ARTICLE IN PRESS
Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
www.elsevier.com/locate/jastp
The dynamical influence of the Pinatubo eruption in the
subtropical stratosphere
J. Hampsona, C. Claudb, P. Keckhuta,, A. Hauchecornea
a
Service d’Aéronomie, Institut Pierre Simon Laplace, UMR 7620, Verrières-le-Buisson, F-91371, France
Laboratoire de Météorologie Dynamique, Institut Pierre Simon Laplace, UMR 8359, Ecole Polytechnique, Palaiseau, F-91128, France
b
Received 2 January 2006; received in revised form 21 April 2006; accepted 5 May 2006
Available online 24 July 2006
Abstract
An analysis of de-seasonalised TOVS satellite data shows an aspect of the effect of the Mount Pinatubo eruption (15th
June 1991, 15.141N, 120.351E) which has not previously been commented on. A mean tropical temperature increase of
around 3–4 K is seen in the 50–30 hPa layer from August 91 to October 91, as seen by previous authors. However, distinct
bands of temperature increase are then seen in the subtropics from November 91 until May 92. It is hypothesised that this
subtropical signal is a dynamical consequence of the radiative heating increase in the lower tropical stratosphere
immediately after the eruption. The hypothesis is tested in a 3D mechanistic middle atmosphere model, with the tropical
Pinatubo chemical–radiative aerosol effect on temperature parameterised using a simple direct temperature forcing. It is
suggested that the subtropical temperature pattern observed is a result of a tropical–subtropical circulation cell caused by
the Pinatubo temperature effect in the tropics.
r 2006 Elsevier Ltd. All rights reserved.
Keywords: Atmospheric dynamics; Temperature; Volcanic aerosols; Modeling
1. Introduction
Understanding the effect of volcanic eruptions on
the atmosphere is important for both the short-term
and long-term understanding of climate. It has been
known for centuries that a large volcanic eruption
can have significant consequences in the years
succeeding the eruption, in particular in cooling
the earth’s surface (e.g. Franklin, 1784).
The way in which a volcanic eruption affects the
climate depends on its location, strength, altitude
and timing. If the volcanic plume from the eruption
Corresponding author. Fax: +33 1 69 20 29 99.
E-mail address: [email protected] (P. Keckhut).
1364-6826/$ - see front matter r 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jastp.2006.05.009
does not penetrate into the stratosphere, then its
effects are likely to be regional. However, if the
plume does penetrate into the stratosphere, its
effects are likely to be more global. This is due to
the longer lifetime of sulphate aerosols in the
stratosphere and the effect of the stratospheric
circulation. Sulphur gases from the eruption are
converted into sulphate aerosols in the stratosphere,
which then have an e-folding residence time of
about 1 year. Antuña et al. (2003) carried out a
comparison of volcanic aerosol measurements from
five lidar stations and the stratosphere aerosol and
gas experiment (SAGE) II and found a good
agreement. Sulphate aerosols have a direct effect
on the atmosphere’s chemistry and radiation, and
ARTICLE IN PRESS
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
also indirect effects due to dynamical processes.
These effects are described in more details in the
review by Robock (2000).
The eruption of Mount Pinatubo in June 1991
was the strongest eruption of the 20th century, and
the best ever documented by so many observations.
Enormous amounts of SO2 and other volcanic
effluents created stratospheric clouds to altitudes
higher than 30 km.In particular, these could be
observed and tracked by satellite instruments, as
well as their influence on atmospheric temperatures.
Numerous observational and modelling studies
have been carried out on the Pinatubo eruption.
Different studies have focused on different aspects
of the effect of the eruption.
For observational data, Labitzke and McCormick (1992) compared northern hemisphere (NH)
stratospheric rawinsonde-derived temperature data
at 30 and 50 hPa with long-term monthly means,
showing significant temperature increases between
301N and the equator, of up to 3 K at 201N and
higher equatorwards. This temperature increase is
mainly due to the direct radiative forcing. Angell
(1993) compared the changes in temperature following the eruptions of three different eruptions:
Mount Agung, El Chichòn and Mount Pinatubo.
The warming for Pinatubo was comparable to
Agung and El Chichon in the tropics and north
extratropics, but was the largest in southern midlatitudes and the polar regions. It was speculated
that this could be due to the eruption of Cerro
Hudson (Chile), which occurred shortly after the
Pinatubo eruption. Lidar observations conducted
above the south of France (Keckhut et al., 1995)
revealed a temperature response in the mesosphere
associated with the Mount Pinatubo eruption.
