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Georg A. Grell

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Federal
Partner Affiliation
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Publon ID

Publications

Corresponding Articles: 85

Georg A. Grell authored and/or contributed to the following articles/publications.

The Inclusion of Biomass Burning in WRF-Chem: Impact of Wildfires on Weather Forecasts

A plume rise algorithm for wildfires was included in WRF-Chem, and applied to look at the impact of intense wildfires during the 2004 Alaska wildfire season on weather simulations using model resolutions of 10 km and 2 km. Biomass burning emissions were estimated using a biomass burning emissions model. In addition, a 1-D, time-dependent cloud m...

Georg A. Grell

PREP-CHEM-SRC - 1.0: a preprocessor of trace gas and aerosol emission fields for regional and global atmospheric chemistry models

The preprocessor PREP-CHEM-SRC presented in the paper is a comprehensive tool aiming at preparing emission fields of trace gases and aerosols for use in atmospheric-chemistry transport models. The considered emissions are from the most recent databases of urban/industrial, biogenic, biomass burning, volcanic, biofuel use and burning from agricul...

Georg A. Grell

Forecasting weather and air quality with online integrated modeling systems (Invited Speaker)

ntegrated modeling systems have been developed and used by the research community since the 1990's. Climate modeling centers have gone to an Earth system modeling approach that includes atmospheric chemistry and oceans. However, NWP centers, as well as entities responsible for air quality forecasting, are only now beginning to discuss whether an...

Georg A. Grell

Inclusion of Biomass Burning in WRF-Chem: Impact of Wildfires on Weather Forecasts

A plume rise algorithm for wildfires was included in WRF-Chem, and applied to look at the impact of intense wildfires during the 2004 Alaska wildfire season on weather forecasts using model resolutions of 10km and 2km. Biomass burning emissions were estimated using a biomass burning emissions model. In addition, a 1-D, time-dependent cloud model...

Georg A. Grell

Influence of ship emissions on air quality and input of contaminants in southern Alaska National Parks and Wilderness Areas during the 2006 tourist season

The impact of ship emissions on air quality in Alaska National Parks and Wilderness Areas was investigated using the Weather Research and Forecasting model inline coupled with chemistry (WRF/Chem). The visibility and deposition of atmospheric contaminants was analyzed for the length of the 2006 tourist season. WRF/Chem reproduced the meteorologi...

Georg A. Grell

The Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) - Part 1: Model description and evaluation

We introduce the Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS). CATT-BRAMS is an on-line transport model fully consistent with the simulated atmospheric dynamics. Emission sources from biomass burning and urban-industrial-vehicular activities for trace...

Georg A. Grell

Regional climate model simulation of U.S.-Mexico summer precipitation using the optimal ensemble of two cumulus parameterizations

The fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5)-based regional climate model (CMM5) simulations of U.S.–Mexico summer precipitation are quite sensitive to the choice of Grell or Kain–Fritsch convective parameterization. An ensemble based on these two parameterizations provides superior performance because distinct r...

Georg A. Grell

Satellite-observed U.S. power plant NOx emission reductions and their impact on air quality

Nitrogen oxide (NOx) emissions resulting from fossil fuel combustion lead to unhealthy levels of near-surface ozone (O3). One of the largest U.S. sources, electric power generation, represented about 25% of the U.S. anthropogenic NOx emissions in 1999. Here we show that space-based instruments observed declining regional NOx levels between 1999 ...

Georg A. Grell

Ensemble-based ozone forecasts: Skill and economic value

[1] In the summer of 2004, seven air quality models provided forecasts of surface ozone concentrations over the eastern United States and southern Canada. Accuracy of these forecasts can be assessed against hourly ozone measurements at over 350 locations. The ensemble of the air quality models is used to issue deterministic and pro...

Georg A. Grell

Effects of changing power plant NOx emissions on ozone in the eastern United States: Proof of concept

Recent decreases in nitrogen oxide (NOx = NO + NO2) emissions from eastern U.S. power plants and their effects on regional ozone are studied. Using the EPA 1999 National Emission Inventory as a reference emission data set, NOx and sulfur dioxide (SO2) emission rates at selected power plants are updated to their summer 2003 levels using Continuou...

