More high-quality, in situ observations of essential marine variables are needed over the seasonal ice zone to better understand Arctic (or Antarctic) weather, climate, and ecosystems. To better assess the potential for arrays of uncrewed surface vehicles (USVs) to provide such observations, five wind-driven and solar-powered saildrones were sailed into the Chukchi and Beaufort Seas following the 2019 seasonal retreat of sea ice. They were equipped to observe the surface oceanic and atmospheric variables required to estimate air-sea fluxes of heat, momentum and carbon dioxide. Some of these variables were made available to weather forecast centers in real time. Our objective here is to analyze the effectiveness of existing remote ice navigation products and highlight the challenges and opportunities for improving remote ice navigation strategies with USVs. We examine the sources of navigational sea-ice distribution information based on post-mission tabulation of the sea-ice conditions encountered by the vehicles. The satellite-based ice-concentration analyses consulted during the mission exhibited large disagreements when the sea ice was retreating fastest (e.g., the 10% concentration contours differed between analyses by up to ∼175 km). Attempts to use saildrone observations to detect the ice edge revealed that in situ temperature and salinity measurements varied sufficiently in ice bands and open water that it is difficult to use these variables alone as a reliable ice-edge indicator. Devising robust strategies for remote ice zone navigation may depend on developing the capability to recognize sea ice and initiate navigational maneuvers with cameras and processing capability onboard the vehicles.

The tropical Pacific moored-buoy array spacing was based on wind coherence scales observed from low-lying islands in the western-central tropical Pacific. Since the array was deployed across the full basin in the mid-1990s, winds from the array have proven critical to accurately monitoring for decadal-scale changes in tropical Pacific winds and identifying spurious trends in wind analysis products used to monitor for long-term change. The array observations have also greatly advanced our ability to diagnostically model (hindcast) and thereby better understand the observed development of central Pacific sea surface temperature anomaly development associated with El Niño and La Niña events, although the eastern equatorial Pacific is not yet accurately hindcast. The original array-design assumptions that the statistics calculated from the western-central Pacific island records are representative of open-ocean conditions and other regions of the tropical Pacific have not been thoroughly reexamined. We revisit these assumptions using the basinwide wind observations provided by the array and find that key wind statistics change across the tropical Pacific basin in ways that could not be determined from the original island wind study. The island results provided a best-case answer for mooring zonal spacing with minimally redundant coherence between adjacent buoys. Buoy-observed meridional coherence scales are longer than determined from the islands. Enhanced zonal sampling east of 140°W and west of 180° is needed to obtain minimal redundancy (optimal spacing). Reduced meridional sampling could still yield minimal redundancy for wind and wind stress fields over the ocean waveguide.

This chapter aims to illuminate the capabilities of naval forces across the African continent. It focuses on historical development, capabilities, and the role of these forces in both the regional and international contexts. African navies comprise an assortment of forces as diverse as the continental states themselves. Based on current deployment, logistics, and maintenance capabilities, they are essentially coastal patrol forces. At independence, most African states possessed a navy consisting of a small number of platforms transferred from the respective colonial power. African navies are faced with a multitude of problems that few have been able to overcome. The most salient problems include shortages of skilled manpower, lack of training, organizational difficulties, poor logistics, undeveloped infrastructures, and maintenance problems. South Africa has an established, tested navy. Its forces are well trained and have benefited from a long history rooted in the British naval tradition. The Simonstown agreement set the stage for joint cooperation between South African and British navies.

The tropical Pacific is a major natural source of CO2 to the atmosphere and contributor to global air‐sea carbon flux variability. High time‐resolution wind and CO2 measurements from equatorial Pacific moorings reveal the primary factor controlling mooring‐observed flux variability to be near‐surface wind variability, above CO2 variability, in this region over the last 10 years. The analysis product winds used most widely in previous calculations of basin‐scale carbon flux are compared with mooring winds and found to exhibit significant differences in mean, variability, and trend. Earth system model calculations are in basic agreement with the mooring results and used to estimate effects of wind uncertainty on our knowledge of regional air‐sea carbon exchange. Results show that NCEP1 and NCEP2 winds contain biases large enough to obscure the interannual variability of CO2 flux (RMSE ≈ σ) and cause spurious 25‐year (1992–2016) trend components in equatorial Pacific carbon flux of 0.038–0.039 and 0.016–0.021 Pg C yr−1 per decade, respectively. These spurious trends act to reduce by up to 50% the 25‐year trend in equatorial Pacific carbon flux simulated by the Earth system model under increasing atmospheric CO2 concentration. The Cross‐Calibrated‐Multi‐Platform wind product tracks observed variability of equatorial Pacific wind better (interannual RMSE ≈ 0.4σ) than the NCEP reanalyses when site sampled at mooring locations yet still causes a spurious regional trend (0.03 Pg C yr−1 per decade) that masks 40% of the simulated 25‐year trend in carbon flux. The mooring observations are fundamental to identifying the limitations of current wind products to characterizing long‐term trends and understanding air‐sea carbon exchange.

