scholarly journals AMO- and ENSO-Driven Summertime Circulation and Precipitation Variations in North America

2012 ◽  
Vol 25 (19) ◽  
pp. 6477-6495 ◽  
Author(s):  
Qi Hu ◽  
Song Feng
Keyword(s):  
North America ◽  
Atmospheric Circulation ◽  
Time Scale ◽  
Southern Oscillation ◽  
Precipitation Anomaly ◽  
Enso Cycle ◽  
Interannual Variations ◽  
Recent Climate ◽  
Precipitation Anomalies ◽  
Forced Waves

Abstract Interannual and multidecadal time-scale anomalies in sea surface temperatures (SST) of the North Atlantic and North Pacific Oceans could result in persistent atmospheric circulation and regional precipitation anomalies for years to decades. Understanding the processes that connect such SST forcings with circulation and precipitation anomalies is thus important for understanding climate variations and for improving predictions at interannual–decadal time scales. This study focuses on the interrelationship between the Atlantic multidecadal oscillation (AMO) and El Niño–Southern Oscillation (ENSO) and their resulting interannual to multidecadal time-scale variations in summertime precipitation in North America. Major results show that the ENSO forcing can strongly modify the atmospheric circulation variations driven by the AMO. Moreover, these modifications differ considerably between the subtropics and the mid- and high-latitude regions. In the subtropics, ENSO-driven variations in precipitation are fairly uniform across longitudes so ENSO effects only add interannual variations to the amplitude of the precipitation anomaly pattern driven by the AMO. In the mid- and high latitudes, ENSO-forced waves in the atmosphere strongly modify the circulation anomalies driven by the AMO, resulting in distinctive interannual variations following the ENSO cycle. The role of the AMO is shown by an asymmetry in precipitation during ENSO between the warm and cold phases of the AMO. These results extend the outcomes of the studies of the recent Climate Variability and Predictability (CLIVAR) Drought Working Group from the AMO and ENSO effects on droughts to understanding of the mechanisms and causal processes connecting the individual and combined SST forcing of the AMO and ENSO with the interannual and multidecadal variations in summertime precipitation and droughts in North America.

scholarly journals An Extreme Annual Precipitation Anomaly in the Preradiosonde Era

2016 ◽  
Vol 97 (6) ◽  
pp. 989-1001
Author(s):  
David S. Gutzler ◽  
Sharon M. Sullivan ◽  
Deirdre M. Kann
Keyword(s):  
Southern Oscillation ◽  
Climatic Variability ◽  
Historical Record ◽  
Precipitation Anomaly ◽  
Quality Of Data ◽  
Climate Anomalies ◽  
The Pacific ◽  
Average Precipitation ◽  
Modern Analysis ◽  
Precipitation Anomalies

Abstract The wettest year, by a huge margin, in the instrumental history for the state of New Mexico was 1941. The authors describe the extraordinary magnitude and persistence of above-average precipitation across the seasonal cycle during this year and consider possible climatic causes of this exceptional annual anomaly through examination of a wide variety of historical records and modern analysis tools. Indices of the Pacific decadal oscillation and the El Niño–Southern Oscillation were both extremely positive in 1941, consistent with the historical tendency for above-average precipitation across the southern United States under such conditions. However, the largest precipitation anomalies occurred in transition season months that do not fit the typical seasonality associated with strong ENSO- or PDO-related continental climate anomalies in the more recent historical record. The difficulty in attributing this extreme annual anomaly to any specific climatic cause is a reminder that the radiosonde era provides only a limited sample of natural climatic variability. The number and quality of data sources available for preradiosonde years allows for surprisingly in-depth observational analysis of early twentieth-century climatic anomalies.

scholarly journals A Hybrid Precipitation Index Inspired by the SPI, PDSI, and MCDI. Part II: Application to Investigate Precipitation Variability along the West Coast of North America

