Western Tropical Pacific Ocean Research Articles

New Data on Chelidonura Amoena Bergh, 1905 (Opisthobranchia: Cephalaspidea: Aglajidae)

Chelidonura amoena Bergh, 1905 is redescribed, principally on material from Australia. The single extant type specimen is designated as lectotype. Considerable intraspecific colour variation is evident, with that relating to the caudal lobes being greatest. The variation in coloration and shape observed in one specimen from Belau lies outside those described for C. amoena and we believe it could be explained as the product of hybridisation with C. electra Rudman, 1970. Aggregation for the purpose of breeding is shown to be normal for C. amoena. The collection data and observations indicate C. amoena is widely distributed in the tropical western Pacific and eastern Indian Oceans with disparate limits on the eastern and western coasts of the Australian continent.

Salinity variability in the surface layer of the tropical western Pacific Ocean

Observations of surface layer salinity and temperature, rainfall, wind and upper ocean currents from two surveys during the Tropical Ocean Global Atmosphere‐Coupled Ocean‐Atmosphere Response Experiment are presented. The surveys covered a region of 25×25 n. mi (46.3×46.3 km) with hydrographic sections of 5 n. mi (9.3 km) separation, using a Seasoar towed conductivity‐temperature‐depth profiler. One survey was dominated by the presence of several rain‐induced patches of low‐salinity water with slightly reduced temperature. These patches extended to the bottom of the mixed layer, which at the time, was 20–30 m deep, and appeared to be the result of convection driven by their reduced temperature. Below the mixed layer was a 15 to 20 m thick barrier layer. By distributing the freshwater over the mixed layer almost instantly, the convecting patches appeared to contribute to the maintenance of the barrier layer. This survey is typical for conditions found during most of the observation period. The second survey was dominated by a salinity front and advection of low‐salinity water with the large‐scale westerly wind that prevailed at the time. A single event of very heavy rain produced a shallow lens of freshened water; but the reduction in salinity was so strong that the associated cooling was insufficient to initiate convection. No barrier layer was seen ahead of the front but the observations indicate the development of a barrier layer after the passage of the front. The work demonstrates the difficulties in establishing a freshwater budget for the tropical ocean. Ship borne rain gauge measurements, even though becoming more accurate, seem not to be representative for an area much beyond a few kilometers or less. Sometimes the surface salinity distribution shows better visual correlation with the wind gust pattern than with the rainfall distribution, indicating that the wind gusts associated with atmospheric convection cells are less intermittent and more coherent in space than the rain.

Cloud albedo feedback and the super greenhouse effect in a global coupled GCM

Two competing cloud-radiative feedbacks identified in previous studies i.e., cloud albedo feedback and the super greenhouse effect, are examined in a sensitivity study with a global coupled ocean-atmosphere general circulation model. Cloud albedo feedback is strengthened in a sensitivity experiment by lowering the sea-surface temperature (SST) threshold in the specified cloud albedo feedback scheme. This simple parameterization requires coincident warm SSTs and deep convection for upper-level cloud albedos to increase. The enhanced cloud albedo feedback in the sensitivity experiment results in decreased maximum values of SST and cooler surface temperatures over most areas of the planet. There is also a cooling of the tropical troposphere with attendant global changes of atmospheric circulation reminiscent of those observed during La Nina or cold events in the Southern Oscillation. The strengthening of the cloud albedo feedback only occurs over warm tropical oceans (e.g., the western Pacific warm pool), where there is increased albedo, decreased absorbed solar radiation at the surface, stronger surface westerlies, enhanced westward currents, lower temperatures, and decreased precipitation and evaporation. However, the weakened convection over the tropical western Pacific Ocean alters the large-scale circulation in the tropics such that there is increased upper-level divergence over tropical land areas and the tropical Indian Ocean. This results in increased precipitation in those regions and intensified monsoonal regimes. The enhanced precipitation over tropical land areas produces increased clouds and albedo and wetter and cooler land surfaces. These additional contributions to decreased absorbed solar input at the surface combine with similar changes over the tropical oceans to produce the global cooling associated with the stronger cloud albedo feedback. Increased low-level moisture convergence and precipitation over the tropical Indian Ocean enhance slightly the super greenhouse effect there. But the stronger cloud albedo feedback is still the dominant effect, although cooling of SSTs in that region is less than in the tropical western Pacific Ocean. The sensitivity experiment demonstrates how a regional change of radiative forcing is quickly transmitted globally through a combination of radiative and dynamical processes in the coupled model. This study points to the uncertainties involved with the parameterization of cloud albedo and the major implications of such parameterizations concerning the maximum values of SST, global climate sensitivity, and climate change.

