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Richard J. Lind and William J. Shaw

Abstract

Calibration of an airborne Lyman-α hygrometer against simultaneous measurements of humidity from a dewpoint hygrometer shows that Lyman-α biases drift with time. Analyses of low-level flight data from four days during the 1986 Frontal Air–Sea Interaction Experiment indicate that Lyman-α gains are constant for each Right (∼ 3 h duration) but different on each day. If not explicitly accounted for, the time-varying bias can introduce a significant error in calculated humidities from the Lyman-α hygrometer.

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Robert Frouin, Catherine Gautier, Kristina B. Katsaros, and Richard J. Lind

Abstract

Surface insulation data collected during the Mixed Layer Dynamiccs Experiment are used to intercompare the satellite technique of Gautier et al. (1980) and five commonly referenced empirical formulas for estimating daily insulation over the oceans. The results demonstrate the superiority of the satellite technique, which exhibits a 0.97 correlation coefficient, a 12.0 W m M−2 error of estimate, and a −4.9 W m−2 bias error, and which is also able to account for water vapor, ozone, and dust amount variations in the atmosphere and monitor quasi-instantaneously vast extents of ocean. Among the empirical formulas, Mosby's (1936) yields the best predictions with a 0.84 correlation coefficient, a 19.1 W m−2 standard error of estimate, and a 3.4 W m−2 bias. Kimball'(1928) and Reed's (1977) formulas however, perform nearly as well. The largest biases are obtained with Berliand's (1960) and Laevastu' (1960) formulas, which overestimate insolation by 15.2 and 24.5 W m−2, respectively. It is suggested the empirical formulas, even though established from visual cloud cover observations, would provide useful insolation estimates if employed with satellite-derived cloud cover.

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Paul H. Dobos, Richard J. Lind, and Russell L. Elsberry

Abstract

A special set of radar wind profiler observations during the Tropical Cyclone Motion (TCM-90) field experiment is used to relate lower-tropospheric winds to surface sustained winds and gusts on the west coast of Okinawa. Owing to the passage of four typhoons at various separation distances, hourly comparisons are possible for lower-tropospheric wind speeds ranging from 0 to 40 m s−1. Regressions with nonzero intercepts provide more accurate estimates than simple ratios between lower-tropospheric winds and surface sustained winds and gusts. Little difference is found in use of a layer-average wind between 600 and 1800 m compared to regressions for individual levels. Stratification of the data into daytime and nighttime regression equations markedly improves surface sustained wind and gust predictions for wind speeds below 30 m s−1. It is recommended that these daytime and nighttime regression equations he used to estimate surface winds over coastal regions when lower-tropospheric wind observations are available or when a tropical island wind report is available and a lower-tropospheric wind speed estimate is required.

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Paul A. Hirschberg, Richard J. Lind, Steven J. Bolduc, and Russell L. Elsberry

Mesoscale weather systems that develop in the central United States are often forced by environmental features that have formed far upstream over the conventional data-sparse Pacific Ocean. Although remotely sensed observations, such as satellite retrievals, are becoming more numerous and accurate, they still may not have the resolution necessary to enhance global model-based analyses and forecasts over this region. These global model products are the primary source of lateral boundary conditions that have been found to have large impacts on the downstream forecast skill of regional mesoscale models over the United States. In addition, the temporal and spatial resolution of the current rawinsonde network along the West Coast may not be sufficient to detect and measure mesoscale flow features as they move inland. During the STORM-FEST experiment in February–March 1992, a “Picket Fence” of seven special rawinsonde stations were interspersed among the seven regular rawinsonde sites from Port Hardy, British Columbia, to San Diego, California. All sites obtained observations every 3 h rather than the normal 12 h. The objective of the Picket Fence was to examine the feasibility of using extra observations in time and space to improve upstream boundary conditions for forecasts of mesoscale weather events in the central United States. As a first step in examining the potential boundary condition impact of the Picket Fence, fluxes of mass, heat, momentum, potential energy, kinetic energy, and moisture across the West Coast resolved with various spatial and temporal combinations of Picket Fence data are compared with the 12-h regular upper-air sites as the standard. When a wave system crossed the middle of the Picket Fence, significantly different fluxes were calculated with the full spatial and 3-h Picket Fence observations. For other systems that crossed near the margins of the Picket Fence, only small changes were detected by the additional observations.

