• Pankaj Kumar

      Articles written in Journal of Earth System Science

    • Impact of modified soil thermal characteristic on the simulated monsoon climate over south Asia

      Pankaj Kumar Ralf Podzun Stefan Hagemann Daniela Jacob

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      In the present study, the influence of soil thermal characteristics (STC) on the simulated monsoon climate over south Asia is analyzed. The study was motivated by a common warm temperature bias over the plains of northern India that has been noticed in several global and regional climate models. To address this warm bias and its relation to STC, two sensitivity experiments have been performed with the regional climate model REMO of the Max Planck Institute for Meteorology. The control experiment uses the standard soil thermal characteristic of the model that corresponds to a moist soil. The second experiment uses modified STC that characterize a dry soil, which is more representative of the considered region, as a large part of the region has arid, semi-arid or subtropical summer wet conditions. Both experiments were conducted over 20 years using re-analysis data as lateral boundary conditions. Results show that using the modified STC the predominant regional warm bias has reduced substantially, leading to a better and more realistic surface temperature compared to observations over south Asia. Although, the magnitude of bias has reduced, the warm bias still exists over the region suggesting that other atmospheric and land surface processes also play a role, such as aerosols and irrigation. These need to be addressed adequately in future modeling studies over the region.

    • Understanding drought dynamics and variability over Bundelkhand region

      MD SAQUIB SAHARWARDI ALAM SHWETA MAHADEO PANKAJ KUMAR

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      This study provides an evaluation of the past, present, and future spatiotemporal variability of droughts in the Bundelkhand region of central India. The assessment has been made by analyzing the existing (1951–2018) drought dynamics with gridded observational and reanalysis datasets. The future projection is presented using a multi-model ensemble from 21 simulations of regional climate model over CORDEX South-Asia domain under the highest carbon concentration, i.e., RCP8.5 emission scenario. The Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) indices are used for short and long-term monitoring of droughts. Spatiotemporal statistical analysis is performed to examine the relationship between drought indices, i.e., SPI, SPEI and driving parameters such as temperature, precipitation, etc. It is noticed that the frequency of drought has increased since the beginning of the 21st century. In particular, the northern part of the Bundelkhand region is more vulnerable to drought due to overall less precipitation and more temperature. The composite analysis of drought year indicates that moisture-laden wind from the Arabian Sea branch generally weakened in monsoon season. Teleconnections of drought over Bundelkhand region reveal that nearly 40% of the droughts are linked to El-Nino events that have become stronger in recent decades. The model ensemble realistically represents the regional climate reasonably well over the region. The projected change in near future drought shows more frequent events using both SPI and SPEI indices that are also detected in the observational analysis.

      $\bf{Highlights}$

      $\bullet$ The Northern region of Bundelkhand is more prone to drought due to high temperature and low precipitation.

      $\bullet$ The region receives most of its precipitation from Arabian Sea branch of monsoon winds that generally weakened in drought composite years.

      $\bullet$ About 40% of drought variability is teleconnected with El–Nino years that has become more stronger in recent decades

      $\bullet$ The ensemble of RCM simulations over CORDEX South–Asian domain indicates that the drought events are projected to be more frequent in near future.

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