Research [Projects] [Publications]


pinPaleoclimate reanalysis [2014-]
The fusion of paleoclimate proxy data and climate simulations has progressed to the point where it is now possible to use data assimilation approaches similar to those used for reanalysis of weather observations during the instrumental record. Such approaches provide not only a reconstruction of the global-mean surface air temperature, but the spatial distribution and uncertainty in the temperature field, and potentially many others fields as well. In the Last Millennium Climate Reanalysis (LMR) project, we use a data assimilation approach to extend the reanalysis time period to the last 2000 years. The main goal of this project is the production of a global gridded dataset of climate fields that represents an optimal blend of information from paleoclimate proxy data (i.e. tree ring widths, ice core and coral istotopes, etc.) and climate model simulations. In a separate project, work is being done to extend the method for the reconstruction of climate states characterizing "deeper times" (Holocene, LGM, PETM etc.).

Greg Hakim, Eric Steig, Andre Perkins (University of Washington, Seattle, Washington) & Julien Emile-Geay (USC) & David Noone, Kaleb Horlick (Oregon State University) & David Anderson (Monterey Bay Aquarium Research Institute) & Jessica Tierney, Matt Osman (University of Arizona), J. Zhu, C. Poulsen (U. of Michigan), M. Li (Penn State U.)

pinOptimal design of observation network over Antarctica [2016-]
The objective of the project is to determine and validate the optimal placement of Automated Weather Stations (AWS) in Antarctica for weather and climate monitoring purposes. The analysis is performed using an ensemble sensitivity framework applied to data from the Antarctic Mesoscale Prediction System (AMPS).

Greg Hakim, Karin Bumbaco (University of Washington, Seattle, Washington) & Jordan Powers, Kevin Manning (NCAR) & Matthew Lazzara, David Mikolajczyk (University of Wisconsin at Madison)

pinAtmosphere-ocean coupled data assimilation for decadal climate prediction [2011-2014]
The overarching objective of the research is the investigation of factors limiting the predictability of decadal climate variability from the point of view of data assimilation (DA) methodologies in coupled atmosphere-ocean climate prediction systems. The research is performed within the framework of NCAR's Data Assimilation Research Testbed (DART) Ensemble Kalman Filter (EnKF) DA system and involves a hierarchy of atmospheric and ocean models, including ultimately the Model for Prediction Across Scales (MPAS).

Greg Hakim (University of Washington, Seattle, Washington) & Chris Snyder (NCAR/MMM, Boulder, Colorado)

pinImproved assimilation of scatterometer ocean surface wind vectors in an operational NWP system [2008-2011]
The research aimed at providing enhancements to analyses and forecasts of surface winds over the global ocean through improvements in the assimilation of scatterometer (SeaWinds onboard QuikSCAT and ASCAT onboard MetOp-A) data into a NWP model. A novel forward observation operator was developed which takes explicitly into account the equivalent neutral calibration of scatterometer winds. The corresponding tangent linear model and its adjoint were developed and tested into the Canadian Global Deterministic Prediction System 4D-var assimilation system. Results showed that a subtle change in the definition of the surface layer wind observation operator induces changes to analyses and leads to modest improvements in medium-range forecasts of the global atmosphere.

Stéphane Laroche, Judy St-James & Mateusz Reszka (Environment Canada, Dorval, Canada)

pinObservation analysis and mesoscale numerical modeling of fog events [2007-2008]
The research focused on (1) an analysis of observations gathered during the six-month ParisFog field experiment to provide an overall characterization of events observed during the campaign, (2) the characterization of fog events at the Paris/Charles de Gaulle airport to support an enhanced evaluation of a fog and low cloud local ensemble prediction system and (3) an assessment of the capability of a 3D mesoscale NWP model at reproducing the spatio-temporal variability of the fog life cycle in a heterogeneous environment. Research results have shown that the fog phenomenon in the Paris area is mainly composed of radiation and stratus lowering events, both resulting from subtle changes in environmental conditions. Also, it was demonstrated that the Méso-NH mesoscale model is able to represent the complete life cycle of a fog event and its mesoscale spatial variability around Paris, provided that sufficient vertical resolution is used. Given fixed computing resources, fog features around the Paris area were better represented with a horizontal resolution of 10 km in combination with an increased vertical resolution (order of 1 m near the surface) rather than using a standard vertical resolution of 10 m to few tens of meters and increasing the horizontal resolution to kilometer and sub-kilometer-scales.

