Precipitation and the Associated Moist Static Energy Budget off Western Australia in Conjunction with Ningaloo Niño

Tao Zheng,Xuhua Cheng,Kang Xu,Tao Feng

doi:10.3389/feart.2020.597915

Abstract

Ningaloo Nino is a well-known ocean-atmosphere coupled climate event in the southeastern Indian Ocean that interacts with large-scale atmospheric circulations at the interannual time scale. When a Ningaloo Nino develops, remarkably enhanced precipitation anomalies occur primarily off the coast of northwestern Australia (NWA) rather than over the offshore area of western Australia (WA), where the most significant sea surface temperature warming prevails. This enhanced NWA precipitation manifests as jointly intensified stratiform and convective precipitation accompanied by an increase in high cloud cover. Further analyses of the column-integrated moist static energy (MSE) budget reveal that during Ningaloo Nino events, positive vertical MSE transport moistens and heats the atmosphere in the WA region. However, these moistening and heating effects are mostly offset by the inhibitory effect of the negative horizontal MSE advection, leading to the relatively weak and nonsignificant variation in local precipitation anomalies off the WA coastal region. In contrast, off the coast of the NWA region, the recharge of column-integrated MSE, which is induced by the significant positive radiative and surface heating, horizontal MSE advection, and vertical MSE advection, contributes to the heaviest austral summer precipitation associated with Ningaloo Nino. Therefore, the distinct MSE transport processes result in the particular rainfall pattern in which the most enhanced rainfall is associated with Ningaloo Nino events over the NWA region.

Highlights

Ningaloo Niño events are significantly correlated with El Niño-Southern Oscillation (ENSO), the Indian Ocean dipole (IOD) and the Interdecadal Pacific Oscillation (Feng et al, 2013; Pearce and Feng, 2013; Kataoka et al, 2014; Tozuka et al, 2014; Zhang et al, 2018; Zhang and Han, 2018; Kusunoki et al, 2020; Tanuma and Tozuka, 2020), recent studies have demonstrated that Ningaloo Niño/Niña events independently exert a substantial influence on the regional climate and marine ecosystems along the western Australia (WA) coast (Tozuka et al, 2014; Kataoka et al, 2018; Zhang et al, 2018)
We investigated the interannual variability of Ningaloo Niño-related rainfall anomalies off the western and northwestern coasts of Australia as well as the associated dynamic mechanisms
During Ningaloo Niño events, the most pronounced rainfall enhancement occurs off the northwestern Australia (NWA) coast

Summary

INTRODUCTION

Ningaloo Niño/Niña is the dominant mode of interannual variation in the southeastern Indian Ocean (Feng et al, 2013; Kataoka et al, 2014; Tozuka et al, 2014; Zhang et al, 2018). The most remarkable Ningaloo Niño-related precipitation anomalies are observed over the northwest Australia (NWA) coastal region near the vicinity of the Intertropical Convergence Zone rather than over the warmest SSTA region near the WA coast (Tozuka et al, 2014, in their Figure 7; Marshall et al, 2015, in their Figure 3; Doi et al, 2015, in their Figure 5) Such precipitation anomalies cannot be explained by the warming of the local SSTAs. In addition, the abnormal rainfall and associated cloud formation play essential roles in the local SSTA change; the cause of the abnormal rainfall over the SEIO is critical for understanding the overall perspective of Ningaloo Niño events. Clouds with cloud top pressures lower than 680 hPa (higher than 440 hPa) are classified as low (high) clouds, and clouds with cloud top pressures between 680 and 440 hPa are defined as middle clouds

Methodology

CONCLUSION AND DISCUSSION

Findings

DATA AVAILABILITY STATEMENT