Abstract: In order to gain insights into the influence of environmental conditions on air temperature observation,the difference of temperature between the two stations and its response to the sunshine,wind speed and precipitation caused by different observation circumstances were investigated using the ground-based meteorological data of Beijing (54511) and Nanhaizi (A1274) weather stations in 2017.The results suggest that the significant difference in air temperature in 2017 is attributed to the differences in environmental conditions.The annual average temperature at the 54511 station is 0.75℃ higher than that at A1274 station,and the monthly average air temperature at the 54511 station is higher than that at A1274 station for each month.In addition,the smallest and largest differences of monthly mean air temperature between two stations are 0.60℃ in July and 1.09℃ in September,respectively.Moreover,the difference of mean daily maximum air temperatures between two stations is small,while that of mean daily minimum air temperature (MINT) is large and the MINT of 54511 station is 1.24℃ higher than that of A1274 station.Besides,the diurnal variations of air temperature at the two stations are similar and both show a single peak distribution,while diurnal temperature range and MINT of 54511 stations are smaller and larger than those of A1274 station,respectively.The difference in hourly air temperature (TD) between the two stations increases with duration and intensity of sunshine increasing.TDs during 10-14 o'clock and 19-23 o'clock when short-wave and long-wave effects are respectively strongest are significantly related to direct radiation in the daytime with relationship coefficients of 0.459 and 0.601.Also,horizontal wind speed has a great influence on the difference in temperature between the two stations.At the same time,the differences of the annual average temperature between the two stations are below 0.1℃ and above 1.28℃ when the wind speed exceeds 5 m·s^-1 and is less than 1 m·s^-1,respectively.The temperature difference between the two stations is smaller in the rainy day than in the non-rainy day.Specifically,air temperature in 54511 station is only 0.2℃ higher than that in A11274 station.The distance between the two stations is about 4.3 km,which indicates the climatological temperature of the two stations is homogeneous.The proportions of construction land,vegetation and water body in the 2 km area around the 54511 station are about 30% higher and 28% lower as well as similar relative to those of the A1274 station,respectively.In addition,the Fifth Ring Road near the 54511 station is of the characteristics of low reflectivity and high heat capacity and is able to absorb solar radiation and store more heat in the daytime,and then releases this heat in the nighttime.Altogether,the temperature difference between the two stations is greatly affected by solar radiation and wind speed,but less affected by precipitation,owing to the difference in environmental conditions.

Key words: Meteorological observatory environment, Air temperature, Solar radiation, Wind speed, Precipitation