Marine Weather Research Articles

MARINE WEATHER SYSTEMS: STUDY WITH ASEOS-II AMSR, AQUA AMSR-E AND ENVISAT ASAR

Observations carried out by the Aqua AMSR-E (Advanced Microwave Scanning Radiometer), ADEOS-II AMSR and Envisat ASAR (Advanced Synthetic Aperture Radar) have been used to study the distribution of total water vapor content V, total cloud liquid water content Q, precipitation R and surface wind W in marine weather systems over the Northwestern Pacific Ocean. V, Q and W were retrieved from the measured brightness temperatures TB(n) with vertical and horizontal polarization at AMSR frequencies n with using of the developed algorithms. Strong gradients in the surface wind field existing at scales of a few kilometers and less are dramatically smoothed in AMSR data retrievals as follows from a comparison with Envisat ASAR images. Joint analysis of the active/passive microwave images of the cold air outbreaks and atmospheric convective eddies revealed the relationships of the high-gradient zones of water vapor and surface wind. The regulated structures in the marine boundary layer of the atmosphere such as mesoscale convective cells and rolls, etc. were detected both on the ASAR and on TB(89) images. The NOAA AVHRR, Terra and Aqua MODIS images, QuikSCAT wind vector fields and surface analysis maps were used as complimentary information

Wind information for marine weather forecasting from RADARSAT-1 synthetic aperture radar data: Initial results from the "Marine winds from SAR" demonstration project

The Canadian Ice Service (CIS), part of Environment Canada's Meteorological Service of Canada, has been a primary user of RADARSAT-1 data since its launch in November 1995. Approximately 4000 RADARSAT-1 images are received annually for ice reconnaissance work, but the appearance of dramatic atmospheric conditions imprinted on the open water of oceans and lakes has increased interest in using this data for other marine and meteorological applications. To exploit the CIS operational RADARSAT-1 data stream, a demonstration project was initiated for the winter of 2001 to deliver RADARSAT-1 ScanSAR images and derived wind products to meteorological centres in the East Coast and Great Lakes regions of Canada. Meteorologists were trained in interpreting synthetic aperture radar (SAR) imagery and how wind products are generated from SAR data. From January to April 2001, over 600 images and wind products were delivered in near real time to weather centres for use in forecast production. Feedback from meteorologists in the use of RADARSAT-1 for weather applications was positive, especially for site-specific weather forecasting in regions such as coastal or marginal ice zones, lakes, and estuaries in which scatterometer land contamination is an issue and data from other sources are sparse. Additionally, initial validations of the ocean monitoring workstation (OMW) wind products have shown promising results.

Satellite Passive Sensing of the Marine Atmosphere Associated With Cold-Air Mesoscale Cyclones

Contemporary research into extratropical cloud systems optimizes the increase in resolution of visible (VIS) and thermal infra-red (IR) sensors, and the ability to retrieve wind and atmospheric moisture variables at mesoscales using microwave radiometry. These passively-acquired remote sensing data are used to develop synoptic climatological (conceptual and simple statistical) ‘models’ of mesoscale cyclones in cold-air outbreaks (mesocyclones, ‘polar lows’) occurring over the otherwise data-void southern oceans. Mesocyclones present a limitation to successful weather forecasting for New Zealand and coastal Chile, southern Australia and South Africa, during the cold season. The synoptic climatological analyses show that: 1) the patterns of mesocyclone cloud vortex origins, movement and dissipation (‘mesocyclone regimes’), exhibit spatial dependence and have associations with upper-ocean conditions; 2) mesocyclone ‘outbreaks’ are embedded within characteristic larger-scale anomaly fields of tropospheric pressure, height, and layer thickness (mean temperature); and 3) composite (statistical average) models of cloud system structure based on the microwave retrievals of marine weather reveal mesocyclones to be relatively dry in comparison with synoptic cyclones, yet very windy. These analyses should permit the development of methods to better predict these important cold-season storms over southern middle latitudes, and a fuller assessment of their significance for the larger hydroclimatic system.

