scholarly journals Sensitivity of RegCM3 Simulated Precipitation over Southern Brazil with Different Boundary Conditions: ENSO Case

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Simone Erotildes Teleginski Ferraz ◽  
Diego Pedroso
Keyword(s):  
Boundary Conditions ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Regional Climate ◽  
La Niña ◽  
Southern Brazil ◽  
Different Boundary Conditions ◽  
La Nina ◽  
Simulated Precipitation

This paper investigates the capability of a regional climate model (RegCM3) to simulate the Southern Brazil rainfall during three periods: the El Niño (1982), the neutral intermediary phase (1985), and the La Niña (1988). Each integration has used three of different boundary conditions available: NCEP-NCAR Reanalysis (I and II) and ECMWF Reanalysis—ERA-40. The simulations were performed covering a South America domain and some descriptive statistics analyses have been applied, like arithmetic mean, median, standard deviation and Pearson’s correlation; and frequencies histogram over Southern Brazil. The main results show that the model satisfactorily reproduces the rainfall in this region during the El Niño, neutral, and La Niña events, indicating that the boundary conditions which were tested adequately describe this simulations type.

scholarly journals The Pause End and Major Temperature Impacts during Super El Niños are Due to Shortwave Radiation Anomalies

2020 ◽  
pp. 1-20
Author(s):  
Antero Ollila
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
La Niña ◽  
Global Temperature ◽  
Temperature Changes ◽  
Simple Climate Model ◽  
Enso Events ◽  
La Nina ◽  
Temperature Impacts

The hiatus or temperature pause during the 21st century has been the subject of numerous research studies with very different results and proposals. In this study, two simple climate models have been applied to test the causes of global temperature changes. The climate change factors have been shortwave (SW) radiation changes, changes in cloudiness and ENSO (El Niño Southern Oscillation) events assessed as the ONI (Oceanic Niño Index) values and anthropogenic climate drivers. The results show that a simple climate model assuming no positive water feedback follows the satellite temperature changes very well, the mean absolute error (MAE) during the period from 2001 to July 2019 being 0.073°C and 0.082°C in respect to GISTEMP. The IPCC’s simple climate model shows for the same period errors of 0.191°C and 0.128°C respectively. The temperature in 2017-2018 was about 0.2°C above the average value in 2002–2014. The conclusion is that the pause was over after 2014 and the SW anomaly forcing was the major reason for this temperature increase. SW anomalies have had their greatest impacts on the global temperature during very strong (super) El Niño events in 1997-98 and 2015-16, providing a new perspective for ENSO events. A positive SW anomaly continued after 2015-16 which may explain the weak La Niña 2016 temperature impacts, and a negative SW anomaly after 1997-98 may have contributed two strong La Niña peaks 1998-2001. No cause and effect connection could be found between the SW radiation and temperature anomalies in Nino areas.

scholarly journals Seasonal Forecasting in the Pacific Using the Coupled Model POAMA-2

2013 ◽  
Vol 28 (3) ◽  
pp. 668-680 ◽  
Author(s):  
Andrew Cottrill ◽  
Harry H. Hendon ◽  
Eun-Pa Lim ◽  
Sally Langford ◽  
Kay Shelton ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Regional Climate ◽  
Coupled Model ◽  
Forecast Model ◽  
Seasonal Prediction ◽  
La Niña ◽  
Spatial And Temporal Variability ◽  
Seasonal Forecasts ◽  
La Nina

Abstract The development of a dynamical model seasonal prediction service for island nations in the tropical South Pacific is described. The forecast model is the Australian Bureau of Meteorology's Predictive Ocean–Atmosphere Model for Australia (POAMA), a dynamical seasonal forecast system. Using a hindcast set for the period 1982–2006, POAMA is shown to provide skillful forecasts of El Niño and La Niña many months in advance and, because the model faithfully simulates the spatial and temporal variability of rainfall associated with displacements of the southern Pacific convergence zone (SPCZ) and ITCZ during La Niña and El Niño, it also provides good predictions of rainfall throughout the tropical Pacific region. The availability of seasonal forecasts from POAMA should be beneficial to Pacific island countries for the production of regional climate outlooks across the region.

The Pacific’s Response to Surface Heating in 130 Yr of SST: La Niña–like or El Niño–like?

