Marine Forecasting Course

Lecture 1: Measuring Winds from Space - Scatterometers

Winds over sea are essential for marine forecasting and used in nowcasting and numerical weather prediction (NWP) to aid, among others, in off-shore activities (e.g., energy sector), transport and recreation, particularly to secure safety of life and property. Winds over sea are observed by satellites and available from NWP model forecasts. Most satellite winds over sea are provided by scatterometers these days; they provide swath fields of both wind speed and wind direction from polar satellites. More satellite winds are becoming available through a global virtual constellation of scatterometers. Currently, winds from MetOp-A, MetOp-B and the Indian OceanSat-2 are operationally available and provide good day coverage. Moreover, winds from the Chinese HY2A satellite are being tested with good results at KNMI and further scatterometer launches are being approved. The lecture will briefly comment on these developments, but mainly focuses on what scatterometer winds really represent, how good they are for marine forecasting and what aspects need attention when applying these winds in your routine operations.

Lecture 2: Measuring Wind and Waves from Space - Altimeters

Conventional observations of wind and wave data from ships and buoys are limited by coverage. Due to the increasing size of ships, observers are more removed from the ocean surface and wave estimation is more difficult. Satellite altimeters are a downward pointing radar that scan the oceans and provide very accurate observations of wave height, wind speed, sea surface height anomaly. Our understanding of sea level-rise is due in large part to the record of altimeter based sea level data.

Forecasters responsible for ocean and coastal waters must rely on any information for situational awareness and to keep forecasts relevant. Satellite altimeters provide very accurate coincident measures of significant wave height and wind speed. Integrated data display and product generation systems offer the opportunity for forecasters to compare a variety of observations, imagery, and numerical model predictions to enhance awareness and communicate hazards to mariners. This session will discuss the use by forecasters of altimeter wave and wind data with other sources in an operational forecast center.

Lecture 3: Fog in the Marine Environment

Marine fog formation, development, and dissipation depend on many important physical, chemical, radiative, dynamical, and thermodynamical processes as well surface characteristics of the location in the ocean-land boundary system. Marine fog can be either warm fog or cold fog depend on temperature (T); if T is less than or equal to zero in the air, fog is called as freezing fog. The main reason of the fog formation is usually due to warm and moisture air advection over the cold ocean surface or over the radiatively cooled land surface. Ts-Td (ocean surface T and air dew point T) difference of about 2°C is usually used for a limit for fog formation. It is also possible that local marine environment can enhance or weaken the fog intensity because of vegetation, surface height, and sea breezes. Fog over the marine environments is usually dissipates at noon because of radiative heating and mixing due to turbulence with higher dry air. The intensity of fog is the function of liquid water content (LWC) and droplet number concentration (Nd) of the particles in the air mass. Increasing LWC and Nd result in visibility down to 10s of meters. In this presentation, marine fog observations using surface instruments and remote sensing platforms, and as well as its forecasting based on numerical models will be discussed and its effect on aviation, marine environment, transportation, and vegetation will be summarized.

Lecture 4: Sea Ice Detection and Products

Accurate measurement of sea ice properties is important for example in initializing numerical weather and ice models (data assimilation), navigation in the sea ice covered areas, and for monitoring the annual changes in the global ice cover (climate change). The presentation will cover the remote sensing (RS) techniques for detecting and measuring sea ice. Measuring of different sea ice parameters based on space-borne Rs instruments has been developed significantly during the recent years, and many sea ice parameters can now be measured by different RS instruments. The sea ice parameters that can be measured by RS include ice type, ice deformation, ice concentration (ice area), ice thickness and ice drift. Different kind of RS instruments are used for measuring these quantities: radiometers operating at different wavelengths, sunthetic aperture radars, coastal radars, altimeters. The presentation covers these methods and an introduction to algorithms for measuring the ice parameters. Existing ice products are presented, and also the deficiencies of the methods and validation of the measurements are shortly discussed.

Lecture 5: Ocean Wave Models

Nowadays, an accurate description of the surface waves that are generated by the wind (wind waves) can be achieved by running a wave model. In turn, waves affect the wind profile over the oceans. Such an effect is accounted for in the ECMWF forecasting systems by having a wave model component within the atmospheric model.

A brief review of the essence of how ocean waves forecasts are obtained will be presented. This will be followed by a comprehensive description of the type of wave products that are available (from deterministic to probabilistic one). Waves are essentially global and can therefore affect areas far away from the generating storms. Examples will be presented to illustrate these last points.

Lecture 6: Ship Routing

Thomas Bruns gives a presentation on the history of ship routing and its improvements in the last 20 years, further on ocean waves and its related hazards. He gives an introduction to the classical methods of navigation. Route optimization is closely related to the ship performance, time optimization will not work without the knowledge of detailed ship properties. Finally, the two competing ways of navigating ships across the ocean, namely onboard and shore-based routing, will be discussed.

Lecture 7: Hurricanes and extra-tropical Cyclones

Forecasting Tropical cyclones in the medium range

In this module the importance of forecasting tropical cyclones (TC) is briefly discussed. An overview is given of the recent developments in the forecast systems at ECMWF with impact on the forecast of TCs, including the recent change in the model’s resolution and the implementation of the Ensemble Data Assimilation. At the present time, any TC formed in the forecast system can be identified using a tracker developed at ECMWF. How does it work and what kind of products that can be derived from it is discussed. Some examples are also presented to highlight the model's ability to forecast the genesis of TCs. Finally the statistics of the forecast performance for TCs is discussed.

Lecture 8: Hurricanes and extra-tropical Cyclones

Frontal Structures and High Winds in Extratropical Cyclones

This talk presents new conceptual models in cyclone structures and evolutions. How does the large-scale flow in which the cyclone is embedded determine the type of frontal evolution that occurs? How does the air flow through cyclones, and what can this tell us about the possibility for damaging winds at the surface? This talk concludes with general principles for how forecasters can improve their skill through the use of conceptual models in operational forecasting.

Lecture 9: Rapid Cyclogenesis

Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure systems that occur in the middle latitudes and are associated with fronts (cold front, warm front and occlusion) and horizontal gradients in temperature and dew point , known as baroclinic zones. Extratropical cyclones are the everyday phenomena which, along with anticyclones, drive the weather over much of the Earth, producing anything from cloudiness and mild showers to heavy gales and thunderstorms. Evolution of these depressions can be recognized in the developing of the cloud systems. These cloud developments are the footprints of physical processes in the upper air. In case of explosive deepening it is called rapid cyclogenesis. Satellite imagery, especially recognition of cloud patterns and water vapour structures, can be a great help for marine forecasters to find the area where these cyclogenesis occurs. The deepening of the depression, where you can expect the strongest wind speeds at sea surface and what will be the distribution of the precipitation are issues which will be covered during the lecture. In general, the lecture will give insight in physical processes which can explain the development and life-cycle of rapid cyclogenesis by using single channel satellite images and RGB-images in combination with NWP model fields.

Lecture 10: Polar Lows

Polar lows are small but fairly intense lows that develop during cold air episodes during the winter season in the marine Arctic. The lecture will adress some of the basic formation processes, the climatology and traditional forecasting based on deterministic short range models. Recently, Polar Lows are tracked using fine scale EPS based on the UM, and presently the Harmonie 2,5 km model. Results are represented as an estimate of probability for PL tracks, wind and precipitation.