Abstract
Evaporative Ducts (ED) are common refractive features that exist due to the persistent/strong vertical moisture gradient inherent to the lowest 10s of meters of the marine atmospheric surface layer (MASL). The ED plays a large role in the propagation of signals from the surface- or ship-based radar/communications systems due to the ducting of electromagnetic (EM) waves. Previous studies have characterized ED structure using mesoscale and surface layer models which are based on the Monin-Obukhov similarity theory. As a result, only the spatially/temporally averaged mean ED structure has been examined. Conversely, this study focuses on ED variability occurring over turbulent energy-containing eddy scales by utilizing large-eddy simulations (LES) of the MASL. This innovative approach reveals that the LES-resolved refractivity perturbations are directly linked to MASL large eddy dynamic and thermodynamic processes. In the thermally unstable MASL, significant turbulent ED variability is noted, with regions of increased ED heights associated with convective updrafts and positive moisture perturbations. In contrast, the thermally stable MASL is shown to exhibit significantly less ED variability over the LES domain. Since current surface layer models have difficulties in calculating ED properties in the thermally stable MASL, utilization of LES is helpful to gain an understanding of the ED in these conditions. A conceptual model of turbulent ED variation is proposed to describe the relationship between MASL dynamics/thermodynamic processes, state variable perturbations, and refractive variations.
| Original language | English (US) |
|---|---|
| Article number | e2022JD036434 |
| Journal | Journal of Geophysical Research: Atmospheres |
| Volume | 127 |
| Issue number | 22 |
| DOIs | |
| State | Published - Nov 27 2022 |
| Externally published | Yes |
Bibliographical note
Funding Information:We acknowledge the support of the CASPER project by the Office of Naval Research Multidisciplinary University Research Initiative (MURI; Award N0001420WX01066 to NPS, N000142112126 to U. Notre Dame sub‐awarded to NPS through the Agreement Number NCRADA ‐ NPS ‐ 21 – 0252 and to UMN through the Agreement Number 204082UM, and N000141613205 to UMN). Qingfang Jiang is supported by the Chief of Naval Research through the NRL Base Program, PE 0601153N. Computational resources were supported by a grant of HPC time from the Department of Defense Major Shared Resource Centers. Lian Shen acknowledges the help of UMN students Tao Cao and Mingxiang Zhao on some of the raw LES data.
Funding Information:
We acknowledge the support of the CASPER project by the Office of Naval Research Multidisciplinary University Research Initiative (MURI; Award N0001420WX01066 to NPS, N000142112126 to U. Notre Dame sub-awarded to NPS through the Agreement Number NCRADA - NPS - 21 – 0252 and to UMN through the Agreement Number 204082UM, and N000141613205 to UMN). Qingfang Jiang is supported by the Chief of Naval Research through the NRL Base Program, PE 0601153N. Computational resources were supported by a grant of HPC time from the Department of Defense Major Shared Resource Centers. Lian Shen acknowledges the help of UMN students Tao Cao and Mingxiang Zhao on some of the raw LES data.
Publisher Copyright:
© 2022 American Geophysical Union. All Rights Reserved. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
Keywords
- air-sea interaction
- evaporation duct
- marine atmospheric surface layer
- RF ducting