Ambarish Karmalkar

University of Massachusetts Amherst, Department of Geoscience, Adjunct

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EDUCATION:
Ph.D., Geosciences, 2010, University of Massachusetts Amherst
M.S., Astronomy, 2005, University of Massachusetts Amherst
M.Sc., Physics, 2001, University of Mumbai, India

PREVIOUS RESEARCH APPOINTMENTS:
Scientist, Met Office Hadley Centre, UK, Mar 2012 – Feb 2015
Postdoctoral Researcher, University of Oxford, UK, Sep 2010 – Feb 2012

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Papers by Ambarish Karmalkar

Finding plausible and diverse variants of a climate model. Part II: development and validation of methodology

Climate Dynamics, 2019

Interpreting Results from the NARCCAP and NA-CORDEX Ensembles in the Context of Uncertainty in Regional Climate Change Projections

Bulletin of the American Meteorological Society, 2018

Identifying credible and diverse GCMs for regional climate change studies—case study: Northeastern United States

Climatic Change, 2019

Consequences of Global Warming of 1.5 ˚C and 2 ˚C for Regional Temperature and Precipitation Changes in the Contiguous United States

The differential warming of land and ocean leads to many continental regions in the Northern Hemi... more The differential warming of land and ocean leads to many continental regions in the Northern Hemisphere warming at rates higher than the global mean temperature. Adaptation and conservation efforts will, therefore, benefit from understanding regional consequences of limiting the global mean temperature increase to well below 2˚C above pre-industrial levels, a limit agreed upon at the United Nations Climate Summit in Paris in December 2015. Here, we analyze climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to determine the timing and magnitude of regional temperature and precipitation changes across the contiguous United States (US) for global warming of 1.5 and 2˚C and highlight consensus and uncertainties in model projections and their implications for making decisions. The regional warming rates differ considerably across the contiguous US, but all regions are projected to reach 2˚C about 10-20 years before the global mean temperature. Although there is uncertainty in the timing of exactly when the 1.5 and 2˚C thresholds will be crossed regionally, over 80% of the models project at least 2˚C warming by 2050 for all regions for the high emissions scenario. This threshold-based approach also highlights regional variations in the rate of warming across the US. The fastest warming region in the contiguous US is the Northeast, which is projected to warm by 3˚C when global warming reaches 2˚C. The signal-to-noise ratio calculations indicate that the regional warming estimates remain outside the envelope of uncertainty throughout the twenty-first century, making them potentially useful to planners. The regional precipitation projections for global warming of 1.5˚C and 2˚C are uncertain, but the eastern US is projected to experience wetter winters and the Great Plains and the Northwest US are projected to experience drier summers in the future. The impact of different scenarios on regional precipitation projections is negligible throughout the twenty-first century compared to uncertainties associated with internal variability and model diversity.

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Cloud liquid water path and radiative feedbacks over the Southern Ocean

by Ambarish Karmalkar and M. Ringer

Climate models show a robust shortwave negative feedback in the midlatitude oceans in climate cha... more Climate models show a robust shortwave negative feedback in the midlatitude oceans in climate change simulations. This feedback is commonly attributed to an increase in cloud optical depth due to ice to liquid phase change as the climate warms. Here we use a cyclone compositing technique to show that the models' cloud liquid water path (LWP) response is strongly dependent on cloud regime. The radiative and LWP responses are not as tightly coupled as a zonal-mean analysis would suggest, implying that the physical mechanisms that control the overall LWP response are not necessarily responsible for the radiative response. The area of the cyclone dominated by low-level stratiform and shallow convective clouds plays a dominant role in the radiative response. Since these are mostly supercooled liquid clouds, the strength of a negative cloud phase feedback in the real world should be smaller than the one predicted by current models.

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A review of observed and projected changes in climate for the islands in the Caribbean