2020 ◽  
Vol 21 (9) ◽  
pp. 1977-2002 ◽  
Author(s):  
Dudley B. Chelton ◽  
Craig M. Risien
Keyword(s):  
British Columbia ◽  
North America ◽  
Time Scales ◽  
West Coast ◽  
Time Scale ◽  
Opposite Sign ◽  
Precipitation Variability ◽  
The West ◽  
Southeast Alaska ◽  
Precipitation Anomalies

AbstractThe hybrid precipitation index developed in Part I of this study is applied to investigate precipitation variability along the west coast of North America during the wet season November–March on monthly-to-interannual time scales. The variability in each of six regions considered in this study is negatively correlated with nearby 500-hPa geopotential height anomalies. Except in Southeast Alaska, these correlation patterns indicate that precipitation variability in each region is predominantly influenced by local atmospheric forcing analogous to the ridging of the westerly flow that has been studied extensively with regard to California drought variability. The first empirical orthogonal function (EOF) accounts for nearly all of the Southeast Alaska precipitation variability, which is controlled by the strength of the onshore flow rather than ridging. In association with this mode of variability, precipitation anomalies of opposite sign account for about 40% of the precipitation variance in Northern California and Oregon on all time scales. On short time scales, the second and third EOFs account primarily for precipitation variability in British Columbia/Washington and California, respectively. With increasing time scale, the third EOF diminishes in importance and the second EOF evolves into a pattern of synchronous precipitation anomalies of the same sign from British Columbia to Northern California. Precipitation variability in Southern California is only modestly related to precipitation elsewhere. With increasing time scale, Southern California precipitation variability becomes increasingly related to precipitation anomalies of opposite sign in Washington.

scholarly journals Interannual variations and regionality of Antarctic sea-ice-temperature associations

1998 ◽  
Vol 27 ◽  
pp. 403-408 ◽  
Author(s):  
Andrew M. Carleton ◽  
Gareth John ◽  
Robert Welsch
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Ross Sea ◽  
Southern Oscillation ◽  
Interannual Variations ◽  
Antarctic Sea Ice ◽  
Ice Conditions ◽  
Climate Scale ◽  
The Relationship

In the Antarctic, climate-scale anomalies of surface temperature (T s) are associated with the atmospheric circulation and also sea-ice conditions. Negative (positive) anomalies of station T s tend to accompany more (less) extensive sea ice in broadly similar longitudes. However, the relationship between temperature and sea-ice conditions during large interannual variations of the circulation has been little explored, as has its association over longer distances within Antarctica. This study examines the inter-associations between T s at seven automatic weather stations in East Antarctica and the Ross Sea area, and sea-ice conditions in the sector 30° Ε eastward to 60° W for the three ice-growth seasons (March-October) of 1987-89. Strong between-year differences occur in the intercorrelalions among station T s, sectoral içe extent and the relationship between the two climate variables, especially for 1988 and 1989. These differences are also expressed in the patterns of cold-air mesoscale cyclogenesis over sub-Antarctic latitudes. The study indicates that the T s-sea-ice link is modulated strongly in the presence of large-scale interannual anomalies of the atmospheric circulation, including the El Niño-Southern Oscillation (ENSO).

Interannual Variability of North American Winter Temperature Extremes and Its Associated Circulation Anomalies in Observations and CMIP5 Simulations

2020 ◽  
Vol 33 (3) ◽  
pp. 847-865 ◽  
Author(s):  
B. Yu ◽  
H. Lin ◽  
V. V. Kharin ◽  
X. L. Wang
Keyword(s):  
North America ◽  
Surface Temperature ◽  
Atmospheric Circulation ◽  
North American ◽  
North Pacific ◽  
Large Scale ◽  
Temperature Extremes ◽  
Temperature Extreme ◽  
Central Canada ◽  
Leading Mode

