Intraseasonal and Seasonally Persisting Patterns of Indian Monsoon Rainfall

2007 ◽  
Vol 20 (1) ◽  
pp. 3-20 ◽  
Author(s):  
V. Krishnamurthy ◽  
J. Shukla
Keyword(s):  
Monsoon Rainfall ◽  
Indian Monsoon ◽  
Singular Spectrum Analysis ◽  
Daily Rainfall ◽  
Central India ◽  
North India ◽  
Peninsular India ◽  
Rainfall Analysis ◽  
Intraseasonal Oscillations ◽  
Rainfall Anomalies

Abstract The space–time structure of the active and break periods of the Indian monsoon has been studied using 70-yr-long high-resolution gridded daily rainfall data over India. The analysis of lagged composites of rainfall anomalies based on an objective categorization of active and break phases shows that the active (break) cycle, with an average life of 16 days, starts with positive (negative) rainfall anomalies over the Western Ghats and eastern part of central India and intensifies and expands to a region covering central India and parts of north India during the peak phase, while negative (positive) anomalies cover the sub-Himalayan region and southeast India. During the final stage of the active (break) period, the positive (negative) rainfall anomalies move toward the foothills of the Himalayas while peninsular India is covered with opposite sign anomalies. The number of days on which lows and depressions are present in the region during active and break periods is consistent with the rainfall analysis. The number of depressions during the active phase is about 7 times that during the break phase. Using multichannel singular spectrum analysis of the daily rainfall anomalies, the seasonal monsoon rainfall is found to consist of two dominant intraseasonal oscillations with periods of 45 and 20 days and three seasonally persisting components. The 45- and 20-day oscillations are manifestations of the active and break periods but contribute very little to the seasonal mean rainfall. The seasonally persisting components with anomalies of the same sign, and covering all of India, have a very high interannual correlation with the total seasonal mean rainfall. These results support a conceptual model of the interannual variability of the monsoon rainfall consisting of seasonal mean components and a statistical average of the intraseasonal variations. The success in the prediction of seasonal mean rainfall depends on the relative strengths of the seasonally persisting components and intraseasonal oscillations.

scholarly journals The Identity and Distribution of Striped Bagrid Catfish, Mystus Tengara (Hamilton 1822) Revealed Through Integrative Taxonomy

2021 ◽  
Author(s):  
Sangeetha Nair ◽  
Kavita Kumari ◽  
Pavan Kumar ◽  
Rajeev Raghavan ◽  
Ashok Jaiswar
Keyword(s):  
Genetic Distance ◽  
Geographical Location ◽  
Taxonomic Status ◽  
Central India ◽  
Type Locality ◽  
North India ◽  
Morphometric Traits ◽  
Peninsular India ◽  
North East ◽  
Taxonomic Approach

Abstract In the present study, an integrated taxonomic approach has been applied to clarify the taxonomic status, identity and distribution of bagrid catfish, Mystus tengara. Comparative morphometric evaluation of M. tengara identified in the present study from distant geographical location revealed variations of the traits in response to body length and environment, without significant genetic distance. The observed morphometric traits of M. tengara were found to be overlapping with available morphometric traits of M. tengara, M. carcio and M. vittatus. Maximum likelihood phylogenetic analysis based on mitochondrial cytochrome c oxidase (COI) gene also could not resolve their identity, and five paraphyletic clades comprising of M. tengara, M. vittatus and M. carcio from India, Nepal and Bangladeshwere observed. Morphological and genetic evidence along withcomparative evaluation of M. tengara, from its type locality, we consider M. tengara identified in the present study to be true, with its distribution extending from North East India to West Bengal, North India, Central India, Northern peninsular India and Bangladesh. The observation of paraphyletic subclade and evaluation of genetic distance between subclades reveals, there could be at least four cryptic species in this group. Further confirmation on the identity of M. vittatus and M. carcio, by integrated taxonomic approach based on fresh specimens collected from type locality, is required.

scholarly journals The Effect of Soil Moisture Perturbations on Indian Monsoon Depressions in a Numerical Weather Prediction Model

