72 research outputs found
Meteorology for scientists and engineering/ Stull
xvi, 502 hal.:ill.; 28 cm
Practical Meteorology : An Algebra-based Survey of Atmospheric Science
In this book are five major components of meteorology:
(1) thermodynamics, (2) physical meteorology,
(3) observation and analysis, (4) dynamics,
and (5) weather systems (cyclones, fronts, thunderstorms).
Also covered are air-pollution dispersion,
numerical weather prediction, and natural climate
processes.Earth, Ocean and Atmospheric Sciences, Department ofScience, Faculty ofReviewedFacult
Capturing Plume Rise and Dispersion with a Coupled Large-Eddy Simulation: Case Study of a Prescribed Burn
Current understanding of the buoyant rise and subsequent dispersion of smoke due to wildfires has been limited by the complexity of interactions between fire behavior and atmospheric conditions, as well as the uncertainty in model evaluation data. To assess the feasibility of using numerical models to address this knowledge gap, we designed a large-eddy simulation of a real-life prescribed burn using a coupled semi-emperical fireâatmosphere model. We used observational data to evaluate the simulated smoke plume, as well as to identify sources of model biases. The results suggest that the rise and dispersion of fire emissions are reasonably captured by the model, subject to accurate surface thermal forcing and relatively steady atmospheric conditions. Overall, encouraging model performance and the high level of detail offered by simulated data may help inform future smoke plume modeling work, plume-rise parameterizations and field experiment designs.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofReviewedFacult
Wet-Bulb Temperature from Relative Humidity and Air Temperature.
An equation is presented for wet-bulb temperature as a function of air temperature and relative humidity at standard sea level pressure. It was found as an empirical fit using gene-expression programming. This equation is valid for relative humidities between 5% and 99% and for air temperatures between â20° and 50°C, except for situations having both low humidity and cold temperature. Over the valid range, errors in wet-bulb temperature range from â1° to +0.65°C, with mean absolute error of less than 0.3°C.
Copyright 2011 American Meteorological Society (AMS). Permission
to use figures, tables, and brief excerpts from this work in scientific and educational
works is hereby granted provided that the source is acknowledged. Any use of material in
this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act
or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17
USC §108, as revised by P.L. 94-553) does not require the AMSâs permission.
Republication, systematic reproduction, posting in electronic form, such as on a web site
or in a searchable database, or other uses of this material, except as exempted by the
above statement, requires written permission or a license from the AMS. Additional
details are provided in the AMS Copyright Policy, available on the AMS Web site
located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
[email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult
Kalman Filter and Analog Schemes to Postprocess Numerical Weather Predictions.
Two new postprocessing methods are proposed to reduce numerical weather predictionâs systematic and random errors. The first method consists of running a postprocessing algorithm inspired by the Kalman filter (KF) through an ordered set of analog forecasts rather than a sequence of forecasts in time (ANKF). The analog of a forecast for a given location and time is defined as a past prediction that matches selected features of the current forecast. The second method is the weighted average of the observations that verified when the 10 best analogs were valid (AN). ANKF and AN are tested for 10-m wind speed predictions from the Weather Research and Forecasting (WRF) model, with observations from 400 surface stations over the western United States for a 6-month period. Both AN and ANKF predict drastic changes in forecast error (e.g., associated with rapid weather regime changes), a feature lacking in KF and a 7-day running-mean correction (7-Day). The AN almost eliminates the bias of the raw prediction (Raw), while ANKF drastically reduces it with values slightly worse than KF. Both analog-based methods are also able to reduce random errors, therefore improving the predictive skill of Raw. The AN is consistently the best, with average improvements of 10%, 20%, 25%, and 35% with respect to ANKF, KF, 7-Day, and Raw, as measured by centered root-mean-square error, and of 5%, 20%, 25%, and 40%, as measured by rank correlation. Moreover, being a prediction based solely on observations, AN results in an efficient downscaling procedure that eliminates representativeness discrepancies between observations and predictions.
Copyright 2011 American Meteorological Society (AMS). Permission
to use figures, tables, and brief excerpts from this work in scientific and educational
works is hereby granted provided that the source is acknowledged. Any use of material in
this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act
or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17
USC §108, as revised by P.L. 94-553) does not require the AMSâs permission.
Republication, systematic reproduction, posting in electronic form, such as on a web site
or in a searchable database, or other uses of this material, except as exempted by the
above statement, requires written permission or a license from the AMS. Additional
details are provided in the AMS Copyright Policy, available on the AMS Web site
located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
[email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult
Mesoscale Analysis Method for Surface Potential Temperature in Mountainous and Coastal Terrain
A technique is developed to anisotropically spread surface observations in steep valleys. The goal is to
create an improved objective analysis for the lowest, terrain-following numerical weather prediction (NWP)
model level in mountainous terrain.
The method is a motherâdaughter (MD) approach, where the amount of information transferred from
one grid point (the mother) to all neighboring grid points (the daughters) depends on elevation differences.
The daughters become mothers and further share information with their neighboring grid points. This
iterative method allows information to follow valleys around ridges, while reducing spread over the ridge
top. The method is further refined to account for landâsea anisotropy.
This approach is tested in the objective analyses of surface potential temperatures over the steep mountainous
and coastal terrain of southwestern British Columbia, Canada. Analysis results are compared with
other existing schemes using the Advanced Regional Prediction System Data Assimilation System (ADAS).
It is found that the MD approach outperforms the other schemes over mountainous and coastal terrain. Copyright 2005 American Meteorological Society (AMS). Permission
to use figures, tables, and brief excerpts from this work in scientific and educational
works is hereby granted provided that the source is acknowledged. Any use of material in
this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act
or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17
USC §108, as revised by P.L. 94-553) does not require the AMSâs permission.
