Bhardwaj, A., & Misra, V. (2019). Monitoring the Indian Summer Monsoon Evolution at the Granularity of the Indian Meteorological Sub-divisions using Remotely Sensed Rainfall Products. Remote Sensing , 11 (9), 1080.
Abstract: We make use of satellite-based rainfall products from the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) to objectively define local onset and demise of the Indian Summer Monsoon (ISM) at the spatial resolution of the meteorological subdivisions defined by the Indian Meteorological Department (IMD). These meteorological sub-divisions are the operational spatial scales for official forecasts issued by the IMD. Therefore, there is a direct practical utility to target these spatial scales for monitoring the evolution of the ISM. We find that the diagnosis of the climatological onset and demise dates and its variations from the TMPA product is quite similar to the rain gauge based analysis of the IMD, despite the differences in the duration of the two datasets. This study shows that the onset date variations of the ISM have a significant impact on the variations of the seasonal length and seasonal rainfall anomalies in many of the meteorological sub-divisions: for example, the early or later onset of the ISM is associated with longer and wetter or shorter and drier ISM seasons, respectively. It is shown that TMPA dataset (and therefore its follow up Global Precipitation Measurement (GPM) Integrated Multi-satellite Retrievals for GPM (IMERG)) could be usefully adopted for monitoring the onset of the ISM and therefore extend its use to anticipate the potential anomalies of the seasonal length and seasonal rainfall anomalies of the ISM in many of the Indian meteorological sub-divisions. View Full-Text
Karmakar, N., & Misra, V. (2019). The Relation of Intraseasonal Variations With Local Onset and Demise of the Indian Summer Monsoon. J. Geophys. Res. Atmos. , 124 (5), 2483–2506.
Abstract: Two of the most important hydroclimatic features of the Indian Summer Monsoon (ISM) rainfall are its onset/demise and Intraseasonal Oscillations (ISOs) manifested by the active‐break cycles. In this study, we aim to understand the quantitative association between these two phenomena. An objective definition of local onset/demise of the ISM based on more than a century‐long India Meteorological Department (IMD) rain‐gauge observation is taken into consideration. Using multichannel singular spectrum analysis (MSSA) we isolate northward propagating low‐ (20–60 days; LF‐ISO) and northwestward propagating high‐ (10–20 days; HF‐ISO) frequency ISOs from the daily ISM rainfall. Our results suggest that a large number of local onset (59%) and demise (62%) events occur during positive developing phases and positive decaying phases of two ISOs, respectively, with phase‐locking between LF‐ISO and HF‐ISO being particularly important. Local onset is largely associated with favorable phases of ISOs across India except for LF‐ISO over eastern India and HF‐ISO over western Ghats and central India (CI). We find that local demise is more coherent with the ISO phases, especially with HF‐ISO across the domain. We performed a case study to understand large‐scale association with the onset of the ISM over CI. In 44 of total 58 cases (1948–2005), when CI onset occurred during favorable LF‐ISO or HF‐ISO phase, they are either linked with a northward propagation of convection from the equator in LF‐ISO timescale (28 cases) or westward propagating structures from the western Pacific in HF‐ISO timescale (27 cases).
Glazer, R. H., & Misra, V. (2018). Ice versus liquid water saturation in simulations of the Indian summer monsoon. Climate Dynamics , .
Misra, V., Bhardwaj, A., & Mishra, A. (2018). Local onset and demise of the Indian summer monsoon. Climate Dynamics , 51 (5-6), 1609–1622.
Abstract: This paper introduces an objective definition of local onset and demise of the Indian summer monsoon (ISM) at the native grid of the Indian Meteorological Department's rainfall analysis based on more than 100 years of rain gauge observations. The variability of the local onset/demise of the ISM is shown to be closely associated with the All India averaged rainfall onset/demise. This association is consistent with the corresponding evolution of the slow large-scale reversals of upper air and ocean variables that raise the hope of predictability of local onset and demise of the ISM. The local onset/demise of the ISM also show robust internannual variations associated with El Nino and the Southern Oscillation and Indian Ocean dipole mode. It is also shown that the early monsoon rains over northeast India has a predictive potential for the following seasonal anomalies of rainfall and seasonal length of the monsoon over rest of India.
Ali, M., Singh, N., Kumar, M., Zheng, Y., Bourassa, M., Kishtawal, C., et al. (2018). Dominant Modes of Upper Ocean Heat Content in the North Indian Ocean. Climate , 6 (3), 71.
