| Popis: |
The raindrop size distribution (RSD) and parameter characteristics of different climate regions, rain types, topographies or weather systems have been extensively studied focusing on summer precipitation. However, even microphysical characteristics of precipitation in the same region can show significant seasonal differences. Seasonal distribution characteristics of RSD with different rain rates and rainfall types in Taiyuan are investigated and compared with conclusions from other regions based on observations of precipitation phenomenometer from December 2017 to November 2022. It can provide references for localized application of the parameterization of rainfall microphysics in numerical weather and climate prediction models, the rainfall kinetic energy flux estimation and the radar quantitative precipitation estimation. In addition, satellite measurements, ground observations, and reanalysis data are applied to explain the possible mechanism of seasonal differences in RSD. The RSD presents a unimodal structure with a peak of 0.562 mm and the decrease trend of concentration is more obvious in winter. Small raindrops with diameter less than 1.0 mm contribute more than 80% of the total number concentration, while the rain rate (R) is contributed primarily from mid-size raindrops with diameter of 1-2 mm during all seasons. The rainfall with R < 1 mm·h-1 are most frequent in different seasons, but the rainfall with R ≥ 5 mm·h-1 is predominant in summer. For the RSD of different rain rate, the highest (lowest) concentration of large (small) raindrops in winter is observed from the first two rain rate classes, while the concentration is higher in summer when the rain rate exceeds 5 mm·h-1. Rainfall at Taiyuan is dominated by stratiform rain throughout the year, lgNw or Dm has minor seasonal differences, and the distribution of lgNw and Dm is more similar to Nanjing. The convective rain occurs most often during summer and is close to the maritime-like cluster, the convective rain during spring and autumn is neither continental nor maritime, and there is no convective rain in winter. The stratiform rain has a wider spectrum width and higher concentration compared with the convective rain. μ-λ, Et-R, Ed-Dm, and Z-R relationships are derived by the least square method for different seasons. μ-λ relationships change little with seasons, but vary significantly compared with Florida in America. The power function and the binomial function has better fitting performance for Et-R and Ed-Dm, respectively. There is an inverse relationship between the coefficient and the exponent of the Z-R relationships. For stratiform rain, the classical relationship overestimates rainfall in spring and autumn, while the classical relationship turns from overestimated to underestimated as the rain rate increases. For convective rain, the classical relationship overestimates rainfall slightly in summer and autumn. |
