General circulation parameters in the Northern Hemisphere are calculated using atmospheric thermal structure obtained from Nimbus 3 SIRS multi-channel radiance information. The thermal structure up to 10 mb is obtained by using a regression technique with thickness between pressure levels as the dependent variable. General circulation parameters calculated on a daily basis include zonal and eddy available potential energy, and zonal and eddy kinetic energy. A second set of calculations is performed using National Meteorological Center grid data. A comparison of the two sets of calculations indicates that, although the energies calculated from the SIRS-derived structure underestimate the actual energies, maxima, minima, and trends are well identified. An example of mid-stratospheric energy changes during a breakdown of the polar-night vortex is also given

Reiter, E. R.

English

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Intel-hemispheric Comparison of Atmospheric Circulation
Features as Evaluated from NIMBUS Satellite Data
Semi-Annual Report
1 July 1972 - 31 December 1972
Grant NCR 06-002-098
DEPARTMENT OF ATMOSPHERIC SCIENCE
STATE UNIVERSITY
FORT COLLINS, COLORADO
https://ntrs.nasa.gov/search.jsp?R=19740002238 2020-03-23T14:13:05+00:00Z
SEMI-ANNUAL REPORT
for
Grant NCR 06-002-098
1 July 1972 - 31 December 1972
Prepared by
E. R. Reiter, Principal Investigator
Department of Atmospheric Science
Colorado State University
for
National Aeronautics and Space Administration
Contracting Officer: Mrs. G. Wiseman
Technical Monitor: Dr. V. Salomonson
General Circulation Parameters in the Troposphere and Stratosphere
as Calculated from SIRS-derived Thermal and Mass Structure
by
R. F. Adler
(Department of Atmospheric Science
Colorado State University
Fort Collins, Colorado
April 27, 1973
Abstract
General circulation parameters in the northern hemisphere are calcu-
lated 'using atmospheric thermal structure obtained from Nimbus III SIRS
multi-channel radiance information. The thermal structure up to 10 mb
is obtained by using a regression technique with thickness between
pressure levels as the dependent variable. General circulation parameters
calculated on a daily basis include zonal and eddy available potential
energy, and zonal and eddy kinetic energy. A second set of calculations
is performed using National Meteorological Center (NMC) grid data. A
comparison of the two sets of calculations indicates that, although the
energies calculated from the SIRS-deriyed structure underestimate the
actual energies, maxima, minima, and trends are well identified. An
example of mid-stratospheric energy changes during a breakdown of the
polar-night vortex is also given.
1. Introduction
The advent of satellite multi-channel radiance information, such as
from £he SIRS experiment, and the development of techniques to retrieve
atmospheric structure from the radiances, present possibilities not only
for operational uses, but for research into the global general circulation.
While the general circulation of the northern hemisphere has been the
subject of many studies, the general circulation of the troposphere and
stratosphere of the southern hemisphere has been relatively unstudied
because of the lack of a dense hemispheric radiosonde network. The ability
to obtain atmospheric structure on a hemispheric basis from the satellite
data opens up the possibility of making general circulation calculations
in the southern hemisphere. Before making these calculations in the
southern hemisphere, calculations in the northern hemisphere should be
made using structure derived from both SIRS data and conventional data.
The comparison of the two sets of computations will indicate the
limitations of the calculations based on the satellite information. The
purpose of this paper is to show examples of comparisons between calcula-
tions made from both sources of data and to show an example of energetics
calculations during a stratospheric polar vortex breakdown based on SIRS-
derived structure.
2. Techniques Used to Obtain Structure from SIRS Data
Atmospheric thermal structure is obtained from the NIMBUS III SIRS
radiances using a regression technique similar to that of Smith, WooIf
and Jacob [3] . However, instead of using the temperature of particular
pressure levels as the dependent variable, the thickness between pressure
surfaces is used. The height difference between pressure surfaces is, of
course, proportional to the layer-mean temperature. For the regression
analysis}the data is divided into three latitude bands: 20 -40 N,
40 -60 N, and 60 -80 N. Eight layers in the vertical are used from
10 mb to 1000 mb. Cloud-contaminated data is climated by checking the
