15 research outputs found
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Tracking tropical cloud systems - Observations for the diagnosis of simulations by the Weather Research and Forecasting (WRF) Model
To aid in improving model parameterizations of clouds and convection, we examine the capability of models, using explicit convection, to simulate the life cycle of tropical cloud systems in the vicinity of the ARM Tropical Western Pacific sites. The cloud life cycle is determined using a satellite cloud tracking algorithm (Boer and Ramanathan, 1997), and the statistics are compared to those of simulations using the Weather Research and Forecasting (WRF) Model. Using New York Blue, a Blue Gene/L supercomputer that is co-operated by Brookhaven and Stony Brook, simulations are run at a resolution comparable to the observations. Initial results suggest a computational paradox where, even though the size of the simulated systems are about half of that observed, their longevities are still similar. The explanation for this seeming incongruity will be explored
Structural and functional leaf traits of two Gochnatia species from distinct growth forms in a sclerophyll forest site in Southeastern Brazil
Modifications to the Water Vapor Continuum in the Microwave Suggested by Ground-Based 150-GHz Observations
The role of cloud microphysics parameterization in the simulation of mesoscale convective system clouds and precipitation in the tropical western Pacific
This paper presents a detailed analysis of convection-permitting cloud simulations, aimed at increasing the understanding of the role of parameterized cloud microphysics in the simulation of mesoscale convective systems (MCSs) in the tropical western Pacific (TWP). Simulations with three commonly used bulk microphysics parameterizations with varying complexity have been compared against satellite-retrieved cloud properties. An MCS identification and tracking algorithm was applied to the observations and the simulations to evaluate the number, spatial extent, and microphysical properties of individual cloud systems. Different from many previous studies, these individual cloud systems could be tracked over larger distances because of the large TWP domain studied. The analysis demonstrates that the simulation of MCSs is very sensitive to the parameterization of microphysical processes. The most crucial element was found to be the fall velocity of frozen condensate. Differences in this fall velocity between the experiments were more related to differences in particle number concentrations than to fall speed parameterization. Microphysics schemes that exhibit slow sedimentation rates for ice aloft experience a larger buildup of condensate in the upper troposphere. This leads to more numerous and/or larger MCSs with larger anvils. Mean surface precipitation was found to be overestimated and insensitive to the microphysical schemes employed in this study. In terms of the investigated properties, the performances of complex two-moment schemes were not superior to the simpler one-moment schemes, since explicit prediction of number concentration does not necessarily improve processes such as ice nucleation, the aggregation of ice crystals into snowflakes, and their sedimentation characteristics. © 2013 American Meteorological Society
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Tracking tropical cloud systems for the diagnosis of simulations by the weather research and forecasting (WRF) model
To aid in improving model parameterizations of clouds and convection, we examine the capability of models, using explicit convection, to simulate the life cycle of tropical cloud systems in the tropical warm pool. The cloud life cycle is determined using a satellite cloud tracking algorithm (Boer and Ramanathan, J. Geophys. Res., 1997), and the statistics are compared to those of simulations using the Weather Research and Forecasting (WRF) Model. Using New York Blue, a Blue Gene/L supercomputer that is co-operated by Brookhaven and Stony Brook, simulations are run at a resolution comparable to the observations. Initial results suggest that the organization of the mesoscale convective systems is particularly sensitive to the cloud microphysics parameterization used
Inclined lidar observations of boundary layer aerosol particles above the Kongsfjord, Svalbard
An inclined lidar with vertical resolution of 0.4 m was used for detailed boundary layer studies and to link observations at Zeppelin Mountain (474 m) and Ny-Ă…lesund, Svalbard. We report on the observation of aerosol layers directly above the Kongsfjord. On 29 April 2007, a layer of enhanced backscatter was observed in the lowest 25 m above the open water surface. The low depolarization ratio indicated spherical particles. In the afternoon, this layer disappeared. The ultrafine particle concentration at Zeppelin and Corbel station (close to the Kongsfjord) was low. On 1 May 2007, a drying process in the boundary layer was observed. In the morning, the atmosphere up to Zeppelin Mountain showed enhanced values of the backscatter coefficient. Around noon, the top of the highly reflecting boundary layer decreased from 350 to 250 m. The top of the boundary layer observed by lidar was confirmed by radiosonde data
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RACORO long-term, systematic aircraft observations of boundary layer clouds
Our knowledge of boundary layer cloud processes is insufficient to resolve pressing scientific problems. Boundary layer clouds often have liquid-water paths (LWPs) less than 100 gm{sup 2}, which are defined here as being 'thin' Clouds with Low Optical Water Depths (CLOWD). This type of cloud is common globally, and the Earth's radiative energy balance is particularly sensitive to small changes in their optical properties. However, it is difficult to retrieve accurately their cloud properties via remote sensing because they are tenuous and often occur in partly cloudy skies. This interferes with our ability to obtain the routine, long-term statistics needed to improve their representation in climate models. To address this problem, in-situ data are needed to investigate cloud processes and to evaluate and refine existing retrieval algorithms. Coordinated by the ARM Aerial Facility (AAF), the Routine AAF CLOWD Optical Radiative Observations (RACORO) field campaign conducted long-term, systematic flights in boundary layer, liquid-water clouds over the ARM Southern Great Plains (SGP) site between 22 January and 30 June 2009. This was the first time that a long-term aircraft campaign was undertaken for systematic in-situ sampling of cloud properties. Using the CIRPAS Twin Otter aircraft equipped with a comprehensive set of instruments to measure solar and thermal radiation, cloud microphysics, aerosol properties and atmospheric state, the RACORO team logged an unprecedented 59 flights and 259 research hours above the SGP site. Data gathered during the RACORO campaign will provide researchers with a statistically relevant data set of boundary-layer cloud and aerosol properties for future study. These data can be used to validate retrieval algorithms and support process studies and model simulations of boundary layer clouds and, in particular, CLOWD-type clouds. In addition to cloud observations, complementary clear-sky flight patterns were conducted to map the surface albedo, characterize the aerosol and cloud condensation nuclei, and study boundary layer turbulence. For RACORO to operate as a routine, long-term program, flight operations had to be kept as simple as possible to achieve its objectives, which required an operating paradigm different from typical, short-term, intensive aircraft field programs. This poster summarizes RACORO operations, measurements and instruments