Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network Research Articles

High‐Resolution Gridded Temperature and Salinity Fields From Argo Floats Based on a Spatiotemporal Four‐Dimensional Multigrid Analysis Method

AbstractThe shortage of in situ ocean observations greatly limits the development of gridded ocean subsurface environmental analysis products. Fully using the correlated information of the observations in time and space is an appropriate approach to this problem. Here we adopt a method of spatiotemporal four‐dimensional multigrid analysis. A weekly gridded Argo product is also constructed in the Northwest Pacific Ocean (0°–40°N, 120°–152°E) from 2005 to 2020, with a horizontal resolution of 0.5° × 0.5° and 65 layers in the upper 1,500 m. Then, the gridded Argo product is evaluated by using in situ Argo floats, satellite altimeter data, the Tropical Atmosphere Ocean/Triangle Trans‐Ocean Buoy Network (TAO/TRITON), high‐resolution shipboard observations and some global gridded Argo products. Compared with in situ Argo floats, the reconstructed fields retain the spatiotemporal information of Argo floats well. The maximum vertical root mean square errors of temperature and salinity between the gridded Argo product and in situ Argo floats are less than 0.47°C and 0.06 psu respectively. In addition, the product agrees well with independent observations of satellite altimeter data, TAO/TRITON. Compared with shipboard observations, the product can well reflect the structure of mesoscale eddies and detect some small‐scale water masses. Compared with global gridded Argo products, our product retains more mesoscale features and has spatiotemporal correlation.

Examination of the Daily Cycle Wind Vector Modes of Variability from the Constellation of Microwave Scatterometers and Radiometers

Offshore of many coastal regions, the ocean surface wind varies in speed and direction throughout the day, owing to forcing from land/sea temperature differences and orographic effects. Far offshore, both diurnal and semidiurnal wind vector variability has been noted in the Tropical Atmosphere Ocean-TRIangle Trans-Ocean buoy Network (TAO-TRITON) mooring data in the tropical Pacific Ocean. In this manuscript, the tropical diurnal wind variability is examined with microwave radiometer-derived winds from the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM), merged with RapidScat and other scatterometer data. Since the relationship between wind speed and its zonal and meridional components is nonlinear, this manuscript describes an observationally based methodology to merge the radiometer and scatterometer-based wind estimates as a function of observation time, to generate a multi-year dataset of diurnal wind variability. Compared to TAO-TRITON mooring array data, the merged satellite-derived wind components fairly well replicate the semidiurnal zonal wind variability over the tropical Pacific but generally show more variability in the meridional wind components. The meridional component agrees with the associated mooring location data in some locations better than others, or it shows no clear dominant diurnal or semidiurnal mode. Similar discrepancies are noted between two forecast model reanalysis products. It is hypothesized that the discrepancies amongst the meridional winds are due to interactions between surface convergence and convective precipitation over tropical ocean basins.

How strong was the 2015/2016 El Niño event?

On the interannual timescale, the Indonesian climate is strongly influenced by a coupled ocean-atmosphere modes in the tropical Pacific Ocean. During a warm phase (El Niño event), negative sea surface temperature anomalies (SSTA) in the western tropical Pacific lead to suppress convection activities causing reduce precipitation over the maritime continent. The situation is reverse during the cold season(La Niña event). In this study, the evolution of 2015/2016 El Niño event is evaluated based on the collected data by the Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) buoys. The results show that the evolution of the event has started in boreal spring (April – May 2015). It came to thepeak in boreal fall/winter (October – December 2015). The event lasted until boreal spring before it terminated in April/May 2016. In addition, the intensity of the event is classified as a strong event, and it is one of the strongest El Niño events during the last three decades.

The net energy budget at the ocean‐atmosphere interface of the “Cold Tongue” region

AbstractPacific “Cold Tongue” (PCT) sea surface temperature (SST) experiences significant (>0.5°C) interannual variations forced by the El‐Nino Southern Oscillations (ENSO) with global impacts on the Earth climate. In this study, we estimate the PCT net heat budget known to be difficult to derive using numerical models. The main goal is to determine how accurately the net heat flux across the surface/atmosphere interface can currently be determined primarily, from satellite observations; these are first evaluated against the nearest available observations inside and outside the PCT of the Tropical Pacific Ocean, using buoy arrays such as the Tropical Atmosphere Ocean/Triangle Trans‐Ocean Buoy Network (TAO/TRITON). It was found that the satellite‐based estimates of both turbulent and radiative fluxes are in better agreement with the observations than similar estimates from leading numerical models. The monthly mean satellite estimates of PCT SW↓ during January/July 2009 were 273.07/170.14, for LW↓, latent heat and sensible heat they were 378.79/365.54, 95.52/130.31, 9.89/20.67, respectively (all in W/m2). The estimated standard deviations for PCT SW↓ were in the range of 7.2–7.8% of the mean and in the range of 2.0–2.5% for LW↓, at daily time scale. Satellite estimates of both PCT LHF and SHF exhibit much higher variability, characterized by standard deviations of 50% from the mean values.