2017 ◽  
Vol 30 (21) ◽  
pp. 8811-8823 ◽  
Author(s):  
Kieran M. R. Hunt ◽  
Andrew G. Turner
Keyword(s):  
Soil Moisture ◽  
Indian Monsoon ◽  
Monsoon Season ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Numerical Weather Prediction Model ◽  
North India ◽  
Peninsular India ◽  
Monsoon Depressions

Indian monsoon depressions (MDs) are synoptic-scale cyclonic systems that propagate across peninsular India three or four times per monsoon season. They are responsible for the majority of rainfall in agrarian north India, so constraining precipitation estimates is of high importance. Here, a case study from August 2014 is used to explore the relationship between varying soil moisture and the resulting track and structure of an incident MD using the Met Office Unified Model. This case study is chosen with the view to increasing understanding of the general impact of soil moisture perturbations on monsoon depressions. It is found that increasing soil moisture in the monsoon trough region results in deeper inland penetration and a more developed structure—for example, a warmer core in the midtroposphere and a stronger bimodal potential vorticity core in the mid-to-lower troposphere—with more precipitation, and a structure that in general more closely resembles that found in depressions over the ocean, indicating that soil moisture may enhance the convective mechanism that drives depressions over land. This experiment also shows that these changes are most significant when the depression is deep and negligible when it is weakening. Increasing soil moisture in the sub-Himalayan arable zone, a region with large irrigation coverage, also caused deeper inland penetration and some feature enhancement in the upper troposphere, but no significant changes were found in the track heading or lower-tropospheric structure.

scholarly journals Regional Simulation of Indian summer Monsoon Intraseasonal Oscillations at Gray Zone Resolution

2017 ◽  
Author(s):  
Xingchao Chen ◽  
Olivier M. Pauluis ◽  
Fuqing Zhang
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Monsoon Rainfall ◽  
Deep Convection ◽  
Wrf Model ◽  
Central India ◽  
Horizontal Resolution ◽  
Cumulus Parameterization ◽  
Gray Zone ◽  
Intraseasonal Oscillations

Abstract. Simulations of the Indian summer monsoon by cloud-permitting WRF model at gray zone resolution are described in this study, with a particular emphasis on the model ability to capture the Monsoon Intraseasonal Oscillations (MISO). Five boreal summers are simulated from 2007 to 2011 using the ERA-Interim reanalysis as lateral boundary forcing data. Our experimental set-up relies on a high horizontal resolution of 9 km to capture deep convection without the use of a cumulus parameterization. When compared to simulations with coarser grid spacing (27-km) and using the cumulus scheme, our approach results in a reduction of the biases in mean precipitation and in more realistic reproduction of the low frequency variability associated with MISO. Results show that the model at gray zone resolution captures the fundamental features of the summer monsoon. The spatial distributions and temporal evolutions of monsoon rainfall in WRF simulations are verified qualitatively well against observations from the Tropical Rainfall Measurement Mission (TRMM), with regional maxima located over West Ghats, central India, Himalaya foothills and the west coast of Myanmar. The onset, breaks and withdrawal of the summer monsoon in each year are also realistically captured by the model. MISO phase composites of monsoon rainfall, low-level wind and precipitable water anomalies in the simulations are compared qualitatively with the observations. Both the simulations and observations show a northeastward propagation of the MISO, with the intensification and weakening of Somali Jet over the Arabian Sea during the active and break phases of the Indian summer monsoon.

scholarly journals Regional simulation of Indian summer monsoon intraseasonal oscillations at gray-zone resolution

2018 ◽  
Vol 18 (2) ◽  
pp. 1003-1022 ◽  
Author(s):  
Xingchao Chen ◽  
Olivier M. Pauluis ◽  
Fuqing Zhang
Keyword(s):  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Monsoon Rainfall ◽  
Deep Convection ◽  
Wrf Model ◽  
Central India ◽  
Precipitable Water ◽  
Gray Zone ◽  
Grid Spacing ◽  
Intraseasonal Oscillations