2010 ◽  
Vol 67 (8) ◽  
pp. 2649-2657 ◽  
Author(s):  
Ka-Kit Tung ◽  
Jiansong Zhou
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Walker Circulation ◽  
Dominant Mode ◽  
Equatorial Region ◽  
La Niña ◽  
Radiative Heating ◽  
Modified Method ◽  
La Nina

Abstract Using a modified method of multiple linear regression on instrumented sea surface temperature (SST) in the two longest historical datasets [the Extended Reconstructed SST dataset (ERSST) and the Met Office Hadley Centre Sea Ice and SST dataset (HadISST)], it is found that the response to increased greenhouse forcing is a warm SST in the mid- to eastern Pacific Ocean in the equatorial region in the annual or seasonal mean. The warming is robustly statistically significant at the 95% confidence level. Consistent with this, the smaller radiative heating from solar forcing produces a weak warming also in this region, and the spatial pattern of the response is neither La Niña–like nor El Niño–like. It is noted that previous reports of a cold-tongue (La Niña–like) response to increased greenhouse or to solar-cycle heating were likely caused by contaminations due to the dominant mode of natural response in the equatorial Pacific. The present result has implications on whether the Walker circulation is weakened or strengthened in a warmer climate and on coupled atmosphere–ocean climate model validation.

Identification of small summers in Southern Brazil and its relation with El Niño and La Niña events

2015 ◽  
Author(s):  
Lucas da Conceição ◽  
Humberto Conrado ◽  
Glauber Mariano ◽  
Ericka Mariano
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Southern Brazil ◽  
La Nina

Increased Occurrence of Stratospheric Sudden Warmings during El Niño as Simulated by WACCM

2006 ◽  
Vol 19 (3) ◽  
pp. 324-332 ◽  
Author(s):  
Masakazu Taguchi ◽  
Dennis L. Hartmann
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Distribution Functions ◽  
La Niña ◽  
Wave Forcing ◽  
Eddy Heat Flux ◽  
La Nina ◽  
Zonal Wavenumber ◽  
Stratospheric Sudden Warmings

Abstract Experiments with Whole Atmosphere Community Climate Model (WACCM) under perpetual January conditions indicate that stratospheric sudden warmings (SSWs) are twice as likely to occur in El Niño winters than in La Niña winters, in basic agreement with the limited observational dataset. Tropical SST anomalies that mimic El Niño and La Niña lead to changes in the shape of probability distribution functions (PDFs) of stratospheric day-to-day variability, resulting in a warmer pole and weaker vortex on average for El Niño conditions. The tropical SST forcing induces a response similar to the observed response in the enhancement of the planetary wave of zonal wavenumber 1 (wave 1) and the weakening of wave 2 in the upper troposphere and stratosphere of high latitudes. The enhanced wave 1 contributes to a shift of the PDFs of poleward eddy heat flux in the lower stratosphere, or wave forcing entering the stratosphere. The shift of the PDFs includes an increase of strong wave events that induce more frequent SSWs.

scholarly journals Predictability of the California Niño/Niña*

2015 ◽  
Vol 28 (18) ◽  
pp. 7237-7249 ◽  
Author(s):  
Takeshi Doi ◽  
Chaoxia Yuan ◽  
Swadhin K. Behera ◽  
Toshio Yamagata
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Regional Climate ◽  
Circulation Model ◽  
Seasonal Prediction ◽  
La Niña ◽  
Boreal Summer ◽  
La Nina ◽  
Basin Scale

Abstract Predictability of a recently discovered regional coupled climate mode called the California Niño (Niña) off Baja California and California is explored using a seasonal prediction system based on the Scale Interaction Experiment-Frontier, version 1 (SINTEX-F1) coupled ocean–atmosphere general circulation model. Because of the skillful prediction of basin-scale El Niño (La Niña), the California Niño (Niña) that co-occurs with El Niño (La Niña) with a peak in boreal winter is found to be predictable at least a couple of seasons ahead. On the other hand, the regional coupled phenomenon peaking in boreal summer without co-occurrence with El Niño (La Niña) is difficult to predict. The difficulty in predicting such an intrinsic regional climate phenomenon may be due to model deficiency in resolving the regional air–sea–land positive feedback processes. The model may also underestimate coastal Kelvin waves with a small offshore scale, which may play an important role in the generation of the California Niño/Niña. It may be improved by increasing horizontal resolution of the ocean component of the coupled model. The present study may provide a guideline to improve seasonal prediction of regional climate modes for important industrial as well as social applications.

scholarly journals Precipitation Anomalies in Southern Brazil Associated with El Niño and La Niña Events

1998 ◽  
Vol 11 (11) ◽  
pp. 2863-2880 ◽  
Author(s):  
Alice M. Grimm ◽  
Simone E. T. Ferraz ◽  
Júlio Gomes
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Southern Brazil ◽  
La Nina ◽  
Precipitation Anomalies

