The Stratospheric Extension of the Canadian Global Deterministic Medium-Range Weather Forecasting System and Its Impact on Tropospheric Forecasts

Charron, Martin; Polavarapu, Saroja; Buehner, Mark; Vaillancourt, Paul; Charette, Cécilien; Roch, Michel; Morneau, Josée; Garand, Louis; Aparicio, Josep M.; Macpherson, Stephen; Pellerin, Simon; St‐James, Judy; Heilliette, Sylvain

doi:10.1175/mwr-d-11-00097.1

Cited by 83 publications

(68 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The RDPS itself was driven by meteorological analyses generated using data assimilation. The RDPS was also used to drive a 2.5 km horizontal-resolution regional weather-only simulation, using a modified GEM High-Resolution Deterministic Prediction System configuration (HRDPS, Charron et al, 2012). Both the modified HRDPS and the 10 km resolution GEM-MACH produced 36 h simulations, the last 24 h of which were used to provide the respective meteorological and chemical boundary conditions for a 24 h GEM-MACH 2.5 km resolution simulation (which was configured with 64 vertical levels, with the underlying meteorology model operating on a 1 min time step and the chemistry module being called every second chemistry step).…”

Section: Model Setup and Configurationsmentioning

confidence: 99%

A chemical transport model study of plume-rise and particle size distribution for the Athabasca oil sands

et al. 2018

View full text Add to dashboard Cite

Abstract. We evaluate four high-resolution model simulations of pollutant emissions, chemical transformation, and downwind transport for the Athabasca oil sands using the Global Environmental Multiscale -Modelling Air-quality and Chemistry (GEM-MACH) model, and compare model results with surface monitoring network and aircraft observations of multiple pollutants, for simulations spanning a time period corresponding to an aircraft measurement campaign in the summer of 2013. We have focussed here on the impact of different representations of the model's aerosol size distribution and plume-rise parameterization on model results.The use of a more finely resolved representation of the aerosol size distribution was found to have a significant impact on model performance, reducing the magnitude of the original surface PM 2.5 negative biases 32 %, from −2.62 to −1.72 µg m −3 .We compared model predictions of SO 2 , NO 2 , and speciated particulate matter concentrations from simulations employing the commonly used Briggs (1984) plume-rise algorithms to redistribute emissions from large stacks, with stack plume observations. As in our companion paper (Gordon et al., 2017), we found that Briggs algorithms based on estimates of atmospheric stability at the stack height resulted in under-predictions of plume rise, with 116 out of 176 test cases falling below the model : observation 1 : 2 line, 59 cases falling within a factor of 2 of the observed plume heights, and an average model plume height of 289 m compared to an average observed plume height of 822 m. We used a highresolution meteorological model to confirm the presence of significant horizontal heterogeneity in the local meteorological conditions driving plume rise. Using these simulated meteorological conditions at the stack locations, we found that a layered buoyancy approach for estimating plume rise in stable to neutral atmospheres, coupled with the assumption of free rise in convectively unstable atmospheres, resulted in much better model performance relative to observations (124 out of 176 cases falling within a factor of 2 of the observed plume height, with 69 of these cases above and 55 of these cases below the 1 : 1 line and within a factor of 2 of observed values). This is in contrast to our companion paper, wherein this layered approach (driven by meteorological observations not co-located with the stacks) showed a relatively modest impact on predicted plume heights. Persistent issues with over-fumigation of plumes in the model were linked to a more rapid decrease in simulated temperature with increasing height than was observed. This in turn may have led to overestimates of near-surface diffusivity, resulting in excessive fumigation.

show abstract

Section: Model Setup and Configurationsmentioning

confidence: 99%

A chemical transport model study of plume-rise and particle size distribution for the Athabasca oil sands

et al. 2018

View full text Add to dashboard Cite

show abstract

“…As atmospheric refractivity is mostly modulated by moisture whenever the amount of water vapour is significant this is primarily a measure of irregularity in the field of water vapour. The horizontal heterogeneity in the refractivity was evaluated from the background fields of Environment Canada's operational short-term global forecasts (Charron et al, 2012), whose grid resolution is 25 km. The correlation of coherent reflections against this parameter indicates that these are indeed less frequent with more heterogeneity.…”

