Chattopadhyay Rajib

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  • Article
    Ocean observations to improve our understanding, modeling, and forecasting of subseasonal-to-seasonal variability
    (Frontiers Media, 2019-08-08) Subramanian, Aneesh C. ; Balmaseda, Magdalena A. ; Centurioni, Luca R. ; Chattopadhyay, Rajib ; Cornuelle, Bruce D. ; DeMott, Charlotte ; Flatau, Maria ; Fujii, Yosuke ; Giglio, Donata ; Gille, Sarah T. ; Hamill, Thomas M. ; Hendon, Harry ; Hoteit, Ibrahim ; Kumar, Arun ; Lee, Jae-Hak ; Lucas, Andrew J. ; Mahadevan, Amala ; Matsueda, Mio ; Nam, SungHyun ; Paturi, Shastri ; Penny, Stephen G. ; Rydbeck, Adam ; Sun, Rui ; Takaya, Yuhei ; Tandon, Amit ; Todd, Robert E. ; Vitart, Frederic ; Yuan, Dongliang ; Zhang, Chidong
    Subseasonal-to-seasonal (S2S) forecasts have the potential to provide advance information about weather and climate events. The high heat capacity of water means that the subsurface ocean stores and re-releases heat (and other properties) and is an important source of information for S2S forecasts. However, the subsurface ocean is challenging to observe, because it cannot be measured by satellite. Subsurface ocean observing systems relevant for understanding, modeling, and forecasting on S2S timescales will continue to evolve with the improvement in technological capabilities. The community must focus on designing and implementing low-cost, high-value surface and subsurface ocean observations, and developing forecasting system capable of extracting their observation potential in forecast applications. S2S forecasts will benefit significantly from higher spatio-temporal resolution data in regions that are sources of predictability on these timescales (coastal, tropical, and polar regions). While ENSO has been a driving force for the design of the current observing system, the subseasonal time scales present new observational requirements. Advanced observation technologies such as autonomous surface and subsurface profiling devices as well as satellites that observe the ocean-atmosphere interface simultaneously can lead to breakthroughs in coupled data assimilation (CDA) and coupled initialization for S2S forecasts. These observational platforms should also be tested and evaluated in ocean observation sensitivity experiments with current and future generation CDA and S2S prediction systems. Investments in the new ocean observations as well as model and DA system developments can lead to substantial returns on cost savings from disaster mitigation as well as socio–economic decisions that use S2S forecast information.
  • Article
    Bay of Bengal intraseasonal oscillations and the 2018 monsoon onset
    (American Meteorological Society, 2021-10-01) Shroyer, Emily L. ; Tandon, Amit ; Sengupta, Debasis ; Fernando, Harindra J. S. ; Lucas, Andrew J. ; Farrar, J. Thomas ; Chattopadhyay, Rajib ; de Szoeke, Simon P. ; Flatau, Maria ; Rydbeck, Adam ; Wijesekera, Hemantha W. ; McPhaden, Michael J. ; Seo, Hyodae ; Subramanian, Aneesh C. ; Venkatesan, Ramasamy ; Joseph, Jossia K. ; Ramsundaram, S. ; Gordon, Arnold L. ; Bohman, Shannon M. ; Pérez, Jaynise ; Simoes-Sousa, Iury T. ; Jayne, Steven R. ; Todd, Robert E. ; Bhat, G. S. ; Lankhorst, Matthias ; Schlosser, Tamara L. ; Adams, Katherine ; Jinadasa, S. U. P. ; Mathur, Manikandan ; Mohapatra, Mrutyunjay ; Rama Rao, E. Pattabhi ; Sahai, Atul Kumar ; Sharma, Rashmi ; Lee, Craig ; Rainville, Luc ; Cherian, Deepak A. ; Cullen, Kerstin ; Centurioni, Luca R. ; Hormann, Verena ; MacKinnon, Jennifer A. ; Send, Uwe ; Anutaliya, Arachaporn ; Waterhouse, Amy F. ; Black, Garrett S. ; Dehart, Jeremy A. ; Woods, Kaitlyn M. ; Creegan, Edward ; Levy, Gad ; Kantha, Lakshmi ; Subrahmanyam, Bulusu
    In the Bay of Bengal, the warm, dry boreal spring concludes with the onset of the summer monsoon and accompanying southwesterly winds, heavy rains, and variable air–sea fluxes. Here, we summarize the 2018 monsoon onset using observations collected through the multinational Monsoon Intraseasonal Oscillations in the Bay of Bengal (MISO-BoB) program between the United States, India, and Sri Lanka. MISO-BoB aims to improve understanding of monsoon intraseasonal variability, and the 2018 field effort captured the coupled air–sea response during a transition from active-to-break conditions in the central BoB. The active phase of the ∼20-day research cruise was characterized by warm sea surface temperature (SST > 30°C), cold atmospheric outflows with intermittent heavy rainfall, and increasing winds (from 2 to 15 m s−1). Accumulated rainfall exceeded 200 mm with 90% of precipitation occurring during the first week. The following break period was both dry and clear, with persistent 10–12 m s−1 wind and evaporation of 0.2 mm h−1. The evolving environmental state included a deepening ocean mixed layer (from ∼20 to 50 m), cooling SST (by ∼1°C), and warming/drying of the lower to midtroposphere. Local atmospheric development was consistent with phasing of the large-scale intraseasonal oscillation. The upper ocean stores significant heat in the BoB, enough to maintain SST above 29°C despite cooling by surface fluxes and ocean mixing. Comparison with reanalysis indicates biases in air–sea fluxes, which may be related to overly cool prescribed SST. Resolution of such biases offers a path toward improved forecasting of transition periods in the monsoon.