are determined by considering the
important variables used in the prediction of a
water waterspout. The values used in the triangle
diagram are daily values from the '' Plymouth
State Weather Center '‘and the vertical data of
ERA-Interim [8].
APPLICATION OF WATERSPOUT NOMOGRAM
The Skew - t diagram of the four cases that are found in the Kale - Demre station is available. The
values used in the Szilagyi Waterspout Nomogram are given in the table below. The data of the waterspouts
at different times in the Demre district of Antalya were analysed and evaluated individually in the Szilagyi
Waterspout Nomogram. The results are as follows.
9 March
2010
23 January
2009
16 December
2011
CONCLUSION
As you can see in Figure 13, only one of the four
waterspout cases in Kale - Demre region (09/03/2010)
has a very small value in Szilagyi Waterspout
Nomogram. The reason for this is that EL level cannot
be determined. However, when we build the Skew - t
diagram, the pressure levels can be plotted with more
frequent intervals and the result may vary. On the other
hand, in our examinations dated 23 January 2009 and 16
December 2011, the results were very close to the water
waterspout formation border. The results of the cases
dated December 20, 2011 are very close to the water
waterspout formation area due to the upper low and have
coordination with intersection of the mesocyclone water
waterspout area. These results suggest that the Szilagyi
Waterspout Index may be useful for predicting
waterspouts in the Mediterranean but should be
customized for the Antalya region. ERA- Interim data
can be used for analysis of extreme cases.
When the Triangle Diagram is examined, water
waterspouts in the Antalya region have been found to be
Fig 13 Szilagyi Waterspout Nomograms of all studied cases
around 65% and above relative humidity. Considering
Figure 7, the increase in the number of water
waterspouts is 70% RH or more. In addition, it is seen
that the sweat index value required for water
waterspout formation in Antalya region is at least 200.
On the other hand, it is seen that the water waterspout
is not formed when the wind speed of 850 mb in the
water waterspout cases between 2001 and 2012 is 5
knots lower.
a) b)
a)
b) c)
20 December
2011
In our study, in addition to the Szilagyi Waterspout Index examination, we tried to determine the conditions
of water waterspouts for Antalya with the Triangle Diagram which is created first time. In this diagram we have
formed with the water waterspouts that form in Antalya between the years of 2001 and 2012, there is a tendency
for the washer to concentrate on a certain area. The fact that the bottom right corner of the diagram is empty
indicates that the probability of water waterspout formation in this area is low.