The fundamental importance of near-equatorial zonal wind stress in the evolution of the tropical Pacific Ocean's seasonal cycle and El Nino-Southern Oscillation (ENSO) events is well known. It has been two decades since the TAO/TRITON buoy array was deployed, in part to provide accurate surface wind observations across the Pacific waveguide. It is timely to revisit the impact of TAO/TRITON winds on our ability to simulate and thereby understand the evolution of sea surface temperature (SST) in this region. This work shows that forced ocean model simulations of SST anomalies (SSTAs) during the periods with a reasonably high buoy data return rate can reproduce the major elements of SSTA variability during ENSO events using a wind stress field computed from TAO/TRITON observations only. This demonstrates that the buoy array usefully fulfills its waveguide-wind-measurement purpose. Comparison of several reanalysis wind fields commonly used in recent ENSO studies with the TAO/TRITON observations reveals substantial biases in the reanalyses that cause substantial errors in the variability and trends of the reanalysis-forced SST simulations. In particular, the negative trend in ERA-Interim is much larger and the NCEP-NCAR Reanalysis-1 and NCEP-DOE Reanalysis-2 variability much less than seen in the TAO/TRITON wind observations. There are also mean biases. Thus, even with the TAO/TRITON observations available for assimilation into these wind products, there remain oceanically important differences. The reanalyses would be much more useful for ENSO and tropical Pacific climate change study if they would more effectively assimilate the TAO/TRITON observations.

The unexpected halt of warm sea surface temperature anomaly (SSTA) growth in 2014 and development of a major El Nino in 2015 has drawn attention to our ability to understand and predict El Nino development. Wind stress-forced ocean model studies have satisfactorily reproduced observed equatorial Pacific SSTAs during periods when data return from the TAO/TRITON buoy network was high. Unfortunately, TAO/TRITON data return in 2014 was poor. To study 2014 SSTA development, the observed wind gaps must be filled. The hypothesis that subseasonal wind events provided the dominant driver of observed waveguide SSTA development in 2014 and 2015 is used along with the available buoy winds to construct an oceanic waveguide-wide surface stress field of westerly wind events (WWEs) and easterly wind surges (EWSs). It is found that the observed Nino-3.4 SSTA development in 2014 and 2015 can thereby be reproduced satisfactorily. Previous 2014 studies used other wind fields and reached differing conclusions about the importance of WWEs and EWSs. Experiment results herein help explain these inconsistencies, and clarify the relative importance of WWEs and EWSs. It is found that the springtime surplus of WWEs and summertime balance between WWEs and EWSs (yielding small net wind stress anomaly) accounts for the early development and midyear reversal of El Nino-like SSTA development in 2014. Astrong abundance of WWEs in 2015 accounts for the rapid SSTA warming observed then. Accurately forecasting equatorial Pacific SSTA in years like 2014 and 2015 may require learning to predict WWE and EWS occurrence characteristics.

El Niño-Southern Oscillation (ENSO) seasonal temperature and precipitation anomaly associations provide a useful basis for statistical seasonal weather forecasting in the seasons and regions where linkages between the tropical Pacific anomaly state and seasonal weather conditions are sufficiently strong in amplitude and consistent in character from one event to another (“robust”). Robust El Niño seasonal weather associations occur in boreal winter in many affected regions worldwide, when El Niño events reach peak amplitude in the tropical Pacific.

El Nino-Southern Oscillation (ENSO) events are associated with particular seasonal weather anomalies in many regions around the planet. When the statistical links are sufficiently strong, ENSO state information can provide useful seasonal forecasts with varying lead times. However, using conventional sea surface temperature or sea level pressure indices to characterize ENSO state leads to many instances of limited forecast skill (e.g., years identified as El Nino or La Nina with weather anomalies unlike the average), even in regions where there is considerable ENSO-associated anomaly, on average. Using outgoing longwave radiation (OLR) conditions to characterize ENSO state identifies a subset of the conventional ENSO years, called OLR El Nino and OLR La Nina years herein. Treating the OLR-identified subset of years differently can both usefully strengthen the level of statistical significance in the average (composite) and also greatly reduce the year-to-year deviations in the composite precipitation anomalies. On average, over most of the planet, the non-OLR El Nino and non-OLR La Nina years have much more limited statistical utility for precipitation. The OLR El Nino and OLR La Nina indices typically identify years in time to be of use to boreal wintertime and later seasonal forecasting efforts, meaning that paying attention to tropical Pacific OLR conditions may offer more than just a diagnostic tool. Understanding better how large-scale environmental conditions during ENSO events determine OLR behavior (and deep atmospheric convection) will lead to improved seasonal precipitation forecasts for many areas.