Thierry Bergot & Stevie Roquelaure (Météo-France/CNRM, Toulouse, France) & Martial Haeffelin (Institut Pierre-Simon Laplace, École Polytechnique, Palaiseau, France)

pinFog physical processes in the New York City area [2001-2007]
The research produced an original characterization of the fog phenomenon and greater understanding of the physical processes leading to fog formation in the New York City area. The project involved a field phase with the deployment of a suite of sensors at the site of the meteorological tower of the Brookhaven National Laboratory (BNL). The research relied on the analysis of observations and the development of a microphysical rainfall model to study the role of evaporation of non-equilibrium raindrop in frontal inversions as an important mechanism contributing to the often-observed formation of fog within precipitating synoptic scale weather systems.

Roy Rasmussen & Paul Herzegh (NCAR/RAL, Boulder, Colorado)

pinShort-term forecasting of atmospheric conditions over airports with a single column numerical model [1993-2001]
Research and development (R&D) efforts were performed to develop a local-scale short-term prediction system designed to provide accurate nowcasts of atmospheric over North-American airports. The Code Brouillard à l'Echèlle Locale (COBEL) single column model, originally developed by Météo-France/CNRM and the Laboratoire d'Aérologie in Toulouse France, was further developed through the addition of external forcings, physical parameterizations and adapted initialization modules for comprehensive nowcasting of fog and marine stratus, as well as wind profiles for wake vortex environment prediction. The highlight of this R&D is the development of a module of the Marine Stratus Burn-Off Forecast System now operational at the San Francisco International Airport.

Collaborators: Peter Zwack (UQÀM, Montréal, Canada), Wes Wilson, Dave Clark, Frank Robasky (MIT/Lincoln Laboratory, Lexington Massachusetts) & Doug Sinton (San Jose State University, San Jose, California)


Marzban, C, R. Tardif, S. Sandgathe, 2019: A sensitivity analysis of two mesoscale models: COAMPS and WRF. Mon. Wea. Rev., 148(7), 2997–3014. doi: 10.1175/MWR-D-19-0271.1 [link]

Marzban, C, R. Tardif, S. Sandgathe, 2020: Sensitivity analysis of the spatial structure of forecasts in mesoscale models: Noncontinuous model parameters. Mon. Wea. Rev., 148(4), 1717–1735, doi: 10.1175/MWR-D-19-0321.1. [link]

Hakim, G. J., K. Bumbaco, R. Tardif, J. Powers, 2020: Optimal network design applied to monitoring and forecasting temperature in Antarctica. Mon. Wea. Rev., 148(2), 857–873, doi: 10.1175/MWR-D-19-0103.1. [link]

Tardif, R., G. J. Hakim, W. A. Perkins, K. A. Horlick, M. P. Erb, J. Emile-Geay, D. M. Anderson, E. J. Steig and D. Noone, 2019: Last Millennium Reanalysis with an expanded proxy database and seasonal proxy modeling. Clim. Past., 15, 1251-1273, doi:10.5194/cp-15-1251-2019. [link]

Anderson, D. M., R. Tardif, K. Horlick, M. P. Erb, G. J. Hakim, D. Noone, W. A. Perkins, E. J. Steig, 2019: Additions to the Last Millennium Reanalysis multi-proxy database (LMRdb v1.0.0). Data Science Journal, 18(1), doi:10.5334/dsj-2019-002 [link]

Marzban, C., R. Tardif, N. Hryniw, S. Sandgathe, 2019: A methodology for sensitivity analysis of spatial features in forecasts: The Stochastic Kinetic Energy Backscatter Scheme. Met. App., 26(3), 454-467, doi:10.1002/met.1775. [link]

Singh, H.K.A., Hakim, G. J., R. Tardif, J. Emile-Geay, D. Noone, 2018: Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework. Clim. Past., 14 (2), 157-174, doi:10.5194/cp-14-157-2018 [link]

Tardif, R., 2017: Precipitation and Fog. Book chapter in Koracin, D., and C. E. Dorman, eds. Marine Fog: Challenges and Advancements in Observations and Forecasting. Springer Publ. [link]

Hakim, G. J., J. Emile-Geay, E. J. Steig, D. Noone, D. A. Anderson, R. Tardif, N. Steiger, W. A. Perkins, 2016: The Last Millennium Climate Reanalysis project: Framework and first results. JGR (Atmospheres), 121 (12), 6745-6764, doi: 10.1002/2016JD024751, [link]

Tardif, R., G. J. Hakim and C. Snyder, 2015: Coupled atmosphere-ocean data assimilation experiments with a low-order model and CMIP5 model data. Climate Dyn., 45 (5-6), 1415-1627, doi:10.1007/s00382-014-2390-3. [link]

