The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, having a significant impact on medium-range weather forecasts and climate integrations. To pursue this ...further, a moderately stratified Arctic case is simulated by nineteen single-column turbulence schemes. Statistics from a large-eddy simulation intercomparison made for the same case by eleven different models are used as a guiding reference. The single-column parameterizations include research and operational schemes from major forecast and climate research centres. Results from first-order schemes, a large number of turbulence kinetic energy closures, and other models were used. There is a large spread in the results; in general, the operational schemes mix over a deeper layer than the research schemes, and the turbulence kinetic energy and other higher-order closures give results closer to the statistics obtained from the large-eddy simulations. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored.PUBLICATION ABSTRACT
We present the main results from the second model intercomparison within the GEWEX (Global Energy and Water cycle EXperiment) Atmospheric Boundary Layer Study (GABLS). The target is to examine the ...diurnal cycle over land in today’s numerical weather prediction and climate models for operational and research purposes. The set-up of the case is based on observations taken during the Cooperative Atmosphere-Surface Exchange Study-1999 (CASES-99), which was held in Kansas, USA in the early autumn with a strong diurnal cycle with no clouds present. The models are forced with a constant geostrophic wind, prescribed surface temperature and large-scale divergence. Results from 30 different model simulations and one large-eddy simulation (LES) are analyzed and compared with observations. Even though the surface temperature is prescribed, the models give variable near-surface air temperatures. This, in turn, gives rise to differences in low-level stability affecting the turbulence and the turbulent heat fluxes. The increase in modelled upward sensible heat flux during the morning transition is typically too weak and the growth of the convective boundary layer before noon is too slow. This is related to weak modelled near-surface winds during the morning hours. The agreement between the models, the LES and observations is the best during the late afternoon. From this intercomparison study, we find that modelling the diurnal cycle is still a big challenge. For the convective part of the diurnal cycle, some of the first-order schemes perform somewhat better while the turbulent kinetic energy (TKE) schemes tend to be slightly better during nighttime conditions. Finer vertical resolution tends to improve results to some extent, but is certainly not the solution to all the deficiencies identified.
This is the second in a series of papers examining the behavior of the Milbrandt-Yau multimoment bulk microphysics scheme for the simulation of the 13-14 December 2001 case of orographically enhanced ...precipitation observed during the second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) experiment. The sensitivity to the number of predicted moments of the hydrometeor size spectra in the bulk scheme was investigated. The triple-moment control simulations presented in Part I were rerun using double- and single-moment configurations of the multimoment scheme as well the single-moment Kong-Yau scheme. Comparisons of total precipitation and in-cloud hydrometeor mass contents were made between the simulations and observations, with the focus on a 2-h quasi-steady period of heavy stratiform precipitation. The double- and triple-moment simulations were similar; both had realistic precipitation fields, though generally overpredicted in quantity, and had overprediction of snow mass and an underprediction of cloud water aloft. Switching from the triple- to single-moment configuration resulted in a simulation with a precipitation pattern shifted upwind and with a larger positive bias, but with hydrometeor mass fields that corresponded more closely to the observations. Changing the particular single-moment scheme used had a greater impact than changing the number of moments predicted in the same scheme, with the Kong-Yau simulations greatly overpredicting the total precipitation in the lee side of the mountain crest and producing too much snow aloft. Further sensitivity tests indicated that the leeside overprediction in the Kong-Yau runs was most likely due to the combination of the absence of the latent heat effect term in the diffusional growth rate for snow combined with the assumption of instantaneous snow melting in the scheme.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Using the Montreal Urban Snow Experiment (MUSE) 2005 database, surface radiation and energy exchanges are simulated in offline mode with the Town Energy Balance (TEB) and the Interactions between ...Soil, Biosphere, and Atmosphere (ISBA) parameterizations over a heavily populated residential area of Montreal, Quebec, Canada, during the winter–spring transition period (from March to April 2005). The comparison of simulations with flux measurements indicates that the system performs well when roads and alleys are snow covered. In contrast, the storage heat flux is largely underestimated in favor of the sensible heat flux at the end of the period when snow is melted. An evaluation and an improvement of TEB's snow parameterization have also been conducted by using snow property measurements taken during intensive observational periods. Snow density, depth, and albedo are correctly simulated by TEB for alleys where snow cover is relatively homogeneous. Results are not as good for the evolution of snow on roads, which is more challenging because of spatial and temporal variability related to human activity. An analysis of the residual term of the energy budget—including contributions of snowmelt, heat storage, and anthropogenic heat—is performed by using modeling results and observations. It is found that snowmelt and anthropogenic heat fluxes are reasonably well represented by TEB–ISBA, whereas storage heat flux is underestimated.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Environment Canada ran an experimental numerical weather prediction (NWP) system during the Vancouver 2010 Winter Olympic and Paralympic Games, consisting of nested high-resolution (down to 1-km ...horizontal grid-spacing) configurations of the GEM–LAM model, with improved geophysical fields, cloud microphysics and radiative transfer schemes, and several new diagnostic products such as density of falling snow, visibility, and peak wind gust strength. The performance of this experimental NWP system has been evaluated in these winter conditions over complex terrain using the enhanced mesoscale observing network in place during the Olympics. As compared to the forecasts from the operational regional 15-km GEM model, objective verification generally indicated significant added value of the higher-resolution models for near-surface meteorological variables (wind speed, air temperature, and dewpoint temperature) with the 1-km model providing the best forecast accuracy. Appreciable errors were noted in all models for the forecasts of wind direction and humidity near the surface. Subjective assessment of several cases also indicated that the experimental Olympic system was skillful at forecasting meteorological phenomena at high-resolution, both spatially and temporally, and provided enhanced guidance to the Olympic forecasters in terms of better timing of precipitation phase change, squall line passage, wind flow channeling, and visibility reduction due to fog and snow.
