Proposal to
National Oceanic and Atmospheric Administration
National Environmental Satellite, Data, and Information Service
Washington DC
Pass#52954
for
NPOESS Applications to Tropical Cyclone Analysis and Forecasting
Submitted by
Cooperative Institute for Research in the Atmosphere
Colorado State University
West Laporte Avenue
Fort Collins, CO 80523-1375
Dr. John A. Knaff
Principal Investigator
CIRA/Colorado State University
Telephone: 970-491-8881
Email: knaff@cira.colostate.edu
In partnership with
Dr. Mark DeMaria
Regional and Mesoscale Meteorology Team Leader
NESDIS Office of Research and Applications
Telephone: 970-491-8405
Email: Mark.DeMaria@noaa.gov
Period of Activity: January 1, 2006 – December 31, 2006
_______________________
John A. Knaff, P.I.
CIRA
(970) 491-8448
___________________________
Thomas Vonder Haar, Director
CIRA
(970) 491-8566
_____________________
Anita Montgomery
Research Administrator
Office of Sponsored Programs
(970) 491-6586
1. Introduction
To prepare for tropical cyclones (TCs) and mitigate their effects, accurate analyses and
forecasts of the track, intensity, wind structure and rainfall are required. TC track forecast
errors have decreased significantly over the past several decades, and some modest
improvement in intensity forecast skill has occurred in the past few years. The ability to
forecast TC wind structure and rainfall have received considerably less attention. The
track error reductions are due to improved dynamical models, while the intensity
improvements resulted from better dynamical and statistical forecast techniques. Despite
these gains, tropical cyclone warnings are still only issued 24 hours in advance. This
amount of time is not always long enough for large metropolitan areas, as was so
dramatically illustrated in Hurricane Katrina in 2005. Further improvement in TC
forecasting will require better measurements of the storm environment and core,
advanced tropical cyclone models, and advanced data assimilation techniques to utilize
the new data. Product development activities to diagnose the required forecast parameters
such as TC wind radii from the data and model fields are also needed.
Although the inner cores of TCs have a small spatial scale (100 km or less), the time
scale of the track and intensity changes have a fairly long time scale (6 hours or longer).
Because of this long time scale, observations from polar orbiting satellites are very well
suited to tropical cyclone analysis. The advanced instruments on NPOESS have great
potential to contribute to TC forecast improvements. In this proposal, the application of
NPOESS data to tropical cyclone analysis and short term forecasting will be
demonstrated using proxy data from existing operational and experimental satellites. The
utility of the VIIRS instrument for intensity and wind structure diagnosis will be
investigated using MODIS and AVHRR observations. The utility of the combined ATMS
and CrIS sounding in tropical cyclones will also be demonstrated using proxy data from
AIRS/AMSU retrievals from recent tropical cyclones, as well as output from numerical
model simulations. The ability to use these sounding in tropical cyclone eyes and well as
in the storm environments will be studied. The eye soundings have great promise for
intensity monitoring. The soundings surrounding the storm can be used to evaluate the
moisture available to the storm (for short term intensity forecasting), and to provide wind
structure estimation, though the use of hydrostatic and dynamical constraints. The
potential use of the ocean altimeter planned for NPOESS will also be demonstrated by
investigating the impact of oceanic heat content determined from current altimeters on
tropical cyclone intensity changes.
2. Prototype Tropical Cyclone Products
2.1 VIIRS Applications
The VIIRS instrument will provide visible and infrared imagery with horizontal
resolution finer than currently available from GOES and the current series of NOAA
polar orbiting satellites. Visible and IR imagery has been used at operational forecast
centers for the last several decades to monitor tropical cyclone intensity with various
versions of the Dvorak technique (e.g., Dvorak 1975). The IR version of the technique is
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more objective, and relies on the difference between the warm eye temperature and the
cold clouds in the eye wall. For tropical cyclones with small eyes, the technique can be
limited by the horizontal resolution. In this project, high resolution MODIS and AVHRR
data will be used as a proxy for VIIRS. For example, Fig. 1 shows 1 km IR imagery from
MODIS of hurricane Lili from the 2002 hurricane season. For comparison, the imagery
was degraded to 4 km (the current resolution of GOES). Considerably more detail can be
seen in the eye and eye wall region with the finer resolution. In this project, a series of
tropical cyclone images from MODIS and AVHRR will be obtained. Companion images
will be generated by degrading the resolution to that of the current GOES and POES
satellites. The impact on the Dvorak method, and the more general IR tropical cyclone
wind structure algorithm described by Mueller et al (2006) will be evaluated.
