Nine atmospheric rivers since late Dec: what ever became of ENSO?
I predict imminent serious flooding of preprint servers with articles offering up explanations for (yet another) very wet La Nina in California.
Checking today, GoogScholar had 493 results for 'enso california' limited to 2023. However most of these were written six months or more ago and are just now surfacing at journals. Here we are looking only for post-Jan 15th articles taking recent events into consideration.
Under these circumstances, the best way to stay on top of developments is probably the WeatherWest twitter site of Daniel Swain which effectively relays the best insider sources.
https://twitter.com/weather_west?lang=en√ Clouds can go higher and drift further
Could indeed be involved but 'when we try to pick out anything by itself, we find it hitched to everything else in the universe'.
Low Cloud–SST Feedback over the Subtropical Northeast Pacific and the Remote Effect on ENSO Variability
Liu Yang et al 22 Dec 2022
https://journals.ametsoc.org/view/journals/clim/36/2/JCLI-D-21-0902.1.xmlLow clouds frequent the subtropical northeastern Pacific Ocean (NEP) and interact with the local sea surface temperature (SST) to form positive feedback. Wind fluctuations drive SST variability through wind–evaporation–SST (WES) feedback, and surface evaporation also acts to damp SST.
Over the summer NEP, the low cloud–SST feedback is so large that it exceeds the evaporative damping and amplifies summertime SST variations. The WES feedback causes the locally enhanced SST variability to propagate southwestward from the NEP low cloud deck, modulating El Niño–Southern Oscillation (ENSO) occurrence upon reaching the equator. As a result, a second-year La Niña tends to occur when there are significant cold SST anomalies over the subtropical NEP in summer following an antecedent La Niña event ...
√ It's those darned fluctuations of AO, MJO, ENSO and PNATP
On the Relationship of Arctic Oscillation with Atmospheric Rivers and Snowpack in the Western US
Samuel Liner et al 02 August 2022
https://www.mdpi.com/2073-4441/14/15/2392 More precipitation is observed in lower latitudes during negative AO months and farther north (north of 45° N) in latitude during positive AO months. These are associated with wavelike synoptic patterns in negative AO months and more straight-line type synoptic patterns in positive AO months.
There is no statistically significant difference between either negative AO or positive AO phase, especially in southern California. In addition, the snow water equivalent tends to be reduced in the positive AO phase and under high-temperature conditions, especially in recent years (2010s). The similar relationships are found in the early 1990s and 2000s, but their statistical significances are low.
Atmospheric rivers are characterized by the filamentary shape of strong water vapor transport associated with extratropical cyclones and proceeded by a low-level jet stream, categorized by an IVT greater than ~250 kg/m/s and high integrated water vapor >2 cm. Although ARs only cover about ten percent of the globe longitudinally, they transport up to ninety percent of poleward water vapor.
ARs contribute up to fifty percent of the state’s annual precipitation and streamflow. An increased number of ARs can also influence the snowpack. Rain-on-snow events and AR events occurring in different locations can have opposing effects on snowpack.
The actual contribution of ARs to the rain and snowpack in California depends on where they make landfall. Since water vapor transported in ARs is lower in the atmosphere (under ~700 hPa), it is especially subject to orographic lifting. The type of terrain influences how much water vapor falls as precipitation and how far inland the AR’s influence reaches; the number of ARs reaching the interior is highest in the Pacific Northwest while fewer ARs make it over the High Sierra Nevada mountains and into the Great Basin.
Although ARs are largely governed by the regional moisture flux and meteorological conditions, they are also controlled by large-scale climate variability with different temporal scales. The climate variability, such as El Niño-Southern Oscillation (ENSO), Arctic Oscillation (AO), Madden-Julian Oscillation (MJO), and Pacific/North American Teleconnection Pattern (PNA) frequently fluctuate demonstrating possible linkages to ARs.
√ The climate varies a lot but periodically locks in
Temporal and geographic extent of the late Holocene dry period in the central Great Basin
Scott Mensing et al
https://www.sciencedirect.com/science/article/abs/pii/S0277379122005315We provide evidence from pollen and radiocarbon dating of wet meadow sediments for the presence of multi-centennial drought, termed the Late Holocene Dry Period (LHDP), in the central Great Basin between 3100 and 1800 cal yr BP. We examine four sites spanning the boundary of the anti-phasing dipole pattern of precipitation associated with ENSO.
The LHDP conforms to the dipole pattern but contains three different phases, an initial 900-year dry period, followed by 200 years of wetter climate and then another 200 years of extreme drought. The dipole boundary appears to have shifted to a new semi-stable position with each period.
A review of lake levels, tree-rings, and submerged stumps suggest that the drought between 2000 and 1800 cal yr BP was of greater magnitude than that recorded during the MCA megadrought.
We do not yet have sufficient information to establish a cause for megadroughts, however it is important to note that the climate system periodically locks into a pattern with a consistently northward shifted storm track that persists for multiple decades to centuries, bringing persistent drought to the American Southwest.
√ asking a scientist for an opinion gets something hedged to the point of uselessness
Bruce S posts: 'Not climate change. And not El Niño either. But it feels like one though the Walker circulation hasn’t switched so not really El Niño.The jet stream is pointed straight at us in ways that look exactly how an El Niño would act. Just because 1969, 1982-83, and 1997-98 were El Niño and super wet means nothing. It is the way the jet steam has dropped in latitude so that California rather than the Pacific Northwest is getting the storms and rainfall.'