Georg A. Grell

Effects of Surface Moisture, Land-Atmosphere Exchanges, and Turbulent Transport on Precipitation over the Rocky Mountains and High Plains

Georg A. Grell

Meteorological evaluation of a weather-chemistry forecasting model using observations from the TEXAS AQS 2000 field experiment

[1] Meteorological forecasts for the period of 25 - 30 August 2000 from a coupled weather-chemistry model are evaluated both qualitatively and quantitatively using the observations from different instruments that were deployed in metropolitan Houston during the Texas Air-Quality Study 2000 field experiment. The qualitative comparison is carried ...

Georg A. Grell

Monitoring the transport of biomass burning emissions in South America

The atmospheric transport of biomass burning emissions in the South American and African continents is being monitored annually using a numerical simulation of air mass motions; we use a tracer transport capability developed within RAMS (Regional Atmospheric Modeling System) coupled to an emission model. Mass conservation equations ar...

Georg A. Grell

A 13-KM RUC AND BEYOND: RECENT DEVELOPMENTS AND FUTURE PLANS

Georg A. Grell

Evaluation of New Trace Gas and Aerosol Modules in WRF-chem using Measurements from TexAQS 2000

Georg A. Grell

Comparisons of Model Aerosol Mass and Chemical Composition with Observations from the 2002 New England Air Quality Study

Georg A. Grell

REAL-TIME APPLICATIONS OF THE WRF MODEL AT THE FORECAST SYSTEMS LABORATORY

Georg A. Grell

Implementing the SMOKE Emissions Processing System with WRF-Chem: Progress and Early Results

Georg A. Grell

COMPARISONS BETWEEN OBSERVATIONS MADE DURING NEAQS AND AIR QUALITY FORECASTS FROM MM5 AND WRF CHEMISTRY MODELS

Georg A. Grell

The Scientific Basis of NOAA's Air Quality Forecasting Program

Georg A. Grell

A generalized approach to parameterizing convection combining ensemble and data assimilation techniques

[1] A new convective parameterization is introduced that can make use of a large variety of assumptions previously introduced in earlier formulations. The assumptions are chosen so that they will generate a large spread in the solution. We then show two methods in which ensemble and data assimilation techniques may be used to find the best valu...

Georg A. Grell

A COMPARISON OF METEOROLOGICAL OBSERVATIONS WITH THE OUTPUT OF A REAL-TIME WEATHER-CHEMISTRY FORECASTING MODEL DURING THE TEXAS AQS 2000 FIELD EXPERIMENT

Georg A. Grell

A case study comparison of 10-km WRFRUC and RUC model forecasts from the IHOP experiment

Georg A. Grell

REAL-TIME SIMULTANEOUS PREDICTION OF AIR POLLUTION AND WEATHER DURING THE HOUSTON 2000 FIELD EXPERIMENT

Georg A. Grell

RESULTS FROM THE NOAA, FSL PHOTOCHEMICAL FORECAST MODEL: COMPARISONS TO AIRCRAFT AND SURFACE DATA DURING TEXAQS-2000

Georg A. Grell

Nonhydrostatic climate simulations of precipitation over complex terrain

A climate version of the nonhydrostatic fifth-generation Penn State/NCAR Mesoscale Model has been used to downscale a global climate scenario to cloud-resolving scales over complex terrain (the Alps). After first describing the model and methodology, we then present comparison results from the model-predicted and ensemble-averaged regional-scale...

Georg A. Grell

Nonhydrostatic climate simulations of precipitation over complex terrain

A climate version of the nonhydrostatic fifth-generation Penn State/NCAR Mesoscale Model has been used to downscale a global climate scenario to cloud-resolving scales over complex terrain (the Alps). After first describing the model and methodology, we then present comparison results from the model-predicted and ensemble-averaged regional-scale...

