Subseasonal SST Variability in the Tropical Eastern North Pacific during Boreal Summer

2008 ◽  
Vol 21 (17) ◽  
pp. 4149-4167 ◽  
Author(s):  
Eric D. Maloney ◽  
Dudley B. Chelton ◽  
Steven K. Esbensen
Keyword(s):  
Costa Rica ◽  
Warm Pool ◽  
Boreal Summer ◽  
Sst Variability ◽  
East Pacific ◽  
Pacific Warm Pool ◽  
Northern Edge ◽  
Precipitation Anomalies ◽  
Sst Anomalies ◽  
Costa Rica Dome

Abstract Boreal summer intraseasonal (30–90-day time scale) sea surface temperature (SST) variability in the east Pacific warm pool is examined using Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) sea surface temperatures during 1998–2005. Intraseasonal SST variance maximizes at two locations in the warm pool: in the vicinity of 9°N, 92°W near the Costa Rica Dome and near the northern edge of the warm pool in the vicinity of 19°N, 108°W. Both locations exhibit a significant spectral peak at 50–60-day periods, time scales characteristic of the Madden–Julian oscillation (MJO). Complex empirical orthogonal function (CEOF) and spectra coherence analyses are used to show that boreal summer intraseasonal SST anomalies are coherent with precipitation anomalies across the east Pacific warm pool. Spatial variations of phase are modest across the warm pool, although evidence exists for the northward progression of intraseasonal SST and precipitation anomalies. Intraseasonal SSTs at the north edge of the warm pool lag those in the vicinity of the Costa Rica Dome by about 1 week. The MJO explains 30%–40% of the variance of intraseasonal SST anomalies in the east Pacific warm pool during boreal summer. Peak-to-peak SST variations of 0.8°–1.0°C occur during MJO events. SST is approximately in quadrature with MJO precipitation, with suppressed (enhanced) MJO precipitation anomalies leading positive (negative) SST anomalies by 7–10 days. Consistent with the CEOF and coherence analyses, MJO-related SST and precipitation anomalies near the Costa Rica Dome lead those at the northern edge of the warm pool by about 1 week.

Mixed layer modeling in the East Pacific warm pool during 2002

2011 ◽  
Vol 38 (11-12) ◽  
pp. 2559-2573 ◽  
Author(s):  
Luke P. Van Roekel ◽  
Eric D. Maloney
Keyword(s):  
Mixed Layer ◽  
Warm Pool ◽  
East Pacific ◽  
Pacific Warm Pool

scholarly journals On the Convective Coupling and Moisture Organization of East Pacific Easterly Waves

2015 ◽  
Vol 72 (10) ◽  
pp. 3850-3870 ◽  
Author(s):  
Adam V. Rydbeck ◽  
Eric D. Maloney
Keyword(s):  
Life Cycle ◽  
Zonal Wind ◽  
Wind Shear ◽  
Warm Pool ◽  
Moisture Gradient ◽  
Easterly Waves ◽  
East Pacific ◽  
Pacific Warm Pool ◽  
Meridional Winds ◽  
The Mean

Abstract Processes associated with the local amplification of easterly waves (EWs) in the east Pacific warm pool are explored. Developing EWs favor convection in the southwest and northeast quadrants of the disturbance. In nascent EWs, convection favors the southwest quadrant. As the EW life cycle progresses, convection in the northeast quadrant becomes increasingly prominent and southwest quadrant convection wanes. The EW moisture budget reveals that anomalous meridional winds acting on the mean meridional moisture gradient of the ITCZ produce moisture anomalies supportive of convection in the southwest quadrant early in the EW life cycle. As EWs mature, moisture anomalies on the poleward side of the EW begin to grow and are supported by the advection of anomalous moisture by the mean zonal wind. In the southwest and northeast portions of the wave, where convection anomalies are favored, lower-tropospheric vorticity is generated locally through vertical stretching that supports a horizontal tilt of the wave from the southwest to the northeast. EWs with such tilts are then able to draw energy via barotropic conversion from the background cyclonic zonal wind shear present in the east Pacific. Convection anomalies associated with EWs vary strongly with changes in the background intraseasonal state. EWs during westerly and neutral intraseasonal periods are associated with robust convection anomalies. Easterly intraseasonal periods are, at times, associated with very weak EW convection anomalies because of weaker moisture and diluted CAPE variations.