Simulations (Rind et al., 1992) showed similar
responses for major eruptions due to indirect effects
through the propagation of the planetary waves that
could have changed due to the modification of the
vertical static stability in the tropics.
Chandra (1993) looked at the total column ozone
from Nimbus 7 TOMS and NOAA-11 SBUV/2
spectrometers, finding a decrease of 5–6% in the
tropics, 3–4% at mid-latitudes and 6–9% at high
latitudes in the NH. Some of the decrease at highlatitudes was thought to be due to the effects of the
QBO phase and inter-annual variability. Randel
et al. (1995) examined observations of ozone (from
TOMS satellite instrument) and temperature (MSU
instrument). They showed substantial decreases in
column ozone over large regions of the globe, and
1601
anomalously warm temperatures over 301N–S for
1–2 years following the eruption. Cold anomalies
were observed over the NH polar cap for NH
summer 1993. This was thought to be linked to an
additional contribution due to the decrease in ozone
levels. For modelling work, Ramachandran et al.
(2000) used the SKYHI GCM to model the stratospheric temperature response to the Mount Pinatubo eruption. They found an increase in temperature
in the tropical lower stratosphere of 3 K. They
stated that the lower latitude response compared
well to observations for only the first year following
Pinatubo; however, they found a good comparison
with the global mean temperature evolution for the
two years following Pinatubo. This was thought to
be because the global mean response is not sensitive
to dynamical adjustments, which would not necessarily be represented properly in a model.
Pitari and Mancini (2002) used a coupled climatechemistry model to study the dynamical effects of
the radiative forcing due to stratospheric aerosols
formed after the Pinatubo eruption. They saw a
two-fold dynamical perturbation: of the stratospheric mean meridional circulation, and of planetary wave propagation in mid-high latitudes. Yang
and Schlesinger (2002) carried out ensemble simulations using a GCM, in particular looking at the role
of using observed sea-surface temperatures (SSTs).
They found that the influence of Pinatubo was
sensitive to the prescribed SST anomalies, but that
the stratosphere was insensitive. They also found
that the simulated global-mean temperature
anomaly due to Pinatubo exceeded that of observations by 1 to 1.5 K, and suggested that this was in
part due to the model not resolving the QBO and
observed ozone depletion. Rosanov et al. (2002)
investigated the effect of the Pinatubo eruption on
ozone and temperature using the UIUC (University
of Illinois) GCM with interactive photochemistry.
The model tropical stratospheric warming exceeded
that of observations by 1–2 K, but matched well the
intensification of the polar night jet in NH winter
1991–1992, the cooling of the lower stratosphere
and the warming of surface area in boreal winter in
large parts of the NH.
Stenchikov et al. (2004) reported on a SKYHI
GCM investigation of radiative and dynamical
mechanisms that could account for observed arctic
oscillation (AO) perturbations in the NH extratropical winter tropospheric circulation. They also show a
QBO temperature effect in the subtropics, associated
to the QBO residual circulation, of up to 1 K. The
ARTICLE IN PRESS
1602
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
Mount Pinatubo eruption is extensively studied and
described, and is shown to have a strong impact on
the whole atmosphere during several months after
the eruption through different effects including
numerous indirect feedbacks.
In this paper, we investigate an additional
possible dynamic effect of the Mount Pinatubo
eruption on tropical/subtropical stratospheric temperatures which has not been previously examined.
In Section 2, an analysis of deseasonalised TIROSN operational vertical sounder (TOVS) satellite
data is presented, showing a distinct band of
subtropical temperature increase in the lower
stratosphere (50–30 hPa) in months following the
eruption. In Section 3 it is hypothesised that this
subtropical signal is a dynamical consequence of the
tropical lower stratospheric temperature increase
immediately following the eruption. The hypothesis
is tested in a 3D mechanistic middle atmosphere
model, with the tropical Pinatubo chemical-radiative aerosol effect on temperature parameterised
using a simple direct temperature forcing. The
model and the forcing of the Pinatubo tropical
forcing are described in Section 3. The model results
are discussed in Section 4. In Section 5, the model
results are compared to the TOVS data analysis,
and a discussion follows.
