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