Hye-Yun Kim

IMSG at NOAA/NESDIS/STAR

Outline ABI SW Radiation Budget (SRB) algorithm

Evaluation of retrieved SW radiation

ABI SRB algorithm demonstration with AHI

Summary

Advanced Baseline Imager (ABI) SRB algorithm GOES-R series ABI SRB algorithm is

RT-based, hybrid algorithm combines direct path and indirect path to retrieve Downward SW Radiation at Surface

(DSR) Reflected SW Radiation at TOA

(RSR) DSR and RSR are determined

separately for clear and cloudy scenes and outputs are the cloud-fraction weighted averages during daytime

ABI SRB algorithm: direct path When a complete description of the

atmospheres and surfaces is available from ABI derived products

Uses GOES-R products (AOD, COD, surface albedo etc.) as inputs to calculate reflectance and transmittance

Straightforward computation with low latency

More consistent with other ABI products

No retrievals when input product is missing

May not conserve energy at TOA

Reflected by atmosphere

Reflected by surface and transmitted through the atmosphere

Absorbed by atmosphere

Transmitted through atmosphere

Incoming Solar Radiation

ABI SRB algorithm: indirect path Used when direct path can not be applied Uses ABI TOA reflectances in multiple

channels as input to calculate RSR and DSR is obtained by estimating atmospheric transmittance from TOA albedo

Clear sky composite is calculated as the median of 28 days of clear sky albedo

Conservation of energy at TOA is attempted

Uses broadband TOA albedo that requires spectral and angular corrections, which introduce uncertainties

Illustration of retrieval of transmittance from TOA albedo (reflectance) for the geometry and atmospheric condition shown (no surface effects). The clear-sky/cloudy-sky transmittance is ~0.69/0.28 corresponding to the TOA albedo of 0.1/0.5.

0.0 0.2 0.4 0.6 0.80.0

0.2

0.4

0.6

0.8

0: 0.6H20: 2.0 g cm

-2

O3: 0.3 atm-cmAerosol: CONT-I (: 0.0-1.5)Cloud: water (: 0-80)Cloud top: 5.5 kmCloud bottom: 2kmSurface albedo: 0

Shortwave Transmittance vs. TOA Reflectance

Cloudy sky Clear sky

Tran

smitt

ance

Reflectance

Outline ABI SW Radiation Budget (SRB) algorithm

Evaluation of retrieved SW radiation

DSR and RSR using MODIS

ABI algorithm demonstration with AHI

Summary

PROXY data MODIS/Terra, Aqua Simulated ABI data GOES Surface Insolation Product (GSIP) Advanced Himawari Imager/Himawari-8 Spinning Enhanced Visible and InfraRed Imager/MSG

PROXY data MODIS Terra/Aqua; period covered 2000/2002 2015

TOA reflectance (from MOD/MYD02),

Geometry (from MOD/MYD03), Surface elevation (from

MOD/MYD03), Aerosol optical depth (from

MOD/MYD04), Cloud optical

depth/size/height/phase (from MOD/MYD06),

Ozone (from MOD/MYD07), Total precipitable water (from

MOD/MYD07, NCEP Reanalysis),

Snow mask (from MOD/MYD10),

Surface albedo (from MCD43C3)

Reference Data Ground data for DSR

NOAA Surface Radiation Network (SURFRAD): 2000 2015

CERES Ocean Validation Experiment (COVE): 2000 2013

Baseline Surface Radiation Network (BSRN): 2000 2009

CERES TOA observation for RSR Cloud Radiation Swath (CRS): 2000

2009 Single Scanner Footprint (SSF): 2010

2015

ABI SRB algorithm validation Collocation process for evaluation

Retrievals are collocated with: Ground measurement for DSR CERES TOA observation for RSR

Retrievals are averaged spatially (25km) Ground measurements are averaged temporally (30min)

Monthly instantaneous DSR

ABI SRB algorithm with MODIS data DSR at 25km

Overestimation in cloudy Underestimation in clear sky

RSR at 25km

Cloud fraction difference between

proxy and reference data causes retrieval error

Error over scene type DSR

RSR

Blue: Indirect path Red: Direct path

Demonstration with AHI data Sept 29th 2015 00:00

12:30 UTC, every 30 minutes

Gridded 2km Inputs:

AHI TOA reflectances: chn 1, 3-6 Uses ABI narrow-to-

broadband (NTB) coefficients

CHN4 coefficient is not used

Cloud-mask product, surface height, TPW, and ozone from GFS

Demonstration with AHI data

9/29/2015

Summary The ABI SW Radiation Budget algorithm uses two

paths depending on availability of ABI products and runs during daytime only.

Direct and indirect path are evaluated with MODIS data at 25km: both algorithm shows almost the same retrieval

error in RSR retrieval direct path shows slightly better estimation for DSR

retrieval

Thank you

kimsc_2015_v2.5_part1ABI SW Radiation Budget (SRB) Algorithm and Validation OutlineAdvanced Baseline Imager (ABI) SRB algorithmABI SRB algorithm: direct pathABI SRB algorithm: indirect pathOutlinePROXY data PROXY dataReference DataABI SRB algorithm validationABI SRB algorithm with MODIS dataError over scene typeDemonstration with AHI dataanimation_2Demonstration with AHI dataDemonstration with AHI datakimsc_2015_v2.5_part2SummarySlide Number 2