Anomalous holiday precipitation over southern China
The Chinese Spring Festival (CSF, also known as the Chinese New Year or Lunar New Year) is the most important festival in China. Lunar New Year's Day (LNYD) is the first day of the Lunar New Year. Traditionally, the CSF holiday begins a couple of days before LNYD and ends on lantern day, lasting for approximately 2 weeks. In this paper, based on the long-term station observations from 1979 to 2012, the precipitation during the holiday over southern China (108–123° E and 21–33° N, 155 stations) tends to be lower than that before and after the holiday. The mean precipitation frequency anomaly from the fourth day to the sixth day after LNYD (i.e., days [+4, +6]) decreases by –7.4 %. Simultaneously, the daily precipitation amount experiences a reduction of –0.62 mm day–1 during days [+2, +5]. The holiday precipitation anomalies are strongly linked to the anomalies of relative humidity (ΔRH) and cloud cover. The station observations of the ΔRH show an evident decrease from day +2 to day +7, and a minimum appears on days [+4, +6], with a mean of –3.9 %. The ΔRH vertical profile displays significant drying below approximately 800 hPa. Between 800 and 1000 hPa, the mean ΔRH is –3.9 %. The observed station daytime low cloud cover (LCC) evidently decreases by –6.1 % during days [+4, +6]. Meanwhile, the ERA-Interim daily LCC also shows a comparable reduction of –5.0 %. The anomalous relative humidity is mainly caused by the decreased water vapor in the lower-middle troposphere. Evident negative specific humidity anomalies persist from day –3 to day +7 in the station observations. The average specific humidity anomaly for days [+4, +6] is –0.73 g kg–1. When the precipitation days are excluded, the anomaly remains significant at –0.46 g kg–1. A significant water vapor deficit is observed in the lower troposphere below 700 Pa. Between 800 and 1000 hPa, the mean specific humidity drops by –0.70 g kg–1. This drier lower-middle troposphere is due to anomalous northerly winds, which are closely related to the cyclonic circulation anomaly over the northwestern Pacific. The time-lag correlation demonstrates that approximately 1 week after a lower temperature occurs over eastern China, a stronger cyclone is observed over the western Pacific. The possible mechanism needs further clarification through elaborate observation and numerical modeling.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER); State Key Laboratory of Earth Surface Processes and Resource Ecology; National Natural Science Foundation of China (NSFC)
- Grant/Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1631692
- Report Number(s):
- PNNL-SA-140996
- Journal Information:
- Atmospheric Chemistry and Physics (Online), Vol. 18, Issue 22; ISSN 1680-7324
- Publisher:
- European Geosciences UnionCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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