Abstract: The thermal energy needed for the development of hurricanes and monsoons as well as any prolonged marine weather event comes from layers in the upper oceans, not just from the thin layer represented by sea surface temperature alone. Ocean layers have different modes of thermal energy variability because of the different time scales of ocean-atmosphere interaction. Although many previous studies have focused on the influence of upper ocean heat content (OHC) on tropical cyclones and monsoons, no study thus farparticularly in the North Indian Ocean (NIO)has specifically concluded the types of dominant modes in different layers of the ocean. In this study, we examined the dominant modes of variability of OHC of seven layers in the NIO during 1998-2014. We conclude that the thermal variability in the top 50 m of the ocean had statistically significant semiannual and annual modes of variability, while the deeper layers had the annual mode alone. Time series of OHC for the top four layers were analyzed separately for the NIO, Arabian Sea, and Bay of Bengal. For the surface to 50 m layer, the lowest and the highest values of OHC were present in January and May every year, respectively, which was mainly caused by the solar radiation cycle.
Pantina, P. (2010). Characterizing the Variability of the Indian Monsoon: Changes in Evaporative Sources for Summertime Rainfall Events . Master's thesis, Florida State University, Tallahassee, FL.
Abstract: This study focuses on the interannual and intraseasonal variability of evaporative sources for rainfall events during the Indian monsoon. The monsoon is an important part of the economy and lifestyle in India, thus, any improvements in our understanding of its mechanisms would be directly beneficial to society. We first discuss the use of evaporative sources for rainfall events as an important tool to help increase our knowledge of the variations of the monsoon. We then outline the variability of the monsoon on an interannual (wet and dry years) and intraseasonal (active and break periods) time scale. We use three reanalyses (NCEP-R2, CFSR, and MERRA) and an IMD gridded rainfall dataset to trace the location and strength of evaporative sources via a quasi-isentropic back trajectory program. The program uses reanalysis winds and evaporation, among other parameters, to estimate these sources back in time. We discuss the differences in parameters between the datasets on a seasonal, interannual, and intraseasonal time scale. We then thoroughly investigate the strength and location of evaporative sources between datasets on interannual and intraseasonal time scales, and we attempt to explain the variations by analyzing the differences in the input parameters and circulation mechanisms themselves. The study finds that the evaporative sources for given interannual or intraseasonal rainfall events do vary in strength and location. Interannually, the strongest change in evaporative source occurs over central India and the Arabian Sea, suggesting that the overall monsoon flow contributes moisture for Indian rainfall on this time scale. Intraseasonally, the strongest change in evaporative source occurs over the Bay of Bengal, suggesting that low pressure systems contribute moisture for Indian rainfall on this time scale. All three reanalyses yield similar fields of evaporative source. We conclude that accurate prediction of the Indian monsoon requires improved understanding of both interannual and intraseasonal oscillations since the sources of moisture for these events are unique.
Banks, R. (2006). Variability of Indian Ocean Surface Fluxes Using a New Objective Method . Master's thesis, Florida State University, Tallahassee, FL.
Abstract: A new objective technique is used to analyze monthly mean gridded fields of air and sea temperature, scalar and vector wind, specific humidity, sensible and latent heat flux, and wind stress over the Indian Ocean. A variational method produces a 1°x1° gridded product of surface turbulent fluxes and the variables needed to calculate these fluxes. The surface turbulent fluxes are forced to be physically consistent with the other variables. The variational method incorporates a state of the art flux model, which should reduce regional biases in heat and moisture fluxes. The time period is January 1982 to December 2003. The wind vectors are validated through comparison to monthly scatterometer winds. Empirical orthogonal function (EOF) analyses of the annual cycle emphasize significant modes of variability in the Indian Ocean. The dominant monsoon reversal and its connection with the southeast trades are linked in eigenmodes one and two of the surface fluxes. The third eigenmode of latent and sensible heat flux reveal a structure similar to the Indian Ocean Dipole (IOD) mode. The variability in surface fluxes associated with the monsoons and IOD are discussed. September-October-November composites of the surface fluxes during the 1997 positive IOD event and the 1983 negative IOD event are examined. The composites illustrate characteristics of fluxes during different IOD phases.
Krishnamurti, T. N., Kumar, V., Simon, A., Thomas, A., Bhardwaj, A., Das, S., et al. (2017). March of buoyancy elements during extreme rainfall over India. Clim Dyn , 48 (5-6), 1931–1951.
Misra, V., & Li, H. (2014). The seasonal predictability of the Asian summer monsoon in a two-tiered forecast system. Clim Dyn , 42 (9-10), 2491–2507.
Krishnamurthy, V., & Misra, V. (2011). Daily atmospheric variability in the South American monsoon system. Clim Dyn , 37 (3-4), 803–819.