ENSO Signals in Global Upper-Ocean Temperature

The time-space evolution of the El Niño-Southern Oscillation in sea surface temperature (SST) and heat storage of the upper 400 m (HS400) for the Pacific, Indian, and Atlantic Oceans is investigated for 13 years (1979–1991). EOF and rotated EOF (Varimax or VRX) analyses are performed using the time series of normalized anomalies for each ocean separately and then for the global ocean. In the Pacific and Indian Oceans, the two dominant EOF modes for both SST and H5400 are associated with ENSO. For SST they account for 49% of the total variance in each mean, while for H5400 they account for over 35% of the total variance in each ocean. In the Pacific Ocean, the first EOF modes for SST and HS400 display peak values during spring-summer of 1983 and 1987. They are characterized by maximum positive loadings (or warmer temperature) in the eastern and central Pacific Ocean straddling the equator. These modes represent the peak phase of El Niño off the west coast of South America. The second modes for SST and HS400 are precursor modes with maximum positive loadings in the western and central Pacific Ocean both on and off the equator. The peak values in HS400 second mode lead peak values in HS400 first mode by 6–9 months. Taken together, SST and HS400 first two modes are associated with slow equatorial and eastward propagation of ENSO signals, more clearly though in HS400 than in the SST. In the Indian Ocean, the dominant EOF modes for SST display peak values in summer-fall of 1983 and summer of 1987, while peak values for HS400 are found during fall of 1982 and summer of 1987. Corresponding positive SST loadings are found in the central Indian Ocean while positive HS400 loadings are found in the western Indian Ocean. Maximum values are both straddling the equator. As in the Pacific Ocean, the second EOF modes for SST and HS400 in the Indian Ocean are precursor modes to the first modes. They occur 9–15 months earlier, with warmer SST in the Arabian Sea, colder SST northwest of Australia, and colder H5400 in the vicinity of the boreal winter ITCZ. Taken together, thew two modes suggest a slow equatorial and eastward propagation of ENSO signals in SST and HS400, very similar to those in the Pacific Ocean. This propagation can he seen extending eastward south of Indonesia and on into the Timor Sea. There the anomalies have the same sign as the anomalies found in the Philippine and Coral Seas in the western tropical Pacific Ocean during the peak phase of El Niño. In the Atlantic Ocean, ENSO is represented by the third SST VRX mode but not at all in HS400. As such, the Atlantic ENSO signal at the equator is a passive response to a globally perturbed atmosphere. It lags by approximately 18 months the dominant Pacific ENSO mode.

Historical dictionary of Guam and Micronesia

The book, in dictionary form, provides basic reference material on Micronesia, a region encompassing a vast area of the tropical western Pacific Ocean. Micronesia, from the Greek mikros (small), and nesos (island), is one of the three major geographical regions of the Pacific, or Oceania. It includes the Mariana, Caroline, Marshall, and Gilbert islands and the island nation of Nauru. In all there are 2,106 islands, Guam being the largest and most populous. Intended for interested general readers as well as scholars, the book covers the history, culture, society, geography, and economy of the region, and includes information on prominent individuals, events, and institutions. It is the first book of its type on Micronesia. With maps, tables, and an extensive bibliography.

One‐ to two‐month oscillations in SSMI surface wind speed in western tropical Pacific Ocean

The 10‐m wind speed over the ocean can be estimated from microwave brightness temperature measurements recorded by the Special Sensor Microwave Imager (SSMI) instrument mounted on a polar‐orbiting spacecraft. Four‐year (1988–1991) time series of average daily 1° × 1° SSMI wind speeds were analyzed at selected sites in the western tropical Pacific Ocean. One‐ to two‐month period wind speed oscillations with amplitudes statistically significant at the 95% confidence level were observed near Kanton, Eniwetok, Guam, and Truk. This is the first report of such an oscillation in SSMI wind speeds.

