scholarly journals Floods and droughts in association with cold and warm ENSO events and related circulation features

MAUSAM ◽  
2021 ◽  
Vol 50 (4) ◽  
pp. 355-364
Author(s):  
MEDHA KHOLE ◽  
U.S DE
Keyword(s):  
Summer Monsoon ◽  
Extreme Event ◽  
Southern Oscillation ◽  
Indian Subcontinent ◽  
Phase Locking ◽  
Regional Scale ◽  
Circulation Pattern ◽  
Enso Events ◽  
Monsoon System ◽  
Floods And Droughts

For the Indian subcontinent. the occurrence of floods and droughts is closely linked with the summer monsoon activity. The phenomenon of El Nino-Southern Oscillation (ENSO) has been established to be one of the major teleconnections of Indian Summer Monsoon. Also the relationship between the circulation features and summer monsoon activity is well documented in the literature. The interaction of F.NSO with monsoon system was known to the seasonal forecasters in India from the days of G. Walker. Northland (1953) summarising these results has remarked that ‘Monsoon has a prolonged influence on the global weather rather than global weather parameters influencing the monsoon’. 1990-94 was a prolonged period of warm ENSO producing weather anomalies in different regions of the globe. Yet during the same period all India rainfall was very close to normal and in fact. 1994 was a year of abundant rainfall for India. The aim of the study is to examine some of these features more critically.   It is observed that ENSO has a modifying effect on the regional scale circulation pattern and possible interactions and/or phase-Locking with the planetary scale circulation pattern. which results into the occurrence or non-occurrence of an extreme event. Also, a qualitative analysis is carried for a period 1960-90 to assess how far the mid-season rainfall deficiency is made up at the end of the season. It is observed that even during drought years, the mid-season rainfall deficiency is made up at the end of the season for a considerable percentage of the total number of cases.

scholarly journals Regional and Local Impacts of the ENSO and IOD Events of 2015 and 2016 on the Indian Summer Monsoon—A Bhutan Case Study

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 954
Author(s):  
Katherine Power ◽  
Josefine Axelsson ◽  
Norbu Wangdi ◽  
Qiong Zhang
Keyword(s):  
Indian Ocean ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
El Niño ◽  
Late Onset ◽  
El Nino ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Local Scale ◽  
The Indian Ocean

The Indian Summer Monsoon (ISM) plays a vital role in the livelihoods and economy of those living on the Indian subcontinent, including the small, mountainous country of Bhutan. The ISM fluctuates over varying temporal scales and its variability is related to many internal and external factors including the El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). In 2015, a Super El Niño occurred in the tropical Pacific alongside a positive IOD in the Indian Ocean and was followed in 2016 by a simultaneous La Niña and negative IOD. These events had worldwide repercussions. However, it is unclear how the ISM was affected during this time, both at a regional scale over the whole ISM area and at a local scale over Bhutan. First, an evaluation of data products comparing ERA5 reanalysis, TRMM and GPM satellite, and GPCC precipitation products against weather station measurements from Bhutan, indicated that ERA5 reanalysis was suitable to investigate ISM change in these two years. The reanalysis datasets showed that there was disruption to the ISM during this period, with a late onset of the monsoon in 2015, a shifted monsoon flow in July 2015 and in August 2016, and a late withdrawal in 2016. However, this resulted in neither a monsoon surplus nor a deficit across both years but instead large spatial-temporal variability. It is possible to attribute some of the regional scale changes to the ENSO and IOD events, but the expected impact of a simultaneous ENSO and IOD events are not recognizable. It is likely that 2015/16 monsoon disruption was driven by a combination of factors alongside ENSO and the IOD, including varying boundary conditions, the Pacific Decadal Oscillation, the Atlantic Multi-decadal Oscillation, and more. At a local scale, the intricate topography and orographic processes ongoing within Bhutan further amplified or dampened the already altered ISM.

scholarly journals Evaluation of the Hydrological Cycle in the ECHAM5 Model

2006 ◽  
Vol 19 (16) ◽  
pp. 3810-3827 ◽  
Author(s):  
Stefan Hagemann ◽  
Klaus Arpe ◽  
Erich Roeckner
Keyword(s):  
General Circulation ◽  
Hydrological Cycle ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Vertical Resolution ◽  
Model Simulations ◽  
Enso Events ◽  
Precipitation Response ◽  
Simulated Precipitation ◽  
The Impact

