广州地区灰霾过程和清洁过程的边界层特征对比分析

利用2014~2016年广州国家基本气象站的微波辐射计、风廓线雷达和地面观测数据，研究广州地区灰霾过程和清洁过程的边界层结构特征.结果表明：（1）灰霾过程中，270m高度以下风速随高度递减，270m高度以上的风速随高度递增，2000m以下的风速增率小于2000m以上的风速增率，盛行风向随高度的增加呈顺时针旋转，510m高度以下风速基本小于3.0m/s，其中08：00至20：00，390m高度以下风速小于2.0m/s；清洁过程中510~1590m和2790~3000m存在风速大于5.0m/s的高值中心，1830m高度以下，清洁过程各层的平均风速明显高于灰霾过程；（2）贴地逆温与能见度总体上呈负相关，与PM_2.5浓度呈正相关，相关系数分别为-0.367和0.455，而当贴地逆温和低空逆温同时存在时，其相关性更高，其相关系数分别为-0.5和0.601，说明多层逆温的存在更容易出现灰霾天气.灰霾过程中，低空逆温与能见度和PM_2.5的相关不明显，而清洁过程中，低空逆温的出现主要与冷空气南下有关，其与能见度呈正相关（0.217），和PM_2.5浓度呈负相关（-0.64），低空逆温不利于灰霾天气形成；（3）灰霾过程中，贴地逆温出现频率为60.68%，平均逆温强度为1.38℃/100m，平均逆温厚度为153.20m，明显高于清洁过程；清洁过程中，低空逆温的逆温强度、厚度和出现频率分别为0.27℃/100m、691.07m和64.61%，明显高于灰霾过程.（4）清洁过程的混合层高度明显高于灰霾过程，清洁过程的日均混合层高度（958.92m）是灰霾过程（398.03m）的2.4倍.

Comparative analysis on the boundary layer features of haze processes and cleaning process in Guangzhou

Base on the ground weather data and data of microwave radiometer and wind profile from 2014 to 2016 in Guangzhou national climate observatory, the characteristics of boundary layer structure of the typical during haze processes and cleaning process in Guangzhou are studied. The results are showed as follows:(1) In haze process, the wind speed decreases with height below 270m, but increases with height over 270m, and the increase rate of wind speed below 2000m is lower than that over 2000m. The prevailing wind direction rotates clockwise with height. The wind speed below 510m height is basically less than 3.0m/s, and from 08am to 20pm, the wind speed is less than 2.0m/s below 390m. In cleaning process, there is a speed higher than 5.0m/s zone at 510~1590m and 2790~3000m respectively. Below the height of 1830m, the average wind speed of each layer in the cleaning process is obviously higher than that in haze process. (2) The low temperature inversion was negatively correlated with visibility and positively correlated with concentration of PM_2.5, and the correlation coefficients are -0.367 and 0.455respectively. The correlation coefficients is higher when the low temperature inversion and low altitude inversion are simultaneously, and the correlation coefficients are -0.5 and 0.601, respectively. It shows that the existence of multilayer inversion is more prone to haze weather. In haze process, the correlation of low altitude inversion to visibility and PM_2.5 was not obvious. In cleaning process, the occurrence of low altitude inversion was mainly related to the cold air coming down from the north, which was positively correlated with visibility (0.217), and negatively correlated with the concentration of PM_2.5(-0.64). Low altitude inversion is not conducive to the formation of haze weather. (3) During haze process, the frequency of the low temperature inversion is 60.68%, the average inversion intensity is 1.38℃/100m, and the average inversion layer thickness is 153.2m, which is obviously higher than that of the cleaning process. During cleaning process, the average frequency of occurrence, inversion intensity and inversion layer thickness of low temperature inversion are 64.61%, 0.27℃/100m and 691.07m respectively, which are significantly higher than those of haze process. (4) The mixing layer height of cleaning process is obviously higher than that of the haze process. The daily mixing layer height (958.92m) of cleaning process is 2.4times that of haze process (398.03m).