Page 235 - 《高原气象》2022年第6期

高 原 气 象 41 卷
1598

The Impact of Surface Synoptic Circulation Types on Air Quality and

the PM Concentration Forecast in Fen-Wei Plains
2.5

1，2
2，3
LIU Hui ，ZHANG Xuting ，HUANG Xin ，HU Bo 4
1
（1. Shaanxi Meteorological Observatory，Xi’an 710014，Shaanxi，China；
2. Key Laboratory of Eco-Environment and Meteorology for the Qinling Mountains and Loess Plateau，Xi’an 710014，Shaanxi，China；
3. Shaanxi Meteorological Information Center，Xi’an 710014，Shaanxi，China；
4. State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry，Institute of Atmospheric Physics，
Chinese Academy of Sciences，Beijing 100029，China）

Abstract：Based on the sea level pressure data from 2014 to 2018，Lamb-Jenkinson（L-J）atmospheric circula‐
tion classification scheme was used to classify the surface synoptic circulation types during air pollution seasons
in Fen-Wei Plains and their relationships with the PM 2. 5 concentration and surface meteorological elements were
analyzed. Combining the observed PM 2. 5 mass concentration and mixing layer height，relative humidity，wind
speed，retention index，a PM 2. 5 concentration forecast model was established in each city under different surface
synoptic circulation types. The results show：（1）Occurrence frequencies of different surface circulation types
vary，under which the distributions of PM concentration and meteorological elements differentiate also. Under
2. 5
controls of circulation types South（S），South East（SE），East（E）and cyclone（C）the ratio of PM 2. 5 polluted
days proportion to PM 2. 5 polluted days proportion under all synoptic circulation types were more than 1，corre‐
sponding to a larger product of the occurrence frequency and the pollution days，which will lead to PM 2. 5 pollu‐
tion events easily.（2）In the case of mild or above pollution in Xi 'an，the mixed layer height ranged from 483. 5
m to 601. 38 m，the relative humidity ranged from 42. 94% to 64. 03%，the wind speed ranged from 1. 45 m∙s -1
-1
to 2. 61 m∙s and the retention index ranged from 0. 13 to 0. 53. Under controls of circulation types S，SE，E and
-1
C the average mixed layer height was 488. 98 m，the average wind speed was 1. 89 m∙s and the average reten‐
tion index was 0. 46. Except for under type C，the mixed layer height was below 500 m on more than 60% of the
sites，and the relative humidity over 60% on more than 50% of the sites. The wind speed was below 2 m∙s with
-1
a retention index more than 0. 4 on more than 60% of the sites under all four circulation types.（3）According to
the PM concentration forecast models for different circulation patterns in each city，there exists a 0~1 level dif‐
2. 5
ference between predicted level and measured level about 82% of all samples，where about 37% of all samples
were perfectly consistent. The predicted PM 2. 5 values from 2019 to 2020 were larger compared with the measured
PM 2. 5 values，and the average absolute deviation values were close to the values of 2014-2018 years，indicating
that the forecast accuracy and stability of the forecast models were good. From 2019 to 2020，there exists a 0~1
level difference between predicted level and measured level among 80% of all samples，where about 33% of all
samples were perfectly consistent.
Key words：Synoptic circulation types；PM 2. 5 mass concentration；meteorological factors；forecast model