A research investigation was conducted into the possibility of using atmospheric observations made in the past from both terrestrial and space-based platforms to create a global, coherent four dimensional analysis for the purpose of studying atmospheric, oceanic, and land surface processes relevant to climate simulation, monitoring, and change. This investigation consisted of the following tasks: (1) a mature global data assimilation system was obtained from the National Meteorological Center and modified for use on a Cray X-MP computer system; (2) atmospheric observations for the period 20 Nov. 1982 through 1 Mar. 1983, including rawinsonde soundings, aircraft-based measurements, pilot balloons, and temperature soundings from polar orbiting satellites were obtained from several sources; and (3) the global data assimilation system was used to reassimilate the atmospheric observations to produce a new atmospheric analysis which was then compared with the contemporaneous analysis. The global hydrologic cycle, including fluxes between the atmosphere and both the land and ocean surfaces, was estimated. The flux of water from the ocean surface into the atmosphere, its transport in the form of latent heat to remote regions, and its return to the surface in the form of precipitation were estimated globally. In addition, several regional budgets for selected tropical oceanic and extratropical continental areas were also done

Kinter, J. L., III

Shukla, J.

English

NASA Technical Reports Server

NASA-CR-196495
F'mal Technical Report
NASA Grant NAGW-1166
Integration of Space and In-Situ Observations
to Study Atmosphere, Ocean and Land Processes
1 September 1987- 31 August 1992
P.I. - I. Shukla Co-P.I. - ;r. L. Kinter ITI
Center for Ocean-Land-Atmosphere Interactions
University of Maryland
College Park, MD 20742
.- . r
A research investigation was conducted into the possibility of using atmospheric observations
made in the past from both terrestrial and space-based platforms to ereate a global, coherent four
dimensional analysis for the purpose of studying atmospheric, oceanic and land surface processes
relevant to climate simulation, monitoring and change. This investigation consisted of the
following tasks:
• A mature global data assimilation system was obtained from the National
Meteorological Center and modified for use on a Cray X-MP computer system.
•Atmospheric observations for the period 20 November 1982 through 1 March
1983, including rawinsonde soundings, aircraft-based measurements, pilot balloons,
and temperature soundings from polar orbiting satellites were obtained from
several sources.
• The global data assimilation system was used to reassimilate the atmospheric
observations to produce a new atmospheric analysis which was then compared
with the contemporaneous analysis.
The global hydrologic cycle, including fluxes between the atmosphere and both the land and
ocean surfaces, was estimated. The flux of water from the ocean surface into the atmosphere,
its transport in the form of latent heat to remote regions, and its return to the surface in the form
of precipitation were estimated globally. In addition, several regional budgets for selected
tropical oceanic and extratropical continental areas have also been done.
The period of 20 November 1982 through 1 March 1983 was chosen because of the high level
of ocean-atmosphere interaction during that period. It was found, for example, that much more
realistic analyses of the surface temperature analysis over the tropical Pacific Ocean provided a
more accurate picture of the ocean-atmosphere interaction during the tmusually large E1 Nifio
event of that period.
Among the other significant improvements over the contemporaneously produced analysis we
found in the reanalyzed data were the more realistic representation of the planetary boundary
layer temperatures and winds over the tropical oceans. This improvement allowed a much more
accurate calculation of the surface fluxes of latent and semsible heat. Also improved were the
mean meridional circulation which provided a much better estimate of the poleward transport of
(NASA-CR-194495) INTEGRATION OF
SPACE AND IN-SITU OBSERVATIONS TO
STUDY ATMOSPHERF, OCEAN ANO LAND
PROCESSES Final Technical Report, I
Sep. I98# - 3I Auq. i992 (Maryland
Iinl ii _i I 1
N94-14500
Unclas
https://ntrs.nasa.gov/search.jsp?R=19940010027 2020-06-16T19:44:10+00:00Z
moisture by the large scale flow. The representation of the humidity field was substantially
improved, although this sensitive quantity is one where further research is needed into extracting
information from the existing observations and into developing better observing systems for
measuring moisture content m the atmosphere and at the land surface. Finally, the assimilating
modal simulation of the evaporation (ocean surface), evapotranspiration (land surface) and
