WIND FIELD IN A CLOSED BREEZE CELL IN AHTOPOL - … · The sea breeze is a coastal phenomenon...
Transcript of WIND FIELD IN A CLOSED BREEZE CELL IN AHTOPOL - … · The sea breeze is a coastal phenomenon...
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Volume V, Number 3, 2015 Natural & Mathematical science 25
WIND FIELD IN A CLOSED BREEZE CELL IN AHTOPOL - MODELLING AND
OBSERVATIONS
Hristina Kirova, Damyan Barantiev, Valeri Nikolov, Ekaterina Batchvarova
National Institute of Meteorology and Hydrology,
Bulgarian Academy of Sciences,
66, Tsarigradsko Shose blvd Sofia 1784
ABSTRACT The sea breeze is a coastal phenomenon driven by the temperature difference over land
and sea. This thermally driven circulation is observed mainly during the warm seasons and is
characterized with specific wind and temperature conditions influencing all social and economic
activities. Two simulations with the Weather Research and Forecasting (WRF) model with different parameterizations of physical processes are performed and the results are compared
with data from a sodar at Ahtopol. Three days with closed breeze cell are chosen for the study.
The model simulates the wind field adequately in some of them and poorly in others. Key words: closed breeze circulation, vertical profiles, SODAR, WRF
INTRODUCTION
Life in coastal areas is influenced by the sea breeze in different ways: it affects dispersion of
pollutants, distribution of airborne insects, spread of pollens etc. The sea breeze is a thermally
driven circulation, observed mainly during the warm part of the year. The development of the sea
breeze depends on a variety of physical, climatic, orographic conditions (Simpson, 1994). The
breeze influences different recreational (e.g. gliding, ballooning, sailing) and economic activities
determining the importance of studying the phenomenon using long series of measurements and
numerical mesoscale models. Here we investigate the ability of Weather Research and Forecasting
(WRF) model to simulate wind field in a closed sea breeze cell. Tree days with closed breeze cell
are selected: 05.08.2008, 05.09.2008 and 07.05.2009 to be studied. The output of the model is
compared with data obtained by acoustic system for sounding of atmosphere - SCIENTEC Flat
Array middle range instrument (MFAS) sodar with frequency range 1650 – 2750 Hz; 9
emission/reception angles (0°, ±22°, ± 29°); maximum 100 vertical layers; range between 500 –
1000 m; accuracy of horizontal wind speed 0.1 – 0.3 ms-1; range of horizontal wind speed ± 50 ms-
1; accuracy of vertical wind speed 0.03 – 0.1m/s; range of vertical wind speed ± 10 ms-1; accuracy
of wind direction 2 -3 degrees. The climate of the sea breeze circulation based on sodar
measurements have been studied intensively since 2008. The duration of sea breeze at the Southern
Bulgarian coast is about 4 hours, the vertical scale - 600 m, wind speed in the cell is rarely higher
than 5 m/s, observed closed breeze cell are about 6 % per year (Barantiev et al 2013, Barantiev et al.
2011, Batchvarova et al. 2012, Batchvarova et al 2011, , Novitskii et al. 2012 ). The sodar is
operational since July of 2008 at southernmost site at the Bulgarian Black sea coast under a
Bulgarian – Russian joint project between the National Institute of Meteorology and Hydrology -
Bulgarian Academy of Sciences (NIMH-BAS) and the Research and Production Association (RPA)
Figure 1. The meteorological observatory Ahtopol.
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“Typhoon” in Obninsk, which is part of the Russian Federal Service on Hydrometeorology
and Environmental Monitoring (Roshydromet).
The sodar is located at meteorological observatory (MO) of Ahtopol (NIMH - BAS) about
400 m inland, 30 m above the sea level. It is mounted on the roof of station building (Figure 1). In
the vicinity of the station the coastline is oriented from NNW to SSE which determines that the
marine conditions are represented by the flows from the sector 0 – 150 degrees (air mass intrusions
from the sector 0-150 degrees represent intrusions from the sea).
MODEL SET UP
Simulations are performed with the Weather Research and Forecasting (WRF) model with
dynamical Advanced Research WRF (ARW) core, version 3.3.1 (Skamarock et al., 2008). The
initial and boundary conditions are provided by the US National Center for Environmental
Prediction Final Analyses (FNL) model with 1x1 degree spatial and 6 hours temporal resolution.
Details on model configuration are described in Table 1. For both configurations (WRF1 and
WRF2) two- way interactive nesting is applied which allows exchange of information between
nested domain and its parent one (Figure 2). The model top is set to 50 hPa. The number of vertical
levels in WRF1 is 50, in WRF2 – 43.
Figure 2. Configuration modelling domains (WRF2) and terrain features of the innermost one.
