Integration of Advanced Integration of Advanced Satellite Cloud Products into Satellite Cloud Products into an Icing Nowcasting Systeman Icing Nowcasting System

Julie Haggerty, Gary Cunning, Ben Bernstein, Michael Chapman, Julie Haggerty, Gary Cunning, Ben Bernstein, Michael Chapman, David Johnson, Marcia Politovich, Cory WolffDavid Johnson, Marcia Politovich, Cory WolffNational Center for Atmospheric Research National Center for Atmospheric Research

Boulder, Colorado USABoulder, Colorado USA

Patrick Minnis and Rabindra PalikondaPatrick Minnis and Rabindra PalikondaNASA Langley Research Center, Hampton, Virginia USANASA Langley Research Center, Hampton, Virginia USA

WWRP Symposium on Nowcasting and Very Short Range Forecasting, 5-9 September 2005

The NCARThe NCARCurrent Icing Potential (CIP) Current Icing Potential (CIP)

System:System:A Basic DescriptionA Basic Description

Hourly diagnosis of icing potential Hourly diagnosis of icing potential and the potential for supercooled and the potential for supercooled large drops over a three-large drops over a three-dimensional domain over the dimensional domain over the continental United Statescontinental United States

Experimental version estimates Experimental version estimates icing severityicing severity

Data sources include surface Data sources include surface observations, pilot reports, model observations, pilot reports, model forecasts, radars, and lightning forecasts, radars, and lightning sensorssensors

Limited satellite data currently Limited satellite data currently used (cloud mask and cloud top used (cloud mask and cloud top temperature)temperature)

CIP Icing Potential at 825 mb16 February 2005 at 1600 UTC

NASA Langley Satellite-derived NASA Langley Satellite-derived Cloud ProductsCloud Products

GOES Imager visible, GOES Imager visible, near-infrared, and infrared near-infrared, and infrared channelschannels

Products include cloud Products include cloud droplet phase, liquid water droplet phase, liquid water path, particle size path, particle size

These variables can These variables can indicate possible icing indicate possible icing conditions conditions potential potential improvement to CIP improvement to CIP products products

Represent conditions Represent conditions primarily near cloud topprimarily near cloud top Liquid water path at 1615 UTC on

16 February 2005 as derived from GOES-12 imagery.

Integration PlanIntegration PlanCIP-Satellite Cloud ProductsCIP-Satellite Cloud Products

Forecasters’ experience using satellite productsForecasters’ experience using satellite products Selection of satellite products likely to improve Selection of satellite products likely to improve

icing detection, i.e., phase, liquid water path, icing detection, i.e., phase, liquid water path, particle sizeparticle size

Objective assessment of satellite productsObjective assessment of satellite products Modification of CIP algorithms to include satellite Modification of CIP algorithms to include satellite

productsproducts Case studies using modified version of CIPCase studies using modified version of CIP Refinement of integration methodsRefinement of integration methods

Satellite Product ValidationSatellite Product Validation

Case studies – comparison of phase, LWP, Case studies – comparison of phase, LWP, cloud top height, particle size with research cloud top height, particle size with research aircraft and ground-based radiometer dataaircraft and ground-based radiometer data

Long-term intercomparison of satellite and Long-term intercomparison of satellite and CIP products with pilot reportsCIP products with pilot reports

Statistical characterization of satellite Statistical characterization of satellite products to verify forecasters’ guidelinesproducts to verify forecasters’ guidelines

Satellite-Aircraft Comparisons from AIRS-II

Cloud Phase

0

1

2

3

4

5

0 1 2 3 4 5

Aircraft-derived category

Sat

ellit

e-d

eriv

ed c

ateg

ory

1 = liquid1.5 = mixed2 = ice4 =clear

(10)

(3)

(1) (1)

(2)(2)

Aircraft cloud-top penetrations

• 13 aircraft-detected liquid cases

−10 classified correctly by satellite

− 2 classified as ice (overlying cirrus?)

