COMET® Distance Learning Aviation Courses

Description:
This module deals with identifying the characteristics of radiation versus advection fog events, determining which process is dominating, and applying that understanding when making ceiling and visibility forecasts. A forecast approach using a decision tree is also discussed. This decision tree outlines the basic steps involved in applying a thorough forecast approach to fog and stratus events. The module is based on live teletraining sessions offered in 2003 as part of the Distance Learning Aviation Course 1 (DLAC1) on Fog and Stratus Forecasting.

Objectives:
1. Describe the differing processes that lead to radiation fog and advection fog

2. State the two key ingredients for the formation of fog or low stratus: increasing moisture in the boundary layer or decreasing boundary layer temperatures.

3. Properly identify which processes are dominating a particular fog or low stratus event. You can do this by:

• Examining the characteristics of the processes involved,
• Examining the low-level factors that are influencing the event, and
• Comparing these to the known characteristics, processes, and factors that distinguish a radiation event from an advective event.

Estimated time to complete: 2 h

Description:
This module presents the physical processes and life cycle of radiation fog, including its preconditioning environment, initiation, growth, and dissipation. The processes include radiation (both solar and longwave), soil-atmosphere thermal interactions, turbulent mixing, the roles of condensation nuclei, and droplet settling. Each section includes a set of interactive questions based on the learning content presented.

Tom Dulong of the National Weather Service Center Weather Service Unit (CWSU) in Longmont, Colorado is the Principal Science Advisor for this module, and Dr. Paul Croft, Meteorology Program Coordinator for Jackson State University, provided additional scientific review and guidance.

Objectives:
The goal of this training module is to help you increase your understanding of how radiation fog forms, grows, and dissipates. Such understanding, in turn, can help you more efficiently and accurately evaluate the ability of a given atmospheric environment to generate and/or maintain radiation fog.

Performance Objectives

With Regard to the Preconditioning Environment:
• Identify key conditions and ingredients necessary for development of radiation fog
• Discriminate between large-scale low-level environments that are favorable and unfavorable for development of radiation fog
• Describe the sequence of key surface and boundary-layer processes that prepare the low-level environment for development of radiation fog
• Demonstrate an understanding of how surface cooling dries the micro-boundary layer and prevents low-level condensation from being deposited onto the surface
• Rank various surface and surface cover types in terms of the relative speed with
which low-level air in contact with them will reach saturation

With Regard to Initiation and Growth:
• Identify levels at which radiative cooling is most active at various stages of the fog initiation and growth process
• Demonstrate an understanding of the effects that various condensation nuclei types and concentrations have on fog formation
• Sequence the key processes and events that occur during formation of a layer of radiation fog
• Demonstrate an understanding of how the fog-top inversion is created by the fog itself
• Demonstrate an understanding of influences that heat flux from the surface have on a fog layer during its initiation and growth.

With Regard to Maintenance Phase:
• Describe key processes that balance one another to allow a fog layer to maintain a relatively constant depth.
• Identify conditions in and above a fog-top layer that support continued condensate production
• Identify conditions in and above a fog-top layer that restrict further deepening
• Demonstrate an understanding of the effects that various condensation nuclei types and concentrations have on fog maintenance
• Demonstrate an understanding of the effects that introduction of an overlying cloud layer have on a mature fog layer at the surface
• Demonstrate an understanding of influences that heat flux from the surface have on a mature fog layer
• Identify the typical level of a fog-top inversion
• Demonstrate an understanding of how the fog-top inversion is maintained by various processes at and above the top of the fog layer

With Regard to Dissipation Phase:
• Identify key processes that contribute to the dissipation of a fog layer
• Apply a droplet settling rate calculation to predict the time required for a given depth of fog layer to settle to the ground in the absence of any new condensate production
• Demonstrate an understanding of how radiative heating contributes to dissipation of a fog layer
• Demonstrate an understanding of how turbulent mixing contributes to dissipation of a fog layer
• Demonstrate an understanding of how changes in low-level winds can contribute to dissipation of a fog layer
• Demonstrate an understanding of how introduction of an overlying cloud layer can contribute to dissipation of a fog layer

Estimated time to complete: 1-2 h

Description:
In order to assess whether a fog or stratus event is possible, you must evaluate the synoptic-scale influences that will drive the local conditions. In this module, we examine several common synoptic situations to understand the processes involved in fog or low stratus development. Most of these are forced primarily by advective or dynamic processes (although radiation does play a role). A more detailed discussion of radiation processes is contained in the Radiation Fog module. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus.

Objectives:
• Identify the large-scale and local conditions that support the development, maintenance, and dissipation of fog/stratus events
• Identify several synoptic regimes that can result in advection or radiation fog and the processes that contribute to fog formation, maintenance, and dissipation for each

Estimated time to complete: 2-3 h

Description:
Local and mesoscale influences can make or break your fog or stratus forecast. Influences of local water bodies, terrain, vegetation, soil characteristics, and coastal features on the lower atmosphere can play a vital role in the development, duration, and intensity of these events. As part of the Distance Learning Course 1: Forecasting Fog and Low Stratus, this module examines several of these influences and discusses how they enhance or inhibit a fog or stratus event.