Georg A. Grell

Application of a multiscale, coupled MM5/chemistry model to the complex terrain of the VOTALP valley campaign

A coupled complex meteorology/chemistry model has been used to simulate the how field and the concentration fields of atmospheric pollutants in Alpine valleys during the VOTALP (Vertical Ozone Transports in the ALPs) Valley Campaign in August 1996 in southern Switzerland. This paper starts with a description of a coupled numerical model (MCCM, ...

Georg A. Grell

A past and future look at the Rapid Update Cycle for the 3 May 1999 severe weather outbreak

Georg A. Grell

Using VIIRS fire radiative power data to simulate biomass burning emissions, plume rise and smoke transport in a real-time air quality modeling system

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Cascading Toward a Kilometer-Scale GCM: Impacts of a Scale-Aware Convection Parameterization in the Goddard Earth Observing System GCM

The National Aeronautics and Space Administration (NASA) Goddard Earth Observing System global circulation model (GCM) is evaluated through a cascade of simulations with increasing horizontal resolution. This model employs a nonhydrostatic dynamical core and includes a scale?aware, deep convection parameterization (DPCP). The 40?day simulations ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Use of VIIRS Aerosol Optical Depth Information at NOAA GSL to Improve Smoke, Visibility, and Weather Forecasts in the Experimental High Resolution Rapid Refresh

Recent wildfires in the U.S. and abroad have underscored the far-reaching effects that smoke from wildfires has on lives and industries, impacting air quality, aviation, solar energy generation, and more. As a result, demand has increased for reliable and accurate forecasts of smoke emanating from wildfires. To a...

Georg A. Grell

Addressing a Warm/Dry Bias over Central North America with Improved Boundary Layer and Land Surface Physics and Data Assimilation

Representing shallow cumulus in numerical weather prediction and climate models is a significant challenge. Misrepresenting these subgrid-scale clouds can result in large errors in the downwelling shortwave radiative flux at surface, resulting in large errors in the surface temperature that results in feedbacks into the accuracy of the thermodyn...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Addressing Common Cloud - Radiation Errors from ~4-hour to 4-week Model Prediction

Cloud-radiation representation in models for subgrid-scale clouds is a known gap from subseasonal-to-seasonal models down to storm-scale models applied for forecast duration of only a few hours. NOAA/ESRL has been applying common physical parameterizations for scale-aware deep/shallow convection and boundary-layer mixing over this wide range of ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Aerosol Impact on Seasonal Prediction Using FIM-Chem-iHYCOM Coupled Model

The coupled atmosphere, ocean and chemistry system using the global FIM-Chem-iHYCOM model is applied to subseasonal to seasonal prediction to investigate the aerosol impact on the atmospheric and oceanic circulation. The sources and sinks for aerosols, fire and anthripogenic emissions are prescribed. We compare the model sensitivity with various...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Inline Coupling of Simple and Complex Chemistry Modules within the Global Weather Forecast model FIM (FIM-Chem v1)

The global Flow-following finite-volume Icosahedral Model (FIM), which was developed in the Global Systems Laboratory of NOAA/ESRL, has been coupled inline with aerosol and gas-phase chemistry schemes of different complexity using the chemistry and aerosol packages from WRF-Chem v3.7, named as FIM-Chem v1. The three chemistry schemes include 1) ...

Georg A. Grell
Institutions National Oceanic and Atmospheric Administration - NOAA Earth System Research Laboratory - ESRL

How does a Pinatubo‐size Volcanic Cloud Reach the Middle Stratosphere?