precipitation fields aUowed the calculation of a complete moisture budget (Kinter et al., 1989).
A study workshop was organized and hosted by the co-principal investigators in which
international experts in data assimilation were assembled to discuss the merit and feasibility of
a larger reanalysis effort than was undertaken in this pilot study (Kinter and Shulda, 1989). The
consensus of the group was that there is a real need to use modem data assimilation and quality
control techniques on the available archive of atmospheric observations to develop a
comprehensive, coherent, global analysis for climate monitoring and climate research.
K.inter 1Tr, LL., D.A. Paolino, and J. Shulda, 1989: An estimate of the global hydrologic cycle
from reanalyzed atmospheric circulation data. IAMAP Symposium on Global Energy and
Water Fluxes (31 luly - 12 August 1989, University of Reading, UK).
Kinter III, I.L. and L Shukla, 1989: Reanalysis for TOGA (Tropical Oceans Global Atmosphere),
I-3 February 1989, Center for Ocean-Land-Atmosphere Interactions. Bull. A met. Meteor.
Soc., 70, 1422-1427.
FINAL REPORT
for
Integration of Space and In Situ Observations
to Study Atmosphere, Ocean, Land Processes:
Climatic Water Budget Supplement
U.M.C.P Reference: Cooperative Agreement No. 26929B
by
Cort J. Willmott, Principal Investigator
Center for Climatic Research
Department of Geography
University of Delaware
Newark, DE 19716
(Phone: 302-831-8998)
Project Budget:
$64,283
Signature: __
Cort J Willmott
Principal Investigator
Date:
/ /
Research was conducted concerning the development of a
decadal-scale data set containing time series of monthly air
temperature (Tm) , precipitation (P_), evapotranspiration (E_), soil
moisture (wm) and snow cover (_m) for the terrestrial world. This
data set was completed and delivered to David Straus at the
University of Maryland. It contained the above-mentioned variables
for most of the 1970s and 1980s. Time series of T_ and Pm were made
available by NCAR. A spatial interpolation procedure discussed by
Willmott et al (1985b) as well as a high-resolution climatology of
T and P were used to estimate values of T m and Pm at the nodes of
a 0.5°x0.5 ° lattice. The derived variables (E_, w= and _m) were
obtained from the gridded T m and Pm data using the water-budget
algorithm described by Willmott et al. (1985a)
Spatial interpolation of climate variables, especially from a
sparse station network, has been shown to produce considerable bias
both in the estimation of grid-point values and spatial averages
(Willmott and Legates, 1991: Willmott et al., 1991). To improve
upon the raw station-network-to-grid-point interpolation that is
common in the climatological literature, a climatologically Aided
Interpolation (CAI) scheme was developed, tested and used to
estimate our terrestrial fields of T m and Pm" This involved
computing a difference between a monthly normal at each NCAR
station location (obtained from Legates and Willmott's 1990a and
1990b high-_esolution climatology of monthly averages) and the
actual monthly value of the NCAR observation at that station. Once
these differences were obtained for all NCAR months and stations,
they were interpolated to the 0.5°x0.5 ° grid and then added to the
Legates and Willmott normal available at that grid node.
Illustrating for P_, a precipitation difference was first computed
from
dPi = P= - Pci
where Pci is the climatological normal for that month at station i
(from Legates and Willmott, 1990a) and P= is the actual monthly
precipitation value drawn from the NCAR data set for month m and
NCAR station i. NCAR-station precipitation differences (dPis) then
were interpolated to the 0.5°x0.5 ° lattice (according to Willmott et
al., 1985b) to obtain an estimate at each grid point j (d_). Each
d R subsequently was added to the corresponding Legates and Willmott
climatological mean at that grid point, which gave an estimate of
monthly precipitation at j (P_). This "new" interpolation scheme
has been tested on a variety of data sets (cf, Robeson, 1992) and
has been found to be far superior to the simple interpolation from
the NCAR stations to virtually any resolution lattice. Papers by
Willmott and Legates (1991) and Willmott et al. (1991) report on
the sizeable biases that can arise when simple spatial
interpolation to a grid is made from a sparse station network.
Using Willmott et al.'s (1985a) water-budget procedure, values of
F_j, w_j and _mj were estimated for all months available in the NCAR
archive at the 0.5°x0.5 ° resolution.
A few tasks remain incomplete. A wind-velocity time series for
the terrestrial world was proposed; however, owing to a number of
data incompatibilies, the final data set remains to be completed.
A "corrected" (for raingage biases) precipitation time-series data
set also remains incomplete because the gage-correction procedure
requires the wind-velocity fields. Efforts by the Principal
