Monsoon

About: Monsoon is a research topic. Over the lifetime, 16087 publications have been published within this topic receiving 599888 citations.

Coupled Model Simulations of the West African Monsoon System: Twentieth- and Twenty-First-Century Simulations

Abstract: The ability of coupled GCMs to correctly simulate the climatology and a prominent mode of variability of the West African monsoon is evaluated, and the results are used to make informed decisions about which models may be producing more reliable projections of future climate in this region. The integrations were made available by the Program for Climate Model Diagnosis and Intercomparison for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. The evaluation emphasizes the circulation characteristics that support the precipitation climatology, and the physical processes of a “rainfall dipole” variability mode that is often associated with dry conditions in the Sahel when SSTs in the Gulf of Guinea are anomalously warm. Based on the quality of their twentieth-century simulations over West Africa in summer, three GCMs are chosen for analysis of the twenty-first century integrations under various assumptions about future greenhouse gas increases. Each of these models behav...

Annual Cycle of Southeast Asia—Maritime Continent Rainfall and the Asymmetric Monsoon Transition

Abstract: In general, the Bay of Bengal, Indochina Peninsula, and Philippines are in the Asian summer monsoon regime while the Maritime Continent experiences a wet monsoon during boreal winter and a dry season during boreal summer. However, the complex distribution of land, sea, and terrain results in significant local variations of the annual cycle. This work uses historical station rainfall data to classify the annual cycles of rainfall over land areas, the TRMM rainfall measurements to identify the monsoon regimes of the four seasons in all of Southeast Asia, and the QuikSCAT winds to study the causes of the variations. The annual cycle is dominated largely by interactions between the complex terrain and a simple annual reversal of the surface monsoonal winds throughout all monsoon regions from the Indian Ocean to the South China Sea and the equatorial western Pacific. The semiannual cycle is comparable in magnitude to the annual cycle over parts of the equatorial landmasses, but only a very small regio...

Solar influence on the Indian summer monsoon during the Holocene

Abstract: [1] The large (8%) changes in the past seasonal insolation have a well-documented influence on the Indian summer monsoon. However, the effect of the small (<1%) decade to century scale solar variability is less certain. Evidence is emerging that Earth's climate is sensitive to small changes in solar output on centennial time scale during the Holocene. Comparison of a recently published proxy record for sunspot activity with our newly-revised higher-resolution record of the Indian summer monsoon winds reveals multiple intervals of weak summer monsoon during the Holocene at multidecadal to centennial scales. Weak summer monsoon winds correlate with reduced solar output. Our results suggest that small changes in solar irradiance can bring pronounced changes in the tropical monsoon. The multidecade to century scale variations in the monsoon winds were much larger in the early Holocene coincident with increased sunspot numbers.

Detection, causes and projection of climate change over China: An overview of recent progress

Abstract: This article summarizes the main results and findings of studies conducted by Chinese scientists in the past five years It is shown that observed climate change in China bears a strong similarity with the global average The country-averaged annual mean surface air temperature has increased by 11°C over the past 50 years and 05–08°C over the past 100 years, slightly higher than the global temperature increase for the same periods Northern China and winter have experienced the greatest increases in surface air temperature Although no significant trend has been found in country-averaged annual precipitation, interdecadal variability and obvious trends on regional scales are detectable, with northwestern China and the mid and lower Yangtze River basin having undergone an obvious increase, and North China a severe drought Some analyses show that frequency and magnitude of extreme weather and climate events have also undergone significant changes in the past 50 years or so Studies of the causes of regional climate change through the use of climate models and consideration of various forcings, show that the warming of the last 50 years could possibly be attributed to an increased atmospheric concentration of greenhouse gases, while the temperature change of the first half of the 20th century may be due to solar activity, volcanic eruptions and sea surface temperature change A significant decline in sunshine duration and solar radiation at the surface in eastern China has been attributed to the increased emission of pollutants Projections of future climate by models of the NCC (National Climate Center, China Meteorological Administration) and the IAP (Institute of Atmospheric Physics, Chinese Academy of Sciences), as well as 40 models developed overseas, indicate a potential significant warming in China in the 21st century, with the largest warming set to occur in winter months and in northern China Under varied emission scenarios, the country-averaged annual mean temperature is projected to increase by 15–21°C by 2020, 23–33°C by 2050, and by 39–60°C by 2100, in comparison to the 30-year average of 1961–1990 Most models project a 10%–12% increase in annual precipitation in China by 2100, with the trend being particularly evident in Northeast and Northwest China, but with parts of central China probably undergoing a drying trend Large uncertainty exists in the projection of precipitation, and further studies are needed Furthermore, anthropogenic climate change will probably lead to a weaker winter monsoon and a stronger summer monsoon in eastern Asia

Orbital‐scale timing and mechanisms driving Late Pleistocene Indo‐Asian summer monsoons: Reinterpreting cave speleothem δ18O

Abstract: [1] Southeast China cave δ18O, often interpreted as a pure East Asian summer monsoon proxy, lags maximum northern hemisphere summer insolation by 2.9 ± 0.3 kyrs at the precession cycle. The Arabian Sea summer monsoon stack lags by 8 ± 1 kyr, consistent with 13 other Indian and East Asian summer monsoon proxies from marine, lake, and terrestrial archives. This 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology; it requires reconciliation in the context of proxy interpretation. Both of these lags are incompatible with a direct response to northern hemisphere summer insolation, implicating additional forcing mechanisms. Analysis of heterodynes in the cave δ18O spectrum demonstrates that variance contained in the Arabian Sea summer monsoon proxies also resides in the cave δ18O record. This variance is subtracted from the cave δ18O record yielding a residual that is highly coherent and in phase with precession minima, reflecting the impact of winter temperature change on cave δ18O (meteorological precipitation under cold conditions). Thus, we argue that the timing of light cave δ18O peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone. The 2.9 kyr precession band phase lag of cave δ18O reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima. This interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast China.