Definition of new summer monsoon index for Vietnam region

2018 ◽  
Vol 60 (1) ◽  
pp. 90-96
Author(s):  
Dang Mau Nguyen ◽  
Van Thang Nguyen ◽  
Keyword(s):  
Summer Monsoon ◽  
Monsoon Index ◽  
Definition Of

scholarly journals Significant impact of the East Asia monsoon on ozone seasonal behavior in the boundary layer of Eastern China and the west Pacific region

2008 ◽  
Vol 8 (24) ◽  
pp. 7543-7555 ◽  
Author(s):  
Y. J. He ◽  
I. Uno ◽  
Z. F. Wang ◽  
P. Pochanart ◽  
J. Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
East Asia ◽  
Summer Monsoon ◽  
Eastern China ◽  
Pacific Region ◽  
The West ◽  
Seasonal Behavior ◽  
West Pacific ◽  
East Asia Monsoon ◽  
Monsoon Index

Abstract. The impact of the East Asia monsoon on the seasonal behavior of O3 in the boundary layer of Eastern China and the west Pacific region was analyzed for 2004–2006 by means of full-year nested chemical transport model simulations and continuous observational data obtained from three inland mountain sites in central and eastern China and three oceanic sites in the west Pacific region. The basic common features of O3 seasonal behaviors over all the monitoring sites are the pre- and post-monsoon peaks with a summer trough. Such bimodal seasonal patterns of O3 are predominant over the region with strong summer monsoon penetration, and become weaker or even disappear outside the monsoon region. The seasonal/geographical distribution of the pre-defined monsoon index indicated that the East Asia summer monsoon is responsible for the bimodal seasonal O3 pattern, and also partly account for the differences in the O3 seasonal variations between the inland mountain and oceanic sites. Over the inland mountain sites, the O3 concentration increased gradually from the beginning of the year, reached a maximum in June, decreased rapidly to the summer valley in July or August, and then peaked in September or October, thereafter decreased gradually again. Over the oceanic sites, O3 abundance showed a similar increasing trend beginning in January, but then decreased gradually from the end of March, followed by a wide trough with the minimum in July and August and a small peak in October or November. A sensitivity analysis performed by setting China-emission to zero revealed that the chemically produced O3 from China-emission contributed substantially to the O3 abundance, particularly the pre- and post-monsoon O3 peaks, over China mainland. We found that China-emission contributed more than 40% to total boundary layer O3 during summertime (60–70% in July) and accounted for about 40 ppb of each peak value over the inland region if without considering the effect of the nonlinear chemical productions. In contrast, over the oceanic region in the high monsoon index zone, the contribution of China-emission to total boundary layer O3 was always less than 20% (<10 ppb), and less than 10% in summer.

An improved south Asian summer monsoon index with Monte Carlo test

2005 ◽  
Vol 14 (4) ◽  
pp. 844-849 ◽  
Author(s):  
Shi Neng ◽  
Gu Jun-Qiang ◽  
Yi Yan-Ming ◽  
Lin Zhen-Min
Keyword(s):  
Monte Carlo ◽  
South Asian ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
South Asian Summer Monsoon ◽  
Monte Carlo Test ◽  
Monsoon Index ◽  
Asian Summer

scholarly journals Defining the Onset and End of the Indian Summer Monsoon

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Sarah Stanley
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Definition Of

A new, objective definition of the onset of the summer monsoon could improve predictions of rainfall in India.

scholarly journals Significant impact of the East Asia monsoon on ozone seasonal behavior in the boundary layer of Eastern China and the west Pacific region

2008 ◽  
Vol 8 (4) ◽  
pp. 14927-14955 ◽  
Author(s):  
Y. J. He ◽  
I. Uno ◽  
Z. F. Wang ◽  
P. Pochanart ◽  
J. Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
East Asia ◽  
Summer Monsoon ◽  
Eastern China ◽  
Pacific Region ◽  
The West ◽  
Seasonal Behavior ◽  
West Pacific ◽  
East Asia Monsoon ◽  
Monsoon Index

Abstract. The impact of the East Asia monsoon on the seasonal behavior of O3 in the boundary layer of Eastern China and the west Pacific region was analyzed for 2004–2006 by means of full-year nested chemical transport model simulations and continuous observational data obtained from three inland mountain sites in central and eastern China and three oceanic sites in the west Pacific region. The basic common features of O3 seasonal behaviors over all the monitoring sites are the pre- and post-monsoon peaks with a summer trough. Such bimodal seasonal patterns of O3 are predominant over the region with strong summer monsoon penetration, and become weaker or even disappear outside the monsoon region. The seasonal/geographical distribution of the pre-defined Monsoon Index indicated that the East Asia summer monsoon is responsible for the bimodal seasonal O3 pattern, and also partly account for the differences in the O3 seasonal variations between the inland mountain and oceanic sites. Over the inland mountain sites, the O3 concentration increased gradually from the beginning of the year, reached a maximum in June, decreased rapidly to a minimum in July or August, and then peaked in September or October, thereafter decreased gradually again. Over the oceanic sites, O3 abundance showed a similar increasing trend beginning in January, but then decreased gradually from the end of March, followed by a wide trough with the minimum in July and August and a small peak in October or November. A sensitivity analysis performed by setting China-emission to zero revealed that the chemically produced O3 from China-emission contributed more than 40% of total boundary layer O3 during summertime (60–70% in June) and accounted for about 40 ppb of each peak value over the inland region. In contrast, over the oceanic region in the high monsoon index zone, the contribution of China-emission to total O3 was always less than 20% (<10 ppb), and less than 10% in summer.

scholarly journals Impact of Northward-Propagating Intraseasonal Variability on the Onset of Indian Summer Monsoon

