scholarly journals Asymmetric Response of the Equatorial Pacific SST to Climate Warming and Cooling

2017 ◽  
Vol 30 (18) ◽  
pp. 7255-7270 ◽  
Author(s):  
Fukai Liu ◽  
Yiyong Luo ◽  
Jian Lu ◽  
Oluwayemi Garuba ◽  
Xiuquan Wan
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Dominant Role ◽  
Surface Heat ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Asymmetric Structure ◽  
Linear Component ◽  
Budget Analysis

Abstract The response of the equatorial Pacific Ocean to heat fluxes of equal amplitude but opposite sign is investigated using the Community Earth System Model (CESM). Results show a strong asymmetry in SST changes. In the eastern equatorial Pacific (EEP), the warming responding to the positive forcing exceeds the cooling response to the negative forcing, whereas in the western equatorial Pacific (WEP) it is the other way around and the cooling surpasses the warming. This leads to a zonal dipole asymmetric structure, with positive values in the east and negative values in the west. A surface heat budget analysis suggests that the SST asymmetry mainly results from the oceanic horizontal advection and vertical entrainment, with both of their linear and nonlinear components playing a role. For the linear component, its change appears to be more significant over the EEP (WEP) in the positive (negative) forcing scenario, favoring the seesaw pattern of the SST asymmetry. For the nonlinear component, its change acts to warm (cool) the EEP (WEP) in both scenarios, also favorable for the development of the SST asymmetry. Additional experiments with a slab ocean confirm the dominant role of ocean dynamical processes for this SST asymmetry. The net surface heat flux, in contrast, works to reduce the SST asymmetry through its shortwave radiation and latent heat flux components, with the former being related to the nonlinear relationship between SST and convection, and the latter being attributable to Newtonian damping and air–sea stability effects. The suppressing effect of shortwave radiation on SST asymmetry is further verified by partially coupled overriding experiments.

scholarly journals Contributions of Surface Heat Fluxes and Oceanic Processes to Tropical SST Changes: Seasonal and Regional Dependence

2017 ◽  
Vol 30 (11) ◽  
pp. 4185-4205 ◽  
Author(s):  
Zhuoqi He ◽  
Renguang Wu ◽  
Weiqiang Wang ◽  
Zhiping Wen ◽  
Dongxiao Wang
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Spatial Scales ◽  
Geographical Area ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Surface Heat Fluxes ◽  
Vertical Advection ◽  
Large Geographical Area

Abstract The present study employs six surface heat flux datasets and three ocean assimilation products to assess the relative contributions of surface heat fluxes and oceanic processes to the sea surface temperature (SST) change in the tropical oceans. Large differences are identified in the major terms of the heat budget equation. The largest discrepancies among different datasets appear in the contribution of vertical advection. The heat budget is nearly balanced in the shortwave-radiation- and horizontal-advection-dominant cases but not balanced in some of the latent-heat-flux- and vertical-advection-dominant cases. The contributions of surface heat fluxes and ocean advections to the SST tendency display remarkable seasonal and regional dependence. The contribution of surface heat fluxes covers a large geographical area. The oceanic processes dominate the SST tendency in the near-equatorial regions with large values but small spatial scales. In the Pacific and Atlantic Oceans, the SST tendency is governed by the dynamic and thermodynamic processes, respectively, while a wide variety of processes contribute to the SST tendency in the Indian Ocean. Several regions have been selected to illustrate the dominant contributions of individual terms to the SST tendency in different seasons. The seasonality and regionality of the interannual air–sea relationship indicate a physical connection with the mean state.

scholarly journals An Intermodel Approach to Identify the Source of Excessive Equatorial Pacific Cold Tongue in CMIP5 Models and Uncertainty in Observational Datasets

2015 ◽  
Vol 28 (19) ◽  
pp. 7630-7640 ◽  
Author(s):  
Gen Li ◽  
Yan Du ◽  
Haiming Xu ◽  
Baohua Ren
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Specific Humidity ◽  
Cmip5 Models ◽  
Climate Projections ◽  
Cold Tongue ◽  
Budget Analysis ◽  
Dynamic Cooling

