scholarly journals The Impact of Ocean Data Assimilation on Seasonal-to-Interannual Forecasts: A Case Study of the 2006 El Niño Event

2010 ◽  
Vol 23 (15) ◽  
pp. 4080-4095 ◽  
Author(s):  
Shu-Chih Yang ◽  
Michele Rienecker ◽  
Christian Keppenne
Keyword(s):  
El Niño ◽  
Initial Conditions ◽  
El Nino ◽  
Warm Pool ◽  
Breeding Method ◽  
Central Pacific ◽  
Background Error ◽  
Mature Phase ◽  
El Niño Event ◽  
The Impact

Abstract This study investigates the impact of four different ocean analyses on coupled forecasts of the 2006 El Niño event. Forecasts initialized in June 2006 using ocean analyses from an assimilation that uses flow-dependent background error covariances are compared with those using static error covariances that are not flow dependent. The flow-dependent error covariances reflect the error structures related to the background ENSO instability and are generated by the coupled breeding method. The ocean analyses used in this study result from the assimilation of temperature and salinity, with the salinity data available from Argo floats. Of the analyses, the one using information from the coupled bred vector (BV) replicates the observed equatorial long wave propagation best and exhibits more warming features leading to the 2006 El Niño event. The forecasts initialized from the BV-based analysis agree best with the observations in terms of the growth of the warm anomaly through two warming phases. This better performance is related to the impact of the salinity analysis on the state evolution in the equatorial thermocline. The early warming is traced back to salinity differences in the upper ocean of the equatorial central Pacific, while the second warming, corresponding to the mature phase, is associated with the effect of the salinity assimilation on the depth of the thermocline in the western equatorial Pacific. The series of forecast experiments conducted here show that the structure of the salinity in the initial conditions is important to the forecasts of the extension of the warm pool and the evolution of the 2006 El Niño event.

scholarly journals The Role of Stochastic Forcing in Ensemble Forecasts of the 1997/98 El Niño

2009 ◽  
Vol 22 (10) ◽  
pp. 2526-2540 ◽  
Author(s):  
Li Shi ◽  
Oscar Alves ◽  
Harry H. Hendon ◽  
Guomin Wang ◽  
David Anderson
Keyword(s):  
El Niño ◽  
Initial Conditions ◽  
El Nino ◽  
Intraseasonal Variability ◽  
Coupled Model ◽  
Ensemble Spread ◽  
Coupled Models ◽  
Central Pacific ◽  
Ensemble Forecasts ◽  
The Impact

Abstract The impact of stochastic intraseasonal variability on the onset of the 1997/98 El Niño was examined using a large ensemble of forecasts starting on 1 December 1996, produced using the Australian Bureau of Meteorology Predictive Ocean Atmosphere Model for Australia (POAMA) seasonal forecast coupled model. This coupled model has a reasonable simulation of El Niño and the Madden–Julian oscillation, so it provides an ideal framework for investigating the interaction between the MJO and El Niño. The experiment was designed so that the ensemble spread was simply a result of internal stochastic variability that is generated during the forecast. For the initial conditions used here, all forecasts led to warm El Niño–type conditions with the amplitude of the warming varying from 0.5° to 2.7°C in the Niño-3.4 region. All forecasts developed an MJO event during the first 4 months, indicating that perhaps the background state favored MJO development. However, the details of the MJOs that developed during December 1996–March 1997 had a significant impact on the subsequent strength of the El Niño event. In particular, the forecasts with the initial MJOs that extended farther into the central Pacific, on average, led to a stronger El Niño, with the westerly winds in the western Pacific associated with the MJO leading the development of SST and thermocline anomalies in the central and eastern Pacific. These results imply a limit to the accuracy with which the strength of El Niño can be predicted because the details of individual MJO events matter. To represent realistic uncertainty, coupled models should be able to represent the MJO, including its propagation into the central Pacific so that forecasts produce sufficient ensemble spread.

