scholarly journals Understanding Future Change of Global Monsoons Projected by CMIP6 Models

2020 ◽  
Vol 33 (15) ◽  
pp. 6471-6489 ◽  
Author(s):  
Bin Wang ◽  
Chunhan Jin ◽  
Jian Liu
Keyword(s):  
North American ◽  
Rainy Season ◽  
Monsoon Rainfall ◽  
North American Monsoon ◽  
Convective Heating ◽  
Monsoon Circulation ◽  
Future Change ◽  
Global Monsoon ◽  
African Monsoon ◽  
The Future

AbstractProjecting future change of monsoon rainfall is essential for water resource management, food security, disaster mitigation, and infrastructure planning. Here we assess the future change and explore the causes of the changes using 15 models that participated in phase 6 of the Coupled Model Intercomparison Project (CMIP6). The multimodel ensemble projects that, under the shared socioeconomic pathway (SSP) 2–4.5, the total land monsoon rainfall will likely increase in the Northern Hemisphere (NH) by about 2.8% per one degree Celsius of global warming (2.8% °C−1) in contrast to little change in the Southern Hemisphere (SH; −0.3% °C−1). In addition, in the future the Asian–northern African monsoon likely becomes wetter while the North American monsoon becomes drier. Since the humidity increase is nearly uniform in all summer monsoon regions, the dynamic processes must play a fundamental role in shaping the spatial patterns of the global monsoon changes. Greenhouse gas (GHG) radiative forcing induces a “NH-warmer-than-SH” pattern, which favors increasing the NH monsoon rainfall and prolonging the NH monsoon rainy season while reducing the SH monsoon rainfall and shortening the SH monsoon rainy season. The GHG forcing induces a “land-warmer-than-ocean” pattern, which enhances Asian monsoon low pressure and increases Asian and northern African monsoon rainfall, and an El Niño–like warming, which reduces North American monsoon rainfall. The uncertainties in the projected monsoon precipitation changes are significantly related to the models’ projected hemispheric and land–ocean thermal contrasts as well as to the eastern Pacific Ocean warming. The CMIP6 models’ common biases and the processes by which convective heating drives monsoon circulation are also discussed.

Drier North American Monsoon in Contrast to Asian–African Monsoon under Global Warming

2020 ◽  
Vol 33 (22) ◽  
pp. 9801-9816
Author(s):  
Chao He ◽  
Tim Li ◽  
Wen Zhou
Keyword(s):  
North American ◽  
Radiative Forcing ◽  
Monsoon Rainfall ◽  
Summer Monsoon Rainfall ◽  
North American Monsoon ◽  
Global Monsoon ◽  
African Monsoon ◽  
High Emission ◽  
Continental Area ◽  
Sst Warming

AbstractSummer monsoon rainfall supplies over 55% of annual precipitation to global monsoon regions. As shown by more than 70% of models, including 30 models from CMIP5 and 30 models from CMIP6 under high-emission scenarios, North American (NAM) monsoon rainfall decreases in a warmer climate, in sharp contrast to the robust increase in Asian–African monsoon rainfall. A hierarchy of model experiments is analyzed to understand the mechanism for the reduced NAM monsoon rainfall in this study. Modeling evidence shows that the reduction of NAM monsoon rainfall is related to both direct radiative forcing of increased CO2 concentration and SST warming, manifested as fast and slow responses to abrupt CO2 quadrupling in coupled GCMs. A cyclone anomaly forms over the Eurasian–African continental area due to enhanced land–sea thermal contrast under increased CO2 concentration, and this leads to a subsidence anomaly on its western flank, suppressing the NAM monsoon rainfall. The SST warming acts to further reduce the rainfall over the NAM monsoon region, and the El Niño–like SST warming pattern with enhanced SST warming over the equatorial Pacific plays a key role in suppressing NAM rainfall, whereas relative cooling over the subtropical North Atlantic has no contribution. A positive feedback between monsoon precipitation and atmospheric circulation helps to amplify the responses of monsoon rainfall.

