D. A. Randall's research while affiliated with University of Colorado Boulder and other places

Publications (25)

Article
A variety of global climate models (GCMs) has been used to examine the Snowball Earth Hypothesis for Neoproterozoic glaciations, often with conflicting results. If such models are to be used to increase theoretical understanding of Neoproterozoic glaciations, the sources of discrepancies among models must be understood. A previous SNOWball Model In...
Article
Several climate models have predicted an increase in long-term droughts in tropical South America due to increased greenhouse gases in the atmosphere. Although the Amazon rainforest is resilient to seasonal drought, multi-year droughts pose a definite problem for the ecosystem's health. Furthermore, drought- stressed vegetation participates in feed...
Article
Full-text available
By reviewing recent observational, numerical, and theoretical studies, progress in understanding the physics of climate change feedbacks is achieved as well as some of the reasons for the intermodel differences. Intermodel differences in cloud feedbacks have been confirmed as the primary source of climate-sensitivity uncertainty, and recent studies...
Article
Full-text available
The Atmospheric Radiation Measurement (ARM) Program's Single Column Model (SCM) working group conducted its intercomparison study of midlatitude summertime continental convection using the July 1995 Intensive Operational Period (IOP) data set (Ghan et al. 2000). Only one cloud-resolving model (CRM) participated in the study. On the other hand, seve...
Article
The Single-Column Model (SCM) Working Group (WC) and the Cloud Working Group (CWG) in the Atmospheric Radiation Measurement (ARM) Program have begun a collaboration with the GEWEX Cloud System Study (GCSS) WGs. The forcing data sets derived from the special ARM radiosonde measurements made during the SCM Intensive Observation Periods (IOPs), the we...
Article
Several one-dimensional (ID) cloud/turbulence ensemble modeling results of an idealized nighttime marine stratocumulus case are compared to large eddy simulation (LES). This type of model intercomparison was one of the objects of the first Global Energy and Water Cycle Experiment Cloud System Study boundary layer modeling workshop held at the Natio...
Article
Implementation of a broadband radiation parameterization in the UCLA cumulus ensemble model (CEM) is discussed in this study, with emphasis on the specific problems associated with adequate calculation of radiative transfer processes in the CEM. The radiation parameterization is based on the Harshvardhan broadband radiative transfer model with clou...
Article
Radiative-convective systems inevitably seek a statistical equilibrium, but there is no reason to believe that this equilibrium must be steady. The obvious temporal variability of convection in na- ture, on many time scales, is dearly linked, at least in part, to forcing by transient large-scale dynam- ical processes (e.g. easterly waves) and trans...
Article
Year 2000 simulations of surface fluxes at the Atmospheric Radiation Measurement Program Southern Great Plains (ARM/SGP) site made with SiB Version 2.5 coupled to the Colorado State University GCM (CSU-BUGS5) in Single Column Mode (SCM) result in a spuriously large Bowen Ratio and anomalously low precipitable water during several periods over the s...
Article
Full-text available
CO 2 transport by synoptic "eddies" strongly amplifies seasonality at high latitudes while damping seasonality at mid-latitudes. In this study, we investigate uncertainty in eddy transport using a global transport model driven by four reanalysis products from the Goddard EOS Data Assimilation System for 2005. We find that upward and poleward transp...

