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Christopher AlstonMark Baker
Philip Degliomini
Main Objectives
Explain And Interpret Radar Bright Bands Discuss Importance Of The Bright Band Discuss Specific Applications Of The Bright
Band TRMM
Overview Specific Case Study: Detecting Tropical Cyclone
Structural Changes CloudSat
Overview Specific Case Studies: Analysis Of Tropical Systems
What Is A Radar Bright Band?
A Bright Band Is A Melting Layer Of Snow And Ice That Usually Lies Above The Stratiform Type Of Rain.
On The Meteorological Radar, A Bright Band Can Be Seen As A Nearly Horizontal Thin Bright Echo Layer With A Large Radar Reflectivity Factor.
It Is Associated With The Melting Layer Between Rain And Snow
Defines Layered Depth Of Precipitation
Can Be Used To Estimate The Height Of The 0° Isotherm
What Causes Radar Bright Bands?
The Reflectivity Of Liquid Water Is Much Higher Than That Of Ice
Larger Objects Have A Higher Reflectivity Than Smaller Objects
What Causes Radar Bright Bands?
As Snow Falls To Areas Where The Temperature Is Above Freezing, It Will Being To Melt From The Outside-In.
This Will Result In Large Wet Spongy Spheres Being Formed In A Layer Immediately Below The 0° Isotherm.
Image Source: http://wx.db.erau.edu/faculty/mullerb/Wx365/Bright_band/bright_band.html
What Causes Radar Bright Bands?
Thus, These Hydrometeors Maximize Reflectivity And As A Result A Bright Band Appears In The Radar Sounding
Image Source: http://wx.db.erau.edu/faculty/mullerb/Wx365/Bright_band/bright_band.html
A Typical Bright Band Image
Image Source: www.radar.mcill.c
a/bright_band.html
Applications Of Radar Bright Bands Rainfall Retrieval Rates
Difficult To Procure Accurately Use Of PR Improve Estimates The Thicker The Bright Band The More Intense
The Precipitation Can Be Used To Strengthen Rainfall Processes
Modeling Understanding Of How Rainfall Heat Energy
Steers Atmospheric Circulation Changes In Location Of The 0° Isotherm
Effects From ENSO Climate Change Indications
Improve Numerical Weather Prediction
TRMM
Tropical Rainfall Measuring Mission
A Joint Project Between The US and Japan
Launched From Japan And Placed In A Low Earth Orbit
First Satellite That Monitors Rainfall Over The Tropics (35° North to 35° South Latitude)
Image Source: http://nasascience.nasa.gov/missions/trmm
Instruments Of TRMM
Visible And Infrared Scanner (VIRS) Indirect Gauge Of Rain Links Measurements With Other Satellite
Measurements Clouds And Earth Radiant Energy System
Instrument (CERES) Examines Energy Balances Between The Sun,
Space, The Earth’s Surface, Atmosphere, And Clouds.
Lightning Imaging Sensor (LIS) Detects Lightning
Instruments of TRMM
Precipitation Radar Provides Three Dimensional Images Of Storm
Structure Intensity, Distribution Of Rain, Storm Depth, And
Height Of The Melting Layer Improve Global Circulation Models
TRMM Microwave Imager (TMI) Measures The Amount Of Rainfall Can Quantify Water Vapor, Cloud Water, And
Rainfall Intensity
What Makes TRMM Valuable?
First Mission Devoted To Measuring Rainfall In The Tropics/Subtropics Using Space Based Microwave And Infrared Sensors
Additionally, The Precipitation Radar Is The First Space Based Radar For Rainfall
What Makes TRMM Valuable? It Is Difficult To Measure Rainfall Over The Ocean
Two-Thirds Of Global Rainfall Occurs In The Tropics
The Latent Heat Release From Condensation Is The Paramount Force That Drives Circulation In The Troposphere
TRMM Provides Much More Accurate Measurements Of Rainfall Over The Tropics Which Can Be Used To Determine Latent Heat Release
Thus By Understanding Rainfall And Rainfall Variability We Can Gain A Greater Understanding Of Climate Change Across The Globe As Well As The Heat Balances Between The Ocean, Atmosphere, And Land
CloudSat
Provides Images Of The Vertical Structure Of Clouds As Well As Cloud Composition
Cooperative Mission With Canada
On The A-Train
Sun-Synchronous Orbit
Image Source: http://nasascience.nasa.gov/missions/cloudsat
CloudSat
Operates By Taking A Vertical Cross Section From The Top Of The Atmosphere To The Surface Of The Earth
The First Satellite With A Millimeter-Wavelength Cloud Radar
This Cloud Profiling Radar Is Much More Sensitive Than Other Radars
As A Result, CloudSat Can Distinguish Smaller Water And Ice Particles That Provide The Composition Of Clouds
Why Is CloudSat Valuable?
