Marine Surface Wind Research Articles

EFFECT OF MONSOON PHENOMENON ON SEA SURFACE TEMPERATURES IN INDONESIAN THROUGHFLOW REGION AND SOUTHEAST INDIAN OCEAN

Indonesia is influenced by two types of monsoons, namely, the Asian and Australian monsoons. The differences in conditions occurring during these monsoon phenomena can affect sea surface temperatures (SSTs). This study aims to determine the effect of these monsoons on the SSTs in the southeast Indian Ocean and the Indonesian throughflow (ITF) region. SST and geostrophic current data obtained from Copernicus Marine Service and surface wind speed and direction data from the European Center for Medium-Range Weather Forecasts (ECMWF) from March 2019 to February 2020 were statistically and descriptively analyzed. Observational conductivity–temperature–depth (CTD) data obtained in December 2019 were used to identify statistical errors in the Copernicus Marine Service SST data. The results of the SST data verification show a 0.85°C RMSE and 0.6°C MAE; they are significantly correlated at 0.82 with a 95% confidence level. The results of this study generally show that geostrophic currents move to the east, and SST tends to be warmer during the Asian monsoon period than during the Australian monsoon period, which has a cooler SST (with geostrophic currents moving to the northwest). Specifically, the SST conditions in the ITF region and southeast Indian Ocean cool from the MAM period. This cooling period intensifies during the JJA period and subsides in the SON period. The Australian monsoon, which is dominant during the DJF period, causes warmer-than-average SST conditions in the northern part of Indonesia, particularly the northern part of the ITF.

Multimodel Ensemble Projections of Wave Climate in the Western North Pacific Using CMIP6 Marine Surface Winds

For decades, the western North Pacific (WNP) has been commonly indicated as a region with high vulnerability to oceanic and atmospheric hazards. This phenomenon can be observed through general circulation model (GCM) output from the Coupled Model Intercomparison Project (CMIP). The CMIP consists of a collection of ensemble data as well as marine surface winds for the projection of the wave climate. Wave climate projections based on the CMIP dataset are necessary for ocean studies, marine forecasts, and coastal development over the WNP region. Numerous studies with earlier phases of CMIP are abundant, but studies using CMIP6 as the recent dataset for wave projection is still limited. Thus, in this study, wave climate projections with WAVEWATCH III are conducted to investigate how wave characteristics in the WNP will have changed in 2050 and 2100 compared to those in 2000 with atmospheric forcings from CMIP6 marine surface winds. The wave model runs with a 0.5° × 0.5° spatial resolution in spherical coordinates and a 10-min time step. A total of eight GCMs from the CMIP6 dataset are used for the marine surface winds modelled over 3 h for 2050 and 2100. The simulated average wave characteristics for 2000 are validated with the ERA5 Reanalysis wave data showing good consistency. The wave characteristics in 2050 and 2100 show that significant decreases in wave height, a clockwise shift in wave direction, and the mean wave period becomes shorter relative to those in 2000.

EVALUATION AND BIAS CORRECTION OF MARINE SURFACE WINDS IN THE WESTERN NORTH PACIFIC FROM CMIP5 AND CMIP6 GCMS FOR WAVE CLIMATE MODELLING

For over years, fundamental component and dataset in climate projection had been covered by general circulation models (GCMs) output mainly from the Coupled Model Inter-comparison Project (CMIP). Marine surface winds are an important output of GCMs and they provide input to marine forecasts and warning systems. Their accuracy have direct implications for marine safety, air-sea fluxes, and wave and ocean modellings. Western North Pacific (WNP) is known as a highly vulnerable region to oceanic and atmospheric hazards, such as storm surges, waves and typhoons. Therefore, this study aims to examine the quality of marine surface winds from CMIP5 and CMIP6 GCMs in the WNP and its sub-regions with respect to a reference data, and presents bias correction of marine surface winds for contributing to wave and ocean modelling communities.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/750mqrERbS8

How Wind Shear Affects Trade-wind Cumulus Convection.

