Aerosol-induced changes in the vertical structure of precipitation: a perspective of TRMM precipitation radar

Abstract

Abstract. Our knowledge is still poor regarding the response of the precipitation vertical structure to aerosols, partly due to the ignorance of precipitation occurring at different spatial scales. A total of 6 years of collocated ground-based PM10 and satellite-based (Tropical Rainfall Measuring Mission, TRMM) radar data, along with ERA-Interim reanalysis, are used in this study to investigate the aerosol effects on three localized rain regimes (shallow, stratiform, and convective rain) over the Pearl River Delta region of China. A subjective analysis method is proposed to discriminate between the localized and synoptic-scale precipitations based on weather composite charts where daily averaged wind field at 850 hPa is overlaid with the geopotential height at 500 hPa. In general, average rain rate tends to be greater under polluted conditions than under clean conditions. But such potential aerosol effects are regime dependent: as the atmosphere becomes slightly polluted (PM10≤38 µg m−3), the top 1 % radar reflectivity (Z) for all regimes initially increases, followed by continued increases and weak decreases for convective and stratiform/shallow rain regimes, respectively. As the atmosphere becomes much more polluted, such regime dependences of aerosol effects are more significant. From a perspective of the vertical Z structure, comparisons between polluted conditions (days with the highest third of PM10 concentration) and clean conditions (days with the lowest third of PM10 concentration) show that the convective rain regime exhibits a deeper and stronger Z pattern, whereas a much shallower and weaker Z pattern is observed for stratiform and shallow precipitation regimes. In particular, the top height of the 30 dBZ rain echo increases by ∼29 % (∼1.27 km) for the convective regime, but decreases by ∼10.8 % (∼0.47 km) for the stratiform regime. However, no noticeable changes are observed for the shallow precipitation regime. Impacts of meteorological factors are further studied on both rain top height (RTH) and the center of gravity of Z, including vertical velocity, vertical wind shear, convection available potential energy, and vertically integrated moisture flux divergence (MFD). The possible invigoration effect on convective precipitation seems dependent on wind shear, in good agreement with previous findings. Overall, the observed dependence of the precipitation vertical structure on ground-based PM10 supports the notion of aerosol invigoration or suppression effect on cold or warm rain and adds new insights into the nature of the complex interactions between aerosol and various localized precipitation regimes.

Anthropogenic Aerosols Significantly Reduce Mesoscale Convective System Occurrences and Precipitation Over Southern China in April

“…Below 1 km, the RADAR reflectivity under the MCSs shifted slightly toward smaller values under polluted conditions due to an 8.7% radius-reduction of raindrops, which likely evaporated more quickly. Overall, the RADAR reflectivity of MCSs under polluted conditions was invigorated at midlevel and shifted toward lower values near the surface (Figure 3c), consistent with observations (Guo et al, 2018). However, the rainfall reaching the surface from individual MCSs was not significantly different in the polluted and clean simulations ( Figure S7c).…”

Variability in vertical structure of precipitation with sea surface temperature over the Arabian Sea and the Bay of Bengal as inferred by Tropical Rainfall Measuring Mission precipitation radar measurements

“…The aforementioned studies mainly focused on the morphology of vertical structure of precipitation, but none of them studied the variation in vertical structure of precipitation (in terms of occurrence and intensity) with SST and the differences in the vertical structure over AS and BOB. On the other hand, information on the vertical structure of precipitation is essential for improving the accuracy of rainfall estimation (Fu and Liu, 2001;Sunilkumar et al, 2015), understanding the dynamical and microphysical processes of hydrometeor growth-decay mechanisms (Houze, 2004;Geets and Dejene, 2005;Saikranthi et al, 2014;Rao et al, 2016), and improving the latent heating retrievals (Tao et al, 2006(Tao et al, , 2016. SST being the main driving force to trigger precipitating systems through air-sea interactions (Sabin et al, 2012;Nuijens et al, 2017) can alter the vertical structure of precipitation (Oueslati and Bellon, 2015).…”

Local Severe Storm Tracking and Warning in Pre-Convection Stage from the New Generation Geostationary Weather Satellite Measurements

“…The summer precipitation generally contributes more than 50% of annual precipitation [48]. Since the precipitation area and the Intertropical Convergence Zone (ITCZ) have moved northward [49], Shandong Province will be frequently subjected to severe convective storm weather systems in the summer season (June, July, and August) as shown in Figure 1. The detailed process of this convection is shown in Figure 6.…”