8 research outputs found
Observations of Stratocumulus Clouds and Their Effect on the Eastern Pacific Surface Heat Budget along 20°S
This is the publisher's version, also available electronically from http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00618.1.Widespread stratocumulus clouds were observed on nine transects from seven research cruises to the southeastern tropical Pacific Ocean along 20°S, 75°â85°W in OctoberâNovember of 2001â08. The nine transects sample a unique combination of synoptic and interannual variability affecting the clouds; their ensemble diagnoses longitudeâvertical sections of the atmosphere, diurnal cycles of cloud properties and drizzle statistics, and the effect of stratocumulus clouds on surface radiation. Mean cloud fraction was 0.88, and 67% of 10-min overhead cloud fraction observations were overcast. Clouds cleared in the afternoon [1500 local time (LT)] to a minimum of fraction of 0.7. Precipitation radar found strong drizzle with reflectivity above 40 dBZ.
Cloud-base (CB) heights rise with longitude from 1.0 km at 75°W to 1.2 km at 85°W in the mean, but the slope varies from cruise to cruise. CBâlifting condensation level (LCL) displacement, a measure of decoupling, increases westward. At night CBâLCL is 0â200 m and increases 400 m from dawn to 1600 LT, before collapsing in the evening.
Despite zonal gradients in boundary layer and cloud vertical structure, surface radiation and cloud radiative forcing are relatively uniform in longitude. When present, clouds reduce solar radiation by 160 W mâ2 and radiate 70 W mâ2 more downward longwave radiation than clear skies. Coupled Model Intercomparison Project phase 3 (CMIP3) simulations of the climate of the twentieth century show 40 ± 20 W mâ2 too little net cloud radiative cooling at the surface. Simulated clouds have correct radiative forcing when present, but models have ~50% too few clouds
Weather Sensitive High Spatio-Temporal Resolution Transportation Electric Load Profiles For Multiple Decarbonization Pathways
Electrification of transport compounded with climate change will transform
hourly load profiles and their response to weather. Power system operators and
EV charging stakeholders require such high-resolution load profiles for their
planning studies. However, such profiles accounting whole transportation sector
is lacking. Thus, we present a novel approach to generating hourly electric
load profiles that considers charging strategies and evolving sensitivity to
temperature. The approach consists of downscaling annual state-scale sectoral
load projections from the multi-sectoral Global Change Analysis Model (GCAM)
into hourly electric load profiles leveraging high resolution climate and
population datasets. Profiles are developed and evaluated at the Balancing
Authority scale, with a 5-year increment until 2050 over the Western U.S.
Interconnect for multiple decarbonization pathways and climate scenarios. The
datasets are readily available for production cost model analysis. Our open
source approach is transferable to other regions
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Mechanisms of convective cloud organization by cold pools over tropical warm ocean during the AMIE/DYNAMO field campaign
This paper investigates the mechanisms of convective cloud organization by precipitation-driven cold pools over the warm tropical Indian Ocean during the 2011 Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation (MJO) Investigation Experiment/Dynamics of the MJO (AMIE/DYNAMO) field campaign. A high-resolution regional model simulation is performed using the Weather Research and Forecasting model during the transition from suppressed to active phases of the November 2011 MJO. The simulated cold pool lifetimes, spatial extent, and thermodynamic properties agree well with the radar and ship-borne observations from the field campaign. The thermodynamic and dynamic structures of the outflow boundaries of isolated and intersecting cold pools in the simulation and the associated secondary cloud populations are examined. Intersecting cold pools last more than twice as long, are twice as large, 41% more intense (measured with buoyancy), and 62% deeper than isolated cold pools. Consequently, intersecting cold pools trigger 73% more convection than do isolated ones. This is due to stronger outflows that enhance secondary updraft velocities by up to 45%. However, cold pool-triggered convective clouds grow into deep convection not because of the stronger secondary updrafts at cloud base, but rather due to closer spacing (aggregation) between clouds and larger cloud clusters that form along the cold pool boundaries when they intersect. The close spacing of large clouds moistens the local environment and reduces entrainment drying, increasing the probability that the clouds further develop into deep convection. Implications for the design of future convective parameterization with cold pool-modulated entrainment rates are discussed.The DYNAMO field campaign data used in this paper is available at NCAR's Earth Observing Laboratory's DYNAMO Data Catalogue https://www.eol.ucar.edu/field_projects/dynamo. The data set names are: R/V Roger Revelle Flux, Near-Surface Meteorology, and Navigation Data and S-PolKa Radar, fully corrected, merged, final moments data in cfRadial format