radiances in channel 2 (750 cm ) and channel 3 (714 cm ) against pre-
determined limits which are a function of latitude. If the observed
radiances in both channels fall below the limits, the data is eliminated
as cloud-contaminated. The radiance limits are selected by comparing
observed SIRS radiances and satellite cloud photographs.
The regression equations are obtained using a near-simultaneous
matchup of SIRS radiances and thicknesses obtained from the NMC northern
hemisphere fields for the layers below 100 mb, and from station data for
the layers above 100 mb. The root mean square errors of the regression
equations are comparable to those of Smith, Woolf and Jacob [3] with
errors of from 2-4 K. Geopotential height data is obtained by adding
the thicknesses derived from the SIRS data to an NMC hemispheric 1000 mb
height field.
3. Comparison of General Circulation Parameters
General circulation parameters calculated include the zonal and
eddy available potential energy (AZ and AE, respectively) and the zonal
and eddy kinetic energy (KZ and KE, respectively). The calculations are
made on a daily basis for the month of January, 1970, and are done using
a 5° by 5° latitude-longitude grid between 20°N and 80°N. The NMC data
is linearly interpolated from the NMC grid to the latitude-longitude
•
grid. The SIRS-based data is also linearly interpolated from satellite
track positions to the latitude-longitude grid. Satellite data is com-
bined for 24 hour periods centered on 1200Z to obtain substantial hemispheric
coverage.
The formulations used in the calculations are as follows:
8 .
 d21=1
8 [lujjjl + [v.]*]
KZ = E 1 X 1 A *•* AP (3)
2 2
The notation follows that of Reiter [2] with brackets representing
an average over the subscripted variable and parentheses representing
a deviation from the average. The summation is over the eight layers
in the vertical. The variable Tj represents the mean layer temperature
in the i layer derived from the thickness, X is longitude, 4> is latitude,
u. and v. are the usual sealer horizontal wind speeds, Ap. is the pressure
difference from the bottom to the top of the i layer and [a] is the
hemispheric averaged static stability given by
[ 00 i f — -k
•5^ (5)1000"R p X ,< j> •
where 0 is the potential temperature, g is the acceleration of gravity
and R is the universal gas constant. The u. and v. in equations 3 and 4
are claculated using the geostrophic assumption. In this paper contribu-
tions to the total energy from individual layers will be noted by, for
example, AE (300-500 mb), the contribution to the total AE from the layer
300-500 mb.
In the figures to be presented,three-day running means are used to
smooth out small time scale fluctuations. In addition to the smoothing
of the three-day running means, seven days are eliminated from the SIRS
representation because of insufficient hemispheric data coverage. The
elimination is based on the number of locations in the five-by-five
latitude-longitude grid that are originally filled with satellite data.
The days eliminated are January 1, 5, 13, 21, 26, 28, 31.
Figure 1 shows the AZ (300-500 mb) computed from both the NMC fields
and from the fields derived from the SIRS radiances. The AZ (300-500 mb)
based on the SIRS data is consistently less than the NMC-based results.
Ti7ie underestimation is about 20%. Since AZ involves squares of terms
involving meridional temperature gradients, the underestimation of AZ
by 20% implies an underestimation of meridional temperature gradients by
about 10%. The underestimation appears to be larger in the middle of the
month. The dates of relative maxima and minima are, however, well
defined. The times of the month when there is a significant increase or
decrease of AZ are indicated correctly.
ijigure 2 indicates the variation of KE (300 mb) during the month as
calculated from NMC 300 mb height field and the 300 mb height field obtained
from SIRS-derived thicknesses added to the NMC 1000 mb height field. The
KE (300 mb) actually represents the contribution to the total KE from the
layer 250-400 mb. The SIRS KE underestimates the actual by about 50%.
However, positions of relative maxima and minima are again indicated.
Starting from a minimum at the beginning of the month, there is a sharp
increase from about the 5th to a peak on the 9th, indicated in both curves.
After a decrease to the 12th, the two curves do not parallel each other
well until the sharp rise from the 17th to the peak around the 20th and
21st. From this peak to the end of the month, there is a sharp decrease
to the low for the month in both curves.
Figure 3 gives the two curves for AE (100-200 mb). This layer is,
for the most part., in the lowest part of the stratosphere. The under-
