Identification And Distribution Characteristics Of Sea And Land Breeze In The Western Bohai

In this paper, the identification and distribution characteristics of sea and land breeze in the western bohai during the year 2008 is analyzed, using 14 automatic weather station observation data of Tianjin. data from the Beijing sounding station and conventional surface meteorological stations in Tianjin.First, by summarizing the researches of the past 20 years mainly on identification of sea breeze, the information obtained with conventional land-sea breeze at identifying the three main factors should be considered:(1) conducive to the formation of large-scale sea breeze circulation background situation and pressure field situation; (2) between sea and land exist a certain temperature difference; (3) the changes of near-surface wind direction and wind speed.Secondly. based on the above three conclusions, the main mechanism for the formation from the sea breeze and the impact factor of departure, through a comparative analysis of several typical sea breeze recognition to discuss the Tianjin Binhai area for identification of sea breeze on 4 criteria. (1) First, select a data set of weather conditions, weak circulation, the provisions in the 37-41°N.115-120°E regional weather maps on the inner surface strips, only≤1 through the pressure lines, which meet both very weak gradient wind Pressure field conditions; in the regional context, the daily surface weather maps on 08.14.20 when the weather more than two types of weak circulation, the circulation on the weather at the provisions of the weak, weak circulation as the weather situation Indicators; (2) from sunrise to sunset during this time to have the land and sea temperature difference is greater than 0℃moment appears; (3) sunrise to 2 hours after sunset, wind direction a continuous 3 hours there, and Wind speed> 1m/s; (4) 00 am to 1 hour after sunrise, there appeared a continuous 2 hours land breeze wind and land breeze wind> 0.5m/s.Finally, according to established criteria of the sea breeze and the station at the direction of the sea breeze, coastal areas of Tianjin, the temporal and spatial distribution of land and sea breeze carried out statistical analysis, the following preliminary conclusions:(1) time features:Tianjin, west coast of Bohai Bay, throughout the year to the sea breeze can be observed, but the seasonal distribution is uneven, most in summer, spring, fall is relatively small, at least in winter; winds start time of the spring and summer than in winter and Early autumn; sea breeze in summer at the latest end time, the first winter; the duration of the winter land breeze sea breeze than the duration of the summer long; initial maximum wind speed in spring and winter minimum; strong sea breeze winds 1 to 6 months is relatively large,10 December is relatively small, the maximum wind strength appears 16 times on average between 17 o'clock.(2) the spatial characteristics of three coastal stations:chittagong station minimum number of days of sea breeze appears, Hangu and Tanggu station the same; dagang station earliest starting time of the sea breeze, Tanggu station relatively late, the latest station in Hangu; up to the initial direction and the coastline of the sea breeze close, at least the initial wind direction perpendicular to the coast; initial time in the sea breeze near the sea than the steering angle to be at least 20°. in order to accurately determine the beginning of the sea breeze; Hangu stand strong sea breeze winds the most. followed by Tanggu station, dagang station minimum. (3) the spatial characteristics of marine, coastal and inland stations:communication from the sea breeze did not show significant seasonal changes in sea-land breeze can be widely spread throughout the year to Ninghe, Jinnan, Toray three stations, the sea breeze inland The number of stations appear gradually decreased with increasing distance, the farthest reach Jixian. With the increase of the distance to leave the coast, the sea breeze late starting time change, the wind gradually shorter duration; humidity obvious diurnal variation, from sea to land humidity diurnal range becomes smaller, the humidity was significantly higher than the coastal stations The same time the humidity inland stations; temperature after sunrise, coastal and inland stations than at sea, the higher the temperature the more inland; daily maximum temperature greater than inland stations and sea shore, Tanggu station daily maximum temperature in 15, Tanggu Station at this time is the height of the sea breeze development period. Temperature difference between sea and land the three points are obvious diurnal variations during the day for the peak night for the trough, from sea to land and sea temperature rise.