Abstract
Precipitation efficiency (PE) is a crucial physical quantity in convective processes, describing the efficiency of rainfall generation from cloud detrainment. Although the importance of PE in extreme precipitation events is widely accepted, the evolution of PE in the warming climate and the associated moisture processes in East Asia are still not well understood. To address these issues, the interdecadal variability of PE in East Asia during summer in 1979–2016 is investigated in this study. Two major modes of summertime precipitation efficiency are identified using Empirical Orthogonal Function (EOF) analysis. The leading EOF mode (EOF1) has a dipole pattern that reveals the variations of mean precipitation efficiency. The second EOF mode (EOF2) presents a quadrupole pattern that shows changes in the variability of precipitation efficiency. Both EOF modes exhibit significant interdecadal variability (IDV). The IDV of EOF1 is closely associated with the phase change of the Pacific decadal oscillation (PDO). The Pacific sea surface temperature anomalies associated with the PDO can excite wind anomalies that significantly modulate moisture transport and further alter the mean precipitation efficiency in East Asia. The IDV of EOF2 can be attributed to the interdecadal change of occurrence frequency of Eastern Pacific El Niño-Southern Oscillation (ENSO) events, which affect water vapor transport by inducing an East Asia-Pacific teleconnection-like wave train anomaly pattern. The IDV patterns of precipitation efficiency for both the mean value and variability will improve the ability to predict precipitation in East Asia.
Highlights
Precipitation efficiency (PE) is an important physical quantity of a convective system that characterizes the efficiency of rainfall generation via water vapor from cloud detrainment
South of 35°N, precipitation, and PE exhibit opposite variations to their northward counterparts, with total precipitable water still decreasing, all of these changes are statistically insignificant. e spatial distribution of the PE difference has a center near the north pole of the EOF1 dipole. e results suggest that the atmospheric response to the Pacific decadal oscillation (PDO) phase change leads to the interdecadal variability (IDV) of mean PE in East Asia
E Empirical Orthogonal Function (EOF) analysis of PE has revealed two major modes of IDV, where PC1 represents changes in mean value and PC2 corresponds to transitions of the variability. e PC1 IDV changed during 1998–1999, with a meridional negativepositive dipole pattern during 1983–1998 and the opposite dipole distribution during 1999–2011. e PC2 IDV changed during 1999–2000 with a prominent negativepositive-negative-positive quadrupole structure during 1979–1999 and a much weaker structure during 2000–2016
Summary
Precipitation efficiency (PE) is an important physical quantity of a convective system that characterizes the efficiency of rainfall generation via water vapor from cloud detrainment. Previous studies suggest that ice clouds have a significant impact on the organization of tropical convection that affects PE in terms of both microphysical processes and radiative effects [23,24,25]. Variations of atmospheric circulation have a significant impact on the water vapor sources of precipitation by altering the moisture transport pathway, convective intensity, and water vapor condensation and deposition in cumulus clouds [23, 24, 37, 38]. As a major monsoon system, the East Asian monsoon is an important modulator of the East Asian climate, which shapes the seasonal march of major rain belts and the Meiyu-Baiu rains with its significant variability from intraseasonal to interdecadal scales [26] It affects the ENSO-related teleconnections that extend the influence to the global scale [39].
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