AbstractThe interannual variability of wintertime North American surface temperature extremes and its generation and maintenance are analyzed in this study. The leading mode of the temperature extreme anomalies, revealed by empirical orthogonal function (EOF) analyses of December–February mean temperature extreme indices over North America, is characterized by an anomalous center of action over western-central Canada. In association with the leading mode of temperature extreme variability, the large-scale atmospheric circulation features an anomalous Pacific–North American (PNA)-like pattern from the preceding fall to winter, which has important implications for seasonal prediction of North American temperature extremes. A positive PNA pattern leads to more warm and fewer cold extremes over western-central Canada. The anomalous circulation over the PNA sector drives thermal advection that contributes to temperature anomalies over North America, as well as a Pacific decadal oscillation (PDO)-like sea surface temperature (SST) anomaly pattern in the midlatitude North Pacific. The PNA-like circulation anomaly tends to be supported by SST warming in the tropical central-eastern Pacific and a positive synoptic-scale eddy vorticity forcing feedback on the large-scale circulation over the PNA sector. The leading extreme mode–associated atmospheric circulation patterns obtained from the observational and reanalysis data, together with the anomalous SST and synoptic eddy activities, are reasonably well simulated in most CMIP5 models and in the multimodel mean. For most models considered, the simulated patterns of atmospheric circulation, SST, and synoptic eddy activities have lower spatial variances than the corresponding observational and reanalysis patterns over the PNA sector, especially over the North Pacific.

scholarly journals Origins of Biases in CMIP5 Models Simulating Northwest Pacific Summertime Atmospheric Circulation Anomalies during the Decaying Phase of ENSO

2018 ◽  
Vol 31 (14) ◽  
pp. 5707-5729 ◽  
Author(s):  
Weichen Tao ◽  
Gang Huang ◽  
Renguang Wu ◽  
Kaiming Hu ◽  
Pengfei Wang ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Southern Oscillation ◽  
Coupled Model ◽  
Tropical Indian Ocean ◽  
Shortwave Radiation ◽  
Cmip5 Models ◽  
Northwest Pacific ◽  
Circulation Anomalies ◽  
Atmospheric Circulation Anomalies ◽  
Sst Anomalies

Abstract The present study documents the biases of summertime northwest Pacific (NWP) atmospheric circulation anomalies during the decaying phase of ENSO and investigates their plausible reasons in 32 models from phase 5 of the Coupled Model Intercomparison Project. Based on an intermodel empirical orthogonal function (EOF) analysis of El Niño–Southern Oscillation (ENSO)-related 850-hPa wind anomalies, the dominant modes of biases are extracted. The first EOF mode, explaining 21.3% of total intermodel variance, is characterized by a cyclone over the NWP, indicating a weaker NWP anticyclone. The cyclone appears to be a Rossby wave response to unrealistic equatorial western Pacific (WP) sea surface temperature (SST) anomalies related to excessive equatorial Pacific cold tongue in the models. On one hand, the cold SST biases increase the mean zonal SST gradient, which further intensifies warm zonal advection, favoring the development and persistence of equatorial WP SST anomalies. On the other hand, they reduce the anomalous convection caused by ENSO-related warming, and the resultant increase in downward shortwave radiation contributes to the SST anomalies there. The second EOF mode, explaining 18.6% of total intermodel variance, features an anticyclone over the NWP with location shifted northward. The related SST anomalies in the Indo-Pacific sector show a tripole structure, with warming in the tropical Indian Ocean and equatorial central and eastern Pacific and cooling in the NWP. The Indo-Pacific SST anomalies are highly controlled by ENSO amplitude, which is determined by the intensity of subtropical cells via the adjustment of meridional and vertical advection in the models.