Regime Change of the Boreal Summer Hadley Circulation and Its Connection with the Tropical SST

2011 ◽  
Vol 24 (15) ◽  
pp. 3867-3877 ◽  
Author(s):  
Ran Feng ◽  
Jianping Li ◽  
Jincheng Wang
Keyword(s):  
High Frequency ◽  
Regime Change ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Asymmetric Mode ◽  
Pacific Warm Pool ◽  
Highly Correlated ◽  
Relationship Of

Abstract The year-to-year variability of the boreal summer [June–August (JJA)] Hadley circulation (HC) is dominated by an asymmetric mode centered in the Northern Hemisphere (AMN) and a quasi-symmetric mode centered at 5°N (QSM). The regime change of the JJA HC is revealed by the phase reversal of the time series of the AMN, showing significant weakening of the northern part of the JJA HC and a reversed seesaw relationship of the zonal-mean updraft over 10°–20°N and around the equator. This transition is accompanied by the southward retreat of the HC core and is well correlated with the weakening of tropical summer monsoons. The strong warming trends of the sea surface temperature over the tropical Atlantic and Indo–west Pacific warm pool play an important role in the regime change of the JJA HC. The high-frequency interannual variability of the JJA HC, however, is mainly featured by the QSM and is highly correlated with the Niño-3.4 index, implying that ENSO’s influence is mainly on the high-frequency interannual time scale.

scholarly journals Satellite and Buoy Observations of Boreal Summer Intraseasonal Variability in the Tropical Northeast Pacific

2007 ◽  
Vol 135 (1) ◽  
pp. 3-19 ◽  
Author(s):  
Eric D. Maloney ◽  
Steven K. Esbensen
Keyword(s):  
Heat Flux ◽  
Wind Speed ◽  
Latent Heat ◽  
Latent Heat Flux ◽  
Intraseasonal Variability ◽  
Warm Pool ◽  
East Pacific ◽  
Pacific Warm Pool ◽  
Westerly Flow ◽  
Trmm Precipitation

Abstract Tropical intraseasonal variability in the eastern North Pacific during June–September of 2000–03 is analyzed using satellite and buoy observations. Quick Scatterometer ocean vector winds and the Tropical Rainfall Measuring Mission (TRMM) precipitation indicate that periods of anomalous surface westerly flow over the east Pacific warm pool during a summertime intraseasonal oscillation (ISO) life cycle are generally associated with an enhancement of convection to the east of 120°W. An exception is a narrow band of suppressed precipitation along 8°N that is associated with negative column-integrated precipitable water anomalies and anticyclonic vorticity anomalies. Periods of surface easterly anomalies are generally associated with suppressed convection to the east of 120°W. Summertime wind jets in the Gulfs of Tehuantepec and Papagayo exhibit heightened activity during periods of ISO easterly anomalies and suppressed convection. Strong variations in east Pacific warm pool wind speed occur in association with the summertime ISO. Anomalous ISO westerly flow is generally accompanied by enhanced wind speed to the east of 120°W, while anomalous easterly flow is associated with suppressed wind speed. Intraseasonal vector wind anomalies added to the climatological flow account for the bulk of the wind speed enhancement in the warm pool during the westerly phase, while the easterly phase shows strong contributions to the negative wind speed anomaly from both intraseasonal vector wind anomalies and suppressed synoptic-scale eddy activity. An analysis using Tropical Atmosphere Ocean buoys and TRMM precipitation suggests that wind–evaporation feedback is important for supporting summertime intraseasonal convection over the east Pacific warm pool. A statistically significant correlation of 0.6 between intraseasonal latent heat flux and precipitation occurs at the 12°N, 95°W buoy. Correlations between precipitation and latent heat flux at the 10°N, 95°W and 8°N, 95°W buoys are positive (0.4), but not statistically significant. Intraseasonal latent heat flux anomalies at all buoys are primarily wind induced. Consistent with the suppressed convection there during the ISO westerly phase, a negative but not statistically significant correlation (−0.3) occurs between precipitation and latent heat flux at the 8°N, 110°W buoy.

scholarly journals Influence of the Madden–Julian Oscillation and Caribbean Low-Level Jet on East Pacific Easterly Wave Dynamics

2018 ◽  
Vol 75 (4) ◽  
pp. 1121-1141 ◽  
Author(s):  
Justin W. Whitaker ◽  
Eric D. Maloney
Keyword(s):  
Warm Pool ◽  
Central American ◽  
Madden Julian Oscillation ◽  
Easterly Waves ◽  
Low Level ◽  
East Pacific ◽  
Pacific Warm Pool ◽  
Low Level Jet ◽  
Favorable Conditions ◽  
Relationship Of

