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- Fu, Yunfei, et al.
(author)
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Fundamental Characteristics of Tropical Rain Cell Structures as Measured by TRMM PR
- 2020
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In: Journal of Meteorological Research. - : Springer Science and Business Media LLC. - 2095-6037 .- 2198-0934. ; 34:6, s. 1129-1150
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Journal article (peer-reviewed)abstract
- Rain cells are the most elementary unit of precipitation system in nature. In this study, fundamental geometric and physical characteristics of rain cells over tropical land and ocean areas are investigated by using 15-yr measurements of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The rain cells are identified with a minimum bounding rectangle (MBR) method. The results indicate that about 50% of rain cells occur at length of about 20 km and width of 15 km. The proportion of rain cells with length > 200 km and width > 100 km is less than 1%. There is a a log-linear relationship between the mean length and width of rain cells. Usually, for the same horizontal geometric parameters, rain cells tend to be square horizontally and lanky vertically over land, while vertically squatty over ocean. The rainfall intensity of rain cells varies from 0.4 to 10 mm h(-1) over land to 0.4-8 mm h(-1) over ocean. Statistical results indicate that the occurrence frequency of rain cells decreases as the areal fraction of convective precipitation in rain cells increases, while such frequency remains almost invariant when the areal fraction of stratiform precipitation varies from 10% to 80%. The relationship between physical and geometric parameters of rain cells shows that the mean rain rate of rain cells is more frequently associated with the increase of their area, with the increasing rate over land greater than that over ocean. The results also illustrate that heavy convective rain rate prefers to occur in larger rain cells over land while heavy stratiform rain rate tends to appear in larger rain cells over ocean. For the same size of rain cells, the areal fraction and the contribution of convective precipitation are about 10%-15% higher over land than over ocean.
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| 2. |
- Zhang, Aoqi, et al.
(author)
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Structure of Cyclonic Precipitation in the Northern Pacific Storm Track Measured by GPM DPR
- 2020
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In: Journal of Hydrometeorology. - 1525-755X .- 1525-7541. ; 21:2, s. 227-240
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Journal article (peer-reviewed)abstract
- Despite the long existence of theoretical studies, few statistical studies of precipitation characteristics on the northern Pacific storm track have been reported due to lack of observation. Using data from GPM DPR and ERA-Interim, we examined the precipitation features of extratropical cyclones in the northern Pacific storm-track region. Extratropical cyclones were classified into four categories including developing, mature, dissipating, and short-term based on their life stages. Our results show that extratropical cyclones of all categories had a comma rainband and precipitation mostly occurred to the east of the cyclonic center. The extratropical cyclones promote precipitation to the east of their centers, but suppress precipitation to the west. Precipitation to the east of the extratropical cyclones had larger and more condensed droplets, a stronger intensity, and a higher rain top than the local seasonal average, while the opposite characteristics were seen to the west. Our results suggest that the different types of vertical air motion and moisture content in these two regions induced by the frontal structure of extratropical cyclones play important roles in the different impact of extratropical cyclones. Furthermore, the different life stages of extratropical cyclones had different degrees of impact on precipitation: the highest impact in the developing stage, followed by the mature stage, and the weakest impact in the dissipating stage.
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