Investigator and his colleagues to complete these data archives are
ongoing and,. when complete, they will be made available to the
climatological community. Upon completion, it also will be possible
to compute more accurate E_, w m and _ fields.
REFERENCES
Legates, D. R. and C. J. Willmott, 1990a. Mean Seasonal and
Spatial Variability in Gauge-Corr ect ed, G loba 1
Precipitation. International Journal of Climatology, I0,
111-127.
Legates, D. R. and C. J. Willmott, 1990b. Mean Seasonal and
Spatial Variability in Global Surface Air Temperature.
Theoretical and Applied Climatology, 41, 11-21.
Robeson, S. M., 1992. Spatial Interpolation, Network Bias, and
Terrestrial Air Temperature Variability. Newark, DE:
University of Delaware, Ph.D. dissertation.
Willmott, C. J., C. M. Rowe, and Y. Mintz, 1985a. Climatology of
the Terrestrial Seasonal Water Cycle. Journal of Climatology,
5, 589-606.
Willmott, C. J., C. M. Rowe, and W. D. Philpot, 1985b. Small-Scale
Climate Maps: A Sensitivity Analysis of Some Common
Assumptions Associated with Grid-Point Interpolation and
Contouring. The American Cartographer, 12, 5-16.
Willmott, C. J., S. M. Robeson and J. J. Feddema, 1991. Influence
of Spatially Variable Instrument Networks on Climatic
Averages. Geophysical Research Letters, 18(12), 2249-2251.
Willmott, C. J. and D. R. Legates, 1991. Rising Estimates of
Terrestrial and Global Precipitation. Climate Research 1(3),
179-186.
Final Report
Project Tide:
Sponsor:
PI:
Institution:
Interaction of Space & In Situ Observations to Study Atmosphere-
Ocean-Land Processes: Climatic Water Budget Supplement
University of Maryland
Brian F. Farrell
Harvard University
Division of Applied Sciences
Pierce Hall
Harvard University
Cambridge, MA 02138
Award Period: 09101/87 - 08/31/92
-2-
Linear Instability andPredictabilityof Observed 3-d Atmospheric Flows
The two main areas of work were supported by this subcontract: study of the
localization of storm tracks and study of the predictability of flow regimes.
Our study of storm tracks involved relaxation of the assumption of flow sym-
metry. One major effect of asymmetries is the emergence of a correspondence
between local instability on jets and absolute instability of the nonlocal jet which
potentially restricts storm track instability to a limited subset of flow configurations.
We find that loca! instability requires easterly flow sea,- the ground, that the storm
tracks must extend for O(10) Rossby Radii in order to support local instability (Del-
Sole and Farrell, 1993), and that the response of a stable jet to stochastic forcing
increases rapidly with shear and decreases with static stability (Farrell and Ioannou,
1993).
The predictability problem was examined building on a new method for identifying
disturbances that produce the most rapid growth of perturbation variance (Farrell,
1990). This work addresses the observation that the atmosphere varies in predictability
depending on the flow regime. The method developed for studying idealized flows can
be extended to NWP models, indeed this is presently being pursued at ECMWF. This
extension involves use of the adjoint of the linearized NWP model already developed
for applications in data assimilation.
PUBLICATIONS UNDER THIS CONTRACT
DelSole, T., and B. F. Fan'ell, 1993: Absolute and convective instabilities in a non-
linear two layer quasi-geostrophie model. I. Atmos. Sci., (submitted)
Fan-ell, B. F., i990: SmaLl error dynamics and the predictability of atmospheric flows.
I. Atmos. Sci., 47, 2409-2416.
Fan-ell, B. F., and P. I. Ioannou, 1993: Theory of the stochastic dynamics of baroclinic
waves. I. Atmos. Sci., (submitted)
TechnicalReport
Project Tide:
Sponsor:
PI:
Institution:
Interaction of Space& In Situ Observationsto Study Atmosphere-
Ocean-LandProcesses:Climatic WaterBudgetSupplement
University of Maryland
Brian F. Fan'eU
HarvardUniversity
Division of Applied Sciences
PierceHall
HarvardUniversity
Cambridge,MA 02138
Award Period: 09/01/87- 08/31/92
-2-
Linear Instability andPredictability of Observed3-d AtmosphericFlows
The two main areasof work were supported by this subcontract: study of the
localization of storm tracks and study of the predictability of flow regimes.
1. STORM TRACKS
The Northern Hemisphere midlafitude troposphere is dominated by a zonal jet
concentrated near the tropopause; closer examination reveals that the jet is variable in
intensity and orientation forming geographically localized storm tracks associated pri-
marily with the western ocean boundaries. Of central interest to meteorology are the
ubiquitous transient waves with scale of a few thousand kilometers which form and
propagate on this relatively fixed background flow. The origin and growth to moderate
amplitude of these synoptic scale waves is generally ascribed to linear baroclinic insta-
bility of the jet. This theory is founded on the discovery that the quasi-geostrophic