Abstract The east Pacific warm pool exhibits basic-state variability associated with the Madden–Julian oscillation (MJO) and Caribbean low-level jet (CLLJ), which affects the development of easterly waves (EWs). This study compares and contrasts composite changes in the background environment, eddy kinetic energy (EKE) budgets, and EW tracks during MJO and CLLJ events. While previous studies have shown that the MJO influences jet activity in the east Pacific, the influence of the MJO and CLLJ on the east Pacific and EWs is not synonymous. The CLLJ is a stronger modulator of the ITCZ than the MJO, while the MJO has a more expansive influence on the northeastern portion of the basin. Anomalous low-level westerly MJO and CLLJ periods are associated with favorable conditions for EW development paralleling the Central American coast, contrary to previous findings about the relationship of the CLLJ to EWs. Easterly MJO and CLLJ periods support enhanced ITCZ EW development, although the CLLJ is a greater modulator of EW tracks in this region, which is likely associated with stronger moisture and convection variations and their subsequent influence on the EKE budget. ITCZ EW growth during easterly MJO periods is more reliant on barotropic conversion than during strong CLLJ periods, when eddy available potential energy (EAPE)-to-EKE conversion associated with ITCZ convection is more important. Thus, the influence of these phenomena on east Pacific EWs should be considered distinct.

How Many ENSO Flavors Can We Distinguish?*

2013 ◽  
Vol 26 (13) ◽  
pp. 4816-4827 ◽  
Author(s):  
Nathaniel C. Johnson
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Pool ◽  
Tropical Pacific ◽  
La Niña ◽  
Western Pacific ◽  
Western Pacific Warm Pool ◽  
La Nina ◽  
Pacific Warm Pool ◽  
Sst Anomalies

Abstract It is now widely recognized that El Niño–Southern Oscillation (ENSO) occurs in more than one form, with the canonical eastern Pacific (EP) and more recently recognized central Pacific (CP) ENSO types receiving the most focus. Given that these various ENSO “flavors” may contribute to climate variability and long-term trends in unique ways, and that ENSO variability is not limited to these two types, this study presents a framework that treats ENSO as a continuum but determines a finite maximum number of statistically distinguishable representative ENSO patterns. A neural network–based cluster analysis called self-organizing map (SOM) analysis paired with a statistical distinguishability test determines nine unique patterns that characterize the September–February tropical Pacific SST anomaly fields for the period from 1950 through 2011. These nine patterns represent the flavors of ENSO, which include EP, CP, and mixed ENSO patterns. Over the 1950–2011 period, the most significant trends reflect changes in La Niña patterns, with a shift in dominance of La Niña–like patterns with weak or negative western Pacific warm pool SST anomalies until the mid-1970s, followed by a dominance of La Niña–like patterns with positive western Pacific warm pool SST anomalies, particularly after the mid-1990s. Both an EP and especially a CP El Niño pattern experienced positive frequency trends, but these trends are indistinguishable from natural variability. Overall, changes in frequency within the ENSO continuum contributed to the pattern of tropical Pacific warming, particularly in the equatorial eastern Pacific and especially in relation to changes of La Niña–like rather than El Niño–like patterns.

Decadal Variability of the Indo-Pacific Warm Pool and Its Association with Atmospheric and Oceanic Variability in the NCEP–NCAR and SODA Reanalyses

2008 ◽  
Vol 21 (21) ◽  
pp. 5545-5565 ◽  
Author(s):  
Hui Wang ◽  
Vikram M. Mehta
Keyword(s):  
Decadal Variability ◽  
Gulf Coast ◽  
Phase Relationship ◽  
Warm Pool ◽  
The United States ◽  
Function Technique ◽  
Pacific Warm Pool ◽  
Rainfall Anomalies ◽  
Upper Level ◽  
Sst Anomalies

