scholarly journals Characterizing ENSO Coupled Variability and Its Impact on North American Seasonal Precipitation and Temperature*

2015 ◽  
Vol 28 (10) ◽  
pp. 4231-4245 ◽  
Author(s):  
Michelle L. L’Heureux ◽  
Michael K. Tippett ◽  
Anthony G. Barnston
Keyword(s):  
North American ◽  
Longwave Radiation ◽  
Climate Impacts ◽  
Spring Precipitation ◽  
Central Pacific ◽  
Complete Representation ◽  
Central Pacific Ocean ◽  
Temperature And Precipitation ◽  
Precipitation Anomalies ◽  
Coupled Variability

Abstract Two questions are addressed in this paper: whether ENSO can be adequately characterized by simple, seasonally invariant indices and whether the time series of a single component—SST or OLR—provides a sufficiently complete representation of ENSO for the purpose of quantifying U.S. climate impacts. Here, ENSO is defined as the leading mode of seasonally varying canonical correlation analysis (CCA) between anomalies of tropical Pacific SST and outgoing longwave radiation (OLR). The CCA reveals that the strongest regions of coupling are mostly invariant as a function of season and correspond to an OLR region located in the central Pacific Ocean (CP-OLR) and an SST region in the eastern Pacific that coincides with the Niño-3 region. In a linear context, the authors explore whether the use of a combined index of these SST and OLR regions explains additional variance of North American temperature and precipitation anomalies beyond that described by using a single index alone. Certain seasons and regions benefit from the use of a combined index. In particular, a combined index describes more variability in winter/spring precipitation and summer temperature.

scholarly journals Flow-dependent and dynamical systems analyses of predictability of the Pacific-North American summertime circulation

2021 ◽  
Author(s):  
Ebrahim Nabizadeh ◽  
Sandro Lubis ◽  
Pedram Hassanzadeh
Keyword(s):  
Dynamical Systems ◽  
North American ◽  
Initial Conditions ◽  
Weather Prediction ◽  
Self Organizing Map ◽  
Near Surface ◽  
Pacific North American ◽  
The North ◽  
Temperature And Precipitation ◽  
Precipitation Anomalies

Forecast skills of numerical weather prediction (NWP) models and intrinsic predictability can be flow-dependent, e.g., different amongweather regimes. Here, we have examined the predictability of distinct Pacific-North American weather regimes in June-September. Fourweather regimes are identified using a self-organizing map analysis of daily 500-hPa geopotential height anomalies, and are shown to havedistinct and coherent links to near-surface temperature and precipitation anomalies over the North American continent. The 4 to 14-dayforecast skills of these 4 regimes are quantified for the ECMWF and the NCEP models (from the TIGGE project) and the Global EnsembleForecast System (GEFS). Based on anomaly correlation coefficient, persistence, and transition frequency, the highest forecast skills areconsistently found for regime 3 (Arctic high). In general, the least skillful forecasts are for regime 1 (Pacific trough). The instantaneous localdimension and persistence of each regime are computed using a dynamical systems-based analysis. The local dimension and persistenceare indicators of intrinsic predictability. This analysis robustly shows that regime 3 has the highest intrinsic predictability. The analysisalso suggests that overall, regime 1 has the lowest intrinsic predictability. These findings are consistent with the high (low) forecast skillsof NWP models for regime 3 (regime 1). Weather regime 1 is associated with above-normal temperature and precipitation anomalies overwestern North America and around the Gulf of Mexico region, indicating potentially important implications for the poor predictability ofthis regime. The dynamical systems analysis suggests that better estimates of initial conditions might improve the forecasts of this regime.

scholarly journals Mechanisms determining diversity of ENSO-driven equatorial precipitation anomalies

2021 ◽  
pp. 1-47
Keyword(s):  
El Niño ◽  
El Nino ◽  
Longwave Radiation ◽  
Walker Circulation ◽  
Precipitation Anomaly ◽  
La Niña ◽  
Central Pacific ◽  
Cp El Niño ◽  
La Nina ◽  
Precipitation Anomalies

Abstract The longitudinal location of precipitation anomalies over the equatorial Pacific shows a distinctive feature with the westernmost location for La Niña, the easternmost location for eastern-Pacific (EP) El Niño and somewhere between for central-Pacific (CP) El Niño, even though the center of the sea surface temperature anomaly (SSTA) for La Niña is located slightly east of that of CP El Niño. The mechanisms for such a precipitation diversity were investigated through idealized model simulations and moisture and moist static energy budget analyses. It is revealed that the boundary layer convergence anomalies associated with the precipitation diversity are mainly induced by underlying SSTA through the Lindzen-Nigam mechanism, that is, their longitudinal locations are mainly controlled by the meridional and zonal distributions of the ENSO SSTA. The westward shift of the precipitation anomaly center during La Niña relative to that during CP El Niño is primarily caused by the combined effects of nonlinear zonal moist enthalpy advection anomalies and the Lindzen-Nigam mechanism mentioned above. Such a zonal diversity is further enhanced by the “convection-cloud-longwave radiation” feedback, the SST-induced latent heat flux anomalies and the advection of mean moist enthalpy by anomalous winds. This diversity in the longitudinal location of precipitation anomalies has contributions to the diversities in the longitudinal locations of anomalous Walker Circulation and western North Pacific anomalous anticyclone/cyclone among the three types of ENSO.