estimation is present again, with the SIRS AE being about 55% of the NMC
values on the average. Again, however, the maxima, minima and trends
are well indicated by the SIRS-based AE. The sharp increase from the 5th
to the 10th is indicated well, as is the increase from the middle of the
month to the maximum for the month on the 22nd. From this peak to the
end of the month, there is a sharp decrease in both curves.
Figures 1 through 3 are representative examples of general circula-
tion calculations in the upper troposphere and stratosphere. The calcula-
tions indicate that although magnitudes are systematically underestimated,
especially in the eddy terms, the calculations based on SIRS-derived
atmospheric structure correctly identify times of maxima, minima and major
changes in components of the atmosphere's energy cycle.
4. Energy Changes during a Stratospheric Breakdown
Figure 4 shows three day running means of mid-stratosphere energy
parameters during a polar vortex breakdown. The parameters have been
calculated solely from thermal structure obtained from SIRS radiances,
with the exception of the use of daily 1000 mb height fields. The AZ
and AE in Figure 4 are the contributions to the total values from the
layer 10-30 mb. The KZ and KG in the diagram are based on the 10 mb
height fields and represent the layer 0-20 mb. The dashed portions of
the curves indicated dates when the data is such that the indicated
computations are unreliable, or days when there are missing data.
The breakdown begins about December 22. Prior to that there is a
significant increase in KZ (10 mb) and KE (10 mb) from the 15th to the
19th. From the 22nd to the 28th, there is a sharp increase in AE, a
sharp decrease in KZ, and a decrease in AZ. The decrease in AZ is small
in magnitude but large in percentage change. The KE reaches a peak on
the 27th. The AE remains high until about January 1, decreases sharply
from the 1st to the 5th, and remains nearly constant for the remainder
of the period. While the AE decreases, the AZ increases to a peak on
the 3rd and 4th and then decreases again. After reaching its peak on
the 27th, the KE decreases unsteadily.
One interesting observation from Figure 4 is that the sum of the
four energies decreases from before to after the stratospheric breakdown.
Because it is unlikely that generation or dissipation terms could account
for this decrease, the decrease implies an export of energy out of this
mid-stratospheric layer during the breakdown.
The breakdown in Figure 4 has been studied by Miller, Brown and
Campana [1] using mainly NMC and rocketsonde data. The energy changes
8in Figure 4 agree at least qualitatively with their calculations.
Quantitatively,it is difficult to compare the computations since different
layers and different geographic areas are used in the computations.
5. Conclusions
The examples shown in this paper indicate that, within the
limitations discussed, worthwhile general circulation calculations
can be made with atmospheric structure derived from satellite,
multi-channel radiance data.
(M
ju
12 -
1 I
10
8
NMC
8 10 12 14 16 18
JANUARY 1970
20 22 24 26 28 30
Fig. 1. Variation with time of the contribution to the zonal available
potential energy from the 300-500 mb layer, AZ [300-500 mb].
3.8
3.6
3.4
3.2
3.0
w 2.8
,^
| 2.6
o
"o 2.4
^
1.8
1.6
1.4
1.2
1.0 J I
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
JANUARY 1970
Fig. 2. Variation with time of the eddy kinetic energy at 300 mb, KE. [300 mb].
CM
,80 -
.70
.60
.50
in
2
 .40
.30
.20
NMC
4 6 10 12 14 16 18 20 22 24 26 28 30
JANUARY 1970
Fig. 3. Variation with time of the comtribution to the eddy available poten-
tial energy from the 100-200 mb layer, AE [100-200 mb].
o
IO
40
36
32
28
24
20
16
12
8
4
0
KE
16 18 20 22 24 26
DECEMBER 1969
28 30 I 5 7 9 II
JANUARY 1970
13 15
Fig. 4. ' Energy changes during a stratospheric breakdown. AZ and AE for the
10-30 mb layer, KZ and KE at 10 mb.
References
1. Miller, A. J., J. A. Brown and K. A. Campana: A Study of the
Energetics of an Upper Stratospheric Warming (1969-1970). Quart.
J. Roy. Meteor. Soc., 9_8, 730-744 (1972).
2. Reiter, E. R.: Atmospheric Transport Processes, Part I: Energy
Transfers and Transformations. AEC Critical Review Series, USAEC
Report TID-24868. Oak Ridge, Tennessee: USAEC Division of Technical
Information Extension, 1971.
3. Smith, W. L., H. M. Woolf and W. J. Jacob: A Regression Method for
Obtaining Real-Time Temperature and Geopotential Height Profiles
from Satellite Spectrometer Measurements and Its Application to
Nimbus 3 SIRS Observations. Monthly Weather Review, 98, 582-603
(1970).


Interhemispheric comparison of atmospheric circulation features as evaluated from Nimbus satellite data

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