Leah J. Welty
   Postdoctoral Fellow
   Johns Hopkins Bloomberg School of Public Health
   Department of Biostatistics

   CV (pdf)
   Contact
   Research Interests
   Publications
   Presentations
   Software
   Dissertation


Contact:

 Leah J. Welty                                                                Phone: 410-614-7837
 Johns Hopkins Department of Biostatistics             Fax: 410-955-0958
 615 N. Wolfe Street
 Baltimore, MD 21205                                              
 lwelty@jhsph.edu

Research Interests:

Applications of statistics to medical and environmental sciences.  In particular, health effects of air pollution and weather, spatial statistics, time series, distributed lag models, and combining physical and statistical models.

Publications:

To appear:

Welty, L. and Zeger, S. ``Are the Acute Effects of PM10 on Mortality in NMMAPS the Result of Inadequate Control for Weather and Season?  A Sensitivity Analysis using Flexible Distributed Lag Models.'' American Journal of Epidemiology, to appear. Technical Report.

Submitted:

Welty, L., Stein M., Lesht, B., Vanderploeg, H. and Johengen, T. ``A Quantitative Correction for Non-Photochemical Quenching in the Calibration of Chlorophyll Fluorescence to Chlorophyll a Concentration, Applied to Lake Michigan.'' Technical Report.

Peng, R. and Welty, L. ``The National Morbidity, Mortality, and Air Pollution Study Database in R." Technical Report.

2004:

Peng, R. and Welty, L. ``The NMMAPSdata Package'' (2004) R News, 4/2, 10-14.  Article

Stein, M., Chi, Z., Welty, L. ``Approximating the Likelihood for Irregularly Observed Gaussian Random Fields.'' (2004) JRSS B, 66, 275-296.

Welty, L. J., Stein, M. L. ``Modeling Phytoplankton: Covariance and Variogram Model Specification for Phytoplankton Levels in Lake Michigan.'' (2004) geoENV IV -- Geostatistics for Environmental Applications, 163 - 174.

2002:

Lesht, B. M., Stroud, J. R., McCormick, M. J., Fahnenstiel, G. L., Stein, M. L., Welty, L. J. and Leshkevich, G. A. ``An event-driven phytoplankton bloom in southern Lake Michigan observed by satellite.'' (2002) Geophysical Research Letters, 29, 013533.


Presentations:

UCHS 2005     Time Series Studies of Air Pollution and Mortality:  Confounding and Cumulative Effects  pdf

NU 2004           Time Series Studies of Air Pollution and Mortality:  Confounding, Control, and Cumulative Effects pdf

JSM 2004        An Application of Approximate Likelihood Methods to Interpolate Lake Michigan Algae Levels pdf

ISEE 2004       Flexible Distributed Lag Models:  Are the Acute Effects of PM10 on Mortality the Result of Inadequate Control for Weather and Season?  (version 2)  pdf

WNAR 2004    A Bayesian Formulation for Distributed Lag Models:  Mortality Displacement from PM10 pdf

NCAR 2004     Flexible Distributed Lag Models:  Are the Acute Effects of PM10 on Mortality the Result of Inadequate Control for Weather and Season? (version 1)  pdf

JHSPH 2003   Spatial Statistics for Modeling Phytoplankton pdf

GLERL 2003   Calibrating In Situ Fluorescence to Chlorophyll Concentration pdf


Software:

NMMAPSdata R package (includes links to programs for estimating distributed lag models)


Dissertation:

Title: Spatial Statistics for Modeling Phytoplankton pdf

          Advisor: Michael L. Stein, Professor, University of Chicago Department of Statistics

Summary:  Interpolating chlorophyll levels using irregularly spaced observations from multiple measurement sources.  Investigating covariance models for badly anisotropic data, modeling measurement bias, and estimating parameters through approximate restricted maximum likelihood techniques.


Last updated February 2005.