Volcanic explosions are the most critical replenishing mechanism of the stratospheric aerosol Junge layer. A fresh volcanic cloud comprises mostly sulfur‐bearing gases, volcanic ash, and water vapor. It is commonly assumed that only sulfate aerosols remain in an aged volcanic cloud. Accurate simulation of the initial evolution of multicomponent ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Evaluation and intercomparison of wildfire smoke forecasts from multiple modeling systems for the 2019 Williams Flats fire

Wildfire smoke is one of the most significant concerns of human and environmental health, associated with its substantial impacts on air quality, weather, and climate. However, biomass burning emissions and smoke remain among the largest sources of uncertainties in air quality forecasts. In this study, we evaluate the smoke emissions and plume f...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Evaluation of the Grell–Freitas Convective Scheme in the Hurricane Weather Research and Forecasting (HWRF) Model

The Developmental Testbed Center (DTC) tested two convective parameterization schemes in the Hurricane Weather Research and Forecasting (HWRF) Model and compared them in terms of performance of forecasting tropical cyclones (TCs). Several TC forecasts were conducted with the scale-aware Simplified Arakawa Schubert (SAS) and Grell–Freitas (GF) co...

Georg A. Grell
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

A scale and aerosol aware stochastic convective parameterization for weather and air quality modeling

A convective parameterization is described and evaluated that may be used in high resolution non-hydrostatic mesoscale models as well as in modeling system with unstructured varying grid resolutions and for convection aware simulations. This scheme is based on a stochastic approach originally implemented by Grell and Devenyi (2002). Two approach...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

The Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA)

To explore the various couplings across space, time and between ecosystems in a consistent manner, atmospheric modeling is moving away from the fractured limited-scale modeling strategy of the past towards a unification of the range of scales inherent in the Earth System. This paper describes the forward-looking MUlti-Scale Infrastructure for Ch...

Georg A. Grell
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

WRF-Chem model sensitivity to chemical mechanisms choice in reconstructing aerosol optical properties

In the framework of the AQMEII initiative WRF-Chem has been applied over Europe adopting two chemical configurations for the calendar year 2010. The first one employed the RADM2 gas-phase chemistry and MADE/SORGAM aerosol module, while the second one implemented the CBM-Z gaseous parameterization and MOSAIC aerosol chemistry. Configurations shar...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

The Grell–Freitas (GF) convection parameterization: recent developments, extensions, and applications

Recent developments and options in the GF (Grell and Freitas, 2014; Freitas et al., 2018) convection parameterization are presented. The parameterization has been expanded to a trimodal spectral size to simulate three convection modes: shallow, congestus, and deep. In contrast to usual entrainment and detrainment assumptions, we assume that beta...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Improving dust simulations in WRF-Chem v4.1.3 coupled with the GOCART aerosol module

In this paper, we rectify inconsistencies that emerge in the Weather Research and Forecasting model with chemistry (WRF-Chem) v3.2 code when using the Goddard Chemistry Aerosol Radiation and Transport (GOCART) aerosol module. These inconsistencies have been reported, and corrections have been implemented in WRF-Chem v4.1.3. Here, we use a WRF-Ch...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

The effects of simulating volcanic aerosol radiative feedbacks with WRF-Chem during the Eyjafjallajökull eruption, April and May 2010

Explosive volcanic eruptions can inject large amounts of ash and gases into the atmosphere. Such volcanic aerosols can have a significant impact on the surrounding environment, and there is the need to closely investigate their effects on meteorology on local, regional, and even continental scale. This work presents a study of the 2010 Eyjafjall...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Building the Next Generation of Climate Modelers: Scale-Aware Physics Parameterization and the “Grey Zone” Challenge

Climate system models have typically been restricted to grid resolutions from a few hundred kilometers down to a few tens of kilometers owing to computational constraints, and a representation of subgrid physical processes by parameterization is required. The continuing advances of science and technology are allowing larger computations and high...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Assessing the Grell-Freitas Convection Parameterization in the NASA GEOS Modeling System

We implemented and began to evaluate an alternative convection parameterization for the NASA Goddard Earth Observing System (GEOS) general circulation model (GCM). The proposed parameterization follows the mass flux approach with several closures, for equilibrium and nonequilibrium convection, and includes scale and aerosol aware functionalities...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Subseasonal Forecasting with an Icosahedral, Vertically Quasi-Lagrangian Coupled Model. Part I: Model Overview and Evaluation of Systematic Errors