Marine Weather program offers new and updated products

Marine Weather program offers new and updated products

Marine Forecasting at the 1996 Centennial Olympic Games

A team of meteorologists from the United States, Canada, and Australia provided marine weather support to the sailing events of the 1996 Centennial Olympic Games, held in Wassaw Sound near Savannah, Georgia. The team conducted research on the weather and climate and developed a set of forecast products designed to inform athletes, volunteers, and race managers of the wind, tidal current, wave, and weather behavior expected each day during the pre-Olympic and Olympic periods. The Olympic period proved to be a challenge with thunderstorms delaying, abandoning, or postponing races on half of the days. Thunderstorm development and movement was linked to the timing and strength of the sea breeze as well as the direction and speed of the gradient wind. Numerous thunderstorm warnings were issued with the assistance of the WSR-88D radar and the Warning Decision Support System. Frequent lightning was a legitimate safety concern due to the long distances between race courses and lack of suitable shelter; fortunately no one was injured during the lightning episodes. Forecasters benefited from access to a variety of monitoring tools and models including real-time Olympic buoy wind and current time series displays; satellite and radar imagery animation; 2-, 8-, and 10-km resolution mesoscale models; a live video feed of race coverage; and communications with forecasters aboard patrol craft offshore. Official wind forecasts, mesoscale models, and a simple vector addition model performed better than climatology and persistence as defined by mean vector error and rms wind direction error. Climatology was difficult to beat on the basis of wind speed error.

The Seasonal Heat Budget of the North Pacific: Net Heat Flux and Heat Storage Rates (1950–1990)

Abstract A new estimate of the heat budget for the North Pacific Ocean is presented in this paper. The seasonal net heat flux and heat storage rates were calculated for the North Pacific Ocean from 1950 to 1990 on a spatial resolution of 5° × 5°. Temperature profiles from the National Ocean Data Center were used to calculate the heat storage rates. Satellite remotely sensed solar irradiance and ship marine weather reports from the Comprehensive Ocean–Atmosphere Data Set were used to calculate the net surface heat flux. Heat storage rates were calculated as the time rate of change of the heat content integrated from the surface down to the isotherm that was 1°C less than the coldest locally observed wintertime sea surface temperature, which was defined as the locally observed wintertime ventilation isotherm. The monthly climatology of the 5° × 5° resolution net heat flux was balanced by the heat storage rate for most regions of the North Pacific. To achieve this balance the net heat flux was calculated usi...

Ocean surface wind speed and direction retrievals from the SSM/I

A semiempirical model is developed that retrieves ocean surface wind direction information in addition to improved wind speeds from Special Sensor Microwave/Imager (SSM/I) measurements. Radiative transfer and neural network techniques were combined in the authors' approach. The model was trained and tested using clear sky cases, but atmospheric transmittance is retrieved so that retrieval in other than clear sky conditions is possible. With two SSM/I instruments currently providing operational ocean surface wind speed retrievals, the addition of wind direction information and improved wind speed retrievals will enhance the impact of this data in weather prediction models and marine weather forecasting.

Response of global upper ocean temperature to changing solar irradiance

By focusing on time sequences of basin‐average and global‐average upper ocean temperature (i.e., from 40°S to 60°N) we find temperatures responding to changing solar irradiance in three separate frequency bands with periods of >100 years, 18–25 years, and 9–13 years. Moreover, we find them in two different data sets, that is, surface marine weather observations from 1990 to 1991 and bathythermograph (BT) upper ocean temperature profiles from 1955 to 1994. Band‐passing basin‐average temperature records find each frequency component in phase across the Indian, Pacific, and Atlantic Oceans, yielding global‐average records with maximum amplitudes of 0.04°±0.01°K and 0.07°±0.01°K on decadal and interdecadal scales, respectively. These achieve maximum correlation with solar irradiance records (i.e., with maximum amplitude 0.5 W m−2 at the top of the atmosphere) at phase lags ranging from 30° to 50°. From the BT data set, solar signals in global‐average temperature penetrate to 80–160 m, confined to the upper layer above the main pycnocline. Operating a global‐average heat budget for the upper ocean yields sea surface temperature responses of 0.01°–0.03°K and 0.02°–0.05°K on decadal and interdecadal scales, respectively, from the 0.1 W m−2 penetration of solar irradiance to the sea surface. Since this is of the same order as that observed (i.e., 0.04°–0.07°K), we can infer that anomalous heat from changing solar irradiance is stored in the upper layer of the ocean.

