Distribution characteristics of the summer precipitation raindrop spectrum on the Qinghai–Tibet Plateau
<p>To enhance the precision of precipitation forecasting in the Qinghai–Tibet Plateau region, a comprehensive study of both macro- and micro-characteristics of local precipitation is imperative. In this study, we investigated the particle size distribution, droplet velocity, droplet number den...
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| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-12-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/17/6933/2024/amt-17-6933-2024.pdf |
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| Summary: | <p>To enhance the precision of precipitation forecasting in the Qinghai–Tibet Plateau region, a comprehensive study of both macro- and micro-characteristics of local precipitation is imperative. In this study, we investigated the particle size distribution, droplet velocity, droplet number density, <span class="inline-formula"><i>Z</i></span>–<span class="inline-formula"><i>I</i></span> (radar reflectivity–rainfall intensity) relationship, and gamma distribution of precipitation droplet spectra with a single precipitation duration of at least 20 min and precipitation of 5 mm or more at four stations (Nyalam, Lhasa, Shigatse, and Naqu) in Tibet during recent years from June to August. The results are as follows: (1) in the fitting relationship curve between precipitation raindrop spectral particle size and falling speed at the four stations in Tibet, when the particle size was less than 1.5 mm, the four lines essentially coincided. When the particle size exceeded 1.5 mm, the speed in Nyalam was the highest, followed by Naqu, and the speed in Lhasa was the lowest. The falling speed of particles correlated with altitude. (2) The five microphysical characteristics (mean diameter (<span class="inline-formula"><i>D</i><sub>m</sub></span>), average volume diameter (<span class="inline-formula"><i>D</i><sub>v</sub></span>), mode diameter (<span class="inline-formula"><i>D</i><sub>d</sub></span>), dominant diameter (<span class="inline-formula"><i>D</i><sub>p</sub></span>), and median diameter (<span class="inline-formula"><i>D</i><sub>nd</sub></span>)) at the four stations have different correlation relationships with altitude under different rainfall intensities. <span class="inline-formula"><i>D</i><sub>m</sub></span> exhibits a negative correlation with altitude at the same rainfall intensity; in contrast, <span class="inline-formula"><i>D</i><sub>v</sub></span> shows a positive correlation with altitude. For microphysical parameters such as <span class="inline-formula"><i>D</i><sub>d</sub></span> and <span class="inline-formula"><i>D</i><sub>p</sub></span>, a rainfall intensity of 10 mm h<span class="inline-formula"><sup>−1</sup></span> serves as the boundary line, and they have different correlation relationships with altitude under the same rainfall intensity level. (3) The <span class="inline-formula"><i>Z</i></span>–<span class="inline-formula"><i>I</i></span> relationships at the four stations exhibited variations. Owing to the proximity in altitude between Lhasa and Shigatse, as well as between Nyalam and Nagqu, the coefficient <span class="inline-formula"><i>a</i></span> and index <span class="inline-formula"><i>b</i></span> in the <span class="inline-formula"><i>Z</i></span>–<span class="inline-formula"><i>I</i></span> relationships of the two groups of sites were relatively similar. (4) The fitting curves of the exponential and gamma distributions of the precipitation particle size at the aforementioned four stations are largely comparable. The exponential distribution fitting exhibits a slightly better effect. The parameter <span class="inline-formula"><i>μ</i></span> in the gamma distribution decreases with an increase in altitude, while <span class="inline-formula"><i>N</i><sub>0</sub></span> and <span class="inline-formula"><i>λ</i></span> in the exponential distribution show a clear upward trend with altitude.</p> |
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| ISSN: | 1867-1381 1867-8548 |