scholarly journals Future Changes and Controlling Factors of the Eight Regional Monsoons Projected by CMIP6 Models

2020 ◽  
Vol 33 (21) ◽  
pp. 9307-9326
Author(s):  
Chunhan Jin ◽  
Bin Wang ◽  
Jian Liu
Keyword(s):  
Monsoon Rainfall ◽  
Rainfall Variability ◽  
Coupled Model ◽  
Summer Rainfall ◽  
Winter Precipitation ◽  
Specific Humidity ◽  
North American Monsoon ◽  
Central Pacific ◽  
The North ◽  
Spread Analysis

AbstractAn accurate prediction of land monsoon precipitation (LMP) is critical for the sustainable future of the planet as it provides water resources for more than two-thirds of the global population. Here, we show that the ensemble mean of 24 CMIP6 (phase 6 of the Coupled Model Intercomparison Project) models projects that, under the Shared Socioeconomic Pathway 2–4.5 (SSP2–4.5) scenario, summer LMP will very likely increase in South Asia (~4.1% °C−1), likely increase in East Asia (~4.6% °C−1) and northern Africa (~2.9% °C−1), and likely decrease in North America (~−2.3% °C−1). The annual mean LMP in three Southern Hemisphere monsoon regions will likely remain unchanged due to significantly decreased winter precipitation. Regional mean LMP changes are dominated by the change in upward moisture transport with moderate contribution from evaporation and can be approximated by the changes of the product of the midtropospheric ascent and 850-hPa specific humidity. Greenhouse gas (GHG)-induced thermodynamic effects increase moisture content and stabilize the atmosphere, tending to offset each other. The spatially uniform increase of humidity cannot explain markedly different regional LMP changes. Intermodel spread analysis demonstrates that the GHG-induced circulation changes (dynamic effects) are primarily responsible for the regional differences. The GHGs induce a warm land–cool ocean pattern that strengthens the Asian monsoon, and a warm North Atlantic and Sahara that enhances the northern African monsoon, as well as an equatorial central Pacific warming that weakens the North American monsoon. CMIP6 models generally capture realistic monsoon rainfall climatology, but commonly overproduce summer rainfall variability. The models’ biases in projected regional SST and land–sea thermal contrast likely contribute to the models’ uncertainties in the projected monsoon rainfall changes.

scholarly journals CMIP5 Simulations of Low-Level Tropospheric Temperature and Moisture over the Tropical Americas

2013 ◽  
Vol 26 (17) ◽  
pp. 6257-6286 ◽  
Author(s):  
Leila M. V. Carvalho ◽  
Charles Jones
Keyword(s):  
Daily Precipitation ◽  
Monsoon Season ◽  
Coupled Model ◽  
Specific Humidity ◽  
Cmip5 Models ◽  
North American Monsoon ◽  
Tropospheric Temperature ◽  
The North ◽  
Decadal Variations ◽  
Monsoon System

Abstract Global warming has been linked to systematic changes in North and South America's climates and may severely impact the North American monsoon system (NAMS) and South American monsoon system (SAMS). This study examines interannual-to-decadal variations and changes in the low-troposphere (850 hPa) temperature (T850) and specific humidity (Q850) and relationships with daily precipitation over the tropical Americas using the NCEP–NCAR reanalysis, the Climate Forecast System Reanalysis (CFSR), and phase 5 of the Coupled Model Intercomparison Project (CMIP5) simulations for two scenarios: “historic” and high-emission representative concentration pathway 8.5 (RCP8.5). Trends in the magnitude and area of the 85th percentiles were distinctly examined over North America (NA) and South America (SA) during the peak of the respective monsoon season. The historic simulations (1951–2005) and the two reanalyses agree well and indicate that significant warming has occurred over tropical SA with a remarkable increase in the area and magnitude of the 85th percentile in the last decade (1996–2005). The RCP8.5 CMIP5 ensemble mean projects an increase in the T850 85th percentile of about 2.5°C (2.8°C) by 2050 and 4.8°C (5.5°C) over SA (NA) by 2095 relative to 1955. The area of SA (NA) with T850 ≥ the 85th percentile is projected to increase from ~10% (15%) in 1955 to ~58% (~33%) by 2050 and ~80% (~50%) by 2095. The respective increase in the 85th percentile of Q850 is about 3 g kg−1 over SAMS and NAMS by 2095. CMIP5 models project variable changes in daily precipitation over the tropical Americas. The most consistent is increased rainfall in the intertropical convergence zone in December–February (DJF) and June–August (JJA) and decreased precipitation over NAMS in JJA.