Clouds Are Very Important Meteorologically and Climatologically
Provides Data On Cloud Layer Thickness, Altitudes Of Cloud Tops And Cloud Bases, Optical Properties, And Water And Ice Content Of Clouds
Using This Data Numerical Prediction Models Can Be Improved Which Will Lead To More Accurate Weather Forecasts
Why Is CloudSat Valuable?
Climatologically Speaking, Clouds Are The Most
Prominent Factor In The Earth’s Radiation Budget
Slight Changes In Cloud Cover Will Have
Significant Effects On Prevailing Climate
CloudSat Will Provide A Greater Knowledge Of
Global Cloud Cover, Which Will Lead To A Better
Understanding Of Earth Radiation Balance Which
Will Produce More Accurate Climate Models
CloudSat Products
Can Provide Profiles On Tropical Storms, Mid-Latitude Cyclones, Severe Thunderstorms, And Tornadic Outbreaks
For example, CloudSat Can Show A Tropical Disturbance Develop From A Tropical Depression Into A Tropical Storm
Tropical Cyclone Izilda
Image Source: http://
cloudsat.atmos.colostate.edu/tcs/izilda_0323_2.jpg
Applications Of Radar Bright Bands
Specific Applications That Will Be Highlighted: Using TRMM:
Detecting Tropical Cyclone Structure Bright Band Height Predicating Tropical Evolution
Using CloudSat: Cross Section Bright Band Of Cloud Layers And
Precipitation Case Studies Comparison To Traditional Computer Model
Guidance
Tropical Cyclones (TC) Importance of
temperature anomalies
Extratropical Transition (ET) Strong TC -Warm
Symmetric Core Weakening TC - Cold
Asymmetric Core
San Francisco State University
Extratropical Transition Important in predicating
strength of TC Predicting ET can be
difficult Wind field expansion,
trapped fetch waves, speed
Cyclone Space Phase- Model thermal structure Has helped improve ET
prediction but still process has inherent flaws
Solution Gain insight on tropical cyclone
changes by analyzing bright band heights (BBHs) received from TRMM PR
Procedure- How does this work? Compute BBH perturbations using TRMM to
detect anomalous thermal structure BBH distribution can be used as an indication of
symmetry Rain around core characterized by BB Distribution of rainfall distribution of convection
which tells us about symmetry and ET Strong TC- fairly symmetric BBH distribution, with
the largest perturbations close to the center (warm core)
Weakening TC- asymmetric BBH distribution with the negative BBH perturbations close to the center (ET)
Case Study- Typhoon Meari
Became a typhoon on September 22, 2004.
