Remote Sensing
Slide 1: Title
Radar Bright Bands And Applications In Meteorology And Climatology
Slide 2: 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
Slide 3: 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.
Slide 4: Radar bright band
• An Area Of Higher Reflectivity Within A Radar “Sounding”
•
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
Slide 5: What causes?
• The Reflectivity Of Liquid Water Is Much Higher Than That Of Ice
•
Larger Objects Have A Higher Reflectivity Than Smaller Objects
Slide 6: Ditto
• 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 (large ice-centered pellets covered
in a layer of liquid water) Being Formed In A Layer Immediately Below The 0°
Isotherm. (picture)
Slide 7: Again
(Using picture) Additionally, as the wet spongy spheres continue to fall they will
continue to melt and obviously decrease in size and will fall faster, which will lessen the
reflectivity right below the bright band.
• Thus, These Hydrometeors Maximize Reflectivity And As A Result A Bright
Band Appears In The Radar Sounding
Slide 8: Typical Example
-VPR (vertical reflectivity profile) signal is affected by precip, thus less reflectivity
behind melting layer.
-As you can see, an area of strong reflectivity just under 3 km. Thus we can assume the 0
degree isotherm is at about 3000 meters from the ground. Can also determine the strength
of the precip falling which has its obvious importance.
-Important to know for type of precip (rain/snow). Freezing layer height determines
whether or not hail will form.
Slide 9: Applications
• 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
RRR – Especially difficult over oceans where traditional land based measurement
methods are not practical/applicable. Rainfall heat energy is the largest and most
important energy source for driving global atmospheric circulations. Important For Flood
Prone Areas…Deployment of resources, evac strategies, etc
ZDI – See The effects of ENSO to understand further,
NWP – Clouds influence on the weather
Others – Applications in disaster management, air quality, water management, amongst
others…
Slide 10: 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)
Slide 11: 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
But the most important are…
Slide 12: Important 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
PR – Use estimates of the heat released into the atmosphere at different heights to
improve GCM.
TMI – Passive Microwave sensor. Measures amount of microwave energy emitted by
earth/atmosphere. By carefully measuring this microwave energy emitted by the Earth
and its atmosphere, TMI will be able to quantify the water vapor, the cloud water, and the
rainfall intensity in the atmosphere.
Slide 13: TRMM’s Value
• 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
The PR measures the echo backscattered from rain, the PR produces very accurate
estimates of rain profiles.
Slide 14: TRMM’s Value continued
• 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
Slide 15: 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
Slide 16: 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
Slide 17: CloudSat’s Value
• 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
Slide 18: Climate-wise
• 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
Slide 19: CloudSat Products
• Can Provide Profiles On Tropical Storms, Mid-Latitude Cyclones, Sever
Thunderstorms, And Tornadic Outbreaks
•
For example, CloudSat Can Show A Tropical Disturbance Develop From A
Tropical Depression Into A Tropical Storm
Slide 20: Tropical Storm Izilda
The intense developing convection is evident from the orange and red reflectivities in the
center of the core convection.
Tropical depression developed between Africa and Madagascar. Developed with winds
on 60 MPH just shy of a cat 1 tropical cyclone.
Just a preview of Mark Bakers Project
Slide 21: Specific Applications
• 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 (Hurricane bill and Tropical Cyclone Kammuri)
– Comparison To Traditional Computer Model Guidance