The atmospheric hydrostatic Flow-Following Icosahedral Model (FIM), developed for medium-range weather prediction, provides a unique three-dimensional grid structure—a quasi-uniform icosahedral horizontal grid and an adaptive quasi-Lagrangian vertical coordinate. To extend the FIM framework to subseasonal time scales, an icosahedral-grid renditi...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Evaluation of MJO Predictive Skill in Multiphysics and Multimodel Global Ensembles

Monthlong hindcasts of the Madden–Julian oscillation (MJO) from the atmospheric Flow-following Icosahedral Model coupled with an icosahedral-grid version of the Hybrid Coordinate Ocean Model (FIM-iHYCOM), and from the coupled Climate Forecast System, version 2 (CFSv2), are evaluated over the 12-yr period 1999–2010. Two sets of FIM-iHYCOM hindcas...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

A Performance Comparison between Multiphysics and Stochastic Approaches within a North American RAP Ensemble

A stochastic parameter perturbation (SPP) scheme consisting of spatially and temporally varying perturbations of uncertain parameters in the Grell–Freitas convective scheme and the Mellor–Yamada–Nakanishi–Niino planetary boundary scheme was developed within the Rapid Refresh ensemble system based on the Weather Research and Forecasting Model. Al...

Georg A. Grell
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

The Weather Research and Forecasting Model: Overview, System Efforts, and Future Directions

Since its initial release in 2000, the Weather Research and Forecasting (WRF) Model has become one of the world’s most widely-used numerical weather prediction models. Designed to serve both research and operational needs, it has grown to offer a spectrum of options and capabilities for a wide range of applications. In addition, it underlies a n...

Georg A. Grell
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

Sense size-dependent dust loading and emission from space using reflected solar and infrared spectral measurements: An observation system simulation experiment

The Climate Absolute Radiance and Refractivity Observatory (CLARREO) satellite mission observes hyperspectral Earth reflected solar (RS) and emitted infrared radiance (IR). Such measurements span an additional dimension on spectrally dependent scattering and absorption of dust, the critical signals for particle size. Through a suite of observati...

Georg A. Grell
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA

What factors control the trend of increasing AAOD over the United States in the last decade?

We examine the spatial and temporal trends of absorbing aerosol optical depth (AAOD) in the last decade over the United States (U.S.) observed by the Ozone Monitoring Instrument (OMI). Monthly average OMI AAOD has increased over broad areas of the central U.S. from 2005 to 2015, by up to a factor of 4 in some grid cells (~60 km resolution). The ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Deposition and rainwater concentrations of trifluoroacetic acid in the United States from the use of HFO-1234yf

Currently, HFC-134a (1,1,1,2-tetrafluoroethane) is the most common refrigerant in automobile air conditioners. This high global warming potential substance (100 year GWP of 1370) will likely be phased out and replaced with HFO-1234yf (2,3,3,3-tetrafluoropropene) that has a 100 year GWP of 4. HFO-1234yf will be oxidized to produce trifluoroacetic...

Georg A. Grell
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA

High-resolution smoke forecasting for the 2018 Camp Fire in California

Smoke from the 2018 Camp Fire in Northern California blanketed a large part of the region for two weeks, creating poor air quality in the “unhealthy” range for millions of people. The NOAA Global System Laboratory’s HRRR-Smoke model was operating experimentally in real time during the Camp Fire. Here, output from the HRRR-Smoke model is compared...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Summary and Recommendations on Integrated Modelling

This Chapter summaries the main discussion points arising from the topics of the workshop, namely: On-line and off-line coupling of meteorological and air quality models Implementation of feedback mechanisms, direct and indirect effects of aerosols Advanced interfaces between NWP and ACTM models Model validation studies, including air quality-re...

Georg A. Grell

A new chemistry option in WRF-Chem v. 3.4 for the simulation of direct and indirect aerosol effects using VBS: evaluation against IMPACT-EUCAARI data

A parameterization for secondary organic aerosol (SOA) production based on the volatility basis set (VBS) approach has been coupled with microphysics and radiative schemes in the Weather Research and Forecasting model with Chemistry (WRF-Chem) model. The new chemistry option called RACM-MADE-VBS-AQCHEM was evaluated on a cloud resolving scale ag...

