Sea Breeze Numerical Simulation in Caspian Sea Southern Coasts on the Base of Climatic Characteristics

IntroductionSea breeze system as a Meso-scale phenomenon is caused by direct radiation of the sun on land and also the energy balance between water and land. It is also observed along middle and tropical coasts (Bowers, 2004). Cool marine air propagates inland when a cross-shore meso-scale (2–2000 km) pressure gradient is created by daytime differential heating (Miller, 2003). In the clear weather, when the heat brings a pressure gradient force from sea toward the land, marine air surface layer moves toward the land. The temperature decrease on land depends on the beginning sea breeze. Sometimes, in the afternoon (when there is a maximum difference between land and sea), the heat difference reaches 4.4 centigrade (Rao, 1955). This research studies the sea breeze according to climatology parameters and numerical simulation. Actually it determines synoptic patterns providing suitable conditions for the occurrence of sea breeze along the Caspian Sea coastlines. Here it also has determined the initiating, the termiation, and the climax of sea breeze during the months and seasons.Materials and MethodsIdentification sea breeze occurrence and determining dominant days: In this study, the main filter for extracting the sea breeze days is a surface wind reversal criterion. This criterion is implemented in the following manner (M. Furberg et al, 2002): The wind must blow (onshore current) for at least three consecutive hours during the hours from sunrise to sunset. The days were selected by monitoring the speed and wind direction, air pressure, sea and land temperature, cloudiness from May to September(from 2000-2006). The daily variations of wind direction are the most important criterion for selecting the sea breeze.To have a more accurate report from sea breeze days which separate it from synoptic currents, another method was added to the above criterion. Borne et al (1998) used Tland-Tsea>3 C criterion in which Tland is the mean of daily temperature on land during sunny days and Tsea is sea surface temperature. Finally two samples (July 8th - 9th 2003 and June 5th - 6th 2003) were chosen and analyzed. TAPM is a PC-based meso-scale numerical model with meteorological and air pollution components. This model is three dimensional, controllable; it also has effective and high resolution. The meteorological module of TAPM predicts the local-scale circulations, such as sea breezes and slope flows, in conjunction with larger scale synoptic scale meteorological fields. It also enjoys high graphical representation and uses terrain database, meteorology and climatology data, and pollution data.Results and DiscussionThe highest temperature difference because of heating difference between the land and the sea occurs in the second half of spring and the first half days of summer in all of the stations. The results show that the highest differences between land and sea surface temperature in all stations have occurred in May. On average, in all stations, the sea breeze from May to August is most frequent. In this period, the sea breeze appears in 40% of all days.ConclusionAnalysis of the LARS-WG outputs for 2010-2039 show the results as bellow:• Mean amount of precipitation will be decreased by 2 percent during 2010-2039,• Summer and second half of winter rain fall will increase over the period under study,• Thresholds of heavy and extreme rainfall will increase by 3 and 19 percent, respectively,• Hot days series will be increased over the future period, Amount of freezing day lenght will decrease,• Annual station-averaged temperature has calculated to increase by 1oCin 2020s. The greatest increase inannual mean temperature has been calculated to be 1.1°C in winters.