Abstract

Raindrop size distribution (DSD) can reflect the fundamental microphysics of precipitation and provide an accurate estimation of its amount and characteristics; however, there are few observations and investigations of DSD in cold, mountainous regions. We used the second-generation particle size and velocity disdrometer Parsivel2 to establish a quality control scheme for raindrop spectral data obtained for the Qinghai–Tibet Plateau in 2015. This scheme included the elimination of particles in the lowest two size classes, particles >10 mm in diameter and rain rates <0.01 mm∙h−1. We analyzed the DSD characteristics for different types of precipitation and rain rates in both permafrost regions and regions with seasonally frozen ground. The precipitation in the permafrost regions during the summer were mainly solid with a large particle size and slow fall velocity, whereas the precipitation in the regions with seasonally frozen ground were mainly liquid. The DSD of snow had a broader drop spectrum, the largest particle size, the slowest fall velocity, and the largest number of particles, followed by hail. Rain and sleet shared similar DSD characteristics, with a smaller particle size, slower velocity, and smaller number of particles. The particle concentration for different classes of rain rate decreased with an increase in particle size and decreased gradually with an increase in rain rate. Precipitation with a rain rate >2 mm∙h−1 was the main contributor to the annual precipitation. The dewpoint thresholds for snow and rain in permafrost regions were 0 and 1.5 °C, respectively. The dewpoint range 0–1.5 °C was characterized by mixed precipitation with a large proportion of hail. This study provides valuable DSD information on the Qinghai–Tibet Plateau and can be used as an important reference for the quality control of raindrop spectral data in regions dominated by solid precipitation.

Highlights

  • Accurate observation of precipitation is essential for research and applications of regional to global climate, hydrology and ecology, calibration of remote sensing products [1,2]

  • We analyzed the differences between the two data quality control schemes applied in different regions and for different types of precipitation

  • The observation results from July to August 2015 showed that the DSD characteristics in summer were clearly different at the Tanggula and Naqu observation sites

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Summary

Introduction

Accurate observation of precipitation is essential for research and applications of regional to global climate, hydrology and ecology, calibration of remote sensing products [1,2]. The climate in the permafrost regions of the Qinghai–Tibet Plateau is extremely cold and windy, with snowfall exceeding 40% of the annual precipitation and daily mean wind speeds >4 m·s−1 [7,8,9,10,11]. The operation period of these stations are both short and inconsistent. These factors limit reliability of precipitation data over the Qinghai–Tibet Plateau [6]. Precipitation and snow cover are the two most important factors affecting thermal condition of permafrost after temperature; intensity and phase of precipitation have different effects on the thermal status of the surface, they influence he development of, and changes in, the permafrost layer [13,14]

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