Seasonal heat storage in the North Pacific: 1976–1989

Volunteer observing ship expendable bathythermograph data obtained during the period 1976–1989, from 30°N to 40°N in the North Pacific, were used to compute the rate of change of heat storage to a fixed upper ocean temperature surface. The variability of the storage rate in the seasonal timescale, computed on a 5° latitude by 5° longitude spatial scale, is compared to the net surface heat flux computed from available surface marine weather data to the same spatial and temporal resolution. Averaged across the entire basin, the difference between the average monthly heat storage rate and the average monthly heat flux is 3.76 Wm−1. The average basin‐wide absolute heat storage rate agrees to within 7.5% of the average absolute heat flux for the whole basin. An empirical orthogonal decomposition of the spatial patterns of the difference between the heat storage rate and the net heat flux reveals no obvious trends in the heat flux computation or possible physical processes responsible for the difference. Instead, the eddies shed by the warm boundary current, the Kuroshio, is probably responsible for the major part of the difference patterns in locations where the difference values are maximum. The most important results of this study are that the heat storage rate computed to a fixed isotherm matches the net heat flux extremely well at the chosen locations and across the whole basin; and the heat storage rate computation is sensitive to the isotherm choice and to the space scale involved.

Validation of tropical ocean‐atmosphere heat fluxes‐from marine data against a satellite‐based method

AbstractOcean‐atmosphere heat fluxes were calculated from marine weather reports over a mesoscale region of the Coral Sea near Townsville, Australia. These heat fluxes were compared, as 5‐week averages, with a set of heat fluxes derived over the same region from a combination of satellite and surface data. These satellite‐ and surface‐derived fluxes were calibrated and validated against accurate, independent surface heat fluxes, as described in a previous paper.Significant differences were noted between the two sets of heat fluxes. The discrepancies in the net solar radiation are attributed to insufficient marine weather reports and/or improper cloud parameterization in the formulae applied to the marine data. Some large differences were observed in the outgoing turbulent heat fluxes, and these were traced to higher water‐air specific humidity gradients in the marine data. These two discrepancies cancel so that the long‐term (45 week) averages of the total ocean‐atmosphere heat flux, at 52 W m−2 for the satellite‐based technique and 34 W m−2 for the shipboard method, differ by only 18 W m−2.On the basis of these systematic differences it was concluded that the heat fluxes derived from satellite and surface data in this study were superior in quality and reliability to heat fluxes calculated from marine weather reports. Further studies are required to test this result in other locations.

Marine climate, weather and fisheries: The effects of weather and climatic changes on fisheries and ocean resources

Marine climate, weather and fisheries: The effects of weather and climatic changes on fisheries and ocean resources

Uncertainties in estimates of surface heat fluxes derived from marine reports over the tropical and subtropical oceans

Estimates are made of the uncertainties in calculations of the heat fluxes at the surface of the tropical and subtropical oceans based upon the bulk formulae and archived marine weather reports. Major contributions are identified not only in the basic observations of such variables as temperature and wind but also in uncertainties in parameters in the bulk formulae themselves. All identified factors are defined as either random or systematic. The potential effects of archiving and sampling errors are also explored. The total uncertainties for individual observations of the net solar and infrared irradiances and the latent and sensible heat fluxes are about 80, 10, 83 and 12 W m^-2, respectively. Because uncertainties associated with random errors decrease when many observations are averaged, the uncertainties in the fluxes decrease substantially when fifty or more observations are averaged together. However, since all of the surface fluxes have some systematic uncertainties associated with them, sizeable uncertainties remain, especially in the latent heat flux, even if an unlimited number of observations is available for calculating the means. Representative maps of uncertainties in 20-year monthly means of the component fluxes over the tropical Pacific show large uncertainties in the equatorial and southeastern oceans. Elsewhere, the net solar and infrared irradiance and sensible heat flux have uncertainties of 10 W m^-2 or less. Unfortunately, the uncertainties in the latent heat flux exceed 30 W m^-2 everywhere, because of the large systematic component. Total uncertainties in the net heating of the ocean surface are relatively large over the entire tropical Pacific with the smallest relative values in the eastern tropical region.