Abstract Decadal variability of the Indo-Pacific warm pool (IPWP) sea surface temperature (SST) and its association with atmospheric and oceanic circulations are investigated with observed 50-yr (1952–2001) SST, and the NCEP–NCAR atmospheric and Simple Ocean Data Assimilation (SODA) oceanic reanalysis data. The decadal variability of the IPWP SSTs was analyzed by applying an empirical orthogonal function technique to low-pass-filtered SSTs. Two leading empirical modes (EMs) well represent the IPWP SST decadal variations. EM1 is an ENSO-like pattern with out-of-phase SST anomalies in the western Pacific and the Indian Ocean, whereas EM2 displays an in-phase relationship between SST anomalies in the two regions. Consequently, spatial evolution of EM1 is dominated by opposing changes in zonal and meridional dimensions and thus a strong deformation of the warm pool on decadal time scales. EM2 is dominated by changes in size and intensity of the warm pool. Analyses of ocean thermodynamic fields associated with the two SST EMs indicate that decadal changes in the IPWP can extend down to 300-m depth. Oceanic processes may thus be involved in the IPWP decadal variability, including advections of mean temperature by both mean and anomalous ocean currents and effects of shallow tropical circulations (STCs) on the IPWP SST, which is consistent with some previous studies on tropical decadal variability. The results may also indicate the existence of both positive and negative feedbacks between the IPWP SST and the STCs. Both December–January–February (DJF) and June–July–August (JJA) atmospheric circulations exhibit thermally direct responses to the two decadal IPWP SST EMs by altering the Hadley and Walker circulations. In addition, significant upper-level rotational flow anomalies in the extratropics are found to be associated with the decadal IPWP SST variability. Consistent with the upper-level flow anomalies and 850-hPa convergence–divergence patterns associated with the two SST EMs are rainfall anomalies over the United States. In DJF, the rainfall anomalies are mainly in Florida, the Gulf Coast, southern Texas, Arizona, and along the West Coast. In JJA, the rainfall anomalies are mainly in the Midwest and the Southeast. Since these rainfall anomalies are a significant fraction of seasonal-average rainfall and since these anomalies persist for many years, they potentially make a significant impact on U.S. water resources and agriculture. Further analysis of observations and modeling studies are required to understand the physics of the IPWP SST decadal variability and its impacts on global climate, and to assess its predictability.

scholarly journals Moist Dynamical Linkage between the Equatorial Indian Ocean and the South Asian Monsoon Trough*

2010 ◽  
Vol 67 (3) ◽  
pp. 589-610 ◽  
Author(s):  
H. Annamalai
Keyword(s):  
Indian Ocean ◽  
Moisture Content ◽  
Equatorial Indian Ocean ◽  
Monsoon Trough ◽  
Boreal Summer ◽  
Coupled Models ◽  
Precipitation Anomalies ◽  
Anomalous Wind ◽  
Normal Rainfall ◽  
Sst Anomalies

Abstract During boreal summer, both the monsoon trough and the equatorial Indian Ocean (EIO) receive intense climatological precipitation. At various time scales, EIO sea surface temperature (SST) and/or precipitation variations interact with rainfall along the trough. For instance, during July–August in strong Indian Ocean dipole/zonal mode (IODZM) years, EIO experiences below-normal rainfall while regions along the monsoon trough receive above-normal rainfall. A lack of spatial coherency between SST and precipitation variations is noted in both regions. This paper posits the hypothesis that interaction between equatorial waves and moist physics is important in determining precipitation anomalies over these regions and in setting up the teleconnection. The hypothesis is tested using a linear baroclinic model (LBM). IODZM-related SST anomalies derived from multicentury integrations of the Geophysical Fluid Dynamics Laboratory coupled model (GFDL CM2.1) are used to force the LBM. Consistent with observations and CM2.1 composites of strong IODZM events, steady-state LBM solutions simulate zonally oriented negative (positive) precipitation anomalies over the EIO (along the monsoon trough). To identify the processes simulated in the LBM, moisture and moist static energy budgets are examined. Over both regions, analyses reveal that moisture advection contributes the most to the LBM budget, with advection of climatological moisture by the anomalous wind being the principal factor. Specifically, in response to cold SST anomalies in the EIO, moist stability due to surface fluxes increases, giving rise to below-normal rainfall. These conditions produce anomalous anticyclonic circulation as a Rossby wave response in the lower troposphere. Over the central-eastern EIO, this anomalous circulation advects climatological air of lower moisture content from the subtropics. In addition, advection of anomalous moisture by both climatological and anomalous wind results in anomalous dry conditions over the entire EIO. In contrast, anomalous divergent circulations that emanate from the EIO advect climatological air of higher moisture content from the equatorial region, amplifying rainfall along the monsoon trough. Consequently, the two regions are connected by a thermally driven overturning meridional circulation. Budget diagnostics performed with CM2.1 composites and the ECMWF interim reanalysis for observed IODZM events support the hypothesis. The results here imply that in coupled models, realistic representation of the basic state and details of the moist processes are necessary for successful monsoon prediction.

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