2.2 ATMS/CrIS Applications
The combined microwave and infrared sounders planned for NPOESS will provide
temperature and moisture retrievals with unprecedented accuracy. Proxy data from
AIRS/AMSU will be used to illustrate the utility of ATMS/CrIS for tropical cyclone
analysis.
In the first application, the AIRS/AMSU retrievals will be obtained in hurricane eyes. For
weaker systems without clear eyes, the technique will rely on the microwave data from
the ATMS. Given an upper boundary condition which can be obtained from an NCEP
global analysis, the hydrostatic equation can integrated to the surface using the
temperature and moisture sounding to directly estimate the surface pressure. This will
provide a new and novel method for monitoring the intensity of tropical cyclones, which
will be especially useful in regions such as the Pacific which do not have routine aircraft
reconnaissance observations available.
As an example of this technique, Fig. 2 shows an eye sounding obtained from a combined
AIRS/AMSU retrieval in Hurricane Isabel (2003) from the AQUA satellite. The
hydrostatic integration of the eye sounding from 100 hPa to the surface gave a minimum
pressure of 936 hPa, which compared well with the 933 hPa measure by aircraft.
In the second application, the above method will be generalized to determine TC wind
structure. The radius of 50 kt winds is a critical parameter for ship routing, and the 34 ktwind radius is important for coastal evacuations because these must be completed before
the arrival of gale force winds. To estimate the outer wind field, the two dimensional
geopotential height field near the surface can be estimated from a downward hydrostatic
integration. The non-linear balance equation can be used to estimate the wind field above
the boundary layer, and then standard surface reduction methods can be used to estimate
the surface winds. This application provides an estimate of the entire surface wind field,
instead of just a point value of the maximum intensity.
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Figure 1. Comparison of 1 km (top) and 4 km (bottom) IR imagery for Hurricane Lili on
2 October 2002.
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Eye - Environment
Temperature
100
200
Eye Sounding
Environment
Sounding
Pressure (hPa)
300
400
500
600
700
800
900
1000
0
2
4
6
8
10
12
14
16
18
Temperature Anomaly (C)
Figure 2. The location of the combined AIRS/AMSU retrieval in the eye and environment
of Hurricane Isabel (left). The temperature difference between the eye and environment
sounding is shown on the right and illustrates the classic warm core structure.
The wind structure estimation method has already been tested on a few AMSU-based
temperature retrievals (Bessho et al 2006), as shown in Figure 3. Results show that the
technique has accuracy comparable to QuikSCAT surface wind retrievals, which are
extremely useful for operational TC analysis at the National Hurricane Center (NHC) and
the Joint Typhoon Warning Center. Although neither technique resolves the inner core,
the outer wind field structure can be determined. It is anticipated that the ATMS/CrIS
retrievals will have improved horizontal resolution compared to AIRS/AMSU. To
investigate the improvement in the wind structure retrieval, the algorithm will also be
applied to proxy soundings from numerical hurricane model simulations, with various
horizontal filters applied to match the planned resolution of ATMS, and that of the
current AMSU resolution.
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Figure 3. The surface winds for Hurricane Floyd (1999) from QuikSCAT (left) and the
AMSU retrieval technique.
2.3 Ocean Altimeter Applications
The fact that hurricanes are fueled by heat from the ocean has been known for more than
half of a century. However, the depth of the warm water can vary considerably. Thus, the
oceanic heat content (OHC), the ocean energy available to the storm, can vary
considerably, depending on the subsurface ocean structure. The OHC can be estimated
using a combination of sea surface temperature and ocean altimeter measurements. The
ocean altimeter planned for NPOESS will be a valuable part of this observing system.
Recent results (DeMaria et al 2005) have shown that the OHC input can have an effect on
operational tropical cyclone intensity forecasts. In this proposal, OHC estimated from
current satellites will be used to identify cases where the ocean impacts were especially
important. For example, Fig. 4 shows the operational OHC product from the National
Hurricane Center (determined from satellite altimetry) and the track and intensity of
Hurricane Katrina from 2005 season. In this case, Katrina reached category 5 intensity
(i.e., winds greater than 135 kt) as it passed over a region of very high OHC in the Gulf
of Mexico. Investigation of these types of cases will help to highlight the need for
altimetry data from NPOESS for operational hurricane intensity forecasting.
