Sensitivity of the Asian summer monsoon to the horizontal resolution: Differences between AMIP-type and coupled model experiments

A set of experiments forced with observed
SST has been performed with the Echam4 atmospheric
GCM at three different horizontal resolutions (T30,
T42 and T106). These experiments have been used to
study the sensitivity of the simulated Asian summer
monsoon (ASM) to the horizontal resolution. The
ASM is reasonably well simulated by the Echam4
model at all resolutions. In particular, the low-level
westerly flow, that is the dominant manifestation of the
Asian summer monsoon, is well captured by the model,
and the precipitation is reasonably simulated in intensity
and space appearance. The main improvements
due to an higher resolution model are associated to
regional aspects of the precipitation, for example the
Western Ghats precipitation is better reproduced. The
interannual variability of precipitation and wind fields
in the Asian monsoon region appears to be less affected
by an increase in the horizontal resolution than
the mean climatology is. A possible reason is that the
former is mainly SST-forced. Besides, the availability
of experiments at different horizontal resolution realized
with the Echam4 model coupled to a global oceanic
model allows the possibility to compare these
simulations with the experiments previously described.
This analysis showed that the coupled model is able to
reproduce a realistic monsoon, as the basic dynamics of
the phenomenon is captured. The increase of the horizontal
resolution of the atmospheric component
influences the simulated monsoon with the same
characteristics of the forced experiments. Some basic
features of the Asian summer monsoon, as the interannual
variability and the connection with ENSO, are
further investigated.

Annamalai H, Slingo JM, Sperber KR, Hodges K (1999) The
mean evolution and variability of the Asian summer monsoon:
comparison of ECMWF and NCEP/NCAR reanalysis.
Mon Weather Rev 127:1157–1186
Cherchi A, Navarra A (2003) Reproducibility and predictability
of the Asian summer monsoon in the Echam4 GCM. Clim
Dyn 20:365–379
Clark CO, Cole JE and Webster PJ (2000) Indian Ocean SST
and Indian summer monsoon rainfall: predictive relationships
and their decadal variability. J Clim 13:2503–2519
Du¨ menil L, Bauer HS (1998) The tropical easterly jet in a
hierarchy of GCMs and reanalyses. MPI-Report 247:45 pp
Fennessy MJ, Kinter III JL, Kirtman B, Marx L, Nigam S,
Schneider E, Shukla J, Straus D, Vernekar A, Xue X, Zhou
J (1994) The simulated Indian monsoon: a GCM sensitivity
study. J Clim 7:33–43
Fu X, Wang B, Li T (2002) Impacts of air–sea coupling on the
simulation of mean Asian summer monsoon in the ECHAM4
model. Mon Weather Rev 130:2889–2904
Gates WL (1992) AMIP: the atmospheric model intercomparison
project. Bull Am Meteorol Soc 73:1962–1970
Goswami BN (1998) Interannual variations of Indian summer
monsoon in a GCM: external conditions versus internal
feedbacks. J Clim 11:501–521
Goswami BN, Krishnamurthy V, Annamalai H (1999) A broad
scale circulation index for the interannual variability of the
Indian summer monsoon. Q J R Meteor Soc 125:611–633
Gualdi S, Navarra A, Guilyardi E, Delecluse P (2003) Assessment
of the tropical Indo-Pacific climate in the SINTEX
CGCM. Ann Geophys 46:1–26
Guilyardi E, Delecluse P, Gualdi S, Navarra A (2003) Mechanisms
for ENSO phase change in a coupled GCM. J Clim
16:1141–1158
Hastenrath S (2000) Zonal circulations over the Equatorial Indian
Ocean. J Clim 13:2746–2756
Inatsu M, Kimoto M (2005) Difference of boreal summer climate
between coupled and atmosphere-only GCMs. SOLA
1:105–108 doi:10.2151/sola.2005-028
Ju J, Slingo J (1995) The Asian summer monsoon and ENSO. Q
J R Meteor Soc 121:1133-1168
Kinter III JL, Miyakoda K, Yang S (2002) Recent changes in the
connection from the Asian monsoon to ENSO. J Clim
15:1203–1215
Kitoh A, Arakawa O (1999) On overestimation of tropical precipitation
by and atmospheric GCM with prescribed SST.
Geophys Res Lett 26(19):2965–2968
Kitoh A, Yukimoto S, Noda A (1999) ENSO–monsoon relationship
in the MRI Coupled GCM. J Meteorol Soc Jpn
77:1221–1245
Kobayashi C, Sugi M (2004) Impact of horizontal resolution on
the simulation of the Asian summer monsoon and tropical
cyclones in the JMA global model. Clim Dyn 93:165–176
Kumar KK, Kleeman R, Cane MA, Rajagopalan B (1999a)
Epochal changes in Indian monsoon–ENSO precursors.
Geophys Res Lett 26(1):75–78
Kumar KK, Rajagopalan B, Cane MA (1999b) On the weakening
relationship between the Indian monsoon and ENSO.