Abstract This study investigates the impact of model resolution on the hydrological cycle in a suite of model simulations using a new version of the Max Planck Institute for Meteorology atmospheric general circulation model (AGCM). Special attention is paid to the evaluation of precipitation on the regional scale by comparing model simulations with observational data in a number of catchments representing the major river systems on the earth in different climate zones. It is found that an increased vertical resolution, from 19 to 31 atmospheric layers, has a beneficial effect on simulated precipitation with respect to both the annual mean and the annual cycle. On the other hand, the influence of increased horizontal resolution, from T63 to T106, is comparatively small. Most of the improvements at higher vertical resolution, on the scale of a catchment, are due to large-scale moisture transport, whereas the impact of local water recycling through evapotranspiration is somewhat smaller. At high horizontal and vertical resolution (T106L31) the model captures most features of the observed hydrological cycle over land, and also the local and remote precipitation response to El Niño–Southern Oscillation (ENSO) events. Major deficiencies are the overestimation of precipitation over the oceans, especially at higher vertical resolution, along steep mountain slopes and during the Asian summer monsoon season, whereas a dry bias exists over Australia. In addition, the model fails to reproduce the observed precipitation response to ENSO variability in the Indian Ocean and Africa. This might be related to missing coupled air–sea feedbacks in an AGCM forced with observed sea surface temperatures.

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 Prediction of September–December Fire in New Caledonia (Southwestern Pacific) Using July Niño-4 Sea Surface Temperature Index

2013 ◽  
Vol 52 (3) ◽  
pp. 623-633 ◽  
Author(s):  
Vincent Moron ◽  
Renaud Barbero ◽  
Morgan Mangeas ◽  
Laurent Borgniet ◽  
Thomas Curt ◽  
...  
Keyword(s):  
New Caledonia ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Sea Surface ◽  
Small Scale ◽  
Central Pacific ◽  
Climatic Forcing ◽  
Austral Spring ◽  
Burned Areas ◽  
Enso Events

AbstractAn empirical statistical scheme for predicting September–December fires in New Caledonia in the southwestern Pacific Ocean region using a cross-validated generalized linear model has been developed for the 2000–10 period. The predictor employs July sea surface temperatures (SST) recorded over the Niño-4 box (5°S–5°N, 160°–210°E), which are closely related to austral spring (September–November) rainfall anomalies across New Caledonia. The correlation between the logarithm of observed and simulated total burned areas across New Caledonia is 0.87. A decrease in the local-scale skill (median correlation between the log of observed and simulated total burned areas in a 20-km radius around a rain gauge = 0.46) around the main town (Nouméa) and its suburbs in the southwest of Grande Terre, and also in northern New Caledonia, could be associated either with a weaker climatic forcing from the Niño-4 SST index or a small-scale climatic forcing not linearly related to the El Niño–Southern Oscillation (ENSO) phenomenon. It is more likely that the decrease is tied to the influence of human-driven factors that blur the regional-scale climatic signal mostly associated with central Pacific ENSO events.

scholarly journals The Influence of ENSO and MJO on Drought in Different Ecological Geographic Regions in China

2021 ◽  
Vol 13 (5) ◽  
pp. 875
Author(s):  
Lei Zhou ◽  
Siyu Wang ◽  
Mingyi Du ◽  
Qiang Chen ◽  
Congcong He ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Spatial Correlation ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Meteorological Drought ◽  
Agricultural Drought ◽  
Tibet Plateau ◽  
Enso Events ◽  
Geographical Regions ◽  
The Impact

Mastering the spatial and temporal differences of ENSO (EI Niño-Southern Oscillation) and MJO (Madden–Julian Oscillation) and their influence on drought is very important for accurately monitoring and forecasting drought. In this study, spatiotemporal characteristics and variability of the impact of ENSO and MJO on drought were analyzed from the perspectives of meteorological drought and agricultural drought through temporal and spatial correlation analyses of China’s 48 eco-geographical regions. The results show a strong correlation between drought and ENSO and MJO in general. The spatial correlation coefficients are different, and the response of extreme events varies in different regions. The influence of ENSO and MJO on agricultural drought is higher than that on meteorological drought. ENSO and MJO have a considerable influence on agricultural drought in regions such as the Qinghai-Tibet Plateau and Xinjiang, with the highest correlation coefficient of 0.72. A significant influence of ENSO and MJO on meteorological drought was found in the Jiangnan region with the highest correlation coefficient of 0.40. In addition, agricultural drought shows a significant time lag in response to ENSO events. When the lag time is six months, the time series presents the highest correlation coefficient with the mean value of the correlation coefficient reaching 0.38 and the maximum value reaching 0.75. This research is of great significance for understanding the spatiotemporal correlation between climate patterns and drought on a large regional scale and it provides further insights into the teleconnection mechanisms of drought.