2. Satellite observations of the effect of Pinatubo
The TOVS, which flies aboard NOAA polar
satellites, consists of three passive vertical sounding
instruments (Smith et al., 1979): the high resolution
infrared radiation sounder (HIRS-2), a radiometer
with 19 channels in the infrared band and one in the
visible band; the microwave sounding unit (MSU), a
microwave sounder with four channels in the
vicinity of 55 GHz; and the stratospheric sounding
unit (SSU), a pressure-modulated infrared radiometer with three channels near 15 mm. Only HIRS-2
and MSU data have been processed by the
improved initialisation inversion (3I, e.g. Chédin
et al., 1995, Scott et al., 1999) for producing
atmospheric parameters. Retrievals are from
NOAA-10 for the period January 1987–August
1991 and NOAA-12 for the period September
1991–August 1995. In the 3I procedure, adjustment
coefficients are calculated to take into account the
possible changes in instruments over their lifetime,
therefore ensuring a spatial and temporal homogeneity. Their determination, based on time and
space collocations between TOVS measurements
and radiosonde reports makes use of a moving
average on a basis of 3 months (Scott et al., 1999).
Previous studies dedicated to the stratosphere, have
shown that, between 100 and 10 hPa, it is reasonable
to consider four different layers, and the validation
tests conducted for very different situations (stratospheric coolings, warmings; and more standard
situations) give confidence into the 3I-retrieved
temperatures (Claud et al., 1993, 1996, 1998).
Further validation studies have been performed
and are described in Claud et al. (1999); Cagnazzo
et al. (2000) and Cagnazzo (2004). They all
demonstrate the overall continuity of the satellite
products, since no ‘‘break’’ appears between the
NOAA-10 and NOAA-12 periods. Finally, mean
temperatures for the following layers: 100-70, 70-50,
50-30, and 30–10 hPa at a spatial resolution of
11 latitude by 11 longitude are available for each
month, a.m. and p.m. separately. In this study, only
a.m. monthly mean values are used and discussed,
avoiding problems related to different equator
crossing times.
For assessing the impact of the Pinatubo eruption
on stratospheric temperatures, the climatological
mean seasonal cycle has been removed from the
record of individual months. Here, the climatological mean is calculated using the data from January
1987 to May 1991 and July 1993 to June 1995
(hence not including the two years immediately
following the Pinatubo eruption). We concentrate
on the layer 50–30 hPa (from about 20–25 km),
which corresponds to the layer where the effect on
the subtropical temperatures has been found to be
maximum.
The effect on the mean temperature appears
clearly in August 1991 (Fig. 1a) with a rather
homogeneous anomaly of the order of 3 K over the
tropics. There is a strong latitudinal temperature
gradient in the subtropics in both hemispheres. Until
October, the situation remains globally unchanged,
except that the anomaly is larger than 4 K over some
areas and that the gradient in the NH tends to slack.
In contrast, in November, the anomaly patterns are
totally different, with two bands of large values
(about 3 K) both sides of the Equator, while
equatorwards, the anomaly ranges now between 1
and 2 K (Fig. 1b). From December 1991 on, the
subtropical signal is stronger (larger and more zonal)
in the southern hemisphere than in the northern
hemisphere (see Fig. 1c, valid for March 2002) and in
May 1992 (Fig. 1d), the signal appears much weaker,
compared to the period before.
ARTICLE IN PRESS
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
Fig. 1. TOVS temperature anomaly (months following Pinatubo
minus climatological mean), in K, in the layer 20–25 km for: (a)
August 91; (b) November 91; (c) March 92; (d) May 92 (see text
for further details).
A similar effect in the subtropics is seen in NCEP
re-analysis data as shown in Ramachandran et al.
(2000) for the 50 hPa level (their Fig. 7b). However,
these authors do not comment on this point. A
distinct subtropical signal can also be seen in MSU
temperature anomalies for the period 1991–1994
(Fig. 13a of Randel et al., 1995), though again the
authors do not comment on this specifically.
3. Hypothesis, description of model and forcing of
tropical volcanic temperature signal, and description
of simulations performed
We hypothesise here that the subtropical bands of
higher temperature seen between November 1991
and May 1992 in the TOVS data could be an
indirect dynamical effect of the Pinatubo eruption,
resulting from an anomalous circulation cell caused
by the direct tropical radiative heating effect of
Pinatubo.
