SBDART Santa Barbara DISORT Atmospheric Radiative Transfer Model

1
SBDART Santa Barbara DISORT Atmospheric
Radiative Transfer Model

• Ricchiazzi, Yang and Gautier
• Bulletin of Am. Meteo. Soc.
• 1998

2
What is SBDART?

• A research model allowing accurate computations
  of radiation anywhere in the atmosphere
  (including the surface) given known conditions

SBDART
inputs
outputs
Has a graphical user interface that makes it
extremely easy to use for educational purposes
3
How are we going to use SBDART for this class?

• SBDART is our surrogate climate model
• We will ask scientific questions that can be
  answered quantitatively with SBDART
• We will perform experiments to address these
  questions
• We will analyze the results and estimate whether
  they are reasonable or not based on predictions
  we make based on our knowledge
• We will follow the scientific approach and act as
  scientists

4
How does SBDART work?

• SBDART 1-D model represents one column of the
  atmosphere and the surface
• 1-D model represents the average structure of
  the atmosphere
• The air column is divided into 100 layers
  surface
• Each layer contains climatically important
  constituents (GHGs, aerosols)
• Model is driven by solar radiation at the top of
  the atmosphere (TOA)

5
How does SBDART work?

• An engine to perform computations (complex
  mathematical and physical systems not visible to
  students)
• Data bases for inputs to run computations (solar
  spectrum, various realistic constituents
  concentrations and clouds, various possible
  atmospheric profiles, various possible surface
  types)
• Outputs of runs in the form of tables and
  graphics
• Menu-driven, Click-and-Point interface

6
User Interface
Tabs for various inputs
Scrolling Help text
Input style Selection
Filter selection (wavelength region)
7
User Interface Atmospheric Profile
Menu of atmospheric profiles
Menu of Gas concentrations
Graphic of Profiles (water vapor, ozone,
temperature and pressure)
Menu of Surface types
8
Aerosol Parameters

• Aerosols are particulates or gases emitted by
  human activities or natural sources that scatter
  or absorb radiation
• Amount is expressed in the form of optical depth
• There are three layers of aerosols that can be
  selected 2 tropospheric (background and enhanced
  both with top altitude 10 km) and one
  stratospheric (bottom altitude 10 km) layers
• The different types are
• Background tropospheric Enhanced tropospheric
• Rural (comb) - mineral
• Urban (comb) - soot
• Oceanic - sulfates
• Stratospheric
• Volcanic
• Meteoric dust

9
Interface aerosols
10
Surface Parameters

• The surface impact the radiation as it absorbs or
  reflects it
• Different surfaces affect radiation differently,
  the darker they are the more they absorb, the
  brighter the more they reflect
• Vegetation reflects highly in the near-infrared
• The different types of surfaces that can be
  selected are
• Snow
• Water (clear, lake, sea)
• Sand
• Vegetation
• Another option allows to chose a constant albedo

11
User Interface Cloud Parameters
High cloud
Droplet Size slider
Altitude slider
Middle cloud
Optical Depth slider
Low cloud
12
Cloud Parameters

• Clouds can be at different levels, have different
  thicknesses (specified by bottom and top
  altitude), different concentration of droplets
  (specified by optical depth tau - t) and
  different cloud droplet size distributions
  (specified by effective droplet size)
• A graphic at the bottom of the interface shows
  the specified clouds altitude and thickness

13
User Interface - Run Model
Run Name
Detailed Run Description
Type of Computations of vertical profiles
14
Run Model
Two types of runs can be made

• Vertical profiles (variations with altitude) for
• Flux Up (upward flux) SBDART_Conceptual_Model.ppt
• Conceptual_Model_cloudy_sky.ppt
• Flux Down (downward flux)
• Direct Beam Flux (downward direct flux)
• Net Flux (downward flux minus upward flux)
• Heating Rate Heating_Rate.ppt

• Repetitive sets of computations for
• Top up, down, direct
• Bottom up, down, direct
• As a function of
• Hour of the day
• Latitude
• Longitude
• Solar zenith angle
• CO2, CH4, N2O concentrations
• Visibility
• wavelength

15
User Interface - Plot Model Runs
Graphics overlaid
List of runs
View runs highlighted
Modifyable Axis boundaries
Delete runs highlighted
Info about latest run highlighted
Copy plot to clipboard for use in word or
photoshop
Print info
Save all runs
Save plots to a file