Satellites reveal the strongest increase in duration of extreme dry periods in global monsoon regions

2020 ◽  
Author(s):  
Irina Y. Petrova ◽  
Diego G. Miralles ◽  
Hendrik Wouters
Keyword(s):  
Tropical Rainfall Measuring Mission ◽  
Annual Number ◽  
Drought Indices ◽  
Monsoon Circulation ◽  
Precipitation Data ◽  
Global Monsoon ◽  
Global Trends ◽  
Dry Spells ◽  
Hourly Data ◽  
The Future

<p align="justify">Drought is <span>arguably the climate phenomenon that most strongly impacts societies worldwide,</span> causing severe socioeconomic and ecologic damage. While models unanimously project an overall increase in aridity and drought occurrence in the future, observational evidence has so far been inconclusive. The discrepancies between the various drought definitions and drought indices has been a major factor contributing to our <span>low confidence in observed dryness trends. In this study we investigate global trends in meteorological dry spells using a simple, unambiguous and intuitive diagnostic: the maximum annual number of consecutive dry days (CDDs). In contrast to popular drought indices, the number of CDDs is a direct measure of the duration of rainfall scarcity, easy to quantify based on rain data, free of parametrizations, and independent from other proxies. </span></p><p align="justify"><span>Because the time-span of available satellite-based precipitation data records is constantly increasing, current products are becoming an alternative to </span><span><em>in situ</em></span><span> rain gauges </span><span>for</span><span> study</span><span>ing</span><span> long-term trends. In particular, the Tropical Rainfall Measuring Mission (TRMM) has now been operational for over twenty years, thus offering a unique opportunity to analyse temporally-coherent, single-platform precipitation data. Here, we use TRMM3B42 3-hourly data for 1998–2018 to calculate and analyse changes in the maximum annual number of CDDs worldwide. The robustness of the identified relationships among observational products is tested using recently-compiled gauge and satellite precipitation data from the </span><span>Frequent Rainfall Observations on GridS (</span><span>FROGS</span><span>)</span><span> database. </span></p><p align="justify">The r<span>esults reveal that almost 70% of the continental land monitored by TRMM has experienced an increase in duration of the longest annual dry period over the past 20 years, and in 20% of these regions trends </span><span>are found to be </span><span>significant (</span><span><em>p</em></span><span> < 0.01). Agreement among various observational products is regionally dependent. However, most of the data sets suggest that the signal largely originates, not from arid regions (which would support the dry–gets–drier paradigm), but from monsoon areas. Further analysis shows that the same areas experience clear increasing (decreasing) trends in rain seasonality (amount), suggesting a link to the monsoon circulation dynamics. A preliminary analysis confirms this connection and additionally points to the potentially important role of land feedbacks, revealing a tendency for later moisture build up and, hence, a monsoon onset after more prolonged dry seasons. Altogether, our findings emphasize the vulnerability of global monsoon regions to </span><span>climate</span><span> change. An increasing length of dry spells as we progress into the future might lead to devastating </span><span>socioeconomic and ecologic consequences in these regions.</span></p><p align="justify"> </p>

scholarly journals Land–Sea Thermal Contrast and Intensity of the North American Monsoon under Climate Change Conditions

2014 ◽  
Vol 27 (12) ◽  
pp. 4566-4580 ◽  
Author(s):  
Abraham Torres-Alavez ◽  
Tereza Cavazos ◽  
Cuauhtemoc Turrent
Keyword(s):  
North American ◽  
Climate Models ◽  
Global Climate ◽  
Coastal Region ◽  
Global Climate Models ◽  
North American Monsoon ◽  
Thermal Contrast ◽  
The North ◽  
The Future ◽  
The Mean

Abstract The hypothesis that global warming during the twenty-first century will increase the land–sea thermal contrast (LSTC) and therefore the intensity of early season precipitation of the North American monsoon (NAM) is examined. To test this hypothesis, future changes (2075–99 minus 1979–2004 means) in LSTC, moisture flux convergence (MFC), vertical velocity, and precipitation in the region are analyzed using six global climate models (GCMs) from phase 5 of the Coupled Model Intercomparison Project (CMIP5) under the representative concentration pathway 8.5 (RCP8.5) emission scenario. A surface LSTC index shows that the continent becomes warmer than the ocean in May in the North American Regional Reanalysis (NARR) and ECMWF Interim Re-Analysis (ERA-Interim) and in June in the mean ensemble of the GCMs (ens_GCMs), and the magnitude of the positive LSTC is greater in the reanalyses than in the ens_GCMs during the historic period. However, the reanalyses underestimate July–August precipitation in the NAM region, while the ens_GCMs reproduces the peak season surprisingly well but overestimates it the rest of the year. The future ens_GCMs projects a doubling of the magnitude of the positive surface LSTC and an earlier start of the continental summer warming in mid-May. Contrary to the stated hypothesis, however, the mean projection suggests a slight decrease of monsoon coastal precipitation during June–August (JJA), which is attributed to increased midtropospheric subsidence, a reduced midtropospheric LSTC, and reduced MFC in the NAM coastal region. In contrast, the future ens_GCMs produces increased MFC and precipitation over the adjacent mountains during JJA and significantly more rainfall over the entire NAM region during September–October, weakening the monsoon retreat.

