| 1. |
- Brodeau, Laurent, et al.
(författare)
-
Climatologically significant effects of some approximations in the bulk parameterizations of turbulent air-sea fluxes
- 2017
-
Ingår i: Journal of Physical Oceanography. - 0022-3670 .- 1520-0485. ; 47:1, s. 5-28
-
Tidskriftsartikel (refereegranskat)abstract
- This paper quantifies the impacts of approximations and assumptions in the parameterization of bulk formulae on the exchange of momentum, heat, and freshwater computed between the ocean and atmosphere. An ensemble of sensitivity experiments are examined. Climatologies of wind stress, turbulent heat flux, and evaporation for the 1982-2014 period are computed using SST and surface meteorological state variables from the ERA-Interim reanalysis. Each experiment differs from the defined control experiment in only one aspect of the parameterization of the bulk formulae. The wind stress is most sensitive to the closure used to relate the neutral drag coefficient to the wind speed in the bulk algorithm, which mainly involves the value of the Charnock parameter. The disagreement between the state-of-the-art algorithms examined is typically of the order of 10%. The largest uncertainties in turbulent heat flux and evaporation are also related to the choice of the algorithm (typically 15%), but also emerge in experiments examining approximations related to the surface temperature and saturation humidity. Thus, approximations for the skin temperature and the salt-related reduction of saturation humidity have a substantial impact on the heat flux and evaporation (typically 10%). Approximations such as the use of a fixed air density, sea level pressure, or simplified formula for the saturation humidity, lead to errors no larger than 4% when tested individually. The impacts of these approximations combine linearly when implemented together, yielding errors up to 20% over mid- and subpolar latitudes.
|
|
| 2. |
- Cronin, Meghan F., et al.
(författare)
-
Air-sea fluxes with a focus on heat and momentum
- 2019
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- © 2019 Cronin, Gentemann, Edson, Ueki, Bourassa, Brown, Clayson, Fairall, Farrar, Gille, Gulev, Josey, Kato, Katsumata, Kent, Krug, Minnett, Parfitt, Pinker, Stackhouse, Swart, Tomita, Vandemark, Weller, Yoneyama, Yu and Zhang. Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m-2 and a bias of less than 5 W m-2. At present this accuracy target is met only at OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500 - 1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1 - 3 measurement platforms in each nominal 10° by 10° boxes. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development, product validation, and for improving satellite-based, NWP and blended flux products. In addition, some of these flux platforms will also measure direct turbulent fluxes, which can be used to improve algorithms for computation of air-sea exchange of heat and momentum in flux products and models. With these improved air-sea fluxes, the ocean's influence on the atmosphere will be better quantified and lead to improved long-term weather forecasts, seasonal-interannual-decadal climate predictions, and regional climate projections.
|
|