scholarly journals On the Relationship between Winter Sea Ice and Summer Atmospheric Circulation over Eurasia

2013 ◽  
Vol 26 (15) ◽  
pp. 5523-5536 ◽  
Author(s):  
Bingyi Wu ◽  
Renhe Zhang ◽  
Rosanne D'Arrigo ◽  
Jingzhi Su
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
Rainfall Variability ◽  
Summer Rainfall ◽  
Eastern Coast ◽  
Northern Eurasia ◽  
Sea Ice Concentration ◽  
The North ◽  
Circulation Anomalies ◽  
Atmospheric Circulation Anomalies

Abstract Using NCEP–NCAR reanalysis and Japanese 25-yr Reanalysis (JRA-25) data, this paper investigates the association between winter sea ice concentration (SIC) in Baffin Bay southward to the eastern coast of Newfoundland, and the ensuing summer atmospheric circulation over the mid- to high latitudes of Eurasia. It is found that winter SIC anomalies are significantly correlated with the ensuing summer 500-hPa height anomalies that dynamically correspond to the Eurasian pattern of 850-hPa wind variability and significantly influence summer rainfall variability over northern Eurasia. Spring atmospheric circulation anomalies south of Newfoundland, associated with persistent winter–spring SIC and a horseshoe-like pattern of sea surface temperature (SST) anomalies in the North Atlantic, act as a bridge linking winter SIC and the ensuing summer atmospheric circulation anomalies over northern Eurasia. Indeed, this study only reveals the association based on observations and simple simulation experiments with SIC forcing. The more precise mechanism for this linkage needs to be addressed in future work using numerical simulations with SIC and SST as the external forcings. The results herein have the following implication: Winter SIC west of Greenland is a possible precursor for summer atmospheric circulation and rainfall anomalies over northern Eurasia.

scholarly journals The Multidecadal Atlantic SST—Sahel Rainfall Teleconnection in CMIP5 Simulations

2014 ◽  
Vol 27 (2) ◽  
pp. 784-806 ◽  
Author(s):  
Elinor R. Martin ◽  
Chris Thorncroft ◽  
Ben B. B. Booth
Keyword(s):  
North Atlantic ◽  
Rainfall Variability ◽  
Coupled Model ◽  
Multidecadal Variability ◽  
The North ◽  
Sst Variability ◽  
Tropical North Atlantic ◽  
Sahel Rainfall ◽  
Intercomparison Project ◽  
The Indian Ocean

Abstract This study uses models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) to evaluate and investigate Sahel rainfall multidecadal variability and teleconnections with global sea surface temperatures (SSTs). Multidecadal variability is lower than observed in all historical simulations evaluated. Focus is on teleconnections with North Atlantic SST [Atlantic multidecadal variability (AMV)] as it is more successfully simulated than the Indian Ocean teleconnection. To investigate why some models successfully simulated this teleconnection and others did not, despite having similarly large AMV, two groups of models were selected. Models with large AMV were highlighted as good (or poor) by their ability to simulate relatively high (low) Sahel multidecadal variability and have significant (not significant) correlation between multidecadal Sahel rainfall and an AMV index. Poor models fail to capture the teleconnection between the AMV and Sahel rainfall because the spatial distribution of SST multidecadal variability across the North Atlantic is incorrect. A lack of SST signal in the tropical North Atlantic and Mediterranean reduces the interhemispheric SST gradient and, through circulation changes, the rainfall variability in the Sahel. This pattern was also evident in the control simulations, where SST and Sahel rainfall variability were significantly weaker than historical simulations. Errors in SST variability were suggested to result from a combination of weak wind–evaporation–SST feedbacks, poorly simulated cloud amounts and feedbacks in the stratocumulus regions of the eastern Atlantic, dust–SST–rainfall feedbacks, and sulfate aerosol interactions with clouds. By understanding the deficits and successes of CMIP5 historical simulations, future projections and decadal hindcasts can be examined with additional confidence.