Validating satellite altimeter measurements of internal tides with long‐term TAO/TRITON buoy observations at 2°S–156°E

AbstractSatellite altimetry is regularly used to map the global distribution of mode‐1 internal tides. Validating altimeter measurements of internal tides with in situ data is difficult as the mooring observations typically are too short compared with the altimetry. Here taking advantage of the long‐term (since 1999) Tropical Atmosphere‐Ocean/Triangle Trans‐Ocean Buoy Network (TAO/TRITON) buoy observations at 2°S–156°E located at a TOPEX/Poseidon crossover in a region of strong internal tides, direct comparisons are made between altimeter and in situ measurements over a common 15 year period. The hourly buoy data are decimated every 9.9 day to emulate altimeter measurements. The altimeter and decimated buoy data are highly coherent at the aliased semidiurnal period (~60 day), and they agree well for the stationary semidiurnal internal tide. For the nonstationary internal tide, which consists of a significant annual cycle, the demodulated amplitude from the altimeter appears to be contaminated by nontidal signals. The demodulated amplitude from the decimated buoy data, on the other hand, is capable of resolving the temporal variability. This suggests the potential of mapping nonstationary internal tides from satellites.

Modeling shortwave radiative fluxes from satellites

During the last two decades, significant progress has been made in assessing the Earth Radiation Balance from satellite observations. Yet, satellite based estimates differ from each other and from those provided by numerical models. Major issues are related to quality of satellite observations, such as the frequent changes in satellite observing systems, degradation of sensors, restricted spectral intervals and viewing geometry of sensors, and changes in the quality of atmospheric inputs that drive the inference schemes. To reduce differences among the satellite based estimates requires, among others, updates to inference schemes so that most recent auxiliary information can be fully utilized. This paper reports on improvements introduced to a methodology developed at the University of Maryland to estimate shortwave (SW) radiative fluxes within the atmosphere system from satellite observations, the implementation of the approach with newly available auxiliary information, evaluation of the downwelling SW flux against ground observations, and comparison with independent satellite methods and numerical models. Specifically, introduced are: new Narrow to Broadband (N/B) transformations and new Angular Distribution Models (ADM) for clear and cloudy sky that incorporate most recent land use classifications; improved aerosol treatment; separation of clouds by phase; improved sun‐earth geometry; and implementation at 0.5° spatial resolution at 3‐hourly intervals integrated to daily and monthly time scales. When compared to an earlier version of the model as implemented at 2.5° at global scale and against observations from the globally distributed Baseline Surface Radiation Network (BSRN) stations for a period of six years (at monthly time scale), the bias was reduced from 8.6 (4.6%) to −0.5 (0.3%) W/m2, the standard deviation from 16.6 (8.9%) to 14.5 (7.8%) W/m2while the correlation remained high at 0.98 in both cases. Evaluation was also done over oceanic sites as available from the Pilot Research Moored Array in the Tropical Atlantic (PIRATA) moorings and from the Tropical Atmosphere Ocean/Triangle Trans‐Ocean Buoy Network (TAO/TRITON) moorings in the tropical Pacific Ocean. Overall, results over oceans were not as good as over land for all the satellite retrievals compared in this study.

2010년 4월 TAO 해양관측부이 시스템에 관한 탐사보고

Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON) Array is the series of buoys for the international ocean research project, which is mostly supported by National Ocean and Atmosphere Administration (NOAA) and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). We can determine the effect of the equatorial and Pacific Ocean conditions on global climate change from buoy array measurement data. The TAO/TRITON array comprises around 70 measurement buoys from 10° north to 10° south in the tropics and between Galpagos and New Guinea. NOAA maintains ATLAS buoys in the central and eastern Pacific between 165°E and 95°W, and JAMSTEC maintains the 12 buoys in the western Pacific along 137°E, 147°E, and 156oE. The KA-10-03 cruise excursion provided us with a good opportunity to obtain knowledge on oceanic buoy operation and maintenance. Further, we learned advanced techniques and know-how on buoy operation and maintenance. Once we are confident with our buoy management and maintenance techniques, both KORDI and NOAA technicians may be able to help each other when needed and share available resources.

Pausing of the ENSO Cycle: A Case Study from 1998 to 2002

Abstract The heat balance of the surface mixed layer is analyzed at the eastern equatorial Pacific Ocean (0°, 140°W) in order to examine the transition from the 1998 La Niña to the 2002 El Niño. The data used are observations from the Tropical Atmosphere Ocean/Triangle Trans-Ocean Buoy Network (TAO/TRITON). Results show that interannual variation of eddy heat flux due to tropical instability waves slows the transition from La Niña to El Niño. Previous studies have described this slow transition as a pausing period of the ENSO cycle; that is, La Niña lingers and El Niño does not immediately appear despite a deepened thermocline. Heat balance analysis shows that the vertical heat advection anomaly and surface heat flux anomaly warm the mixed layer from 1999 to 2002. These warming anomalies cause the rise of the mixed layer temperature anomaly in the transition from La Niña to El Niño. In contrast, a cooling anomaly of the horizontal heat advection reduces the warming anomaly and slows down the transition from La Niña to El Niño. In horizontal heat advection terms, the eddy heat flux anomaly significantly contributes to the cooling anomaly associated with weakened variability in the 14–50-day-period band, that is, weakened tropical instability waves. During the transition from La Niña to El Niño, the meridional shear between the South Equatorial Current (SEC) and North Equatorial Counter Current is weakened because of the eastward current anomaly at the equator (i.e., weakened SEC) associated with relaxing trade winds. Weakened shear would suppress tropical instability waves. The results presented here suggest that the synoptic-scale processes work effectively at the basin scale to slow down the transition from La Niña to El Niño.

