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J. C. King

Abstract

Surface pressure measurements from instruments deployed on ice floes in the southern Bellingshausen Sea were used to assess the accuracy of European Centre for Medium-Range Weather Forecasts (ECMWF) analyses in this region during February–May 2001. Despite the lack of in situ observations from this region, the analyses were found to be in very good agreement with the observed pressures and pressure gradients. The absolute difference between observed and analyzed pressures never exceeded 2.7 hPa over a pressure range of 965–1000 hPa. Standard deviations of the differences between observed and analyzed pressures were typically around 1 hPa. When additional in situ surface pressure observations from this region became available for use in the analyses, the agreement between analyzed and observed pressures improved only slightly. This suggests that atmospheric analyses are constrained well by satellite temperature soundings and other remotely sensed data in this region.

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J. C. King and J. Turner

Abstract

No abstract available

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Thomas S. King and Robert C. Balling Jr.

Abstract

Lightning flash data for Arizona from the Bureau of Land Management's magnetic detection finder network are analyzed for the 1989 and 1990 summer monsoon seasons. Results from harmonic analysis reveal a strong diurnal cycle in the frequency of lightning flashes. In much of the state, the time of maximum occurs in the mid-to-late afternoon period. However, in the large valley of central Arizona, the time of maximum lightning frequency is closer to midnight. These results from the emerging lightning flash database should be useful in (a) further evaluating the role of various mechanisms responsible for the nocturnal convective regime of central Arizona, (b) verifying existing and future numerical models of precipitation processes in the region, and (c) preparing and evaluating forecasts of summertime convective events in Arizona.

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J. C. King and W. M. Connolley

Abstract

Surface radiation measurements and other climatological data were used to validate the representation of the surface energy balance over the East Antarctic Ice Sheet in the U.K. Meteorological Office Unified Climate Model. Model calculations of incident and reflected shortwave radiation are in good agreement with observations, but the downward component of longwave radiation at the surface appears to be underestimated by up to 20 W m−2 in the model. Over much of the interior of Antarctica this error appears to be compensated for by an overestimate in turbulent transport of heat to the surface, while over the steep coastal slopes the heat flux is in good agreement with observations but the surface temperature is too low. The excessive heat flux over the interior results largely from the use of an inappropriately large bulk transfer coefficient under very stable conditions, suggesting that the surface heat flux scheme in the model is not ideally formulated for the conditions that prevail in the Antarctic boundary layer.

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W. D. Neff and C. W. King

Abstract

We describe a sequence of tethersonde and solar measurements showing the effects of the pooling of cold air drainages in a basin located along the Colorado River below the Brush drainage. Results obtained during periods of weak ambient winds show that the basin fills over a period of several hours, then eventually overflows. The depth of the pool is such as to affect tributary drainages, such as that of Brush Creek, and to cause the accumulating drainage jets to become elevated as they flow down the larger drainage channels into the basin.

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W. D. King, C. T. Maher, and G. A. Hepburn

Abstract

A further 400 h of flying experience with the CSIRO hot-wire probe has shown that it can accurately measure liquid water content in clouds. Computations and experiments suggest that when an epoxy coating is used for protection, it should be less than 50 μm thick, and that the wire should be operated around 160°C when such coatings are used. Comparisons of performance with the Axially Scattering Spectrometer Probe and in a wet wind tunnel indicate that splashing of drops up to 40 μm diameter is not a problem at speeds up to 80 m s−1.