scholarly journals Interannual variability of the frequency of MJO phases and its association with two types of ENSO

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Panini Dasgupta ◽  
M. K. Roxy ◽  
Rajib Chattopadhyay ◽  
C. V. Naidu ◽  
Abirlal Metya
Keyword(s):  
Indian Ocean ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Moisture Distribution ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Frequency Pattern ◽  
Enso Events ◽  
Enso Phases

AbstractIn this study, we reexamine the effect of two types of El Niño Southern Oscillation (ENSO) modes on Madden Julian Oscillation (MJO) activity in terms of the frequency of MJO phases. Evaluating all-season data, we identify two dominant zonal patterns of MJO frequency exhibiting prominent interannual variability. These patterns are structurally similar to the Wheeler and Hendon (Mon. Weather Rev. 132:1917–1932, 2004) RMM1 and RMM2 spatial patterns. The first pattern explains a higher frequency of MJO activity over the Maritime Continent and a lower frequency over the central Pacific Ocean and the western Indian Ocean, or vice versa. The second pattern is associated with a higher frequency of MJO active days over the eastern Indian Ocean and a lower frequency over the western Pacific, or vice versa. We find that these two types of MJO frequency patterns are related to the central Pacific and eastern Pacific ENSO modes. From the positive to the negative ENSO (central Pacific or eastern Pacific) phases, the respective MJO frequency patterns change their sign. The MJO frequency patterns are the lag response of the underlying ocean state. The coupling between ocean and atmosphere is exceedingly complex. The first MJO frequency pattern is most prominent during the negative central-Pacific (CP-type) ENSO phases (specifically during September–November and December-February seasons). The second MJO frequency pattern is most evident during the positive eastern-Pacific (EP-type) ENSO phases (specifically during March–May, June–August and September–November). Different zonal circulation patterns during CP-type and EP-type ENSO phases alter the mean moisture distribution throughout the tropics. The horizontal convergence of mean background moisture through intraseasonal winds are responsible for the MJO frequency anomalies during the two types of ENSO phases. The results here show how the MJO activity gets modulated on a regional scale in the presence of two types of ENSO events and can be useful in anticipating the seasonal MJO conditions from a predicted ENSO state.

scholarly journals Climatology and Interannual Variability of Quasi-Global Intense Precipitation Using Satellite Observations

2016 ◽  
Vol 29 (15) ◽  
pp. 5447-5468 ◽  
Author(s):  
Martina Ricko ◽  
Robert F. Adler ◽  
George J. Huffman
Keyword(s):  
Daily Precipitation ◽  
Southern Oscillation ◽  
Regional Scale ◽  
Tropical Rainfall Measuring Mission ◽  
Spatial And Temporal Variation ◽  
Intense Rainfall ◽  
Precipitation Regime ◽  
Enso Events ◽  
Intense Precipitation ◽  
The One

Abstract Climatology and variations of recent mean and intense precipitation over a near-global (50°S–50°N) domain on a monthly and annual time scale are analyzed. Data used to derive daily precipitation to examine the effects of spatial and temporal coverage of intense precipitation are from the current Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) 3B42 version 7 precipitation product, with high spatial and temporal resolution during 1998–2013. Intense precipitation is defined by several different parameters, such as a 95th percentile threshold of daily precipitation, a mean precipitation that exceeds that percentile, or a fixed threshold of daily precipitation value (e.g., 25 and 50 mm day−1). All parameters are used to identify the main characteristics of spatial and temporal variation of intense precipitation. High correlations between examined parameters are observed, especially between climatological monthly mean precipitation and intense precipitation, over both tropical land and ocean. Among the various parameters examined, the one best characterizing intense rainfall is a fraction of daily precipitation ≥ 25 mm day−1, defined as a ratio between the intense precipitation above the used threshold and mean precipitation. Regions that experience an increase in mean precipitation likely experience a similar increase in intense precipitation, especially during the El Niño–Southern Oscillation (ENSO) events. Improved knowledge of this intense precipitation regime and its strong connection to mean precipitation given by the fraction parameter can be used for monitoring of intense rainfall and its intensity on a global to regional scale.

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