Options
NCAR
4 results
Now showing 1 - 4 of 4
- PublicationOpen AccessSensitivity of Tropical Cyclone Rainfall to Idealized Global Scale Forcings(2014)
; ; ; ; ; ; ; ; ;Villarini, G.; The University of Iowa ;Lavers, D.; The University of Iowa ;Scoccimarro, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Zhao, M.; GFDL ;Wehner, M.; LBNL ;Vecchi, G. A.; GFDL ;Knutson, T. R.; GFDL ;Reed, K.; NCAR; ; ; ; ; ; ; Heavy rainfall and flooding associated with tropical cyclones (TCs) are responsible for a large number of fatalities and economic damage worldwide. Despite their large socio-economic impacts, research into heavy rainfall and flooding associated with TCs has received limited attention to date, and still represents a major challenge. Our capability to adapt to future changes in heavy rainfall and flooding associated with TCs is inextricably linked to and informed by our understanding of the sensitivity of TC rainfall to likely future forcing mechanisms. Here we use a set of idealized high-resolution atmospheric model experiments produced as part of the U.S. CLIVAR Hurricane Working Group activity to examine TC response to idealized global-scale perturbations: the doubling of CO2, uniform 2K increases in global sea surface temperature (SST), and their combined impact. As a preliminary but key step, daily rainfall patterns of composite TCs within climate model outputs are first compared and contrasted to the observational records. To assess similarities and differences across different regions in response to the warming scenarios, analyses are performed at the global and hemispheric scales and in six global TC ocean basins. The results indicate a reduction in TC daily precipitation rates in the doubling CO2 scenario (on the order of 5% globally), and an increase in TC rainfall rates associated with a uniform increase of 2K in SST (both alone and in combination with CO2 doubling; on the order of 10-20% globally).259 325 - PublicationRestrictedHurricanes and climate: the U.S. CLIVAR working group on hurricanes(2015)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Walsh, K. J. E.; University of Melbourne ;Camargo, S. J.; Columbia University ;Vecchi, G. A.; GFDL ;Daloz, A. S.; University of Wisconsin-Madison ;Elsner, J.; Florida State University ;Emanuel, K.; MIT ;Horn, M.; University of Melbourne ;Lim, Y. K.; NASA ;Roberts, M.; Met-Office ;Patricola, C.; Texas A&M University ;Scoccimarro, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Sobel, A.; Columbia University ;Strazzo, S.; Florida State University ;Villarini, G.; IOWA University ;Wehner, M.; Lawrence Berkeley National Laboratory, ;Zhao, M.; GFDL ;Kossin, J. P.; NOAA/NCDC ;Larow, T.; Florida State University ;Oouchi, K.; JAMSTEC ;Shubert, S.; NASA ;Wang, H.; NOAA/NCEP ;Bacmeister, J.; NCAR ;Chang, P.; Texas A&M University ;Chauvin, F.; Meteo-France ;Jablonowski, C.; University of Michigan ;Kumar, A.; NOAA ;Murakami, H.; GFDL ;Ose, T.; MRI/JMA ;Reed, K.; NCAR ;Saravanan, R.; Texas A&M University ;Yamada, Y.; JAMSTEC ;Zarzycki, C. M.; University of Michigan ;Vidale, P. L.; University of Reading ;Jonas, J. A.; Columbia Univeristy ;Henderson, N.; Lamont-Doherty Earth Observatory,; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; While a quantitative climate theory of tropical cyclone formation remains elusive, considerable progress has been made recently in our ability to simulate tropical cyclone climatologies and understand the relationship between climate and tropical cyclone formation. Climate models are now able to simulate a realistic rate of global tropical cyclone formation, although simulation of the Atlantic tropical cyclone climatology remains challenging unless horizontal resolutions finer than 50 km are employed. This article summarizes published research from the idealized experiments of the Hurricane Working Group of U.S. CLIVAR (CLImate VARiability and predictability of the ocean-atmosphere system). This work, combined with results from other model simulations, has strengthened relationships between tropical cyclone formation rates and climate variables such as mid-tropospheric vertical velocity, with decreased climatological vertical velocities