This hypothesis is tested in using a 3-D mechanistic model. A model simulation is carried out with a
1603
parameterised radiative effect of the Pinatubo
eruption using a direct temperature forcing on the
tropical lower stratosphere. It would be difficult to
produce a Pinatubo temperature signal using a more
realistic chemical–radiative approach, as this would
be beyond the scope of the model chemistry and
radiative schemes. Therefore a simplified approach
is taken: a direct temperature forcing is applied in
the model lower stratosphere, based upon the
temperature enhancement observed and reported
(Labitzke and McCormick, 1992) and stratospheric
aerosol distribution and evolution (Sato et al.,
1993). Such a simplified approach is justified
because we are here testing the hypothesis that the
radiative heating inducing the tropical temperature
anomaly is the primary cause of the subtropical
signal seen in the TOVS data. The results of the
simulation with the parameterised Pinatubo tropical
temperature forcing are compared to a control
simulation in which there is no such temperature
forcing.
The model used in this work is MSDOL
(Berenger, 1999): it was developed from the NCAR
ROSE model. It is a mechanistic stratosphere–
mesosphere dynamical–chemistry model, with dynamics from the primitive equations. The height
range of the model is from 10 to 80 km. The model
has a regular horizontal grid with 32 longitudinal
points and 36 latitudinal points. There are 24
vertical pressure levels. Lower boundary dynamical
forcing values are provided by NCEP re-analysis
data (Kalnay et al., 1996). The Fritts and Lu scheme
(1987) is used to parameterise gravity wave drag.
The detailed chemical reactions include photolysis,
gas phase photochemical reactions, CFC polar
chemistry and advection of long-lived species using
a Van Leer Eulerian scheme. Short-wave radiation
is a parameterisation of O2, O3 solar heating
(Strobel et al.,1978; Zhu et al., 1994), and LW
radiation a parameterisation of CO2 cooling (Fels
and Schwarzkopf, 1981; Schwarzkopf and Fels,
1985).
Ideally, a quasi-biennial oscillation (QBO) would
be present in the model throughout the whole
period of the model simulation, as it is known that
the phase of the QBO has a dynamical influence on
the stratosphere and could also directly impacted on
the atmospheric response of a volcanic eruption
(e.g. Stenchikov et al., 2004). Such investigations are
difficult to perform with a prescribed QBO (as done
by Stenchikov et al.) because the wind observations
may contain an indirect volcanic signal (if we expect
ARTICLE IN PRESS
1604
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
a dynamical response to the Pinatubo eruption). In
our experiment this is also difficult to perform as
any forcing of the tropical wind and/or temperature
in the lower stratosphere will also impinge on the
volcanic temperature signal forcing (described
below). Therefore, our model does not include any
QBO forcing during the course of the model
simulation with volcanic forcing. Instead, the model
is initialised with the appropriate QBO winds and
temperature anomaly. This is done by spinning up
(using a relaxation scheme) from NCEP re-analysis
data in the tropics up to 31 km. The amplitude of
the tropical zonal wind in the NCEP data has been
scaled up by a factor of 1.5, since the nature of the
re-analysis data means that the amplitude of the
QBO in the NCEP data is slightly smaller than one
expects (Baldwin, 1999).
The model lower boundary dynamical values
are forced using NCEP re-analysis data. As well,
the NCEP data is also forced (using a simple
relaxation scheme) over the lowest few model
levels (up to 16.5 km), in order to avoid the
possibility of the forced planetary scale waves being
unrealistically damped out over the lowest few
model levels.
The lower stratosphere temperature effect of the
Pinatubo eruption is simulated as follows. A direct
forcing term F (heating rate) is added to the right
hand side of the temperature prognostic equation.
The latitudinal, height and time dependence of F is
based upon aerosol data taken from Sato et al.
(1993) (and also corresponds approximately to that
described by Antuña et al., 2003) and takes the
form:
and
8
0
>
>
>
>
>
< sin2 p ðz 18Þ
10
hðzÞ ¼
>
2
>
> cos
>
>
:
0
for zo18 km;
18pzo23 km;
23pzo28 km;
zX28 km:
The forcing amplitude A is chosen so as to give a
maximum volcanic temperature effect of about 2 K.
Trial and error leads to taking a value of
A ¼ 2:53 105 K=s.
