Happy New Year 2024 (and sorry for the forum being offline some hours) /DM
70&10mb winds almost a carbon copy of 2015 when viewed through earth.nullschool.net.
Ed Vallee: Real-time ENSO water temp analysis showing first official #LaNina reading in the 3.4 region today. Must watch trends
I don't understand what happened in the last leg of observations of the NINO4 SST. The observation blue dotted lines have red dotted lines below it. Does this means that the observations took a higher path that prior projections?
The biggest risk factor to the validity of the p.d.f. is the risk that the ENSO SSTs in future years will be biased warm or cold relative to the calibration period for reasons that are missing from the models, or that one or more of the models suffers from some error or mistake that will result in future forecasts being biased relative to model performance in the calibration period.
QuoteEd Vallee: Real-time ENSO water temp analysis showing first official #LaNina reading in the 3.4 region today. Must watch trendshttps://twitter.com/edvalleewx/status/754319838932262913
SST values in the Niño 3.4 region may not be the best choice for determining La Niña episodes but, for consistency, the index has been defined by negative anomalies in this area. A better choice might be the Niño 4 region, since that region normally has SSTs at or above the threshold for deep convection throughout the year. An SST anomaly of -0.5°C in that region would be sufficient to bring water temperatures below the 28°C threshold, which would result in a significant westward shift in the pattern of deep convection in the tropical Pacific.
AbstractThe contrasting behaviour of westward-moving mixed Rossby–gravity (WMRG) and the first Rossby (R1) waves in El Niño (EN) and La Niña (LN) seasons is documented with a focus on the Northern Hemisphere winter. The eastward-moving variance in the upper troposphere is dominated by WMRG and R1 structures that appear to be Doppler-shifted by the flow and are referred to as WMRG-E and R1-E. In the east Pacific and Atlantic the years with stronger equatorial westerly winds, LN in the former and EN in the latter, have the stronger WMRG and WMRG-E. In the east Pacific, R1 is also a maximum in LN. However, R1-E exhibits an eastward shift between LN and EN.The changes with El Niño/Southern Oscillation (ENSO) phase provide a test bed for the understanding of these waves. In the east Pacific and Atlantic, the stronger WMRG-E and WMRG with stronger westerlies are in accord with the dispersion relation with simple Doppler-shifting by the zonal flow. The possible existence of free waves can also explain stronger R1 in EN in the Eastern Hemisphere. 1-D free-wave propagation theory based on wave activity conservation is also important for R1. However, this theory is unable to explain the amplitude maxima for other waves observed in the strong equatorial westerly regions in the Western Hemisphere, and certainly not their ENSO-related variation. The forcing of equatorial waves by higher-latitude wave activity and its variation with ENSO phase is therefore examined. Propagation of extratropical eastward-moving Rossby wave activity through the westerly ducts into the equatorial region where it triggers WMRG-E is favoured in the stronger westerlies, in LN in the east Pacific and EN in the Atlantic. It is also found that WMRG is forced by Southern Hemisphere westward-moving wave trains arching into the equatorial region where they are reflected. The most significant mechanism for both R1 and R1-E appears to be lateral forcing by subtropical wave trains.
The fact that EN events significantly suppress WMRG waves over the central-eastern Pacific in both winter and summer may have an implication for the stratosphere QBO. Maruyama and Tsuneoka (1988) found that EN events had a connection to longer-lasting QBO westerly/shorter-lasting QBO easterly. This is consistent with the finding here considering that the tropospheric WMRG waves, which propagate upwards and contribute to the easterly momentum acceleration, are suppressed in EN years. In addition, given that Kelvin waves contribute to the westerly momentum acceleration, the QBO difference may also be related to the fact that upper-tropospheric Kelvin waves are substantially enhanced by EN events, as shown in Yang and Hoskins (2013). A modelling study of Maury et al. (2013) indeed showed that ENSO has a substantial influence on stratospheric Kelvin waves.
Abstract. Tropical temperature variability over 10–30 km and associated Kelvin wave activity is investigated using GPS radio occultation (RO) data from January 2002 to December 2014. RO data are a powerful tool to quantify tropical temperature oscillations with short vertical wavelengths due to their high vertical resolution and high accuracy and precision. Gridded temperatures from GPS RO show strongest variability in the tropical tropopause region (on average 3 K²). Large-scale zonal variability is dominated by transient high-frequency waves (2 K²) and about half of high-frequency variance is explained by eastward traveling Kelvin waves with periods of 7 to 30 days (1 K²). Quasi-stationary waves associated with the annual cycle and inter-annual variability contribute about a third (1 K²) to total resolved zonal variance. High-frequency waves, including Kelvin waves, are highly transient in time. Above 20 km, Kelvin waves are strongly modulated by the quasi-biennial oscillation (QBO) in stratospheric zonal winds, with enhanced wave activity during the westerly shear phase of the QBO. In the tropical tropopause region, however, peaks of Kelvin wave activity are irregularly distributed in time. Several peaks coincide with maxima of zonal variance in tropospheric deep convection, but other episodes are not evidently related. Further investigations of convective forcing and atmospheric background conditions are needed to better understand variability near the tropopause.
Figure 10. Time series of daily Kelvin wave variance (thin gray) and smoothed Kelvin wave variance (thick black) at 18 km (top panel) and time series of daily variances of high-pass filtered OLR data between 10°S and 10°N (bottom panel). Green and red lines indicate points of time with smoothed Kelvin wave variance outside of one standard deviation (1.59 K², indicated by the dashed yellow line). Green lines indicate matched peaks between Kelvin wave variance and OLR variance, red lines indicate a peak in Kelvin wave variance but a missing peak in OLR variance. Blue lines in the bottom panel indicate a peak in OLR variance but a missing peak in Kelvin wave variance.
QBO, update to #827 above. Sam Lillo keeps updating these graphs via tweets.
The SMOS satellite first acquired sea-surface salinity observations in early 2010 as a weak El Niño was fading out and reversed into a strong La Niña, which lasted until 2012. Lower than usual salinities were observed in early 2010 in the equatorial Pacific as the Western Pacific Fresh Pool extended east. The pool retracted back westward as La Niña settled in.Last year, a strong El Niño developed again. The central Pacific high salinities disappeared and gave way for the Western Pacific Fresh Pool to reach the Eastern Pacific Fresh Pool. This is the greatest El Niño-related salinity anomaly ever measured at the basin scale. “Scientists have shown that low-salinity pools modify the ocean’s vertical structure and change the impact of the atmospheric forcing on it,” said Audrey Hasson, researcher at LOCEAN in Paris, France. “A study combining satellite observations with models is underway to understand the role of salinity in the development of the most recent El Niño event.” Furthermore, scientists have identified the rain-dominated Eastern Pacific Fresh Pool as an ideal place to carry out experiments to better understand the link between sea surface salinity, freshwater fluxes and the oceanic circulation. Scientists have not only used SMOS data to examine the extent of the fresh pool at the surface, but also salinity measurements collected by Argo buoys to estimate the depth of the fresh pool.