Study on air temperature fall by sea breeze and a simple evaluation method of urban heat island measure technology using upper weather data

We observed upper weather data at four towers located between Osaka city and East-Osaka city forming a line from the shore. Observation heights of upper weather data are between about 40 to 85 m. The main observation elements are air temperature and wind direction and velocity, unfortunately a turbulence statistic was not observed. Air temperature characteristics affected by sea breeze are considered using these upper weather data. Mutual relations of air temperature between towers are evaluated. In a condition of sea breeze, air temperature difference of around 2 - 4 degrees Celsius occurred in the shore part and the inland. But in other wind conditions, air temperature difference between four towers did not occur. At each observation point (tower), air temperature of upper weather and near ground changed approximately at the same time. The time change of air temperature at the inland points was late more than one hour from that at the point of the neighborhood of shore. The time change of air temperature at the city center point which is located between the inland and the neighborhood of shore was late more than half hour from that at the point of the neighborhood of shore. Convection heat transfer coefficients from near surface to upper air are estimated using upper weather data and near ground data according to the heat budget model in surface boundary layer. Then, air temperature decrease in the case of applying urban heat island measure technology is estimated using these convection heat transfer coefficients. From the analysis of the data of Osaka tower in summer of ten years, the difference by the year of convection heat transfer coefficient in surface boundary layer is not confirmed. Air temperature decrease in the nighttime is around two or three times of that in the daytime when same sensible heat flux is reduced in the daytime and nighttime. Air temperature decreases are almost the same when same sensible heat flux is reduced at four towers.