Motivated by an observed relationship between marine low cloud cover and surface wind speed, this study investigates how vertical wind shear affects trade‐wind cumulus convection, including shallow cumulus and congestus with tops below the freezing level. We ran large‐eddy simulations for an idealized case of trade‐wind convection using different vertical shears in the zonal wind. Backward shear, whereby surface easterlies become upper westerlies, is effective at limiting vertical cloud development, which leads to a moister, shallower, and cloudier trade‐wind layer. Without shear or with forward shear, shallow convection tends to deepen more, but clouds tops are still limited under forward shear. A number of mechanisms explain the observed behavior: First, shear leads to different surface wind speeds and, in turn, surface heat and moisture fluxes due to momentum transport, whereby the weakest surface wind speeds develop under backward shear. Second, a forward shear profile in the subcloud layer enhances moisture aggregation and leads to larger cloud clusters, but only on large domains that generally support cloud organization. Third, any absolute amount of shear across the cloud layer limits updraft speeds by enhancing the downward oriented pressure perturbation force. Backward shear—the most typical shear found in the winter trades—can thus be argued a key ingredient at setting the typical structure of the trade‐wind layer.

Standardization of marine surface wind speeds at coastal islands

Field measurements of surface wind can provide valuable information for a wide range of research and practices. However, surface wind records are usually influenced by topographic/terrain effects and direct use of the raw datasets may result in non-ignorable errors for subsequent applications. Thus, it is required to standardize surface wind speed measurements, i.e., to correct raw wind speeds to their potential values which are associated with a given mean speed duration (e.g., 10-min) at a fixed height (e.g., 10 m) above a reference terrain (e.g., open flat terrain). This paper focuses on the standardization of surface wind speed records measured at coastal islands. A standardization scheme is proposed, which takes into account the combined effects associated with topography and speed-dependence of marine roughness z0m. A case study via wind tunnel testing is presented to verify the effectiveness of the proposed scheme. The topographic effects on surface wind speeds are found to vary noticeably with approaching wind field that is characterized by different z0m. The validity of the proposed scheme is examined through comparison of the standardized wind measurements at two coastal stations.

Extreme value statistics of wind speed and wave height of the Marmara Sea based on combined radar altimeter data

Both reliable and long-term wind and wave data are necessary for the design of coastal and offshore structures. Due to lack of sufficient in-situ measurement data, modeling data have been used in the limited number of wind and wave climate studies of the Marmara Sea. Satellites equipped with instruments capable of observing marine surface wind and ocean waves like Radar Altimeter can be another source for the long term wind and wave climate of the Marmara Sea. In this study, for the first time, the altimeter wind speed and the significant wave height data from different satellite missions are attempted to use in the climate and extreme value analysis of the Marmara Sea. Altimeter wind speeds and significant wave heights are compared with the in-situ measurements and it is found that while the altimeter wind speed agrees with the measurement data, the significant wave height data should be calibrated. After the calibration of the altimeter data and the inter-calibrations of earlier satellite missions, 27 years of altimeter wind speed and wave height data are obtained to use in extreme value analysis. The wind speed and the significant wave height values corresponding to various return periods are determined as a result of extreme value statistics and those values are compared with the results of the measurements and previous studies. Consistent extreme values computed in the current study indicate that the combined radar altimeter data can be used in the wind and the wave climate calculations and the extreme value analysis of the Marmara Sea.

Oil Spill Scenarios in the Kotor Bay: Results from High Resolution Numerical Simulations

A major threat for marine and coastal environment comes from oil spill accidents. Such events have a great impact on both the ecosystem and on the economy, and the risk increases over time due to increasing ship traffic in many sensitive areas. In recent years, numerical simulation of oil spills has become an affordable tool for the analysis of the risk and for the preparation of contingency plans. However, in coastal areas, the complexity of the bathymetry and of the orography requires an adequate resolution of sea and wind flows. For this reason, we present, to the best of the author’s knowledge, the first study on the subject adopting Large Eddy Simulations for both the low-atmosphere and sea dynamics in order to provide highly-resolved marine surface current and wind stress to the oil slick model, within a one-way coupling procedure. Such approach is applied to the relevant case of Kotor Bay (UNESCO heritage since 1979), in Montenegro, which is a semi-closed basin surrounded by mountains that is subject to an intense ship traffic for touristic purposes. Oil spill spots are tracked along ship paths, in two wind scenarios.