scholarly journals Model study of the cross-tropopause transport of biomass burning pollution

2007 ◽  
Vol 7 (14) ◽  
pp. 3713-3736 ◽  
Author(s):  
B. N. Duncan ◽  
S. E. Strahan ◽  
Y. Yoshida ◽  
S. D. Steenrod ◽  
N. Livesey
Keyword(s):  
Biomass Burning ◽  
El Niño ◽  
Fossil Fuels ◽  
Extreme Event ◽  
El Nino ◽  
Deep Convection ◽  
Tropical Tropopause Layer ◽  
Tropical Tropopause ◽  
El Niño Event ◽  
The Impact

Abstract. We present a modeling study of the troposphere-to-stratosphere transport (TST) of pollution from major biomass burning regions to the tropical upper troposphere and lower stratosphere (UT/LS). TST occurs predominately through 1) slow ascent in the tropical tropopause layer (TTL) to the LS and 2) quasi-horizontal exchange to the lowermost stratosphere (LMS). We show that biomass burning pollution regularly and significantly impacts the composition of the TTL, LS, and LMS. Carbon monoxide (CO) in the LS in our simulation and data from the Aura Microwave Limb Sounder (MLS) shows an annual oscillation in its composition that results from the interaction of an annual oscillation in slow ascent from the TTL to the LS and seasonal variations in sources, including a semi-annual oscillation in CO from biomass burning. The impacts of CO sources that peak when ascent is seasonally low are damped (e.g. Southern Hemisphere biomass burning) and vice-versa for sources that peak when ascent is seasonally high (e.g. extra-tropical fossil fuels). Interannual variation of CO in the UT/LS is caused primarily by year-to-year variations in biomass burning and the locations of deep convection. During our study period, 1994–1998, we find that the highest concentrations of CO in the UT/LS occurred during the strong 1997–1998 El Niño event for two reasons: i. tropical deep convection shifted to the eastern Pacific Ocean, closer to South American and African CO sources, and ii. emissions from Indonesian biomass burning were higher. This extreme event can be seen as an upper bound on the impact of biomass burning pollution on the UT/LS. We estimate that the 1997 Indonesian wildfires increased CO in the entire TTL and tropical LS (>60 mb) by more than 40% and 10%, respectively, for several months. Zonal mean ozone increased and the hydroxyl radical decreased by as much as 20%, increasing the lifetimes and, subsequently TST, of trace gases. Our results indicate that the impact of biomass burning pollution on the UT/LS is likely greatest during an El Niño event due to favorable dynamics and historically higher burning rates.

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (3) ◽  
pp. 9743-9767 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. A new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM), with an improved general circulation model and an internally generated quasi-biennial oscillation (QBO), is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward planetary wave activity in the central South Pacific during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 3–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. OLR, streamfunction and Rossby wave energy diagnostics are used to show that the modelled QBO does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

On Abnormally Strong Currents Observed on the Northern Coast of Peru during the 2015-2016 El Niño

2021 ◽  
Vol 8 (4) ◽  
pp. 205-210
Author(s):  
Chang-Woong Shin ◽  
Dimitri Gutiérrez
Keyword(s):  
Mixed Layer ◽  
El Niño ◽  
El Nino ◽  
Current Data ◽  
Kelvin Waves ◽  
Coastal Current ◽  
Northern Coast ◽  
El Niño Event ◽  
Strong Current ◽  
The Impact

The northern coast of Peru is a region that can rapidly detect the impact of an El Niño. To investigate the effects of the 2015-2016 El Niño on the oceanographic environment of the northern coast of Peru, the temperature and current data obtained from moored equipment at an oil platform were analyzed. Strong coastal along-shore currents of more than 0.60 m·s-1 were observed three times, although the mean current speed was 0.10 m·s-1 flowing toward the south-southwest. After the first strong current, the bottom temperature increased and the mixed layer deepened and remained there during the El Niño event. The temperature reached a maximum after the strong coastal current, then decreased gradually. An analysis of wind and sea surface height anomalies revealed that the coastal strong current was caused by Kelvin waves and the deepening of the mixed layer was not related to local winds, but to coastal Kelvin waves from the equator during the El Niño event.