Citations

... These changes have the anthropogenic and natural origins (Qiuhong 2020). The major driving factors for stream flow variability have been widely attributed to climate change and human activities (Jaramillo and Destouni 2015;Piao, et al. 2010;Solomon, et al. 2007;Sun, et al. 2014;Wu, et al. 2018;Zhang, et al. 2015). However, there are many challenges left to be dealt with by scientists in terms of changes in the local stream flow and the effective mechanisms due to the complicated relations between the human activities and climate changes (Chang, et al. 2016;Marhaento, et al. 2018;Tang and Oki 2016). ...
... Dust aerosols directly affect the radiation budget of the Earth system by scattering and absorbing solar radiation. Furthermore, as cloud condensation nuclei, dust also participates in the aerosol-cloud interaction and indirectly affects the climate system [8,9]. Thus, a better provide new levels of capacity for identifying, tracking, and monitoring rapidly changing weather events. ...
... A rationale is that at such resolution we can get rid of some of the parameterizations, for instance of atmospheric convection, to base crucial processes like vertical atmospheric energy transport (see above) on laws of physics instead, and thereby increase the fidelity of the simulations further. Earth's globally averaged surface temperature has already warmed by about 1.1 • C when comparing the average over the years 2011-2020 with a preindustrial reference (1850-1900) [3]. Of course, there is no direct measurement of this quantity but it is derived from the large number of available surface observations which are, however, inhomogeneously distributed. ...
... This uncertainty is largely due to the spread in low-level cloud responses seen across the Global Climate Models (GCMs) participating in the Couple Model Intercomparison Projects phase 3 (CMIP3) and 5 (CMIP5) (Bony and Dufresne, 2005;Webb et al., 2006;Sherwood et al., 2014), and is the main source of the GCMs spread in ECS estimates (2-4.6°C) (Bony et al., 2006;Vial et al., 2013;Caldwell et al., 2016). ...
... New satellite-based observations allow for innovative ways to observe the boundary layer structure. The global boundary layer height (BLH) climatology has been derived by using Global Positioning System radio occultation (GPS-RO) measurements (Ratnam and Basha, 2010;Guo et al., 2011;Ao et al., 2012), the Lidar In-space Technology Experiment (LITE) (Randall et al., 1998), the Geoscience Laser Altimeter System (GLAS) (Palm et al., 2005), and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) (Jordan et al., 2010;Denning, 2012, 2013). GPS-RO provides a valuable global view of heightresolved refractivity or moisture structure of boundary layer, but suffers with very coarse spatial resolutions (200 m in vertical and ∼ 200 km horizontal) and has limited penetration into the lowest 500 m of the atmosphere . ...
... The work of the IPCC is synthesized in Assessment Reports (AR) which are released at regular intervals. The fifth AR [1] indicates the foremost importance of the greenhouse gases and of the aerosols emitted by human activities on the energy budget of the Earth. This budget quantifies the radiative energy reaching the Earth and the outcoming energy. ...
... Therefore, atmospheric water vapour causing the formation of clouds, is a significant component in the hydrological cycle for which more attention is required from researchers in elucidating the meteorological process in the atmosphere (Oltmans and Hoffmann 1995;Houghton et al. 2001;Hoffmann et al. 2005;Deshpande et al. 2010;Unnikrishnan Warrior et al. 2010). The regional scale variation in meteorological parameters are mainly influenced by topography and moisture source (Roderick and Farquhar 2002;Trenberth 2002). Thus, the effect of the regional climate and distribution pattern of moisture on continental areas is being studied to understand the different aspects in meterology. ...
... Optical and micro-physical aerosol properties inferred from AERONET inversion products have been used in this study to incorporate some important information into climate and radiative studies (Dubovik and King, 2000;Dubovik et al., 2006;Boucher et al., 2013). Monthly mean aerosol volume size distributions (dV /dlnR) for background and dust-laden conditions are displayed in Figs. 5 and 7, while monthly mean aerosol volume concentration (VolCon) and effective radius (R eff ) values for the total, fine and coarse modes in addition to the fine-mode fraction (V f /V t ) are presented in Figs. 6 and 8, respectively. ...
... One important component of the measurements at each of these sites is the routine launching of radiosondes two-four times per day, resulting in more than 5000 launches per year. During this period the ARM program has used Vaisala radiosondes as part of regular operations and intensive operational periods (e.g., Ghan et al., 2000;Xu et al., 2002;Xie et al., 2005;Miller et al., 2007;Jensen et al., , 2016. The RS92 radiosonde is the current standard at all of the ARM sites and has been in use since 2005. ...
... They consist of both solar shortwave radiation and infrared longwave radiation. Radiative cooling may influence cloud formation (Lilly, 1988;Xu and Randall, 1995a), convection (Gray and Jacobson, 1977;Fu et al., 1995), surface rainfall (Dudhia, 1989;Xu and Randall, 1995b), relative humidity (Fu et al., 1995;Tao et al., 1996), and precipitable water (Sui et al., 1997(Sui et al., , 1998Gao et al., 2009;Gao and Li, 2010). Heat budget is one of the most important physical constraints in linking radiative cooling to the release of latent heat, sensible heat, and divergence of heat flux. ...