Tardif, R., G. J. Hakim and C. Snyder, 2014: Coupled atmosphere-ocean data assimilation experiments with a low-order climate model. Climate Dyn., 43 (5-6), 1631-1643, doi:10.1007/s00382-013-1989-0. [link]

Tardif, R. and S. Laroche, 2012: An equivalent neutral wind observation operator for variational assimilation of scatterometer ocean surface wind data. Quart. J. Roy. Meteor. Soc., 138, 2086-2104. [link]

Haeffelin, M., T. Bergot, T. Elias, R. Tardif, D. Carrer, P. Chazette, M. Colomb, P. Drobinski, E. Dupont, J-C. Dupont, L. Gomes, L. Musson-Genon, C. Pietras, A. Plana-Fattori, A. Protat, J. Rangognio, J-C. Raut, S. Rémy, D. Richard, J. Sciare, and X. Zhang, 2010: ParisFog, shedding new light on fog physical processes. Bull. Amer. Meteor. Soc., 91(6), 767-783. [link]

Tardif, R., and R. M. Rasmussen, 2010: Evaporation of non-equilibrium raindrops as a fog formation mechanism. J. Atmos. Sci., 67(2), 345-364. [link]

Roquelaure, S., R. Tardif, S. Rémy and T. Bergot, 2009: Skill of a ceiling and visibility Local Ensemble Prediction System (L-EPS) according to fog-type prediction at Paris International Airport. Wea. Forecasting, 24(6), 1511-1523 [link]

Bergot, T., M. Haeffelin, L. Musson-Genon, R. Tardif, and co-authors, 2008: Paris-Fog: des chercheurs dans le brouillard. La Météorologie, 62, 48-58. [pdf]

Tardif, R., and R. M. Rasmussen, 2008: Process-oriented analysis of environmental conditions associated with precipitation fog events in the New York City region. J. Appl. Meteor. Climatol., 47, 1681-1703. [link]

Tardif, R.
, and R. M. Rasmussen, 2007: Event-based climatology and typology of fog in the New York City region.  J. Appl. Meteor. Climatol.,
46, 1141-1168. [link]

Tardif, R., 2007: The impact of vertical resolution in the explicit numerical forecasting of radiation fog: A case study. Pure Appl. Geophys. , 164, 1221-1240. [link]

Gultepe, I., R. Tardif, S. C. Michaelides, J. Cermak, A. Bott, J. Bendix, M. D. Müller, M. Pagowski, B. K. Hansen, G. P. Ellrod, W. Jacobs, G. Toth, and S. Cober, 2007: Fog research: A review of past achievements and future perspectives. Pure Appl. Geophys. , 164, 1121-1159. [link]

Ph.D. Dissertation

Characterizing Fog and the Physical Mechanisms Leading to its Formation during Precipitation in a Coastal Area of the Northeastern United States. University of Colorado at Boulder, 2007. [pdf]

International Conferences & Workshops

Tardif, R., S. Laroche, M. Reszka, and J. St-James, 2011: An equivalent neutral wind observation operator for the variational assimilation of scatterometer ocean surface wind data. EUMETSAT/ESA Scatterometer Science Conference, Darmstadt, Germany. [pdfsoon...]

Reszka, M., R. Tardif, J. St-James and S. Laroche, 2011: ASCAT scatterometer winds at MSC: Recent improvements in quality control and assimilation procedures. EUMETSAT/ESA Scatterometer Science Conference, Darmstadt, Germany. [pdfsoon...]

Cotton, J., R. Tardif, H. Hersbach, D. Offiler and B. Conway, 2011: NWP SAF scatterometer monitoring. Poster for NWP SAF Scatterometer Data Assimilation Workshop, Darmstadt, Germany. [pdf]

Tardif, R.,
M. Reszka, S. Laroche and J. St-James, 2010: Improving scatterometer ocean wind vector data assimilation in Environment Canada's global variational analysis and forecast system. 17th Conference on Satellite Meteorology and Oceanography, Annapolis, MD. [pdf]

Tardif, R., S. Laroche, M. Reszka and J. St-James, 2010: Status of Scatterometer Ocean Wind Vector Data Assimilation in Environment Canada's Global Variational Analysis and Forecast System (talk), 1st International Ocean Vector Wind Science Team meeting , Barcelona, Spain [pdf]

Reszka, M, S. Laroche, R. Tardif, and J. St-James, 2009: Assimilation of ASCAT scatterometer winds in the MSC analysis system. 43rd Congress of the Canadian Meteorological and Oceanographic Society, Halifax, Nova Scotia. [link]