leading to decreased tropical cyclone formation. Systematic differences are shown between experiments in which only sea surface temperature is increased versus experiments where only atmospheric carbon dioxide is increased, with the carbon dioxide experiments more likely to demonstrate the decrease in tropical cyclone numbers previously shown to be a common response of climate models in a warmer climate. Experiments where the two effects are combined also show decreases in numbers, but these tend to be less for models that demonstrate a strong tropical cyclone response to increased sea surface temperatures. Further experiments are proposed that may improve our understanding of the relationship between climate and tropical cyclone formation, including experiments with two-way interaction between the ocean and the atmosphere and variations in atmospheric aerosols.246 57 - PublicationRestrictedLayered structures in the upper Ligurian Sea(2010)
; ; ; ; ; ; ;Carniel, S.; CNR-ISMAR ;Kantha, L.; Univ. of Colorado ;Bergamasco, A.; CNR-ISMAR ;Prandke, H.; ISW ;Small, R. J.; NCAR ;Sclavo, M.; CNR-ISMAR; ; ; ; ; During the dedicated sea-truth cruise LIGURE2007, a part of the intensive observational campaign Ligurian Sea Air-Sea Interaction Experiment (LASIE) performed in the eastern Ligurian Sea (Italy) from 16th to 23rd June in 2007, the R/V Urania carried out an intensive microstructure measurement program. Most of these measurements were made between 17th and 20th, in the vicinity of a spar buoy anchored 60 km off the coast in a region with a water column depth of approximately 1500 m; the prevailing light wind conditions and intense solar radiation limited the depth of the upper mixed layer to about 10–15m. We carried out measurements of the structure of the upper water column to a depth exceeding about 200 m. Interestingly, the microstructure measurements revealed multiple layers of relatively elevated dissipation and diffusivity rates around a depth of about 100 m. Since the water column is shown not to be not conducive to double-diffusion, these layered structures must have been produced by small-scale shear due to other processes, such as breaking internal waves. In this paper, we describe the oceanographic conditions prevailing at the time of the measurements, as well as the general turbulent properties in the upper part of the water column. In particular, the layered structures below the mixed layer are discussed in detail, with suggestions as to the likely origin and possible ways of investigating these processes.423 118 - PublicationRestrictedCharacteristics of tropical cyclones in high-resolution 1 models in the present climate(2014-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Shaevitz, D.; Columbia University ;Camargo, S.; Columbia University ;Sobel, A. H.; Columbia University ;Jonas, J.; Columbia Univeristy ;Kim, D.; Columbia Univeristy ;Kumar, A.; NOAA/NWS/NCEP ;LaRow, T.; Florida State University ;Lim, Y.; NASA ;Murakami, H.; University of Hawaii ;Reed, K.; NCAR ;Roberts, M. J.; Met Office ;Scoccimarro, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Vidale, P. L.; Universiy of Reading ;Wang, H.; NOAA/NWS/NCEP ;Wehner, M. F.; University of California ;Zhao, M.; GFDL ;Henderson, N.; Columbia University; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The global characteristics of tropical cyclones (TCs) simulated by several climate models are analyzed and compared with observations. The global climate models were forced by the same sea surface temperature (SST) fields in two types of experiments, using climatological SST and interannually varying SST. TC tracks and intensities are derived from each model's output fields by the group who ran that model, using their own preferred tracking scheme; the study considers the combination of model and tracking scheme as a single modeling system, and compares the properties derived from the different systems. Overall, the observed geographic distribution of global TC frequency was reasonably well reproduced. As expected, with the exception of one model, intensities of the simulated TC were lower than in observations, to a degree that varies considerably across models151 19