Computer Generation of Marine Weather Forecast Text

Abstract MARWORDS is a natural language text generation system which has been developed to synthesize marine forecasts for the Davis Strait area in Northern Canada. It uses standard manually produced predictions of wind speed, air temperature, and other weather conditions to generate English language text forecasts. The resulting text compares favorably with those written by marine weather specialists. MARWORDS incorporates a detailed grammar to capture the constraints on words, sentences, and texts that are natural to the domain. This grammar was developed from a study of approximately 50 000 words of forecast text. Among the problems faced were the linguistic treatment of data-salience relations and the modulation of temporal adverbs to reflect increasing levels of uncertainty for more remote events. In addition the system was designed so that it could be extended to synthesize bilingual (French and English) or multilingual forecasts.

A Comparison of Shallow Water Model Results for Three Estimates of a Composite El Niño Forcing

A linear shallow water model on an equatorial β-plane is driven by three different estimates of the heating rate perturbation during seven seasons of a composite El Niño episode. In two cases the heating perturbations for this model are assumed to be closely linked to the pattern of sea surface temperature anomalies. In the, third the heating is related to direct estimates of precipitation departures. The model-derived winds based upon these three estimates are compared to one another and to data available from marine weather reports. An analysis of area averaged winds, surface latent heat fluxes and moisture convergences shows general agreement with observations over the composite El Niño seasons for the results of all three forcing estimates, although the model results using the direct precipitation estimates seem generally to be the poorest. A second analysis explores the similarity of smaller-scale features of the model results to the observations. This suggests that the simple parameterized heating using sea surface temperature estimates gives the only solutions which fairly well identify smaller-scale, variations.

The Possible Link Between Net Surface Heating and El Niño

Three diagnostic analyses are described which strongly suggest the importance of local net surface heating in the life history of the large-scale, air-sea phenomenon centered in the eastern tropical Pacific Ocean, commonly called El Niño. These analyses rely upon monthly marine weather summaries for the period 1957 to 1976. In the first, correlations and coherence spectra were calculated which show a strong link between the net surface heat flux and sea-surface temperature variations over the eastern equatorial Pacific. The second analysis, also based upon the use of coherence spectra, indicates a sea temperature precursor in the eastern ocean near 25 degrees S which precedes sea temperature changes near the El Niño focus near 5 degrees S. Since the link between the two regions would require ocean advective velocities that appear to be unreasonably large, this analysis also suggests the importance of atmospheric forcing through the surface heat flux. In the third analysis a proxy variable is described that seems to be a reasonable indicator of the overall effect of ocean dynamics on the temperature of the El Niño core region. A composite analysis of the four El Niño events of 1957, 1965, 1972, and 1976 suggests that local surface heating is important during the early part of an event, whereas dynamical factors dominate later.

