http://www.gfdl.noaa.gov/index/news-app Research highlights from www.gfdl.noaa.gov en 2012-05-16T07:31:19-04:00 hourly 1 1970-01-01T00:00+00:00 http://www.gfdl.noaa.gov/index/news-app/story.58/title.21st-century-projections-of-north-atlantic-tropical-storms-from-cmip5-models North Atlantic tropical storms (TS) are a major climate hazard to North America, and have exhibited variability and change on decadal timescales. Therefore, understanding and predicting future decadal TS activity on decadal timescales is central to NOAA's mission and highly relevant to society. Climate Change Variability and Prediction 2012-05-14 http://www.gfdl.noaa.gov/index/news-app/story.61/title.tropical-tropospheric-only-responses-to-absorbing-aerosols An ongoing challenge in quantifying aerosols’ impact on the climate is determining an optimal way of calculating aerosols’ radiative forcing. For absorbing aerosols, in particular, studies have shown that a forcing calculation that does not include the tropospheric response to absorbing aerosol (instantaneous forcing) is a poor proxy for the change in global mean surface temperature caused by the aerosol. Atmospheric Physics Chemistry and Climate 2012-05-04 http://www.gfdl.noaa.gov/index/news-app/story.60/title.comparing-global-atmospheric-model-simulations-of-tropical-convection An intercomparison of global atmospheric model simulations of tropical convection has been presented and evaluated with available observations collected during the TWP-ICE field experiment. Short simulations initialized from the ECMWF analysis have been used to constrain model large-scale states and thus isolate model systematic biases originating from various physical parameterizations. With realistic thermodynamic and kinematic fields captured in various weather regimes (wet, dry, and break), model precipitation, cloud properties (LWC, IWC, cloud fraction), radiation, and vertical heating profiles respond accordingly in these regimes. Despite somewhat realistically simulated precipitation, there are substantial cloud property discrepancies among the models, which are mainly influenced by cloud and convective parameterizations. Atmospheric Physics Chemistry and Climate 2012-04-27 http://www.gfdl.noaa.gov/index/news-app/story.57/title.some-counter-intuitive-dependencies-of-tropical-cyclone-frequency-on-parameters-in-a-gcm High resolution global atmospheric models are becoming more credible tools for studying the effects of global warming on tropical cyclones, and we need to understand how those aspects of the models in which we have relatively low confidence affect the simulations. The goal of this research was to systematically explore and understand how some key parameters in this global atmospheric model affect the simulation of tropical cyclone frequency. Weather and Atmospheric Dynamics 2012-04-20 http://www.gfdl.noaa.gov/index/news-app/story.56/title.using-relative-humidity-as-a-state-variable-in-climate-feedback-analysis We often use feedback terminology to help us understand why models differ in their estimates of the magnitude of the surface temperature changes produced by a given change in the Earth's energy balance, such as that due to an increase in carbon dioxide. But several lines of evidence have suggested that the methodology used to define these feedbacks is far from optimal, making the typical model's behavior look more complicated than it really is. Our goal in this short note was to propose an alternative methodology that simplifies the analysis in several ways. Weather and Atmospheric Dynamics 2012-04-13 http://www.gfdl.noaa.gov/index/news-app/story.55/title.an-overview-of-cmip5-and-the-experiment-design The fifth phase of the Coupled Model Intercomparison Project (CMIP5) will produce a coordinated multi-model dataset that is designed to advance our knowledge of climate variability and climate change. Researchers worldwide will analyze the model output and produce results that will underlie the forthcoming IPCC Fifth Assessment Report. Unprecedented in scale, CMIP5 has attracted participation from all major climate modeling groups. Building on previous CMIP efforts, CMIP5 includes "long-term" simulations of 20th century climate and projections for the 21st century and beyond. Climate and Ecosystems 2012-04-06 http://www.gfdl.noaa.gov/index/news-app/story.54/title.reducing-uncertainty-in-understanding-ocean-oxygen-and-nitrogen-cycles Oxygen minimum zones (OMZs) exclude many classes of the biological community and are major sites