equations linearized about an inviseid, zonally symmetric, baroclinic basic state support
normal modes that grow exponentially in time. These unstable modes have approxi-
mately the scale and structure of observed waves and the theory constructed around
these instabilities presumes that infinitesimal perturbations to the zonal flow occur with
nonzero projection on the modal speclrum so that over many doubling times the wave
of maximum growth eventually dominates the observed synoptic scale variance.
Recent work on baroctinic instability theory has involved a relaxation of assump-
tions made in earlier studies in the interest of simplicity, one of these being neglect of
flow asymmetries. One major effect of asymmetries is the emergence of a correspon-
dence between local instability on jets and absolute instability of the nonlocal jet
which potentially restricts storm track instability to a limited subset of flow
configurations (Pierrehumbert, 1984). In the case of nonzonal flows it is important to
separate local instability from global modes which maintain their instability by cycling
energy all the way around the globe obtaining a boost on passing repeatedly through
the enhanced baroclinicity of the storm track region. It is likely (Pierrehumbert., 1984;
DelSole and Fan-ell, 1993) that the latter are not physically realistic; unfortunately in a
nearly inviscid model it is difficult to tell local from global instability so uhat the non-
zonal instability calculations mentioned above do not answer the question of whether
realistic observed flows support local instability. We have addressed this problem in
two ways, first by constructing a nonlinear q-g channel model with sponge layers at
the ends to allow controlled experiments on the absolute/convective transition in zon-
ally asymmetric flows, and second by forcing jets stochastically in a linear model to
determine how local response to forcing varies with shear and static stability. We find
that local instability requires easterly flow near the ground, that the storm tracks must
extend for O(10) Rossby Radii in order to support local instability (DelSole and Far-
rell, 1993), and that the response of a stable jet to stochastic forcing increases rapidly
with shear and decreases with static stability (Farrell and Ioannou, 1993).
-3-
2. PREDICTAB112TY
The predictability problem wasexaminedbuilding on a new method for identify-
ing disturbances that produce the most rapid growth of perturbation variance (Farrell,
1988, 1989, 1990). This work addresses the observation that the atmosphere varies in
predictability depending on the flow regime. The method used involves constructing a
spanning set of perturbations ordered in growth of variance over a fiane interval chosen
to be representative of synoptic predictability intervals of around a week. These per-
turbations define the axes of the predictability error ellipse and the axes of maximum
growth determine the predictability of the flow while the form of the perturbations of
maximum growth correspond to the preferred responses of the system. A preliminary
study of predictability has been carried out for flows chosen to model midlatitude
storm tracks.
Having in hand theoretical u.uderstanding of the predictability problem puts us in
position to apply the theory to observed flows. We expect from experience with model
problems that flows with rapid perturbation growth can be distinguished from more
predictable flows by differences in evolution of the error ellipse. A new method for
obtaining criteria for a given flow to be predictable and by extension those characteris-
tics of flows that are most crucial to observe accurately in order to obtain a good fore-
cast are central results of this study.
The method developed for studying idealized flows can be extended to NWP
models, indeed this is presently being pursued at ECMW'F. This extension involves
use of the adjoint of the 1Luearized NWP model already developed for applications in
data assimilation.
REFERENCES
DelSole, T., and B. F. Farrell, 1993: Absolute and convective instabilities in a non-
linear two layer quasi-geostrophie model. I. Atmos. Sci., (submitted)
Fan-ell, B. F., 1988: Optimal excitation of neutral Rossby waves. I. Atmos. Sci.,46,
163-172.
Fan-ell, B. F., 1989: Optimal excitation of baroclinic waves. I. Atmos. Sci., 46, 1193-
1206.
Fan'ell, B. F., 1990: Small error dynamics and the predictability of atmospheric flows.
I. Atmos. Sci., 47, 2409-2416.
Farre11, B. F., and P. I. Ioannou, 1993: Theory of the stochastic dynamics of baroclinic
waves. I. Atmos. Sci., (submitted)
Pierrehumbert, R.T., 1984: Local and global baroclimc instability in zonally inhomo-
geneous flows. I. Atmos. Sci., 41, 2141-2162.


Integration of space and in-situ observations to study atmosphere, ocean and land processes

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