scholarly journals Variation of the North American Summer Monsoon Regimes and the Atlantic Multidecadal Oscillation

2008 ◽  
Vol 21 (11) ◽  
pp. 2371-2383 ◽  
Author(s):  
Qi Hu ◽  
Song Feng
Keyword(s):  
United States ◽  
North American ◽  
Summer Rainfall ◽  
Atlantic Multidecadal Oscillation ◽  
North American Monsoon ◽  
Western North America ◽  
The North ◽  
West Mexico ◽  
Central United States ◽  
Rainfall Variations

Abstract The North American summer monsoon holds the key to understanding warm season rainfall variations in the region from northern Mexico to the Southwest and the central United States. Studies of the monsoon have pictured mosaic submonsoonal regions and different processes influencing monsoon variations. Among the influencing processes is the “land memory,” showing primarily the influence of the antecedent winter season precipitation (snow) anomalies in the Northwest on summer rainfall anomalies in the Southwest. More intriguingly, the land memory has been found to vary at the multidecadal time scale. This memory change may actually reflect multidecadal variations of the atmospheric circulation in the North American monsoon region. This notion is examined in this study by first establishing the North American monsoon regimes from relationships of summer rainfall variations in central and western North America, and then quantifying their variations at the multidecadal scale in the twentieth century. Results of these analyses show two monsoon regimes: one featured with consistent variations in summer rainfall in west Mexico and the Southwest and an opposite variation pattern in the central United States, and the other with consistent rainfall variations in west Mexico and the central United States but different from the variations in the southwest United States. These regimes have alternated at multidecadal scales in the twentieth century. This alternation of the regimes is found to be in phase with the North Atlantic Multidecadal Oscillation (AMO). In warm and cold phases of the AMO, distinctive circulation anomalies are found in central and western North America, where lower than average pressure prevailed in the warm phase and the opposite anomaly in the cold phase. Associated wind anomalies configured different patterns for moisture transport and may have contributed to the development and variation of the monsoon regimes. These results indicate that investigations of the effects of AMO and its interaction with the North Pacific circulations could lead to a better understanding of the North American monsoon variations.

scholarly journals Empiric Forecasting of Dominant Modes to Summer Precipitation Anomaly of Northeast Brazil

2020 ◽  
Vol 9 (6) ◽  
pp. 353
Author(s):  
Rodrigo Lins Da Rocha Júnior ◽  
Fabrício Daniel Dos Santos Silva ◽  
Rafaela Lisboa Costa ◽  
Heliofábio Barros Gomes
Keyword(s):  
Rainfall Variability ◽  
Summer Precipitation ◽  
Summer Rainfall ◽  
Precipitation Anomaly ◽  
Linear Regression Models ◽  
Equatorial Atlantic ◽  
Economic Activities ◽  
Climate Forecasting ◽  
The North ◽  
Brazilian Northeast

The main economic activities of the Brazilian Northeast (NEB) are affected by the region's highly variable climate, requiring research into seasonal climate forecasting. In a work we show the results obtained after analysing the relationship between the main modes of NEB rainfall variability and lagged oceanic and atmospheric variable fields, that is, preceding rainfall. Consistent relationships were found between sea surface temperature (SST) in the Equatorial Pacific, Equatorial Atlantic and South Atlantic with NEB rainfall. Rossby wave patterns over the North Pacific that propagate from west to east to the Intertropical Convergence Zone (ITCZ), Walker Cell and Upper Bolivia have also been identified. In this research, the main objective was to identify the physical basis for the construction of linear regression models capable of predicting seasonal summer rainfall in the NEB, from the relationships between predictor-predictor. The adjusted regression model performed well between simulations and observations based on validation metrics and can be reliably indicated for operational climate forecasting systems. 