Potential predictability of Southwest US rainfall : role of tropical and high-latitude variability

2021 ◽  
pp. 1-45
Keyword(s):  
Time Scale ◽  
Climate Model ◽  
Southern Oscillation ◽  
Seasonal Prediction ◽  
Seasonal Rainfall ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Potential Predictability ◽  
Subseasonal Variability ◽  
The Tropics

Abstract This study explores the potential predictability of Southwest US (SWUS) precipitation for the November-March season in a set of numerical experiments performed with the Whole Atmospheric Community Climate Model. In addition to the prescription of observed sea surface temperature and sea ice concentration, observed variability from the MERRA-2 reanalysis is prescribed in the tropics and/or the Arctic through nudging of wind and temperature. These experiments reveal how a perfect prediction of tropical and/or Arctic variability in the model would impact the prediction of seasonal rainfall over the SWUS, at various time scales. Imposing tropical variability improves the representation of the observed North Pacific atmospheric circulation, and the associated SWUS seasonal precipitation. This is also the case at the subseasonal time scale due to the inclusion of the Madden-Julian Oscillation (MJO) in the model. When additional nudging is applied in the Arctic, the model skill improves even further, suggesting that improving seasonal predictions in high latitudes may also benefit prediction of SWUS precipitation. An interesting finding of our study is that subseasonal variability represents a source of noise (i.e., limited predictability) for the seasonal time scale. This is because when prescribed in the model, subseasonal variability, mostly the MJO, weakens the El Niño Southern Oscillation (ENSO) teleconnection with SWUS precipitation. Such knowledge may benefit S2S and seasonal prediction as it shows that depending on the amount of subseasonal activity in the tropics on a given year, better skill may be achieved in predicting subseasonal rather than seasonal rainfall anomalies, and conversely.

Future Changes to El Niño Teleconnections over the North Pacific and North America

2021 ◽  
pp. 1-43
Author(s):  
Jonathan D. Beverley ◽  
Matthew Collins ◽  
F. Hugo Lambert ◽  
Robin Chadwick
Keyword(s):  
North America ◽  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Positive Temperature ◽  
Central Pacific ◽  
Wave Source ◽  
The North ◽  
Precipitation Anomalies ◽  
The North Pacific

AbstractThe El Niño-Southern Oscillation (ENSO) is the leading mode of interannual climate variability and it exerts a strong influence on many remote regions of the world, for example in northern North America. Here, we examine future changes to the positive-phase ENSO teleconnection to the North Pacific/North America sector and investigate the mechanisms involved. We find that the positive temperature anomalies over Alaska and northern North America that are associated with an El Niño event in the present day are much weaker, or of the opposite sign, in the CMIP6 abrupt 4×CO2 experiments for almost all models (22 out of 26, of which 15 are statistically significant differences). This is largely related to changes to the anomalous circulation over the North Pacific, rather than differences in the equator-to-pole temperature gradient. Using a barotropic model, run with different background circulation basic states and Rossby wave source forcing patterns from the individual CMIP6 models, we find that changes to the forcing from the equatorial central Pacific precipitation anomalies are more important than changes in the global basic state background circulation. By further decomposing this forcing change into changes associated with the longitude and magnitude of ENSO precipitation anomalies, we demonstrate that the projected overall eastward shift of ENSO precipitation is the main driver of the temperature teleconnection change, rather than the increase in magnitude of El Niño precipitation anomalies which are, nevertheless, seen in the majority of models.

Anomalies of continental precipitation associated with El Niño Southern Oscillation: the role of moisture contribution from oceanic and terrestrial sources 

2021 ◽  
Author(s):  
Rogert Sorí ◽  
Raquel Nieto ◽  
Margarida L.R. Liberato ◽  
Luis Gimeno
Keyword(s):  
South America ◽  
Southern Oscillation ◽  
The United States ◽  
Precipitation Pattern ◽  
Two Phase ◽  
The North ◽  
Terrestrial Origin ◽  
Precipitation Anomalies ◽  
June July