Table1. Physical options for WRF1 and WRF2 simulations WRF1 WRF2
Microphysics
95 (D1&D2), 5(D3&D4)= Eta
microphysics
8 (D3&D2)= Thompson
graupel scheme; 4(D1)=WSM
5-class scheme Longwave radiation 1 = RRTMG 1 = RRTM
Shortwave radiation 2 = RRTMG 2 = Goddard
Surface layer 2 = Eta similarity 2 = Eta similarity Land surface 1=thermal diffusion scheme Noah LSM
PBL 2 = Mellor-Yamada-Janjic (MYJ)
2 = Mellor-Yamada-Janjic
(MYJ)
Cumulus parameterisation 5 = New Grell (only for D1, D2, D3) 5 = New Grell (D1 & D2)
Urban physics 3 – category Urban Canopy Model
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MODEL RESULTS
Evolution of breeze cells is examined through vertical cross –sections of zonal-component of
wind speed (U), wind speed (Wsp), Wdir - wind direction and vertical component of the wind speed
(W) (Figure 3). Both configurations of WRF simulate the observed structure with some delay in
time and with different spatial scale in vertical. WRF1 patterns are with smaller size but closer to
the measured ones, except for W. Sodar WRF1 WRF2
a)
b)
c)
Figure 3. Vertical crossection (07.05.2009) of zonal component of the wind speed a); wind speed b); wind
direction c); vertical component of the wind speed d).
The ability of presented configurations to reproduce the vertical structure during well
recorded closed breeze cells is studied by comparing the model output at every level with
measurements. For every level the correlation coefficient (r) is calculated (Figure 4). The best
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overall performance is obtained for the event of 07 May 2009.The lowest values for correlation
coefficient are obtained for the vertical wind speed. As a whole the most stable parameter for
WRF2 simulation is the zonal component of the wind speed.
WRF1 WRF2
05 A
ugu
st 2
008
05 S
epte
mb
er 2
008
07 M
ay 2
009
Figure 4. Variability of the correlation coefficient with height
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CONCLUSIONS:
Development of the sea breeze on the Southern coast of Bulgaria has been simulated with
WRF (ARW) and model outputs have been evaluated against data from sodar. Two configuration of
WRF have been applied with widely used Mellor-Yamada-Janjic planetary boundary layer schemes.
Both model configurations reproduced the observed structure shifted in time and with
different vertical scale. WRF1 qualitatively overperforms WRF2 but in the same time better
correlation is achieved for studied parameters for WRF2.
Acknowledgements. This work is result of intergovernmental agreement for scientific
cooperation between Bulgaria and Russia,and in particular it is a part of a research project initiated
between the National Institute of Meteorology and Hydrology – Bulgarian Academy of Sciences
(NIMH-BAS) and the Research and Production Association (RPA) “Typhoon” – Russian Federal
Service on Hydrometeorology and Environmental Monitoring (Roshydromet). This paper has been
prepared with the financial support of the European Social Fund through Project *ВG051РО001-
3.3.06-0063*.NIMH - BAS is solely responsible for the content of this document, and under no
circumstances can be considered as an official position of the EU or the Ministry of Education and
Science.
LITERATURE
1. Barantiev, D., E. Batchvarova, M. Novitsky, (2013). Exploration of the Coastal Boundary
Layer in Ahtopol through Remote Acoustic Sounding of the Atmosphere, paper in conference
proceedings, 2nd National Congress on Physical Sciences, Section: Physics of Earth, Atmosphere
and Space (S07.26), 25-29 September 2013, Sofia, Bulgaria
2. Barantiev D, M Novitsky, E Batchvarova, (2011). Meteorological observations of the
coastal boundary layer structure at the Bulgarian Black Sea coast, Adv. Sci. Res., 6, 251-259
3. Batchvarova, E., D. Barantiev, M. Novitsky, (2012). Costal Boundary layer wind profile
based on SODAR data – Bulgarian contribution to COST Acton ES0702, paper in conference
proceedings, The 16th
International Symposium for the Advancement of Boundary-Layer Remote
Sensing – ISARS 2012, 5-8 June 2012, Boulder, Colorado, USA
4. Batchvarova, E., D. Barantiev, M. Novitzky, 2011: Characteristics of the sea breeze at the
southern Bulgarian Black sea coast based on sodar and eddy correlation measurements.
Energy&Meteorology - Weather and Climate for the Energy Industry, ICEM2011, 8-11 November,
Surfers paradise, Queensland, Australia, p.64
5. Novitskii M. A., Kulizhnikova L. K., Kalinicheva O. Yu., Gaitandzhiev D., Barantiev, D,
Bachvarova E, Krysteva, K., (2012). Characteristics of wind speed and wind direction in the
atmospheric boundary layer on the southern coast of Bulgaria, Russian Meteorology and
Hydrology, 37, 159-164.
6. Simpson J. E: Sea breeze and local wind, 1994. Cambridge University Press
7. Skamarock W., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, M. G. Duda, Xiang-Yu
Huang, W. Wang, J. G. Powers, 2008. A Description of Advanced Research WRF Version3
http://www.mmm.ucar.edu/wrf/users/docs