SST data improve modeling of North American monsoon rainfall

Eos ◽  
2003 ◽  
Vol 84 (43) ◽  
pp. 457 ◽  
Author(s):  
X. Gao ◽  
S. Sorooshian ◽  
J. Li ◽  
J. Xu
Keyword(s):  
North American ◽  
Monsoon Rainfall ◽  
North American Monsoon

Seasonal Shifts in the North American Monsoon

2007 ◽  
Vol 20 (9) ◽  
pp. 1923-1935 ◽  
Author(s):  
Katrina Grantz ◽  
Balaji Rajagopalan ◽  
Martyn Clark ◽  
Edith Zagona
Keyword(s):  
United States ◽  
North American ◽  
Gulf Of California ◽  
Monsoon Rainfall ◽  
Monsoon Season ◽  
North American Monsoon ◽  
Southwestern United States ◽  
Monsoon Period ◽  
The North ◽  
Ocean Conditions

Abstract Analysis is performed on the spatiotemporal attributes of North American monsoon system (NAMS) rainfall in the southwestern United States. Trends in the timing and amount of monsoon rainfall for the period 1948–2004 are examined. The timing of the monsoon cycle is tracked by identifying the Julian day when the 10th, 25th, 50th, 75th, and 90th percentiles of the seasonal rainfall total have accumulated. Trends are assessed using the robust Spearman rank correlation analysis and the Kendall–Theil slope estimator. Principal component analysis is used to extract the dominant spatial patterns and these are correlated with antecedent land–ocean–atmosphere variables. Results show a significant delay in the beginning, peak, and closing stages of the monsoon in recent decades. The results also show a decrease in rainfall during July and a corresponding increase in rainfall during August and September. Relating these attributes of the summer rainfall to antecedent winter–spring land and ocean conditions leads to the proposal of the following hypothesis: warmer tropical Pacific sea surface temperatures (SSTs) and cooler northern Pacific SSTs in the antecedent winter–spring leads to wetter than normal conditions over the desert Southwest (and drier than normal conditions over the Pacific Northwest). This enhanced antecedent wetness delays the seasonal heating of the North American continent that is necessary to establish the monsoonal land–ocean temperature gradient. The delay in seasonal warming in turn delays the monsoon initiation, thus reducing rainfall during the typical early monsoon period (July) and increasing rainfall during the later months of the monsoon season (August and September). While the rainfall during the early monsoon appears to be most modulated by antecedent winter–spring Pacific SST patterns, the rainfall in the later part of the monsoon seems to be driven largely by the near-term SST conditions surrounding the monsoon region along the coast of California and the Gulf of California. The role of antecedent land and ocean conditions in modulating the following summer monsoon appears to be quite significant. This enhances the prospects for long-lead forecasts of monsoon rainfall over the southwestern United States, which could have significant implications for water resources planning and management in this water-scarce region.

scholarly journals Intensification of the North American Monsoon Rainfall as Observed From a Long‐Term High‐Density Gauge Network

2019 ◽  
Vol 46 (12) ◽  
pp. 6839-6847 ◽  
Author(s):  
Eleonora M. C. Demaria ◽  
Pieter Hazenberg ◽  
Russell L. Scott ◽  
Menberu B. Meles ◽  
Mary Nichols ◽  
...  
Keyword(s):  
North American ◽  
Monsoon Rainfall ◽  
High Density ◽  
North American Monsoon ◽  
The North

scholarly journals Future changes in monsoon duration and precipitation using CMIP6

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Suyeon Moon ◽  
Kyung-Ja Ha
Keyword(s):  
Rainy Season ◽  
Coupled Model ◽  
Future Climate ◽  
Future Scenarios ◽  
Model Intercomparison ◽  
Future Change ◽  
The Future ◽  
Intercomparison Project ◽  
Regional Monsoon ◽  
Thermodynamic Factors

AbstractFuture change in summertime rainfall under a warmer climate will impact the lives of more than two-thirds of the world’s population. However, the future changes in the duration of the rainy season affected by regional characteristics are not yet entirely understood. We try to understand changes in the length of the rainy season as well as the amounts of the future summertime precipitation, and the related processes over regional monsoon domains using phase six of the Coupled Model Intercomparison Project archive. Projections reveal extensions of the rainy season over the most of monsoon domains, except over the American monsoon. Enhancing the precipitation in the future climate has various increasing rates depending on the subregional monsoon, and it is mainly affected by changes in thermodynamic factors. This study promotes awareness for the risk of unforeseen future situations by showing regional changes in precipitation according to future scenarios.

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