A World Weather Research Programme (WWRP) project entitled the Science of Nowcasting Olympic Weather for Vancouver 2010 (SNOW-V10) was developed to be associated with the Vancouver 2010 Olympic and ...Paralympic Winter Games conducted between 12 February and 21 March 2010. The SNOW-V10 international team augmented the instrumentation associated with the Winter Games and several new numerical weather forecasting and nowcasting models were added. Both the additional observational and model data were available to the forecasters in real time. This was an excellent opportunity to demonstrate existing capability in nowcasting and to develop better techniques for short term (0–6 h) nowcasts of winter weather in complex terrain. Better techniques to forecast visibility, low cloud, wind gusts, precipitation rate and type were evaluated. The weather during the games was exceptionally variable with many periods of low visibility, low ceilings and precipitation in the form of both snow and rain. The data collected should improve our understanding of many physical phenomena such as the diabatic effects due to melting snow, wind flow around and over terrain, diurnal flow reversal in valleys associated with daytime heating, and precipitation reductions and increases due to local terrain. Many studies related to these phenomena are described in the Special Issue on SNOW-V10 for which this paper was written. Numerical weather prediction and nowcast models have been evaluated against the unique observational data set now available. It is anticipated that the data set and the knowledge learned as a result of SNOW-V10 will become a resource for other World Meteorological Organization member states who are interested in improving forecasts of winter weather.
This paper reports the first evaluation of the Milbrandt-Yau multimoment bulk microphysics scheme against in situ microphysical measurements. The full triple-moment version of the scheme was used to ...simulate a case of orographically enhanced precipitation with a 3D mesoscale model at high resolution (4- and 1-km grid spacings). The simulations described in this paper also serve as the control runs for the sensitivity experiments that will be examined in Part II of this series. The 13-14 December 2001 case of heavy orographically enhanced precipitation, which occurred over the Oregon Cascades, was selected since it was well observed during the second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) observational campaign. The simulated fields were compared with observed radar reflectivity, vertical velocity, precipitation quantities from rain gauges, and microphysical quantities measured in situ by two instrumented aircraft. The simulated reflectivity structure and values compared favorably to radar observations during the various precipitation stages of the event. The vertical motion field in the simulations corresponded reasonably well to the mountain-wave pattern obtained from in situ and dual-Doppler radar inferred measurements, indicating that biases in the simulations can be attributed in part to the microphysics scheme. The patterns of 18-h accumulated precipitation showed that the model correctly simulated the bulk of the precipitation to accumulate along the coastal mountains and along the windward slope of the Cascades, with reduced precipitation on the lee side of the crest. However, both the 4- and 1-km simulations exhibited a general overprediction of precipitation quantities. The model also exhibited a distinct bias toward overprediction of the snow mass concentration aloft and underprediction of the mass and vertical extent of the pockets of cloud liquid water on the windward side of the Cascades. Nevertheless, the overall spatial distribution of the hydrometeor fields was simulated realistically, including the mean-mass particle diameters for each category and the observed trend of larger snow sizes to be located at lower altitudes. PUBLICATION ABSTRACT
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Within the framework of a large urban meteorology program recently launched in Canada, the Montreal Urban Snow Experiment (MUSE) campaign has been conducted in order to document the thermoradiative ...exchanges in a densely built-up area of Montreal in late winter and spring conditions. The targeted period is of particular scientific interest because it covers the transition period from a mainly snow-covered urban environment to a mainly snow-free environment. The campaign is based on four weeks of observations from 17 March to 14 April 2005. It couples automatic and continuous measurements of radiation and turbulent fluxes, radiative surface temperatures, and air temperature and humidity with manual observations performed during intensive observation periods to supplement the surface temperature observations and to characterize the snow properties. The footprints of radiation and turbulent flux measurements are computed using the surface–sensor–sun urban model and the flux-source area model, respectively. The analysis of the radiometer footprint underscores the difficulty of correctly locating this type of instrument in urban environments, so that the sensor sees a representative combination of the urban and nonurban surfaces. Here, the alley contribution to the upward radiation tends to be overestimated to the detriment of the road contribution. The turbulent footprints cover homogeneous zones in terms of surface characteristics, whatever the wind direction. The initial analysis of the energy balance displays the predominance of the residual term (Q