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Figure 4. The ocean heat content estimated from satellite altimetry and the track (circles)
of hurricane Katrina from 2005.
3. Relevance to the NPOESS mission
Tropical cyclones have a time scale consistent with that of polar orbiting satellites, and
the suite of instrumentation planned for NPOESS had great potential for improvement of
tropical cyclone analysis and forecasting. Tropical cyclones are costly both in terms
property damage and loss of life, and so the improvements in hurricane analysis
forecasting from the NPOESS program will have great societal benefit. For nearly all
tropical cyclone basins except the Atlantic, reconnaissance aircraft data is not routinely
available, so that tropical cyclone monitoring is almost exclusively from satellite data.
Thus, NPOESS will be even more important for the interests of the U.S. Department of
Defense, who have global tropical cyclone forecast responsibility.
In the future, the infrared and microwave sounding information from NPOESS will be
included in numerical hurricane models through direct radiance assimilation. However, a
number of other diagnostic products will be possible provided that the temperature and
moisture fields that are used as input are of sufficient accuracy. This proposal will help to
establish the accuracy of the NPOESS algorithms near tropical cyclones, and evaluate the
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impact on derived intensity and wind structure products that are of interest to operational
forecasters. The work will also help to pave the way for operational NPOESS-based
tropical cyclone algorithms.
4. Budget Explanation
The proposed budget for the first year of this project is $45 K, which will help to support
CIRA research associates, a computer programmer and a student assistant. The
contribution from M. DeMaria will be provided from NOAA/ORA base funds at no cost
to NESDIS.
PERSONNEL:
1. Salaries: Base salaries included in this proposal reflect the actual salaries approved by
the Governing Board of Colorado State University for the period July 1, 2005 through
June 30, 2006. Any salaries beyond this period are budgeted at a 4% increase over the
prior year’s annual base. All individuals budgeted are employees of Colorado State
University.
2. Fringe Benefits: The following estimated CSU rates were applied to the above
salaries based on the individual’s payroll classification.
a. Faculty/Administrative Professional
b. State Classified
c. Student Hourly
FY 2005
20.3%
20.5%
1.2%
FY 2006
20.3%
21.5%
1.2%
TRAVEL:
Travel is budgeted based on the successful completion of the project and the proposed
dissemination of the research results. Per diem rates are applied when the destination is
to a location listed in the CSU per diem/city publication. Airfare and rental car estimates
are obtained from state approved travel agencies. The expenses of one trip is budgeted to
Miami, FL, for collaboration with the AOML Hurricane Research Division and the
National Hurricane Center.
SUPPLIES:
$500 is budgeted for editing software. The software will be needed to make short highquality movie loops that include sound, narration and animation. This was requested by
the Integrated Program Office for project documentation and promotion.
OTHER:
The CIRA Computer Infrastructure charges provide computer and data support associated
with this project, for the use of the computers already available at CIRA. The Computer
Infrastructure hourly rate is determined by CIRA and depends on the actual cost of the
network/printing, consultation, Linux hardware and maintenance, data and materials.
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INDIRECT COSTS:
An Indirect Rate of 25% is charged on this proposal. This is the negotiated rate for
CIRA’s Cooperative Agreement for the period January 1, 2005-June 30, 2006. The rate
is applied to Modified Total Direct Costs (MTDC). MTDC is defined as Total Direct
Costs less Equipment, GRA Tuition, and Subcontracts > $25,000.
References
Bessho, K., M. DeMaria and J.A. Knaff, 2006: Tropical cyclone wind retrievals from the
Advanced Microwave Sounder Unit (AMSU): Application to surface wind analysis. J.
Appl. Meteor, 46, in press.
DeMaria, M., M. Mainelli, L.K. Shay, J.A. Knaff and J. Kaplan, 2005: Further
Improvements in the Statistical Hurricane Intensity Prediction Scheme (SHIPS). Wea.
Forecasting, 20, 531-543.
Dvorak, Vernon F. 1975: Tropical Cyclone Intensity Analysis and Forecasting from
Satellite Imagery. Mon. Wea. Rev., 103, 420–464.
Mueller, K., M. DeMaria, J.A. Knaff and T.H. Vonder Haar, 2005: Objective Estimation
of Tropical Cyclone Wind Structure from Infrared Satellite Data. Wea. Forecasting, 21,
in press.
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