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Verlinde, Johannes

Publications and source records attributed to Verlinde, Johannes.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) (Field Campaign Report)

The Arctic is rapidly changing, and these changes have substantial societal relevance. First, arctic change is a leading sign of global change, as the warming observed in the Arctic is 2-3 times faster than observed across the rest of the globe. This so-called arctic amplification is due to numerous feedbacks, including those linked to the declining sea ice. Broad arctic changes are also hypothesized to be related to shifts in large-scale circulation patterns that may have implications for mid-latitude weather and ocean circulation. Arctic change is further affecting the oceans through acidification that threatens food supplies. Declining sea ice also opens the Arctic for new resource development, shipping routes, tourism, and other commercial activities. Lastly, the changing Arctic is a hotbed for geopolitical challenges as nations vie for influence and control of this resource-rich and newly accessible region. Clearly the Arctic and its changes are playing a huge role in our Earth both from a geophysical and socio-political standpoint. To navigate, manage, and respond to the challenges associated with arctic change requires a vastly improved understanding of the coupled arctic system, and the drivers and implications of these changes. It is essential to better understand the physical basis for why the arctic sea ice is declining, the associated feedbacks that work to amplify or modulate this decline, and the myriad ways that the Earth system is responding. As a result of these changes and uncertainties, there are increasing societal needs for improved model predictive skill in the Arctic, to address pressing gaps in global climate prediction, to advance forecast skills for regional and hemispheric weather and sea ice, and to ensure robust ecosystem models that realistically link physical and biological systems. To fulfill these core needs requires new, sophisticated, and cross-cutting observations within the rapidly changing arctic ice pack.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Habit–Dependent Vapor Growth Modulates Arctic Supercooled Water Occurrence

We present an analysis of long-term data collected at Utqiagvik, Alaska, to explore the impacts of cloud processes on the probability of finding supercooled water given cloud temperature, P(L|T), in the topmost unseeded liquid-bearing layers. P(L|T) has local minima at temperatures around –6°C and –15°C. Simulations using habit-evolving ice microphysics models suggest that these minima are the result of efficient vapor growth by non-isometric habits found at these temperatures. Here, we conclude that habit-dependent vapor growth of ice crystals modulates the macrophysical occurrence of supercooled water in polar clouds, the effect of which should be included in model parametrizations to avoid biases and/or error compensation. Our methodology is adaptable for spherical ice treatments implemented in models (example parametrizations provided), amenable for use with satellite measurements to give global impartial observational targets for model evaluations, and may allow empirical characterization of bulk responses to seeding and possibly secondary ice effects.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

AWARE: The Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment

The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) performed comprehensive meteorological and aerosol measurements and ground-based atmospheric remote sensing at two Antarctic stations using the most advanced instrumentation available. A suite of cloud research radars, lidars, spectral and broadband radiometers, aerosol chemical and microphysical sampling equipment, and meteorological instrumentation was deployed at McMurdo Station on Ross Island from December 2015 through December 2016. A smaller suite of radiometers and meteorological equipment, including radiosondes optimized for surface energy budget measurement, was deployed on the West Antarctic Ice Sheet between 4 December 2015 and 17 January 2016. AWARE provided Antarctic atmospheric data comparable to several well-instrumented high Arctic sites that have operated for many years and that reveal numerous contrasts with the Arctic in aerosol and cloud microphysical properties. These include persistent differences in liquid cloud occurrence, cloud height, and cloud thickness. Antarctic aerosol properties are also quite different from the Arctic in both seasonal cycle and composition, due to the continent’s isolation from lower latitudes by Southern Ocean storm tracks. Antarctic aerosol number and mass concentrations are not only non-negligible but perhaps play a more important role than previously recognized because of the higher sensitivities of clouds at the very low concentrations caused by the large-scale dynamical isolation. Antarctic aerosol chemical composition, particularly organic components, has implications for local cloud microphysics. The AWARE dataset, fully available online in the ARM Program data archive, offers numerous case studies for unique and rigorous evaluation of mixed-phase cloud parameterization in climate models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Arctic Cloud Microphysical Processes. Final report

The primary goal of our team’s effort under this grant was to quantify Arctic lower-troposphere processes by tying data from the large suite of NSA instruments to modeling efforts indirectly through data assimilation and directly through remote sensing and cloud modeling efforts. We maintained a distinct focus on how the ARM measurements may be used evaluate model simulations and/or physical processes. We will separate this report into two distinct sections: our data assimilation effort and the use of NSA instruments to improve our understanding and modeling of model physics to better characterize the critical surface energy budget in polar regimes.

58 GEOSCIENCES↗
NASA NTRS2002

Tropical Convection's Roles in Tropical Tropopause Cirrus

The results presented here show that tropical convection plays a role in each of the three primary processes involved in the in situ formation of tropopause cirrus. First, tropical convection transports moisture from the surface into the upper troposphere. Second, tropical convection excites Rossby waves that transport zonal momentum toward the ITCZ, thereby generating rising motion near the equator. This rising motion helps transport moisture from where it is detrained from convection to the cold-point tropopause. Finally, tropical convection excites vertically propagating tropical waves (e.g. Kelvin waves) that provide one source of large-scale cooling near the cold-point tropopause, leading to tropopause cirrus formation.

Boehm, Matthew T.↗
NASA NTRS2002

Tropical Convection's Roles in Tropical Tropopause Cirrus

Remote sensing observations reveal the frequent occurrence of tropopause cirrus, thin cirrus layers located near the tropical cold-point tropopause. Here, we present a theory in which tropical convection plays several important roles in tropopause cirrus formation. First, tropical convection is the primary means by which the moisture required for tropopause cirrus formation is transported into the upper troposphere. However, previous studies suggest that this convection rarely penetrates to the altitudes at which tropopause cirrus layers are observed, suggesting that additional vertical moisture transport is required to explain tropopause cirrus formation. We propose a mechanism for explaining this transport in which tropical convection plays the key role. According to this hypothesis, the transport is accomplished by meridional circulations that develop within the tropopause transition layer (TTL) in response to momentum transport by Rossby waves generated by tropical convection. Results of a series of global scale model runs designed to test this hypothesis will be presented. In addition, reanalyses vertical velocity data will be examined for evidence of the expected correlation between large-scale rising motion within the TTL and tropical convection. Once moisture is present near the cold-point tropopause, large-scale cooling is required to initiate tropopause cirrus formation. One source of this cooling is stratospheric tropical waves induced by tropical convection, as we will show using a time series of radiosonde temperature data superimposed with data on cloud occurrence from the DOE ARM Nauru99 field experiment. Observations of the global characteristics of these waves from a longer time series of reanalysis data will also be presented.

Boehm, Matthew T.↗