Multisector Dynamics: Advancing the Science of Complex Adaptive Human-Earth Systems
The field of MultiSector Dynamics (MSD) explores the dynamics and co-evolutionary pathways of human and Earth systems with a focus on critical goods, services, and amenities delivered to people through interdependent sectors. This commentary lays out core definitions and concepts, identifies MSD science questions in the context of the current state of knowledge, and describes ongoing activities to expand capacities for open science, leverage revolutions in data and computing, and grow and diversify the MSD workforce. Central to our vision is the ambition of advancing the next generation of complex adaptive human-Earth systems science to better address interconnected risks, increase resilience, and improve sustainability. This will require convergent research and the integration of ideas and methods from multiple disciplines. Understanding the tradeoffs, synergies, and complexities that exist in coupled human-Earth systems is particularly important in the context of energy transitions and increased future shocks
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Near-Surface Density Currents Observed in the Southeast Pacific Stratocumulus-Topped Marine Boundary Layer
Density currents (i.e., cold pools or outflows) beneath marine stratocumulus clouds are characterized using 30 days of ship-based observations obtained during the 2008 Variability of American Monsoon Systems (VAMOS) OceanâCloudâAtmosphereâLand Study Regional Experiment (VOCALS-REx) in the southeast Pacific. An air density increase criterion applied to the Improved Meteorological (IMET) sensor data identified 71 density current front, core (peak density), and tail (dissipating) zones. The similarity in speeds of the mean density current propagation speed (1.8 m sâ»Âč) and the mean cloud-level advection relative to the surface layer wind (1.9 m sâ»Âč) allowed drizzle cells to deposit elongated density currents in their wakes. Scanning Doppler lidar captured prefrontal updrafts with a mean intensity of 0.91 m sâ»Âč and an average vertical extent of 800 m. Updrafts were often surmounted by low-lying shelf clouds not connected to the overlying stratocumulus cloud. The observed density currents were 5â10 times thinner and weaker than typical continental thunderstorm cold pools. Nearly 90% of density currents were identified when C-band radar estimated areal average rain rates exceeded 1 mm dayâ»Âč over a 30-km diameter. Rather than peaking when rain rates were highest overnight, density current occurrence peaks between 0600 and 0800 local solar time when enhanced local drizzle co-occurred with shallow subcloud dry and stable layers. The dry layers may have contributed to density current formation by enhancing subcloud evaporation of drizzle. Density currents preferentially occurred in a large region of predominantly open cells but also occurred in regions of closed cells.This is the publisherâs final pdf. The published article is copyrighted by American Meteorological Society and can be found at: https://www2.ametsoc.org/ams/index.cfm/publications/journals/monthly-weather-review/Keywords: Density currents, Boundary layer, Drizzle, In situ atmospheric observations, Lidars/Lidar observations, Subtropic
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The impact of the diurnal cycle on the propagation of MaddenâJulian Oscillation convection across the Maritime Continent
Influences of the diurnal cycle on the propagation of the MaddenâJulian Oscillation (MJO) convection across the Maritime Continent (MC) are examined using cloudâpermitting regional model simulations and observations. A pair of ensembles of control (CONTROL) and noâdiurnal cycle (NODC) simulations of the November 2011 MJO episode are performed. In the CONTROL simulations, the MJO signal is weakened as it propagates across the MC, with much of the convection stalling over the large islands of Sumatra and Borneo. In the NODC simulations, where the incoming shortwave radiation at the top of the atmosphere is maintained at its daily mean value, the MJO convection signal propagating across the MC is enhanced. Examination of the surface energy fluxes in the simulations indicates that the surface downwelling shortwave radiation is larger in the presence of the diurnal cycle (CONTROL simulations) primarily because clouds preferentially form in the afternoon and are smaller during day time in comparison to nighttime. Furthermore, the diurnal covariability of surface wind speed and skin temperature results in a larger sensible heat flux and a cooler land surface in the CONTROL runs compared to NODC runs. An analysis of observations indicates that ahead of and behind the MJO active phase, the diurnal cycle of cloudiness enhances downwelling shortwave radiation and hence convection over the MC islands. This enhanced stationary convection competes with and disrupts the convective signal of MJO events that propagate over the waters surrounding the islands.
Key Points:
The diurnal cycle disrupts MJO propagation across the Maritime Continent
It enhances downwelling radiation and precipitation over the MC islands
It however has a net cooling effect on the MC land surface