Solar‐irradiance variations and regional precipitation fluctuations in the Western USA

AbstractChanges in total solar irradiance can be linked to changes in regional precipitation. A possible mechanism responsible for this linkage begins with the absorption of varying amounts of solar energy by the tropical oceans, which creates ocean temperature anomalies. These anomalies are then transported by major ocean currents to locations where the stored energy is released into the atmosphere, thereby altering atmospheric pressure and moisture patterns, which can ultimately affect regional precipitation.Correlation coefficients between annual differences in empirically modelled solar‐irradiance variations and annual State‐divisional precipitation in the USA for the period 1950–1988 were computed with lag times of 0 to 7 years. The most significant correlations occur in the Pacific North‐west, with a lag time of 4 years, which is approximately equal to the travel time of water within the Pacific gyre from the western tropical Pacific Ocean to the Gulf of Alaska. Precipitation in the Desert South‐west correlates significantly with solar irradiance lagged 3 and 5 years, which suggests a link with ocean‐water temperature anomalies transported by the Equatorial Counter Current as well as the North Pacific gyre. With the correlations obtained, droughts coincide with periods of negative irradiance differences (dry high‐pressure development), and wet periods coincide with periods of positive differences (moist low‐pressure development).

Low-Frequency Oscillations in Radiative-Convective Systems

Although eastward propagation has long been considered one of the essential features of the Madden-Julian waves, recent observations have revealed a stationary or quasi-stationary component in the oscillations, particularly in measures of the diabatic heating rate. Wave-CISK theories of the low-frequency oscillations have struggled to explain the observed period and vertical structure of the waves. On the other hand, theoretical and numerical studies have shown that low-frequency waves strongly resembling the observed oscillations can be excited by specified low-frequency oscillations of the convective heating. A problem with the latter set of theories is that the cause of the oscillatory heating has not been satisfactorily explained. It is proposed here that the observed low-frequency wave motions are the response to forcing by an essentially stationary, self-excited oscillating heat source that is produced by nonlinear interactions among radiation, cumulus convection, and the surface fluxes of sensible heat and moisture. Feedback of the large-scale motions on the latent heating is not required. Results from two very different one-dimensional models are presented to support this hypothesis. The physical processes included in the models are essentially the same, that is, radiation, cumulus convection, and the surface fluxes of sensible heat and moisture; the first model is highly simplified, however, while the second includes relatively sophisticated parameterizations of all the relevant physical processes. Results from both models show low-frequency oscillations of the latent heating, temperature, and moisture. Experiments show that the oscillations are favored by a warm sea surface and weak surface wind speeds, consistent with the observed conditions over the Indian Ocean and the tropical western Pacific Ocean.

Climatology and natural variability of the global hydrologic cycle in the GLA atmospheric general circulation model

Time average climatology and low‐frequency variabilities of the global hydrologic cycle (GHC) in the Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) were investigated in the present work. A 730‐day experiment was conducted with the GLA GCM forced by insolation, sea surface temperature, and ice‐snow undergoing climatological annual cycles. Influences of interactive soil moisture on time average climatology and natural variability of the GHC were also investigated by conducting 365‐day experiments with and without interactive soil moisture. Insolation, sea surface temperature, and ice‐snow were fixed at their July levels in the latter two experiments. Results show that the model's time average hydrologic cycle variables for July in all three experiments agree reasonably well with observations. Except in the case of precipitable water, the zonal average climates of the annual cycle experiment and the two perpetual July experiments are alike, i.e., their differences are within limits of the natural variability of the model's climate. Statistics of various components of the GHC, i.e., water vapor, evaporation, and precipitation, are significantly affected by the presence of interactive soil moisture. Even with fixed external conditions, the GHC exhibits a variety of low‐frequency natural variabilities. A long‐term trend is found in the principal empirical modes of variability of ground wetness, evaporation, and sensible heat. Dominant modes of variability of these quantities over land are physically consistent with one another and with land surface energy balance requirements. The dominant empirical modes of ground wetness variability in the annual cycle and perpetual July experiments have similar spatial patterns. The dominant mode of precipitation variability is found to be closely related to organized convection over the tropical western Pacific Ocean. The precipitation variability has timescales in the range of 2 to 3 months and can be identified with the stationary component of the Madden‐Julian Oscillation. The precipitation mode is not sensitive to the presence of interactive soil moisture but is closely linked to both the rotational and divergent components of atmospheric moisture transport. The present results indicate that globally coherent natural variability of the GHC in the GLA GCM has two basic timescales in the absence of annual cycles of external forcings: a long‐term trend associated with atmosphere‐soil moisture interaction which affects the model atmosphere mostly over midlatitude continental regions and a large‐scale 2‐ to 3‐month variability associated with atmospheric moist processes over the western Pacific Ocean.