− 1 as clear (varied conditions)

• 2 aircraft-detected mixed phase cases

− both classified as ice by satellite

• 4 aircraft-detected ice cases

− 3 classified correctly by satellite

− 1 classified as clear

MWR Mean = 238.5

GOES Mean = 264.0

MWR Stddev = 156.6

GOES Stddev = 169.2

Correlation coefficient = 0.72

AIRS-II: LWP at Montreal

0

100

200

300

400

500

600

700

800

900

0 100 200 300 400 500 600 700 800 900

GOES-derived LWP (g/m^2)

MW

R L

WP

(g

/m^

2)

Comparison of Satellite Product with Ground-based Microwave Radiometer

CIP Icing Severity IndexCIP Icing Severity Index

Severity product intended Severity product intended to characterize rate of ice to characterize rate of ice accumulation accumulation

Current data sources are Current data sources are model estimates (vertical model estimates (vertical velocity, liquid water, velocity, liquid water, temperature), pilot reports, temperature), pilot reports, and CIP icing potentialand CIP icing potential

Good candidate for Good candidate for improvement by advanced improvement by advanced satellite products because satellite products because of liquid water and particle of liquid water and particle size dependence size dependence

Severity Severity IndexIndex

DefinitionDefinition

00 No icingNo icing

0.1250.125 TraceTrace

0.250.25 Trace-lightTrace-light

0.3750.375 LightLight

0.50.5 Light-moderateLight-moderate

0.6250.625 ModerateModerate

0.750.75 Moderate-severeModerate-severe

0.8750.875 HeavyHeavy

11 SevereSevere

Case StudiesCase StudiesNortheastern United StatesNortheastern United States

Six cases identified with icing conditions and in situ Six cases identified with icing conditions and in situ measurements by a research aircraftmeasurements by a research aircraft

16 February 2005; non-precipitating, single layer 16 February 2005; non-precipitating, single layer stratus cloud; cloud top temperature -10 to -15 stratus cloud; cloud top temperature -10 to -15 ººCC

19 January 2005; widespread liquid cloud with high 19 January 2005; widespread liquid cloud with high liquid water content; cloud top temperature -10 liquid water content; cloud top temperature -10 ººCC

Adjustment of CIP Severity Index Adjustment of CIP Severity Index with Satellite Productswith Satellite Products

Cloud drop phase, 16 February 2005, 1545 UTC

Phase product locates pixels with liquid or supercooled liquid at cloud top

LWP product LWP product assumed to represent assumed to represent liquid water content in liquid water content in highest cloud layerhighest cloud layer

Adjustment of CIP Severity Index Adjustment of CIP Severity Index with Satellite Productswith Satellite Products

Liquid Water Path, 16 February 2005, 1545 UTC

Adjustment of CIP Severity Index Adjustment of CIP Severity Index with Satellite Productswith Satellite Products

Empirical scaling factor used to estimate Empirical scaling factor used to estimate liquid water content (LWC) in cloud layer liquid water content (LWC) in cloud layer using LWP estimateusing LWP estimate

New severity index calculated from LWC New severity index calculated from LWC estimate for pixels with positive icing estimate for pixels with positive icing potentialpotential

Original CIP severity index adjusted upward Original CIP severity index adjusted upward or downward by half the difference or downward by half the difference

CIP Icing Severity Index 16 February 2005 at 1600 UTC

Original estimate Modified by inclusion of satellite-derived phase and liquid water path products

Areas of high LWP

CIP Icing Severity Index 19 January 2005 at 1915 UTC

Original estimate Modified by inclusion of satellite-derived phase and liquid water path products

Interim Conclusions and Interim Conclusions and Future WorkFuture Work

Advanced satellite products appear to have skill in Advanced satellite products appear to have skill in estimating icing-related cloud variablesestimating icing-related cloud variables

Integration of phase and LWP products for Integration of phase and LWP products for adjustment of CIP severity index produces results adjustment of CIP severity index produces results consistent with aircraft measurementsconsistent with aircraft measurements

Analysis of additional, more complex cases Analysis of additional, more complex cases Refinement of integration methods and use of Refinement of integration methods and use of

additional products such as particle sizeadditional products such as particle size