of fixed nitrogen removal from the open ocean. Previous estimates of rate of fixed nitrogen loss through denitrification in the pelagic ocean and in sediments have been unable to match estimates of the supply of fixed nitrogen via N2 fixation, rivers, and atmospheric deposition. This has led some scientists to the conclusion that the global ocean nitrogen cycle is out of balance, and the oceans are accumulating fixed nitrogen. Atmospheric Physics Chemistry and Climate 2012-03-29 http://www.gfdl.noaa.gov/index/news-app/story.52/title.a-model-study-of-heat-waves-over-north-america-meteorological-aspects-and-projections-for-the-21st-century The goal of this research is to evaluate the fidelity of GFDL climate models in reproducing the characteristics of summertime heat waves in North America, and to examine the model-projected changes of these characteristics in the 21st century. Heat waves in North America precipitate a substantial number of human casualties and huge economic costs. Understanding of the processes contributing to heat waves, and projecting changes in them in the 21st century, are an integral part of the NOAA mission to provide scientific information on the present and future states of the climate system. Climate Diagnostics 2012-03-12 http://www.gfdl.noaa.gov/index/news-app/story.53/title.transport-of-asian-ozone-pollution-into-surface-air-over-the-western-united-states-in-spring As Asian countries develop, they are emitting more ozone precursors that pollute surface level air. Many studies have documented this pollution being carried by air currents to the western United States. To determine the extent to which this pollution is affecting air quality in the western U.S., We analyzed balloon soundings, aircraft, surface and satellite measurements from May through June 2010 using a new global high-resolution chemistry-climate model. Our findings indicate that Asian pollution contributes as much as 20 percent of total ozone during springtime pollution episodes in western U.S. surface air. Atmospheric Physics Chemistry and Climate 2012-02-24 http://www.gfdl.noaa.gov/index/news-app/story.51/title.will-open-ocean-oxygen-stress-intensify-under-climate-change- Ten percent of today’s ocean volume is characterized by low level of dissolved oxygen similar to those found in the well-known "dead zones" in the Gulf of Mexico with 35% of global surface waters overlying at least some of this "hypoxia". Under global warming, higher temperatures would be expected to directly lower oxygen concentrations and enhanced stratification to reduce the flow of well-ventilated surface waters to the interior. Under such circumstances, it has been hypothesized that the open-ocean dead zones could greatly expand and indeed changes in low-oxygen waters have been invoked as evidence of climate change. Climate and Ecosystems 2012-02-14 http://www.gfdl.noaa.gov/index/news-app/story.50/title.using-relative-humidity-as-a-state-variable-in-climate-feedback-analysis We often use feedback terminology to help us understand why models differ in their estimates of the magnitude of the surface temperature changes produced by a given change in the Earth's energy balance -- such as that due to an increase in carbon dioxide. But a variety of lines of evidence have suggested that the methodology used to define these feedbacks is far from optimal, making the typical model's behavior look more complicated than it really is. Our goal in this short note was to propose an alternative methodology that simplifies the analysis in several ways. Weather and Atmospheric Dynamics 2012-02-08 http://www.gfdl.noaa.gov/index/news-app/story.49/title.the-future-of-hurricane-activity-why-models-differ-among-themselves One aspect of uncertainty in future projections of basin-wide hurricane activities stems from the variety of projections of the spatial pattern of tropical warming. A tropical cyclone permitting high-resolution, global atmospheric model is used to explore hurricane frequency response to sea surface temperature (SST) anomalies generated by coupled models for the late 21st century using the SRES A1B scenario. Weather and Atmospheric Dynamics 2012-02-03 http://www.gfdl.noaa.gov/index/news-app/story.48/title.pathways-between-primary-production-and-fisheries-yields-of-large-marine-ecosystems There is considerable uncertainty in projections of the impact of climate on fisheries yields due to uncertainties in climate change impacts on primary production and the processes controlling how much