The effect of averaging on bulk estimates of heat and momentum fluxes for the tropical western Pacific Ocean

The magnitudes of bulk air‐sea surface flux estimates calculated using three temporal averaging methods were compared. The reference method is a simple average of fluxes computed from hourly values of bulk meteorological parameters termed the sampling method (SM). In contrast, the scaler averaging method (SAM) computes the average flux from the average of the bulk data; thus it ignores correlations between variables. The vector averaging method (VAM) is similar to the SAM but uses the magnitude of the average wind vector rather than the average magnitude of the hourly wind vectors. The data used in this study were collected during the Tropical Ocean and Global Atmospheric pilot cruise of the R/V Wecoma in the equatorial Pacific Ocean near 0°N, 145°E from February 17 to March 10,1990. The ratios of the SAM and VAM values relative to the SM values were studied as a function of averaging periods from 2–72 hours. The ratios vary little for times exceeding 36 hours. For averaging periods of 72 hours, the SAM estimates of QE, QH, τx, and τy were 102%, 61%, 21%, and 69% of the SM estimates, respectively; the VAM ratios were even lower. These results suggest that air‐sea surface sealer fluxes and stress components computed from monthly, weekly, and even daily averaged bulk meteorological parameters can be seriously in error in equatorial, temporally variable wind regimes.

The development of a satellite‐based insolation model for the tropical western Pacific Ocean

AbstractConcurrent pyranometer and GMS (Japanese Geostationary Meteorological Satellite) data were collected for the western tropical Pacific during a 21‐month period in 1987 and 1988. Data from 10 pyranometer stations in 1987 were used to build a satellite insolation model. Such processes as surface albedo, narrow band to broad band conversion, and depletion by water vapour and aerosols were taken into account. The model was then tested with an independent pyranometer data set comprising 9 months in 1988.Results show that aerosol depletion is site‐specific, with typical long‐term values ranging from 19·8 per cent of the extraterrestrial value for Kuala Lampur, to 4·8 per cent for Willis Island. Monthly insolation may be mapped over the oceanic regions of the study area assuming that the Willis Island aerosol depletion values apply. The model gave root‐mean‐square (RMS) errors of 14·08 W m−2 when tested against all monthly average pyranometer data for 1988. Corresponding RMS errors are 11·67 W m−2 when only Willis Island data are used. Sources of errors are discussed, as are suggestions for future research.

Uncertainties in Climatological Tropical Humidity Profiles: Some Implications for Estimating the Greenhouse Effect

Abstract The vertical profile of water vapor, the principal infrared-absorbing gas in the atmosphere, is an important factor in determining the energy balance of the climate system. This study examines uncertainties in calculating a climatologicai humidity profile: specifically one derived from radiosonde data representative of the moist and highly convective region over the western tropical Pacific Ocean. Uncertainties in the humidity data are large in conditions of low temperature or low humidity in the mid- and upper troposphere. Results derived from a single United States station (Koror) and from an average of four United States--operated stations (all near the equator west of the date line) yield nearly identical results. No humidity measurements are reported in fully the upper third of the troposphere. The implications of these uncertainties for determining the climatological humidity profile are quantitatively assessed by bracketing the range of plausible assumptions for unreported humidity to prod...

Determination of characteristic features of cloud liquid water from satellite microwave measurements