Statistical Evaluation of Monthly Marine Surface Winds of CMIP6 GCMs in the western North Pacific

Statistical Evaluation of Monthly Marine Surface Winds of CMIP6 GCMs in the western North Pacific

Climatic Study of the Marine Surface Wind Field over the Greek Seas with the Use of a High Resolution RCM Focusing on Extreme Winds

The marine surface wind field (10 m) over the Greek seas is analyzed in this study using The RegCM. The model’s spatial resolution is dynamically downscaled to 10 km × 10 km, in order to simulate more efficiently the complex coastlines and the numerous islands of Greece. Wind data for the 1980–2000 and 2080–2100 periods are produced and evaluated against real observational data from 15 island and coastal meteorological stations in order to assess the model’s ability to reproduce the main characteristics of the surface wind fields. RegCM model shows a higher simulating skill to project seasonal wind speeds and direction during summer and the lowest simulating skill in the cold period of the year. Extreme wind speed thresholds were estimated using percentiles indices and three Peak Over Threshold (POT) techniques. The mean threshold values of the three POT methods are used to examine the inter-annual distribution of extreme winds in the study region. The highest thresholds were observed in three poles; the northeast, the southeast, and the southwest of Aegean Sea. Future changes in extreme speeds show a general increase in the Aegean Sea, while lower thresholds are expected in the Ionian Sea. Return levels for periods of 20, 50, 100, and 200 years are estimated.

Correcting Marine Surface Winds Simulated in Atmospheric Models Using Spatially and Temporally Varying Linear Regression

Abstract This study examines the application of three different variations of linear-regression corrections to the surface marine winds from the Australian Bureau of Meteorology’s recently implemented operational atmospheric model. A simple correction over the entire domain is found to inadequately account for geographical variation in the wind bias. This is addressed by considering corrections that vary in space. Further, these spatially varying corrections are extended to vary in time. In an operational environment, the error characteristics of the wind forcing can be expected to change over time with the evolution of the atmospheric model. This in turn requires any applied correction to be monitored and maintained. Motivated by a desire to avoid this manual maintenance, a self-learning correction method is proposed whereby spatially and temporally varying corrections are calculated in real time from a moving window of historical comparisons between observations and preceding forecasts. This technique is shown to effectively remove both global and regionally varying wind speed biases.

Spatial evaluations of ACCESS marine surface winds using scatterometer data

Spatial evaluations of ACCESS marine surface winds using scatterometer data

Self-Consistency of Marine Surface Wind Vectors Observed by ASCAT

Marine surface wind vectors observed by the Advanced Scatterometer on the MetOp-A satellite are evaluated by assessing their self-consistency. Global statistics on wind speeds and directions were calculated from the data for a period of one year. The wind speed histograms exhibited a clear dependence on the cross-track wind vector cell (WVC) location, which corresponds to the incidence angle. This trend was reflected in the higher order statistics (standard deviation, skewness, and kurtosis) of the wind speed distribution. The histograms of the wind directions relative to the satellite flight direction clearly showed systematic errors relative to the antenna beam directions. The number density of the wind directions exhibited a systematic pattern relative to the antenna beam directions, and the pattern varied with wind speed and cross-track WVC location. These systematic errors in the wind speed and direction may affect the divergence/convergence and rotation of the wind field. The results of this study suggest the need for further refinements of the wind retrieval algorithms and the C-band geophysical model function. It was also confirmed that the evaluation technique based on the statistical distributions of scatterometer-derived vector winds is effective for identifying systematic errors in the wind speeds and directions.