Science 284:2156–2159
Latif M, Barnett TP (1994) Causes of decadal climate variability
over the North Pacific and North America. Science 266:634–
637
Lau NC, Nath MJ (2000) Impact of ENSO on the variability of
the Asian–Australian monsoons as simulated in GCM
experiments. J Clim 13:4287–4309
Lau KM, Kim KM, Yang S (2000) Dynamical and boundary
forcing characteristics of regional components of the Asian
summer monsoon. J Clim 13:2461–2482
Li C, Yanai M (1996) The onset and interannual variability of
the Asian summer monsoon in relation to land–sea thermal
contrast. J Clim 9:358–375
Lindzen RS, Nigam S (1987) On the role of sea surface temperature
gradients in forcing low-level winds and convergence
in the Tropics. J Atmos Sci 44(17):2418–2436
Madec G, Delecluse P, Imbard M, Levy C (1998) OPA version
8.1 Ocean general circulation model reference manual.
Technical report LODYC/IPSL Note 11
May W (2003) The Indian summer monsoon and its sensitivity to
the mean SSTs: simulations with the ECHAM4 AGCM at
T106 horizontal resolution. J Roy Meteorol Soc Jap
81(1):57–83
Meehl GA (1989) The coupled ocean–atmosphere modelling
problem in the tropical Pacific and Asian monsoon regions.
J Clim 2:1146–1163
Meehl GA, Arblaster JM (1998) The Asian–Australian monsoon
and El Nin˜ o-Southern Oscillation in the NCAR climate
system model. J Clim 11:1356–1385
Meehl GA, Gent P, Arblaster JM, Otto-Bliesner B, Brady E,
Craig A (2001) Factors that affect amplitude of El Nin˜o in
global coupled climate models. Clim Dyn 17:515–526
Miyakoda K, Navarra A, Ward MN (1999) Tropical-wide teleconnection
and oscillation. II: the ENSO-monsoon system.
Q J R Meteorol Soc 125: 2937–2963
Navarra A, Ward MN, Miyakoda K (1999) Tropical-wide teleconnection
and oscillation. I: teleconnection indices and
type I/type II states. Q J R Meteor Soc 125:2909–2935
Parthasarathy B, Munot AA, Kothwale DR (1992) Indian summer
monsoon rainfall indices: 1871–1990. Meteorol Mag
121:174–186
Rao KG and Goswami BN (1988) Interannual variations of sea
surface temperature over the Arabian sea and the Indian
monsoon. Mon Weather Rev 116:558–568
Rasmusson EM, Carpenter TH (1983) The relationship between
the Eastern Pacific sea surface temperature and rainfall over
India and Sri Lanka. Mon Weather Rev 111:517–528
Rayner NA, Parker DE, Horton EB, Folland CK, Alexander
LV, Frich P (2000) The HadISST1 global sea–ice and sea
surface temperature Dataset, 1871-1999. Hadley Centre
Technical Note 17
Roeckner E, Arpe K, Bengtsson L, Christoph M, Claussen M,
Du¨ menil L, Esch M, Giorgetta M, Schlese U, Schulzweida U
(1996) The Atmospheric general circulation Model ECHAM4:
model description and simulation of present-day
climate. Max-Planck Institut fu¨ r Meteorologie Report
no.218 Hamburg 86 pp
Shukla J (1987) Interannual variability of monsoons. In: Fein JS,
Stephenson PL (eds) Monsoons. Wiley, New York, pp 399–
464
Shukla J, Fennessy MJ (1994) Simulation and predictability of
monsoons. In: Proceedings of the International Conference
on Monsoon Variability and Prediction Tech. Rep. WCRP-
84 World Climate Research Program, Geneva, Switzerland
Soman MK, Slingo J (1997) Sensitivity of the Asian summer
monsoon to aspects of sea surface temperature anomalies in
the Tropical Pacific Ocean. Q J R Meteor Soc 123:309–336
Sperber KR, Palmer TN (1996) Interannual tropical rainfall
variability in general circulation model simulations associated
with the atmospheric model intercomparison project. J
Clim 9:2727–2750
Sperber K, Hameed S, Potter JL, Boyle JS (1994) Simulation of
the northern summer monsoon in the ECMWF model:
sensitivity to horizontal resolution. Mon Weather Rev
122:2461–2481
Sperber KR, Slingo JM, Annamalai H (2000) Predictability and
the relationship between subseasonal and interannual variability
during the Asian summer monsoon. Q J R Meteor
Soc 126:2545–2574
Stendel M, Roeckner E (1998) Impacts of horizontal resolution
on simulated climate statistics in ECHAM4. MPI-Report
253:57pp
Terray P, Guilyardi E, Fischer AS, Delecluse P (2005) Dynamics
of Indian Monsoon and ENSO relationships in a global
coupled model. Clim Dyn 24:145–168
Trenberth KE, Stepaniak DP, Caron JM (2002) Interannual
variations in the atmospheric heat budget. J Geophys Res
107(D8):AAC 4-1–15
Valcke S, Terray L, Piacentini A (2000) The Oasis coupler user
guide version 2.4. Technical report TR/CMGC/00-10
CERFACS
Wang B, Wu R, Lau KM (2001) Interannual variability of the
Asian summer monsoon: contrast between the Indian and
the Western North Pacific–East Asian monsoons. J Clim
14:4073–4090
Webster PJ, Yang S (1992) Monsoon and ENSO: selectively
interactive systems. Q J R Meteor Soc 118:877–926
Webster PJ, Magan˜ a V, Palmer TN, Shukla J, Tomas RA, Yanai
M, Yasunari T (1998) Monsoons: processes, predictability
and the prospects for prediction. J Geophys Res 103:14 451–
14 510
Xie P, Arkin P (1997) Global precipitation: a 17-year monthly
analysis based on gauge observations, satellite estimates,
and numerical model outputs. Bull Am Meteor Soc 78:2539–
2558
Zhang R, Sumi A, Kimoto M (1996) Impact of El Nin˜o on the
East Asian monsoon: a diagnostic study of the ’86–’87 and
’91–’92 events. J Meteorol Soc Jpn 74:49–62