Study of the Indian summer monsoon using WRF-ROMS regional coupled model simulations

From the 1980s, Indian summer monsoon rainfall (ISMR) shows a decreasing trend over north and northwest India, and there was a significant observed reduction in July over central and south India in 1982–2003. The key drivers of the changed ISMR, however, remain unclear. It was hypothesized that the large-scale irrigation development that started in the 1950s has resulted in land surface cooling, which slowed large-scale atmospheric circulation, exerting significant influences on ISMR. To test this hypothesis, a fully coupled model, the CESM v1.0.3, was used with a global irrigation dataset. In this study, spatially varying irrigation-induced feedback mechanisms are investigated in detail at different stages of the monsoon. Results show that soil moisture and evapotranspiration increase significantly over India throughout the summertime because of the irrigation. However, 2-m air temperature shows a significant reduction only in a limited region because the temperature change is influenced simultaneously by surface incoming shortwave radiation and evaporative cooling resulting from the irrigation, especially over the heavily irrigated region. Irrigation also induces a 925-hPa northeasterly wind from 30°N toward the equator. This is opposite to the prevailing direction of the Indian summer monsoon (ISM) wind that brings moist air to India. The modeled rainfall in the irrigated case significantly decreases up to 1.5 mm day−1 over central and north India from July to September. This paper reveals that the irrigation can contribute to both increasing and decreasing the surface temperature via multiple feedback mechanisms. The net effect is to weaken the ISM with the high spatial and temporal heterogeneity.

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Role of the Indian Ocean in the Biennial Transition of the Indian Summer Monsoon

Journal of Climate ◽

10.1175/jcli4127.1 ◽

2007 ◽

Vol 20 (10) ◽

pp. 2147-2164 ◽

Cited By ~ 19

Author(s):

Renguang Wu ◽

Ben P. Kirtman

Keyword(s):

Indian Ocean ◽

Summer Monsoon ◽

Indian Summer Monsoon ◽

Indian Monsoon ◽

Coupled Model ◽

The Pacific ◽

The Indian Ocean ◽

Biennial Variability ◽

Sst Anomalies

Abstract The biennial variability is a large component of year-to-year variations in the Indian summer monsoon (ISM). Previous studies have shown that El Niño–Southern Oscillation (ENSO) plays an important role in the biennial variability of the ISM. The present study investigates the role of the Indian Ocean in the biennial transition of the ISM when the Pacific ENSO is absent. The influence of the Indian and Pacific Oceans on the biennial transition between the ISM and the Australian summer monsoon (ASM) is also examined. Controlled numerical experiments with a coupled general circulation model (CGCM) are used to address the above two issues. The CGCM captures the in-phase ISM to ASM transition (i.e., a wet ISM followed by a wet ASM or a dry ISM followed by a dry ASM) and the out-of-phase ASM to ISM transition (i.e., a wet ASM followed by a dry ISM or a dry ASM followed by a wet ISM). These transitions are more frequent than the out-of-phase ISM to ASM transition and the in-phase ASM to ISM transition in the coupled model, consistent with observations. The results of controlled coupled model experiments indicate that both the Indian and Pacific Ocean air–sea coupling are important for properly simulating the biennial transition between the ISM and ASM in the CGCM. The biennial transition of the ISM can occur through local air–sea interactions in the north Indian Ocean when the Pacific ENSO is suppressed. The local sea surface temperature (SST) anomalies induce the Indian monsoon transition through low-level moisture convergence. Surface evaporation anomalies, which are largely controlled by surface wind speed changes, play an important role for SST changes. Different from local air–sea interaction mechanisms proposed in previous studies, the atmospheric feedback is not strong enough to reverse the SST anomalies immediately at the end of the monsoon season. Instead, the reversal of the SST anomalies is accomplished in the spring of the following year, which in turn leads to the Indian monsoon transition.

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On the response of Indian summer monsoon to aerosol forcing in CMIP5 model simulations

Climate Dynamics ◽

10.1007/s00382-015-2516-2 ◽

2015 ◽

Vol 45 (9-10) ◽

pp. 2949-2961 ◽

Cited By ~ 25

Author(s):

S. D. Sanap ◽

G. Pandithurai ◽

M. G. Manoj

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Cmip5 Model ◽

Model Simulations ◽

Aerosol Forcing

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Indian summer monsoon prediction and simulation in CFSv2 coupled model

Atmospheric Science Letters ◽

10.1002/asl.599 ◽

2015 ◽

Vol 17 (1) ◽

pp. 57-64 ◽

Cited By ~ 23

Author(s):

Gibies George ◽

D. Nagarjuna Rao ◽

C. T. Sabeerali ◽

Ankur Srivastava ◽

Suryachandra A. Rao

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Coupled Model ◽

Prediction And Simulation

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Etesians and the summer circulation over East Mediterranean in Coupled Model Intercomparison Project Phase 5 simulations: Connections to the Indian summer monsoon

International Journal of Climatology ◽

10.1002/joc.6259 ◽

2019 ◽

Vol 40 (2) ◽

pp. 1118-1131

Author(s):

Ioannis Logothetis ◽

Kleareti Tourpali ◽

Stergios Misios ◽

Prodromos Zanis

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Coupled Model ◽

Model Intercomparison ◽

East Mediterranean ◽

Summer Circulation ◽

Intercomparison Project

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Model Uncertainty in the Projected Indian Summer Monsoon Precipitation Change under Low-Emission Scenarios

Atmosphere ◽

10.3390/atmos12020248 ◽

2021 ◽

Vol 12 (2) ◽

pp. 248

Author(s):

Shang-Min Long ◽

Gen Li

Keyword(s):

Summer Monsoon ◽

Indian Summer Monsoon ◽

Model Uncertainty ◽

Signal To Noise Ratio ◽

Coupled Model ◽

Precipitation Change ◽

Emission Scenarios ◽

Intergovernmental Panel ◽

Low Emission ◽

Precipitation Changes

The projected ISM precipitation changes under low-emission scenarios, Representative Concentration Pathway 2.6 (RCP2.6) and Shared Socioeconomic Pathway 1-2.6 (SSP1-2.6), are investigated by outputs from models participating in phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). Based on the high-emission scenarios like RCP8.5, the Intergovernmental Panel on Climate Change Fifth Assessment Report suggests a wetter Indian summer monsoon (ISM) by the end of 21st century. Although the multi-model ensemble mean (MME) ISM precipitation under RCP2.6 and SSP1-2.6 is still projected to increase over 2050–2099 referenced to 1900–1949, the intermodel spread of the ISM precipitation change is tremendous in both CMIPs. Indeed, the signal-to-noise ratio (SNR) of ISM precipitation change, defined as the MME divided by its intermodel standard deviation, is even below 1 under the low-emission scenarios. This casts doubts on a future wetter ISM in a warmer climate. Moisture budget analyses further show that most of the model uncertainty in ISM precipitation change is caused by its dynamical component from the atmospheric circulation change. As expected, the interhemispheric surface warming contrast is essential in causing the intermodel differences in ISM circulation and precipitation changes under low-emission scenarios. In addition, the projected wetter ISM is prominently enhanced from CMIP5 to CMIP6, along with reduced model uncertainty. However, the resultant increased SNR in CMIP6 is still low in most ISM regions. The results imply that ISM precipitation change is highly uncertain under low-emission scenarios, which greatly challenges the decisions-making in adaptation policies for the densely populated South Asian countries.

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