Standard Assessment Of Temperature And Wind Observation Environment Based On Numerical Simulation

This article is completed under the patronizing of China Meteorological Administration, public welfare meteorological profession specific (Project number: GYHY201106049). The accuracy of three kinds of models was validated by using the observational experiment data and wind tunnel data, The model parameters were optimized by test.The experimental observational data of single building impact on wind speed and direction were analyzed. Meanwhile,the CFD model is used to simulate four classifications for wind observing environment issued by WMO, analysising sensitively and evaluating quantitatively of requirements for the distance of the obstacles,then quantitatively assess the actual environmental impact of Miyun observatoriesAnalysis the observations data of different heat sources and national highway impact on temperature.The USSM is used to analysis sensitively and evaluate quantitatively of requirements for the distance of the road The conclusions are as follows:(1)Compared with observational experiment data or wind tunnel data,the simulation results show the validation of models. Sensitivity tests of parameter optimization showed that all the indexes will be stable if the height of computational domain beyond three times the height of the building. The values of the indexes will be increase with the increase of the level of initial mesh. All the indexes are not more sensitive to the level of local initial mesh. The vortex length before the building is more sensitive to the form of mean wind profile than that after the building. By comparing to the observing data, the optimal parameters are the height of computational domain as 3 times building height, the level of initial mesh as 4, the level of local initial mesh as 4 and the form of mean wind profile as exponential.(2) Observational trial data of structure impact on the wind shows the obstacle can weaken the wind speed, which is related to baseline wind speed, and with great wind speed comes great effect extent. While the baseline wind velocity is between lm/s and 3 m/s,the wind speed attenuation of the sites begins to decrease with the increasing of distance behind the obstacle and the attenuation ratio of wind speed is 10-15 percent or so at the distance of 10 times the height of the obstacle; as the baseline wind velocity is more than 3 m/s, the wind speed attenuation of the sites decreases firstly and then increases, which there is a cavity at the distance of 5 times the height of the obstacle, and the velocity value attenuates by about 20-30 percent at 10 times the height of the obstacle distance.when the wind and building have a 45-degree angle,Wind speed attenuation ratio at obstacle leeward direction of 12.5 degrees is greater than it at 45 degrees. The prevailing wind direction frequency is decreased caused by the obstacle, and the influence distance is 6 times the height of the obstacle of vertical wind,8 times the height of 45-degree angle wind.(3) CFD simulations shows,WMO require the class 1 station to ensure the wind speed observations don't affected by obstacles when the wind vertical the obstacles, class 2 station could have 40.7% error. From the sensitivity analysis of inflow wind speed,building height, building angular width and inflow direction,we can see that the distance requirement of 10 meters height for wind observation change with different inflow wind speed; while the obstacle height is less than 6 meters,the influence on wind speed and wind direction is not more sensitive,the distance requirement of the obstacle decreases with the building height increased when the obstacle height is more than 6 meters; the distance requirement of the obstacle will be higher by the increasing of the building angular width;the influenced scope of wind speed is larger,the horizontal affected area of wind direction is bigger and lateral side is smaller when the angle of the building and the inflow wind is 45 degrees.(4)The observation environment around Miyun Station has serious influences on wind speed of the observation field. The annual mean wind speed from 2004 to 2013 reduces by 27.2 percent compared with it from 1994 to 2003, and the dominant wind scale drops. The 64 tests at 8 directions and 4 different speeds show that the CFD model can better simulate the attenuation in wind speed of Miyun station. The simulation values of the wind speed attenuation are higher than the observations in the directions of southwest, west and northwest, which illustrates observation environment around these directions changes gradually during the two stages. While, the results of simulation in directions of south, southeast and north are in good agreement with the observations, indicating that these changes before and after stages are caused indeed by changing of the surrounding buildings. Although the impact of buildings in the east and northeast of the Miyun station is not obvious, the trees are the main cause of the decreasing of wind speed, and the attenuation ratio of wind speed is about 20 percent.(5) Observational data shows that under the calm wind conditions, temperature of class 4 station in WMO higher than class 3 station and class 2 station. With the increase of stations classification, temperature inside a screen gradually increased.(6) Experiment data show that the influence of road on temperature is more significant at night than in the daytime.The simulation results show that road has a obvious influence on temperature within 90 meters downwind.The influence distance of road on temperature increase firstly then decrease with the increase of wind speed. The influence distance on temperature gradually increase with the increase of road width.