Section: Variablementioning

confidence: 99%

Information content in reflected signals during GPS Radio Occultation observations

2018

Self Cite

View full text Add to dashboard Cite

Abstract. The possibility of extracting useful information about the state of the lower troposphere from the surface reflections that are often detected during GPS radio occultations (GPSRO) is explored. The clarity of the reflection is quantified, and can be related to properties of the surface and the low troposphere. The reflected signal is often clear enough to show good phase coherence, and can be tracked and processed as an extension of direct non-reflected GPSRO atmospheric profiles. A profile of bending angle vs. impact parameter can be obtained for these reflected signals, characterized by impact parameters that are below the apparent horizon, and that is a continuation at low altitude of the standard non-reflected bending angle profile. If there were no reflection, these would correspond to tangent altitudes below the local surface, and in particular below the local mean sea level. A forward operator is presented, for the evaluation of the bending angle of reflected GPSRO signals, given atmospheric properties as described by a numerical weather prediction system. The operator is an extension, at lower impact parameters, of standard bending angle operators, and reproduces both the direct and reflected sections of the measured profile. It can be applied to the assimilation of the reflected section of the profile as supplementary data to the direct section. Although the principle is also applicable over land, this paper is focused on ocean cases, where the topographic height of the reflecting surface, the sea level, is better known a priori.

show abstract

“…The Canadian operational Global Deterministic Prediction System (GDPS) is composed of the GEM model and an incremental 4D-Var data assimilation system Laroche et al, 2007). The global configuration of the GEM model is characterized by a horizontal grid spacing of 33 km (exact value at 49 • N) with 80 hybrid vertical levels (terrain-following near the surface relaxing to pressure at higher altitudes) extending from the surface to 0.1 hPa (Charron et al, 2012). Analysis increments are produced on model levels on a 1.5 • horizontal grid.…”

Section: Assimilation Experimentsmentioning

confidence: 99%

An equivalent neutral wind observation operator for variational assimilation of scatterometer ocean surface wind data

Tardif¹,

Laroche²

2012

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

This article describes a new observation operator developed for improved variational data assimilation of scatterometer ocean wind vectors. The forward operator is designed explicitly to take into account the equivalent neutral calibration of scatterometer wind retrievals. The corresponding tangent linear and adjoint (TL/AD) operators are developed for the calculation of near-surface increments based explicitly on parametrizations of surface-layer turbulent momentum transfer. Tangent linear and adjoint operators are formulated using the Jacobian of the forward operator estimated using the perturbation method. Various TL/AD configurations are investigated in more detail to assess the impact of sensitivities affecting the vertical gradient of surface-layer temperature during assimilation of ocean surface wind data. It is argued that these sensitivities should be neglected in the context of a stand-alone atmospheric prediction system. The complete form of the operator has, however, the potential to be a key component of a coupled atmosphere-ocean data assimilation system. Two data assimilation experiments were performed using distinct scatterometer observation operators, i.e. new equivalent neutral versus the simpler operational configuration using stability-dependent (real) background winds. Associated medium-range forecasts were run for a complete impact assessment. The impact of the new operator is tracked through the entire data assimilation and forecast process by comparing analyses and forecasts from both experiments. A significant sensitivity of the data assimilation system to the configuration of the observation operator has been found. Modest but beneficial impacts are obtained with the equivalent neutral wind observation operator with respect to short-range forecasts of ocean surface winds and medium-range forecasts of extratropical geopotential heights.

show abstract

The Stratospheric Extension of the Canadian Global Deterministic Medium-Range Weather Forecasting System and Its Impact on Tropospheric Forecasts

Cited by 83 publications

References 40 publications

A chemical transport model study of plume-rise and particle size distribution for the Athabasca oil sands

A chemical transport model study of plume-rise and particle size distribution for the Athabasca oil sands

Information content in reflected signals during GPS Radio Occultation observations

An equivalent neutral wind observation operator for variational assimilation of scatterometer ocean surface wind data

Contact Info

Product

Resources

About