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Sophie C. Lewis, Andrew D. King, and Sarah E. Perkins-Kirkpatrick

Abstract

The term “new normal” has been used in scientific literature and public commentary to contextualize contemporary climate events as an indicator of a changing climate due to enhanced greenhouse warming. A new normal has been used broadly but tends to be descriptive and ambiguously defined. Here we review previous studies conceptualizing this idea of a new climatological normal and argue that this term should be used cautiously and with explicit definition in order to avoid confusion. We provide a formal definition of a new climate normal relative to present based around record-breaking contemporary events and explore the timing of when such extremes become statistically normal in the future model simulations. Applying this method to the record-breaking global-average 2015 temperatures as a reference event and a suite of model climate models, we determine that 2015 global annual-average temperatures will be the new normal by 2040 in all emissions scenarios. At the regional level, a new normal can be delayed through aggressive greenhouse gas emissions reductions. Using this specific case study to investigate a climatological new normal, our approach demonstrates the greater value of the concept of a climatological new normal for understanding and communicating climate change when the term is explicitly defined. This approach moves us one step closer to understanding how current extremes will change in the future in a warming world.

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Malcolm J. King, Matthew C. Wheeler, and Todd P. Lane

Abstract

The 5-day Rossby–Haurwitz wave is unlike other large-scale wave modes that interact with tropical rainfall in that associated rainfall presents as a modulation of localized areas of rainfall instead of propagating with the wave. This form of wave-modulated convective organization in climate models has received little attention. This study investigates the simulation of interactions between the 5-day wave and tropical convection in 30 models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and compares these with the interaction diagnosed from ERA-Interim and TRMM precipitation data. Models simulate the dry dynamics of the 5-day wave well, with realistic coherences between upper- and lower-tropospheric winds, as well as magnitudes and geographic distribution of wave wind anomalies being close to observations. The models consistently display significant coherences between 5-day-wave zonal winds and precipitation but perform less well at simulating the spatial distribution and magnitude of precipitation anomalies. For example, a third of the models do not reproduce significant observed anomalies near the Andes, and the best-performing model simulates only 38% of the observed variance over the tropical Andes and 24% of the observed variance over the Gulf of Guinea. Models with higher resolution perform better in simulating the magnitude of the Andean rainfall anomalies, but there is no similar relationship over the Gulf of Guinea. The evidence therefore suggests that the simulated interaction is mostly one way only, with the wave dynamics forcing the precipitation variations on the 5-day time scale.

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S. C. Ou, K. N. Liou, and J. F. King

Abstract

We have explored the applicability of the differential inversion (DI) method to temperature retrievals in both clear and cloudy atmospheres using red satellite data. The main theme of the DI is that the local Planck intensity can be exactly expressed by a linear combination of the derivatives of radiances in the logarithmic pressure coordinate. The inversion coefficients are obtained by fitting the weighting function to a generalized form. The higher-order derivatives of radiances are determined from polynomial fittings. The satellite dataset used in this work contains collocated brightness temperatures and radiosonde data that have been collected during the period of Baseline Upper Atmospheric Network (BUAN) experiments. These data include both cloudy and clear cases. A multispectral cloud-removal method using the principle of the N * method has been developed. This method uses radiances of High-Resolution Infrared Radiation Sounder channels 6, 7, and 8 to estimate clear radiances of these channels and the surface temperature simultaneously based on radiative transfer simulations. Subsequently, the quantity N * (the ratio of effective cloud cover over adjacent pixels) and the clear radiances of the rest of the channels are evaluated.

Retrieval results are presented in terms of rms temperature differences between retrieved and sounding profiles. Considering all clear and partly cloudy cases, the rms differences in temperature of approximately 2 K for retrievals using the DI are comparable to those using the minimum-variance scheme. The rms differences in temperature for retrievals using the multispectral cloud-removal scheme are slightly larger than those using the BUAN cloud-removal scheme by approximately 0.5 K. Finally, the rms temperature differences are much smaller than those for the first guess of the minimum-variance scheme. These results indicate fire that the DJ can achieve acceptable performance without first-guess or error covariance matrices; second, that the proposed multispectral cloud-removal method is also capable of generating reasonable cloud-removed clear radiances; and finally that the DI can be used as a tool to obtain first guesses in the current operational method and to perform large-volume temperature retrievals for climate studies.

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

Abstract

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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