Change in Coherence of Summer Rainfall Variability over the Western Pacific around the Early 2000s: ENSO Influence

2020 ◽  
Vol 33 (3) ◽  
pp. 1105-1119 ◽  
Author(s):  
Zhuoqi He ◽  
Weiqiang Wang ◽  
Renguang Wu ◽  
In-Sik Kang ◽  
Chao He ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Rainfall Variability ◽  
Summer Rainfall ◽  
Rainfall Anomaly ◽  
Western Pacific ◽  
Northern Indian Ocean ◽  
Central Pacific ◽  
Enso Events ◽  
The Western Pacific ◽  
Sst Anomalies

AbstractThis study is the second part of a two-part series investigating a recent decadal modulation of interannual variability over the western Pacific Ocean around the early 2000s. Observational evidence shows that the anomalous Philippine Sea cyclonic circulation retreats eastward, with the western Pacific rainfall anomaly distribution changing from a north–south tripole pattern to an east–west dipole pattern after 2003–04. These changes are attributed to a change in El Niño–Southern Oscillation (ENSO) properties and the associated Indo-Pacific sea surface temperature (SST) anomaly pattern. Before the early 2000s, slow-decaying ENSO events induce large SST anomalies in the northern Indian Ocean during the following summer. The northern Indian Ocean SST anomalies act together with the opposite-sign SST anomalies in the tropical central Pacific, leading to a zonally extended anomalous lower-level cyclonic (anticyclonic) circulation and an elongated rainfall anomaly band over the western Pacific. After the early 2000s, ENSO events have a shortened period and a weakened amplitude, and the eastern Pacific SST anomalies tend to undergo a phase transition from winter to summer. Consequently, the influence of ENSO on the Indian Ocean SST anomalies is weakened and the contribution of the northern Indian Ocean SST anomalies to the western Pacific summer rainfall variability becomes insignificant. In this case, the western North Pacific summer rainfall is mainly dominated by the well-developed tropical Pacific SST forcing following the early decay of ENSO events. The potential physical mechanism for the two types of ENSO influences is validated with regional decoupled Community Earth System Model experiments.

Reply to “Comments on ‘Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States’”

2013 ◽  
Vol 26 (2) ◽  
pp. 683-688 ◽  
Author(s):  
Wenhong Li ◽  
Laifang Li ◽  
Rong Fu ◽  
Yi Deng ◽  
Hui Wang
Keyword(s):  
North Atlantic ◽  
Rainfall Variability ◽  
Southeastern United States ◽  
Summer Rainfall ◽  
Subtropical High ◽  
North Atlantic Subtropical High ◽  
The North ◽  
Westward Movement ◽  
The North Atlantic ◽  
Potential Impact

Abstract Recently Diem questioned the western ridge movement of the North Atlantic subtropical high (NASH) reported in a 2011 paper of Li et al. This reply shows more analysis that further strengthens the conclusions originally put forth by Li et al. Diem’’s analysis of the trend in the western ridge of the NASH was based on the data over a 30-yr period (1978–2007), whereas the main conclusions in Li et al. were drawn according to the data over a 60-yr period (1948–2007). Over the last 60 years, the NASH has shown a significant trend of westward movement, the meridional movement of the western ridge of the NASH has enhanced in the recent three decades, and the potential impact of global warming cannot be ruled out in an attempt to explain these changes of the NASH.

Sign in / Sign up

Export Citation Format

Share Document