Microwave Remote Sensing of Hurricanes & Tropical

MeteorologyTyler Adams and Megan Leigh

Abstract

Remote sensing is a major contributor to the prediction and forecasting of hurricanes. By use of satellite imagery we can look at the key ingredients in hurricane formation as well as growth and sustainability. A disturbance of the African coast, Sea surface temperatures, and moisture levels seen in the water vapor loops are important components that remote sensing allows us to see. At different stages of the Hurricane lifespan, we use different types of remote sensing, including both passive and active sensors. Examples this project will detail include, SAR, SeaWinds, TRMM.

Outline

• Introduction to Hurricanes

• Why is RS of Hurricanes important?

• History of Microwave Remote Sensors

• Scatterometers

• SAR

• Microwave radiometer

• Rain radar (TRMM)

• Hurricane—A tropical cyclone with 1-min average surface (10 m) winds in excess of 32 m s−1 (64 knots) in the Western Hemisphere (North Atlantic Ocean, Caribbean Sea, Gulf of Mexico, and in the eastern and central North Pacific east of the date line).

http://www.aoml.noaa.gov/general/WWW000/text/Pop_Dead.html

Why is RS of hurricanes important?

http://www.sip.ucar.edu/pdf/01_Hurricane_Forecasting_the_State_of_the_Art.1.pdf

Why is RS of hurricanes important?

Why is RS of hurricanes important?

• Little was known about hurricanes before remote sensing.

• Hurricanes such as the 1900 Galveston hurricane killed many because people had no idea there was a storm coming

• As technology improved, ships radar systems (as explained later) sent information back to the US, but that still wasn’t enough warning and wasn’t reliable.

• Hurricane related deaths have drastically declined in the last 100 years.

The 1st Radars• AN/APQ-13 radars were a ground scanning radar developed by

Bell, Western Electric, and MIT as an improved model of the airborne H2X radar. They were used on B-29's during World War II in the Pacific theater for high altitude area bombing, search and navigation.

The AN/CPS-9 radar, the first radar specifically designed for meteorological use, was unveiled by the Air Weather Service in 1954.

The AN/APS-2F radar began as a military aircraft radar. Some of the USA's first weather radars were modified APS-2F radars.

WSR-57 radars were the USA's main weather surveillance radar for over 35 years. The National Weather Service operated a network of this model radar across the country, watching for severe weather.

• Hurricane Alice• Formed:

• Dec. 1954

• Dissipated:• Jan 1955

Image of PPI scope of SPS-6 radar onthe USS MIDWAY showing rare January hurricane northeast of British Virgin Islands. This was hurricane Alice.

Old School Style

How is MRS useful?

• Varied frequencies can measure different variables :1.) Low frequencies (<14 GHz) can measure at

the surface because they are not absorbed by clouds and rain

2.) Higher frequencies (20-35 GHz) are absorbed by clouds and rain, thus allowing us to measure them

3.) At a 22GHz frequency, we can measure the amount water vapor in the atmosphere

Scatterometers• Tells us the ocean vector winds• Operate on polar orbiting satellites• Measures the amount of backscatter

received• Backscatter depends on ocean

surface roughness– Rough surface backscatters more energy

– Smooth surface absorbs more energy

• Provide wind speed and direction– Direction based on multiple beams (Ex.

QuikSCAT operates two beams, 6º apart)SeaWinds launched 1999

QuikSCAT

• Launched June 19, 1999• Altitude 800 kilometers • Sun-synchronus

– One pas every 101 minutes

• Platform for SeaWinds

QuikSCAT

Products of Scatterometers

• Specialized microwave radar that measures near-surface wind speed and direction under all weather and cloud conditions over Earth's oceans.