Atmósfera, 2013

ABSTRACT Observed and projected changes in climate have serious socio-economic implications for t... more ABSTRACT Observed and projected changes in climate have serious socio-economic implications for the Caribbean islands. This article attempts to present basic climate change information—based on previous studies, available observations and climate model simulations—at spatial scales relevant for islands in the Caribbean. We use the General Circulation Model (GCM) data included in the Coupled Model Intercomparison Project phase 3 (CMIP3) and the UK Hadley Centre regional climate model (RCM) data to provide both present-day and scenario-based future information on precipitation and temperature for individual island states. Gridded station observations and satellite data are used to study 20th century climate and to assess the performance of climate models. With main focus on precipitation, we also discuss factors such as sea surface temperature, sea level pressure and winds that affect seasonal variations in precipitation. The CMIP3 ensemble mean and the RCM successfully capture the large-scale atmospheric circulation features in the region, but show difficulty in capturing the characteristic bimodal seasonal cycle of precipitation. Future drying during the wet season in this region under climate change scenarios has been noted in previous studies, but the magnitude of change is highly uncertain in both GCM and RCM simulations. The projected decrease is more prominent in the early wet season erasing the mid-summer drought feature in the western Caribbean. The RCM simulations show improvements over the GCM mainly due to better representation of landmass, but its performance is critically dependent on the driving GCM. This study highlights the need for high-resolution observations and ensemble of climate model simulations to fully understand climate change and its impacts on small islands in the Caribbean.

High resolution stalagmite climate record from the Yucatan Peninsula spanning the Maya terminal classic period

Keywords: stalagmite stable isotopes Maya drought rainfall Yucatan

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Climate change in Central America and Mexico: regional climate model validation and climate change projections

by Raymond Bradley and Ambarish Karmalkar

Climate Dynamics - CLIM DYNAM, 2011

Central America has high biodiversity, it harbors high-value ecosystems and it’s important to pro... more Central America has high biodiversity, it harbors high-value ecosystems and it’s important to provide regional climate change information to assist in adaptation and mitigation work in the region. Here we study climate change projections for Central America and Mexico using a regional climate model. The model evaluation shows its success in simulating spatial and temporal variability of temperature and precipitation and also in capturing regional climate features such as the bimodal annual cycle of precipitation and the Caribbean low-level jet. A variety of climate regimes within the model domain are also better identified in the regional model simulation due to improved resolution of topographic features. Although, the model suffers from large precipitation biases, it shows improvements over the coarse-resolution driving model in simulating precipitation amounts. The model shows a dry bias in the wet season and a wet bias in the dry season suggesting that it’s unable to capture the...

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Climate change scenario for Costa Rican montane forests

Geophysical Research Letters, 2008

1] Tropical montane cloud forests are characterized by persistent immersion in clouds, an importa... more 1] Tropical montane cloud forests are characterized by persistent immersion in clouds, an important source of moisture during the dry season. Future changes in temperature and precipitation could alter cloud cover at the vegetation level and seriously affect mountain ecosystems. A regional climate modeling study that focuses on changes in the distributions of temperature and precipitation in Costa Rica shows, in general, an increase in temperature and a decrease in precipitation under the A2 scenario. At high elevations, warming is amplified and future temperature distribution lies outside the range of present-day distribution. Compared to the Caribbean side, temperature changes are greater at high elevations on the Pacific side. Model results also show significant changes in precipitation amounts and variability and an increase in the altitude of cloud formation on the Pacific side that may have serious implications for mountain ecosystems in and around Costa Rica. Citation: Karmalkar, A. V., R. S. Bradley, and H. F. Diaz (2008), Climate change scenario for Costa Rican montane forests, Geophys. Res. Lett., 35, L11702,

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Climate change in Central America and Mexico: regional climate model validation and climate change projections

Climate Dynamics, 2011

Central America has high biodiversity, it harbors high-value ecosystems and it's important to pro... more Central America has high biodiversity, it harbors high-value ecosystems and it's important to provide regional climate change information to assist in adaptation and mitigation work in the region. Here we study climate change projections for Central America and Mexico using a regional climate model. The model evaluation shows its success in simulating spatial and temporal variability of temperature and precipitation and also in capturing regional climate features such as the bimodal annual cycle of precipitation and the Caribbean low-level jet. A variety of climate regimes within the model domain are also better identified in the regional model simulation due to improved resolution of topographic features. Although, the model suffers from large precipitation biases, it shows improvements over the coarse-resolution driving model in simulating precipitation amounts. The model shows a dry bias in the wet season and a wet bias in the dry season suggesting that it's unable to capture the full range of precipitation variability. Projected warming under the A2 scenario is higher in the wet season than that in the dry season with the Yucatan Peninsula experiencing highest warming. A large reduction in precipitation in the wet season is projected for the region, whereas parts of Central America that receive a considerable amount of moisture in the form of orographic precipitation show significant decreases in precipitation in the dry season. Projected climatic changes can have detrimental impacts on biodiversity as they are spatially similar, but far greater in magnitude, than those observed during the El Niño events in recent decades that adversely affected species in the region.

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Finding plausible and diverse variants of a climate model. Part II: development and validation of methodology

Climate Dynamics, 2019