The time, height and latitudinal dependence of F are
shown in Fig. 2. The choice of the value of 2 K is an
averaged value taken from Labitzke and McCormick (1992). Although this does not correspond
exactly to the mean value seen in the tropics in the
TOVS data in Section 2, it should be remembered
(a)
F ¼ A f ðtÞ gðfÞ hðzÞ.
The latitudinal, height and time functions
are given by the following normalized analytical
terms:
8
0
for toJune 1991
>
>
>
<
1
tXJune 1991 and toDecember 1991
f ðtÞ ¼
t
>
>
>
tXDecember 1991
: exp 365
with t* the time in days after stratospheric
aerosol content had started to decrease (December
1991),
and
p j
(
cos
for 20 ojo20
40
gðjÞ ¼
0
otherwise
(b)
Fig. 2. Distributions used for model temperature forcing to
simulate lower stratospheric tropical effect of Pinatubo: (a)
latitude-height dependence g(f).h(z); (b) time dependence f(t).
NB: The months on the time axis indicate the first day of the
corresponding month. The functions are unitless.
ARTICLE IN PRESS
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
that the temperature forcing distribution has been
based on SAGE aerosol data, and not the temperature data. This gives a more homogenous and
broader forcing than it would otherwise be. Further,
the aim of the simulation here is to look at a
possible mechanism for a subtropical response to
the tropical forcing, which should be robust to the
details of the tropical forcing. Although Antuña
et al. (2003) discuss some inhomogeneities in the
tropical aerosol from Pinatubo from June 1991 to
January 1992 , this is not thought to be important
for this study and we have kept the experiment
simple by using homogeneous forcing in the tropics.
Similarly, Antuña et al. (2002) discuss some descent
of the aerosol height around the start of 1992, but
this has not been included in the model forcing.
1605
(a)
(b)
4. Model results
The difference in temperature between the model
simulation with volcanic forcing and the control
simulation is shown, at four different model logpressure height levels: 16, 22, 28 and 34 km (Fig. 3).
At 16 km, the temperature response to the volcanic
forcing is negligible everywhere compared to that
which occurs higher up in the stratosphere.
For that which is of interest here, the main
temperature response to the volcanic forcing occurs
between 22 and 28 km.At 22 km, there is a distinct
tropical band of warming. For the eight months
following the Pinatubo eruption, until February
1992, this is about 2 K at the equator, and stretches
from about 20–301N to 20–301S. Polewards of this,
the response is generally much weaker. Around
February 1992, there is a change in the tropical
response: it becomes somewhat weaker (about 1.4 K
at the equator), and is confined to slightly lower
latitudes, between about 15–251N to 15–251S. In the
extratropics, there are two occurrences of stronger
response. In SH winter/spring (July–October 1991),
there is a negative response of up to 0.5 K (although
this is possibly too soon to be attributed to the
volcanic forcing) followed by a positive response;
then in NH winter/spring (January–March 1992)
there is a negative response of up to 2.5 K followed
by a positive response of up to 2.5 K.
At 28 km, the response is significantly different.
Most notably, the signal is stronger in the subtropics than in the tropics. In the tropics, there is
notable seasonal variation, with maximum response
of 0.8 K in January 1992. In the subtropics,
around 301N and 301S, there is also seasonal
(c)
(d)
Fig. 3. Model temperature anomaly (i.e. model simulation with
volcanic forcing minus control simulation) in K, at: (a) 16 km; (b)
22 km; (c) 28 km; (d) 34 km.
variation, generally varying between 0.5 and 1.5 K,
but the signal is always stronger than that in the
tropics. It is strongest around August 1991 (SH) and
January–February 1992 (NH), and is notably
weaker in both the north and the south around
March 1992. Then, from June until October, the
signal is again stronger in the subtropics than in the
tropics, and larger at around 301S than at 301N. As
at 22 km, there are occurrences of stronger extratropical response, in SH winter/spring and NH
winter/spring. Of these, the warming in NH winter/
spring is largest: there is a cooling of up to 3 K
followed by a warming of up to 5. There is also a
cooling in SH winter 1992 of up to 0.5 K.
At 34 km, the general temperature response is
much weaker and more uneven. It is generally
positive, of up to 0.4 K, with some smaller patches
of negative response. The subtropical temperature is
generally slightly cooler than that in the tropics,
opposite to what was seen at 28 km.There are again
ARTICLE IN PRESS
1606
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
slightly stronger responses in SH winter/spring 1991
and 1992, with cooling and then warming, and a
stronger response in NH winter/spring, with a
cooling of up to 0.8 K in January 1992 followed
by a warming of up to 3.9 K.
