Exploring Relationships of Evaporation Duct Height with Wind Speed and Humidity
Presentation Type
Presentation
Full Name of Faculty Mentor
Erin Hackett, Marine Science; Daniel Greenway (Ph.D. student)
Major
Marine Science
Presentation Abstract
Changes in humidity near the ocean surface can produce a phenomenon called evaporation ducts, which are nearly permanent features within the marine atmospheric surface layer (first ~100 m above the ocean surface). These ducts can cause radar systems operating at X-band frequencies (8-12 GHz) to develop positioning errors, for example, by increasing the range of detection or causing holes in coverage. Radars are important to many civilian and military applications such as weather forecasting, air traffic control, and naval ship self-defense. Evaporation ducts are often characterized by vertical profiles of modified refractivity (M) – a measurement of the index of refraction of the air with respect to the curvature of the earth. A feature of this evaporation duct, called the evaporation duct height, has been shown to be a primary driver of these effects on radar performance. As such, investigating relationships between atmospheric variables and duct height can provide insight into the prediction of these effects. It is commonly known that duct height is related to humidity and wind speed, but these relationships have not been carefully quantified. To explore these relationships, numerical weather prediction data of wind speed and humidity from two different field campaigns were characterized by their altitudinal average from the surface to the duct height. Correlation analysis between these atmospheric properties and duct height is performed. Most commonly, duct height increases as this mean wind speed increases, and decreases as this mean specific humidity increases.
Start Date
12-4-2023 3:40 PM
End Date
12-4-2023 4:00 PM
Disciplines
Oceanography
Recommended Citation
Vaughan, Alexis, "Exploring Relationships of Evaporation Duct Height with Wind Speed and Humidity" (2023). Undergraduate Research Competition. 64.
https://digitalcommons.coastal.edu/ugrc/2023/fullconference/64
Exploring Relationships of Evaporation Duct Height with Wind Speed and Humidity
Changes in humidity near the ocean surface can produce a phenomenon called evaporation ducts, which are nearly permanent features within the marine atmospheric surface layer (first ~100 m above the ocean surface). These ducts can cause radar systems operating at X-band frequencies (8-12 GHz) to develop positioning errors, for example, by increasing the range of detection or causing holes in coverage. Radars are important to many civilian and military applications such as weather forecasting, air traffic control, and naval ship self-defense. Evaporation ducts are often characterized by vertical profiles of modified refractivity (M) – a measurement of the index of refraction of the air with respect to the curvature of the earth. A feature of this evaporation duct, called the evaporation duct height, has been shown to be a primary driver of these effects on radar performance. As such, investigating relationships between atmospheric variables and duct height can provide insight into the prediction of these effects. It is commonly known that duct height is related to humidity and wind speed, but these relationships have not been carefully quantified. To explore these relationships, numerical weather prediction data of wind speed and humidity from two different field campaigns were characterized by their altitudinal average from the surface to the duct height. Correlation analysis between these atmospheric properties and duct height is performed. Most commonly, duct height increases as this mean wind speed increases, and decreases as this mean specific humidity increases.