Abstract An excessive cold tongue error in the equatorial Pacific has prevailed in several generations of climate models. However, the causes of this problem remain a mystery, partly owing to uncertainty and/or a lack of observational datasets. Based on the multimodel ensemble from phase 5 of the Coupled Model Intercomparison Project (CMIP5), this study introduces a novel intermodel approach to identify the bias source by going beyond comparison with observational datasets. Intermodel statistics show that the excessive cold tongue bias could be traced back to a too strong oceanic dynamic cooling linked to a too shallow thermocline along the equatorial Pacific. A heat budget analysis suggests that the excessive oceanic dynamic cooling is balanced by the surface latent heat flux (LHF) adjustment. This is consistent with a variety of oceanic and atmospheric observations but at odds with the popular objectively analyzed air–sea heat fluxes (OAFlux) products. Further analyses suggest an alarming overestimation of OAFlux net surface heat flux (Qnet) into the tropical Pacific, mainly ascribed to observational uncertainly in air specific humidity. Implications for intermodel statistics in assessing model processes, validating observational data, and regulating future climate projections are discussed.

Vertical Structure of the Upper–Indian Ocean Thermal Variability

2020 ◽  
Vol 33 (17) ◽  
pp. 7233-7253 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han ◽  
Fan Wang ◽  
Lei Zhang ◽  
Jing Duan
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Time Scale ◽  
Vertical Structure ◽  
Southern Oscillation ◽  
Linear Trend ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Turbulent Heat

AbstractMulti-time-scale variabilities of the Indian Ocean (IO) temperature over 0–700 m are revisited from the perspective of vertical structure. Analysis of historical data for 1955–2018 identifies two dominant types of vertical structures that account for respectively 70.5% and 21.2% of the total variance on interannual-to-interdecadal time scales with the linear trend and seasonal cycle removed. The leading type manifests as vertically coherent warming/cooling with the maximal amplitude at ~100 m and exhibits evident interdecadal variations. The second type shows a vertical dipole structure between the surface (0–60 m) and subsurface (60–400 m) layers and interannual-to-decadal fluctuations. Ocean model experiments were performed to gain insights into underlying processes. The vertically coherent, basinwide warming/cooling of the IO on an interdecadal time scale is caused by changes of the Indonesian Throughflow (ITF) controlled by Pacific climate and anomalous surface heat fluxes partly originating from external forcing. Enhanced changes in the subtropical southern IO arise from positive air–sea feedback among sea surface temperature, winds, turbulent heat flux, cloud cover, and shortwave radiation. Regarding dipole-type variability, the basinwide surface warming is induced by surface heat flux forcing, and the subsurface cooling occurs only in the eastern IO. The cooling in the southeast IO is generated by the weakened ITF, whereas that in the northeast IO is caused by equatorial easterly winds through upwelling oceanic waves. Both El Niño–Southern Oscillation (ENSO) and IO dipole (IOD) events are favorable for the generation of such vertical dipole anomalies.

Intraseasonal SST Variability and Air–Sea Interaction over the Kuroshio Extension Region during Boreal Summer

2012 ◽  
Vol 25 (5) ◽  
pp. 1619-1634 ◽  
Author(s):  
Lu Wang ◽  
Tim Li ◽  
Tianjun Zhou
Keyword(s):  
Heat Budget ◽  
Kuroshio Extension ◽  
Sensible Heat Flux ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Boreal Summer ◽  
Budget Analysis ◽  
Anomalous Anticyclone ◽  
Sst Warming ◽  
The Kuroshio