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Jennifer A. Francis, Thomas P. Ackerman, Kristina B. Katsaros, Richard J. Lind, and Kenneth L. Davidson

Abstract

Measurements of surface radiation fluxes and meteorological conditions collected in the Fram Strait during the summer 1984 Marginal Ice Zone Experiment (MIZEX) are presented and analyzed. These data were combined with calculations from a radiative transfer model to estimate surface and atmospheric moan radiation budgets on a daily basis and for the early summer season over both sea ice and open water in the marginal ice zone (MIZ). Intensities of solar and infrared fluxes within the atmospheric column, radiative properties of Arctic stratus, and atmospheric cooling rates due to the net loss of radiation were computed by the model.

Results show significant differences between the radiation budgets of sea-ice and open-water regimes in the MIZ. Fluxes averaged over the experimental period (16 June to 10 July) indicate that the atmosphere-open water system gained approximately 60 W m−2, while the atmosphere-ice regime was nearly in equilibrium. The open water absorbed twice as much radiation as did the ice, and the mean cooling rate of the over-water atmosphere was approximately 15% larger than that over ice. Observations and model calculations agree that the effect of varying surface albedo on flux intensities is significantly reduced in overcast conditions as compared to under clear skies.

Fluxes and atmospheric cooling rates were compared to values computed by other investigators. Few studies of Arctic radiation exist due to the dearth of observations from polar regions, but available values compare well with those derived from MIZEX data. Cooling rates calculated for the Farm Strait MIZ are twice as large as estimates for the central Arctic in summer. Evidence suggests that this cooling may be offset by a relatively strong poleward atmospheric advection of sensible and latent heat from the Norwegian Sea area.

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Qing Wang, Denny P. Alappattu, Stephanie Billingsley, Byron Blomquist, Robert J. Burkholder, Adam J. Christman, Edward D. Creegan, Tony de Paolo, Daniel P. Eleuterio, Harindra Joseph S. Fernando, Kyle B. Franklin, Andrey A. Grachev, Tracy Haack, Thomas R. Hanley, Christopher M. Hocut, Teddy R. Holt, Kate Horgan, Haflidi H. Jonsson, Robert A. Hale, John A. Kalogiros, Djamal Khelif, Laura S. Leo, Richard J. Lind, Iossif Lozovatsky, Jesus Planella-Morato, Swagato Mukherjee, Wendell A. Nuss, Jonathan Pozderac, L. Ted Rogers, Ivan Savelyev, Dana K. Savidge, R. Kipp Shearman, Lian Shen, Eric Terrill, A. Marcela Ulate, Qi Wang, R. Travis Wendt, Russell Wiss, Roy K. Woods, Luyao Xu, Ryan T. Yamaguchi, and Caglar Yardim

Abstract

The Coupled Air–Sea Processes and Electromagnetic Ducting Research (CASPER) project aims to better quantify atmospheric effects on the propagation of radar and communication signals in the marine environment. Such effects are associated with vertical gradients of temperature and water vapor in the marine atmospheric surface layer (MASL) and in the capping inversion of the marine atmospheric boundary layer (MABL), as well as the horizontal variations of these vertical gradients. CASPER field measurements emphasized simultaneous characterization of electromagnetic (EM) wave propagation, the propagation environment, and the physical processes that gave rise to the measured refractivity conditions. CASPER modeling efforts utilized state-of-the-art large-eddy simulations (LESs) with a dynamically coupled MASL and phase-resolved ocean surface waves. CASPER-East was the first of two planned field campaigns, conducted in October and November 2015 offshore of Duck, North Carolina. This article highlights the scientific motivations and objectives of CASPER and provides an overview of the CASPER-East field campaign. The CASPER-East sampling strategy enabled us to obtain EM wave propagation loss as well as concurrent environmental refractive conditions along the propagation path. This article highlights the initial results from this sampling strategy showing the range-dependent propagation loss, the atmospheric and upper-oceanic variability along the propagation range, and the MASL thermodynamic profiles measured during CASPER-East.

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