LDAS-North America Domain showing Mississippi River basin outlineMy research is directed at a variety of topics, related to large scale modeling of land surface processes. This includes investigations into forecasting and predictability, and effects of changes in land use and climate on the hydrologic response of regions.

Some specific results from this research can be found on the Publications and Presentations page.

Global Warming and Hydrology

I have been looking at several aspects of this: changing impacts of El Niño in a warming climate, uncertainty associated with differing projections of various climate models, significance of the difference between emissions pathways and impacts on water resources.

An example of the latter: by examining the performance of many climate models over California's Sacramento-San Joaquin basin, statistical analyses can be performed to show where projected changes in precipitation, streamflow, and snow, for example, are significantly greater than the uncertainty of the models themselves. Also, for some impacts, it has been found that the difference is significant between whether we choose a higher (continuing to rely on fossil fuels) or lower (transitioning to sustainable fuels) greenhouse gas emission pathway.

Another area of work relates to adapting the output from coarse scale climate models to represent better the natural spatial variability of things like precipitation and temperature. I use statistical downscaling to achieve this, and have downscaled climate model output across the U.S.

Predictability and Hydrologic Forecasting

I have looked at where runoff would be predictable at long lead times (up to a year in advance), what the sources of that predictability are, and where opportunities might lie for improving it. NASA/Goddard has posted a web summary featuring recent findings on my research on predictability, located here.

I have also examined the possibility for using radar data to decide whether precipitation is falling as rain or snow in a hydrology model. This would be aimed at improving real-time forecasts of streamflow up to 24 hours.


I am beginning to log my 15 minutes of fame, appearing on the local station KPIX (a CBS affiliate) on Aug 5, 2005, viewable online (click here to see the video clip "From above, the earth shows environmental damage").

I also stammered through the "Your Call" radio show on KALW on Aug 25, 2005 (click here for streaming audio - requires realplayer. I'm in the second half).

I'm quoted insubstantially in the Oakland Tribune on December 18, 2005.

Glennda Chui of the San Jose Mercury News included a quote from me on January 31, 2006.

I provide some commentary for the video short produced by the Union of Concerned Scientists, released May 2006.

I was quoted in two articles by Michael Moody in the Modesto Bee on October 8, 2006: Uncertain Future: Growth, climate change could spell disaster for Valley, state waterways and Early melt makes floods more likely.

I appear with my friend Al commenting on global climate change impacts on the Bay Area on TV channel 2, KTVU, on February 2, 2007. (click here for the video clip)

Data and analysis were recognized in the article "Muddy Slopes" at Sports, published March 7, 2007.

My HESS article on climate change impacts on the Rio Lempa was featured in El Faro, October 19, 2009.

I was quoted in the NY Times Green Inc. article "California Dams to Feel Impact of Climate Change," December 2, 2009.

A report on which I was a co-author was featured in Civil Engineering magazine, October 2010.

I was quoted in the San Jose Mercury News article "Taking gardening to new heights", June 10, 2011.

I provided some unfounded opinions for a piece in Life's Little Mysteries, easing our concerns about a potential extreme hydraulic event, March 23, 2012.

I wrote an op-ed with my colleague Eugene Cordero at SJ State, which was published at the Wall Street Journal's Market Watch, April 29, 2013.

As a Google Climate Science Communication Fellow in 2011, I was a co-signer to an open letter posted at Climate Science Watch on August 1, 2013, an abbreviated version of which was published at the New York Times.

I appeared in a clip, online here, related to the evolving 2014 drought on Telemundo 48 (KSTS Area de la Bahía) on January 17, 2014.

I appeared on the live Sunday morning (January 19, 2014) broadcast at KPIX 5, San Francisco, with an online video here, where the questions were also related to the drought.

I contributed to a short documentary on Santa Clara Valley water prepared by Michele Guieu for an exhibit that appears at SCU's de Saisset museum from January 17 - March 16, 2014.

KLIV radio used some of my soundbites as commentary on the May 6, 2014 release of the latest National climate Assessment report.

For the NASA/Ames OpenNex Earth Observation Data for Climate Science workshop, July 2014 I gave a keynote lecture, which can be viewed online (click Lectures in upper right to navigate to the Keynote Lectures).