Physical Environmental Monitoring In the Offshore

Abstract A summary and review is presented of certain components of a Physical Environmental Monitoring Program conducted by Mobil Oil Canada, Limited. This program is in support of Mobil's East Coast drilling operations. The various meteorological and oceanographic program components are described with specific reference to the use of the data collected by this monitoring program.to collect, record and transmit data on meteorological and oceanographic conditions; andto assist and advise operational personnel on the various meteorological and oceanographic conditions that affect the performance of rig operations. Introduction Physical environmental monitoring is associated with all East Coast offshore exploration drilling operations. Although this paper addresses, in summary form, some components of Mobil on Canada's Environmental Monitoring Program, the program as presented here is in line with those of other offshore operations and fairly representative. The objectives of such a program are four fold:to monitor, in real time, meteorological and oceanographic parameters that influence on-going offshore operations;to record data that can be used to more accurately model and forecast future meteorological and oceanographic parameters that may influence these operations;to archive data for future potential design considerations; andto obtain and retain government approvals to explore and develop. These objectives, in part, are satisfied by Environmental Monitoring Program components, namely:Offshore Ice/Weather Observer ProgramAutomatic Environmental Weather Station ProgramWave Measurement ProgramCurrent Measurement Program Ice/Weather Observer Program The first program component, the Ice/Weather Observer Program, is the cornerstone for a large portion of this environmental monitoring work. Two trained ice/weather observers are stationed on each Mobil contracted drilling rig on a 24-hour basis. Their basic duties are:to collect, record and transmit data on meteorological and oceanographic conditions; andto assist and advise operational personnel on the various meteorological and oceanographic conditions that affect the performance of rig operations. Depending on the drilling area the rig is in. they may also act as the rig's radio operators. This case applies only to Mobil's drilling operation near Sable Island. Some of the duties of the ice/weather observers are carried out in accordance with practices set down by the Atmospheric Environment Services (AES) of the Canadian Government. However, other duties are specific to an offshore drilling operation and are carefully supervised and monitored by Mobil. The most important function of the ice/weather observer is to make meteorological and oceanographic observations. The observations are called MANMAR measurements; MANMAR stands for " Manual of Marine Weather Observing". Observations are generally made every three hours. They are recorded in a report titled " Selected Ships Meteorological Log", which is supplied by AES. An individual observation entails anywhere from 23 to 44 pieces of information. Figure 1 shows the various parameters measured, observed and recorded on this regular schedule. This includes information on winds, waves, and other weather parameters such as low cloud ceiling, visibility, temperature, barometric pressure, ice and icebergs-just about any weather parameter you can

El Niño and Tropical Pacific Ocean Surface Temperatures

Abstract The spatial and temporal character of El Nino is explored with analyses of tropical Pacific Ocean surface temperatures for the period 1957–76. The data are derived from approximately 5×106 marine weather reports. Maps are illustrated which portray the initiation, maturation and decay of an “average” El Nino event. Empirical orthogonal functions of nonseasonal departures are displayed. The time coefficients of the dominant empirical functions are derived together with average departures for 18 regions which are usually 10° of latitude and 40–50° of longitude in size. Lag correlation and coherence-spectral analysts are carried out on all of the time series. The pattern of El Nino which is portrayed is that of a basinwide phenomenon with a time evolution lasting more than 24 months. During this evolution sea temperatures in the western Pacific tend to have departures of opposite sign to those in the cast. Variations in the eastern equatorial region are shown to precede those in the central equatoria...

Annual Mean Atmospheric Statistics at the Surface of the Tropical Pacific Ocean

Abstract Long-term annual means and intramonth variances have been calculated for air and sea surface temperature, specific humidity and surface wind components for most 5° × 5° grids for the Pacific Ocean between 40°S and 30°N. These estimates were calculated from about five million marine weather reports for the years 1957–76. In addition to illustrating maps of these statistics, the annual average mean and eddy meridional fluxes of absolute temperature and specific humidity for the surface layer are portrayed. The calculated divergences of the surface fluxes of temperature and humidity are in good agreement with previously published analyses of rainfall and cloudiness. The possible utility of there flux divergence fields in estimating the patterns of low-level vertical motion and vertically averaged moisture flux divergence is tested.

Annual Mean Surface Heat Fluxes in the Tropical Pacific Ocean

Abstract The four components of the long-term annual mean net surface heating of the tropical Pacific Ocean between 30°N and 40°S are calculated and portrayed. These flux elements were derived by using the bulk formulas and about 5 million marine weather reports for the years 1957–76. In addition to illustrating the mean solar, latent heat, infrared radiation and sensible heat fluxes, annual mean values of the atmospheric variables which contribute to those fluxes also are illustrated. A simple error analysis is carried out from which it is concluded that the 95% confidence bands for solar heating, latent heat loss and net oceanic heating are ±29, ±39 and ±49 W m−2, from the respective mean values. The validity of the results for the net heating is partially tested by comparing the horizontal heat transports required by the pattern of heating with independent estimates of those dynamical transports.

Monthly Mean Wind Fields for the South Atlantic Bight

Abstract A total of 339 389 marine weather observations have been analyzed to Produce Monthly mean wind fields for the South Atlantic Bight. The results of plotting wind vectors on a 1/2° latitude by 1/2° longitude grid yields four traditional seasonal flow regimes (winter, spring, summer and fall) and an additional regime designated as mariners’ fall. These seasonal wind regimes are discussed and related to the monthly mean ocean circulation in the Bight.