Latitudinal Gradients in the Earth

1
Latitudinal Gradients in the Earths Energy Budget
2
Solar Flux Impinging on Top of Earths Atmosphere
Solar Flux
Earth
Figure 3.1
3
Spherical Geometry
Figure 3.2
4
Daily Average Insolation (Top of Atmosphere)
Figure 3.3
5
Figure 3.4
Courtesy of NASA ERBE/ Hartmann
6
Annual Mean
Figure 3.5
Courtesy of NASA ERBE/Hartmann
7
Annual Mean
Figure 3.6
Courtesy of NASA ERBE/Hartmann
8
Courtesy of NASA ERBE
9
Annual Mean
Figure 3.7
Courtesy of NASA ERBE/Hartmann
10
Annual Mean Net Radiation
Annual Mean
Figure 3.8
11
How to Calculate the Atmosphere-Ocean Heat Flux
across a Latitude Band
Figure 3.9
Integrate RTOA from the South Pole over the
entire polar cap to calculate the northward heat
flux across a latitude band.
f
l
South Pole
f-p/2
RTOA Shortwave absorbed - Longwave out
Polar Cap
12
Required Atmosphere-Ocean Heat Transport
Figure 3.10
1 PW1015 Watts
Annual Mean
13
Problems with the Use of Radiosonde Data to
Determine Transport

• Strongest poleward eddy-induced heat transport
  occurs where there are few radiosondes, in the
  oceanic storm tracks.

Lau (1978)
Figure 3.11
14
Simplified Atmosphere Governing Equations used
in Data Assimilation
Wind (Fma)
Temperature
Water Vapor
The circled quantities on the right represent the
effects of clouds, radiation, evaporation, and
friction on the atmosphere. These terms represent
sub-gridscale processes and thus must be
parameterized.
Mass Conservation
Vertical Balance (Fma)
Figure 3.12
from Trenberth (1992)
15
Parameterization within Observational Analysis
Models. Example Cumulus Parameterization
300 km

• Cumulus parameterization schemes take grid-scale
  humidity and temperature data from a column of
  grid cells.
• The parameterization tries to simulate the
  population of clouds that might exist within the
  column of cells, and then determines how this
  population of clouds alters the grid-averaged
  temperature and humidity.
• Some newer schemes also account for the effect of
  cumulus clouds on the grid-scale winds.
• Radiation parameterizations then use these
  estimated cloud populations and their effects on
  cloud liquid water to determine cloud-radiation
  interactions.
• This is a very difficult problem

300 km
300 km
Figure 3.13
16
Atmospheric Meridional Heat Transport (As a
Function of Dataset)
TOA Net Radiation
Total and Atmospheric Transports
Differences can be seen depending on what
atmospheric dataset is used.
Figure 3.14
Trenberth and Caron (2001)
17
Atmospheric Meridional Heat Transport as a
Function of Month
From Trenberth and Caron 2001
Atmospheric heat transport largest in winter
hemisphere.
Figure 3.15
18
Direct Ocean Measurements
Temperature and salinity measurements across
ocean transects can be used to measure ocean
heat flux.
Figure 3.16
Ganachaud and Wunsch (2000)
19
Ocean Meridional Heat Transport Calculated Using
Three Different Methods
From Trenberth and Caron 2001
Methods a) and c) Atlantic
Methods a) and b) Atlantic
Methods a), b), and c) World Ocean
Figure 3.17
20
More Recent Partitions of Atmosphere Ocean Heat
Transport (suggest a larger atmosphere role)
RTOA
atm
ocean
Figure 3.18
Trenberth and Caron (2001)