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WARREN R. KING

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W. D. King and R. J. Handsworth

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It is shown that when liquid water contents are measured with the CSIRO hot-wire element, and cloud transmission measured in the UV with a simple optical system, then the two measurements can be combined to yield total droplet concentrations and average droplet size. Sizes and concentrations obtained from this technique are compared with those from an optical scattering probe, and reasonable agreement is found.

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Mu-King Tsay, Ting-I. Wang, R. S. Lawrence, G. R. Ochs, and R. B. Fritz

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In a cooperative field study of the planetary boundary layer, three optical wind sensors were placed around a 300 m meteorological tower in a 450 m equilateral triangle 3–4 m above the terrain. It was found that the convergence measured by the three-sensor system correlates well with in situ measurements of vertical wind by anemometers located on the tower at heights up to 300 m during the occurrence of thermal plumes. By analyzing the correlation between the optically measured convergence and the vertical wind measurements made on the tower, the inversion layer, if below the top of the tower, can usually be located in the early morning when thermal plumes are active. The space-averaged horizontal wind vectors measured by the optical system have good, though not perfect, agreement with the tower measurements at the lowest layer (10 m above the ground), and with the measurements of a nearby network of surface anemometers. A comparison of the optically measured convergence with the direction of the surface horizontal wind indicates some effect of irregular terrain.

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Melinda L. King, Phillip J. Smith, and Anthony R. Lupo

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This paper examines the 48-h life cycle of a winter anticyclone occurring over North America from 18 to 20 January 1979 using Goddard Laboratory for Atmospheres FGGE level IIIb (SOP 1) global analyses on a 4° latitude by 5° longitude grid. Applying the relatively new methodology of the Zwack–Okossi equation, results show that anticyclonic vorticity advection and cold-air advection acted to develop the anticyclone, while adiabatic warming in the descending air opposed development. Other forcing processes made only small contributions to anticyclone changes. Vertical profiles of the development quantities reveal that vorticity and temperature advections, as well as the adiabatic warming, maximized in the 200–300-mb layer.

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W. D. King, D. A. Parkin, and R. J. Handsworth

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A liquid water sensor consisting of a thin copper wire wound on a hollow 1.5 mm diameter cylinder is described. Slave coils on either side of the master sensing coil reduce axial heat losses to an acceptable level, and allow for a simple relationship between power supplied to the wire and liquid water content. Wet wind-tunnel tests show that the system response to liquid water is easily calculable from a knowledge of the geometrical dimensions of the cylinder and the operating temperature of the hot wire. When operated at 100°C, the device has a sensitivity of 0.02 g m−3, a response time of better than 0.05 s and an accuracy of 5% at 1 g m−3.

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John J. Cassano, Thomas R. Parish, and John C. King

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Calculated surface fluxes from seven surface layer parameterizations are verified against 45 months of observations from Halley, Antarctica, with a temporal resolution of 1 h. The surface layer parameterizations are taken from widely used numerical models including the National Center for Atmospheric Research (NCAR) Community Climate models CCM2 and CCM3, the U.K. Met. Office Unified Climate Model, and the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). The observations include measurements of the mean wind speed and temperature inversion strength and direct measurements of the turbulent fluxes of heat and momentum.

A comparison of the calculated and observed fluxes is conducted for conditions in which the surface layer is stably stratified. Based on these comparisons it is found that the simulated friction velocity values are adequate (although slightly larger than the observed turbulent fluxes) under all but the highest bulk Richardson number conditions (greatest static stability). In contrast the magnitude of the calculated sensible heat flux is frequently less than that of the observed sensible heat flux. The use of a larger scalar roughness length for heat compared to that for momentum is found to remove this bias in the calculated sensible heat fluxes.

The correlation between the observed and calculated fluxes of heat and momentum is acceptable for the lower bulk Richardson number regimes, but is near zero for the high bulk Richardson number regime. The correlation between the calculated and observed fluxes is in general better for the momentum flux than for the sensible heat flux.

The bias in the calculated sensible heat flux could have significant implications for numerical simulations in which the flow is driven by surface processes, and may pose problems for climate-scale simulations. The impact that errors of the observed magnitude have on simulated katabatic winds is explored with a series of two-dimensional numerical simulations using MM5. Inferences about the relevance of these findings for climate simulations are also addressed.

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Phillip King, Lan R. McKinnon, John G. Mathieson, and Ivan R. Wilson

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The solar infrared spectra of Murcray et al. (1969) do not contain direct evidence for the presence of N2O5 in the stratosphere. Comparison of atmospheric and laboratory spectra indicate that the upper limit to stratospheric N2O5 number density is about 2 × 108 cm−3.

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R. J. Taylor, S. T. Evans, N. K. King, E. T. Stephens, D. R. Packham, and R. G. Vines

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Convection in the air above an intense fire in northern Australia has been studied, and the results are compared with those of an earlier investigation.

At the height of the fire a short-lived condensation cloud, covering little more than 10% of the total fire area, rose to almost 6000 m above ground level. It is suggested that the rising column acted effectively as a barrier to the wind, so reducing mixing with the surrounding air and allowing convection to proceed very rapidly by the release of latent heat alone. In the earlier study it is likely that similar behavior occurred, but the effect was less marked.

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D. J. Lea, I. Mirouze, M. J. Martin, R. R. King, A. Hines, D. Walters, and M. Thurlow

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A new coupled data assimilation (DA) system developed with the aim of improving the initialization of coupled forecasts for various time ranges from short range out to seasonal is introduced. The implementation here is based on a “weakly” coupled data assimilation approach whereby the coupled model is used to provide background information for separate ocean–sea ice and atmosphere–land analyses. The increments generated from these separate analyses are then added back into the coupled model. This is different from the existing Met Office system for initializing coupled forecasts, which uses ocean and atmosphere analyses that have been generated independently using the FOAM ocean data assimilation system and NWP atmosphere assimilation systems, respectively. A set of trials has been run to investigate the impact of the weakly coupled data assimilation on the analysis, and on the coupled forecast skill out to 5–10 days. The analyses and forecasts have been assessed by comparing them to observations and by examining differences in the model fields. Encouragingly for this new system, both ocean and atmospheric assessments show the analyses and coupled forecasts produced using coupled DA to be very similar to those produced using separate ocean–atmosphere data assimilation. This work has the benefit of highlighting some aspects on which to focus to improve the coupled DA results. In particular, improving the modeling and data assimilation of the diurnal SST variation and the river runoff should be examined.

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David J. Karoly, Mitchell T. Black, Andrew D. King, and Michael R. Grose
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