Hurricane Intensity Estimation from GOES-R Hyperspectral Environmental Suite Eye Sounding

Fourth GOES-R Users’ ConferenceMark DeMaria

NESDIS/ORA-STAR, Fort Collins, CO

INTRODUCTION

The next generation U.S. polar orbiting and geostationarysatellite systems (NPOESS and GOES-R) will includehyperspectral infrared sounders with several thousand spectral bands (HES and CrIS). This represents a two order ofmagnitude increase in the number of bands relative to the current operational sounders. NPOESS will also include an Advanced Technology Microwave Sounder (ATMS) that can be used in cloudy regions. In this study, temperature and moisture retrievals from AIRS/AMSU are used as a proxy forwhat will be available from GOES-R and NPOESS. This study is part of a larger project to develop tropical cyclone applications for future instrument platforms that also include ABI from GOES-R and VIIRS and the altimeter from NPOESS.

Tropical cyclone applications include:

1. Intensity estimation • Higher resolution Dvorak technique from ABI and VIIRS• Hurricane eye soundings from HES and CrIS/ATMS

2. Wind structure analysis• Application of hydrostatic and dynamical balance

constraints to HES and CrIS/ATMS temperature and moisture retrievals

3. Intensity prediction • Applications of ocean heat content from NPOESS altimetry• Moisture analysis in the storm environment from HES and

CrIS/ATMS

This poster shows preliminary results for estimating storm intensity from AIRS/AMSU hurricane eye soundings

AIRS RETRIEVALS

HURRICANE EYE SOUNDINGS SATELLITE INTENSITY ESTIMATES

RESULTS

FUTURE PLANSAIRS granules were obtained for all cases from Hurricanes Lili (2002), Fabian (2003) and Isabel (2003) that had corresponding dropwindsone data from the NOAA Gulfstream jet. Sixteen granules were available from these three storms.

The AIRS/AMSU temperature/moisture retrievals followed the technique of Susskind et al (2003):

1. AIRS data from 9 footprints within each AMSU footprint combined2. Preliminary microwave retrieval3. First infrared product4. Combined microwave/IR product

Only the combined product was used in this study.

AIRS/AMSU soundings closet to the storm center were extracted from each of the 16 granules. Soundings more than30 km from the storm center were eliminated, leaving the 6cases in Table 1 with AIRS/AMSU eye soundings. Theobserved minimum pressure and maximum wind from the National Hurricane Center best track interpolated to the AIRSsounding time are also shown in Table 1.

Table 1. The hurricane cases with AIRS/AMSU eye soundings.

Storm Granule Date

(mmddyy)

Granule Time (UTC)

Observed Max Wind

(kt)

Observed Min Sfc

Pres. (hPa)

Lili 100202 0717 102 960

Lili 100302 0759 97 959

Isabel 091303 1705 139 933

Isabel 091403 1753 140 933

Isabel 091603 1741 95 959

Isabel 091703 1823 90 955

GOES IR imagery for the 6 cases with eye soundings are shown in Fig. 1. Figure 2 shows the temperature anomalies of each eye sounding calculated by subtracting the average sounding from the four corner points of each granule.

Figure 1. Enhanced GOES IR imagery of the 6 hurricane caseswith AIRS/AMSU eye soundings

Lili 02 Oct 2002 07 UTC Lili 03 Oct 2002 08 UTC Isabel 13 Sep 2003 17 UTC

Isabel 14 Sep 2003 18 UTC Isabel 16 Sep 2003 18 UTC Isabel 17 Sep 2003 18 UTC

100

200

300

400

500

600

700

800

900

1000

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25

Temperature Deviation (K)

Pre

ss

ure

(h

Pa

)

Lili 1002 0717 Z

Lili 1003 0759 Z

100

200

300

400

500

600

700

800

900

1000

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25

Temperature Deviation (K)

Pre

ss

ure

(h

Pa

)

Isabel 0913 1705 Z

Isabel 0914 1753 ZIsabel 0916 1741 Z

Isabel 0917 1823 Z

Figure 2. The temperature anomaly versus pressure from the AIRS/AMSU soundings for the Hurricane Lili (left) and Hurricane Isabel (right) cases

One measure of tropical cyclone intensity is the minimumsea level pressure (MSLP). Given boundary conditions, the temperature T from AIRS/AMSU soundings can be substituted into the hydrostatic equation (1) and vertically integrated to estimate the MSLP. Special care must be taken to account for temperature errors near the surface. The vertical integrationprocedure is summarized below.

dP/P = -g/(RT)dz (1)

Vertical Integration Procedure:1. Start with an upper boundary condition for the height z at pressure P=100 hPa from the NCEP global analysis2. Integrate (1) downward from 100 to 850 hPa with T from the AIRS/AMSU retrieval3. Integrate (1) from 850 hPa to the surface with a constant lapse rate sounding with T(850) from the AIRS/AMSU sounding and T(surface) from the observed sea surface temperature (SST)

Two alternate versions of the above procedure were tested where the level the divides the AIRS/AMSU T from the constant lapse rate T was 700 hPa instead of 850 hPa, or500 hPa instead of 850 hPa.

Storm Obs 850 hPa 700 hPa 500 hPa

Lili 1002 960 998 993 981

Lili 1003 959 1030 1017 997

Isabel 0913 933 932 931 934

Isabel 0914 933 943 941 942

Isabel 0916 959 960 959 957

Isabel 0917 955 960 958 949

Table 2. The observed and estimated MSLP (hPa) for the six storm cases with eye soundings. The estimates use the AIRS/AMSU input from 100 hPa to a specified lower level of 850, 700 or 500 hPa.

-10

0

10

20

30

40

50

60

70

80

Lili 02 Oct

Lili 03 Oct

Isabel 13 Sep

Isabel 14 Sep

Isabel 16 Sep

Isabel 17 Sep

MS

LP

Err

or

(hP

a)

850 hPa

700 hPa

500 hPa

Figure 3. The errors of the MSLP estimates from the hydrostatic integrations of the AIRS/AMSU sounding from 100 hPa to 850, 700 or 500 hPa.

Table 2 and Fig. 3 show the MSLP estimates and errorsrelative to the ground truth for the 6 hurricane cases. Thefollowing conclusions can be drawn from these results.

1. The MSLP estimates were very accurate for the 4 Isabel cases. 2. The MSLP estimates were very poor for the 2 Lili cases with estimated pressures that were much too high.3. The difference in the performance between the two storms is probably related to the differences in size as can be seen in Fig. 1. Isabel was much larger, and was better resolved by the combined AMSU/AIRS data, which has a horizontal resolution of about 50 km.4. For storms with fairly clear eyes, single field of view retrievals that take advantage of the full AIRS resolution would be useful. 5. Cloud contamination was a problem for the Lili retrievals, as can be seen by the unrealistic cold anomalies in the lower troposphere in Fig. 2. 6. Both the NPOESS and GOES-R sounders will have

higher spatial resolution than AIRS/AMSU. Those eye soundings should be more accurate than shown here.

This work will be generalized by obtaining a larger sampleof hurricane eye soundings from AIRS. A wide variety of cases are available from the very active 2005 hurricane season. Work is also on-going on the other tropicalcyclone applications listed in the Introduction. AIRS/AMSUretrievals and MODIS imagery will be used as proxy datafor those studies.

REFERENCESusskind, J., C.D. Barnet and J.M. Blaisdell 2003. Retrieval of atmospheric and surface parameters from AIRS/AMSU/HSB data in the presence of clouds. IEEE Trans. Geosci. Remote Sens. 41, 390-409