Objectives:
• Identify three local factors that can enhance fog or stratus development and be able to explain why
• Identify and describe the processes external to the boundary layer that influence duration, intensity, and dissipation
• Identify and describe the processes internal to the boundary layer that influence duration, intensity, and dissipation

Estimated time to complete: 2-3 h

Description:
This module addresses the local and regional climatological considerations and presents tools and methodologies that can be used to assess whether atmospheric conditions can foster fog or low stratus development. Knowing your local climatology and assessing whether it supports favorable conditions for fog or low stratus development is an important step in the forecast process. A number of physical conditions that determine fog or stratus development are largely dictated by climatological restraints, as well as the synoptic pattern. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus.

Objectives:
Understand how climate data can be applied to the forecast process
• Understand the strength and limitations of the various types of climate data and their application to fog and stratus forecasting
• Demonstrate an ability to correctly apply climate data to fog and stratus forecasting

Estimated time to complete: 2 h

Description:
This module discusses how to apply various observational data and remote sensing tools such as satellite, METARS, soundings, profilers, radar, and model analyses to diagnose the potential for fog and/or low stratus. Various forecast tools (such as model forecast fields, forecast soundings, and BUFKIT) used to assess fog and/or low stratus potential onset, intensity, and duration are also examined. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus.

Objectives:
• Apply various observational data and remote sensing tools such as satellite, METARS, soundings, profilers, radar, and model analyses to diagnose the potential for fog and/or low stratus
• Apply various forecast tools such as model forecast fields, forecast soundings, and BUFKIT to assess fog and/or low stratus potential onset, intensity, and duration

Estimated time to complete: 3 h

Description:
This case examines an event that took place over New England and the Mid-Atlantic on 14 June 2001. As the culminating exercise for lessons 1 and 2 of the Distance Learning Aviation Course 1 (DLAC1) on Fog and Stratus Forecasting, its objectives are to 1) identify the preconditions favorable for fog or stratus development; 2) identify synoptic and local processes that influence the event; 3) assess onset time, duration, dissipation, and intensity; and 4) develop a TAF that reflects expected changes in ceiling and visibility. The module is a re-creation of several live teletraining sessions offered in 2003 as part of DLAC1.

Objectives:
• Identify the preconditions favorable for fog or stratus development
• Identify both the synoptic and local processes that will be influencing the event
• Determine the details of the forecast in terms of the onset time, the duration, and the time of dissipation, as well as the intensity of the event
• Assess how the fog or stratus event will affect ceiling and visibility
• Write a TAF forecast that reflects those changes in ceiling and visibility

Estimated time to complete: 2 h

Description:
This module addresses issues surrounding the direct and indirect impacts of restricted ceilings and visibilities on aviation operations and also briefly examines their impacts on ground and marine transportation. The goal is improve forecaster awareness of how their forecasts of these events affect commercial and general aviation operation. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus.

Objectives:
• Increase awareness of the various users of ceilings and visibility forecasts and how forecasts of these conditions impact (both positively and negatively) aviation operations within each user group
    o Improve forecaster understanding of the impacts of reduced visibility and ceilings on commercial and general aviation operations
    o Improve forecaster understanding of the impact to aviation operations from forecasts (TAFs) of reduced ceiling and visibility due to fog and low stratus
    o Provide recommendations on how and when to amend TAFs to best reflect current and forecast conditions
• Increase awareness of the need to be knowledgeable about supported airport configurations
• Increase knowledge of critical thresholds and their variations from one airport to another and one user group to another

Estimated time to complete: 1 h

Description:
This module provides an overview of some of the applicable TAF Amendment and Conditional Group usage rules, as presented in the latest version of the National Weather Service Instruction 10-813 on TAF directives. It also presents a methodology for TAF writing and development that will lead to an effective and user-friendly product. The focus is on the ceiling and visibility aspects of the TAF. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus.

Objectives:
• Develop an understanding and appreciation for how TAF construction (intelligent vs. excessive use of TEMPO and PROB groups) may impact your aviation customers
• Develop skills in writing an effective “practical” TAF that provides an improved forecast of expected flight category changes, while maintaining a customer-friendly format. Compare effective vs. poor TAF structures for a given scenario
• Develop concise TAFs with sparing use of change or conditional groups such as TEMPO and PROB, as we’ll practice in two small case exercises

Estimated time to complete: 2 h

Description:
This case study focuses on making a forecast and writing a TAF so that it best represents the meteorological situation to aviation customers. During the exercise, the student prepares a forecast for Sioux Falls, South Dakota. As part of the Distance Learning Aviation Course 1 (DLAC1) on Fog and Stratus Forecasting, the exercise applies concepts taught in the rest of the course, with special emphasis on determining the impacts on airfield flight operations and creating a TAF that describes those impacts. The module is a re-creation of several live teletraining sessions offered in 2003 as part of DLAC1.

Objectives:
• Use model analyses, forecast products, soundings, and climatology to write a customer-friendly TAF
• Evaluate the impacts of forecasted ceiling and visibility conditions on the airfield operations
• Verify the accuracy and usefulness of your TAF

Estimated time to complete: 2 h