El Niño Modoki Impacts on Australian Rainfall

2009 ◽  
Vol 22 (11) ◽  
pp. 3167-3174 ◽  
Author(s):  
Andréa S. Taschetto ◽  
Matthew H. England
Keyword(s):  
El Niño ◽  
El Nino ◽  
Central Pacific ◽  
Maximum Rainfall ◽  
El Niño Modoki ◽  
El Niño Events ◽  
The Impact ◽  
Sst Anomalies ◽  
Australian Rainfall ◽  
El Nino Events

Abstract This study investigates interseasonal and interevent variations in the impact of El Niño on Australian rainfall using available observations from the postsatellite era. Of particular interest is the difference in impact between classical El Niño events wherein peak sea surface temperature (SST) anomalies appear in the eastern Pacific and the recently termed El Niño “Modoki” events that are characterized by distinct warm SST anomalies in the central Pacific and weaker cold anomalies in the west and east of the basin. A clear interseasonal and interevent difference is apparent, with the maximum rainfall response for Modoki events occurring in austral autumn compared to austral spring for classical El Niños. Most interestingly, the Modoki and non-Modoki El Niño events exhibit a marked difference in rainfall impact over Australia: while classical El Niños are associated with a significant reduction in rainfall over northeastern and southeastern Australia, Modoki events appear to drive a large-scale decrease in rainfall over northwestern and northern Australia. In addition, rainfall variations during March–April–May are more sensitive to the Modoki SST anomaly pattern than the conventional El Niño anomalies to the east.

scholarly journals Spatial and Temporal Analysis of El Niño Impact on Land and Forest Fire in Kalimantan and Sumatra

Agromet ◽  
2021 ◽  
Vol 35 (1) ◽  
pp. 1-10
Author(s):  
Sri Nurdiati ◽  
Ardhasena Sopaheluwakan ◽  
Pandu Septiawan
Keyword(s):  
Forest Fire ◽  
Forest Fires ◽  
El Niño ◽  
Fire Regime ◽  
El Nino ◽  
Function Analysis ◽  
Spatial And Temporal Patterns ◽  
El Niño Event ◽  
Dry Spell ◽  
The Impact

Land and forest fires in Kalimantan and Sumatra, Indonesia occurred annually at different magnitude and duration. Climate and sea interaction, like El Niño, influences the severity of dry seasons preceding the fires. However, research on the influence of El Niño intensity to fire regime in Kalimantan and Sumatra is limited. Therefore, this study aims to analyze the spatial and temporal patterns of the effects of El Niño intensity on land and forest fires in fire-prone provinces in Indonesia. Here, we applied the empirical orthogonal function analysis based on singular value decomposition to determine the dominant patterns of hotspots and rainfall data that evolve spatially and temporally. For analysis, the study required the following data: fire hotspots, dry-spell, and rainfall for period 2001-2019. This study revealed that El Niño intensity had a different impacts for each province. Generally, El Niño will influence the severity of forest fire events in Indonesia. However, we found that the impact of El Niño intensity varied for Kalimantan, South Sumatra, and Riau Province. Kalimantan was the most sensitive province to the El Niño event. The duration and number of hotspots in Kalimantan increased significantly even in moderate El Niño event. This was different for South Sumatra, where the duration and number of hotspots only increased significantly when a strong El Niño event occurred.

scholarly journals Impact of the El Niño type and PDO on the winter sub-seasonal North American zonal temperature dipole via the variability of positive PNA patterns

2021 ◽  
Author(s):  
Yao Ge ◽  
Dehai Luo
Keyword(s):  
North America ◽  
North American ◽  
El Niño ◽  
El Nino ◽  
Hadley Cell ◽  
Height Anomaly ◽  
Central Pacific ◽  
The West ◽  
Anticyclonic Anomaly ◽  
The Impact

