We support validation of surface winds through the use of the AOML/HRD H*Wind System. Shown above
is a surface wind representation of Hurricane Ike (2008). This analysis was created from
hurricane reconaissance, buoy, and satellite winds.
One of the many difficulties with forecasting tropical cyclone intensification and track is obtaining an
accurate representation of the current wind field. Without knowledge of the storm's strength and structure,
there will be higher error in computer model, and thus human, forecasts.
Recent advances in remote sensing (the measurement of environmental variables from a remote location) has
led to the ability to measure surface wind speed and direction over oceans from satellites. The SeaWinds
scatterometer (on board QuikSCAT) is an active instrument that sends a pulse of microwave radiation down to the ocean surface.
The pulse backscatters off of capillary (wavelength ~ 1cm) waves on the ocean surface. These surface waves
vary quite nicely with the surface wind stress, which is in turn a function of the surface wind speed and
ocean currents. SeaWinds measures the amount of "power" returned by the ocean surface - more power generally
means a rouger ocean surface and thus higher wind speeds. In addition, wind direction can be determined by
measuring the polarization of the return beam from multiple azimuth angles.
Since tropical cyclones spend most of their time over the ocean (where surface observations are few and
far between), it is immediately obvious that QuikSCAT could be a valuable source of surface wind information.
The satellite retrieves surface wind speed and direction, and covers about 95% of the Earth's surface each day.
However, there is one very large obstable - rain. Rain contaminates the radiative beam in three ways: attenuation,
enhanced backscatter from the drops, and enhanced backscatter from rain splashing on the surface. The
relationships and impacts between these are complicated and nearly impossible to isolate. They vary according
to the intensity of rain and the "true" surface wind speed (which is what you are trying to measure in the first
place!). In tropical cyclones, where rain rates can reach incredible levels, QuikSCAT wind retrievals are
inaccurate at best and worthless in the worst cases.
This project, in collaboration with the Central Florida Remote Sensing Lab (CFRSL), seeks to improve QuikSCAT
wind retrievals in tropical cyclones. A new algorithm developed by Pete Laupattarakasem at UCF has been
tested against H*Wind surface wind analyses. H*Wind incorporates all surface observations near the tropical
cyclone in both space and time and performs an objective analysis to produce a gridded 6 km wind field.
Pete has shown significant improvement in QuikSCAT wind wind retrievals when the algorithm is applied.
In June 2010, UNC Asheville was awarded a sub-contract with UCF to continue this important work.
Related Journal Articles:
Related Conference Preprints:
- Alsweiss, S., R. Hanna, P. Laupattarakasem, W.L. Jones, C.C. Hennon, and R. Chen, 2014:
A Non-MLE Approach
for Satellite Scatterometer Wind Vector Retrievals in Tropical Cyclones. Remote
Sensing,6, 4133-4148, doi:10.3390/rs6054133.
- Laupattarakasem, P., W.L. Jones, C.C. Hennon, I.S. Adams, J.W. Johnson, P.G. Black,
J.R. Allard, and A.R. Harless, 2010: Improved Ocean Vector Winds using
SeaWinds Active/Passive Retrievals, IEEE Transactions on Geoscience and Remote Sensing,
- Adams, I.S., C.C. Hennon, W.L. Jones, and K. Ahmad, 2006: Evaluation of Hurricane
Ocean Vector Winds from WindSat. IEEE Transactions on Geoscience and Remote Sensing,
44, No. 3, 656-667.
- Laupattarakasem, P., W.L. Jones, C.C. Hennon, J.R. Allard, A.R. Harless, and
P.G. Black, 2008: Q-Winds
satellite hurricane wind speed retrievals and H*Wind comparisons.28th Conf.
on Hurricanes and Tropical Meteorology (Orlando FL), American Meteorological
- Adams, I., C.C. Hennon, W.L. Jones, and K. Ahmad, 2005: Hurricane wind vector
measurements from WindSat polarimetric radiometer. IGARRS 2005, IEEE, New York,
Vol. 6, pp. 4014-4017.
- Jones, W.L., I.S. Adams, and C.C. Hennon, 2005: Hurricane wind vector measurements
from WindSat polarimetric radiometer. Proceedings, 59th Interdepartmental Hurricane
Conference, Jacksonville FL.
- Allard, J.R., 2007:
Using H*Wind to Improve Satellite-Based Wind Measurements in Tropical Cyclones, UNCA
Spring Research Symposium, Asheville, NC.
- Hennon, C.C., J.R. Allard, and A.R. Harless, 2007:
Using Objective Analyses (H*Wind)
in Tropical Cyclone Wind Vector Verfication. Ocean Vector Winds Science Team
Meeting,15th AMS Satellite Meteorology and
Oceanography Conference/EUMETSAT Meteorological Satellite Conference, Amsterdam,
- Hennon, C.C., D. Long, and F. Wentz, 2006:
Validation of QuikSCAT Wind Retrievals in Tropical Cyclone Environments. 14th Conference
on Satellite Meteorology and Oceanography, American Meteorological Society, Boston, MA.