In this paper we present an algorithm for determining liquid water path (LWP) in clouds using satellite microwave measurements from the special sensor microwave/imager (SSM/I). This physically based algorithm is derived using the guidance of a 32‐stream plane‐parallel model of microwave radiative transfer in the cloudy atmosphere. Our investigation using both radiative transfer model and observed SSM/I data indicates that the retrieved LWP is sensitive to the emission temperature of the liquid water, to the presence of large hydrometeors, to the nonuniformity of the rainfall in the satellite field of view, and to the radiation from atmosphere and ocean. Therefore we have incorporated cloud temperature into our algorithm using ancillary infrared satellite data. To account for the effects of rainfall on the LWP retrievals, we use a threshold for the onset of precipitation to determine whether there is any precipitation in the satellite field of view. Two separate retrieval schemes are derived for non‐precipitating and precipitating clouds. A clear‐sky radiation scheme is developed to separate radiation of atmosphere and ocean from that of liquid water. This scheme could be easily tuned by observed microwave data so that the bias in LWP retrieval is minimized. This algorithm is indirectly validated by comparing retrieved values of LWP for clear versus cloudy situations. The retrievals are examined for regions in the tropical western Pacific Ocean, the North Atlantic Ocean, and the subtropical southeast Pacific Ocean. The retrievals obtained using our algorithm are also compared with simultaneous retrievals using other LWP algorithms described in the literature. The retrievals are compared for clear sky, liquid cloud only, cloud with ice, raining water cloud, and raining cloud with ice to assess and interpret the performance of the algorithms in each of these situations. The present algorithm is shown to perform consistently well in all three regions under all conditions. It is determined that features of our algorithm that results in more consistent global retrievals of LWP are inclusion of the tunable clear‐sky scheme, estimation of cloud temperature using satellite infrared radiances, and consideration of precipitation.

The 30–60-Day Convection Seesaw between the Tropical Indian and Western Pacific Oceans

Abstract The tropical Indian and western Pacific oceans are two prominent action centers for tropical 30–60-day convective variability. When convection is enhanced over the equatorial Indian Ocean, the tropical western Pacific often experiences an abnormal dry condition (phase I), whereas the development of the convection over the tropical western Pacific tends to be accompanied by suppressed convection in the equatorial Indian Ocean (phase II). This convection seesaw is a fundamental characteristic of the tropical 30–60-day oscillation. The seesaw is intimately associated with the activity of propagating low-frequency convective systems (LFCSs). Its formation process is season dependent. Typical boreal summer seesaw results from a time-lagged development of two systems: a western system that originates in the equatorial Indian Ocean and moves eastward and/or northward and an eastern system that develops in the western Pacific monsoon region and moves westward and/or northward. The boreal winter seesaw, o...

Poecilostomatoid Copepods associated with the Scleractinian coral Acropora in the tropical western Pacific Ocean

Nine new lichomolgid copepods, including two new genera, Ecphysarion and Unicispina, are described, all associated with various species of the scleractinian genus Acropora in New Caledonia, at Ceram and Obi in the Moluccas, and at Enewetak Atoll in the Marshall Islands: Schedomolgus idanus, S. majusculus, S. insignellus, S. exiliculus, Scyphuliger eumorphus, S. aristoides, Ecphysarion ampullulum, E. spinulatum, and Unicispina latigenitalis. New records are given for Ecphysarion lobophomm (Humes & Ho, 1968), comb. nov., Scyphuliger concavipes Humes, 1991, S. manifestus Humes, 1991, and S. tenuatus (Humes, 1990).

Climatic variability of temperature and humidity over the tropical western Pacific

The vertical structures of recent decadal‐scale trends of temperature and humidity over the tropical western Pacific Ocean are documented using daily data at 16 pressure levels (from the surface to 300 mbar) from four radiosonde stations. Both temperature and specific humidity have increased throughout the troposphere since the mid‐1970 's. The specific humidity increase is sufficiently large that relative humidity also shows positive trends at all tropospheric levels above the surface despite the warming trend. The specific humidity trend is greatest near the surface and decreases with height, whereas the temperature trend increases with height above the boundary layer. Specific humidity in the tropics is shown to be a sensitive indicator of long‐term climate change, because the vertical structure of the specific humidity trend (largest near the surface) is distinctly different from the vertical structure of the seasonal cycle or interannual variability of specific humidity variability, which exhibit peak amplitudes in mid‐troposphere. Thus short‐term climate variability of humidity is a poor proxy for long‐term climate change. Reproduction of the difference in vertical structures of long‐term and short‐term specific humidity fluctuations would provide a good test of the fidelity of model projections of climate change.