Since it has been hypothesised that the occurrence
of the subtropical bands of higher temperature
between November 1991 and May 1992 is due to a
tropical-subtropical circulation cell, we next examine
the vertical upwelling in the model. The difference in
upwelling between the model simulation with volcanic
forcing and the control simulation, for December
1991, is shown in Fig. 4. In the tropics, there is
stronger upwelling for the simulation with volcanic
forcing in both the stratosphere (maximun at
20–25 km) and the mesosphere (maximum at
50-60 km), of up to 0.1 mm/s. This increased upwelling
is generally from about 151N to 151S. In the lower
stratospheric tropics and mid-latitudes the difference
in upwelling represents a significant proportional
change of up to 40% from the control simulation. in.
Associated to this upwelling there is downwelling
around 201 in both hemispheres in the stratosphere
and around 30–401 in the mesosphere. This circulation cell in the stratosphere is induced by the direct
warming and is responsible for the warming bands
centred respectively around 251S and 251N located
around 28 km.
A larger cell is also generated with the associated
downwelling at 60 km. This is probably associated
with the modification of the planetary wave
propagation due to the change of the static stability
(Rind et al., 1992) and warms the upper mesosphere
(Keckhut et al., 1995).
Fig. 4. Latitude–height distribution of model vertical velocity
anomaly (i.e. model simulation with volcanic forcing minus
control simulation), in ms1, for December 1991.
5. Discussion and conclusions
In the analysis of the TOVS data described in
Section 2, we saw a warming associated with the
Pinatubo eruption which showed distinct bands of
subtropical temperature increase from November
1991 to May 1992 in the 50-30 hPa layer. This
contrasts with the earlier signal of a more homogenous tropical temperature increase (centred on
the equator), which is what is expected for radiative
forcing alone. Such a feature is also depicted in
NCEP reanalyses and raw satellite data. It was
hypothesised that the subtropical signal could be a
purely dynamical response to the tropical volcanic
forcing. This possibility was tested by carrying out a
model experiment, using a parameterised volcanic
temperature forcing, in the tropics. A direct
temperature forcing was applied in the model lower
stratosphere, based upon the observed temperature
enhancement and stratospheric aerosol distribution
and evolution. The results of the simulation with the
parameterised Pinatubo tropical temperature forcing were then compared to a control simulation in
which there is no such temperature forcing.
The model did indeed produce a subtropical
response to the Pinatubo forcing. In the layer
centred at about 28 km, temperature anomalies are
larger in the subtropics compared to the tropics. In
order to understand the cause for this subtropical
warming, vertical velocity produced by the model
was also examined. The vertical velocity anomaly in
the simulation with the volcanic forcing compared
to the control simulation with no volcanic forcing
(Fig. 4) suggests that the tropical forcing in the
model does produce a meridional circulation cell
with the ascending branch in the tropics and the
descending branch inducing a diabatic heating in
the subtropics/mid-latitudes. A latitude height plot
of the temperature anomaly in December 1991 due
to the volcanic forcing gives a good indication of
how this circulation cell produces a subtropical
temperature anomaly higher than that in the tropics
(Fig. 5).
When quantitatively comparing the TOVS temperature to the simulated temperatures, there are
differences, in particular in terms of amplitude and
height of the subtropical anomalies. However,
simulated results need to be considered carefully
because the crude modelisation of the forcing can
only provide qualitative results. With this in mind,
the model simulation shows certain similarities with
the analysis of the TOVS data.
ARTICLE IN PRESS
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
1607
References
Fig. 5. Latitude–height distribution of model temperature
anomaly (i.e. model simulation with volcanic forcing minus
control simulation), in K, for December 1991.
While high latitudes are not within the main
focus of this study, we found some similarities
between the model simulations and previous
works. Some large changes have been observed
in both observations and simulations. In the
model lower stratosphere, cooling is seen in
January to February 1992, followed by warming
in March–May 1992. Rosanov et al. (2002)
discuss an intensification of the polar night
jet in December 1991. In the model simulations
carried out by Ramachandran et al. (2002),
they saw cooling in December 1991 followed
by some warming in the extratropics in January
1991, followed by further cooling. Their analysis of
NCEP data showed cooling in December 1991,
warming in January 1992, cooling in March
1992 (but not as far as the pole), then warming in
April 1992.
