Characterization of liquid water content during low visibility based on microwave radiometer data
LIAO Bi-ting1, HUANG Jun2, DENG Xue-jiao3, WANG Chun-lin2, WANG Si-hua1, HUANG Xiao-yun1, SUN Dao-dong1
1. Guangzhou Huangpu Meteorology, Guangzhou 510530, China;
2. Guangzhou Climate and Agrometeorology Center, Guangzhou 511430, China;
3. Institute of Tropical Marine and Meteorology, China Meteorological Administration, Guangzhou 510080, China
We characterized the temporal variations of visibility (Vis), relative humidity (RH) and liquid water profile (LPR) during low visibility periods based on the visibility, cloud and microwave-radiometer-detected liquid water content data provided by the national basic meteorological station in Guangzhou from November 2013 to April 2014. Results showed that the occurrence frequency of Vis<10km was 66.37%. Vis ≤ 1km happened when RH ≥ 95%, and 1km 90%. Vis>5km did not occur when RH>95% and Vis>15km never happened at RH> 90%. Low visibility events tended to happen more frequently in the morning than in the evening and seldom occurred during noontime. This was consistent with the variations of LPR in the corresponding period, indicating that low visibility events may correlate positively with the high liquid water content in the lower atmosphere. The integral liquid water content of the atmosphere was generally high when Vis < 10km. The high liquid water content exceeding 0.02g/m3 was normally observed in the atmosphere below 3km, with the maximum liquid water approximately appeared at 1550m height. The liquid water content was relatively low in the case of Vis ≥ 10km, which seldom exceeded 0.02g/m3 and the maximum value of which was usually observed at a height of approximately 2km. Less than 50% of the low visibility events in Guangzhou was introduced by the formation process of low cloud (or low cloud reaching the ground to form fog). When Vis ≤ 1km, LPR was observed to be nearly zero as no liquid water content was detected by the microwave radiometer. Simultaneously, it is worth noting that the ground-level aerosol loading was quite high (PM2.5>88.3μg/m3) when RH > 95% and the atmosphere was approaching saturation condition, suggesting that low visibility events (Vis ≤ 1km) in Guangzhou could be attributed to the combination of fog and haze. This highlights the need for comprehensive analysis of the liquid water content from microwave radiometer measurements, relative humidity, and particle mass concentration in order to further distinguish haze pollution from fog and/or mixed fog and haze phenomena.
廖碧婷, 黄俊, 邓雪娇, 王春林, 王四化, 黄晓云, 孙道东. 基于微波辐射计分析低能见度的液态含水量特征[J]. 中国环境科学, 2018, 38(10): 3673-3682.
LIAO Bi-ting, HUANG Jun, DENG Xue-jiao, WANG Chun-lin, WANG Si-hua, HUANG Xiao-yun, SUN Dao-dong. Characterization of liquid water content during low visibility based on microwave radiometer data. CHINA ENVIRONMENTAL SCIENCECE, 2018, 38(10): 3673-3682.
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