ATS 761 – Project 3 SBDART

Brian Freitag

12/04/2014

Introduction

• SBDART computes plane-parallel radiative transfer within the Earth’s atmosphere and the surface. – Built to improve upon the treatment of the cloudy

atmosphere in LOWTRAN-MODTRAN – Can analyze a wide variety of radiative transfer problems

within satellite remote sensing and atmospheric radiation budget studies.

– 6 different atmospheric profiles (same as LBLRTM) – 5 different surface types (ocean, lake, vegetation, snow,

and sand) – Molecular absorption depends on low-resolution band

models developed for LOWTRAN atmospheric transmission code.

Objectives

• Recreate 5 examples given in Ricchiazzi introduction document

– Verification SBDART program is running correctly

– Understand the functionality of the SBDART program

• How does downward surface irradiance change with varying droplet radii and cloud height?

• How does the upwelling radiance vary in the presence of a cloud deck, but with different albedo surfaces?

Methods

• Run SBDART code for five different examples given in Ricchiazzi introduction manual – Included wavelengths from 0.25-20 μm to get both

shortwave and longwave spectrum

– Used tropical atmosphere and the sea surface albedo setting

– For Example 3 changed both cloud height and cloud droplet effective radius to 2 km and 100 μm

– For Example 5 changed surface albedo and atmosphere to snow/sand and subarctic winter/tropical

Results – SW Spectral Irradiance

Input: idatm = 4 isat = 0 wlinf = 0.25 wlsup = 4.0 wlinc = 0.05 iout = 1

Results – Optical Depth and Surface Albedo

Input: albcon = 0, 0.2, 0.4, 0.6, 0.8, 1.0

tcloud = 0, 1, 2, 4, 8, 16, 32, 64

idatm = 4 isat = 0 wlinf = 0.55 wlsup = 0.55 isalb = 0 iout = 10 sza = 30

Results – Optical Depth and Surface Albedo

Input: albcon = 0, 0.2, 0.4, 0.6, 0.8, 1.0

tcloud = 0, 1, 2, 4, 8, 16, 32, 64

idatm = 4 isat = 0 wlinf = 0.55 wlsup = 0.55 isalb = 0 iout = 10 sza = 30

Results – SW and LW spectral output – z = 8 km and re = 10 μm

Input: tcloud = 0, 1, 5 zcloud = 8 nre = 10 idatm = 0 wlinf = 0.25 wlsup = 20 wlinc = -0.05 iout = 1 sza = 0

Results – SW and LW spectral output – z = 2 km and re = 10 μm

Input: tcloud = 0, 1, 5 zcloud = 2 nre = 10 idatm = 0 wlinf = 0.25 wlsup = 20 wlinc = -0.05 iout = 1 sza = 0

Results – SW and LW spectral output – z = 8 km and re = 100 μm

Input: tcloud = 0, 1, 5 zcloud = 8 nre = 100 idatm = 0 wlinf = 0.25 wlsup = 20 wlinc = -0.05 iout = 1 sza = 0

Results – Bi-spectral radiances for varying cloud properties

Input: tcloud = 0, 1, 2, 4, 8, 16, 32, 64, 128

nre = 2, 4, 8, 16, 32, 64, 128

isat = 0 wlinf = 0.55, 2.16 wlsup = 0.55, 2.16 isat = 0 isalb = 4 iout = 10 sza = 0

Results – Radiance Input: tcloud = 5,10 zcloud = 1 wlinf = 0.55 wlsup = 0.55 idatm = 1 isalb = 4 sza = 60 iout = 23 nstr = 16 uzen = 0, 15, 32, 45, 60, 70, 80, 89, 91, 100, 110, 120, 135, 148, 165, 180

phi = 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180

Results – Radiance for snow vs. sand

Input: tcloud = 5 zcloud = 1 wlinf = 0.55 wlsup = 0.55 sza = 60 iout = 23 nstr = 16 uzen = 0, 15, 32, 45, 60, 70, 80, 89, 91, 100, 110, 120, 135, 148, 165, 180

phi = 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180

SAND idatm = 1 isalb = 5

SNOW idatm = 5 isalb = 1

Discussion

• Recreated all of the exercises in the Ricchiazzi introduction document

• Results for the downward surface irradiance – Longwave irradiance changes significantly with cloud

height, but not with effective radius (increases)

– Shortwave irradiance changes significantly with effective radius, but not with cloud height (increases)

• Results for the upwelling radiance – Increased radiance using snow albedo flag compared to

sand.

– Similar patterns to sea water flag; different magnitudes