• Launched on QuikSCAT in 1999• Covers 90% of the Earths oceans (non-ice surfaces)

regardless of cloud cover• Provides wind speed/direction at 25-Km resolution• 1,800-kilometer swath during each orbit • Low frequencies (13.4 GHz) • http://winds.jpl.nasa.gov/

SeaWinds map of wind flow in the Gulf of Mexico and the Atlantic during Hurricane Floyd

Synthetic Aperture Radar (SAR)

• Similar to scatterometers by relying on ocean surface roughness to calculate wind speeds

• Provide better, higher resolutions• Due to observations coming from only one angle,

wind direction is difficult to measure• Very little effects even from very thick cloud cover• http://earth.esa.int/ers/eeo4.128/• http://southport.jpl.nasa.gov/desc/imagingradarv3.

html

ASAR (Advanced SAR)

• Aboard ENVISAT• High Resolution: 30 meters• Scan SAR

– Use of several beams to provide a larger image

• Excellent for Measuring Boundary Layer Rolls• Possible to measure ocean currents as well as

smaller atmospheric events• http://envisat.esa.int/handbooks/asar/CNTR5-2.ht

m

ASAR/MERIS

Special Sensor Microwave Imagers (SMM/I)

• Operate at higher frequencies (19-85 GHz), both horizontal and vertical polarizations

• The 22 GHz frequency operates only vertically (water vapor)

• Sun-synchronous orbits• Flew onboard the Defense Meteorological

Satellite Program (DMSP)

SMM/I

Advanced Microwave Scanning Radiometer

• Onboard Aqua Satellite• Measure Frequencies ranging from 6 to 89

GHz• Primary purpose is to measure precipitation

rates, water vapor, moisture, SST, etc.• Secondary purpose is to measure sea

surface winds• Resolution varies by frequency: 5-55 km• Swath nearly 1,500 km wide

AMSR

Stepped-Frequency Microwave Radiometer (SFMR)

Stepped-Frequency Microwave Radiometer (SFMR)

• Measurement of Surface Winds & Precip. Rates within a Tropical Cyclone (4.6-7.2 GHz)

• Measures Sea Brightness Temperature• Useful in measuring the Wind Radii (eye)

expansion or contraction

http://www.403wg.afrc.af.mil/library/factsheets/factsheet.asp?id=8314

Tropical Rainfall Measuring Mission (TRMM)

• Precipitation Radar (PR)• TRMM Microwave Imager (TMI)• Visible and InfraRed Scanner (VIRS)• Cloud and Earth Radiant Energry Sensor (CERES)• Lightning Imaging Sensor (LIS)

Precipitation Radar (PR)

• Provides a 3-D look at rainfall within a storm system

• Detects precipitation up to 20 km high• Can decipher rain echos up to .25 km high• Horizontal Swath of 250 km and resolution

of 3 miles

TRMM Microwave Imager (TMI)

• Passive Microwave Instrument• Similar to SMM/I with a frequency to

acquire an improved observation of heavy rainfall

• Higher resolution due to lower altitude• Rainfall rates are more accurate over water

than land

PR & TMI at Work

• http://trmm.gsfc.nasa.gov/trmm_rain/Events/ATLA/ATLA.2007-9-28T0327Z________LORENZO.qt

Visible InfraRed Scanner

• Uses both Visible and Infrared radiation to create images

• Based on observed temperatures cloud tops are determined– Useful in the tropics where there are many

thunderstorms

• Wider swath than the other instruments:– 833 km wide compared to 247 km (PR)

• Higher resolution: 2.4 km

VIRS to PR Comparison

Conclusions

Within the last 20 years, Remote sensing of hurricanes and tropical storms has improved drastically, thereby improving forecasting and warnings.

Future work

References

• http://www.terrapub.co.jp/journals/JO/pdf/5801/58010137.pdf

• http://ams.allenpress.com/perlserv/?request=get• abstract&doi=10.1175%2F1520-

0426(2002)019%3C2049%3AEOWVOB%3E2.0.CO%3B2&ct=1

• http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0426(1998)015%3C0809%3ATTRMMT%3E2.0.CO%3B2

• http://earth.esa.int/ers/eeo4.128/• http://cat.inist.fr/?aModele=afficheN&cpsidt=17549790• http://ieeexplore.ieee.org/iel5/6913/18663/00860490.pdf• http://adsabs.harvard.edu/abs/2001AGUFMOS31A0386F