Mapping of the ocean surface wind by ocean acoustic interferometers

Measurements of marine surface winds are crucial to understanding mechanical and thermodynamic forces on the ocean. Satellite measurements of surface winds provide global coverage but are problematic at high wind speeds. Acoustic techniques of wind speed retrieval, and even for tracking hurricanes, have been suggested as an alternative since wind is a strong source of ambient noise in the ocean. Such approaches involve near-local measurements with bottom-mounted hydrophones located close to the area of interest. This paper suggests a complementary approach: measuring directivity of low-frequency ambient noise in the horizontal plane. These measurements would employ long vertical line arrays (VLAs) spanning a significant portion of the ocean waveguide. Two VLAs separated by a distance of some tens of kilometers and coherently measuring acoustic pressure form a single ocean interferometer. By sampling the area of interest from different perspectives with at least two interferometers, marine surface winds might be mapped over horizontal scales of the order of 1000 km with about 10 km resolution (more specifically, the 10 km resolution here means that contribution from the basis functions representing surface wind field with the scale of spatial variations of the order of 10 km can be resolved; independent retrieval of the wind within 10(4) cells of a corresponding grid is hardly possible). An averaging time required to overcome statistical variability in the noise field is estimated to be about 3 h. Numerical simulations of propagation conditions typical for the North Atlantic Ocean are presented.

Estimating the maritime component of aerosol optical depth and its dependency on surface wind speed using satellite data

Abstract. Six years (2003–2008) of satellite measurements of aerosol parameters from the Moderate Resolution Imaging Spectroradiometer (MODIS) and surface wind speeds from Quick Scatterometer (QuikSCAT), the Advanced Microwave Scanning Radiometer (AMSR-E), and the Special Sensor Microwave Imager (SSM/I), are used to provide a comprehensive perspective on the link between surface wind speed and marine aerosol optical depth over tropical and subtropical oceanic regions. A systematic comparison between the satellite derived fields in these regions allows to: (i) separate the relative contribution of wind-induced marine aerosol to the aerosol optical depth; (ii) extract an empirical linear equation linking coarse marine aerosol optical depth and wind intensity; and (iii) identify a time scale for correlating marine aerosol optical depth and surface wind speed. The contribution of wind induced marine aerosol to aerosol optical depth is found to be dominated by the coarse mode elements. When wind intensity exceeds 4 m/s, coarse marine aerosol optical depth is linearly correlated with the surface wind speed, with a remarkably consistent slope of 0.009±0.002 s/m. A detailed time scale analysis shows that the linear correlation between the fields is well kept within a 12 h time frame, while sharply decreasing when the time lag between measurements is longer. The background aerosol optical depth, associated with aerosols that are not produced in-situ through wind driven processes, can be used for estimating the contributions of terrestrial and biogenic marine aerosol to over-ocean satellite retrievals of aerosol optical depth.

Wind and wave predictions in the Adriatic Sea

We analyse the quality of the predictions of wind and waves in the Adriatic Sea considering the corresponding analysis and forecast fields of the European Centre for Medium-Range Weather Forecasts up to 72 h. The whole study is based on a 1-year long period 1st Jan–31st Dec 2006 and two hindcast studies of bora events. Global wind fields are used for the analysis. The marine surface wind speeds are corrected for their underestimate with a procedure based on a long term comparison with measured data. The corrected wind fields are then used to run the WAM wave model and to produce the corresponding analysis and forecast wave fields. These are analysed both among themselves and vs buoy data obtained along the Italian coasts. In particular the detailed analysis of a case of bora highlights the sensitivity of the local wind and wave conditions to small changes in the overall meteorological patterns. This strongly suggests that in an enclosed sea the capability of producing successful forecasts beyond a limited time extent is greatly reduced with respect to the oceans.

An Assessment of Marine Surface Winds from the Australian Bureau of Meteorology Numerical Weather Prediction Systems

AbstractA method for routinely verifying numerical weather prediction surface marine winds with satellite scatterometer winds is introduced. The marine surface winds from the Australian Bureau of Meteorology’s operational global and regional numerical weather prediction systems are evaluated. The model marine surface layer is described. Marine surface winds from the global and limited-area models are compared with observations, both in situ (anemometer) and remote (scatterometer). A 2-yr verification shows that wind speeds from the regional model are typically underestimated by approximately 5%, with a greater bias in the meridional direction than the zonal direction. The global model also underestimates the surface winds by around 5%–10%. A case study of a significant marine storm shows that where larger errors occur, they are due to an underestimation of the storm intensity, rather than to biases in the boundary layer parameterizations.