Georg A. Grell

A North American Hourly Assimilation and Model Forecast Cycle: The Rapid Refresh

The Rapid Refresh (RAP), an hourly-updated assimilation and model forecast system, replaced the Rapid Update Cycle (RUC) as an operational regional analysis and forecast system among the suite of models at the NOAA National Centers for Environmental Prediction (NCEP) in 2012. The need for an effective hourly-updated assimilation and modeling sys...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Analyzing the Grell-Freitas convection scheme from hydrostatic to non hydrostatic scales within a global model

The authors implemented the Grell–Freitas (GF) parameterization of convection in which the cloud-base mass flux varies quadratically as a function of the convective updraft fraction in the global nonhydrostatic Model for Prediction Across Scales (MPAS). They evaluated the performance of GF using quasi-uniform meshes and a variable-resolution mes...

Georg A. Grell
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

Constraining black carbon aerosol over Asia using OMI aerosol absorption optical depth and the adjoint of GEOS-Chem

Accurate estimates of the emissions and distribution of black carbon (BC) in the region referred to here as Southeastern Asia (70–150° E, 11° S–55° N) are critical to studies of the atmospheric environment and climate change. Analysis of modeled BC concentrations compared to in situ observations indicates levels are underestimated over most of S...

Georg A. Grell

Data assimilation in atmospheric chemistry models: current status and future prospects for coupled chemistry meteorology models

Data assimilation is used in atmospheric chemistry models to improve air quality forecasts, construct re-analyses of three-dimensional chemical (including aerosol) concentrations and perform inverse modeling of input variables or model parameters (e.g., emissions). Coupled chemistry meteorology models (CCMM) are atmospheric chemistry models that...

Georg A. Grell

Distribution of sulfur aerosol precursors in the SPCZ released by continuous volcanic degassing at Ambrym, Vanuatu

The Melanesian Volcanic Arc (MVA) emits about 12 kT d− 1 of sulfur dioxide (SO2) to the atmosphere from continuous passive (non-explosive) volcanic degassing, which contributes 20% of the global SO2 emission from volcanoes. Here we assess, from up-to-date and long-term observations, the SO2 emission of the Ambrym volcano, one of the dominant vol...

Georg A. Grell

Expanding the High-Resolution Rapid Refresh (HRRR) from Deterministic to Ensemble Data Assimilation, Forecasts and Post-Processing

The 13-km Rapid Refresh (RAP) and 3-km convective-allowing High-Resolution Rapid Refresh (HRRR) are hourly updating weather forecast models that use a specially configured version of the Advanced Research WRF (ARW) model and assimilate many novel and most conventional observation types on an hourly basis using Gridpoint Statistical Interpolation...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Exploring Aerosol Effects on Rainfall for Brisbane, Australia

The majority of studies assessing aerosol effects on rainfall use coarse spatial scale (1° latitude/longitude or more) and multi-seasonal or decadal data sets. Here, we present results from a spatial correlation of aerosol size distribution and rain rate for selected stratiform and cumuliform precipitation events. The chemistry transport version...

Georg A. Grell

Building the Next Generation of Climate Modelers: Scale-Aware Physics Parameterization and the “Grey Zone” Challenge

Climate system models have typically been restricted to grid resolutions from a few hundred kilometers down to a few tens of kilometers owing to computational constraints, and a representation of subgrid physical processes by parameterization is required. The continuing advances of science and technology are allowing larger computations and high...

Georg A. Grell

Aerosol Awareness in a Convective Parameterization for Deep and Shallow Convection: Comparison to Cloud Resolving Simulations (Invited Presentation)

A convective parameterization is applied and evaluated that may be used in high resolution non-hydrostatic mesoscale models for weather and air quality prediction, as well as in modeling system with unstructured varying grid resolutions and for convection aware simulations. This scheme is based on a stochastic approach originally implemented by ...

