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

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