The structure and evolution characteristics of intraseasonal (20–100 day) variations of sea surface temperature (SST) and associated atmospheric and oceanic circulations over the Kuroshio Extension (KE) region during boreal summer are investigated, using satellite-based daily SST, observed precipitation data, and reanalysis data. The intraseasonal SST warming in the KE region is associated with an anomalous anticyclone in the overlying atmosphere, reduced precipitation, and northward and downward currents in the upper ocean. The corresponding atmospheric and oceanic fields during the SST cooling phase exhibit a mirror image with an opposite sign. A mixed layer heat budget analysis shows that the intraseasonal SST warming is primarily attributed to anomalous shortwave radiation and latent heat fluxes at the surface. The anomalous sensible heat flux and oceanic advection also have contributions, but with a much smaller magnitude. The SST warming caused by the atmospheric forcing further exerts a significant feedback to the atmosphere through triggering the atmospheric convective instability and precipitation anomalies. The so-induced heating leads to quick setup of a baroclinic response, followed by a baroclinic-to-barotropic transition. As a result, the atmospheric circulation changes from an anomalous anticyclone to an anomalous cyclone. This two-way interaction scenario suggests that the origin of the atmospheric intraseasonal oscillation over the KE region may partly arise from the local atmosphere–ocean interaction.

Surface heat fluxes in the Western Equatorial Pacific Ocean

1995 ◽  
Vol 13 (10) ◽  
pp. 1047-1053 ◽  
Author(s):  
N. C. Wells
Keyword(s):  
Heat Flux ◽  
Pacific Ocean ◽  
Latent Heat ◽  
Longwave Radiation ◽  
Surface Heat ◽  
Equatorial Pacific ◽  
Heat Fluxes ◽  
Equatorial Pacific Ocean ◽  
Net Heat Flux ◽  
Western Equatorial Pacific

Abstract. Estimates of the components of the surface heat flux in the Western Equatorial Pacific Ocean are presented for a 22-day period, together with a critical analysis of the errors. It is shown that the errors in latent heat, and solar and longwave radiation fluxes, dominate the net heat flux for this period. It is found that the net heat flux into the ocean over the 22-day period is not significantly different from zero. It is also demonstrated that because of the variability in daily averaged values of solar radiation and the latent heat of evaporation, a large number of independent flux measurements will be required to determine with confidence the climatological net heat flux in this region. The variability of latent fluxes over the 22-day period suggest that climatological estimates based on monthly mean observations may lead to a significant underestimate of the latent heat flux.

Equatorial Asymmetry of the East Pacific ITCZ: Observational Constraints on the Underlying Processes

2011 ◽  
Vol 24 (6) ◽  
pp. 1784-1800 ◽  
Author(s):  
Hirohiko Masunaga ◽  
Tristan S. L’Ecuyer
Keyword(s):  
Heat Flux ◽  
Mixed Layer ◽  
Seasonal Cycle ◽  
Heat Budget ◽  
Warm Pool ◽  
Surface Heat ◽  
Northeast Pacific ◽  
The North ◽  
Budget Analysis ◽  
East Pacific

Abstract The equatorial asymmetry of the east Pacific intertropical convergence zone (ITCZ) is explored on the basis of an ocean surface heat budget analysis carried out with a variety of satellite data products. The annual mean climatology of absorbed shortwave flux exhibits a pronounced meridional asymmetry due to a reduction of insolation by high clouds in the north ITCZ. Ocean mixed layer advection has the largest, if not exclusive, effect of counteracting this shortwave-exerted asymmetry. Other heat fluxes, in particular latent heat flux, predominate over the advective heat flux in magnitude but are secondary with respect to equatorial asymmetry. The asymmetry in advective heat flux stems from a warm pool off the Central American coast and, to a lesser extent, the North Equatorial Counter Current, neither of which exist in the Southern Hemisphere. The irregular continental geography presumably comes into play by generating a warm pool north of the equator and bringing cold waters to the south in the far eastern Pacific. In addition to the annual climatology, the north–south contrast in the seasonal cycle of surface heat flux is instrumental in sustaining the north ITCZ throughout the year. The northeast Pacific is exposed to a seasonal cycle that is considerably weaker than that in the southeast Pacific, arising from multiple causes including the finite eccentricity of the earth’s orbit and meridional gradient in mixed layer absorptivity. Simple experiments generating synthetic sea surface temperature (SST) illustrate that the muted seasonal cycle of heat flux forcing moderates the SST seasonal variability in the northeast Pacific and thus allows the north ITCZ to persist year round. Existing theories on the ITCZ asymmetry are briefly examined in light of the present findings.