scholarly journals Application of an ice sheet model to evaluate PMIP3 LGM climatologies over the North American ice sheets

2017 ◽  
Author(s):  
Jay R. Alder ◽  
Steve W. Hostetler
Keyword(s):  
North American ◽  
General Circulation ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Longwave Radiation ◽  
General Circulation Models ◽  
The North ◽  
Temperature And Precipitation ◽  
Simulated Surface

Abstract. We apply the Community Ice Sheet Model (CISM2) to the Palaeoclimate Modelling Intercomparison 3 (PMIP3) Last Glacial Maximum (LGM) simulations to determine if the general circulation models (GCMs) simulated surface temperature and precipitation climatologies would support the large North American ice sheets. We force CISM2 with eight PMIP3 GCMs, and an additional model, GENMOM. The ice sheet simulations indicate seven GCMs produce LGM temperature and precipitation climatologies that support positive mass balances of the Laurentide and Cordilleran ice sheets (LIS, CIS) in areas corresponding to those prescribed in the GCMs, and two GCMs simulate July temperatures that are too warm to support the ice sheets. Four of the nine GCMs support the development of ice sheets in Beringia in the CISM2, in conflict with the driving GCM and reconstructions that indicate the area was ice-free. We test the sensitivity of our results over a range of snow and ice positive degree-day factors, and we evaluate the role of albedo, and shortwave and longwave radiation in the simulations. Areas with perineal snow in the GCM simulations are found to correspond well to the CISM2 simulation of ice presence.

scholarly journals Primary Production in the Water Column as Major Structuring Element of the Biogeographical Distribution and Function of Archaea in Deep-Sea Sediments of the Central Pacific Ocean

Archaea ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Franziska Wemheuer ◽  
Avril Jean Elisabeth von Hoyningen-Huene ◽  
Marion Pohlner ◽  
Julius Degenhardt ◽  
Bert Engelen ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Primary Production ◽  
Deep Sea ◽  
Archaeal Community ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Deep Sea Sediments ◽  
And Function ◽  
Functional Profiles ◽  
Archaeal Communities

Information on environmental conditions shaping archaeal communities thriving at the seafloor of the central Pacific Ocean is limited. The present study was conducted to investigate the diversity, composition, and function of both entire and potentially active archaeal communities within Pacific deep-sea sediments. For this purpose, sediment samples were taken along the 180° meridian of the central Pacific Ocean. Community composition and diversity were assessed by Illumina tag sequencing targeting archaeal 16S rRNA genes and transcripts. Archaeal communities were dominated by CandidatusNitrosopumilus(Thaumarchaeota) and other members of theNitrosopumilaceae(Thaumarchaeota), but higher relative abundances of the Marine Group II (Euryarchaeota) were observed in the active compared to the entire archaeal community. The composition of the entire and the active archaeal communities was strongly linked to primary production (chlorophyll content), explaining more than 40% of the variance. Furthermore, we found a strong correlation of the entire archaeal community composition to latitude and silicic acid content, while the active community was significantly correlated with primary production and ferric oxide content. We predicted functional profiles from 16S rRNA data to assess archaeal community functions. Latitude was significantly correlated with functional profiles of the entire community, whereas those of the active community were significantly correlated with nitrate and chlorophyll content. The results of the present study provide first insights into benthic archaeal communities in the Pacific Ocean and environmental conditions shaping their diversity, distribution, and function. Additionally, they might serve as a template for further studies investigating archaea colonizing deep-sea sediments.

The Birds of Fanning Island, Central Pacific Ocean

The Condor ◽  
1925 ◽  
Vol 27 (5) ◽  
pp. 185-196 ◽  
Author(s):  
Harold Kirby,
Keyword(s):  
Pacific Ocean ◽  
Central Pacific ◽  
Central Pacific Ocean

The Life Cycle and Variability of Antarctic Weak Polar Vortex Events

2022 ◽  
pp. 1-63
Keyword(s):  
Life Cycle ◽  
Polar Vortex ◽  
Southern Annular Mode ◽  
Austral Spring ◽  
Stratospheric Polar Vortex ◽  
Temperature And Precipitation ◽  
Scale Temperature ◽  
Precipitation Anomalies ◽  
Polar Stratosphere ◽  
The Antarctic

Abstract Motivated by the strong Antarctic sudden stratospheric warming (SSW) in 2019, a survey on the similar Antarctic weak polar events (WPV) is presented, including their life cycle, dynamics, seasonality, and climatic impacts. The Antarctic WPVs have a frequency of about four events per decade, with the 2002 event being the only major SSW. They show a similar life cycle to the SSWs in the Northern Hemisphere but have a longer duration. They are primarily driven by enhanced upward-propagating wavenumber 1 in the presence of a preconditioned polar stratosphere, i.e., a weaker and more contracted Antarctic stratospheric polar vortex. Antarctic WPVs occur mainly in the austral spring. Their early occurrence is preceded by an easterly anomaly in the middle and upper equatorial stratosphere besides the preconditioned polar stratosphere. The Antarctic WPVs increase the ozone concentration in the polar region and are associated with an advanced seasonal transition of the stratospheric polar vortex by about one week. Their frequency doubles after 2000 and is closely related to the advanced Antarctic stratospheric final warming in recent decades. The WPV-resultant negative phase of the southern annular mode descends to the troposphere and persists for about three months, leading to persistent hemispheric scale temperature and precipitation anomalies.

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