2011 - Cooperative Institute for Research in Environmental Sciences ...

Milestone 1. Examine the transitional probability of
drought/pluvial conditions over the United States at different
phases of sea surface temperature (SST) evolution
in the tropical Pacific Ocean based on observational data
and multi-model ensemble simulations.
Two sets of analyses are carried out with focus on
the predictability at seasonal timescale. First, the transitional
probability of drought/pluvial conditions is
examined at various regional scales for observations;
AMIP-type (Atmospheric Model Intercomparison Project)
ensemble simulations from multiple atmospheric global
circulation models (AGCMs) forced with observed evolution
of global sea-surface temperature (SST); and the
ensemble forecasts/hindcasts from a fully coupled forecast
system with realistic initializations. The transitional
probability in the dynamic model’s simulations/forecasts
are compared to the transitional probability seen in the
observations. A diagnostic/forecast tool is developed for
probabilistic forecast of seasonal drought/pluvial conditions.
Our initial test indicates that this tool, built upon a
larger number of ensembles of dynamic model output, is
capable of producing more stable and realistic probability
forecasts than other existing forecasts that have smaller
ensemble size.
The second set of the analyses focuses on the predictability
of change of an existing meteorological drought
condition. A method is developed to combine forecasts
with the measures of existing conditions to form a universal
drought index, which gives an objective estimate
on the severity of future drought and allows for quantitative
verification. Further analyses are being pursued in
collaboration with scientists at the International Research
Institute for Climate and Society (IRI) and the Climate
Prediction Center (CPC).
Milestone 2. Evaluation of statistical and dynamical
down-scaled climate projections for the Colorado River
Basin, including data from North American Regional
Climate Change Assessment Program (NARCCAP), particularly
as it relates to hydroclimatic processes and variability.
Work with stakeholders through Western Water
Assessment, WWA, in evaluating needs and approaches
for applying regional climate change information to water
and land resource management.
Hydrologic-model runs comparing statistical and dynamical
downscaling NARCCAP methods were completed.
Work with Bureau of Reclamation researchers to complete
runs of the reservoir-operations model continues. Additionally,
scientific study to clarify some confusing modeling
results found in Reclamation’s Colorado River Basin
Study were designed, and sources of model bias are being
isolated.
A project with The Nature Conservancy and University of
Washington was initiated to calibrate Variable Infiltration
Capacity (VIC) hydrologic model for the purposes of better
modeling flows relevant to ecological applications. NARC-
CAP temperature and precipitation data over the Upper
Colorado River Basin and the San Juan Mountains were
analyzed (publication has been submitted). The team participated
in the Gunnison Basin Climate Vulnerability Group,
and climate information to assist a species- and habitat-based
vulnerability assessment was provided.
Figure 1
Milestone 3. Continue programmatic development and
impact assessments of climate, weather and water services
in conjunction with the National Integrated Drought
Information Service (NIDIS) and other programs.
The Colorado Water Availability Task Force, as well as the
Colorado Water Conservation Board (CWCB), Colorado
Basin River Forecast Center (Salt Lake City) and Upper
Colorado Assessments (NIDIS Pilot), were briefed on seasonal
to two-year expectations regarding runoff prospects
in Colorado. This was partially funded through CWCB.
Figure 2 illustrates two-year runoff behavior for naturalized
annual streamflow during long-lasting La Niña events,
as a possible scenario for the current La Niña situation.
Water managers in the southeastern U.S. (Apalachicola-
Chattahoochee-Flint basin: ACF NIDIS pilot) were briefed
on developing drought situation and linkages to La Niña.
Work continues on an ongoing project with the Department
of Water Resources in California to predict seasonal climate
in that state, with a particular focus on the Sacramento and
San Joaquin river basins. Additionally, a project with the
Bureau of Reclamation to help with its seasonal-prediction
efforts was initiated.
Figure 2
CIRES Annual Report 2011 121