Influences of ENSO on Stratospheric Variability, and the Descent of Stratospheric Perturbations into the Lower Troposphere

2013 ◽  
Vol 26 (13) ◽  
pp. 4725-4748 ◽  
Author(s):  
Ying Li ◽  
Ngar-Cheung Lau
Keyword(s):  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Polar Vortex ◽  
La Niña ◽  
Stratospheric Polar Vortex ◽  
Near Surface ◽  
Annular Mode ◽  
Model Version ◽  
La Nina

Abstract The linkage between El Niño–Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) through the stratospheric pathway is examined using a global coupled climate model [GFDL Climate Model version 3 (CM3)], with increased vertical resolution and extent in the stratosphere as compared to an earlier model [GFDL Climate Model version 2 (CM2)]. It is demonstrated that the relationship between ENSO and NAO is stronger in CM3 than in CM2. It is found that ENSO plays an important role in modulating the frequency of occurrence of the stratospheric polar vortex anomalies through enhancement/attenuation of the amplitudes of zonal wavenumbers 1 and 2, especially in late winter. A higher frequency of weak (strong) stratospheric vortex events is simulated in CM3 during El Niño (La Niña) episodes. The weak vortex events during El Niño winters are preceded by enhancement of the zonal wave-1 pattern and weakening of zonal wave-2 pattern. These modified tropospheric planetary waves propagate upward and then weaken the stratospheric polar vortex through eddy–mean flow interaction. The zonal-mean geopotential response in the stratosphere propagates downward and weakens the polar vortex throughout the troposphere. The effects of planetary wave refraction in the upper troposphere on the zonally averaged circulation cells in the tropospheric meridional plane, and the linkage between the lower branches of these cells and the near-surface wind patterns, play an important role in the flow pattern over the region corresponding to the southern lobe of the NAO. Specifically, a negative annular mode and NAO response is discernible in weak stratospheric vortex events during El Niño. Conversely, the positive annular mode and NAO is evident in strong vortex events during La Niña.

scholarly journals The millennium water vapour drop in chemistry-climate model simulations

2015 ◽  
Vol 15 (17) ◽  
pp. 24909-24953 ◽  
Author(s):  
S. Brinkop ◽  
M. Dameris ◽  
P. Jöckel ◽  
H. Garny ◽  
S. Lossow ◽  
...  
Keyword(s):  
Water Vapour ◽  
El Niño ◽  
Lower Stratosphere ◽  
Climate Model ◽  
El Nino ◽  
La Niña ◽  
Quasi Biennial Oscillation ◽  
La Nina ◽  
Year 2000 ◽  
Stratospheric Water Vapour

Abstract. This study investigates the abrupt and severe water vapour decline in the stratosphere beginning in year 2000 (the "millennium water vapour drop") and other similar stratospheric water vapour drops by means of various simulations with the state-of-the-art Chemistry-Climate Model (CCM) EMAC (ECHAM/MESSy Atmospheric Chemistry Model). The CCM EMAC is able to reproduce the signature and pattern of the water vapour disturbances in agreement with those derived from satellite observations. Model data confirm that this extraordinary water vapour decline is in particular obvious in the tropical lower stratosphere. The starting point of the severe water vapour drop is identified in the tropical lower stratosphere and the start date is found to be in the early days of 2000. We show that the driving forces for this significant drop in water vapour mixing ratios are tropical sea surface temperature changes due to a preceding strong El Niño–Southern Oscillation event (1997/98), which was followed by a La Niña and supported by the prevailing western phase of the equatorial stratospheric quasi-biennial oscillation (QBO) at that time. This constellation of ENSO and QBO obviously lead to the outstanding anomalies in meteorological quantities which are identified in the equatorial atmosphere: (a) a distinct warming (up to 1 K) of the tropical upper troposphere (200 to 120 hPa) beginning in mid-1997 and lasting for about one and a half years, (b) a strong warming (up to 2.5 K) of the tropical lower stratosphere (100 to 50 hPa), beginning in early 1999 and ending in early 2000, and (c) a significantly enhanced upwelling at the tropopause in the late 1990s and an obviously reduced upwelling around the year 2000 followed by a period of enhanced upwelling again. These dynamically induced changes are unambiguously connected to the stratospheric water vapour anomaly. Similarly strong water vapour reductions are also found in other years, and seem to be a~typical feature after strong combined El Niño/La Niña events, if the QBO west phase has prolonged down to the tropopause.

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