The impact of atmospheric rivers on rainfall in New Zealand

Abstract

This study quantifies the impact of atmospheric rivers (ARs) on rainfall in New Zealand. Using an automated AR detection algorithm, daily rainfall records from 654 rain gauges, and various atmospheric reanalysis datasets, we investigate the climatology of ARs, the characteristics of landfalling ARs, the contribution of ARs to annual and seasonal rainfall totals, and extreme rainfall events between 1979 and 2018 across the country. Results indicate that these filamentary synoptic features play an essential role in regional water resources and are responsible for many extreme rainfall events on the western side of mountainous areas and northern New Zealand. In these regions, depending on the season, 40–86% of the rainfall totals and 50–98% of extreme rainfall events are shown to be associated with ARs, with the largest contributions predominantly occurring during the austral summer. Furthermore, the median daily rainfall associated with ARs is 2–3 times than that associated with other storms. The results of this study extend the knowledge on the critical roles of ARs on hydrology and highlight the need for further investigation on the landfalling AR physical processes in relation to global circulation features and AR sources, and hydrological hazards caused by ARs in New Zealand.

Extreme Compound and Seesaw Hydrometeorological Events in New Zealand: An Initial Assessment

“…The rapid transition from dry to wet during seesaw events implies substantial and/or persistent precipitation events. In New Zealand, Reid et al (2021) identified that eight (Christchurch and New Plymouth) and nine (Dunedin) of the top ten rainfall events were associated with an atmospheric river; narrow bands of intense water vapour transport (Newell et al, 1992) that have becoming increasingly associated with extreme precipitation and flooding across New Zealand (Prince et al, 2021;Shu et al, 2021). These same sites (Christchurch, New Plymouth and Dunedin) simultaneously reveal high occurrence of seesaw events in the present work (Fig.…”

Characteristics and large‐scale drivers of atmospheric rivers associated with extreme floods in New Zealand

“…Although their importance diminishes away from the west coast and topographic forcing associated with the Southern Alps, ARs were shown to remain critical to precipitation climatology across a series of locations around New Zealand. In subsequent studies, both Reid et al (2021) and Shu et al (2021) have found a similarly dominant role of ARs for extreme precipitation events across New Zealand. Furthermore, these broad characteristics of New Zealand AR climatology are reflected in more geographically focussed studies within New Zealand, and from precipitation to river flows and the cryosphere.…”

“…(2021) and Shu et al . (2021) have found a similarly dominant role of ARs for extreme precipitation events across New Zealand. Furthermore, these broad characteristics of New Zealand AR climatology are reflected in more geographically focussed studies within New Zealand, and from precipitation to river flows and the cryosphere.…”

Precipitation and temperature anomalies over Aotearoa New Zealand analysed by weather types and descriptors of atmospheric centres of action

“…Generally, 15–35% of the extremes are associated with the dominant WTs identified in Figure 15b. This could be due to interferences with other rain‐bearing systems or mechanisms not necessarily discriminated by the WTs, like atmospheric rivers (recently shown to be involved in many major rain events in ANZ: Prince et al ., 2021; Reid et al ., 2021; Shu et al ., 2021), or ex‐tropical cyclones (Lorrey et al ., 2014b). Three main regions show slightly larger values, denoting a stronger relationship between WTs and intense or precipitation extremes: (a) the Fiordland region, southwest of the South Island; (b) the northern part of the Southern Alps in the South Island; (c) the central‐western part of the North Island, around the volcanic peak of Mount Ruapehu.…”