Georg A. Grell

Implementation and initial application of new chemistry-aerosol options in WRF/Chem for simulating secondary organic aerosols and aerosol indirect effects for regional air quality

Atmospheric aerosols play important roles in affecting regional meteorology and air quality through aerosol direct and indirect effects. Two new chemistry-aerosol options have been developed in WRF/Chem v3.4.1 by incorporating the 2005 Carbon Bond (CB05) mechanism and coupling it with the existing aerosol module MADE with SORGAM and VBS modules ...

Georg A. Grell

Optimization by Firefly with Predation for Ensemble Precipitation Estimation Using BRAMS

The precipitation is predicted by using a weighted combination of different convective parameterization schemes. The best prediction estimation is obtained by calculating the appropriated weights for the ensemble of parameterizations. The weight identification process is a type of inverse problem: parameter estimation. The inverse solution is co...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

REPRESENTATION OF BOUNDARY- LAYER, RADIATION, CLOUD AND AEROSOL PROCESSES IN MESOSCALE MODELS

‘Mesoscale Modelling for Meteorological and Air Pollution Applications’ combines the fundamental and practical aspects of mesoscale air pollution and meteorological modelling. Providing an overview of the fundamental concepts of air pollution and meteorological modelling, including parameterization of key unresolved processes, the book also cons...

Georg A. Grell

Sensitivity analysis of the microphysics scheme in WRF-Chem contributions to AQMEII phase 2

The parameterization of cloud microphysics is a crucial part of fully-coupled meteorology-chemistry models, since microphysics governs the formation, growth and dissipation of hydrometeors and also aerosol cloud interactions. The main objective of this study, which is based on two simulations for Europe contributing to Phase 2 of the Air Quality...

Georg A. Grell

Sensitivity of feedback effects in CBMZ/MOSAIC chemical mechanism

To investigate the impact of the aerosol effects on meteorological variables and pollutant concentrations two simulations with the WRF-Chem model have been performed over Europe for year 2010. We have performed a baseline simulation without any feedback effects and a second simulation including the direct as well as the indirect aerosol effect. ...

Georg A. Grell

The Brazilian Global Atmospheric Model (BAM): Performance for Tropical Rainfall Forecasting and Sensitivity to Convective Scheme and Horizontal Resolution

This article describes the main features of the Brazilian Global Atmospheric Model (BAM), analyses of its performance for tropical rainfall forecasting, and its sensitivity to convective scheme and horizontal resolution. BAM is the new global atmospheric model of the Center for Weather Forecasting and Climate Research [Centro de Previsão de Temp...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

WRF-Chem Version 3.8.1 Users Guide

The WRF-Chem User's Guide is designed to provide the reader with information specific to the chemistry part of the WRF model and its potential applications. It will provide the user a description of the WRF-Chem model and discuss specific issues related to generating a forecast that includes chemical constituents beyond what is typically used by...

Georg A. Grell
Institutions National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

Coupled Chemistry-Meteorology/ Climate Modelling (CCMM): status and relevance for numerical weather prediction, atmospheric pollution and climate research

Online coupled meteorology atmospheric chemistry models have undergone a rapid evolution in recent years. Although mainly developed by the air quality modelling community, these models are also of interest for numerical weather prediction and climate modelling as they can consider not only the effects of meteorology on air quality, but also the ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

WRF/Chem Version 3.3 User's Guide

Georg A. Grell
Institutions Earth System Research Laboratory - ESRL National Center for Atmospheric Research - NCAR National Oceanic and Atmospheric Administration - NOAA

Current Challenges in Climate and Weather Research and Future Directions

This paper summarizes the current challenges in climate and weather research and provides suggestions for future research directions in global observing systems, in modelling and prediction, and in academic environment and education systems.