scholarly journals A Study of Response of the Equatorial Pacific SST to Doubled-CO2 Forcing in the Coupled CAM–1.5-Layer Reduced-Gravity Ocean Model

2013 ◽  
Vol 43 (7) ◽  
pp. 1288-1300 ◽  
Author(s):  
Fan Jia ◽  
Lixin Wu
Keyword(s):  
Heat Flux ◽  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Heat Budget ◽  
Coupled Model ◽  
Ocean Model ◽  
Equatorial Pacific ◽  
Shortwave Radiation ◽  
Reduced Gravity

Abstract The response of the equatorial Pacific SST under CO2 doubling is investigated using Community Atmosphere Model, version 3.1 (CAM3.1)–1.5-layer reduced-gravity ocean (RGO) coupled model. A robust El Niño–like warming pattern is found in the equatorial Pacific. The surface heat budget analyses suggest the El Niño–like pattern results from a weakening of the Walker circulation. In the western equatorial Pacific, all the heat flux components are important to warm the ocean, with the vast majority canceled by entraiment cooling related to increased stratification. In the central-eastern Pacific, the oceanic horizontal advections along with longwave radiation and latent heat flux act to warm the ocean, with entrainment, shortwave radiation, and horizontal diffusion acting as damping terms. An enhanced annual cycle of SST in the equatorial Pacific is also found, which is driven by the ocean dynamical adjustments to changing winds in the eastern ocean. Although the ocean model used here is a simple reduced-gravity model, the El Niño–like response supports the results of some full ocean–atmosphere general circulation models (GCMs) performed for the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project (CMIP) phase-5, indicating that the CAM3.1–RGO model can be taken as a useful and efficient tool to study equatorial Pacific response under changing climate.

NFLUX Satellite-Based Surface Radiative Heat Fluxes. Part II: Gridded Products

2017 ◽  
Vol 56 (4) ◽  
pp. 1043-1057 ◽  
Author(s):  
Jackie C. May ◽  
Clark Rowley ◽  
Charlie N. Barron
Keyword(s):  
Heat Flux ◽  
Radiative Heat ◽  
Weather Prediction ◽  
Longwave Radiation ◽  
Ocean Surface ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Shortwave Radiation ◽  
Global Ocean ◽  
Clearness Index

AbstractThe Naval Research Laboratory (NRL) ocean surface flux (NFLUX) system provides near-real-time satellite-based gridded surface heat flux fields over the global ocean within hours of the observed satellite measurements. NFLUX can serve as an alternative to current numerical weather prediction models—in particular, the U. S. Navy Global Environmental Model (NAVGEM)—that provide surface forcing fields to operational ocean models. This study discusses the satellite-based shortwave and longwave global gridded analysis fields, which complete the full suite of NFLUX-provided ocean surface heat fluxes. A companion paper discusses the production of satellite swath-level surface shortwave radiation and longwave radiation estimates. The swath-level shortwave radiation estimates are converted into clearness-index values. Clearness index reduces the dependency on solar zenith angle, which allows for the assimilation of observations over a given time window. An automated quality-control process is applied to the swath-level estimates of clearness index and surface longwave radiation. Then 2D variational analyses of the quality-controlled satellite estimates with background atmospheric model fields form global gridded radiative heat flux fields. The clearness-index analysis fields are converted into shortwave analysis fields to be used in other applications. Three-hourly shortwave and longwave analysis fields are created from 1 May 2013 through 30 April 2014. These fields are validated against observations from research vessels and moored-buoy platforms and compared with NAVGEM. With the exception of the mean bias, the NFLUX fields have smaller errors when compared with those of NAVGEM.