Extremes of the El Niño-Southern Oscillation (ENSO) are known to have various socio-economic impacts, including effects on several Pacific fisheries. The 137-year-long record of Darwin sea-level pressure offers a uniquely long-term perspective on ENSO and provides important insight into various aspects of interannual to century-scale variability that affects these fisheries. One particular issue of interest is whether there is a centennial-scale (or longer) trend that can be expected to alter the future distributions of these fisheries. Since most tropical Pacific fishery records are no longer than a few decades, another issue is the extent to which trends over these recent decades are a good basis for detecting the presence of long-term (e.g., centennial-scale) deterministic changes, and perhaps thereby projecting future conditions. We find that the full 137-yr trend cannot be distinguished from zero with 95% confidence, and also that the ENSO variance in recent decades is very similar to that of the early decades of the record, suggesting that ENSO has not fundamentally changed over the period of large increase in atmospheric CO2. However, the strong multi-decadal variability in ENSO is reflected in decades with quite different levels of ENSO effects on the ecosystem. Many multi-decadal subsets of the full record have statistically significant trends, using standard analysis techniques. These multi-decadal trends are not; however, representative of the record-length trend, nor are they a useful basis for projecting conditions in subsequent decades. Trend statistical significance is not a robust foundation for speculation about the future. We illustrate how the difficulties involved in determining whether a trend is statistically significant or not mean that, even after careful consideration, an unexpectedly large number of trends may reach standard statistical significance levels over the time spans for which many newer records are available, but still not continue into future decades or be indicative of deterministic changes to the system. Analysis of the Southern Oscillation Index, another common ENSO index, but one that has been directly measured for fewer years than has Darwin, yields similar results.

The processes responsible for the onset of La Nina events have not received the same attention as those responsible for the onset of El Nino events, for which westerly wind events (WWEs) in the tropical Pacific have been identified as important contributors. Results here show that synoptic-scale surface easterly wind surges (EWSs) play an important role in the onset of La Nina events, akin to the role ofWWEsin the onset of El Nino events. It is found that EWSs are a substantial component of zonal wind stress variance along the equatorial Pacific. Using reanalysis wind stress fields, validated against buoy measurements, 340 EWS events are identified between 1986 and 2012. Their distributions in space, time, and El Nino-Southern Oscillation (ENSO) state are described. About 150 EWSs occur during ENSO-neutral conditions, during the months associated with La Nina initiation and growth (April-December). Composites of changes in sea surface temperature anomaly (SSTA) following these similar to 150 events show statistically significant cooling (0.1 degrees-0.4 degrees C) along the oceanic waveguide that persists for 2-3 months following the EWSs. Experiments with EWS forcing of an ocean general circulation model show SSTA patterns like those in the observations. It is suggested that EWSs play an important role in the onset of La Nina waveguide surface cooling and deserve additional study.

It is well known that interannual extremes in the rate of change of atmospheric CO2 are strongly influenced by the occurrence of El Niño-Southern Oscillation (ENSO) events. Qian et al. presented ENSO composites of atmospheric CO2 changes. We show that their composites do not reflect the atmospheric changes that are most relevant to understanding the role of ENSO on atmospheric CO2 variability. We present here composites of atmospheric CO2 change that differ markedly from those of Qian et al., and reveal previously unreported asymmetries between the effects on the global carbon system of El Niño and La Niña events. The calendar-year timing differs; La Niña changes in atmospheric CO2 typically occur primarily over September–May, while El Niño changes occur primarily over December–August. And the net concentration change is quite different; La Niña changes are about half the size of El Niño changes. These results illustrate new aspects of the ENSO/global carbon budget interaction and provide useful global-scale benchmarks for the evaluation of Earth System Model studies of the carbon system.

Westerly wind events (WWEs) have previously been shown to initiate equatorial Pacific waveguide warming. The relationship between WWEs and Madden-Julian oscillation (MJO) activity, as well as the role of MJO events in initiating waveguide warming, is reconsidered here over the 1986-2010 period. WWEs are identified in observations of near-surface zonal winds using an objective scheme. MJO events are defined using a widely used index, and 64 are identified that occur when the El Nino-Southern Oscillation (ENSO) is in its neutral state. Of these MJO events, 43 have one or more embedded WWEs and 21 do not. The evolution of sea surface temperature anomaly over the equatorial Pacific waveguide following the westerly surface wind phase of the MJO over the western equatorial Pacific is examined. Waveguide warming is found for the MJO with WWE events in similar magnitudes as following the WWEs not embedded in an MJO. There is very little statistically significant waveguide warming following MJO events that do not contain an embedded WWE. The observed SST anomaly changes are well reproduced in an ocean general circulation model forced with the respective composite wind stress anomalies. Further, it is found that the occurrence of an MJO event does not significantly affect the likelihood that a WWE will occur. These results extend and confirm the earlier results of Vecchi with a near doubling of the period of study. It is suggested that understanding the sources and predictability of tropical Pacific westerly wind events remains essential to improving predictions of the onset of El Nino events.