<p>The regional and global precipitation pattern is highly modulated by the influence of El Niño Southern Oscillation (ENSO), which is considered the most important mode of climate variability on the planet. In this study was investigated the asymmetry of the continental precipitation anomalies during El Niño and La Niña. To do it, a Lagrangian approach already validated was used to determine the proportion of the total Lagrangian precipitation that is of oceanic and terrestrial origin. During both, El Niño and La Niña, the Lagrangian precipitation in regions such as the northeast of South America, the east and west coast of North America, Europe, the south of West Africa, Southeast Asia, and Oceania is generally determined by the oceanic component of the precipitation, while that from terrestrial origin provides a major percentage of the average Lagrangian precipitation towards the interior of the continents. The role of the moisture contribution to precipitation from terrestrial and oceanic origin was evaluated in regions with statistically significant precipitation anomalies during El Niño and La Niña. Two-phase asymmetric behavior of the precipitation was found in regions such the northeast of South America, South Africa, the north of Mexico, and southeast of the United States, etc. principally for December-January-February and June-July-August. For some of these regions was also calculated the anomalies of the precipitation from other datasets to confirm the changes. Besides, for these regions was calculated the anomaly of the Lagrangian precipitation, which agrees in all the cases with the precipitation change. For these regions, it was determined which component of the Lagrangian precipitation, whether oceanic or terrestrial, controlled the precipitation anomalies. A schematic figure represents the extent of the most important seasonal oceanic and terrestrial sources for each subregion during El Niño and La Niña.</p>

scholarly journals Advanced error diagnostics of the CMAQ and Chimere modelling systems within the AQMEII3 model evaluation framework

2017 ◽  
Author(s):  
Efisio Solazzo ◽  
Christian Hogrefe ◽  
Augustin Colette ◽  
Marta Garcia-Vivanco ◽  
Stefano Galmarini
Keyword(s):  
Wind Speed ◽  
North America ◽  
Boundary Conditions ◽  
Time Scale ◽  
Model Evaluation ◽  
Evaluation Framework ◽  
Diagnostic Methods ◽  
Base Case ◽  
Lateral Boundary ◽  
Lateral Boundary Conditions

Abstract. The work here complements the overview analysis of the modelling systems participating in the third phase of the Air Quality Model Evaluation International Initiative (AQMEII3) by focusing on the performance for hourly surface ozone by two modelling systems, Chimere for Europe and CMAQ for North America. The evaluation strategy outlined in the course of the three phases of the AQMEII activity, aimed to build up a diagnostic methodology for model evaluation, is pursued here and novel diagnostic methods are proposed. In addition to evaluating the base case simulation in which all model components are configured in their standard mode, the analysis also makes use of sensitivity simulations in which the models have been applied by altering and/or zeroing lateral boundary conditions, emissions of anthropogenic precursors, and ozone dry deposition. To help understand of the causes of model deficiencies, the error components (bias, variance, and covariance) of the base case and of the sensitivity runs are analysed in conjunction with time-scale considerations and error modelling using the available error fields of temperature, wind speed, and NOx concentration. The results reveal the effectiveness and diagnostic power of the methods devised (which remains the main scope of this study), allowing the detection of the time scale and the fields that the two models are most sensitive to. The representation of planetary boundary layers (PBL) dynamics is pivotal to both models. In particular: i) The fluctuations slower than −1.5 days account for 70–85 % of the total ozone quadratic error; ii) A recursive, systematic error with daily periodicity is detected, responsible for 10–20 % of the quadratic total error; iii) Errors in representing the timing of the daily transition between stability regimes in the PBL are responsible for a covariance error as large as 9 ppb (as much as the standard deviation of the network-average ozone observations in summer in both Europe and North America); iv) The CMAQ ozone error has a weak/negligible dependence on the errors in NO2 and wind speed, while the error in NO2 significantly impacts the ozone error produced by Chimere; v) On a continent wide monitoring network-average, a zeroing out of anthropogenic emissions produces an error increase of 45 % (25 %) during summer and of 56 % (null) during winter for Chimere (CMAQ), while a zeroing out of lateral boundary conditions results in an ozone error increase of 30 % during summer and of 180 % during winter (CMAQ).

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