**Modeling and Analysis of the Earth's Hydrologic Cycle**

**P.I.: Donald R. Johnson**

**Space Science and Engineering Center**

**University of Wisconsin -- Madison**

***Summary***

***A key aim of this project is to advance the understanding of global
water vapor and inert trace constituent transport in relation to climate
change through analysis of simulations produced by the global University
of Wisconsin (UW) hybrid isentropic coordinate models. Research has
established that simulations in isentropic coordinates are remarkably
more accurate in the transport of water vapor, and inert and chemical
constituents compared against corresponding sigma coordinate models.***

**1. Introduction**

The primary objectives of this research are to; 1) advance the modeling
of climate change by developing a hybrid isentropic model for global and
regional climate simulations, 2) advance the understanding of physical
processes involving water substances and the transport of trace
constituents, and 3) examine the limits of global and regional climate
predictability. Model development has proceeded through a hierarchy of
models from a preliminary channel model to the full fledge global
climate model in use today \[the University of Wisconsin-Madison
isentropic-eta (UW θ-η) coordinate model\]. Studies of a wide variety of
Eulerian and semi-Lagrangian numerics and different algorithms for
parameterization of boundary layer processes and dry and moist
convection have been carried out.

**2. Significance of Research**

This research addresses fundamental issues underlying the understanding
and modeling of hydrologic processes. Hydrologic processes, including
surface evaporation, long-range transport of water substances, release
of latent heating involving evaporation/condensation and attenuation of
the radiative flux of energy by water vapor and clouds, are central in
the regulation of global and regional climate.

A premise of this work is that accurate simulation of the long-range
transport of mass, momentum, energy, water vapor and other trace
constituents is crucial for modeling the climate state. Substantial
evidence exists illustrating the inherent difficulties in simulating the
long-range transport of water vapor and other trace constituents
utilizing conventional sigma coordinate climate models. This limitation
stems primarily from problems associated with vertical advection of
water vapor and other trace constituents in sigma models. The water
vapor structure and its transport are primarily two dimensional in
isentropic coordinates except in regions of moist convection. The
problems associated with vertical advection remain negligible in
isentropic coordinates relative to sigma coordinate models over much of
the global domain.

**3 The UW Model**

The UW θ-η model is a global grid point model employing piecewise
parabolic method (PPM) transport numerics and two-level forward time
differencing. The model incorporates the full suite of physical
parameterizations obtained from the National Center for Atmospheric
Research (NCAR) community climate model version 3 (CCM3). Over the past
year a prognostic cloud prediction scheme developed by NASA Goddard
scientists has been implemented in the UW model. This addition provides
the capability to more accurately simulate and assess the impact of
clouds and water vapor on atmospheric circulation.

**4. Accomplishments**

During the past year the P.I. has had frequent interaction with
scientists from DOE, NASA and NOAA concerning climate modeling and the
importance of hydrologic processes. He also serves as NOAA's National
Centers for Environmental Prediction Special Project Scientist.

Results from a 14-year climate simulation with the UW θ-η model at
2.8125° latitude-longitude resolution have been conditionally accepted
for publication in the *Journal of Climate*. Daily 5-day forecasts at
0.7° latitude-longitude resolution (approximately 4,000,000 model grid
points) have been ongoing for the last 23 months.

The NASA Langley 3D chemical module has been incorporated in the UW
model to provide a global chemical modeling system involving 55
chemicals in the troposphere and stratosphere. Results from this joint
project have been published in the *Journal of Geophysical Research.*

**5. Computational Approach**

The UW model can currently use multiple processors on one node of the
IBM/SP using either OpenMP parallelism or MPI message passing. An effort
is under way to convert the code to use both MPI message passing and
OpenMP to maximize the use of multiple nodes. This capability, which is
70-80% complete, will greatly enhance our research efforts by providing
much faster throughput for climate simulations. The use of multiple
nodes will allow substantial increases in both horizontal and vertical
resolution for climate simulation and NWP. The increased computational
capability also allows the use of more realistic (although more
computationally intense) physical parameterizations. The use of the
SciDAC terascale computing facility will provide the capability to
conduct longer and more complex climate simulations in a reasonable time
and greatly assist the determination of the impact of different physical
parameterizations and different spatial resolutions.

**6. Future Plans**

During the coming year, the conversion of the UW model to use both MPI
message passing and OpenMP parallelism will be completed. The completion
of this effort will greatly facilitate the achievement of the scientific
goals of our research effort.

Numerous seasonal and multi-year simulations will be analyzed to further
our investigations of regional climate in relation to energy balance and
atmospheric hydrologic processes. This effort will also continue to
investigate the relative abilities of isentropic and sigma coordinate
models to transport water vapor and explicitly predict cloud substances,
and to diagnose the impact of the explicitly simulated clouds on cloud
radiative forcing. The impact of increased horizontal and vertical
resolution will also be ascertained.

The increased processing capability will allow implementation of more
highly developed physical parameterizations into the UW model including
more realistic prognostic simulation of clouds. The robust simulation
capabilities of the UW model have led to the desire to couple the UW
model to a sophisticated ocean model in order to provide a stand-alone
system for climate simulation. The terascale computing capability
provided by SciDAC is critical to this effort.

The above efforts seek to take advantage of the increased numerical
accuracies of long-range transport utilizing hybrid isentropic
coordinates to improve the simulation of moist reversible processes
involving water vapor and cloud water and ice and related hydrological
processes. This increased accuracy is essential to increasing the
accuracies of other important processes that interact strongly with
other hydrologic, chemical and biospheric processes, all of which are
critical to accurately simulating the climate state regionally and
globally.