Anthropogenic Warming of the Oceans: Observations and Model Results

2006 ◽  
Vol 19 (10) ◽  
pp. 1873-1900 ◽  
Author(s):  
David W. Pierce ◽  
Tim P. Barnett ◽  
Krishna M. AchutaRao ◽  
Peter J. Gleckler ◽  
Jonathan M. Gregory ◽  
...  
Keyword(s):  
Heat Flux ◽  
Surface Heat Flux ◽  
Climate Model ◽  
Heat Budget ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Anthropogenic Forcing ◽  
Model Version ◽  
Ocean Atmosphere ◽  
Longwave Flux

Abstract Observations show the oceans have warmed over the past 40 yr, with appreciable regional variation and more warming at the surface than at depth. Comparing the observations with results from two coupled ocean–atmosphere climate models [the Parallel Climate Model version 1 (PCM) and the Hadley Centre Coupled Climate Model version 3 (HadCM3)] that include anthropogenic forcing shows remarkable agreement between the observed and model-estimated warming. In this comparison the models were sampled at the same locations as gridded yearly observed data. In the top 100 m of the water column the warming is well separated from natural variability, including both variability arising from internal instabilities of the coupled ocean–atmosphere climate system and that arising from volcanism and solar fluctuations. Between 125 and 200 m the agreement is not significant, but then increases again below this level, and remains significant down to 600 m. Analysis of PCM’s heat budget indicates that the warming is driven by an increase in net surface heat flux that reaches 0.7 W m−2 by the 1990s; the downward longwave flux increases by 3.7 W m−2, which is not fully compensated by an increase in the upward longwave flux of 2.2 W m−2. Latent and net solar heat fluxes each decrease by about 0.6 W m−2. The changes in the individual longwave components are distinguishable from the preindustrial mean by the 1920s, but due to cancellation of components, changes in the net surface heat flux do not become well separated from zero until the 1960s. Changes in advection can also play an important role in local ocean warming due to anthropogenic forcing, depending on the location. The observed sampling of ocean temperature is highly variable in space and time, but sufficient to detect the anthropogenic warming signal in all basins, at least in the surface layers, by the 1980s.

Upper-Ocean Processes under the Stratus Cloud Deck in the Southeast Pacific Ocean

2010 ◽  
Vol 40 (1) ◽  
pp. 103-120 ◽  
Author(s):  
Yangxing Zheng ◽  
George N. Kiladis ◽  
Toshiaki Shinoda ◽  
E. Joseph Metzger ◽  
Harley E. Hurlburt ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Budget ◽  
Surface Heat ◽  
Open Ocean ◽  
Heat Fluxes ◽  
Upper Ocean ◽  
Stratus Cloud ◽  
Surface Heat Fluxes ◽  
Southeast Pacific ◽  
Ocean Processes

Abstract The annual mean heat budget of the upper ocean beneath the stratocumulus/stratus cloud deck in the southeast Pacific is estimated using Simple Ocean Data Assimilation (SODA) and an eddy-resolving Hybrid Coordinate Ocean Model (HYCOM). Both are compared with estimates based on Woods Hole Oceanographic Institution (WHOI) Improved Meteorological (IMET) buoy observations at 20°S, 85°W. Net surface heat fluxes are positive (warming) over most of the area under the stratus cloud deck. Upper-ocean processes responsible for balancing the surface heat flux are examined by estimating each term in the heat equation. In contrast to surface heat fluxes, geostrophic transport in the upper 50 m causes net cooling in most of the stratus cloud deck region. Ekman transport provides net warming north of the IMET site and net cooling south of the IMET site. Although the eddy heat flux divergence term can be comparable to other terms at a particular location, such as the IMET mooring site, it is negligible for the entire stratus region when area averaged because it is not spatially coherent in the open ocean. Although cold-core eddies are often generated near the coast in the eddy-resolving model, they do not significantly impact the heat budget in the open ocean in the southeast Pacific.

Sign in / Sign up

Export Citation Format

Share Document