Modification of the Atmospheric Boundary Layer by a Small Island: Observations from Nauru

Abstract Nauru, a small island in the tropical Pacific, generates cloud plumes that may grow to over 100-km lengths. This study uses observations to examine the mesoscale disturbance of the marine atmospheric boundary layer by the island that produces these cloud plumes. Observations of the surface layer were made from two ships in the vicinity of Nauru and from instruments on the island. The structure of the atmospheric boundary layer over the island was investigated using aircraft flights. Cloud production over Nauru was examined using remote sensing instruments. The diurnal cycles of surface meteorology and radiation are characterized at a point near the west (downwind) coast of Nauru. The spatial variation of surface meteorology and radiation are also examined using surface and aircraft measurements. During the day, the island surface layer is warmer than the marine surface layer and wind speed is lower than over the ocean. Surface heating forces the growth of a thermal internal boundary layer, within which a plume of cumulus clouds forms. Cloud production begins early in the morning over the ocean near the island’s lee shore; as heating intensifies during the day, cloud production moves upwind over Nauru. These clouds form a plume that may extend over 100 km downwind of Nauru. Aircraft observations showed that a plume of warm, dry air develops over the island that extends 15–20 km downwind before dissipating. Limited observations suggest that the cloud plume may be sustained farther downwind of Nauru by a pair of convective rolls. Suggestions for further investigation of the cloud plume are made.

Estimation of Extreme Marine Surface Wind Speed and Storm Surge in Closed Bays in West Japan by Using Stochastic Typhoon Model

Since the terrible storm surge disaster by the Typhoon Vera in 1959, many storm surge defense facilities have been constructed on the coast of bays with disastrous storm surges. The occurrence probability of a higher tidal level than the design tidal level seems to be small, but it may increase due to global warming effects such as the mean sea level rise and typhoon intensification. This study, therefore, gave the value of typhoon parameters under current and future climates by a stochastic typhoon model, and estimated the extreme marine surface depression and wind speed, storm surge, and tidal level with a return period of 10 to 1, 000 years in West Japan. The typhoon development region for the stochastic typhoon model was assumed to move toward the north by 1.5 degrees in latitude from the current to future climate. The simulation result shows that large storm surge and high tidal level over the design condition may appear even under the current climate and that the return period may decrease significantly at some locations.

Simulation of Storm Surge in Seto Inland Sea with Wind Field Estimated by Empirical Typhoon Model and Mesoscale Model

The marine surface wind field in recent major six typhoons over Seto Inland Sea was estimated by using 2D empirical typhoonm odelst, he MASCON model, and the Mesoscale Model MM5 with GPV data and typhoon bogus.A mongt hese models the MM5 estimated the wind field most precisely and improved storm surge estimation. The empirical model taking account of typhoon forwarding into the gradient wind equation and super gradient wind into the wind speed reductionc oefficientg ave the better wind speed variationw itht ime near the typhoonc enter than the empiricalm odel taking the sum of gradient wind and typhoon forwarding vectors. The MASCON model overestimated the effect of land topography on the horizontal wind component and consequently underestimated the wind speed.

Relationship between an el niño event and the interannual variability of significant wave heights in the north pacific

A new global I° × 1° gridded monthly significant wave heights (SWHs) dataset was produced by applying an optimum interpolation method (OIM) to the TOPEX/Poseidon (TP) SWH data obtained from 1993 to 2000. We ascertain the high accuracy of this dataset by comparing it with SWH data obtained from the National Data Buoy Center (NDBC). We then investigate the interannual variability of SWH by using the empirical orthogonal function (EOF) analysis and the relationship of interannual variability between SWH and marine surface winds by using linear regression analysis. When an El Niño event occurs, significant changes can be observed in the SWH east of the Philippines (120°E‐135°E, 10°N‐25°N) and off the US West Coast (140°W‐120°W, 35°N‐45°N). The SWH variability east of the Philippines in winter (January‐March) depends strongly on the northerly winds in relation to the appearance of the Pacific‐North American (PNA) pattern. Off the US West Coast, both the appearance of the PNA pattern and the westerly wind associated with the Aleutian low are very important to wintertime SWH variability. On the other hand, SWH in summer (July‐September) is not related to the PNA pattern either east of the Philippines or off the US West Coast. It is interesting to note that summer SWH off the US West Coast is very low compared with the winter SWH, although the wind speed in summer is almost the same as that in winter. This result suggests that the winter westerlies would lead to higher SWH because of the longer fetch.