The goal of this paper is to provide information on the sea level and upper ocean temperature variability and trends in the Cook Islands region within a global context. Oceanic fisheries variability and change take place within the physical environment. Because the state of the historical data set is not as would be desired, we begin with some review of data distribution issues. We provide some new results from the Cook Islands region but draw upon previous work for information about the global and ocean-basin scale context. There are clear trends over recent decades in sea level and, generally, in upper ocean temperature, but there is also substantial interannual and interdecadal variability, which are larger locally than globally. Because of this variability, it is not possible to say if recent Cook Islands regional trends are representative of longer-term trends, or if longer-term trends have increased recently. Trends in the Cook Islands region over the last four decades are ~0.1–0.3 °C per decade in near surface temperature and ~2–3 cm sea level per decade.

Several lines of evidence show that climatic variation and global warming can have a major effect on fisheries production and replenishment. To prevent overfishing and rebuild overfished stocks under changing and uncertain environmental conditions, new research partnerships between fisheries scientists and climate change experts are required. The International Workshop on Climate and Oceanic Fisheries held in Rarotonga, Cook Islands, 3–5 October 2011, brought representatives from these disciplines together to consider the effects of climate variability and change on oceanic fisheries, the tools and strategies required for identifying potential impacts on oceanic fisheries, and the priority adaptations for sustaining future harvests, especially in the Pacific Ocean. Recommendations made by the workshop included (1) development and implementation of sustainable management measures for fisheries; (2) long-term commitment to monitoring necessary to assess stock status and to conduct integrated ecosystem assessments; (3) process oriented research to evaluate the potential of marine species for adaptation to a changing ocean environment; (4) provision of improved national meteorological and hydrological services to fisheries agencies, enterprises and communities; (5) continuing communication of potential impacts and adaptation strategies to stakeholders to reduce the threats to oceanic fisheries and capitalise on opportunities; and (6) continued collaborative efforts between meteorological, oceanographic, biological and fisheries researchers and management agencies to better monitor and understand the impacts of short-term variability and longer-term change on oceanic fisheries.

This study shows that, since 1979 when outgoing longwave radiation (OLR) observations became reliably available, most of the useful U. S. seasonal weather impact of El Nino events is associated with the few events identified by the behavior of outgoing longwave radiation (OLR) over the eastern equatorial Pacific ("OLR-El Nino events"). These events produce composite seasonal regional weather anomalies that are 95% statistically significant and robust (associated with almost all events). Results also show that there are very few statistically significant seasonal weather anomalies, even at the 80% level, associated with the non-OLR-El Nino events. A major enhancement of statistical seasonal forecasting skill over the contiguous United States appears possible by incorporating these results. It is essential to respect that not all events commonly labeled as El Nino events lead to statistically useful U.S. seasonal forecast skill.

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper, physical modelling of the synchrotron bump using multiplecomponents. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.

This study aims at evaluating effects of the mesoscale variability on the expected accuracy of reconstruction of temperature, salinity, and velocities from the Argo measurements and trajectories. For this purpose, an idealized observing system with profiling floats is simulated in a high-resolution ocean model of the North Atlantic set up to produce annual mean hydrography and circulation. The simulations with and without mesoscale variability are compared, and the effects of the time mean and mesoscale eddy-induced advection are effectively separated and investigated. The results demonstrate several effects of mesoscale eddies on the expected accuracy of the Argo-based reconstructions of temperature, salinity, and horizontal velocities. In most of the domain, the eddies help to achieve uniform spatial coverage. The effects of eddy advection on reconstruction errors are, however, complex but moderate in most of the domain. High-frequency variability in temperature and salinity leads to enhancement of reconstruction errors, especially if the sampling is carried out for only a few years. The reconstruction of horizontal velocities from trajectories of the profiling floats is capable of detecting multiple zonal jets which have been observed already. The reconstruction of the meridional velocities is significantly less reliable, primarily due to a small signal-to-noise ratio in the in the interior of domain.

This chapter contains sections titled: Introduction Sustained, Systematic Observing Systems (Existing Capabilities) Development of Improved Observing Systems (New Capabilities) Summary References