Republication, systematic reproduction, posting in electronic form, such as on a web site
or in a searchable database, or other uses of this material, except as exempted by the
above statement, requires written permission or a license from the AMS. Additional
details are provided in the AMS Copyright Policy, available on the AMS Web site
located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
[email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult
Forecasting Sun versus Shade in Complex Terrain for the 2010 Winter Olympic and Paralympic Games.
Howard, Rosie; Stull, Roland B. 2011.
Forecasting Sun versus Shade in Complex Terrain for the 2010 Winter Olympic and Paralympic Games.
Bulletin of the American Meteorological Society, 92 (10), 1303-1309
http://dx.doi.org/10.1175/2011BAMS-D-11-00017.1
During the 2010 Vancouver Winter Olympic and Paralympic Games in Canada, there were 10 mostly sunny days at the outdoor Olympic venues. The warmth and sunshine, possibly a result of El Niño conditions at the time, significantly reduced snow cover at one venue and weakened the snowpack at the other two venues, much to the chagrin of the event organizers. Solar radiation affects ski racing via its effect on snow-surface friction, abrasion, and mechanical strength. Ski technicians and athletes compensate via the choice of ski and wax. For these reasons, sun-versus-shade forecasts were produced for Canadian ski and snowboard teams.
A theodolite was used to survey the horizon elevation angles around the full azimuth circles at 133 locations spaced roughly 150 m apart along race pistes (compacted ski runs) at three Olympic venues. This survey was important for including the shadowing effects of the tall evergreen trees that border the pistes. This would not be properly accounted for if only digital elevation data were used. These data, along with the astronomical equations for solar elevation and azimuth, were used to calculate whether each survey point would be in the sun or the shade in cloudless conditions for any time and date during the Olympics. Half-hourly output was provided to ski and snowboard technicians and coaches via a graphical user interface delivered on the Internet.
Copyright 2011 American Meteorological Society (AMS). Permission
to use figures, tables, and brief excerpts from this work in scientific and educational
works is hereby granted provided that the source is acknowledged. Any use of material in
this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act
or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17
USC §108, as revised by P.L. 94-553) does not require the AMSâs permission.
Republication, systematic reproduction, posting in electronic form, such as on a web site
or in a searchable database, or other uses of this material, except as exempted by the
above statement, requires written permission or a license from the AMS. Additional
details are provided in the AMS Copyright Policy, available on the AMS Web site
located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
[email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult
Reply to Arya, S. P., 1999: Comments on âWind and temperature profiles in the radix layer: The bottom fifth of the convective boundary layer.â J. Appl. Meteor.,38, 493â494.
We thank Arya (1999) for his comments regarding
the radix layer (RxL) wind profile equation. Surfacelayer power laws (SLPLs) of the form of Aryaâs Eq. (1) have indeed enjoyed a long and successful history in engineering applications. As Arya mentions, these SLPLs have not had the strong theoretical underpinning associated with the MoninâObukhov similarity theory, which also works best in only a shallow region at the bottom of the boundary layer. Copyright 1999 American Meteorological Society (AMS). Permission
to use figures, tables, and brief excerpts from this work in scientific and educational
works is hereby granted provided that the source is acknowledged. Any use of material in
this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act
or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17
USC §108, as revised by P.L. 94-553) does not require the AMSâs permission.
Republication, systematic reproduction, posting in electronic form, such as on a web site
or in a searchable database, or other uses of this material, except as exempted by the
above statement, requires written permission or a license from the AMS. Additional
details are provided in the AMS Copyright Policy, available on the AMS Web site
located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
[email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult
Assimilating Surface Weather Observations from Complex Terrain into a High-Resolution Numerical Weather Prediction Model.
An anisotropic surface analysis method based on the motherâdaughter (MD) approach has been developed
to spread valley station observations to grid points in circuitous steep valleys. In this paper, the MD
approach is further refined to allow spreading the mountain-top observations to grid points near neighboring
high ridges across valleys. Starting with a 3D first guess from a high-resolution mesoscale model
forecast, surface weather observations are assimilated into the boundary layer, and pseudo-upper-air data
(interpolated from the coarser-resolution analyses from major operational centers) are assimilated into the
free atmosphere. Incremental analysis updating is then used to incorporate the final analysis increments (the
difference between the final analysis and the first guess) into a high-resolution numerical weather prediction
model. The MD approaches (including one with shoreline refinement) are compared with other objective
analysis methods using case examples and daily mesoscale real-time forecast runs during November and
December 2004. This study further confirms that the MD approaches outperform the other methods, and
that the shoreline refinement achieves better analysis quality than the basic MD approach. The improvement
of mountain-top refinement over the basic MD approach increases with the percentage of mountaintop
stations, which is usually low. Higher skill in predicting near-surface potential temperature is found
when surface information is spread upward throughout the boundary layer instead of at only the bottom
model level. The results show improved near-surface forecasts of temperature and humidity that are directly
assimilated into the model, but poorer forecasts of near-surface winds and precipitation, which are not
assimilated into the model. Copyright 2007 American Meteorological Society (AMS). Permission
to use figures, tables, and brief excerpts from this work in scientific and educational
works is hereby granted provided that the source is acknowledged. Any use of material in
this work that is determined to be âfair useâ under Section 107 of the U.S. Copyright Act
or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17
USC §108, as revised by P.L. 94-553) does not require the AMSâs permission.
Republication, systematic reproduction, posting in electronic form, such as on a web site
or in a searchable database, or other uses of this material, except as exempted by the
above statement, requires written permission or a license from the AMS. Additional
details are provided in the AMS Copyright Policy, available on the AMS Web site
located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or
[email protected], Faculty ofEarth and Ocean Sciences, Department ofReviewedFacult
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