Abstract In recent years, the winter (from December to February, DJF) North American surface air temperature (SAT) anomaly in midlatitudes shows a “warm west/cold east” (WWCE) dipole pattern. To some extent, the winter WWCE dipole can be considered as being a result of the winter mean of sub-seasonal WWCE events. In this paper, the Pacific SST condition linked to the sub-seasonal WWCE SAT dipole is investigated. It is found that while the sub-seasonal WWCE dipole is related to the positive Pacific North American (PNA+) pattern, the impact of the PNA+ on the WWCE dipole depends on the El Niño SST type and the phase of Pacific decadal Oscillation (PDO). For a central-Pacific (CP) type El Niño, the positive (negative) height anomaly center of PNA+ is located in the west (east) part of North America to result in an intensified WWCE dipole, though the positive PDO favors the WWCE dipole. In contrast, the WWCE dipole is suppressed under an Eastern-Pacific (EP) type El Niño because the PNA+ anticyclonic anomaly dominates the whole North America.Moreover, the physical cause of why the type of El Niño influences the PNA+ is further examined. It is found that the type of El Niño can significantly influence the location of PNA+ through changing North Pacific midlatitude westerly winds (NPWWs). For the CP-type El Niño, the eastward migration of PNA+ is suppressed to favor its anticyclonic (cyclonic) anomaly appearing in the west (east) region of North American owing to reduced NPWWs. But for the EP-type El Niño, NPWWs are intensified to cause the appearance of the PNA+ anticyclonic anomaly over the whole North America due to enhanced Hadley cell and Ferrell cell.

scholarly journals Influence of Natural Climate Variability on Extreme Wave Power over Indo-Pacific Ocean Assessed using ERA5

2021 ◽  
Author(s):  
Prashant Kumar ◽  
Sukhwinder Kaur ◽  
Evan Weller ◽  
Ian R. Young
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Climate Variability ◽  
El Niño ◽  
El Nino ◽  
Extreme Value Analysis ◽  
Wave Power ◽  
Central Pacific ◽  
Natural Climate ◽  
The Impact

Abstract In recent decades, wave power (WP) energy from the ocean is one of the cleanest renewable energy sources associated with oceanic warming. In Indo-Pacific Ocean, the WP is significantly influenced by natural climate variabilities, such as El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). In this study, the impact of major climate variability modes on seasonal extreme WP is examined over the period 1979–2019 using ERA5 reanalysis data and the non-stationary generalized extreme value analysis is applied to estimate the climatic extremes. Independent ENSO influence after removing the IOD trends (ENSO|IOD) on WP are evident over the eastern and central Pacific during December–February (DJF) and March–May (MAM), respectively, which subsequently shifts towards the western Pacific in June–August (JJA) and September–November (SON). The ENSO|PDO impact on WP exhibits similar yet weaker intensity year round compared to ENSO. Extreme WP responses due to the IOD|ENSO include widespread decreases over the tropical and eastern Indian Ocean (IO), with localized increases only over the South China and Philippine (SCP) seas and Bay of Bengal (BOB) during JJA, and the Arabian Sea during SON. Lastly, for the PDO|ENSO, the significant increases in WP are mostly confined to the Pacific, and most prominent in the North Pacific. Composite analysis of different phase combinations of PDO (IOD) with El Niño (La Niña) reveals stronger (weaker) influences year-round. The response patterns in significant wave height (SWH), peak wave period (PWP), sea surface temperatures (SST), and sea level pressure (SLP) helps to explain the seasonal variations in WP.

