PNNL-13501 - Pacific Northwest National Laboratory

wide variety of parallel computing platforms using twodimensional
decomposition with shared or distributed
memory. This effort also contributes toward the
development of a community regional climate model
based on MM5.
Figure 1 shows the speedup attained with the twodimensional
decomposition parallel version of MM5 with
and without subgrid orographic precipitation. Results are
based on benchmarks on the EMSL IBM-SP computer. A
number of 1-day simulations have been performed using
different configurations of the model domain. Higher
speedup is achieved with larger domain sizes. When the
subgrid orographic precipitation scheme is applied, a
simple load-balancing algorithm is needed to improve the
performance. Figure 2 shows the two-dimensional
domain decomposition when the load-balancing algorithm
is applied. Because computational burden increases with
an increasing number of subgrid elevation bands, smaller
domains are assigned to processors that are required to
handle a larger number of subgrid elevation bands.
Speed-up
100
10
B Perfect parallelization
J L-domain (200x200x23) B
H M-domain (70x70x23)
J
F S-domain (37x37x23)
B S-domain (subgrid + load bal) B H
J S-domain (subgrid, no load bal) J
H
B J
H
F
F
B JH
F
B B
F B J J
B J
J
B B J
JH
H F
B F
B J
J
1
1 10
Number of processors
100
Figure 1. Speedup of the two-dimensional decomposition
parallel RCM on the PNNL EMSL IBM-SP machine.
Results are based on 1-day simulations with the RCM
applied to different geographical domains.
Hydrologic Modeling
Assessments of fisheries management conducted by
various federal, state, and tribal agencies (including
Bonneville Power Administration) are driven to the
spatial scale of the 6th-level Hydrologic Unit Code
(HUC6). The channel system in each hydrologic unit
code is subdivided into a number of geo-referenced river
1 2 3 4 5 6 7 8 9 10 11 12
number of subgrid bands per grid
Figure 2. Two-dimensional domain decomposition when the
PNNL subgrid orographic precipitation is applied. Smaller
domains are assigned to processors that cover regions with a
large number of subgrid elevation bands.
reaches. More than 7500, 6th-level hydrologic unit codes
exist in the Columbia Basin, of which less than 1% has
gauged streamflows. The Distributed Hydrology-Soil-
Vegetation Model has been enhanced to operate either on
the original square-grid domain or a more generic
watershed/channel representation that allows direct
application at the HUC6 level. Linkage with the
Laboratory’s regional climate model has been maintained.
Support utilities have been developed to subdivide each
HUC6 into elevation bands with a simplified
representation of subband topography. Each band is
mapped to the appropriate River Reach(s). The model is
currently being run for the entire Columbia River basin at
the HUC6 level using five elevation bands per hydrologic
unit code.
Development of a Hydrosystem Management Tool
The developments under the hydrology task enable us to
provide estimates of natural streamflows. However, dams
and diversions significantly alter these natural streamflow
patterns. Any adaptation to changes in the future climate
will involve changes to the operating policies of dams and
diversions. A numerical procedure to express the
multiple-objective tradeoffs for a single reservoir system
had been developed. The procedure linked a niched
Pareto genetic algorithm with a simple reservoir model.
This method has been modified to consider a system of
multiple reservoirs. The system has been implemented on
massively parallel computer platforms.
Earth System Science 239