Reached maximum strength on 9/24/05 at 922MB (Cat 4)
For the next two days it weakened somewhat (showing signs of ET) as it interacted with a upper level trough
Meari made landfall on 9/29/05 in Japan (Cat 1)
Shortly after reaching maximum strength
(Center for Ocean Atmospheric Prediction Studies)
ET occurring and weakening the system
(Center for Ocean Atmospheric Prediction Studies)
FLHs- TC undergoing strong development
(Center for Ocean Atmospheric Prediction Studies)
FLHs- TC weakening quickly due to ET
(Center for Ocean Atmospheric Prediction Studies)
Conclusion
BBHs computed by TRMM have been used to
further improve ET in tropical cyclones
BBH perturbations tell us about the symmetry
and core temperature of a tropical cyclone
Using this data, we are able to more easily
predict ET and better forecast tropical cyclones
Analysis of case studies will show importance to meteorologists in forecasting
Focus on strengths – vertical cross section of clouds and Bright Band (Cloud layers/Precip)
Relevance of CloudSAT Comparison between CloudSAT and
traditional computer model guidance
CloudSAT passed over Cat 4 Hurricane
Bill August 19, 2009 at 12:20 EDT
Central Pressure of 947 mb (hPa)
Maximum sustained winds of 132 mph
Important features CloudSAT picked up that other devices did not
The Advanced Microwave Scanning Radiometer (AMSR-E) reveals a thin cirrus shield throughout the eye wall while the CloudSAT shows a 50 km cirrus free eye wall
CloudSAT depicts the northwestern eye wall to have strong convection cloud tops 16km in altitude which can’t be observed by any other instrument
CloudSAT depicted a “hot tower” which is a cloud that penetrates the Tropical Tropopause layer, meaning large amounts of Latent Heat are released as water vapor condenses to liquid, providing fuel for the system to strengthen, which it did.
The cross-section of CloudSAT shows the eye wall bends backward and then inward likely from northerly shear along the top of the storm, giving us another important piece of information to see how the cyclone is venting
The Aqua IR image doesn’t show the multiple cloud layers throughout the storm
Looking at the Bright Band and Cross Section CloudSAT produced, you can see convection free areas between heavier rain bands
IR imagery indicates strong convection is found throughout the storm, on the north and south edges but the CloudSat track shows the strongest area of convection on the northern edge of system
The cloud layering is indistinguishable from the IR imagery as all of the cloud layer tops appear to be at the same height
Made landfall on China’s south coast on August 5th, 2008 The IR imagery shows a large are of cloud cover, but it’s
hard to tell where EXACTLY where the most intense weather is
The CloudSAT image shows weak reflectivity at the start of the orbit but the latter part of the orbit has a very think area of reflectivity and easy to depict Bright Band indicating heavy rain
The blue areas along the top of the clouds indicate cloud ice, while the wavy blue lines on the bottom center of the image indicate intense rainfall reaching the surface.
CloudSAT’s image gave an idea of how much liquid was in the column which helped the forecaster give a educated rainfall rate approximation
Precipitation rate exceeds 1.18 inches per hour in areas around the Bright Band
Comparing CloudSAT, CPR, and Reflectivity Simulated from ECMWF
Comparison between CloudSAT cross section and modern model representation (European Centre for Medium-Range Weather Forecasts) of reflectivity in the bright band
CloudSAT Data – Higher accuracy, better results
Model Representation – Harder to read, very coarse in nature, more error
Significance of CloudSAT
Shows a trailing cold front that exists as part of a decaying extra tropical cyclone in the Atlantic Ocean southwest of Iceland
CloudSAT track in the red line
CloudSAT picks up the multiple precipitating low level convective showers in the cold air behind the front whereas the ECMWF doesn’t really show this clearly
CloudSAT shows clearly the presence of small scale regions of more intense reflectivity embedded within the region around the bright band and deep convection
The Model Simulation gives a very vague bright band and no specific regions of embedded higher reflectivity
The widespread shallow convective clouds embedded in the cold air behind the front appear to be producing precipitation heavy in certain areas at the surface according to CloudSAT
The post-frontal shallow convection is not successfully resolved by the model. It’s very blurry and you can’t tell exactly where the heavy, light, or any rain is falling
CloudSat reveals unprecedented information about cloud layering structure, the bright band (BB) that arises as a result of melting processes, the shape and size of convective cores, and the presence of precipitation
This cutting edge new technology we have in CloudSAT helps meteorologists and climatologist understand weather phenomena much better than when basic satellites are model simulations were used
I feel that CloudSAT sensitivity to cloud droplets is the most useful and beneficial in profiling tropical cyclones mainly because precipitation is so violent and it picks up every detail throughout the cloud, which no other instrument can do with nearly the accuracy, helping provide a better forecast, and perhaps save lives in flooding situations
"Hurricane Bill Eye Orbital Overpass by Cloudsat." On Orbit | Social Space News and Networking. Web. Dec. 2009. <http://onorbit.com/node/1417>.