Indian Ocean impact on ENSO evolution 2014-2016 in a set of seasonal forecasting experiments

2020 ◽  
Author(s):  
Michael Mayer ◽  
Magdalena Alonso Balmaseda
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Initial Conditions ◽  
El Nino ◽  
Tropical Pacific ◽  
Seasonal Forecasting ◽  
The Indian Ocean ◽  
The Impact ◽  
The Tropical Pacific

<p>In 2014 the scientific community and forecasters were expecting a major El Nino event, which was suggested by physical indicators and predicted by several seasonal forecasting systems. However, only moderately warm El Nino – Southern-Oscillation (ENSO) conditions materialized in 2014, but one year later in boreal winter 2015/16, one of the strongest El Ninos on record occurred. Moreover, the 2015/16 El Nino exhibited very unusual energetics: Despite warm conditions in the tropical Pacific in 2014 and especially 2015, its ocean heat content (OHC) did not decrease during that period, which usually is the case during El Nino events. Overall, the 2014-16 evolution of the tropical Pacific was quite different from the evolution during the 1997/98 El Nino, which exhibited exceptionally strong Pacific OHC discharge. This discrepancy was attributed at least partly to the anomalously warm Indian Ocean and the exceptionally weak Indonesian Throughflow transports during 2015-16 that kept Pacific OHC at high levels.</p><p>This contribution aims to elucidate the role of the Indian Ocean in the tropical Pacific Ocean evolution during ENSO for the two periods February 1997-1999 and February 2014-2016. For this purpose, we perform initialized two-year predictions using the ECMWF seasonal forecasting system. To isolate the role of the Indian Ocean, we carry out hindcasts with unperturbed ocean initial conditions and hindcasts with swapped Indian Ocean initial conditions, where the 2014 (1997) hindcasts use Indian Ocean initial conditions from 1997 (2014). We first investigate the impact of the Indian Ocean on the strength of the Indonesian Throughflow and the evolution of the tropical Pacific heat budget. Second, we seize these experiments to explore the impact of the Indian Ocean state on two-yearly ENSO evolution, especially on the probability of extreme events, and which role the atmospheric bridge plays versus the oceanic bridge.</p>

scholarly journals Response of the Antarctic stratosphere to warm pool El Niño Events in the GEOS CCM

2011 ◽  
Vol 11 (18) ◽  
pp. 9659-9669 ◽  
Author(s):  
M. M. Hurwitz ◽  
I.-S. Song ◽  
L. D. Oman ◽  
P. A. Newman ◽  
A. M. Molod ◽  
...  
Keyword(s):  
El Niño ◽  
Planetary Wave ◽  
Lower Stratosphere ◽  
El Nino ◽  
Warm Pool ◽  
Wave Activity ◽  
Central Pacific ◽  
Quasi Biennial Oscillation ◽  
South Central ◽  
The Antarctic

Abstract. The Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to investigate the response of the Antarctic stratosphere to (1) warm pool El Niño (WPEN) events and (2) the sensitivity of this response to the phase of the QBO. A new formulation of the GEOS V2 CCM includes an improved general circulation model and an internally generated quasi-biennial oscillation (QBO). Two 50-yr time-slice simulations are forced by repeating annual cycles of sea surface temperatures and sea ice concentrations composited from observed WPEN and neutral ENSO (ENSON) events. In these simulations, greenhouse gas and ozone-depleting substance concentrations represent the present-day climate. The modelled responses to WPEN, and to the phase of the QBO during WPEN, are compared with NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. WPEN events enhance poleward tropospheric planetary wave activity in the central South Pacific region during austral spring, leading to relative warming of the Antarctic lower stratosphere in November/December. During the easterly phase of the QBO (QBO-E), the GEOS V2 CCM reproduces the observed 4–5 K warming of the polar region at 50 hPa, in the WPEN simulation relative to ENSON. In the recent past, the response to WPEN events was sensitive to the phase of the QBO: the enhancement in planetary wave driving and the lower stratospheric warming signal were mainly associated with WPEN events coincident with QBO-E. In the GEOS V2 CCM, however, the Antarctic response to WPEN events is insensitive to the phase of the QBO: the modelled response is always easterly QBO-like. The QBO signal does not extend far enough into the lower stratosphere and upper troposphere to modulate convection and thus planetary wave activity in the south central Pacific.

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