Abstract. Simulations of the Indian summer monsoon by the cloud-permitting Weather Research and Forecasting (WRF) model at gray-zone resolution are described in this study, with a particular emphasis on the model ability to capture the monsoon intraseasonal oscillations  (MISOs). Five boreal summers are simulated from 2007 to 2011 using the ERA-Interim reanalysis as the lateral boundary forcing data. Our experimental setup relies on a horizontal grid spacing of 9 km to explicitly simulate deep convection without the use of cumulus parameterizations. When compared to simulations with coarser grid spacing (27 km) and using a cumulus scheme, the 9 km simulations reduce the biases in mean precipitation and produce more realistic low-frequency variability associated with MISOs. Results show that the model at the 9 km gray-zone resolution captures the salient features of the summer monsoon. The spatial distributions and temporal evolutions of monsoon rainfall in the WRF simulations verify qualitatively well against observations from the Tropical Rainfall Measurement Mission (TRMM), with regional maxima located over Western Ghats, central India, Himalaya foothills, and the west coast of Myanmar. The onset, breaks, and withdrawal of the summer monsoon in each year are also realistically captured by the model. The MISO-phase composites of monsoon rainfall, low-level wind, and precipitable water anomalies in the simulations also agree qualitatively with the observations. Both the simulations and observations show a northeastward propagation of the MISOs, with the intensification and weakening of the Somali Jet over the Arabian Sea during the active and break phases of the Indian summer monsoon.

scholarly journals Composite Structure of Monsoon Low Pressure Systems and Its Relation to Indian Rainfall

2010 ◽  
Vol 23 (16) ◽  
pp. 4285-4305 ◽  
Author(s):  
V. Krishnamurthy ◽  
R. S. Ajayamohan
Keyword(s):  
Monsoon Rainfall ◽  
Total Duration ◽  
Daily Rainfall ◽  
Central India ◽  
Low Pressure ◽  
Rainfall Pattern ◽  
Indian Rainfall ◽  
Northwest India ◽  
Monsoon Winds ◽  
Low Pressure Systems

Abstract The tropical disturbances formed in the Bay of Bengal and the Arabian Sea and over land points in central India, known as low pressure systems (LPSs), are shown to contribute significantly to the seasonal monsoon rainfall over India. Analyses of daily rainfall over India and statistics of the LPSs for the period of 1901–2003 show that the rainfall pattern when the LPSs are present captures the most dominant daily rainfall pattern that represents the active monsoon phase. The rainfall pattern when the LPSs are absent is similar to the pattern representing the break monsoon phase. The location, number, and duration of the LPSs are found to be closely related to the phases and propagation of the dominant intraseasonal modes of the Indian rainfall. The LPSs are also associated with the strengthening of the monsoon trough and low-level monsoon winds. The number of LPSs and their total duration and the corresponding rainfall during July and August exceed those in June and September. The LPS tracks reach up to northwest India during flood years, whereas they are confined to central India during drought years. However, the contribution of rainfall during the LPSs to the total seasonal rainfall is same during flood or drought years. Although the LPSs seem to play an important role in the monsoon rainfall, they alone may not determine the interannual variability of the seasonal mean monsoon rainfall.

scholarly journals Coherent response of the Indian Monsoon Rainfall to Atlantic Multi-decadal Variability over the last 2000 years

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Pothuri Divakar Naidu ◽  
Raja Ganeshram ◽  
Massimo A. Bollasina ◽  
Champoungam Panmei ◽  
Dirk Nürnberg ◽  
...  
Keyword(s):  
Monsoon Rainfall ◽  
Indian Monsoon ◽  
Decadal Variability ◽  
Indian Monsoon Rainfall

On the Predictability of Northeast Monsoon Rainfall over South Peninsular India in General Circulation Models

2013 ◽  
Vol 170 (11) ◽  
pp. 1945-1967 ◽  
Author(s):  
Archana Nair ◽  
Nachiketa Acharya ◽  
Ankita Singh ◽  
U. C. Mohanty ◽  
T. C. Panda
Keyword(s):  
General Circulation ◽  
Monsoon Rainfall ◽  
General Circulation Models ◽  
Northeast Monsoon ◽  
Peninsular India ◽  
Northeast Monsoon Rainfall
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