Impact of Ocean Observation Systems on Ocean Analysis and Seasonal Forecasts

Abstract The relative merits of the Tropical Atmosphere–Ocean (TAO)/Triangle Trans-Ocean Buoy Network (TAO/TRITON) and Pilot Research Moored Array in the Tropical Atlantic mooring networks, the Voluntary Observing Ship (VOS) expendable bathythermograph (XBT) network, and the Argo float network are evaluated through their impact on ocean analyses and seasonal forecast skill. An ocean analysis is performed in which all available data are assimilated. In two additional experiments the moorings and the VOS datasets are withheld from the assimilation. To estimate the impact on seasonal forecast skill, the set of ocean analyses is then used to initialize a corresponding set of coupled ocean–atmosphere model forecasts. A further set of experiments is conducted to assess the impact of the more recent Argo array. A key parameter for seasonal forecast initialization is the depth of the thermocline in the tropical Pacific. This depth is quite similar in all of the experiments that involve data assimilation, but withdrawing the TAO data has a bigger effect than withdrawing XBT data, especially in the eastern half of the basin. The forecasts mainly indicate that the TAO/TRITON in situ temperature observations are essential to obtain optimum forecast skill. They are best combined with XBT, however, because this results in better predictions for the west Pacific. Furthermore, the XBTs play an important role in the North Atlantic. The ocean data assimilation performs less well in the tropical Atlantic. This may be partly a result of not having adequate observations of salinity.

The frontal area at the eastern edge of the western equatorial Pacific warm pool in April 2001

The western part of the equatorial Pacific Ocean is characterized, on average, by a relatively warm, fresh, and oligotrophic near‐surface water mass, the warm pool. On its eastern side the warm pool joins cooler, saltier, and richer waters from the equatorial upwelling. Previous works have shown that the boundary between these two water masses is highly variable in zonal location and structure, depending on large‐scale climatic conditions and/or local atmospheric forcing. This paper reports results from an oceanographic cruise carried out in April 2001, dedicated to the study of that boundary. By combining physical and biogeochemical data, the frontal area could unambiguously be found close to 157.5°E, in the far‐western equatorial Pacific, in accordance with La Niña climatic conditions. Some characteristics of the frontal zone were similar to the scarce previous observations: a sharp pCO2 step of about 40 ppm and a variation of NO3 concentration from about 1 μM to complete depletion. Other features were not previously reported, particularly the unexpected lack of a noticeable surface salinity front. Additional data from the Tropical Atmosphere‐Ocean/Triangle Trans‐Ocean Buoy Network (TAO/TRITON) moorings array provide a tentative explanation for that lack of salinity gradient: It appears that at the time of our observations the eastern part of the warm pool presented anomalously high surface salinity, about 0.5 above normal. The local evaporation‐precipitation budget did not explain this high salinity. Rather, it was associated with an anomalous northward extension of the South Pacific high‐salinity tongue in the upper thermocline.

In situ validation of Tropical Rainfall Measuring Mission microwave sea surface temperatures

We present a validation study of sea surface temperature (SST) retrievals from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). TMI SSTs are calculated using a radiative transfer‐based retrieval algorithm, which precisely accounts for SST and wind effects on surface emissivity as well as atmospheric effects on brightness temperatures. TMI SSTs are compared to 4 years of the National Data Buoy Center, Tropical Atmosphere Ocean/Triangle Trans‐Ocean Buoy Network (TAO/TRITON), and Pilot Research Moored Array in the Tropical Atlantic (PIRATA) moored buoy in situ SSTs. The microwave SSTs are shown to have a mean bias of −0.07°C and a standard deviation of 0.57°C when compared to the TAO/TRITON and PIRATA SSTs. A discussion of time series and dependencies of the accuracy of the TMI SSTs in the presence of varying wind, cloud, and water vapor for each of the buoy arrays is presented. TRMM's precessing equatorial orbit allows the diurnal variability to be determined, revealing midafternoon warming of the surface layer at wind speeds less than 6 m s−1. Low‐wind TAO/TRITON collocations show diurnal warming in both the TMI and buoy retrievals, with TMI's diurnal peak larger and 1 hour before the buoy peak. This decoupling of the skin‐bulk SSTs results in larger standard deviations for daytime low‐wind situations. This result has direct implications for future in situ validation studies, in situ‐based regression algorithms, and future blended infrared/microwave/in situ SST products.