"NASA - Severe Tropical Storm Kammuri Comes Ashore on China's South Coast." NASA - Home. Web. Dec. 2009. <http://www.nasa.gov/mission_pages/cloudsat/multimedia/cloudsat-20080806.html>.
"NASA - Severe Tropical Storm Kammuri Comes Ashore on China's South Coast." NASA - Home. Web. Dec. 2009. <http://www.nasa.gov/mission_pages/cloudsat/multimedia/cloudsat-20080806.html>.
National Aeronautics and Space Administration. "NASA FACTS." The Importance of Understanding Clouds. Web. Dec. 2009. <http://www.nasa.gov/pdf/135641main_clouds_trifold21.pdf>.
"Near-Real-Time Applications of CloudSat Data - page 4 | Journal of Applied Meteorology and Climatology." Reference Articles on All Topics. Web. Dec. 2009. <http://findarticles.com/p/articles/mi_7594/is_200807/ai_n32289003/pg_4/?tag=content;col1>.
Posselt, Derek J., Graeme L. Stephens, and Martin Miller. "CLOUDSAT." American Meteorological Society (2008). CLOUDSAT Adding a New Dimension to a Classical View of Extratropical Cyclones. Web. Dec. 2009. <http://ams.allenpress.com/archive/1520-0477/89/5/pdf/i1520-0477-89-5-599.pdf>.
"Space Today Online - CloudSat - Earth Observing System satellite." SPACE TODAY ONLINE - Space Today Online covering Space from Earth to the Edge of the Universe. Web. Dec. 2009. <http://www.spacetoday.org/Satellites/TerraAqua/CloudSatStory.html>.
Curtis, Dr. A. R., Editor. (2004). CloudSat: How clouds relate to Climate. Space Today Online. Retrieved December 4, 2009, from http://www.spacetoday.org/Satellites/TerraAqua/CloudSatStory.html.
Dept. of Atmospheric Science Colorado State University. (2009, September 15). CloudSat overview (online). Retrieved December 5, 2009, fromhttp://cloudsat.atmos.colostate.edu/overview.
Fabry, F. (1995, August). Vertical profiles of reflectivityand precipitation intensity (electronic version). Paper presented at the III International Symposium on Weather Radars, Sao Paulo, Brazil. Retrieved December 4, 2005, from http://www.unesco.org.uy/phi/libros/radar/art08.html.
Fabry, F. (2000, August ). Examples of bright bands (online), Retrieved December 4, 2009, from http://www.radar.mcgill.ca/bright_band.html.
NASA. (2008, November 14). Cloudsat - NASA science missions (online). Retrieved December 4, 2009, from http://nasascience.nasa.gov/missions/cloudsat.
NASA. (2008, February 8). CloudSat, revealing the inner secrets of clouds (online). Retrieved December 3, 2009, from http://www.nasa.gov/mission_pages/cloudsat/main/index.html.
NASA. (2008, September 30). TRMM – NASA science missions (online). Retrieved December 4, 2009, from http://nasascience.nasa.gov/missions/trmm.
NASA & Jet Propulsion Laboratory, California Institute of Technology. (2004, November 11). Tropical Rainfall Measuring Mission (online). Retrieved December 3, 2009, from http://trmm.jpl.nasa.gov/.
Radar Bright Band (online). Retrieved December 5, 2009 from http://wx.db.erau.edu/faculty/mullerb/Wx365/Bright_band/bright_band.html.
Remer, L. & Przyborski, P. (2009, December 5). Tropical Rainfall Measuring Mission, Earth Observatory (online). Retrieved December 5, 2009, from http://earthobservatory.nasa.gov/Features/TRMM/.
Wolff, Christian. (2009). Radar basics (online). Retrieved December 3, 2009, from http://www.radartutorial.eu/index.en.html.
Guimond, Stephen R., Joesph F. Turk, Clay B. Blankenship, and Jeffrey B. Hawkins. "Detecting Tropical Cyclone Structural Change with the TRMM Precipitation Radar (PR) and Advanced Microwave Sounding Unit (AMSU)." American Meteorological Society. Web. Nov. 2009. <ams.confex.com/ams/pdfpapers/103215.pdf>.