Res=Q* −QH
−QE
) in comparison with the turbulent sensible (QH
) and latent (QE
) heat fluxes, since its daytime contribution exceeds 50% of the net radiation (Q*). The investigation of energy balances observed at the beginning and at the end of the experiment (i.e., with and without snow) also indicates that the snow plays a significant role in the flux partitioning and the daily pattern of fluxes. Without snow, the energy balance is characteristic of energy balances that have been already observed in densely built-up areas, notably because of the hysteresis observed forQ
ResandQH
in relation toQ* and because of the high contribution ofQ
Res, which includes the effect of heat storage inside the urban structures. With snow, the flux partitioning is modified by the snowmelt process leading to contributions of the residual term and latent heat flux, which are larger than in the case without snow to the detriment of the sensible heat flux.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Cotton (Gossypium hirsutum) fiber is sometimes affected by hardlock, which is characterized by a failure of the fiber to expand outward from the boll at maturity. Because affected fiber is ...inaccessible to mechanical harvesters, yield loss can be considerable. Hardlock has been linked to infection by Fusarium verticillioides. The involvement of flower thrips (Frankliniella spp.), which are commonly found in cotton flowers, was explored. At 1100 h, approximately 10% of cotton flowers contained thrips that were carrying F. verticillioides. The effect of thrips and/or Fusarium in flowers and bolls was explored under greenhouse conditions. Exposing flowers to Fusarium and thrips resulted in bolls with the most severe symptoms. Exposure to either Fusarium or thrips alone resulted in more hardlock than was noted in the control group. The impact of thrips was also evaluated under field conditions. Field plots were treated with insecticides, a fungicide, both, or left untreated. Insecticides reduced thrips numbers and reduced hardlock severity. The fungicide had no impact on thrips numbers and was less effective at reducing hardlock. Combining insecticide and fungicide applications was no more effective than using insecticides alone, although it more frequently increased yield. The untreated control plots generally had the most severe hardlock and lowest yields. Reducing hardlock severity resulted in higher yields, although not consistently. These studies suggest that thrips increase the severity of hardlock, and reducing their numbers may diminish hardlock severity.
‘FL12034‐10’ (Reg. no. CV‐389, PI 704483), a facultative oat (Avena sativa L.) cultivar, co‐developed by the University of Florida and Louisiana State University Agricultural Center, was released in ...October 2022. FL12034‐10 was derived from a three‐way cross LA06055SBSBSB‐79/FL11048 F1. It is well adapted across the southern United States and provides producers with a medium‐tall, mid‐season, awnless, white‐glumed, dual‐purpose oat that has high yield potential, good straw strength, and good forage yield. FL12034‐10 was observed to be uniform and stable across environments in the southern United States from 2017 to present. The line possesses a semi‐prostrate growth habit, vigorous growth, and high tillering capacity, and has large leaves that are dark green in color. It expresses moderate‐to‐high levels of resistance to most oat diseases prevalent in the southern United States. The crown and stem rust and Barley yellow dwarf virus ratings (0–9 scale) of FL12034‐10 were 1.7, 0.7, and 1.5, respectively, across different environments. The disease ratings were better than most of the checks. The grain yield average of FL12034‐10 from 41 environments during 2018–2021 was 6437 kg ha−1, which is competitive with check cultivars that are widely used in the southern part of the United States. The forage yield of FL12034‐10 ranged from 2358 to 6617 kg ha−1 (20 environments), which was higher than most of the checks. FL12034‐10 demonstrated better lodging and disease resistance, higher grain yield potential, and higher mid‐winter to late spring season forage yield potential than Horizon 720 and Legend 567 oats released by University of Florida.
Core Ideas
FL12034‐10 is well adapted across the southern United States.
FL12034‐10 is a medium‐tall, mid‐season, dual‐purpose oat cultivar.
FL12034‐10 has high yield potential, good straw strength, and good forage yield.
FL12034‐10 is semi‐prostrate in growth habit with vigorous growth and high tillering capacity.
FL12034‐10 expresses moderate to high levels of resistance to most oat diseases prevalent in the southern United States.
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