Acknowledgements
This work was supported by a contract from the
European Commission (within the EuroSPICE
project). TOVS retrievals have been obtained from
the Atmospheric Radiation Analysis group at
LMD, through the NOAA/NASA TOVS Pathfinder (Path-B) program. We would like to thank
Chiara Cagnazzo for valuable discussions. The
NCEP re-analysis data used in the model forcing
was provided by CLIMSERV, Ecole Polytechnique,
Paris, France and the NOAA-CIRES Climate
Diagnostics Center, Boulder, Colorado, USA (web
site at http://www.cdc.noaa.gov/).
Angell, J.K., 1993. Comparison of stratospheric warming
following Agung, El Chichon and Pinatubo volcanic eruptions. Geophysical Research Letters 20, 715–718.
Antuña, J.C., Robock, A., Stenchikov, G.L., Thomason, L.,
Barnes, J., Thomason, L., 2002. Lidar validation of SAGE II
aerosol measurements after the 1991 mount Pinatubo eruption. Journal of Geophysical Research 107 (D14), 4194.
Antuña, J.C., Robock, A., Stenchikov, G.L., Zhou, J., David, C.,
Barnes, J., Thomason, L., 2003. Spatial and temporal
variability of the stratospheric aerosol cloud produced by
the 1991 Mount Pinatubo eruption, Journal of Geophysical
Research 108 (D20), 4624 doi:10.1029/2003JD003722.2003
Baldwin, M.P., Personal communication, 1999.
Bérenger, G., MSDL System. User’s Manual, 1999.
Cagnazzo, C., 2004. Analyse des facteurs de variabilité de la
température dans la stratosphère, Thèse de Doctorat de
l’Ecole Polytechnique, 195p. (available from Laboratoire de
Météorologie Dynamique, Ecole Polytechnique, 91128,
Palaiseau Cedex).
Cagnazzo C., Claud C., Hauchecorne A., Keckhut P, Chedin A.,
Seasonal and interannual variability of stratospheric temperatures based on TOVS satellite data : 1987-1995. Proceedings of the 2nd SPARC General Assembly, Mar del Plata,
Argentina, Nov. 6-10, 2000.
Chedin, A., Scott, N.A., Wahiche, C., Moulinier, P., 1985. The
Improved Initialization Inversion method: a high resolution
physical method for temperature retrievals from satellites of
the TIROS- N series. Journal of Climate and Applied
Meteorology 24, 128–143.
Chandra, S., 1993. Changes in stratospheric ozone and temperature due to the eruptions of Mt. Pinatubo. Geophysical
Research Letters 20, 33–36.
Claud, C., Ovarlez, J., Chedin, A., Scott, N.A., 1993. TOVS
observations of a stratospheric cooling during the CHEOPS3
campaign: February 4-6, 1990 over Scandinavia. Journal of
Geophysical Research 98, 7229–7243.
Claud, C., Ovarlez, J., Scott, N.A., 1996. Assessment of TOVSderived stratospheric temperatures up to 10 hPa for episodes
of the EASOE campaign. Journal of Geophysical Research
101, 3941–3956.
Claud, C., Ovarlez, J., Scott, J., 1998. Evaluation of TOVSderived stratospheric temperatures up to 10 hPa for a case of
vortex displacement over western Europe. Journal of Geophysical Research 103, 13743–13761.
Claud, C., Scott, N.A., Chedin, A., 1999. Seasonal, interannual
and zonal temperature variability of the tropical stratosphere
based on TOVS satellite data: 1987–1991. Journal of Climate
12, 540–550.
Fels, S.B., Schwarzkopf, M.D., 1981. An efficient, accurate
algorithm for calculating CO2 15 mm band cooling rate.
Journal of Geophysical Research 86, 1205–1232.
Franklin, B., 1784. Meteorological imaginations and conjectures.
Manchester Literary and Philosophical Society Memoirs
and Proceedings 2, 122 (reprinted in Weatherwise, 35,
262.1982).
Fritts, D., Lu, W., 1987. Spectral estimates of gravity wave
energy and momentum fluxes. Part II : parameterization of
wave forcing and variability. Journal of Atmospheric Science
50, 3695–3713.