primary production is transferred to fish. Primary production and proxies such as chlorophyll have proven to be useful predictors of fisheries yields at regional scales but show much less skill when applied globally. The marine food web dynamics that control the transfer of energy from phytoplankton to fish are complex and it has been postulated that the relationship between primary production and fisheries production may differ dramatically between ecosystems due to changes in planktonic foodweb structure. Climate and Ecosystems 2012-01-24 http://www.gfdl.noaa.gov/index/news-app/story.30/title.anthropogenic-aerosols-and-the-weakening-of-the-south-asian-summer-monsoon An important part of the global water cycle, the South Asian summer monsoon provides about 80% of the region’s annual precipitation, and touches the lives of more than 20% of the world’s population. Using the NOAA/GFDL state-of-the-art global climate model that accounts for all the known natural and anthropogenic forcings, we have investigated what caused the observed decrease in the South Asian summer monsoon rainfall over the second half of the 20th century. Was the widespread drying due to natural factors or human activities? Atmospheric Physics Chemistry and Climate 2011-09-29 http://www.gfdl.noaa.gov/index/news-app/story.26/title.climatological-characteristics-of-arctic-and-antarctic-surface-based-inversions Surface-based inversions (SBI) are frequent features of the Arctic and Antarctic atmospheric boundary layer and influence important climate processes. However, prior to this study, climatological polar SBI properties had not been fully characterized, nor had climate model simulations of SBIs been compared comprehensively to observations. Atmospheric Physics Chemistry and Climate 2011-09-12 http://www.gfdl.noaa.gov/index/news-app/story.27/title.different-magnitudes-of-projected-subsurface-ocean-warming-around-greenland-and-antarctica Recent acceleration of Greenland and Antarctic outlet glaciers and ice flows is closely linked to ocean warming, especially in the subsurface layer. This land ice melt will cause sea level rise. Climate and Ecosystems 2011-07-03 http://www.gfdl.noaa.gov/index/news-app/story.33/title.sensitivity-of-the-aerosol-indirect-effect-to-subgrid-variability-in-the-cloud-parame The recently developed GFDL AM3 model (Donner et. al 2011) incorporates a prognostic treatment of cloud drop number to simulate the aerosol indirect effect. The present work explores formulation sensitivities by constructing three alternate model configurations (S1, S2, S3). These alternate configurations exhibit only small differences in their present day climatology. Atmospheric Physics Chemistry and Climate 2011-07-01 http://www.gfdl.noaa.gov/index/news-app/story.32/title.the-gfdl-cm3-model Earlier generations of climate models at GFDL have specified cloud properties to be independent of atmospheric aerosol composition, despite fairly well-understood (at least for liquid clouds) dependence of cloud droplet number on aerosol composition and size distribution. Cloud drop number in turn exerts a major control on cloud radiation, notably albedo, and microphysics and macrophysics, notably cloud structure and lifetimes. Aerosol-cloud interactions are likely to be important in anthropogenic climate change. They have been difficult to incorporate in climate models because they occur at scales much smaller than resolved by climate models. CM3 parameterizes these smaller scales using probability distribution functions for motions smaller than those it explicitly resolves. Atmospheric Physics Chemistry and Climate 2011-07-01 http://www.gfdl.noaa.gov/index/news-app/story.28/title.raining-from-the-ground-up Though it is obvious that rainfall moistens the land surface, our scientific understanding of how land surface moisture may interact with the atmosphere to encourage or suppress subsequent rainfall is limited. Using data from the North American Regional Reanalysis (NARR, Mesinger et al., 2006), this study shows that the likelihood of afternoon rainfall in the eastern United States and Mexico is strongly linked to evaporation from the land surface earlier in the day. Climate Change Variability and Prediction 2011-06-05 http://www.gfdl.noaa.gov/index/news-app/story.31/title.downward-shortwave-surface-flux-in-the-gfdl-cm2-1-general-circulation-model The downward solar flux at the surface is an important component of the earth's climate system, being a major factor governing the surface temperature