Sun Yue, Xiao Hui, Feng Qiang, et al. Rainfall Enhancement and Fog Dissipation Experiments in Wuling Mountain in 2020 using artificial strong sound wave. J Appl Meteor Sci, 2024, 35(1): 90-102. DOI:  10.11898/1001-7313.20240108.
Citation: Sun Yue, Xiao Hui, Feng Qiang, et al. Rainfall Enhancement and Fog Dissipation Experiments in Wuling Mountain in 2020 using artificial strong sound wave. J Appl Meteor Sci, 2024, 35(1): 90-102. DOI:  10.11898/1001-7313.20240108.

Rainfall Enhancement and Fog Dissipation Experiments in Wuling Mountain in 2020 Using Artificial Strong Sound Wave

DOI: 10.11898/1001-7313.20240108
  • Received Date: 2023-10-24
  • Rev Recd Date: 2023-12-07
  • Publish Date: 2024-01-31
  • Low-frequency sound wave is a new type of operational approach that has the potential for enhancing rainfall and dissipating fog. To investigate the impact of this type of equipment, field operations and observational experiments are conducted in Wuling Mountain from August to September 2020. Wuling Mountain is located at Chengde of Hebei outside the northeastern boundary of Beijing. The main peak of the Yanshan Mountains is renowned for its foggy summers with an altitude of 2118 m. In the experiment, a prototype of an electronic acoustic low-frequency strong sound wave device is used. This device has a maximum sound pressure level of 155 dB. Meanwhile, observation instruments such as a disdrometer, visibility meter, fog droplet spectrometer, and automatic weather station with an ultrasonic anemometer are deployed. These instruments are used to obtain the background conditions and to monitor macro and micro changes during rainfall enhancement and fog dissipation operations for evaluating the effectiveness.In two typical cases with an obvious defogging effect, within 2 to 3 minutes after the start of the operation, the number of droplets smaller than 10 μm decreased, while the number of droplets larger than 10 μm increased. Subsequently, the size of the droplets on most scales decreased significantly, resulting in improved visibility. Within a span of 10 minutes, visibility could increase from less than 100 m to a maximum of 1000 m. The relationship between wind speed, wind direction, and the dissipation effect of fog shows that cases with a noticeable defogging effect occur when the average wind speed is less than 1.5 m·s-1 and the wind direction causes the fog to pass through the near side of the influence range of the sound wave device, while cases with an average wind speed greater than 2 m·s-1 hardly show any change in visibility trends. Results, which align with the experimental expectations, are observed during an operation on a convective cloud precipitation when the surface mean wind speed is 1.4 m·s-1. In this case, the rainfall intensity increases rapidly from 0.3 mm·h-1 to more than 7 mm·h-1 within 3 min of operation, and large raindrops with rapid occurrence but short duration are observed. In other rainfall enhancement experimental cases, the average wind speed exceeded 3 m·s-1 during the operation period, and no clear and consistent evidence of increased rainfall is observed, which may be affected by the high wind speeds and only one single observation point.
  • Fig. 1  Location of temporary experiment site on the top of Wuling Mountain

    (the box, the shaded denotes altitude) (a) and placement of observation instruments (A denotes the placement of artificial strong sound wave device on the ground platform, B denotes the placement of laser disdrometer and automatic weather station on the roof, C denotes the placement of fog droplet spectrometer and visibility meter; the blue arrow denotes the fog moving direction, the red arrow denotes the direction of artificial sound wave for fog dissipation) (b)

    Fig. 1  Location of temporary experiment site on the top of Wuling Mountain

    (the box, the shaded denotes altitude) (a) and placement of observation instruments (A denotes the placement of artificial strong sound wave device on the ground platform, B denotes the placement of laser disdrometer and automatic weather station on the roof, C denotes the placement of fog droplet spectrometer and visibility meter; the blue arrow denotes the fog moving direction, the red arrow denotes the direction of artificial sound wave for fog dissipation) (b)

    Fig. 2  Sound pressure level varying with frequency and distance

    Fig. 2  Sound pressure level varying with frequency and distance

    Fig. 3  Directional images of sound pressure level of artificial strong sound wave device

    Fig. 3  Directional images of sound pressure level of artificial strong sound wave device

    Fig. 4  Visibility and fog size distribution parameters during fog dissipation experiments on 23 Aug 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 4  Visibility and fog size distribution parameters during fog dissipation experiments on 23 Aug 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 5  Fog droplet size distribution during four fog dissipation operation periods on 23 Aug 2020

    Fig. 5  Fog droplet size distribution during four fog dissipation operation periods on 23 Aug 2020

    Fig. 6  ERA5 surface wind in the surrounding area of Wuling Mountain during fog dissipation operations on 23 Aug 2020

    (△ denotes Wuling Mountain, the blue vector denotes wind at 1800 BT, the red vector denotes wind at 1900 BT)

    Fig. 6  ERA5 surface wind in the surrounding area of Wuling Mountain during fog dissipation operations on 23 Aug 2020

    (△ denotes Wuling Mountain, the blue vector denotes wind at 1800 BT, the red vector denotes wind at 1900 BT)

    Fig. 7  Examples of visibility changes during fog dissipation experiments in 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 7  Examples of visibility changes during fog dissipation experiments in 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 8  Relationship between wind speed of automatic weather station and visibility change for 21 fog dissipation operations from 27 Aug to 10 Sep in 2020

    Fig. 8  Relationship between wind speed of automatic weather station and visibility change for 21 fog dissipation operations from 27 Aug to 10 Sep in 2020

    Fig. 9  Rainfall intensity and raindrop size distribution before and after the first operations during rainfall enhancement experiments on 7 Sep 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 9  Rainfall intensity and raindrop size distribution before and after the first operations during rainfall enhancement experiments on 7 Sep 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 10  Rainfall intensity during rainfall enhancement experiments from 10 to 11 in Sep 2020

    (the numbered shaded area denotes sequential operation period)

    Fig. 10  Rainfall intensity during rainfall enhancement experiments from 10 to 11 in Sep 2020

    (the numbered shaded area denotes sequential operation period)

    Table  1  Information of wind and cloud during rainfall enhancement experiments in 2020

    试验时段 开机次数 平均风速/(m·s-1) 云类型
    09-07T15:38—16:00 4 1.4 对流云
    09-10T06:54—07:20 3 3.1 层状云
    09-10T08:46—10:11 9 3.3 层状云
    09-11T11:23—12:03 3 3.0 层状云
    09-11T16:53—17:33 3 3.6 层状云
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    Table  1  Information of wind and cloud during rainfall enhancement experiments in 2020

    试验时段 开机次数 平均风速/(m·s-1) 云类型
    09-07T15:38—16:00 4 1.4 对流云
    09-10T06:54—07:20 3 3.1 层状云
    09-10T08:46—10:11 9 3.3 层状云
    09-11T11:23—12:03 3 3.0 层状云
    09-11T16:53—17:33 3 3.6 层状云
    DownLoad: Download CSV
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    • Received : 2023-10-24
    • Accepted : 2023-12-07
    • Published : 2024-01-31

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