پديد آورندگان :
ملكوتي، حسين نويسنده , , پاخيره زن، محمد نويسنده دانشجوي دكتري فيزيك دريا دانشكده علوم و فنون دريايي دانشگاه هرمزگان , , حسني، وجيهه السادات نويسنده كارشناسي ارشد هواشناسي دانشكده علوم و فنون دريايي دانشگاه هرمزگان ,
كليدواژه :
WRF , بادشمال , بوشهر , نسيم دريا ـ خشكي , گلباد
چكيده لاتين :
Extended Abstract
1-Introduction
Shamal winds recognized as a climate regime with a common occurrence in the Persian Gulf that makes the event of adverse weather conditions in this region periodically. Among the phenomenas that occurring under effect of Shamal wind, can be noted to dust storms, Low-level winds and inappropriate sea conditions (Rao, 2003). Shamal winds are categorized into two types, winter Shamal and summer Shamal. Sea-land breezes also are classified as a frequent mesoscale and heat driven flow associated with coastal areas. Temperature gradient between sea and land is the main reason for the formation of a sea breeze circulation that blows from sea to land in low level coastal atmospheric boundary layer. The suitable conditions for Sea-land breezes establishment when the synoptic winds are weak (low synoptic forcing) and temperature level is high in the coastal city of Bushehr (Bidokhti and Moradi, 1383).
The purpose of this research is to investigate seasonal Shamal wind event and its associated synoptic conditions by observations analyzing and numerical expriments on Persian Gulf. The impact of these conditions on wind pattern in the northwestern Persian Gulf coastal area and in optional case in the coastal area of Bushehr are studied and it is intruded interaction between meteorological mesoscale (sea-land breeze) and large-scale (synoptic pattern Shamal wind) forcing effects in this area.
2- Materials and Methods
2-1-Study Area
North of middle east are areas that dominated by the seasonal Shamal wind regime, that begin from the central deserts of Iraq and the mountains of northern Iraq, Turkey and Syria to Persian Gulf. In this study, the coastal city of Bushehr that located in the northwest of Persian Gulf and southwest Iran have been selected to investigate about interaction of Shamal wind pattern on local breeze on the coastal areas (Figure 1). Based on the location of the Bushehr and sea-land breeze definition, sea breeze will occurr in the sector of 180-270 degree.
Figure 1: Coastal case study area
2-2- Basic Data
In this study, in order to analyze the time series of coastal wind, it is used hourly wind speed and direction data from meteorological tower and meteorological station of Bushehr power plant and also wind data from Bushehr airport weather station. The meteorological station Bushehr power plant is located at 28°59ʹ N and 50°00ʹ E and Bushehr Airport Station is located at 28°58ʹ N and 50°49ʹ E. As shown Locations, both of weather station in a relatively small distance from each other.
In the next step, the NCEP FNL data used to generat the initial and boundary conditions for regional simulations by WRF model. This data has 1° × 1° resolution and are available for every 6 hours. This data produce by Global Data Assimilation System (GDAS) that continuously receive monitoring global data for analyze from Global Telemetry System (GTS) and other resources. Selected physical schemes for Model setup are represented in table 1:
Table 1: Selected physical schemes for WRF model setup
Selected physical scheme scheme
WSM 6 (Hong et al.,2004) Microphysics of cloud
Dudhia (Dudhia,1989) Radiation of short wavelength
RRTM (Mlawer et al., 1997) Radiation of long wavelength
NOAH [Chen and Dudhia, 2001; Ek et al., 2003] time interval of summer Shamal Physics of soil
PX (Pleim and Xiu, 2003) time interval of winter Shamal
MM5 SLS (Zhang and Anthes, 1982) time interval of summer Shamal Physics of surface layer
PX (Pleim and Xiu, 2003) time interval of winter Shamal
YSU [Hong et al., 2006; Hong, 2010] time interval of summer Shamal Boundary layer
ACM2 (Pleim, 2007) time interval of winter Shamal
Kain-Fristch (Kain and Fristch, 1993; Kain, 2003) Convection of Cumulus
3- Results and Discussion
The results of the observational time series analyzes from the meteorological tower of Bushehr power plant are shown in table 2 for winter (January) and summer (May) selective periods. These results show the mean detail information of typical wind regimes such as summer and winter Shamal and sea-breeze regimes during January and May 2010. In this table is represented formation quality, duration, mean speed, mean direction of sea-breeze wind in the beginning and ending of sea-breeze regimes during these months. It also is represented frequency of daily occurrence of typical wind regimes with themselves mean speed in Bushehr coastal area.
Table 2 :Specifications of typical wind regimes in Bushehr coastal area during January and May 2010.
Month Mean wind direction in the beginning of sea-breeze period Mean wind direction in the ending time of sea-breeze period Daily duration of sea-breeze activity (hours) Pure sea-breeze occurrence (225 °) Mean wind speed of sea-breeze regime Mean wind speed during the days without sea-breeze occurrence
Number of the days with Shamal wind activity Mean wind speed of Shamal wind regime Shamal wind regime
type
January 269 290 6 no 9 m/s 12.5 m/s 5 days 14 m/s Winter
May 210 230 9 yes 9 m/s 14 m/s 14 days 14 m/s Summer
Figure 1 represents synoptical condition at 10 pm24June 2010local time. Ascan be seen, the northern of Saudi Arabiais influencedbya highpressure systemwith central pressure around 1012hPainthis region. As well, on thePersian Gulf a low pressuretroughis dominant with 1000 hPa central pressure. In addition, a heat low pressure system is seen over east of Iran (region of Afghanistan, Pakistan and etc.). This area is experienced the pressure less than 996 hPa. Turkey, Iraq and west of Zagross mountain rang regions are affected with interactionof these dynamical systems that lead to the creation of Shamal wind in northwest of Persian Gulf.
Figure 1: Simulated synoptical maps for 24 June 2010 at 10 pm local time (top left: sea level pressure, top right: 850 hPa, middle left: 700 hPa, middle right: 500 hPa, down left: 300 hPa and down right: 200 hPa).
4-Conclusion
In general, Shamal wind affects Turcy, Iraq, Iran, Arabian Peninsula and adjacent areas. The maximum activity during 2010 observe in the winter in late of January and in the summer in June by maximum number of Shamal days. This result is obtained by analyzing data from the meteorological tower at height of 100 meters in Bushehr weather station that the summer Shamal causing disruption of coastal wind pattern in 14 days of May, 14 days in June and about 10 days in July of 2010 and in other months, usually less than three to five days. Winter Shamal occurs at intervals of 3 to 9 days from December to March. During the period that the sea-breeze is removed by synoptical Shamal winds forcing, the average daily wind speed more than period of sea-breeze activity.