2014 ◽  
Vol 27 (1) ◽  
pp. 126-139 ◽  
Author(s):  
Lei Zhou ◽  
Raghu Murtugudde
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Large Scale ◽  
Southern Oscillation ◽  
Indian Subcontinent ◽  
Intraseasonal Variability ◽  
Monsoon Index ◽  
Process Understanding ◽  
Simple Regression Model ◽  
Predictive Understanding

Abstract The onset of the Indian summer monsoon (ISM) has a pronounced interannual variability, part of which originates from the large-scale circulation and its thermodynamic properties. While the northward-propagating intraseasonal variabilities (ISVs) are a prominent characteristic of the ISM, they tend to initiate an early onset by transferring moisture and momentum from the deep tropics to the Indian subcontinent. However, not all early onsets of ISM are attributable to strong ISVs and not all strong ISVs can lead to early ISM onsets. With a daily Indian monsoon index and a simple regression model, the onsets of ISM from 1982 to 2011 are separated into two groups. The years in which the early onsets of ISM are closely related to the northward-propagating ISVs are categorized as the ISVO years, and the other years in which the ISM onsets are not closely related to ISVs are categorized as non-ISVO years. The former category is the focus of this study. Before the onset of ISM in the ISVO years, the convective features are prominent, such as a cyclone over the Bay of Bengal (BoB) and the associated strong convection. The ocean–atmosphere interaction is found to be important for the northward-propagating ISVs before the ISM onset in the ISVO years. Evidence shows that warm SST anomalies drive the atmosphere and lead to atmospheric instability and convection. This reinforces the more recent view that the ocean does not just play a passive role in the northward-propagating ISVs. This process understanding helps shape the path to enhancing predictive understanding and monsoon prediction skills with obvious implications for the prediction of El Niño–Southern Oscillation.

scholarly journals Understanding the Variability of West African Summer Monsoon Rainfall: Contrasting Tropospheric Features and Monsoon Index

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 309
Author(s):  
Akintomide Afolayan Akinsanola ◽  
Wen Zhou
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Standardized Precipitation Index ◽  
Reanalysis Data ◽  
Summer Monsoon Rainfall ◽  
West African ◽  
Jet Streams ◽  
Large Variability ◽  
Low Level ◽  
Monsoon Index

West African Summer Monsoon (WASM) rainfall exhibits large variability at interannual and decadal timescales, causing droughts and floods in many years. Therefore it is important to investigate the major tropospheric features controlling the WASM rainfall and explore its potential to develop an objective monsoon index. In this study, monthly mean reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) and monthly rainfall data from three gridded observations during the 65-year period of 1950–2014 were employed. Dry and wet rainfall years were identified using a standardized precipitation index. In a composite analysis of wet and dry years, the dynamical features controlling the WASM exhibit an obvious contrast between these years, and a weaker (stronger) African Easterly Jet (Tropical Easterly Jet) is observed during the wet years. Also, a well-developed and deep low-level westerly flow at about 850 hPa is evident in wet years while an obvious reversal is observed in dry years. Considering this, the main regions of the two easterly jet streams and low-level westerly wind are proposed for objectively defining an effective WASM index (WASMI). The results indicate that the WASMI defined herein can reflect variations in June–September rainfall over West Africa. The index exhibits most of the variabilities observed in the rainfall series, with high (low) index values occurring in the 1950–1960s (1970–1980s), suggesting that the WASMI is skilled in capturing the respective wet and dry rainfall episodes over the region. Also, the WASMI is significantly correlated (r = 0.8) with summer monsoon rainfall, which further affirms that it can indicate not only variability but also the intensity of WASM rainfall.

Influence of Indian Summer Monsoon on Aerosol Loading in East Asia

2011 ◽  
Vol 50 (3) ◽  
pp. 523-533 ◽  
Author(s):  
Xiaodong Liu ◽  
Libin Yan ◽  
Ping Yang ◽  
Zhi-Yong Yin ◽  
Gerald R. North
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Temporal Variations ◽  
Eastern Asia ◽  
Opposite Pattern ◽  
Aerosol Loading ◽  
Monsoon Index ◽  
Modis Aod ◽  
Meridional Winds ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract The spatial and temporal variations of aerosol loading over eastern Asia specified in terms of the aerosol optical depth (AOD) at the 550-nm wavelength during July are examined in conjunction with the intensity of the Indian summer monsoon. AOD derived from Moderate Resolution Imaging Spectroradiometer (MODIS) observations, gridded reanalyses, and ground-based measurements are used in the analysis. Two contrasting years, 2002 and 2003, which represent weak and active Indian summer monsoon events, respectively, are selected for the study, with a focus on an eastern Asian southern subregion (SR; 23°–32°N, 105°–120°E) and an eastern Asian northern subregion (NR; 35°–44°N, 115°–130°E). It is shown that the interannual variation of July mean wind intensity is a major factor in regulating the midsummer spatial pattern of aerosols over eastern Asia when the Indian monsoon index is anomalously large. The AOD anomalies in the NR and SR are positive and negative, respectively, during an active monsoon year, whereas the opposite is observed during a weak monsoon year. The variation patterns of less cloudy-day visibility, observed at four meteorological stations in the SR and NR subregions, also show spatial–temporal aerosol variability evident in the MODIS AOD data. Relative to the case of a weak monsoon year, meridional winds and convection are stronger and more clouds and precipitation are observed in the NR subregion during the active monsoon year. The opposite pattern is observed in the SR subregion. The spatial–temporal variation pattern of aerosols over eastern Asia illustrates the nonnegligible role of transport and dispersal mechanisms associated with the Indian summer monsoon in the region.

Sign in / Sign up

Export Citation Format

Share Document