ARTICLE IN PRESS
1608
J. Hampson et al. / Journal of Atmospheric and Solar-Terrestrial Physics 68 (2006) 1600–1608
Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D.,
Gandin, L., Iredell, M., Saha, S., White, C., Woollen, J., Zhu,
Y., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J.,
Mo, K.C., Ropelewski, C., Wang, J., Leetmaa, A., Reynolds,
R., Jenne, P., Joseph, D., 1996. The NCEP/NAR 40-year
reanalysis project. Bulletin of the American Meterological
Society 77 (3), 437–471.
Keckhut, P., Hauchecorne, A., Chanin, M.L., 1995. Mid-latitude
long-term variability of the middle atmosphere: trends, cyclic
and episodic changes. Journal of Geophysical Research 100,
18887–18897.
Labitzke, K., McCormick, M.P., 1992. Stratospheric temperature
increases due to Pinatubo aerosols. Geophysical Research
Letters 19, 207–210.
Pitari, G., Mancini, E., 2002. Short-term climatic impact of the
1991 volcanic eruption of Mt. Pinatubo and effects on
atmospheric. Natural Hazards and Earth System Sciences 2,
91–108.
Ramachandran, S., Ramaswamy, V., Stenchikov, G.L., Robock,
A., 2000. Radiative impact of the Mount Pinatubo eruption:
lower stratospheric response. Journal of Geophysical Research 105, 24409–24429.
Randel, W.J., Wu, F., Russell III, J.M., Waters, J.W.,
Froidevaux, L., 1995. Ozone and temperature changes in
the stratosphere following the eruption of Mount Pinatubo.
Journal of Geophysical Research 100, 16753–16764.
Rind, D., Suozzo, R., Balachandra, N.K., Prather, M.J., 1992.
Climate change and the middle atmosphere. Part II: The
impact of volcanic aerosols. Journal of Climate 5, 189–207.
Robock, A., 2000. Volcanic eruptions and climate. Reviews of
Geophysics 38, 191–219.
Rosanov, E.V., Schlesinger, M.E., Andronova, N.G., Yang, F.,
Malyshev, S.L., Zubov, V.A., Ergorova, T.A., Li, B., 2002.
Climate chemistry effects of the Pinatubo volcanic eruption
simulated by the UIUC stratosphere/troposphere GCM with
interactive photochemistry. Journal of Geophysical Research
107 (D4), 4594.
Sato, M., Hansen, J.E., McCormick, M.P., Pollack, J.B., 1993.
Stratospheric aerosols optical depths, 1850–1990. Journal of
Geophysical Research 98, 22.987-22.994.
Schwarzkopf, M.D., Fels, S.B., 1985. Improvements to the
algorithm for computing CO2 transmission and cooling rates.
Journal of Geophysical Research 90, 10541–10550.
Scott, N.A., Chedin, A., Armante, R., Francis, J., Stubenrauch,
C., Chaboureau, J.P., Chevallier, F., Claud, C., Cheruy, F.,
1999. Characteristics of the TOVS Pathfinder Path-B Dataset.
Bulletin of the American Meteorological Society 80 (12),
2679–2701.
Smith, W.L., Woolf, H.M., Hayden, C.M., Wark, D.Q.,
McMillin, L.M., 1979. The TIROS-N Operational Vertical
Sounder. Bulletin of the American Meteorological Society 60
(10), 1177–1187.
Stenchikov, G.L., Hamilton, K., Robock, A., Ramaswamy, V.,
Schwarzkopf, M.D., Daniel, M., 2004. Arctic oscillation
response to the 1991 Pinatubo eruption in the SKYHI general
circulation model with a realistic quasi-biennial oscillation.
Journal of Geophysical Research 109 (D3), D03112.
Strobel, D.F., 1978. Parametrisation of the atmospheric heating
rate from 15 to 120 km due to O2 and O3 absorption
of solar radiation. Journal of Geophysical Research 83,
6225–6230.
Yang, F., Schlesinger, M.E., 2002. On the surface and atmospheric temperature changes following the 1991 Pinatubo
volcanic eruption: A GCM study. Journal of Geophysical
Research 107 (D8).
Zhu, X., 1994. An accurate and efficient radiation algorithm for
middle atmosphere models. Journal of Atmospheric Science
51, 3593–3614.