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Prototype of a Warn-on-Forecast System for Smoke (WoFS-Smoke)

This research begins the process of creating an ensemble-based forecast system for smoke aerosols generated from wildfires using a modified version of the National Severe Storms Laboratory (NSSL) Warn-on-Forecast System (WoFS). The existing WoFS has proven effective in generating short-term (0–3 h) probabilistic forecasts of high-impact weather ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Atmospheric Convection

Convective parameterization is the long-lasting bottleneck of global climate modelling and one of the most difficult problems in atmospheric sciences. Uncertainty in convective parameterization is the leading cause of the widespread climate sensitivity in IPCC global warming projections. This paper reviews the observations and parameterizations ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Development and evaluation of the Aerosol Forecast Member in the National Center for Environment Prediction (NCEP)'s Global Ensemble Forecast System (GEFS-Aerosols v1)

The National Oceanic and Atmospheric Administration (NOAA)'s National Weather Service (NWS) is on its way to deploying various operational prediction applications using the Unified Forecast System (https://ufscommunity.org/, last access: 18 June 2022), a community-based coupled, comprehensive Earth modeling system. An aerosol model component dev...

Georg A. Grell
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA

Impacts of estimated plume rise on PM2.5 exceedance prediction during extreme wildfire events: A comparison of three schemes (Briggs, Freitas, and Sofiev)

Plume height plays a vital role in wildfire smoke dispersion and the subsequent effects on air quality and human health. In this study, we assess the impact of different plume rise schemes on predicting the dispersion of wildfire air pollution, and the exceedances of the National Ambient Air Quality Standards (NAAQS) for fine particulate matter ...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Simulating wildfire emissions and plume rise using geostationary satellite fire radiative power measurements: a case study of the 2019 Williams Flats fire

We use the Weather Research and Forecasting with Chemistry (WRF-Chem) model with new implementations of GOES-16 wildfire emissions and plume rise based on fire radiative power (FRP) to interpret aerosol observations during the 2019 NASA-NOAA FIREX-AQ field campaign and perform model evaluations. We compare simulated aerosol concentrations and op...

Georg A. Grell
Institutions Earth System Research Laboratory - ESRL National Oceanic and Atmospheric Administration - NOAA

Evaluation of Aerosol Optical Depth Forecasts from NOAA's Global Aerosol Forecast Model (GEFS-Aerosols)

Abstract The NWS/NCEP recently implemented a new global deterministic aerosol forecast model named the Global Ensemble Forecast Systems Aerosols (GEFS-Aerosols), which is based on the Finite Volume version 3 GFS (FV3GFS). It replaced the operational NOAA Environmental Modeling System (NEMS) GFS Aerosol Component version 2 (NGACv2), which was ba...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Sensitivities of Subseasonal Unified Forecast System Simulations to Changes in Parameterizations of Convection, Cloud Microphysics, and Planetary Boundary Layer

NOAA has been developing a fully coupled Earth system model under the Unified Forecast System framework that will be responsible for global (ensemble) predictions at lead times of 0–35 days. The development has involved several prototype runs consisting of bimonthly initializations over a 7-yr period for a total of 168 cases. This study leverage...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

Heat flux assumptions contribute to overestimation of wildfire smoke injection into the free troposphere

Injections of wildfire smoke plumes into the free troposphere impact air quality, yet model forecasts of injections are poor. Here, we use aircraft observations obtained during the 2019 western US wildfires (FIREX-AQ) to evaluate a commonly used smoke plume rise parameterization in two atmospheric chemistry-transport models (WRF-Chem and HRRR-Sm...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA

A simple and realistic aerosol emission approach for use in the Thompson-Eidhammer microphysics sscheme in the NOAA UFS Weather Model (version GSL global-24Feb 2022)

A physics suite under development at NOAA's Global Systems Laboratory (GSL) includes the aerosol-aware double-moment Thompson–Eidhammer microphysics (TH-E MP) scheme. This microphysics scheme uses two aerosol variables (concentrations of water-friendly aerosol (WFA) and ice-friendly aerosol (IFA) numbers) to include interactions with some of the...

Georg A. Grell
Institution National Oceanic and Atmospheric Administration - NOAA