Influence of precipitating convection on the surface energy budget observed during a tropical ocean global atmosphere pilot cruise in the tropical western Pacific Ocean

A short‐term observational study of the surface energy budget of the equatorial western Pacific Ocean was conducted in preparation for the Tropical Ocean and Global Atmosphere program Coupled Ocean‐Atmosphere Response Experiment (TOGA COARE). Data were obtained between February 17 and March 10, 1990, during the TOGA pilot cruise of the R/V Wecoma near the equator and 147°E longitude. Analysis of the 443 hours of turbulent and radiative fluxes collected was focused on the influence of deep precipitating convection on the day‐to‐day variability of the surface energy budget. Partitioning the data series according to the degree of local convective activity allowed comparison of the surface energy budgets for various convective regimes. As was observed in the tropical Atlantic during the GARP Atlantic Tropical Experiment (GATE), the surface fluxes of sensible and latent heat were larger during periods influenced by deep precipitating convection. Moreover, the mechanisms by which convection affected these fluxes were similar to those described in the tropical Atlantic. Variations in the shortwave radiation caused by convective clouds and their by‐products were found to contribute even more than the surface fluxes to the day‐to‐day variability of the surface energy budget. It is concluded that the existence of convectively disturbed days had a significant impact on the surface energy budget for the entire cruise period as well as on the day‐to‐day variability within that period.

High‐frequency variability of Special Sensor Microwave/Imager derived wind speed and moisture during an intraseasonal oscillation

Special Sensor Microwave/Imager data are used to examine the day‐to‐day variability of wind speed and precipitable water during the passage of an intraseasonal oscillation. First, SSM/I precipitable water and wind speed algorithms are evaluated for the tropical western Pacific Ocean. The algorithm by Alishouse for retrieving precipitable water vapor retrieves precipitable water values that compare well with island radiosonde observations, but the wind speeds retrieved using the algorithm by Goodberlet et al. compare with buoy wind speeds only marginally. A revised wind speed algorithm, based on regression with buoy wind speeds, is derived for use in this region. During the intraseasonal oscillation, anomalously high values of precipitable water, with maximum amplitude at 10°S, accompany the movement of convection eastward. Anomalously high wind speeds are found to the west of the convection and accompany its movement east. Differences of up to 20% are found along 10°S between the means of daily latent heat flux and U*3 values and the 60‐day mean of these quantities. This implies that high frequency variability must be explicitly accounted for in diagnostics and modeling of air‐sea interaction in the western equatorial Pacific Ocean.

Subsurface chlorophyll maximum in the tropical and subtropical western Pacific Ocean: Vertical profiles of phytoplankton biomass and its relationship with chlorophylla and particulate organic carbon

Vertical distribution of phytoplankton biomass in terms of carbon content (PC) and its relationship with chlorophylla and particulate organic carbon (POC) were examined together with phytoplankton growth rates in the tropical and subtropical western Pacific in 1979, where a prominent subsurface chlorophyll maximum (SCM) developed between 65 and 150 m. Fluorescence microscopy combined with image analysis was used for measurement of cell volume which was converted to PC. The SCM coincided consistently with subsurface maximum of PC, and the SCM primarily reflected in situ accumulation of phytoplankton biomass. The PC:chlorophylla ratio decreased with depth; the ratio was 1.8 times, on average, higher in populations at the SCM compared to those near the surface. This increase in relative cellular chlorophylla along with depth accentuated the magnitude of the SCM. The PC:POC ratio was substantially lower near the surface, 0.17 on average, and increased sharply around the SCM, with a mean value of 0.53. Thus suspended particles around SCM were richer in phytoplankton than those in the upper layers. A major part of PC was contributed by autotrophic eukaryotes both near the surface and at the SCM, and prokaryotic picoplankton comprised a relatively small proportion (6.3 to 14.9%) of PC. The high phytoplankton biomass around the SCM was suggested to be ascribed to in-situ growth of phytoplankton.

Further FGGE Forecasts for Amazon Basin Rainfall

Abstract A series of experiments using real-data general circulation model integrations is performed to study the impact of remote tropical Pacific heating modifications upon the rainfall over the Amazon Basin. In one set of experiments, a heating term is added to the thermodynamic equation in the western tropical Pacific Ocean, and in the second set, the sea surface temperatures are cooled in the eastern Pacific Ocean. The rainfall of northern sections of South America decreases in the first set of experiments and increases in the second set of experiments. Examination of the circulation changes for the second set of experiments suggests that the remote links occur through equatorially trapped flow modifications, perhaps related to the east-west Walker cells, rather than through midlatitude teleconnections via Hadley cells. The time evolution of these patterns suggests them to be clearly relevant for medium range weather prediction in the tropics.