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  • Author or Editor: A. A. Kulkarni x
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S. S. Singh, A. A. Kulkarni, and D. R. Sikka

Abstract

Application of a dynamic initialization scheme for balancing initial wind and pressure fields for a one-level primitive equation model in the Indian region has been investigated. For this purpose, the model equations are integrated forward and backward around the initial time following the Euler backward time-difference scheme without restoration of any variable. For comparison, the initial wind-pressure balance has also been constructed from the observed horizontal motion field by a hierarchy of models of increasing complexity, using the geostrophic relation, the linear balance equation and the nonlinear balance equation. Furthermore, the 48 h forecasts are prepared using the balanced initial data derived from the static nonlinear balance equation and the dynamic initialization scheme. The forecast results from both initialization schemes are compared and discussed. The results obtained from the dynamic initialization scheme are found to be either slightly superior or comparable to those based on the static initialization scheme.

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B. Padma Kumari, S. H. Kulkarni, D. B. Jadhav, A. L. Londhe, and H. K. Trimbake

Abstract

The instrument twilight photometer was designed, developed, and installed at the Indian Institute of Tropical Meteorology (IITM), Pune, India (18°43′N, 73°51′E), to monitor the vertical distribution of atmospheric aerosols. The instrument, based on passive remote sensing technique, is simple and inexpensive. It is operated only during twilights, and the method of retrieval of aerosol profile is based on a simple twilight technique. It functions at a single wavelength (660 nm), and a photomultiplier tube is used as a detector. The amplifier, an important component of the system, was designed and developed by connecting 10 single integrated-circuit (IC) amplifiers in parallel so that the noise at the output is drastically reduced and the sensitivity of the system has been increased. As a result, the vertical profiles are retrieved to a maximum of 120 km. A brief description of the basic principle of twilight technique, the experimental setup, and the method of retrieval of aerosol profiles using the above photometer are detailed in this paper.

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Thara V. Prabha, A. Khain, R. S. Maheshkumar, G. Pandithurai, J. R. Kulkarni, M. Konwar, and B. N. Goswami

Abstract

Analysis of the microphysical structure of deep convective clouds using in situ measurements during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) over the Indian peninsular region is presented. It is shown that droplet size distributions (DSDs) in highly polluted premonsoon clouds are substantially narrower than DSDs in less polluted monsoon clouds. High values of DSD dispersion (0.3–0.6) and its vertical variation in the transient and monsoon clouds are related largely to the existence of small cloud droplets with diameters less than 10 μm, which were found at nearly all levels. This finding indicates the existence of a continuous generation of the smallest droplets at different heights. In some cases this generation of small droplets leads to the formation of bimodal and even multimodal DSDs. The formation of bimodal DSDs is especially pronounced in monsoon clouds. Observational evidence is presented to suggest that in-cloud nucleation at elevated layers is a fundamental mechanism for producing multimodal drop size distribution in monsoon clouds as well as in most deep convective clouds. These findings indicate that inclusion of continued nucleation away from the cloud base into numerical models should be considered to predict microphysics and precipitation of clouds in monsoons and other cloud-related phenomena.

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P. Swapna, M. K. Roxy, K. Aparna, K. Kulkarni, A. G. Prajeesh, K. Ashok, R. Krishnan, S. Moorthi, A. Kumar, and B. N. Goswami

Abstract

With the goal of building an Earth system model appropriate for detection, attribution, and projection of changes in the South Asian monsoon, a state-of-the-art seasonal prediction model, namely the Climate Forecast System version 2 (CFSv2) has been adapted to a climate model suitable for extended climate simulations at the Indian Institute of Tropical Meteorology (IITM), Pune, India. While the CFSv2 model has been skillful in predicting the Indian summer monsoon (ISM) on seasonal time scales, a century-long simulation with it shows biases in the ocean mixed layer, resulting in a 1.5°C cold bias in the global mean surface air temperature, a cold bias in the sea surface temperature (SST), and a cooler-than-observed troposphere. These biases limit the utility of CFSv2 to study climate change issues. To address biases, and to develop an Indian Earth System Model (IITM ESMv1), the ocean component in CFSv2 was replaced at IITM with an improved version, having better physics and interactive ocean biogeochemistry. A 100-yr simulation with the new coupled model (with biogeochemistry switched off) shows substantial improvements, particularly in global mean surface temperature, tropical SST, and mixed layer depth. The model demonstrates fidelity in capturing the dominant modes of climate variability such as the ENSO and Pacific decadal oscillation. The ENSO–ISM teleconnections and the seasonal leads and lags are also well simulated. The model, a successful result of Indo–U.S. collaboration, will contribute to the IPCC’s Sixth Assessment Report (AR6) simulations, a first for India.

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Akshara Kaginalkar, Sachin D. Ghude, U. C. Mohanty, Pradeep Mujumdar, Sudheer Bhakare, Hemant Darbari, Arun K Dwivedi, Pallavi Gavali, Srujan Gavhale, Sahidul Islam, Gouri Kadam, Sumita Kedia, Manoj Khare, Neelesh Kharkar, Santosh H. Kulkarni, Sri Sai Meher, A. K. Nath, Mohamed Niyaz, Sagar Pokale, Vineeth Krishnan Valappil, Sreyashi Debnath, Chinmay Jena, Raghu Nadimpalli, Madhusmita Swain, Saimy Davis, Shubha Avinash, C. Kishtawal, Prashant Gargava, S. D. Attri, and Dev Niyogi

Abstract

Global urban population is projected to double by 2050. This rapid urbanization is the driver of economic growth but has environmental challenges. To that end, there is an urgent need to understand, simulate and disseminate information about extreme events, routine city operations and long term planning decisions.

This paper describes an effort underway in India involving an interdisciplinary community of meteorology, hydrology, air quality, computer science from national and international institutes. The urban Collaboratory is a system of systems for simulating weather, hydrology, air quality, health, energy, transport and economy, and its interactions. Study and prediction of urban events involve multi-scale observations and cross-sector models; heterogeneous data management and enormous computing power. The consortia program (NSM_Urban) is part of ‘weather ready cities’, under the aegis of India’s National Supercomputing Mission.

The ecosystem ‘Urban Environment Science to Society (UES2S)’, builds on the integrated cyberinfrastructure with a science gateway for community research and end-user service with modeling and inter-operable data. The Collaboratory has urban computing, stakeholder participation, and a coordinated means to scaffold projects and ideas into operational tools. It discusses the design and the utilization of the High Performance Computing (HPC) as a science cloud platform for bridging urban environment and data science, participatory stakeholder applications and decision making. The system currently integrates models for high impact urban weather, flooding, air quality, and simulating street and building scale wind flow and dispersion. The program with the work underway is ripe for interfacing with regional and international partners and this paper provides an avenue towards that end.

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