and hydrologic cycle. The availability of derived flux climatologies from both ground-based measurements and satellite-based estimates provide a reference for properly assessing general circulation model biases, not only in the surface irradiance, but in the atmospheric factors (aerosols, clouds, and water vapor) affecting it. Atmospheric Physics Chemistry and Climate 2011-04-22 http://www.gfdl.noaa.gov/index/news-app/story.34/title.north-american-isoprene-influence-on-intercontinental-ozone-pollution Changing land-use and climate may increase biogenic isoprene emissions, which could offset the benefits from North American air pollution controls for both domestic and European air quality (surface ozone). Both anthropogenic and biogenic emission changes are reflected in peroxy acetyl nitrate (PAN), which may serve as a more effective indicator of intercontinental emission changes than ozone itself. Atmospheric Physics Chemistry and Climate 2011-02-22 http://www.gfdl.noaa.gov/index/news-app/story.35/title.the-meteorological-nature-of-variable-soluble-iron-transport-and-deposition-within-the-north-atlantic-ocean-basin- Biological productivity in vast regions of the oceans is known to be limited by the supply of iron, an essential nutrient to marine organisms, impacting carbon export to the ocean floor. The atmospheric source of iron originates from desert mineral dust aerosols and is converted to a bio-available form of soluble iron during transport. Little is known of the magnitude and variability of soluble iron deposition (SFeD) and the character of its transport. We have used the GFDL Global Chemical Transport Model to examine the emission of mineral dust (~3.5% Fe) during Saharan desert dust storms; the chemical processing of iron to a soluble form during transport; and the subsequent dry surface deposition and precipitation scavenging deposition to the North Atlantic Ocean. Atmospheric Physics Chemistry and Climate 2011-02-01 http://www.gfdl.noaa.gov/index/news-app/story.39/title.sensitivity-of-the-noy-budget-over-the-united-states-to-anthropogenic-and-lightning-nox-in-summer- The study by Fang et al. [2010] examines the implications of new estimates of the anthropogenic and lightning nitrogen oxide (NOx) sources for the budget of oxidized nitrogen (NOy) over the United States in summer using a 3-D global chemical transport model (MOZART-4). NOy export and burden response less than linearly to either NOx emission changes due to the NOy partitioning change and the corresponding lifetime change. Lightning NOx contributes 24%−43% of the free tropospheric (FT) NOy export from the U.S. to the North Atlantic and 28%−34% to the NOy wet deposition over the United States. Atmospheric Physics Chemistry and Climate 2010-10-01 http://www.gfdl.noaa.gov/index/news-app/story.38/title.sensitivity-of-polar-ozone-to-sea-surface-temperatures-and-halogen-amounts- The results of the simulations of Austin and Wilson (2010) suggest the importance of including a coupled ocean on stratospheric processes as well as realistic bromine amounts, including the very short lived species. The figure shows the calculated area of the ozone hole (colored lines and triangles), together with observations (black triangles). With SSTs from the CM2 coupled ocean-atmosphere experiment, the simulated ozone hole (blue) tends to be slightly larger (by about 6%) than simulated with observed SSTs used as forcing (red curve and points). For the low Bromine simulation (green), which corresponds approximately to just the long lived bromine species, the ozone hole was smaller by about 10%. Atmospheric Physics Chemistry and Climate 2010-10-01 http://www.gfdl.noaa.gov/index/news-app/story.37/title.multi-variate-probability-density-functions-with-dynamics-for-cloud-droplet-activation-in-large-scale-models Multi-variate probability density functions with dynamics (MVD PDFs) have been incorporated into the single-column version of GFDL AM3 and extended to treat aerosol activation. MVD PDFs are unique in that they predict the joint distribution of temperature, water mass, and vertical velocity. The distribution of vertical velocity is then a natural link to aerosol activation. This paper presents the first results on the effects of aerosols and precipitation on cloud fraction and cloud liquid using the MVD PDFs and the first results on cloud droplet number concentrations obtained from the distributions of vertical velocity predicted by the MVD PDFs. Atmospheric Physics Chemistry and Climate 2010-10-01