Tardif, R., 2006: Some results from a sounding enhanced observing period focused on low ceiling and visibility in the northeastern United States. 12th Conference on Aviation, Range and Aerospace Meteorology, Atlanta, GA. [pdf]

Tardif, R., 2006: A climatological study of low ceiling and fog events associated with the occurrence of precipitation in the northeastern United States. 12th Conference on Aviation, Range and Aerospace Meteorology, Atlanta, GA. [pdf]

Landolt, S. D., R. Tardif and P. H. Herzegh, 2006: A comparison of atmospheric profiles using a twelve channel microwave profiling radiometer and radiosondes during low ceiling events. 12th Conference on Aviation, Range and Aerospace Meteorology, Atlanta, GA. [pdf]

Tardif, R., 2004: Characterizing fog occurrences in the Northeastern United States using historical data. 11th Conference on Aviation, Range and Aerospace Meteorology, Hyannis Port, MA. [pdf]

Tardif, R., J. Cole, P. H. Herzegh, S. D. Landolt, R. M. Rasmussen and M. L. Tryhane, 2004: First observations of fog and low ceiling environments at the FAA northeast ceiling and visibility field site. 11th Conference on Aviation, Range and Aerospace Meteorology, Hyannis Port, MA. [pdf]

Tardif, R., 2004: On the impact of vertical resolution in the numerical forecasting of fog. 11th Conference on Aviation, Range and Aerospace Meteorology, Hyannis Port, MA. [pdf]

Landolt, S. D., R. Tardif and P. H. Herzegh, 2004: A case study of thermodynamic profile retrieval using a microwave radiometer at vertical and off-vertical incidence. 11th Conference on Aviation, Range and Aerospace Meteorology, Hyannis Port, MA. [pdf]

Invited Talks

"Understanding precipitation fog: fundamental research using field observations and numerical modeling". 2nd Fog Remote Sensing and Modeling (FRAM) workshop, May 2008, Dalhousie Univ., Halifax, Canada. [ppt]

"Fog field experiments in France, from ParisFog to ToulouseFog: goals, and description of the observations".Co-author with Thierry Bergot. 2nd Fog Remote Sensing and Modeling (FRAM) workshop, May 2008, Dalhousie Univ., Halifax, Canada. [ppt]

"Characterizing the Response of Simulated Atmospheric Boundary Layers to Stochastic Cloud Radiative Forcing",
NCAR/Institute for Mathematics Applied to Geosciences (IMAGe) and Statistics and Applied Mathematics Sciences Institute (SAMSI) Workshop on Applications of Statistics to Numerical Models, May 2007, NCAR, Boulder, Colorado.

"Fog and Low Cloud Ceilings in the Northeastern United States: Climatology and Dedicated Field Study". Fog Remote Sensing and Modeling (FRAM) workshop, June 2005, UQAM, Montré
al, Canada. [ppt]

"Some Research and Development Activities Toward the Improvement of Short-Term Forecasts of Low Ceiling and Reduced Visibility (C&V) Conditions in the United States". COST 722 Expert Meeting, October 2004, Météo-France, Toulouse, France. [ppt]

Miscellaneous Documents
Tardif, R., 2009: Enhancements to the assimilation of scatterometer ocean surface wind vectors in Environment Canada's global forecast system: A review of issues. Internal Report, Environment Canada. [pdf]
Tardif, R., 2006: Calibration procedure of the Droplet Measurement Technologies' FM-100 fog droplet spectrometer and history of calibration tests. [pdf]
Tardif, R.
, 2005: Fog and low cloud ceiling environments observed during the Long Island Fog Regimes (LIFR) field program.
Tardif, R., 2003: Field calibration of the ECH2O soil moisture probes. [pdf]
Tardif, R., 2003: A preliminary numerical sensitivity analysis of marine fog formation under conditions observed in the northeastern United States using the COBEL 1D model. [pdf]
Tardif, R., 2002: A numerical sensitivity study of the boundary layer evening transition to the direct radiative effects of lower tropospheric aerosols. [pdf]
Tardif, R., 2002: Boundary layer aerosol backscattering and its relationship to relative humidity from a combined Raman-elastic backscatter lidar. [pdf]
Tardif, R., 2001: Dew and frost deposition and their role in the regulation of radiation fog onset: a numerical sensitivity study. [pdf]
Tardif, R., M. Beauchemin, P. Zwack and J. L. Keller, 1996: The COBEL model as part of a terminal area Ceiling & Visibility (C&V) nowcast system: A progress report.  Project Report ATC-241, Lincoln Laboratory, Massachusetts Institute of Technology. [pdf]